AR 3a use with new AV receiver

[Gerry S]

My "Listening room": 338.67 square feet. Volume is 8.0’ H, 13’, 5" W (13.42’) x 25’, 3" L (25.25’) = 2,710 cubic feet. For me, that's HUGE. It's really a combination living /dining area with concrete slabs for floor, ceiling and one long wall. Very great bass reinforcement (at least in the mid-bass). Using a Pioneer SX 525 reciever probably15 watts/ channel), It's driving a pair of Boston Acoustics HD 9 ($340/pair in the 1990's).

This combo sounds pretty "loud "to me MOST of the time. The speakers are about 7-8 feet apart flanking a 42" Flat panel TV. I'm sitting about 8' away (equilateral triangle). Many decades back, it was noted that even with "low-sensitivity" home speakers like the AR3a, most listeners would be satisfied driving their amps in the milli-watt region. It was only @ "live" SPL levels when equipment "sounded bad" or got fried !

I plan to do a 5.1 as soon as I re-model my unit. But it's SO much "simpler" with just 2 channels. I've got all the necessary gear for a full scale "SOTA" system but really reluctant to proceed . Difficult enough placing TWO speakers and finding the corresponding listening "sweet spot", never mind 5 or 7 + a sub !

[tysontom]

The low frequency impedance of a SINGLE AR3a can go as low as 1.3-1.5 ohms, depending on unit to unit manufacturing tolerances. It's also a REACTIVE load; not a simple "resistor". With capacitive and inductive elements, impedance at low frequencies isn’t anything like a simple "resistor" that most amps are rated at. So, mid-level amps usually go into "protection mode" and/or sound "wimpy" when a single 3a is played "loudly".

Most amps deliver there maximum voltage into 8 ohms BUT maximum current into 4 ohms (I'm talking resistive ohms). The majority of loudspeakers have impedance characteristics that match well with entry to mid-level amps. The AR3a impedance is such that only VERY rugged amps that can deliver both high voltage and high current SIMULTANEOUSLY can do the AR3a "justice" when played "hard".

There ARE speakers other than the AR3a that can also play "low" and "loud". But,they MUST be much bigger and /or complicated to do so. No free lunch in the area of box size vs. sensitivity vs. bass extension.

Lastly, from an aural perspective, to double PERCIEVED "loudness" requires a SIX to TEN time increase in available "watts" the amp must deliver. To play a single pair of AR3a's "to the max" requires beefy (heavy and costly) amps. No way around it!

Good message from Gerry S!

It sums up the difficulty driving low-Z, low-sensitivity and reactive-type loads at anything above a moderate level. It takes a lot of current capability to do it. Someone mentioned the AR Amp as being designed to drive the AR-3a -- this is certainly true to an extent, but despite its ability to produce over 90-watts/channel into 4 ohms before clipping, even that amp can experience difficulty driving the <4 ohm impedance AR-3a or the <3 ohm impedance of the AR-3. It mostly had to do with heat: I owned an early AR Amp that self-destructed into my AR-3as (the lightning-struck models I own) playing "Switched-On Bach." I sent the amp back to AR; they repaired it extensively. It then operated for about a year before it did a similar thing, but this time with smoke and sparks. I sent it back, AR profusely apologized and then sent me a brand-new AR Amp. The new one worked flawlessly (still have it), but I refrained from driving it as hard as the first one. By the way, it shouldn't be hard to understand my affection for Acoustic Research after the amazing customer service provided repairing my abused equipment over the years!

The bottom line is that these speakers demand a great deal from the amplifier, and many newer AV designs simply aren't up to the task.

--Tom Tyson

[ironlake]

Are you sure with wiring in series of the 3as you are not out of phase. I have great volume with mine and can play allot louder the system as each speaker only handles 1/2 the load as it has to with just one speaker. I am very happy with mine in series and have no problem with a loss of volume.

Using a high power bandwidth amp may be a help to me not sure but anything above the 11 oclock position on the volume control is above 120 db on peaks according to my radio shack sound pressure meter and I try and listen at no louder than 100 db to save on what is left of my hearing.

