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

[onplane]

Roy and I have been commenting on solutions to the pot problem in a couple of threads. So I thought I’d share with everyone what actually happens when you completely remove the pot from the tweeter xover circuit.

Before I get to the analysis, just want to say that all of Roy’s comments were 100% correct and the math below proves it. Nevertheless, Roy and I are probably still going to disagree on the actual impact on some parts of the changes.

Anyhow the analysis below assumes the raw tweeter total impedance (resistance and inductance) in the frequency range below is around 4 ohms. Next, this entire analysis assumes that we have the pot set to max prior to removing the pot AND that we are using the original tweeter. That is, we set the tweeter pot to its maximum position, which is AR’s recommended position for a flat response (along with a slight treble boost).

http://www.classicspeakerpages.net/dc/user_files/1666.jpg

Observations:

1. Removing the pot INCREASES the impedance for the tweeter network

2. Higher impedance means LESS current flows through the tweeter network @ same voltage

3. Nevertheless, MORE current flows through the tweeter and that is shown in the last column

4. On average 11% more current flows through the tweeter with the pot removed

5. Approx. 25% more power in the tweeter and 25% more SPL

6. Tweeter network increases in sensitivity for the same applied voltage

7. Reduction in xover frequency is really negligible (less than 2% difference between 4000 and 5000 hz)

Roy’s argument is that the improvement in sensitivity will cause the AR-3a’s to sound radically different than their originally intended design (Roy, please feel free to jump in and clarify your position).

My position is that AR back in 1968 said that we need the pots at max AND a slight treble boost to achieve a FLAT response. Most treble tone controls provide a maximum boost of 10 to 15db. 3db would equate to a 100% increase in SPL, so our achieved 25% is well within a “slight” increase.

My sense is you can follow the recommendation of Chuck McShane (in our library) of eliminating the tweeter pot with very little risk. Further, if that pot is in better shape than the mid pot, you can always swap or cannibalize.

Next issue is what happens if we remove the mid-range pot. That is a more complex situation, because the mid xover network is far more complex. Permit me to venture a few “guesses”:

1. With more components in series with the mid-range, pot elimination with have a LOWER resulting effect than pot elimination for the tweeter

2. There will be a mid network sensitivity increase – this I know, because I experienced it

3. My “guess” is in the range of 15% to 20% more SPL @ same voltage

The resulting increase will make the AR-3a’s “brighter” than originally intended and I admit that Roy is 100% correct. Unless you have a means to reduce the mid-range you will turn your East Coast speakers into West Coast speakers.

Regards,

Jerry

[dynaco_dan]

Hi Jerry;

Excellent report, thank you.

[Carlspeak]

.........."The resulting increase will make the AR-3a’s “brighter” than originally intended and I admit that Roy is 100% correct. Unless you have a means to reduce the mid-range you will turn your East Coast speakers into West Coast speakers".

Regards,

Jerry

L-Pad attenuation circuits (series-parallel resistors) are a common means of taming a mid or tweeter with higher than desired SPL (following surgical removal of an AR rheostat). Information on these circuits is readily available online. An advantage of this approach is the use of fixed resistors rather than a continuously variable mechanical device which may be subject to eventual failure. Good quality, non-inductive audio-grade resistors like Mills resistors offered by Parts Express will last practicly forever.

However, you must know how many dB you want to attenuate in order to design one of the simple circuits. A Radio Shack SPL meter is recommended for measuring your drivers to determine SPL differences.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[RoyC]

Hi Jerry,

Thanks for taking the time to provide those measurements.

>Roy’s argument is that the improvement in sensitivity will

>cause the AR-3a’s to sound radically different than their

>originally intended design (Roy, please feel free to jump in

>and clarify your position).

Relative to the tweeter pot, I never said anything about a "radical difference" when using the original tweeter.

