Replacement drivers for AR-2a

[owlsplace]

I'm sure I'm not the only person to notice these AR-2a's over on the auction site. Orange Country Speakers in So. Cal. gave them a workover. The seller says he has over $1,000 invested and apparently is happy to recover half of that.

He says the mids and highs sound better than his pair of 3a's.

Mids and tweeters were replaced -- no mention of any crossover changes or the drivers used.

Serial numbers are 7717 and 7723.

[JKent]

Would be interesting to know what drivers were used. The angled drivers are actually tweeters (from the 2-way AR-2) and a supertweeter was added. I would imagine the "expensive high-end tweeters and midrange drivers" would present crossover issues, as you suggest. The new drivers sure do look nice but I wonder how suitable they really are as replacements.

I have a pair of 2a's that unfortunately I'm not using now. Thing about them is, to get the best sound they should be placed on a bookshelf, on their sides, so you get the benefit of the horizontal dispersion of those angled drivers.

Very nice speakers (the original 2a). They used to be overshadowed by the 2ax and of course the 3a but it looks like the 2a is commanding some high prices on the auction site.

-Kent

[RoyC]

The tweeter is the last AB Tech 3/4 inch replacement tweeter, which alone requires a crossover change to be in the ballpark of the original 1"+ dome tweeter. The addition of the mids takes things into the realm of redesigning the speaker...and I believe I recognize the new mids as common general replacement drivers. He is asking alot, even at half of the $1000 he allegedly has into them.

Anyone contemplating selling or purchasing extensivley modified AR's should realize they do not carry a "collector's" premium. Even if they sound OK, they are no longer AR-2a's, and most likely do not sound like 2a's. There are many other AR (and non-AR) "classic" speakers worth considering within and below this seller's price range.

Roy

[Carlspeak]

Here's an interesting thread for those AR2a owners with bad mids. The inexpensive phenolic ring tweeter can sub as a midrange in the 2a application. Read on....

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6705&hl=midrange

[Steve F]

Thoughts/questions that I've always had about the AR-2 and 2a:

Where did that idea for angled 5" drivers come from? Angled drivers in 1957 was hardly a common approach. Was that Villchur's idea? The whole notion of broad dispersion was not widely held or even well-understood in those days. I'd love to read a genuine AR design paper.

Why did they fire "across" each other, rather than "outwards?" There will be tremendous interaction/interference in their outputs by firing "across" (think of two flashlights). In contrast, firing "outwards," each driver's output is unaffected and unfettered.

If the 5" drivers' plastic housing was oriented at 45 degrees rather than being parallel to the horizontal dimension, then the AR-2/2a's 5" radiation would have been identical (although admittedly not optimal) whether the cabinet was used H or V.

Still, I find the entire "angled 5" driver" situation to be strange, not well thought out and somewhat arbitrary. It was not until 1971's LST (a veritable lifetime away from 1957 in that era's speaker development history) that AR again did angled drivers. And except for the MST--which was just trying to capitalize on the LST's cachet at a lower price point--AR never did angled drivers again on a "regular" speaker.

A very strange bird in my view.

Steve F.

[owlsplace]

Thoughts/questions that I've always had about the AR-2 and 2a:

Where did that idea for angled 5" drivers come from? Angled drivers in 1957 was hardly a common approach. Was that Villchur's idea? The whole notion of broad dispersion was not widely held or even well-understood in those days. I'd love to read a genuine AR design paper.

Why did they fire "across" each other, rather than "outwards?" There will be tremendous interaction/interference in their outputs by firing "across" (think of two flashlights). In contrast, firing "outwards," each driver's output is unaffected and unfettered.

If the 5" drivers' plastic housing was oriented at 45 degrees rather than being parallel to the horizontal dimension, then the AR-2/2a's 5" radiation would have been identical (although admittedly not optimal) whether the cabinet was used H or V.