[Gerry S]

^{To ironlake. Yes, it's possible i wired them out of phase, but not likely. Frankly, its been so long ago I can't remember the specifics as to how they were set up (postioned) ,or the electronics used. I'm guessing my percieved bass reduction may be partly due to peak and dips normally encountered with ANY room/speaker/listening combination, which can then be exacerbated when 4 woofers (or more) come into play. At the time, I didn't have a Radio Shack SLM; just used my ears and program material I was familiar with. That and LOTS of man hours trying to locate FOUR AR3a's and myself to get the sound at least "similar" to a SINGLE pair.}

^{Most amplifiers put out their "maximum" power (voltage x current) into 4 ohms, but "cleanest power" into 8 ohms. It's "clean" @ 8 ohms because it's not delivering much current @ higher impedances (it's not working very "hard"). But "volume" requires maxmium current draw. And the ear is not "linear" when percieving "loudness"; bass frequencies need MORE power for the same percieved loudness compared to upper frequencies. This is especially true when listening at "low" SPL. Thus the "loudness button" on many amps of the AR3a era (and even today).}

^{Perhaps your speaker / listener location / boundary interactions just happen to give "clean" bass playback because your amplifier was not taxed. In my case, overall bass performance worsened. Setting aside level differences, I also found the stereo image very "weird" due to "comb filtering" from 4 tweeters and midranges spaced so far apart.}

^{The Allison One (which I also owned) was designed from the "ground up" AFTER learning the many challenges AR3a And AR LSTowners encoutered in "real world" appications: 8 ohm (mostly resistive) load at low frequencies, with uniform mid/treble dispersion at all angles due to carefully spaced midrange/tweeter "array" alignments. This isn't possible (at least theoretically) with double AR3a pairs. The AR 9 also used multiple woofers to increase power handling but also required beefy amps capable of lots of current at bass frequencies to do bass "justice" IF demanding bass material was to be reproduced at "realistic levels".}

^{The Radio Shack SPL meter will give a "rough" indication of playback levels. It will NOT display the frequencies (bass, mid , treble) producing those readings.Bottom line: if you find the series wiring arrangement meets all YOUR criteria for a "satisfying listening experience" using music you like to hear, don't change it.}

[soundminded]

Good message from Gerry S!

It sums up the difficulty driving low-Z, low-sensitivity and reactive-type loads at anything above a moderate level. It takes a lot of current capability to do it. Someone mentioned the AR Amp as being designed to drive the AR-3a -- this is certainly true to an extent, but despite its ability to produce over 90-watts/channel into 4 ohms before clipping, even that amp can experience difficulty driving the <4 ohm impedance AR-3a or the <3 ohm impedance of the AR-3. It mostly had to do with heat: I owned an early AR Amp that self-destructed into my AR-3as (the lightning-struck models I own) playing "Switched-On Bach." I sent the amp back to AR; they repaired it extensively. It then operated for about a year before it did a similar thing, but this time with smoke and sparks. I sent it back, AR profusely apologized and then sent me a brand-new AR Amp. The new one worked flawlessly (still have it), but I refrained from driving it as hard as the first one. By the way, it shouldn't be hard to understand my affection for Acoustic Research after the amazing customer service provided repairing my abused equipment over the years!

The bottom line is that these speakers demand a great deal from the amplifier, and many newer AV designs simply aren't up to the task.

--Tom Tyson

"By the way, it shouldn't be hard to understand my affection for Acoustic Research after the amazing customer service provided repairing my abused equipment over the years!"

Are you kidding? There's a certain individual who shall go unnamed who kept the tweeter department so busy building replacements for him they decided it was much cheaper to hire him than it was to keep reparing his LST's for free as an outside customer.

[ted99]

The original Carver Amps could drive into very low impedances. You can find them on e-bay

[Gerry S]

The original Carver Amps could drive into very low impedances. You can find them on e-bay

As good and innovative as this amp is, think it will not compete with the brute force amps when pushed hard; will go into protection mode. Think the 4 ohm power /ch is 300 watts but less than that at 2 ohms (200 ?). If you do get the Carver M400 on E-bay, be prepaired to to some re-working of the amp. I understand certain parts are very hard to find.

Carver did a "pro version" for sound reinforcement that didn't shut down as often.

[xpat]

Regarding the Adcom 555 amp - why not use one for the front left and right channels? I have used an Adcom GFA 555II for over a decade with AR9 and Sound Dynamic speakers - both of which are 4 ohms. I have never had a problem with the amp getting hot or shutting down. At 4 ohms, the amp puts out over 300W of pure power, and it shows especially when running the AR9s. With good source material - you can feel the bass in your gut and feet. The amp always has plenty of power to spare. The ony downside of the amp is its age - I do worry about the caps after such a long time. Probably time to pull the cover and do a check for leakage.

One last item, the amp has such big caps that when you cut the power, the amp continues to play for about 5 seconds at loud levels - even after all of these years.

[ted99]

As good and innovative as this amp is, think it will not compete with the brute force amps when pushed hard; will go into protection mode. Think the 4 ohm power /ch is 300 watts but less than that at 2 ohms (200 ?). If you do get the Carver M400 on E-bay, be prepaired to to some re-working of the amp. I understand certain parts are very hard to find.