You asked my opinion on by-passing the tweeter and mid pots by essentially fixing them at the maximum setting. I commented that you could probably get away with that approach using the original tweeter (no "radical" difference there), but not the midrange. I also commented that fixing both pots at maximum, and adjusting the midrange and tweeter in tandem, as you suggested, is not a good idea if maintaining the original sonic character of the system is important to the user. Also, for those who are using the modern replacement tweeter, which has more output and greater frequency response than the old, retaining the tweeter level control becomes more necessary.

>My position is that AR back in 1968 said that we need the pots

>at max AND a slight treble boost to achieve a FLAT response.

Regarding setting the level controls to maximum, the AR document you are referring to states the following:

"But the speaker system adjusted this way to play recordings would be unrealistic for anyone who knows what live music sounds like."

It goes on to say:

"Thus, the level control settings should be adjusted away from "normal" only to compensate for a listening environment that is relatively "dead" or "live" compared to "normal".

It should be noted in the quotes above that "normal" is NOT the maximum setting. It is where the AR engineers put the "white dot". Obviously those less-than-maximum pot positions were chosen to be the optimal settings for most listening environments.

Like it or not, even though we are all in agreement that they are a pain in the buns, the pots are part of the "voicing" of the old AR speaker systems. For those who prefer to maintain the character of these speakers, the level controls are necessary.

Most folks, including myself, prefer the old tweeter at or close to the maximum pot setting, which as we discussed, keeps the pot's 15 to 16 ohms in parallel with it. Whether that setting is due to modern tastes, better recordings or tired tweeters is certainly worthy of discussion. Completely removing the pot, however, is unacceptable to me.

>Most treble tone controls provide a maximum boost of 10 to

>15db.

Tone controls vary in turnover frequency, and slopes or contours. Different tone controls...different effects.

Roy

[charger3834]

I agree with Roy 100 percent, removing the tweeter pot brings its output up about 1 db over where it would be at the max position. In most listening enviornments that's a little "hot" relative to live music, which was always AR's target. I guess tastes come in to play as well.

I think that we can all agree that bypassing the midrange pot in any AR speaker system, is no way to achieve smooth power response. By the same reasoning, as a general rule, tweeters in 2-way systems should not be bypassed either.

[Carlspeak]

I get the impression with all this pot discussion that there is an unsaid assumption: our electronics treble and bass adjustments are ALWAYS set to level and are never fiddled with.

Most of us with stereo equipment have an additional tone control device AHEAD of the loudspeakers. It's either a preamp or receiver.

If some of you have the time or inclination (I don't), I'd be interested to know how a listening test would come out if one were to set the electronics to "level" and adjust the pots on the AR's to 'flat' response and then, bypass the pots either completely or with appropriately chosen fixed value resistors and use the electronics tone controls to achieve a similar 'flat' response.

Would there be a noticeable difference in the voicing character of the speakers???

Personally, I believe 95% of a speakers 'voice' is determined first by the mechanical makeup of the drivers, secondly - box material & stiffness, and thirdly - stuffing and driver/box interaction. That other 5% is crossover component selection. All this assumes, of course, the basic crossover design and point are held constant.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

>Regarding setting the level controls to maximum, the AR

>document you are referring to states the following:

>"But the speaker system adjusted this way to play

>recordings would be unrealistic for anyone who knows what live

>music sounds like."

>

>It goes on to say:

>"Thus, the level control settings should be adjusted away

>from "normal" only to compensate for a listening

>environment that is relatively "dead" or

>"live" compared to "normal".

>

>It should be noted in the quotes above that "normal"

>is NOT the maximum setting. It is where the AR engineers put

>the "white dot". Obviously those less-than-maximum

>pot positions were chosen to be the optimal settings for most

>listening environments.

Roy, I guess we are never going to agree on the pot settings. I have reproduced the AR memo below:

http://www.classicspeakerpages.net/dc/user_files/1672.jpg

While Roy’s quote is accurate, there is additional language in the AR memo that is very important. Specifically, AR made it clear that setting the pots to MAX (and let’s not forget that FLAT is still at MAX with a treble boost) would cause unrealistic playbacks BECAUSE of the recordings and playback systems of that time. Back in 1968 the primary source of all music was vinyl records. Vast majority of consumers at that time had record players with ceramic cartridges that were terribly deficient in reproducing high frequencies. Consequently, record companies, that wanted consumers to buy their product, had no choice but to emphasize high frequencies so that their product would sound decent on the majority of playback devices in the marketplace.

