Impact of tweeter pot removal on AR-3a's

[soundminded]

"So, AR fans are faced with the sac-religious task of changing the classic designs into modern designs, more efficient drivers, capacitors, scrapping resistance devices etc."

I think one of the most remarkable things about classic AR speakers in general and speakers like AR3a in particular is that forty years after they were first offered, in a world where electronics progress has been astounding in that time frame, there are still a significant number of people like many of us who have them and use them not as museum pieces but for their original purpose of accurately reproducing recorded music. This is mind boggling to me. Can anyone think of anything else manufactured 40 years ago that they'd still prefer to use that way even if it isn't exactly in its original form for the purpose it was intended for? A television set? A car? Even a toaster? I think if the people who were there at the time could have known their efforts would be so highly regarded after four decades, they'd have been thrilled with the prospect and wouldn't have cared one whit that some minor chanages had to be made to restore them or to further improve them in light of progress elsewhere. What item can you think of that is being manufactured today which will likely be similarly regarded in the year 2046?

IMO, one strategy to get the most out of this speaker is to replace the potentiometers with resistors which will give the flattest on axis frequency response and then install the speakers with the midrange and tweeters at ear level so that the front is flush with a wall. This means cutting an opening in a wall and placing the speaker on a shelf. The next best alternative is a similar installation in a "built in" wall unit. Then equalize the speaker for most accurate sound. Keep in mind that inexpenisve high powered amplifiers and graphic equalizers for consumer use didn't exist in 1967. Because of AR3a's wide dispersion tweeter (still possibly the widest dispersion of all single tweeters), It offers the best compromise between the two critical performance criteria of flattest on axis FR and flattest total radiated power response of any single tweeter speaker system and this is one possible practical way to exploit it to its fullest potential.

[Carlspeak]

Do I sense a minor groundswell of separatism from the purists?

In spite of the poor response to my upgrade inquiry, I'm strongly leaning toward developing the tweet/mid upgrade kit. And, I must confess I'm a bit intrigued by the challange. All that's needed now is a pair of 3a's or 2a's to work on. I don't own any myself but plan to do design/development work in my 'spare' time once I get a pair. So, it may take awhile before something is available. The asking price will be substantially less than Layne Audio's $665 kit.

Oh, and by the way, each kit will come with a customer satisfaction money back guarantee that will negate any 'leap of faith'.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

>I think one of the most remarkable things about classic AR

>speakers in general and speakers like AR3a in particular is

>that forty years after they were first offered, in a world

>where electronics progress has been astounding in that time

>frame, there are still a significant number of people like

>many of us who have them and use them not as museum pieces but

>for their original purpose of accurately reproducing recorded

>music. This is mind boggling to me. Can anyone think of

>anything else manufactured 40 years ago that they'd still

>prefer to use that way even if it isn't exactly in its

>original form for the purpose it was intended for?

Excellent comments, Soundminded! The AR-3a is clearly a remarkable speaker and like many here, I use mine every day (am listening as I type).

I think it was Carl, who mentioned on a number of occasions that he felt that the drivers are the distinguishing feature that give the AR-3a's their unique character.

Looking at them one-by-one, the woofer was designed to minimize low frequency distortion and to "marry" with the enclosure in such a way that really low frequencies could be accurately reproduced.

The domed mid-range is a very unique and exceptionally clear driver. It complements the woofer, but is NOT required to handle the very high frequencies as in a two way system. So the rather narrow frequency range it's left to handle, it does exceptionally well.

That leaves the domed tweeter, which is probably the weakest in modern terms, but still a very high quality driver. Even 40 years later it's dispersion characteristics are admirable!

I say, "To hell with the electronics (caps, coils, pots, etc). Do anything and everything to keep those unique drivers moving!"

Regards,

Jerry

[Carlspeak]

In a 12/5 post Jerry wrote:

"Efficiency is NOT impacted significantly by removing the pots. Efficiency of AR’s is far more influenced by the acoustic suspension woofer. That’s where the real power is consumed."

I beg to differ. Yes the woofer does consume more power. However, that is because it takes significantly more energy to move the larger mass of the cone, coil, spider and surround. A woofer can have an efficiency of 85 dB/watt and a tweeter easily can go above 92 dB/watt. That's a significant difference that must be dealt with if a speaker is to sound half way decent - either with a trim pot or a series/parallel L-pad circuit just ahead of the tweeter.

I'm not saying the AR3a woofer/tweeter difference is that great - just citing an example. However, my experience has shown tweeters are typically more efficient than woofers or mids.

Here again (as I step up on my worn out soap box)I don't know what the original AR3a tweeter and woofers efficiencies were. Perhaps one of the AR gurus could help here.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[soundminded]

In designing a speaker system which will be powered by a single amplifier, it's important to have midrange and tweeter drivers which are more sensitive (efficient) than woofers. This is because it is necessary to match the driver levels in the design and while adding resistors in series with tweeters and midrange speakers to drop their level is not a problem, adding a resistor in series with a woofer to drop its relative level were it too efficient can cause FR problems by reducing electrical damping significantly. Also, this is the frequency range where most power is usually delivered and a series resistor would be a significant waste of power.

[Guest Russ]

Running two amps is an interesting method to boost the highs Jerry, but wouldn't it be better to put in vifa or scanspeak tweeters which have a greater range and output, in addition to putting in new capacitors?

I like the tight bass on the AR-2X's I have with their 10" woofer but the mids and highs of these speakers is not very good, it sounds like you are listening to them through several inches of foam rubber, the mids and highs are quite muffled, some of the information seems to be almost missing.

