Thoughts on Amps for 3's

[ar_pro]

I'd forgotton about the Adcom 555II - it was a great amplifier - reliable, plenty of power, and incredibly quiet.

It would be an excellent match for the AR-3a.

I used to have a pair running in vertical bi-amp mode on the AR-9, with a LF equalizer for the woofer sections, and "driven" by the Adcom passive preamp.

It was an extremely transparent set-up, with better results than many MUCH more expensive systems.

Last I looked, you could get a good 555II for under $400; now that is a bargain!

[tysontom]

>Tom... do you know why AR3 was originally designed as 4 ohm model, even later original models with 10" and 8" woofers were nominally 8 ohm ones? In 50´s amps used tubes and you could use suitable output transformer tap for driving speakers... and actually using lower ratio tap (8 ohm or even 16 ohm tap) do offer better coupling between power transformer primary and secondary. There was not too much advantage being 4 ohm model during early solid state era either? I must have missed the point here.

>Best Regards

>Kimmo

Kimmo,

Sorry, I nearly missed your question.

The AR-3 was based on the AR-1, which was a 4-ohm design.

When Edgar Villchur developed the acoustic-suspension speaker in the spring of 1954, he chose the Western Electric 728B 12-inch driver to use for his original acoustic-suspension prototype. He modified that speaker simply because (in typical WE fashion) the speaker was of very high quality and could be easily disassembled in order to change the spider assembly and the surround to lower the resonance, etc. The 728B was a 4-ohm full-range driver, as was the 755A "tweeter" used in the AR-1. Therefore, when the production-unit AR-1 speaker was built, the new (#3700) woofer voice coil was wound at 4-ohms impedance to match the Altec Lansing (WE) 755A tweeter that had been selected.

At the time of the AR-1, there were not many amps that could easily drive the AR-1, but there were several amps capable of driving the speaker satisfactorily, such as the Fairchild 75-watt mono amps, the big Fisher mono amps, the McIntosh MC60s and the early Dynaco Mark II and later Mark III. Insofar as the AR-1 was a "no-compromise" loudspeaker design, Villchur decided to concentrate on performance, low distortion and quality—somewhat at the expense of efficiency. He knew that there were plenty of amplifiers capable of driving the AR-1 well.

Therefore, when the AR-3 came along in late 1958, it used the AR-1 4-ohm woofer, so the tweeters were wound for 4 ohms as well. The AR-3a at first used the #3700 Alnico woofer (up to late 1969 or so), and therefore the tweeters in that speaker were also wound for 4-ohm impedance. The 200003-series ceramic-ferrite woofers were subsequently introduced to the AR-3a, and since the tweeters were 4-ohms, this new woofer was also wound for 4 ohms, and so it goes....

The AR-2 was a compromise of sorts, so there was a decision to make it an 8-ohm speaker to better match lower-powered amplifiers and receivers of the day (1957). The same was true for the 1964 AR-4.

—Tom Tyson

[der]

Tom,

Fascinating reading there! I've read some of that previously but still thanks for the post. My AR3a's that I bought sometime in 1970 have woofers with cloth surrounds. Can I deduce that they are the Alnico #3700's? I've had them out a couple of times but really didn't look at them that closely. I'll be removing them again soon to re-cap my crossovers. I plan on refreshing the surrounds like I've already done with the AR4x woofer surrounds on the pair I'm currently refurbishing.

I have some concern about the condition of my tweeters. I replaced the midranges a little over 20 years ago after my son blew them out. I'm unsure if I'm getting all I should out of those old dome tweeters. Could be my 67 year old ears just can't hear that much any more at those frequencies.

der

[tysontom]

Tom,

Fascinating reading there! I've read some of that previously but still thanks for the post. My AR3a's that I bought sometime in 1970 have woofers with cloth surrounds. Can I deduce that they are the Alnico #3700's? I've had them out a couple of times but really didn't look at them that closely. I'll be removing them again soon to re-cap my crossovers. I plan on refreshing the surrounds like I've already done with the AR4x woofer surrounds on the pair I'm currently refurbishing.