Moving forward 40 years where digital recording, storage and playback are the norm, that high frequency emphasis no longer exists or is necessary.

Those of you who continue to depress both the mid and high pots are intentionally making your speaker systems sound “dull” when playing back modern recordings. Now if you are listening to vinyl, that’s a different situation. As Carl pointed out, however, you have access to controls to compensate.

My sense is you should set both pots to max (and a slight treble boost) if the majority of your music source is modern digital recordings and playback.

I mean all through their history AR’s state goal was accuracy in sound reproduction. Why in heavens name would we cling to settings that were intended to compensate for errors in recordings that no longer exist? To do so only moves us further away from the end goal of accuracy in sound reproduction.

Carl’s points are well stated. Quality drivers and matching to cabinets creates the opportunity to reproduce accurate sound. Xovers can provide minimal assistance in achieving this goal. I believe even Carl will agree that if the xovers are totally “botched”, however, they can detract from the goal of accurate sound. In short, we absolutely need good xovers if we are to hear those high quality drivers. Poor xovers will act as a “sponge” and prevent energy from getting to the drivers in the correct amount at the correct frequency.

Regards,

Jerry

[soundminded]

Removing the pot increases impedence by removing the parallel resistor to the tweeter voice coil in it as one would expect. It also changes the crossover network characteristic increasing hf output by about 1 1/4 db at 10 khz, more at higher frequencies. This can be audible to critical listeners.

To those wanting to restore AR3a to its original performance, cleaning the pots, replacing them with functioning exact duplicates, or building a multiposition switch incorporating resistor pairs is the only real approach. On the other hand, to someone like me who wants the best possible sound, is not concerned with authenticity, and has no hesitation using a graphic equalizer, I would either eliminate the pot or use substitution resistor values at the point where AR indicated flat response. At the time AR3a was marketed, graphic equalizers at affordable cost were not available to the public, only to professional users at astronomical cost. Altec Acoustavoice a single channel 1/3 octave equalizer cost $900, a great deal of money in those days. At a trade show, an Altec salesman bragged to me he had just sold 56 pairs of Voice of the Theater loudspeakers to Columbia Records. (He also said VOT was 9 times as efficient as AR3a.) I'm sure he sold an equal number of Acousta voice equalizers to them as well. When properly used, an equalizer is one of the most powerful and valuable tools audio engineers and audiophiles have to flatten frequency response or adjust it for some other specific purpose.

[Carlspeak]

Again, lots of discussion on getting those mids and tweeters sounding 'rignt'. My impression from reading dozens of AR posts over the past few years is that it's the bass sound most enthusiasts love about AR speakers. I may be wrong here.

Given that premise (or, assumtion if you will), I wonder if anyone has replaced those old mids and tweeters with good quality, modern drivers (Vifa or Scanspeak) capable of faster response and reproduction of modern, full spectrum recordings? Furthermore, a well designed, fixed component passive crossover made up of very good quality caps, air core inductors and resistors would be a part of the overall upgrade.

I suspect, such a design would/could be capable of superior reproduction of modern recordings in terms and clarity and soundstaging while maintaining that original AR bass sound.

On the other hand, I suspect there are many vinyl/tube enthusiasts out there who would probably prefer keeping those 3a's, 2ax's and others as original as possible because the totality of reproduced music from that scenario would essentially duplicate what they believe they heard 30-40 years ago and want to continue hearing.

Conclusion: TO EACH HIS OWN

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[RoyC]

>Roy, I guess we are never going to agree on the pot settings.

Now there is a statement I agree with, Jerry:-)!!!

You have more faith in the modern recording industry than I do. Many recordings today are quite "hot" with artificial sounding high end. Also, listening environments vary as much today as they did way back when.