Carver did a "pro version" for sound reinforcement that didn't shut down as often.

Yes, I'm still using the M400t I bought new. Had to replace the power supply caps, of course; and the small case makes it very difficult to do anything other than OEM. I was lucky and found caps that were even larger capacity and same form factor from a one-off old stock. Have had no problems, since. Bought a M1.5t on e-bay and it's still going strong, but I laid in a supply of usable caps.

[dynaco_dan]

^{To ironlake. Yes, it's possible i wired them out of phase, but not likely. Frankly, its been so long ago I can't remember the specifics as to how they were set up (postioned) ,or the electronics used. I'm guessing my percieved bass reduction may be partly due to peak and dips normally encountered with ANY room/speaker/listening combination, which can then be exacerbated when 4 woofers (or more) come into play. At the time, I didn't have a Radio Shack SLM; just used my ears and program material I was familiar with. That and LOTS of man hours trying to locate FOUR AR3a's and myself to get the sound at least "similar" to a SINGLE pair.}

Hi there

My first guess would be that the paired drivers were out of phase, thereby cancelling a lot of bass output.

In fact if this was the case I would suspect a lessening of all frequencies, not just the bass.

Some reviewers face to face the speakers and run them loud for a few days to break them in.

Perhaps today there is equipment sesitive enough to determine if there is any frequency variations of individual drivers if an early AR-3A and a later AR-3A were compared for

example.

I suspect that from year to year there was not much variation between driver output.

That being said, dies wear out over-sizing tolerances, new dies are slightly tighter, fiber material batches varie in consistancy.

There also is the extremely rare chance that a woofer or more were inadvertently factory mis-wired.

[ironlake]

would a 25 watt ceramic 4 ohm resistor give the same load as 4 ohm speaker in series.

[dynaco_dan]

would a 25 watt ceramic 4 ohm resistor give the same load as 4 ohm speaker in series.

Hi there

If the ceramic resistor was exactly 4 ohms then it will remain 4 ohms until an extreme temperature change will effect it's value or other factor.

If a speaker is 4 ohms it too will remain 4 ohms until time, temperatrue of other factor changes.

A rated 4 ohm speaker, such as an AR-3A, is approximately 4 ohms at the longtime 1,000 hz point, which is the midrange driver.

As we have seen from AR graphs, the AR-3A actually swings from less than 3 ohms to over 30 ohms from 20 - 20,000 hz.

With this knowledge we can see that the load of the speaker changes for the amplifier with different frequencies but the resistor does not.

As an amplifier over drives the resistor it will become a basic toaster or space heater.

If a speaker is overdriven the drivers will heat up until one or more burns up and quits.

If you visit to the Crown website, they discus driving a woofer and holding your hand in front of the woofers dust dome and feeling the heat pumping out and the potential

temperature and damage.

[Gerry S]

To Dynaco Dan,

I'm pretty sure I wired them correctly (for those who haven't tried "series wiring" 2 speakers to the same channel, it can get pretty cumbersome and confusing). I'm convinced that the dissapointing results I obtained was due to the placement of the four enclosures. I remember physicaly inverting one enlosure and placing it on top of the other (did this for each channel). The bass was there, but the maximum SPL I could obtain was less than anticipated. I inverted them in an attempt to "mirror image" the left & right pairs so that the multiple midrange & tweeters would arrive in a "coherent" fashion so that the spectral balance would be the same or similar compaired to a single 3a

However, the 2 woofers don't have UNIFORM "mutual coupling" throughout their operating range because each woofer "sees" a different boundary when "staggered" this way (unlike Allion Ones or the AR 9's with their dual-woofers extremely close to each other). The wide and unsymetrically spaced physical seperation of the midrange and tweeters also added to comb-filtering (which neither the AR LST or Allisons exhibit because THEIR multiple mids & tweets ARE symetrically & closely placed ).

It is my conviction that a "series wired double AR3a" would in most instances "under-perform" even if we had an amplifier with "infinite power" capable of delivering high voltages (not current) needed to "max out" each 3a in both channels. The goal for a "series-wired double 3a" is to prevent overload of bandwith - limited amps at bass frequencies. The series-wired approach will do this, but at the expense of LESS current capabilty in the bass region; the very region where we want MAXIMUM current draw (un-distorted of course) to get that viceral "whump".

The "Double Advents" in "PARALLEL" provides this "whump" by drawing maximum CURRENT from some mid -priced amps without distorting badly or shutting down. The tonal balance stays relatively the same because it's a 2-way system with a high crossover frequency; less likely to have "driver interference" when "stacked".