I have the speakers hooked into a multi media setup inlcuding a Yamaha 70 watts RMS per side reciever with spacial expander and a Sony stereo TV, the speakers in this regular Sony ($500 TV) are not Sony's top of the line but they reproduce the highs of a female singer and symbol/percussion sounds much brighter than the old AR's, they compliment the AR's making them sound more like a modern speaker. This is pretty sad, that a standard TV is doing a better job on the mids/highs than the AR's.

I also have two Sansui 5 way speakers running in the system on channel B, these have 16" Woofers which in combination with the AR's give a pretty full bass sound as any good Quadraphonic setup would, I had to put a volume control in the speaker wires to restrict the current going to the Sansui's as they are much more effient speakers (open port), I have them set at only one or two on the volume knob in order to balance the sound between AR and Sansui, which shows how much power these AR's need. These old Sansui's are also not very bright - despite an 8" mid-range, horn and two tweeters, perhaps they need new caps too. Their bass can blow your socks off though, even if it is muddy at times. If I can brighten up this system it will be pretty good. Some day I may upgrade to something like this (a variation of the AR-9 perhaps)...

http://stereophile.com/floorloudspeakers/706revel/

or if I win the lottery something like these for $30,000...

http://stereophile.com/floorloudspeakers/1106canton/

Russ

>Efficiency is NOT impacted significantly by removing the pots.

> Efficiency of AR’s is far more influenced by the acoustic

>suspension woofer. That’s where the real power is consumed.

>

>Removing the pots changes the balance of low to high frequency

>sound produced by the speakers. When the speakers were

>designed and built the major source of music at that time was

>vinyl records. Vast majority of the sound reproduction

>systems at that time were so poor that sound engineers

>artificially boosted the high frequencies.

>

>With the advent of digital recording and playback, this

>boosting is no longer necessary. We are extremely fortunate

>that AR had the foresight to allow us to “re-balance” our

>system.

>

>Unfortunately, there are two problems with AR's solution:

>

>1. the pots deteriorate over time and cause degradation of the

>resulting sound

>2. some folks still listen on occasion to vinyl and need the

>ability to attenuate treble and mid-range to compensate for

>that artificial “boost”

>

>From my perspective the ideal solution is to horizontal bi-amp

>and ELIMINATE the pots. This effectively moves the function

>of the pots back to the volume control on the amp that drives

>the mid-range and tweeter. Maintaining that “line level” pot

>is much, much easier than maintaining the power dissipating

>pots inside the speakers. Further, re-balancing for different

>sources (CD’s, vinyl, tapes, etc.) is now trivial. It’s just

>a matter of tweaking the volume control on the amp driving the

>mids/tweeters.

>

>With today’s very low costs for modest power amps, bi-amping

>is within the reach of everyone. Russ, I want to be clear

>here. In order to get “good sound” out of these vintage AR’s

>we need a fairly powerful amp. That “decent amp” can still be

>put to good use driving just the woofers. What’s needed, in

>addition, is a modest power amp to drive the mids/tweeters.

>By “modest power” I’m talking about 25 to 35 wpc channel.

>Anything bigger would just be a waste.

>

>Hope this helps …

>

>Jerry

>

[Guest Russ]

I would love to hear an AR-3A (good enough for Miles Davis) someday as well as the AR-9, I agree that it is impressive that AR's continue to be restored and upgraded, testimony to their quality. Most speaker boxes do not have the thickness of veneer that the old Ar's had, so even when heavily damaged (warped and stained) by people watering plants on top of them (as mine were) you can sand them down and re-oil them to look new again.

Russ

>"So, AR fans are faced with the sac-religious task of

>changing the classic designs into modern designs, more

>efficient drivers, capacitors, scrapping resistance devices

>etc."

>

>I think one of the most remarkable things about classic AR

>speakers in general and speakers like AR3a in particular is

>that forty years after they were first offered, in a world

>where electronics progress has been astounding in that time

>frame, there are still a significant number of people like

>many of us who have them and use them not as museum pieces but

>for their original purpose of accurately reproducing recorded

>music. This is mind boggling to me. Can anyone think of

>anything else manufactured 40 years ago that they'd still

>prefer to use that way even if it isn't exactly in its

>original form for the purpose it was intended for? A

>television set? A car? Even a toaster? I think if the people

>who were there at the time could have known their efforts

>would be so highly regarded after four decades, they'd have

>been thrilled with the prospect and wouldn't have cared one

>whit that some minor chanages had to be made to restore them

>or to further improve them in light of progress elsewhere.

>What item can you think of that is being manufactured today

>which will likely be similarly regarded in the year 2046?

>

>IMO, one strategy to get the most out of this speaker is to

>replace the potentiometers with resistors which will give the

>flattest on axis frequency response and then install the

>speakers with the midrange and tweeters at ear level so that

>the front is flush with a wall. This means cutting an opening

>in a wall and placing the speaker on a shelf. The next best

>alternative is a similar installation in a "built

>in" wall unit. Then equalize the speaker for most

>accurate sound. Keep in mind that inexpenisve high powered

>amplifiers and graphic equalizers for consumer use didn't

>exist in 1967. Because of AR3a's wide dispersion tweeter

>(still possibly the widest dispersion of all single tweeters),

>It offers the best compromise between the two critical

>performance criteria of flattest on axis FR and flattest total

>radiated power response of any single tweeter speaker system

>and this is one possible practical way to exploit it to its

>fullest potential.

