AR-3a Possible Tweeter and Hello

[RoyC]

Here's the alternate tweeter mount. I must say, it is a much more elegant solution, but would require doing the rear-mount wiring scheme.

That looks very nice, John!

As Kent said, you can easily front-wire those if you wish. Later AR-3a's used back-wired tweeters, so either way would be "authentic" looking.

Roy

[Carlspeak]

Here's the alternate tweeter mount. I must say, it is a much more elegant solution, but would require doing the rear-mount wiring scheme.

Yeah, now you're talk'n! That's exactly what I suggested earlier. I'd love to run some acoustic response tests on both this and your earlier mounting configuration to compare measurable diffraction anomalies.

[JohnHeubel]

Yeah, now you're talk'n! That's exactly what I suggested earlier. I'd love to run some acoustic response tests on both this and your earlier mounting configuration to compare measurable diffraction anomalies.

Yeah, this does look a lot neater, and yes I also thought about drilling holes for the wires to come back up thru the faceplate. They could easily be sealed with caulk or coax-seal which I have. There's just something about the first mounting arrangement that seems to "fit" (to me at least) with the way the originals were cobbled together with electrical tape.

Carl, I was wondering about how measurable the diffraction effects of the first mount could be, given that the cabinet frames extend ~1" in front of the baffle. I could see measuring effects with the tweeter suspended in mid air or by itself on a flat baffle board, but not actually mounted in the AR cabinet. Wouldn't the frames virtually trump what diffraction could occur with the ridges on the Peerless with no faceplate?

Also, wouldn't the "great dispersion characteristics" of the originals have been diminished by the cabinet design too? I would think to take full advantage of the dispersion, the tweeter would have to be mounted on a baffle with no grill nor forward protruding edges, but I'll admit my knowledge of all the interactions is limited.

John

[Carlspeak]

You're right about the cabinet's edge predominating the diffraction issue. However, every little bit helps - especially close around the tweeter dome.

AR eventually developed what they called the 'improved' version with a shallower, narrower 'picture' frame cabinet edging as they learned about diffraction. The cabinet diffraction issues with the originals may have been one reason AR only published 2 pi response measurements of the individual AR3a drivers rather than a true, 'in speaker' system response.

[RoyC]

You're right about the cabinet's edge predominating the diffraction issue. However, every little bit helps - especially close around the tweeter dome.

AR eventually developed what they called the 'improved' version with a shallower, narrower 'picture' frame cabinet edging as they learned about diffraction. The cabinet diffraction issues with the originals may have been one reason AR only published 2 pi response measurements of the individual AR3a drivers rather than a true, 'in speaker' system response.

Actually the AR-3a Improved cabinet had been used for the European AR-3a since the early 70's. According to Tom Tyson it was a marketing decision to use a different cabinet in Europe, not a technical one. It was later "improved" around 1975 by the elimination of the dreaded pots, and the use of a modified crossover. The AR-3a Improved was introduced in Europe around the time the AR-11 was introduced in the US. The AR-11/10pi cabinet was probably the first "3a" to deliberately address some diffraction issues.

Personally I believe the dispersion attributes of the original tweeter are overstated, given the limitations of the cabinet, but agree with Carl about optimizing the faceplate.

If resale is a future consideration, the neater faceplate may be an advantage as well.

Roy

[JohnHeubel]

Actually the AR-3a Improved cabinet had been used for the European AR-3a since the early 70's. According to Tom Tyson it was a marketing decision to use a different cabinet in Europe, not a technical one. It was later "improved" around 1975 by the elimination of the dreaded pots, and the use of a modified crossover. The AR-3a Improved was introduced in Europe around the time the AR-11 was introduced in the US. The AR-11/10pi cabinet was probably the first "3a" to deliberately address some diffraction issues.

Personally I believe the dispersion attributes of the original tweeter are overstated, given the limitations of the cabinet, but agree with Carl about optimizing the faceplate.

If resale is a future consideration, the neater faceplate may be an advantage as well.

Roy

Thanks Roy and Carl for the extra historical information. And I agree that the neater faceplate could help with a future sale. More likely though, if the sound I eventually get out of them is what I've read it can be, I'd probably keep these in my system and sell the TSW-510s I have.