I have some concern about the condition of my tweeters. I replaced the midranges a little over 20 years ago after my son blew them out. I'm unsure if I'm getting all I should out of those old dome tweeters. Could be my 67 year old ears just can't hear that much any more at those frequencies.

der

der,

Yes, those woofers in your AR-3a with cloth surrounds are the (AR-3 version) 3700, AR's well-known classic woofer. These were used in the AR-3a until the late 1969, early 1970 period. It's an exceptionally fine driver, and AR continued to improve it right up to the end of production. If the surrounds on your speakers don't leak air, you probably should not treat them as you can affect the resonance slightly by coating them. In other words, "do no harm." On the other hand, if they leak, then you should treat them with some of Roy's surround treatment.

Some AR-3a tweeters are now showing signs of deterioration due to the urethane-polymer foam suspension pieces in the gaps (three slots) and the foam damping piece under the dome itself. Not all tweeters are bad, but many are beginning to show signs of deterioration. At 67, one's hearing beyond 8-10kHz is beginning to retreat as well, so the two go hand-in-hand. Remember, too, that the normal output of the high frequencies in the AR-3a is down 5-7 dB at 20 kHz, relative to the midrange, so the high frequencies were somewhat reticent anyway, yet the dispersion is so good that the overall acoustic power is still excellent by any standard. Once the crossover has been updated and the level controls refurbished, give the speakers another close listen to determine the ultimate condition of the tweeters.

Ironically, it's the midrange in the AR-3a that remains virtually unchanged through all the years. There is little to deteriorate, and no foam was used in the manufacturing process of the driver itself.

--Tom

[der]

I know I have a slight hearing loss in my left ear but it's but it's been a while since my last hearing test so I'm not sure if that's any worse or not. I definitely still hear my 3a tweeters - they are functioning. As to the woofer cloth surrounds, I'm not that sure. The standard test of pressing the cone to test is open to personal interpretation. When I finish up my 4x's I'm going to recap the 3a's and see how they sound then. I detect some "muddiness" in the mid bass and midrange with some material. I have a feeling that refurbiing the cross-overs will help there.

der

[owlsplace]

I know I have a slight hearing loss in my left ear but it's but it's been a while since my last hearing test so I'm not sure if that's any worse or not. I definitely still hear my 3a tweeters - they are functioning. As to the woofer cloth surrounds, I'm not that sure. The standard test of pressing the cone to test is open to personal interpretation. When I finish up my 4x's I'm going to recap the 3a's and see how they sound then. I detect some "muddiness" in the mid bass and midrange with some material. I have a feeling that refurbiing the cross-overs will help there.

der

Join the crowd with the hearing loss. I finally picked up a decent period amp for the AR-5s today. The bass and midrange have never sounded cleaner. I don't think I would want them to sound any brighter. The 5s and 3s are probably about the same efficiency although the lower impedance load of the 3s would tax the amp more. Anyway they are less efficient than the ADS L980 I have them sitting on top of but I like the sound of the 5s better even though the L980s have an extended top end.

With the amp being driven straight from the CD player sans preamp the 5s rattle the furniture with no sign of distortion with the gain controls on max. Having an amp with sufficient headroom is definitely a joy to hear.

I wanted the Mark IIICM but hey, this one presented itself.

Roger

[der]

Looks like a nice one Roger. I've been lookin but haven't made up my mind as yet. One of the issues I have is limited space for equipment in my listening room. It was decorated by my wife and I don't have much room for anything other than a receiver, CD player, and one turntable. I might be able to squeeze a lower profile power amp and preamp in wtith the CD player on the two shelves available but it would be tight. My turntable sits on top of the cabinet.

[ra.ra]

All this talk about sophisticated amps is way above my pay grade, but I just have to chime in and say that this combo of AR-3's with slimline McIntosh separates, which I heard in this listening room at a regional event yesterday, was simply sublime and among the very best complimentary set-ups I have ever had the good fortune to experience.

[owlsplace]

der,

....

Ironically, it's the midrange in the AR-3a that remains virtually unchanged through all the years. There is little to deteriorate, and no foam was used in the manufacturing process of the driver itself.