[Guest matty g]

Hi Jerry- I see your point regarding tthe wiper terminal ont the pot and I agree that your method is electrically a much better idea. You caught me juat in the nick of time as I am currently re-edging and refinishing a pair of 1972 3A's for my living room. I'll take your advice and change 'em. I guess that in the past I never had any problems because the wipers and resistors were so beat that making contact wasn't likely to happen. Truthfully, though, the construction of the pots is such that removing, disassembling and cleaning them is quite easy. They are very robust controls and if properly cleaned and "ox-gaurded" should be relativley trouble free. I have had pretty good luck going that route, too. Thanks for the good advice- and long live that New England soud! Matt

[Guest Russ]

>>I read somewhere else on this site that one of the

>original

>>AR engineers advised people to scrap the pots because

>they

>>would get an increase in signal going to the tweeters or

>mids,

>>this would lead to a more efficient speaker.

>>

>>So, AR fans are faced with the sac-religious task of

>changing

>>the classic designs into modern designs, more efficient

>>drivers, capacitors, scrapping resistance devices etc.

>>

>>Is is better to have a classic chevy or a customized one?

>Your

>>ears are probably more important than maintaining

>tradition. I

>>am guilty of scrapping the original stained vanilla cloth

>in

>>favour of black on my AR-2X's, they look very sharp in

>black.

>>

>>Are the pots the next to go or will it be the caps...

>They

>>do sound good as they are but curiosity may push me to

>>experiment. The walnut boxes are pretty though.

>

>

>

>

>12-5-06

>

>E' tu Brutus?.....

>

>Frank Marsi 12-5-06

Hey Frank, I'm not killing anything here,au contrair...I am breathing new life into a legend....let the good times roll!

Caesar btw was murdered after a finacial crisis in which he was sticking up for the little guy at the expense of the corrupt senators/land owners...history repeats.

Russ

[onplane]

>Hi Jerry- I see your point regarding tthe wiper terminal ont

>the pot and I agree that your method is electrically a much

>better idea. You caught me juat in the nick of time as I am

>currently re-edging and refinishing a pair of 1972 3A's for my

>living room. I'll take your advice and change 'em. I guess

>that in the past I never had any problems because the wipers

>and resistors were so beat that making contact wasn't likely

>to happen. Truthfully, though, the construction of the pots is

>such that removing, disassembling and cleaning them is quite

>easy. They are very robust controls and if properly cleaned

>and "ox-gaurded" should be relativley trouble free.

>I have had pretty good luck going that route, too. Thanks for

>the good advice- and long live that New England soud! Matt

Matt,

The way I see it, the pots are a losing proposition. Yes, you can clean them. No question about it, but ... but they’ll immediately begin to corrode again.

Further, that corrosion changes the balance of the resulting sound. As the pots corrode you slowly lose mid and high frequencies. Back in 1968, AR said that to achieve a “flat” response we need BOTH pots set to max increase AND a slight treble boost. The best way to do this is to cut the wires going to the wipers and solder them directly to the tops of the pot.

Now, you have a speak system with a fairly flat frequency response. If you want to de-emphasize the highs, just reduce the treble control.

Regards,

Jerry

[onplane]

>Running two amps is an interesting method to boost the highs

>Jerry, but wouldn't it be better to put in vifa or scanspeak

>tweeters which have a greater range and output, in addition to

>putting in new capacitors?

>

>I like the tight bass on the AR-2X's I have with their

>10" woofer but the mids and highs of these speakers is

>not very good, it sounds like you are listening to them

>through several inches of foam rubber, the mids and highs are

>quite muffled, some of the information seems to be almost

>missing.

>

>I have the speakers hooked into a multi media setup inlcuding

>a Yamaha 70 watts RMS per side reciever with spacial expander

>and a Sony stereo TV, the speakers in this regular Sony ($500

>TV) are not Sony's top of the line but they reproduce the

>highs of a female singer and symbol/percussion sounds much

>brighter than the old AR's, they compliment the AR's making

>them sound more like a modern speaker. This is pretty sad,

>that a standard TV is doing a better job on the mids/highs

>than the AR's.

>

>I also have two Sansui 5 way speakers running in the system on

>channel B, these have 16" Woofers which in combination

>with the AR's give a pretty full bass sound as any good

>Quadraphonic setup would, I had to put a volume control in the

>speaker wires to restrict the current going to the Sansui's as

>they are much more effient speakers (open port), I have them

>set at only one or two on the volume knob in order to balance

>the sound between AR and Sansui, which shows how much power

>these AR's need.

Russ,

I started bi-amping strictly as an experiment. I did not set out to boost high frequencies. What I got as a result of that bi-amping experiment is:

1. better transient response

2. far better stereo imaging

3. bass that is better defined (tighter)

4. clearer/cleaner high frequencies

5. amps running much cooler than before

Now, why all of this happens is NOT entirely clear, but much can be explained by:

http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

The change to the pots came much later. What happened is I got upset when I once again lost all mid-range in the left speaker. For years now I would have to move the pot back and forth a few times and the mid-range would re-appear. Since my bi-amp was so successful, I decided that I no longer wanted the pots in the circuits at all. Thus, they have been removed and NOW my mid-range is stable as can be!

Now, I’d like to switch to your situation, because I like nothing about it. I mean this with no disrespect, but I think you’ve broken all of the rules.

First off, the AR’s consume vast amounts of power. Next, those multi media amps are not all that good. Now, I don’t know anything about your Yamaha, but many of the HT amps are rated at 1000 hz and are NOT full range (they don’t have to be full range because they strip the low frequencies and send to the sub-woofer). These are simply not the kind of amp that I’d want running AR’s. (The Yamaha may be the exception, but I’d really be surprised.)

On top of this, you have the AR’s in parallel with the Sansui speakers. The load on that little HT amp must be enormous. It’s no surprise to me that the mid-range and tweeter are starved for current by the AR woofer PLUS the 16 inch Sansui woofer.

So where to start …. I think the first thing to do is get the AR’s on their own amp. That is, stop sharing an amp with the Sansui’s. Next, perform the “Jerry Mod” on the pots. That is, cut the wires to the wipers and solder to the top of the pots. This will give you AR’s with a fairly flat frequency response.