[Carlspeak]

Actually the AR-3a Improved cabinet had been used for the European AR-3a since the early 70's. According to Tom Tyson it was a marketing decision to use a different cabinet in Europe, not a technical one. It was later "improved" around 1975 by the elimination of the dreaded pots, and the use of a modified crossover. The AR-3a Improved was introduced in Europe around the time the AR-11 was introduced in the US. The AR-11/10pi cabinet was probably the first "3a" to deliberately address some diffraction issues......

Roy

Hi Roy. I know I read it somewhere here. It just took a while to find it.....

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=895&view=findpost&p=53176

[RoyC]

Hi Roy. I know I read it somewhere here. It just took a while to find it.....

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=895&view=findpost&p=53176

Hey Carl...Thanks. That one got past me.

I recall another conversation I had with Tom regarding AR's opinion that the unique style of cabinet molding of their overseas models (3a/2ax/5) was more to European tastes. If AR truly considered these cabinets a technical improvement, it is interesting that they were never sold here. I have been able to (subjectively) compare European 3a's with the American version on a number of occasions, and have never heard a difference. In fact, having experimented with so many tweeters in the 3a, I consider the dispersion issue to be near the bottom of my list of priorities.

Roy

[Carlspeak]

Hey Carl...Thanks. That one got past me.

I recall another conversation I had with Tom regarding AR's opinion that the unique style of cabinet molding of their overseas models (3a/2ax/5) was more to European tastes. If AR truly considered these cabinets a technical improvement, it is interesting that they were never sold here. I have been able to (subjectively) compare European 3a's with the American version on a number of occasions, and have never heard a difference. In fact, having experimented with so many tweeters in the 3a, I consider the dispersion issue to be near the bottom of my list of priorities.

Roy

I think the dispersion issue is not as important as the diffraction issue for those who typically listen in the 'sweet spot".

[dynaco_dan]

Hey Carl...Thanks. That one got past me.

I recall another conversation I had with Tom regarding AR's opinion that the unique style of cabinet molding of their overseas models (3a/2ax/5) was more to European tastes. If AR truly considered these cabinets a technical improvement, it is interesting that they were never sold here. I have been able to (subjectively) compare European 3a's with the American version on a number of occasions, and have never heard a difference. In fact, having experimented with so many tweeters in the 3a, I consider the dispersion issue to be near the bottom of my list of priorities.

Roy

Hi there

I remember someone told me, or, I read many years ago, that the British and Europeans, unlike North Americans, like a completely totaly finished speaker cabinet package.

Often with none or minimal grille cloth type coverings, as in no exposed driver front connections, more beautifull drivers, more cleanly mounted, after all, it is more of a piece of intimate

furniture to them.

We must remember that a lot of English, etc, have very small homes, requiring smaller stereo systems, especially the speakers.

Not so with the AR-3A's, with their less than beautiful drivers, putty oozing, electrical tape and exposed wiring on the front of the baffles.

Various rough finishes on the rear of the cabinets, putty smears and semi-splashed black paint on the front baffle boards and drivers.

I'm not complaining, I love my pair and all other AR speakers that I still own, but it held the cost down to us consumers.

Just as the British, etc also sold mostly the durable neoprene type surround woofers, rather than our poly foam versions.

I remember reading old English test reports and the comment usually was, the powerful amplifier was about 7 - 10 watts per channel, perhaps class A.

Finished total beauty, durablity and longevity is more to their taste.

[RoyC]

I think the dispersion issue is not as important as the diffraction issue for those who typically listen in the 'sweet spot".

Agreed...and being designed as "far field" speakers, AR did not consider "sweet spots" or "imaging" to be design goals.

Roy

[michiganpat]

I may be doing this comparison, as one of the originals had a good ohms reading. There's actually several tests I may run, all subjective as I don't have test equipment, but I may make the second mount today screwing the masonite ring to the tweeter as I was originally thinking. I'll then be able to compare the Peerless with "fins" to the original and "normal" faceplate version. It's the end of the school year though, andone of my daughters is graduating, so don't wait on my reports to purchase them since they could sell out.

Last year I bought some of the Jamo closeouts, 8' woofers and some 1 1/8" soft domes. I had some wood veneer cabinets with junk drivers in them. So I did some box volume calcs and decided to just use a simple 10uF cap xover like EPIs, running the woofers full range. Maybe I got lucky, but they sound pretty good. So, don't let the price fool you.