Still, I find the entire "angled 5" driver" situation to be strange, not well thought out and somewhat arbitrary. It was not until 1971's LST (a veritable lifetime away from 1957 in that era's speaker development history) that AR again did angled drivers. And except for the MST--which was just trying to capitalize on the LST's cachet at a lower price point--AR never did angled drivers again on a "regular" speaker....

Steve F,

Perhaps a bit of Eddie Villchur's genius. I can see him visualizing the sound field pattern generated by the cross-firing drivers cancelling some of the on-axis response effectively equalizing the broad field response

Someone should have made him sit down and do a biography.

Roger

[lakecat]

I always find these kind of sales odd. You pour way excessive money into a project to make a customized system for yourself. Key word....yourself. Now you sell it?.........why?

[Carlspeak]

.................

Someone should have made him sit down and do a biography.

Roger

Someone did. Scroll down the long list at the link below. E.V. discusses the design of the AR1, dome tweeter, the AR turntable among other developments of his.

http://www.aes.org/historical/oral/#32

There's a veritable treasure trove of video interviews in the Audio Engineering.org website.

[owlsplace]

I always find these kind of sales odd. You pour way excessive money into a project to make a customized system for yourself. Key word....yourself. Now you sell it?.........why?

Following his dream probably which few of us have the cash flow to do in similar fashion anyway...

Someone did. Scroll down the long list at the link below. E.V. discusses the design of the AR1, dome tweeter, the AR turntable among other developments of his.

http://www.aes.org/historical/oral/#32

There's a veritable treasure trove of video interviews in the Audio Engineering.org website.

They are shorts... will watch

[tysontom]

Thoughts/questions that I've always had about the AR-2 and 2a:

Where did that idea for angled 5" drivers come from? Angled drivers in 1957 was hardly a common approach. Was that Villchur's idea? The whole notion of broad dispersion was not widely held or even well-understood in those days. I'd love to read a genuine AR design paper.

Why did they fire "across" each other, rather than "outwards?" There will be tremendous interaction/interference in their outputs by firing "across" (think of two flashlights). In contrast, firing "outwards," each driver's output is unaffected and unfettered.

If the 5" drivers' plastic housing was oriented at 45 degrees rather than being parallel to the horizontal dimension, then the AR-2/2a's 5" radiation would have been identical (although admittedly not optimal) whether the cabinet was used H or V.

Still, I find the entire "angled 5" driver" situation to be strange, not well thought out and somewhat arbitrary. It was not until 1971's LST (a veritable lifetime away from 1957 in that era's speaker development history) that AR again did angled drivers. And except for the MST--which was just trying to capitalize on the LST's cachet at a lower price point--AR never did angled drivers again on a "regular" speaker.

A very strange bird in my view.

Steve F.

I can answer this post.

"Where did that idea for angled 5" drivers come from?"

The angled-5-inch driver idea came specifically from Henry Kloss with his work on the AR-2 before leaving AR in February 1957. Prior to AR, Kloss fabricated and sold the Baruch-Lange "High-Fidelity Speaker," a speaker system designed by profs. J. J. Baruch and H.C. Lang of MIT. This speaker used four Carbonneau 5-inch general-purpose speakers (exactly the same as used in the AR-2), and the frequency response of this system was "reasonably" flat when mounted in the special enclosure. Therefore, the response characteristics of this speaker were known. To improve smoothness in the AR-2, Kloss added fiberglass under the 5-inch cones to help dampen the inexpensive speaker cones.

"Angled drivers in 1957 was hardly a common approach. Was that Villchur's idea? The whole notion of broad dispersion was not widely held or even well-understood in those days."