As mentioned in the other thread, and here by Soundminded, equalizers can be used for enhancement (without speaker surgery or complex amplifier arrangements).

Roy

[onplane]

>Given that premise (or, assumtion if you will), I wonder if

>anyone has replaced those old mids and tweeters with good

>quality, modern drivers (Vifa or Scanspeak) capable of faster

>response and reproduction of modern, full spectrum recordings?

>Furthermore, a well designed, fixed component passive

>crossover made up of very good quality caps, air core

>inductors and resistors would be a part of the overall

>upgrade.

>

>I suspect, such a design would/could be capable of superior

>reproduction of modern recordings in terms and clarity and

>soundstaging while maintaining that original AR bass sound.

>

>Carl

Carl, what to you mean by "drivers capable of faster response"? Just thinking out loud, it would seem to me that the speed of a driver will primarily impact it's upper frequency limit. Now if the AR drivers can cover their intended frequency range, would there really be any sonic difference, Carl?

On the real high frequencies I can well imagine modern tweeters that can produce higher frequencies than the original tweeter. This could be an advantage to many. For me it means little, because I can't hear much above 10K and I know this from Koss Pro 4ax headphones.

As for acoustic suspension base, I couldn't agree with you more. I love the deep, "tight" base. One thing I will share, Carl, is that the three of us that have attempted passive bi-amping all achieved even tighter base with bi-amping. Reason for this is somewhat a mystery, but I believe it has to do with simplier, better behaved impedance of the woofer by itself. This just makes the task for the amp powering the woofer that much easier. Further, any amp rail "jitter" is totally isolated from the other drivers.

Regards,

Jerry

[onplane]

>Removing the pot increases impedence by removing the parallel

>resistor to the tweeter voice coil in it as one would expect.

>It also changes the crossover network characteristic

>increasing hf output by about 1 1/4 db at 10 khz, more at

>higher frequencies. This can be audible to critical

>listeners.

>

Soundminded, your comments above are in agreement with my analysis with the very minor exception of "more at higher frequencies". According to my analysis it's really slightly more at LOWER frequencies.

That is, increasing the impedance causes a very slight reduction in the xover frequency. This reduction is soooo slight and coupled with the driver roll off, I doubt it's audible.

In total, soundminded, I believe your observation of a 1.25 db increase in tweeter output due to pot removal is right on!

Next, your comments on graphic equalizers are particularly interesting. I've notice, soundminded, that a number of folks, who like vintage equipment, have a total disdain for equalizers and I don’t understand this. Like you I strive for the best possible sound and equalizers clearly can play a very significant role in that quest. I have a 7 band on my TSW-610’s and I use it all of the time.

Soundminded, have you tried a bi-amping experiment? Reason I’m asking is that I’d value your feedback on the differences you hear.

Regards,

Jerry

[Carlspeak]

.........Carl, what to you mean by "drivers capable of faster response"? Just thinking out loud, it would seem to me that the speed of a driver will primarily impact it's upper frequency limit. Now if the AR drivers can cover their intended frequency range, would there really be any sonic difference, Carl?

On the real high frequencies I can well imagine modern tweeters that can produce higher frequencies than the original tweeter. This could be an advantage to many. For me it means little, because I can't hear much above 10K and I know this from Koss Pro 4ax headphones.

As for acoustic suspension base, I couldn't agree with you more. I love the deep, "tight" base. One thing I will share, Carl, is that the three of us that have attempted passive bi-amping all achieved even tighter base with bi-amping. Reason for this is somewhat a mystery, but I believe it has to do with simplier, better behaved impedance of the woofer by itself. This just makes the task for the amp powering the woofer that much easier. Further, any amp rail "jitter" is totally isolated from the other drivers.

Good job with the bi-amping!