These were originally Zenith Model 66s, now they're custom.

granted, this a big tangent to the original subject, but over on the parts express board, Johnny Richards came up with a pretty decent 2-way using some jamo 8's running full range...here's the details:

http://techtalk.parts-express.com/showthread.php?t=225010

[genek]

I think the dispersion issue is not as important as the diffraction issue for those who typically listen in the 'sweet spot".

I have never noticed any of the described effects of diffraction with any speaker I've listened to, AR or other. From my POV, dispersion is the greater issue because it determines how much you can move around the room without the sound noticeably changing.

[Carlspeak]

Diffraction is a measurable acoustic artifact which manifests itself in a more jagged response curve. The response curve is smoother when diffraction is absent. One's ability to hear a jagged response varies from person to person.

As I pointed out earlier, dispersion is not a critical listening parameter for those who generally listen in the 'sweet spot' and don't tend to move around. I'll call that person the 'serious' listener for lack of a better description.

Then again, Soundminded might favor dispersion, even for the stationary listener. The kind of dispersion that creats a highly reflective sound field that envelopes the listener.

[RoyC]

Another big variable in all of this is the listening space. Old ads show AR speakers elevated and buried in bookshelves. AR was obviously not worrying about sweet spots or diffraction issues when they designed the models of the 3a era.

Roy

[genek]

Yes. Although dispersion matters more to me than diffraction, neither are terribly critical in a listening room made up almost entirely of "live" surfaces. I could probably create a reverberant field in here from a pair of Sonalerts.

[JohnHeubel]

So, we've sort-of come full circle in this discussion. The oft-touted uber-dispersion characteristics of the AR-3a dome tweeter, may or may not be as great as advertised perhaps because it's in a real world cabinet with protruding frames. Diffraction, while measureable in a test environment, may or may not be a "real world" concern when looking for replacement drivers for these old designs. They weren't then, as evidenced by the cabinet design, so why worry too much about it now.

I did a basic hookup today of the one cabinet with fully functional drivers, though I crimped and/or wire nutted the caps in place and didn't re-stuff the FG. Nice sound, and though I can tell the tweeter is playing, it's definitely subdued. I guess that's the laid-back AR sound I read about. I'm looking forward to getting the other cabinet put back together with the new tweeter and hearing what the difference is with NO extra coil before deciding whether to do that mod. Again, though the difference may be measurable, what's the real world ear test say...

[JKent]

Want dispersion? That's what these were designed for. And check the photo--they're sitting atop AR3a's

edit: See Vern's scans of the full review, Post #19, here:

http://www.classicsp...h=1

[Carlspeak]

Want dispersion? That's what these were designed for. And check the photo--they're sitting atop AR3a's

Sorry page 45 is missing. Anyone have the full review? (Stereo Review June 1971)

Here's a modern version of your Microstatic Array that can be purchased today. The spec's freq. range is 1 kHz to 16 kHz. That range goes too low for an AR3a application. I'd install or, replace whatever caps are in there with a 1 uF cap like the Microstatics have. The upper freq. range is just as good as the Microstatics.

Oh, and the price is quite reasonable.

http://www.mcmelectronics.com/product/555-10345

[genek]

Want dispersion? That's what these were designed for. And check the photo--they're sitting atop AR3a's

I've got several pairs of these. They don't seem to do very much on 3a's and 2ax's in the living room, but the effect on 6's in my office is pretty spectacular.

[Carlspeak]

The tweeters are piezo's which I overlooked initially. However, the 1 uF cap should work though to establish a much higher crossover point above the st'd 5 kHz on the 3a.

[dynaco_dan]

Want dispersion? That's what these were designed for. And check the photo--they're sitting atop AR3a's

Hi Kent

There is a ditto of this write-up that you altered later.

The full review of the Microstatic including my blundering copy has been posted in, I believe the, "others forum".

I started a Microstatic thread and it was later on when I re-posted the entire review again with the missing page.

Several members here have one or more pairs of the Microstatic Tweeter Array.

The most common comment I read was, there was an increase in dispersion and an extension of the highs when used with AR-5's or AR-3A's.

When the Microstatics were turned off, "where are the tweeters was a common comment".

When I wrote about my in home weekend demo of them and also included the JansZen 1-30 Tweeter Array.

My feeling was, "where are the tweeters," when I disconnected both pairs and heard only my AR-3A's playing.

Today I have another equal comparison, for those with hearing aids, pull them out of your ear or turn them off when listening to music

that you are familiar with.

Even the manufacturer said that not all speakers benefit from them and some benefit a lot with using them.