Then tell us how the AR’s sound.

I think you’ll be pleasantly surprised.

Now, if you really want to push them, bi-amping is the way, but that means you’d need two more amps!!

Hope this helps …

Regards,

Jerry

[tysontom]

>

>I started bi-amping strictly as an experiment. I did not set

>out to boost high frequencies. What I got as a result of that

>bi-amping experiment is:

>

>1. better transient response

>2. far better stereo imaging

>3. bass that is better defined (tighter)

>4. clearer/cleaner high frequencies

>5. amps running much cooler than before

>

>Now, why all of this happens is NOT entirely clear, but much

>can be explained by:

>

Jerry,

I’m not going to jump back in and criticize your bi-amping configuration for your AR-3as, but a few of your comments above need clarification and correction.

“Better transient response.”

You do not get “better transient response” with bi-amping, unless there was some problem to begin with, which there is not. The transient response of the AR 12-inch woofer is such that there is no appreciable “ringing” at any frequency; the frequency response would otherwise show deviation in its operating range (poor transient response also relates to irregular frequency response). The AR-3a woofer has less than +/- 1-1/2 dB variation across its operating range, and no one has ever demonstrated problems of this nature in times past. Tone burst photos of the woofer’s response always show less than a half-cycle of overshoot, about as good as it can get for a woofer. The woofer’s damping, primarily at resonance, is determined mechanically, acoustically and magnetically; it doesn’t care whether you have an amplifier driving it only or the entire speaker system, so long as the damping factor is above 1. Most amplifiers are in the hundreds. So you may somehow sensed “better transient response” with your bi-amped setup, but it is not actually real with that speaker.

“Bass that is better defined (tighter).”

Here, too, the same applies. “Tighter” does not specifically describe any acoustical event. If anything, “tighter” might imply over-damping, an undesirable condition. Such a sound is not like the sound of the original instrument because certain elements of the waveform are attenuated when compared to the original sound. The AR-3a is not over-damped with a Q of 1.0.

--Tom Tyson

[ar_pro]

No matter how much Jerry *wishes* this concoction of amplifiers, EQ's & cables to be true bi-amplification, it ain't.

And this stuff is insidious- it's already worked its way into a number of threads, and usually goes unchallenged.

Jerry - have you even checked the schematics of your dissimilar amplifiers and equalizer to determine if absolute phase has been affected? I'll bet not.

Hurray for "clearer/cleaner high frequencies", though!

[soundminded]

Since this has become a general thread about tweeters, I figured I'd stick my two cents in. I noticed about 20 years ago, the general trend to brighter home speakers. I wasn't thrilled with the tonal balance of my AR9s so I began to experiment. I looked at what other people were doing that seemed to work. I was especially impressed by the Snell AIIIi so I decided to try what had been done with this and some other high end speakers and that was to add another tweeter...firing away from me. I've experimented ever since with many speakers and a lot of different ideas and have come to some interesting conclusions. If you take a speaker system that's playing fairly loudly, even one that sounds bright and disconnect everything except the tweeter, it's surprising how little of the overall sound it contributes. But that sound is critical. Although the human ear may not be most sensitive in the top two octaves, the brain apparantly makes a great deal of use of the information it gleans from hearing high frequency sounds. It's critical to determination of direction (a survival tool) and there may be other factors as well. In addition to the relative level and FR contouring of HF sounds, I've discovered that the relative angles this sound arrives at your ear at are also critical, that is whether all of the HF sound comes from a single narrowly focused direction or from a wide number of directions. IMO, the beaming of HF sound from a single point source for reproducing the sound of musical instruments is the worst arrangement possible. Unfortunately, that is the arrangement designed into over 99% of the speaker systems on the market today and over 99% of all speaker systems ever marketed. This is what I think gives recordings a characteristic shrill sound which can be especially noticable on cds where it's a common complaint. Why is this so? I can only guess but a few ideas are that this is not the way even a single musical instrument launches sound let alone a group of them and that when it is launched this way, its interaction with the room boundaries is entirely different (far less) than for middle and low frequency tones which are much more omnidirectionally launched. I've experimented with all types of direct and indirect arrays to try to spread out the sound to come up with the most accurate sounding arrangement. I keep coming back to the conclusion that in the average to slightly bright rooms I have, the optimal launch ratio is about 1 part direct to 12 parts indirect. this ratio can be adjusted by the use of L-pads or resistors so it is not necessary to have 13 tweeters per channel. In this regard, I've found the cost of the tweeters to be of secondary importance, the Audax 3/8" polycarbonate tweeter and its clones which sell for about $5 to $10 each work very well. (arrays also cut down on dynamic compression, each tweeter operating at only a small fraction of its capacity.) I've also found that because the room boundaries usually selectively absorb high frequencies to an increasingly greater degree as frequency rises, further improvement is obtained by countouring the direct firing tweeter relative to the indirect firing tweeters. So for example, in one array, I put a 1 mfd capacitor across the direct tweeter voice coil but none across the indirect tweeters, then slightly boost the treble to compensate. For AR9, using its own tweeter as the direct tweeter, I didn't have to alter it at all. I've also found that because of inherent variations of tonal balance from one recording to another even in cds, it is very advantageous to be able to adjust either or both the high frequency coutour and relative loudness to trim the treble response and it is better to not have to do it at or near the speaker but from a distance. Another discovery I made is that when the treble is not shrill there is a natural tendency to adjust it to be too bright as it is very pleasing to listen to. It also makes it possible to increase the low bass output considerably if the speaker is capable of it without making it sound bottom heavy. I tried an array where the entire treble was radiated indirectly and got an interesting phenomenon. Every time there was a sibilant sound such as from somone singing, the late arrival of all of the HF energy created a peculiar sound similar to what people using a phaser to create sound effects get, a kind of pfssst sound each time so some directly radiated HF sound is necessary. I've experimented on AR9, McIntosh ML-1C, Bose 901, KLH Model 6, Empire 9000M, and AR2a and been very pleased with the results every time. I still have a pair of AR2ax and Advent/2 to experiment with. If anyone has had any experience experimenting in a similar way, I'd be eager to hear about it.