--Tom

Tom: I think the midrange in the 3 and 5 models was always the main attraction, at least for me -- even more so now that my hearing is fading. I A/B'd the 5's I rebuilt against ADS L980's today and the midrange is much more forward on the 5s. To be fair the 980s were under the 5s and the bass coupling to the floor was making them a little boomy. Then again I didn't compensate for the ESR change when I recapped the 5s. It will be interesting to see how the other set of 5s in the process of being rebuilt will sound with the HiVi tweeters.

The sound of the 5s and L980s together was pretty impressive depending on the musical program and the amp didn't complain about the load. I still like to listen to angels (soft music) on the 5's alone..... ... They are just mellow and there is a sentimental attachment there for me.

der: you can always wire a power amp in the closet/basement/attic to get it out of the way an amp with some cojones behind the 3's will put a smile on your face.

ra.ra: no bank breaker on the SAE amp. The retired postal worker I got it from had some major equipment though which was way out of my league -- let's see if I can recount some of it -- oh, he said his wife was a problem as she encourages him -- two Mickey tube amps, two Marantz tube amps, another set of tube amps, some SS amps, Snell type A;s, Klipsch La Scala's, ESS towers (70s vintage sentimental value) speakers, etc....

Roger

[stupidhead]

Hello folks,

I am actually in negotiations and am very close to possessing a set of 3's. Pretty stoked about it and thought this topic would be a reasonable place to pose this question, will my Marantz 2325 drive them alright. I do have a set of 5's that I have not finished rehabbing as well, and am wondering about having the 3s and the 5s together but 4 and 8 ohm respectively has me confused. I don't really understand this piece of the lingo and am hoping someone can explain the ohm conflict and also if the 2325 has the cojones to drive this pair?

Geoff

[der]

I would think your Marantz would be up to the task of driving the 3a's. I think it provides 125 wpc into 8 ohms. I would guess even more into 4 ohms. I'm not that technical so I can't really comment on running all four at the same time. Intuitively, it would seem that the amp would see something between 4 and 8 ohms but I just don't know.

Congrats on your 3a's if you land them!

der

[Jeff_C]

Hello folks,

I am actually in negotiations and am very close to possessing a set of 3's. Pretty stoked about it and thought this topic would be a reasonable place to pose this question, will my Marantz 2325 drive them alright. I do have a set of 5's that I have not finished rehabbing as well, and am wondering about having the 3s and the 5s together but 4 and 8 ohm respectively has me confused. I don't really understand this piece of the lingo and am hoping someone can explain the ohm conflict and also if the 2325 has the cojones to drive this pair?

Geoff

I know little about speakers, and only a little schoolboy physics memory of resistance and impedance. If you wire the speakers in series (such that the signal flows from the + on the amp through one speaker + to - and then the other speaker + to - and then to the amp -) the overall nominal impedance will be 12 Ohms (8+4) , but the 8 Ohm speaker will convert twice as much of the voltage (signal) to sound energy as the 4 Ohm speaker. It would not be a good idea to wire the speakers in parallel (all + terminals wired together and all - terminals wired together) as the resulting nominal impedance will be too low at 2.7 Ohm (1/R = 1/4 + 1/8). If you do wire them in parallel the 4 ohm speaker will convert twice as much of the signal to sound energy than the 8 ohm speaker.

What will happen in practice is even more unpredicatable because the impedance of each speaker will be different across the frequency band.

I hope I've got that right for you and that it makes sense.

[djcheung]

I have yet to get some power amps to drive my AR3a and AR9.

Currently I am using the Yamaha Z11 to drive them.

They sound ok but then I don't normally crank them up too far.

The Z11 doesn't get too hot when it is driven reasonably hard.

I can't turn them up too high fearing neighbours may start complaining.

David.

[stupidhead]

Hi Jeff, and it sort of makes sense. Series not parallel is I believe the bottom line of what you are suggesting. I had a feeling there was some sort of conflict, can anyone else shine a little more light on this please?