The only readable reference was them being used with AR-5 and AR-3A and a mention about using them with KLH.

I did read that the Microstatics sloped upwards after 12 khz and then began a gradual downward slope higher up.

Gene said he did not notice an appreciable difference ? with them with AR-5's or AR-3A's.

He did notice more of a enhancement ? with his AR-6's though.

My thoughts are the woofer and mid drivers least need for output, just dispersion, moreso.

With his AR-6's, his woofer, tweeter balance would be different.

Not wanting to start a war, just my observation and I am really tired now.

Just a thought for today.

[JohnHeubel]

Here's the tweeter using mount two. I did decide to bring the wires up thru the faceplate so I didn't have to do extra re-wiring in the cabinet, but I did decide to use slide terminals which do fit snugly onto the origninal solder teminals for easier removal. The pic shows the top of the assembled cabinet I was listening to earlier. Only one coat of Danish Oil, but it's very nice.

John

[soundminded]

Installing the faceplate on the Peerless tweeter defeats its advantage by limiting dispersion. It focuses the tweeter's sound forward, exactly the opposite of AR's design intent. Personally I'd install it without the faceplate.

One of the problems with the AR tweeter IMO besides its rolloff is its relative inefficiency compared to the midrange and especially the woofer in AR2ax. Not sure about AR3 but it wouldn't surprise me. You want the woofer to be the least efficient driver in the system so that you can pad down the other drivers to match up to it, not the other way around. One way to correct for this is bi and tri amplification but you have to be very careful to set gain to get precisely the settings you want and that they are easily repeatable. A detented volume control knob or a digital volume control with visual indication of the exact setting is helpful. Unless you have amplifier problems driving AR3/3a, a better option IMO is using a graphic equalizer. Used units are very cheap, very effective, and settings are easiliy repeatable.

Personally I'd avoid the piezo array. These tweeters not only often sound harsh, individually they have very narrow dispersion patterns. What you're likely to get is an irregular radiation pattern with HF hot spots on the axis of each one with audilbe falloff at the highest frequencies at angles between them. The deep horn virtually guarantees this effect.

[JohnHeubel]

Installing the faceplate on the Peerless tweeter defeats its advantage by limiting dispersion. It focuses the tweeter's sound forward, exactly the opposite of AR's design intent. Personally I'd install it without the faceplate.

One of the problems with the AR tweeter IMO besides its rolloff is its relative inefficiency compared to the midrange and especially the woofer in AR2ax. Not sure about AR3 but it wouldn't surprise me. You want the woofer to be the least efficient driver in the system so that you can pad down the other drivers to match up to it, not the other way around. One way to correct for this is bi and tri amplification but you have to be very careful to set gain to get precisely the settings you want and that they are easily repeatable. A detented volume control knob or a digital volume control with visual indication of the exact setting is helpful. Unless you have amplifier problems driving AR3/3a, a better option IMO is using a graphic equalizer. Used units are very cheap, very effective, and settings are easiliy repeatable.

Personally I'd avoid the piezo array. These tweeters not only often sound harsh, individually they have very narrow dispersion patterns. What you're likely to get is an irregular radiation pattern with HF hot spots on the axis of each one with audilbe falloff at the highest frequencies at angles between them. The deep horn virtually guarantees this effect.

I'm going to be trying it both ways with the two different mounting options. I agree about the original's inefficiency. ~4db lower than mid and woofer certainly has something to do with the "laid back" sound. I'm playing the Peerless now with no additional inductor and it seems to integrate fairly well. Again, these are not scientific tests...ears only, but with very familiar music. I curently have the high control set just a little toward decrease from "white dot." The better efficiency of the tweeter and extended frequency response compared to the original (yesterday's listening not A/B comparison) is more what I'm used to hearing. Not saying it's necessarily any better or worse, just a more familiar presence in things like harp and guitar string plucks, cymbals and crotales, etc.

As to the add-on tweeter arrays, that's a side discussion that arose out of the dispersion/diffraction discussion. No intention of adding them, nor bi/tri amping the speakers. For those that have the resources and audio is there only hobby, more power (pun intended) to them. That's just not my idea of fun...constantly tweaking and adjusting things. I may order .05mH coils for grins the next time I need to order anything, but I've got to get the other cabinet put together for "real" A/B testing of the tweeter mounts vs each other and the original dome. My gut feeling though, is that I'll have an original dome for sale in the next month or two.