On the contrary, Ed Villchur knew of and wrote about the need for dispersion as early as 1954, and he understood that most of what you hear in a typical home listening room is primarily the reverberant sound field, not direct sound. He had Kloss figure out a way to get better dispersion (in the horizontal plan) with the Carbonneau 5-inch drivers, and the inward-angled arrangement was used. Since the AR-2 was essentially a "bookshelf" loudspeaker, it was most likely to be mounted horizontally, thus the arrangement of the tweeters and the unfinished bottom panel of AR-2s and AR-2as with any finish. With the angled tweeters, there was most definitely an issue of interference effects, but these are heard only in the first-arrival, near field, not in the far field where the speaker's primary acoustic output was predominant.

"Why did they fire "across" each other, rather than "outwards?" There will be tremendous interaction/interference in their outputs by firing "across" (think of two flashlights). In contrast, firing "outwards," each driver's output is unaffected and unfettered."

The answer to this is apparent if you look at the design of these speakers. If you mounted the tweeters to fire away from each other, the drivers would have to be either recessed in the cabinet (this would cause real problems) or protrude outside of the cabinet front grill molding area. Villchur knew the inward-firing tweeters would produce reasonably smooth, if somewhat band-limited, high frequency with reasonable dispersion into the fairly high treble range.

Again, the interaction between the two drivers did not cause an audible artifact in the acoustic-power response, the part we hear. The reason for this is that the lobing, interference effects as measured, will move up and down the frequency band when moving the measuring microphone just a small distance from the speakers or at a slightly different angle. In the final analysis, these peaks and dips will cancel each other in the reverberant field, and this has been clearly demonstrated in the past. Villchur clearly understood this, and it was described Leo Beranek's book Acoustics, Frederick Hunt's book Electroacoustics and Olson's book Elements of Acoustical Engineering. If you listen up close to an AR-2 or AR-2a—within 2-3 feet from the speakers—you will definitely hear the interference effects, but once you get back, you don't hear it. As you know, the AR-2 went on to be top-rated in Consumer Reports and enjoyed very high critical acclaim throughout its history.

"Still, I find the entire "angled 5" driver" situation to be strange, not well thought out and somewhat arbitrary. It was not until 1971's LST (a veritable lifetime away from 1957 in that era's speaker development history) that AR again did angled drivers. And except for the MST--which was just trying to capitalize on the LST's cachet at a lower price point--AR never did angled drivers again on a "regular" speaker. A very strange bird in my view."

Hindsight now is certainly 20-20 as we look back nearly 60 years, but when the AR-2 was introduced, the "angled 5" drivers" worked very well and the speaker was known to have a very smooth, uncolored "personality." It might now seem to be a "strange bird," but when it was designed, it was advanced and ahead of its time for a speaker in this price range. And yes, the LST used the "angled-panel" approach, and it (too) was heavily criticized by many pundits for issues with first-arrival interference effects and so forth, but it was considered to be one of the best loudspeakers ever designed when it came to its perceived accuracy and its ruler-flat acoustic power response, rarely equaled by any standard speaker before or since in this respect.

—Tom Tyson

[Steve F]

Interesting that this was Kloss' idea, not Villchur's. I wouldn't have thought that.

Without specifically agreeing or disagreeing, I will simply observe that this is the exact area in which there is so much controversy:

.....he understood that most of what you hear in a typical home listening room is primarily the reverberant sound field, not direct sound.....With the angled tweeters, there was most definitely an issue of interference effects, but these are heard only in the first-arrival, near field, not in the far field where the speaker's primary acoustic output was predominant.

Proponents of 'first-arrival' say that regardless of far-field response, the very first thing you hear--far field or near--is the so-called anechoic response, and therefore it sets the tonal stage for what follows a few scent milliseconds later. So to them, yes, interference and lobbing do matter, no matter where you sit, up close or far away. They will be quick to point out that "first arrival' is the shortest distance to the listeners' ears and, yes, you hear it first and ascribe the tonal character of the speaker to that FA sound.

Far-field guys say hogwash, the reverberant stuff happens so fast and close after FA that the listener can't distinguish between them and that's why FF dominates.