The midrange cone and tweeter dome materials of modern drivers are much lighter than vintage units due to improvements in materials. Thus, being lighter they can oscillate as fast but with less distortion. It's true that both new and old drivers cover essentially the same frequency range with the exception of some boutique tweeters going well above 30 kHz. However, I strongly suspect that distortion measurements of new and old drivers of similar size and performance characterists whould show the newer ones with less distortion simply because the lighter wight can accomodate the oscillations more easily.

In conclusioin, both new and old cover the same frequencies. The difference is in the new driver's ability to sound cleaner.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

Thanks, Carl!!

The light is finally going on!

Yes, lighter is better and your comments about distortion, especially as we approach the drivers’ upper limit, sound very plausible, indeed!

Thanks again, Carl!

Regards,

Jerry

[soundminded]

As I reported, I have biamped an array of tweeters in my experiments with original Bose 901. I did this out of necessity since I didn't want the Bose equalizer signal to go through the amplifer feeding the tweeters. I also needed the added flexibility this affords. I've experimented considerably with different high frequency propagation concepts and equalization over the last 17 years. I've come to some interesting conclusions about it. I think there are more kinds of tweeter designs than designs for all other kinds of drivers combined. This fact expresses the importance of reproducing this region of the spectrum well and the frustration with what has been obtained to date. In experiments with AR9, I could not get that speaker system to reproduce musical instruments to my satisfaction no matter how much I tweaked my equalizer until I added more tweeters and aimed them indirectly by pointing them at the ceiling. I just kept adding them until the system sounded right. Then it took about 2 years of experimenting to equalize the system optimally. The results are qualitatively different. Each time something happened, an amplifier blew up and was replaced, a cd player conked out, the equalizer itself had a power transformer melt down, it took two more years to get back to where I had been. I can understand the frustration audiophiles have with equalizers, they take a great deal of patience and an ear familiar with live music. Well designed equalizers, and I think that's most of them, don't introduce audible distortion. Equalization is inherent in audio going back to the beginning of the LP and magnetic tape, maybe even before. Audiophiles who wouldn't dream of using one don't know or have forgotten that their records are equalized, every tape deck from the recording deck to the final mixdown deck was equalized, the recording engineer with his knob twiddling fingers used one, possibly drastically, and if the recording was made using professional Dolby Type A, that one's a lollapaloozer with four equalizers and non linear gain for each one. About the only recordngs which don't use equalization as a certainty are Digitally recorded compact discs.

So far adding all of these tweeters without bi-amplifying them has been satisfactory. I haven't blown up any amplifiers with them yet...well maybe one but that was a 22 year old Dynaco Stereo 120 and so it was probably doomed anyway. What really took it out was the DG recording of the Battle on the Ice in Prokofiev's Alexander Nevsky. Although the impedence can go below 2 ohms, the current draw at those frequencies is so low, it doesn't seem to upset any amplifiers I've used so far. I do admit that biamplifying them would be preferable but there is the factor of cost and practicality.

I'm restoring 3 Empire 9000Ms which will be used with an HT type receiver, Sony STR-G3 which does not like low impedence loads according to the instruction manual. I'm thinking of adding 2 tweeters in parallel with the main tweeter but I may use separate small outboard amplifiers built around the LM3886 chip using the main amplifier outputs for the input. Or I might just take my chances. BTW, a series LF blocking capacitor to prevent damage due to a LF transient and to cross them over is still a very good idea, even with an active crossover also being used IMO.

[prrtraincow]

This is quite an enlightening read for me. I have been an AR fan since my cousin bought a brand new pair of AR5s in the early 1970s. I eventually inherited those after he traded up to a pair of AR9s. We both still have those original speakers.

Even to this day, I am always impressed at how airy, clean, and simply beautiful these simple AR5s sound.

As for where those mid and tweeter controls "belong", all I can say is that even today, on almost any program source including modern rock CDs, my old vinyl Beatle records, jazz CDs, classical CDs or vinyl, or lately, Christmas CDs that are very heavy in small-combo acoustic instruments, I would never leave the controls cranked all the way up. They are just too "hot" for me at that level. I tend to put the tweeter about 3/4 up, and the mid about 1/2.