[dynaco_dan]

Hi there;

A very interesting write-up, thank you.

[Guest matty g]

Jerry-

Took your advice about disconnecting the tweeter and the midrange driver from the "B" terminals and connecting them directly to #1 terminal. I did not remove the pots as they are part of a circuit that I don't want to alter.

I did, however, attenuate the mid with a 10 ohm 10 watt ceramic resistor. The system is in a somewhat "live" room and, after test trials with several resistor values, I found 10 to be just right.

The midrange network is quite impressive on the 3A as opposed to the '67 and earlier 3. I felt it best to leave it as originally designed.

By the way, I put these speakers into service this morning and I just can't stop listening to them. They are replacing the 2AX's that I've used every day for 25+ years and they are a major step up! I have never had a pair of speakers that sounded perfect with the amplifier controls set flat before. I must agree that these speakers should be kept as "stock" as possible. The new surrounds didn't seem to change the dynamics of the woofers at all,(my greatest fear),and should one of the "super tweeters" or dome mids go dead every attempt at obtaining a stock replacement should be made. A Vifa or Morel with a spacer ring would be plan b, but I would leave the higher order crossover intact.

Cheers

Matt

[onplane]

Congratulations, Matt!!

I listen to my Ar-3a's every day and I'm still impressed with clarity of the highs and tight, deeeeeep bass.

Regards,

Jerry

[onplane]

>No matter how much Jerry *wishes* this concoction of

>amplifiers, EQ's & cables to be true bi-amplification, it

>ain't.

>

>And this stuff is insidious- it's already worked its way into

>a number of threads, and usually goes unchallenged.

>Jerry - have you even checked the schematics of your

>dissimilar amplifiers and equalizer to determine if absolute

>phase has been affected? I'll bet not.

>Hurray for "clearer/cleaner high frequencies",

>though!

>

>

ar_pro, phase is a very complex subject. In our library there is a very interesting article by Robert Berkovitz that you should read.

Next, I know exactly the phase relationship of my amps. I measured with my dual trace scope. Further, I have the ability to change the phase relationship by 180 degrees with the flip of a switch. This allows me to do a very, very quick A/B comparison. The results of this have already been posted - see:

http://audiokarma.org/forums/showthread.ph...highlight=phase

Next, there are a number of people who have experienced satisfactory results with passive bi-amping of AR speakers ... including AR!! Again, you might try reading the notes from AR in our library.

Regards,

Jerry

[onplane]

>

>I’m not going to jump back in and criticize your bi-amping

>configuration for your AR-3as, but a few of your comments

>above need clarification and correction.

>

>“Better transient response.”

>

>You do not get “better transient response” with bi-amping,

>unless there was some problem to begin with, which there is

>not. The transient response of the AR 12-inch woofer is such

>that there is no appreciable “ringing” at any frequency; the

>frequency response would otherwise show deviation in its

>operating range (poor transient response also relates to

>irregular frequency response). The AR-3a woofer has less than

>+/- 1-1/2 dB variation across its operating range, and no one

>has ever demonstrated problems of this nature in times past.

>Tone burst photos of the woofer’s response always show less

>than a half-cycle of overshoot, about as good as it can get

>for a woofer. The woofer’s damping, primarily at resonance,

>is determined mechanically, acoustically and magnetically; it

>doesn’t care whether you have an amplifier driving it only or

>the entire speaker system, so long as the damping factor is

>above 1. Most amplifiers are in the hundreds. So you may

>somehow sensed “better transient response” with your bi-amped

>setup, but it is not actually real with that speaker.

>

>“Bass that is better defined (tighter).”

>

>Here, too, the same applies. “Tighter” does not specifically

>describe any acoustical event. If anything, “tighter” might

>imply over-damping, an undesirable condition. Such a sound is

>not like the sound of the original instrument because certain

>elements of the waveform are attenuated when compared to the

>original sound. The AR-3a is not over-damped with a Q of 1.0.

>

>

>--Tom Tyson

Hi, Tom!

I agree with you, if we dwell too much in this "pot" thread about bi-amping, we should probably start a new thread.

First off, when I say "better transient response", that is far, far more related to the mid driver and tweeter. What I think is happening is that amps WITHOUT the current drain of the woofer are just unencumbered and can “roll with the punches better”.

Tom, I say this because I watched rail voltages on 4 amps (NAD, HeathKit, HK, and Kenwood) while driving the AR-3a’s. What I saw in every case is the low frequency bass line in music would cause a short term instability (“jitter”) in the rail voltages. That is, the heavy current drain would cause a “droop” in the rail voltages. Now some amps recovered better than others (HK dual power was the fastest).

Nevertheless, during this “droop” a lot was going on in the high frequencies and it’s my contention that an amp NOT experiencing this droop can handle high frequency “bursts” better. Further, Tom, that we can hear the difference.

Now, as to tighter and better defined bass.

Tom, in all honesty I can hear the difference, but I am NOT sure what’s going on. An amp powering the woofer by itself sees a totally different impedance map than an amp powering a complete AR-3a. In this thread, you can see the impedance maps both ways:

http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

Clearly an amp driving just the woofer ALONE sees a better “behaved” impedance AND over the frequency range of the woofer it will send more current to the woofer than a single amp driving a complete 3a at the same voltage/volume. That current difference WILL undoubtedly result in a difference frequency response … it simply has to. Further the additional current is just in the range of 100Hz to 450Hz. The very deep bass is unchanged.