Actually, I would say that good modern-day designers recognize that flat, smooth on-axis response and smooth well-behaved far-field energy response are not mutually exclusive. Good loudspeakers can and do accomplish both--just in case both matter. The AR-91, 9, 78LS, etc are all good examples.

Steve F.

[RoyC]

I had a feeling Kloss was behind those angled drivers. Tom, is it true that Kloss left AR prior to the completion of the AR-2?

Interestingly, each of the 5 inch drivers in this array have very low dcr (2.5+/- ohms each...and they are connected in parallel to produce around 1.3+/- ohms for the unit!), and, probably for this reason, only the series resistance leg of the pot is used with it. This results in a crossover point change as the control adds resistance to the circuit to attenuate the mid(s)...though I believe the pot is usually set to maximum by most users.

Roy

[JKent]

Thanks Tom!

I actually have a couple of those Baruch-Lang speakers, produced by Kloss Industries (which I assume means Henry cobbled them together in his Cambridge loft). The basic speaker (the plain plywood one you show) sold for $25 and a fancy version (like the first one you posted) sold for $30 with hardwood trim and a nice grille cloth.

I had no idea they were same drivers as used in the AR-2a. As I've said before, I really like the 2a. And the Baruch-Lang ain't bad!

-Kent

[tysontom]

Interesting that this was Kloss' idea, not Villchur's. I wouldn't have thought that.

Without specifically agreeing or disagreeing, I will simply observe that this is the exact area in which there is so much controversy:

.....he understood that most of what you hear in a typical home listening room is primarily the reverberant sound field, not direct sound.....With the angled tweeters, there was most definitely an issue of interference effects, but these are heard only in the first-arrival, near field, not in the far field where the speaker's primary acoustic output was predominant.

Proponents of 'first-arrival' say that regardless of far-field response, the very first thing you hear--far field or near--is the so-called anechoic response, and therefore it sets the tonal stage for what follows a few scent milliseconds later. So to them, yes, interference and lobbing do matter, no matter where you sit, up close or far away. They will be quick to point out that "first arrival' is the shortest distance to the listeners' ears and, yes, you hear it first and ascribe the tonal character of the speaker to that FA sound.

Far-field guys say hogwash, the reverberant stuff happens so fast and close after FA that the listener can't distinguish between them and that's why FF dominates.

Actually, I would say that good modern-day designers recognize that flat, smooth on-axis response and smooth well-behaved far-field energy response are not mutually exclusive. Good loudspeakers can and do accomplish both--just in case both matter. The AR-91, 9, 78LS, etc are all good examples.

Steve F.

Steve,

I think your last comment sums it up well: modern designers have attempted to have smooth on-axis as well as good power response, something that was not common in the 50s. Some current experts, such as Floyd Toole, insist that first-arrival is important and audible, but nearly all of his test-room setups show the listener fairly close to the speakers, such as midway in the room or around 2 meters or so.

—Tom

[tysontom]

I had a feeling Kloss was behind those angled drivers. Tom, is it true that Kloss left AR prior to the completion of the AR-2?

Interestingly, each of the 5 inch drivers in this array have very low dcr (2.5+/- ohms each...and they are connected in parallel to produce around 1.3+/- ohms for the unit!), and, probably for this reason, only the series resistance leg of the pot is used with it. This results in a crossover point change as the control adds resistance to the circuit to attenuate the mid(s)...though I believe the pot is usually set to maximum by most users.

Roy

Kloss, who left AR before the AR-2 was finished, did most of the development work on the AR-2, and he was apparently spending most of his time on that speaker about the time that problems between Villchur and Kloss reached a crisis point. Kloss left the company in February, 1957. The AR-2 was delayed into production due to a problem with the voice coil riding out of the gap (a magnetic circuit issue that was corrected by Villchur), but made it into production in March of that year.

The Baruch-Lang speaker, with four of the 5-inch drivers, had a total impedance of 16 ohms, I believe.

—Tom