When you stop to consider all the variables you are trying to account for here: type of music, type of input medium, room acoustics, not to mention wildly varying personal preferences, I think it's plain silly to even worry about.

And I suspect, since AR had the good sense to put those controls on there in the first place, they ALSO thought it was plain silly to expect everybody to enjoy their speakers at some arbitrary "flat" setting (whatever the heck THAT is!)

[onplane]

>

>And I suspect, since AR had the good sense to put those

>controls on there in the first place, they ALSO thought it was

>plain silly to expect everybody to enjoy their speakers at

>some arbitrary "flat" setting (whatever the heck

>THAT is!)

>

Max, clearly when AR designed the AR-3a and the AR-5 the predominate source of music was vinyl records. Back then the recording engineers boosted treble to compensate for inferior playback systems.

AR was extremely wise to allow us years later (when vinyl no longer dominates) to re-balance our speakers. That is, today engineers no longer boost treble, so we have little need to cut back the treble and mid-range.

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 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 pots inside the speakers. Further, re-balancing for different sources (CD’s, vinyl, tapes, etc.) is extremely easy.

With today’s very low costs for modest power amps, bi-amping is within the reach of everyone. Max, I want to be clear here. In order to get “good sound” out of these vintage AR’s we need a decent size 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 ….

Regards,

Jerry

[Guest matty g]

Hello All- Not to beat this subject to death, but I have found that the troublesome wirewound controls on these otherwise phenominal loudspeakers are best left in place. I have had satisfying results with the 3A and 2AX systems by shorting the "super tweeter" pot terminals 1 and 3 (the original tweeters are rather dark) and shorting the mid pot terminals with a ceramic 10 ohm resistor. This seems to give the approximate color that I remember them having. I hope this is electrically kosher. I'm driving the 2AX's with a Mac 1700, so over powering the drivers shouldn't be a problem. Does this seem like a good idea? Matt

[onplane]

>Hello All- Not to beat this subject to death, but I have

>found that the troublesome wirewound controls on these

>otherwise phenominal loudspeakers are best left in place. I

>have had satisfying results with the 3A and 2AX systems by

>shorting the "super tweeter" pot terminals 1 and 3

>(the original tweeters are rather dark) and shorting the mid

>pot terminals with a ceramic 10 ohm resistor. This seems to

>give the approximate color that I remember them having. I hope

>this is electrically kosher. I'm driving the 2AX's with a Mac

>1700, so over powering the drivers shouldn't be a problem.

>Does this seem like a good idea? Matt

Matt, when you say you "short" the tweeter pot terminals, do you just put a jumper from the pot wiper terminal to the terminal at the top of the pot?

If so, I really don't like this idea very much. The wiper is still in the circuit and depending upon where you set it will adjust the impedance seen by your amp. Worst case is if you turn the tweeter to max decrease, you have completely shorted the pot AND the speaker leaving only the cap in the circuit.

On high frequencies you'll have a resulting impedance that's way, way too low.

Matt, the risk is just too high with this. Instead, you would be far, far better off removing the wire that goes to the pot wiper and solder it directly to the top of the pot. Now the wiper does NOTHING. The 16 ohm pot wire resistor is still in the parallel with the tweeter. This is the same as setting a "good" pot to max increase.

Alternatively, you can remove the pot entirely from the circuit, by removing both wires (wiper and top of the pot) and soldering together. This is what I did. The result is slightly less high freqency current goes through the entire speaker, but more current and more sound comes out of the tweeter.

Hope this helps...

Jerry

[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.

[frankmarsi]

E' tu Brutus?.....

[frankmarsi]

>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

[Carlspeak]

>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.

I guess I'm the devil in disguise.

Carl

Carl's Custom Loudspeakers

[frankmarsi]

Don't come down on yourself like that Carl. I dig where you're coming from about how you may see things concerning these speakers,I've been there for over 35 years myself.How do you say? "It's all about the music". Material things that they are often distract men and give pleasure.

Frank Marsi

[onplane]

>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.

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