So, Tom, there can be no more disputes. It’s clearly different! The measurements don’t lie.

Now, what can be disputed is whether it sounds better or … whether it sounds worse. The way I describe the difference is the bass sounds “tighter”. Another individual who tired this exact same experiment (on Usenet) also described the difference as “tighter bass”. (Now, I admit it’s entirely possible that he was influenced by my language.) Nevertheless, I have a TSW-610 to compare against and there is more “punch” in the bass in my 3a’s now than there was prior to bi-amping. In short, I like it better, but ... you may NOT. You may feel it's "unnatural".

Tom, if we want to continue this discussion, we really ought to start a new thread or resurrect the thread on impedances.

Regards,

Jerry

[onplane]

>I've experimented ever since

>with many speakers and a lot of different ideas and have come

>to some interesting conclusions. If you take a speaker system

>that's playing fairly loudly, even one that sounds bright and

>disconnect everything except the tweeter, it's surprising how

>little of the overall sound it contributes. But that sound is

>critical.

Soundminded, that is a great observation. Allow me to embellish. If we shut down the woofer, the sound coming from the mid and tweeter is amazingly small! Then if we shut down the mid and tweeter leaving just the woofer, the sound is still LOUD, but it's awful! It makes little sense to us. You can't even make out what females are singing.

>Although the human ear may not be most sensitive in

>the top two octaves, the brain apparantly makes a great deal

>of use of the information it gleans from hearing high

>frequency sounds. It's critical to determination of direction

>(a survival tool) and there may be other factors as well. In

>addition to the relative level and FR contouring of HF sounds,

>I've discovered that the relative angles this sound arrives at

>your ear at are also critical, that is whether all of the HF

>sound comes from a single narrowly focused direction or from a

>wide number of directions. IMO, the beaming of HF sound from

>a single point source for reproducing the sound of musical

>instruments is the worst arrangement possible. Unfortunately,

>that is the arrangement designed into over 99% of the speaker

>systems on the market today and over 99% of all speaker

>systems ever marketed.

Yeaaaaah, that might be the intended design, a narrowly focused beam, but it's NOT what actually happens. High frequency signals bounce all over hell. What actually arrives at our ears is tons of reflected signals regardless of how the speakers are designed.

>This is what I think gives recordings

>a characteristic shrill sound which can be especially

>noticable on cds where it's a common complaint. Why is this

>so? I can only guess but a few ideas are that this is not the

>way even a single musical instrument launches sound let alone

>a group of them and that when it is launched this way, its

>interaction with the room boundaries is entirely different

>(far less) than for middle and low frequency tones which are

>much more omnidirectionally launched.

Well, when it comes to instruments, I think much depends upon the kind of instrument. Electronic instruments (keyboards, guitars, etc) produce sound via loudspeakers. Even for most singers the sound that actually gets to our ears has been amplified and comes out of a loudspeaker.

>I've experimented with

>all types of direct and indirect arrays to try to spread out

>the sound to come up with the most accurate sounding

>arrangement. I keep coming back to the conclusion that in the

>average to slightly bright rooms I have, the optimal launch

>ratio is about 1 part direct to 12 parts indirect. this ratio

>can be adjusted by the use of L-pads or resistors so it is not

>necessary to have 13 tweeters per channel. In this regard,

>I've found the cost of the tweeters to be of secondary

>importance, the Audax 3/8" polycarbonate tweeter and its

>clones which sell for about $5 to $10 each work very well.

>(arrays also cut down on dynamic compression, each tweeter

>operating at only a small fraction of its capacity.) I've

>also found that because the room boundaries usually

>selectively absorb high frequencies to an increasingly greater

>degree as frequency rises, further improvement is obtained by

>countouring the direct firing tweeter relative to the indirect

>firing tweeters. So for example, in one array, I put a 1 mfd

>capacitor across the direct tweeter voice coil but none across

>the indirect tweeters, then slightly boost the treble to

>compensate.

Why in heavens name would you put a cap across the direct firing tweeter? This will prevent that tweeter from reproducing the high frequencies. If you put that cap across the other tweeters as well, you'd get NO high frequencies. Why not just put a resistor in series if you want to attenuate the direct firing tweeter's output?

>For AR9, using its own tweeter as the direct

>tweeter, I didn't have to alter it at all. I've also found

>that because of inherent variations of tonal balance from one

>recording to another even in cds, it is very advantageous to

>be able to adjust either or both the high frequency coutour

>and relative loudness to trim the treble response and it is

>better to not have to do it at or near the speaker but from a

>distance. Another discovery I made is that when the treble is

>not shrill there is a natural tendency to adjust it to be too

>bright as it is very pleasing to listen to. It also makes it

>possible to increase the low bass output considerably if the

>speaker is capable of it without making it sound bottom heavy.

> I tried an array where the entire treble was radiated

>indirectly and got an interesting phenomenon. Every time

>there was a sibilant sound such as from somone singing, the

>late arrival of all of the HF energy created a peculiar sound

>similar to what people using a phaser to create sound effects

>get, a kind of pfssst sound each time so some directly

>radiated HF sound is necessary. I've experimented on AR9,

>McIntosh ML-1C, Bose 901, KLH Model 6, Empire 9000M, and AR2a

>and been very pleased with the results every time. I still

>have a pair of AR2ax and Advent/2 to experiment with. If

>anyone has had any experience experimenting in a similar way,

>I'd be eager to hear about it.