[Jeff_C]

@stupidhead

If you want to try the AR3 and AR5 together then I would wire them in series. But the result may not be very good because the AR5 should sound louder having the higher series impedance than the AR3. Then there is a potential problem in that the natural sound of the 2 sets of different speakers may not complement one another as it would be hoped.

It would be much more straightforward with 2 sets of AR3, because the speakers are identical, and the impedances are identical. In series 2 x AR3 would give an easy load of 8 Ohms nominally, (in parallel it would be 2 Ohms nominally [and do not forget that the impedance can drop lower than the nominal speaker impedance at certain frequencies]).

[stupidhead]

I could only hope to have two sets of 3s. Thanx for the input.

[owlsplace]

I could only hope to have two sets of 3s. Thanx for the input.

I gave up on getting any 3's, can't compete with the Asians and chances of finding them at a thrift store are really slim. I would jump at a chance to hear a pair properly set up though. In the meantime I picked up the ADS L980's when they came by locally which satisfy any program material that likes deeper bass coverage like jazz, rock, etc.

I don't have any trouble paralleling the 980's with the 5's as they are both 8 ohm speakers. I do have them wired through a Russound impedance matching switch box but it is in the bypass mode. Not sure what is in the box but I can see two large resistors through the ventilation holes.

If amplifier loading is an issue it may be more logical to drive them with separate amps if you want to listen to them at the same time. There are amps out there that will drive 2 ohm loads but you won't be able to balance the levels without using series resistors or impedance matching transformers. At least that is my take.

Not sure you can get away with wiring them in series without a major redesign of the crossovers. There would be problems with signal phase.

Roger

[owlsplace]

I wanted the Mark IIICM but hey, this one presented itself.

Wouldn't you know an SAE Mark IIICM showed up locally at about 4X the price of the SAE Mark IIB that is now playing... well, I guess they are fairly rare, but maybe another day...

Roger

[DavidDru]

That's the way it works. Last week I scored a great deal on a Pair of Heresy's only then a few days later the opportunity to buy a pair of Altec Valencias arose that I just couldn't pass on. Now I am swimming in horns! Hey, needed something for my tube amp now that we have determined it wont work for my AR's!

There is an Adcom GFA 545 on local Clist. Not quite enough power I am thinking.

[iso]

Why tube amp will not work with AR?

If output impedance of amplifier is less than 1 ohm, there is also 1,5 ohm length of voice coil out of magnetic gap (long coil in short gap woofer), 0.8 ohm DCR and 0,7 ohm reactance of crossover coil and also small amount of cabling resistance is series to signal at resonance. So... having source with zero or 0,7 ohm output impedance does not make big difference.

Output impedance does have some effect to frequency response... but this should be minimal compared to room acoustics.

Best Regards

Kimmo

[DavidDru]

Kimmo,

To me you are speaking finnish! not sure what that technical stuff means but I was taking from most of the previous posts that 3's really like power that can reach down into those 4ohms when needed to really get the most out of them. Much like my Maggies I guess. Meanwhile the 2ax should do well with non high current power just fine. My Dynaco St70 tube amp is only rated at 35w/side so it might struggle a bit.

[Sonnar]

That's the way it works. Last week I scored a great deal on a Pair of Heresy's only then a few days later the opportunity to buy a pair of Altec Valencias arose that I just couldn't pass on. Now I am swimming in horns! Hey, needed something for my tube amp now that we have determined it wont work for my AR's!

There is an Adcom GFA 545 on local Clist. Not quite enough power I am thinking.

Hello David, I have some experience in horn speakers. Heresy are very obsolete , poor bass response and ugly mid and high range, and the same for big La Scala, too little short basshorn. Only Cornwalls offers a good reproduction of bass , but Klipsch uses very cheap drivers which causes very harsh mid and high range. I have a pair of Valencias, excellent drivers , but the 416 8b woofer needs a larger cabinet to deliver full bass response, almost 9 cu. in. , and the 811b / 511b sectoral horns are obsolete and rings like a bell. I have a friend who has one of the best sounding horn speakers I' ve ever heard, a 416 8b Altec in 620A cabinet, Altec 288 1.4" drivers with wood made Fostex H320 horns, JBL 075 tweeters. Another excellent speaker is the Altec 604 8g Duplex in 620A cabinet. Every speaker I 've mentioned has its particular quality, but no one sounds really like music, they shows a seductively artifact reproduction. In my opinion, only AR 3 /3a are very close to a neutral, uncolored , well balanced reproduction of classic acoustic instruments. Best regards, Adriano