Soundminded, I think your experiments are neat! One thing that is certain is that there are a large number of variables in reproducing sound. That makes this a fun hobby because there is simply an UNLIMITED number of things to try.

Experimenting and sharing results is what I like almost as much as listening to the music. Fortunately, I can do both at the same time!

Regards,

Jerry

[Guest Russ]

>>Running two amps is an interesting method to boost the

>highs

>>Jerry, but wouldn't it be better to put in vifa or

>scanspeak

>>tweeters which have a greater range and output, in

>addition to

>>putting in new capacitors?

>>

>>I like the tight bass on the AR-2X's I have with their

>>10" woofer but the mids and highs of these speakers

>is

>>not very good, it sounds like you are listening to them

>>through several inches of foam rubber, the mids and highs

>are

>>quite muffled, some of the information seems to be almost

>>missing.

>>

>>I have the speakers hooked into a multi media setup

>inlcuding

>>a Yamaha 70 watts RMS per side reciever with spacial

>expander

>>and a Sony stereo TV, the speakers in this regular Sony

>($500

>>TV) are not Sony's top of the line but they reproduce the

>>highs of a female singer and symbol/percussion sounds

>much

>>brighter than the old AR's, they compliment the AR's

>making

>>them sound more like a modern speaker. This is pretty

>sad,

>>that a standard TV is doing a better job on the

>mids/highs

>>than the AR's.

>>

>>I also have two Sansui 5 way speakers running in the

>system on

>>channel B, these have 16" Woofers which in

>combination

>>with the AR's give a pretty full bass sound as any good

>>Quadraphonic setup would, I had to put a volume control in

>the

>>speaker wires to restrict the current going to the

>Sansui's as

>>they are much more effient speakers (open port), I have

>them

>>set at only one or two on the volume knob in order to

>balance

>>the sound between AR and Sansui, which shows how much

>power

>>these AR's need.

>

>

>Russ,

>

>I started bi-amping strictly as an experiment. I did not set

>out to boost high frequencies. What I got as a result of that

>bi-amping experiment is:

>

>1. better transient response

>2. far better stereo imaging

>3. bass that is better defined (tighter)

>4. clearer/cleaner high frequencies

>5. amps running much cooler than before

>

>Now, why all of this happens is NOT entirely clear, but much

>can be explained by:

>

>http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

>

>

>The change to the pots came much later. What happened is I

>got upset when I once again lost all mid-range in the left

>speaker. For years now I would have to move the pot back and

>forth a few times and the mid-range would re-appear. Since

>my bi-amp was so successful, I decided that I no longer wanted

>the pots in the circuits at all. Thus, they have been removed

>and NOW my mid-range is stable as can be!

>

>Now, I’d like to switch to your situation, because I like

>nothing about it. I mean this with no disrespect, but I think

>you’ve broken all of the rules.

>

>First off, the AR’s consume vast amounts of power. Next,

>those multi media amps are not all that good. Now, I don’t

>know anything about your Yamaha, but many of the HT amps are

>rated at 1000 hz and are NOT full range (they don’t have to be

>full range because they strip the low frequencies and send to

>the sub-woofer). These are simply not the kind of amp that

>I’d want running AR’s. (The Yamaha may be the exception, but

>I’d really be surprised.)

>

>On top of this, you have the AR’s in parallel with the Sansui

>speakers. The load on that little HT amp must be enormous.

>It’s no surprise to me that the mid-range and tweeter are

>starved for current by the AR woofer PLUS the 16 inch Sansui

>woofer.

>

>So where to start …. I think the first thing to do is get the

>AR’s on their own amp. That is, stop sharing an amp with the

>Sansui’s. Next, perform the “Jerry Mod” on the pots. That

>is, cut the wires to the wipers and solder to the top of the

>pots. This will give you AR’s with a fairly flat frequency

>response.

>

>Then tell us how the AR’s sound.

>

>I think you’ll be pleasantly surprised.

>

>Now, if you really want to push them, bi-amping is the way,

>but that means you’d need two more amps!!

>

>Hope this helps …

>

>Regards,

>Jerry

>

>

Jerry, thanks for your input,

First off my Yamaha is not a multi-media reciever, it is a 1983 Stero reciever (R700) which was originally a 50 watts per side but after I dropped it while trying to get it's digital synthysizer tuner to lock on ( a chronic problem on some distant stations when getting a feed from cable) it died and I had Yamaha fix it but they could only get the more powerful 70 watts per side chips for it.(my stereo salesman that I bought it from recommended I pour beer into it next time it misbehaved at the time, but it has been good for over a decade now. Anyways it is a good reciever with very low total harmonic distortion, it has served me well for a quarter century and even running the AR2X's by themselves on channel A they still sound exactly the same as when the Sansui's are hooked up to B with the AR's, so this would argue against the theory that they are starved for power, the Yamaha has lots of power, even when listening to them loud you would not want to go above about 2.5 or 3 on the volume knob.

snip - "perform the “Jerry Mod” on the pots. That

>is, cut the wires to the wipers and solder to the top of the

>pots."

Q:What are the "wipers"?

No doubt I have broken many rules but that does not stop me from enjoying many fine pieces of music from Keith Jarrett, Chic Corea to Bach to the Beatles etc.

The Sansui's were Japan's top speaker back in the late 70's I have been told, Sansui is now gone as a company. What I like about them is the cloth surrounds which remain in good shape after 30 years unlike the foams on AR's which I replaced myself. The Ar's have a much bigger sound than my old EPI 100's.

I realize that this system I have put together is not a high end stereo but it's a pretty good mid range system and perhaps after doing some further tweaking I can pull those mids and highs out better.

Russ

[dynaco_dan]

Hi Russ;

Please write another topic about your AR-2X experiences please.

I know that they are a bigger AR-4X but I would like to see what your thoughts are regarding them.

Which version are yours, earliest with cloth surround, alum frame and 3 1/2" tweeters with fiberglass?

I just recently received a pair with an adapter from a steel 10" woofer to the larger hole pattern, with the 2 1/2" AR-4X tweeter.

[soundminded]

"Yeaaaaah, that might be the intended design, a narrowly focused beam, but it's NOT what actually happens. High frequency signals bounce all over hell. What actually arrives at our ears is tons of reflected signals regardless of how the speakers are designed."

I have to disagree. Most speakers use a 1" dome tweeter which typically starts falling off rapidly above around 12Khz off axis. By 30 to 45 degrees off axis, most are off arond 8 to 10 db at 15 khz with respect to its on axis repsonse. To appreciate just what this polar response difference in HF and mid and low F means, listen to a bookshelf speaker outside and walk around it. Behind it you will hear it fairly loudly except you will hear NO hf sounds whatsoever. As move around it and you get closer and closer to being on axis, notice how much clearer it sounds. The 3/4" AR tweeter was one of the widest dispersion tweeters ever offered but AR engineers decided it still wasn't good enough as evidenced by the design of LST. Were dispersion not a consideration in LST, only power handling, it wouldn't have been necessary to place the tweeters on angled panels. Roy Alison saw the same thing and incorporated it into his designs. I just took it a few steps (a lot of steps) further. In those days, economics was a serious consideration. Adding three tweeters and one midrange to AR3a in a slightly larger box more than doubled its price. Today, items like dome tweeters and graphic equalizers once unavailable to home experimenters are to be had at near giveaway prices.

"Well, when it comes to instruments, I think much depends upon the kind of instrument. Electronic instruments (keyboards, guitars, etc) produce sound via loudspeakers. Even for most singers the sound that actually gets to our ears has been amplified and comes out of a loudspeaker."

You are right. The reproduction of electronically amplified musical instruments is different. But aside from whether or not that is usually the kind of music I'd want to hear, what does the term accuracy mean for reproducing them? If I go to a live symphony concert and what I am hearing is coming from a loudspeaker, even in part, why wouldn't I be just as well off staying home listening to my own speakers? Interestingly, the human voice is one of the few musical instruments to beam most of its hf directly at the listener. However, reproducing it with a speaker system with much wider dispersion of the types I use doesn't seem to degrade its sound at all.

"Why in heavens name would you put a cap across the direct firing tweeter? This will prevent that tweeter from reproducing the high frequencies. If you put that cap across the other tweeters as well, you'd get NO high frequencies. Why not just put a resistor in series if you want to attenuate the direct firing tweeter's output?"

By putting a capacitor in parallel with the direct firing tweeter, its high end is rolled off compared to the indirect firing tweeters, then by boosting the treble control, it is flat again and the indirect tweeters have a rising treble output. Since their energy is selectively absorbed by the walls to a greater degree as frequency increases, the reflected hf sound is also flat. That's how you get both flat direct and reflected sound with an array of tweeters powered by one amplifier. The alternative is to power the direct tweeter and indirect tweeters from different amplifiers, the direct one being flat and the indirect one being appropriately equalized. That's the design for my ultimate speaker system. As for putting a resistor in series with the front firing tweeter, I do that too. It's important to realize that the degree of hf equalization difference depends on the room acoustics, the speaker must be able to be adapted to the room it's used in. In my basement which still has concrete walls, reflection of HF is so efficient, enhancing AR2a with both direct and reflecting tweeters didn't require any difference in FR betweem them.

I think the ears/brain combination works much like a direction finding dipole antenna. A slight movement of the head allows the brain to relate the increase in loudness in one ear and decrease in loudness of the other to the degree of head movement and make critical judgements not only about direction but about the size of a sound source. I think this is completely subconscious. It's also the reason binaural sound (2 channel recordings with mikes where eardrums would be and played back through headphones) dosesn't work, the sound doesn't remain stationary with head movements. In this way, with all of the hf sound coming from a single direction with only one tweeter, the brain judges it as a small concentrated source, hence it is shrill. Also, although acousticians don't ordinarily measure reverberation above 10 khz, IMO HF reverberation is very critical to judging the acoustics of venue. In my experiments with synthetic reverberation, filtering hf components of the reverberant sound compltely substantially lessens its effect. Typically, this component decays about twice as fast as mid frequencies at a live performance in a concert hall but in simulation, it needs to be about 70% to 80% to be subjectively similar. I have no explanation as to why. Speakers with improved hf sound (flatter, more extended, wider dispersion) are sometimes described as sounding more "airy." Perhaps this at least in part is the reason.

[ar_pro]

"Again, you might try reading the notes

from AR in our library."

An amusing response from a fellow who believes that rotating bass & treble controls to their minimum settings in some way replicates an electronic crossover!

By all means, have fun with your collection of old integrated amplifiers and cables - and please continue to report upon your astonishing discoveries of growling bass and faster transients - it's a hoot!

ar_pro (earnestly typed whilst enjoying a pair of bi-amplified AR-9's)

[onplane]

> "Again, you might try reading the notes

> from AR in our library."

>

>An amusing response from a fellow who believes that rotating

>bass & treble controls to their minimum settings in some

>way replicates an electronic crossover!

I never said anything like this. Since I have no electronic xover, the xovers are still in the speakers and still doing their job as I have confirmed. Rotating the tone controls can aid in gaining significant headroom. Once again this has been documented with lots of discussion:

http://audiokarma.org/forums/showthread.ph...light=bi-amping

Perhaps if you contributed to discussions rather than simply challenging, your ideas would achieve better acceptance.

ar-pro, please share with us the results of your experiements and your data.

Regards,

Jerry