[iso]

David

It might be 35wpc power rating that makes your Dynaco ST70 to struggle. 35 wpc amplifier is 35 wpc amplifier using tubes, fet´s or bipolar´s. Most tube amps do have output taps to adjust voltage/current capability of output stage to be suitable for speakers. Most tube amps do have 4/8/16 ohm taps and even 1 and 2 ohm taps have been used. McIntosh solid state gear do use auto transformer for similar purpose.

This technical stuff is what we actually hear... if there is some defect in design we will hear it. Tubes like all other devices do have their limitations, but with good design they are perfectly suitable for driving well designed speakers... maybe direct driving Apogee Scintillas would be too much.

Best Regards

Kimmo

PS when ST70 was serviced... are reservoir caps and tubes fresh. Are other components and adjustments within spec?

[DavidDru]

David

It might be 35wpc power rating that makes your Dynaco ST70 to struggle. 35 wpc amplifier is 35 wpc amplifier using tubes, fet´s or bipolar´s. Most tube amps do have output taps to adjust voltage/current capability of output stage to be suitable for speakers. Most tube amps do have 4/8/16 ohm taps and even 1 and 2 ohm taps have been used. McIntosh solid state gear do use auto transformer for similar purpose.

This technical stuff is what we actually hear... if there is some defect in design we will hear it. Tubes like all other devices do have their limitations, but with good design they are perfectly suitable for driving well designed speakers... maybe direct driving Apogee Scintillas would be too much.

Best Regards

Kimmo

PS when ST70 was serviced... are reservoir caps and tubes fresh. Are other components and adjustments within spec?

Kimmo,

Unfortunately I was speaking with an assumption about the challenges of using the ST70 with the 3's as I still have not completed my restoration of the 3's. We shall see how it goes when I am done, but I would bet several other posters on here have already tried the St70 with the 3's at some point and could chime in on their previous results. The ST70 does have the variable ohm taps. It is something I acquired recently simply because the price was so good and it is in near mint original condition. Also because it is in that condition, and works as is, I have hesitated replacing any components on it as of yet. I figure I could try it with various speakers for a while before doing anything like changing out the selenium rectifier, old caps etc. Actually come to think of it I have not even tried it with my 2ax's yet. Maybe this weekend.

Adriano,

Of course once i purchased the ST70 I started to watch for horn speakers and the Heresys and Valencias came up locally for exceptionally low prices and again I could not resist. I figured it would be fun giving them a try for a while as I could always sell them. In the past I had never enjoyed the nature of Klipsch speakers, but I thought I would give it a try with some better vintage gear and see what I could make of it. So far, meh. Adding my subwoofer in combination with the Heresy's has helped add the missing bottom end. I have only used the Valencias with a SS amp thus far and I might switch them over to the ST70 today to see what comes of it. As it is, the Valencias are so damn big so they will likely get sold first. Certain aspects do come through very nicely with them, but other aspects seem missing. I have a lot to fine tune including speaker location and orientation before jumping to conclusions. I will not be getting into swapping horns, drivers, and cabinets etc.

Yes I am going so many different directions right now with various pieces of equipment (laugh, laugh, chuckle, chuckle, snort) and need to narrow my focus a bit over the winter if possible. All this great input from you guys is very helpful for sure. This thread was started with the intent of narrowing down amp choices that could work well with the speakers I will keep (which right now appear to be the 3's for sure), but may allow some versatility in use with others moving forward. If the 3's really like power and current, thats the same as what my Magneplanars do best with so that would be a good type of amp to have available for both it seems. it's a place to start anyway.

[owlsplace]

Anyone use any of the pro amps on ARs? Like the Ashly FET-200 or 500 models? I think these are "class A" or maybe "AB" designs and imagine a nice match for acoustic suspension type speakers.

Roger