Alpair 7.3 Heresy

[chrisb]

Originally Posted by jimbro

Not sure what the crossover was since that was 35 years ago. Yikes. They were ESS speakers. Yea I'm sure they were clipping their amps but the ribbons seemed to be particularly susceptible to it. Could be that they were inefficient and just cranked too high. Don't remember. I never really liked the sound that much either but I'd try them again if the price was right.

Jimbro - if these were from any of the original AMT1 family, the drivers themselves were quite good - in fact the tweeter is still a world class device - recently "reissued", and quite worth the asking price, and the woofer did a pretty respectable job of trying to keep up - however the cabinets and particularly the crossovers were a joke. Keep in mind that these were introduced during the heyday of the big gas SS amp and receiver wars and it wasn't uncommon to see them driven to clipping with 150WPC or more - "Just because we can, dude" . If you've ever looked at the quality of components and needless complexity of the XO, it's not hard to understand how in conjunction with all that power the ribbons could get overdriven. IINM the current models & replacement diaphrams have been ruggedized, albeit at the expense of minor sacrifice in sensitivity and dynamics / HF extension.


Now, streamline the XO (biamp particularly) and run the AMT with that nice little 3-5 watt tube amp, and it's a whole 'nother freakin barbeque

[jimbro]

Good to know. I'd like to hear some. It's quite probable the sound I didn't like was crappy source. All the nice tube amps were sitting on the used sale shelf. I'd be doing very well if I had grabbed some of those Mac's.

[automaticmojo]

Originally Posted by simon dart

Well I thought that my little exploration might possibly raise a reaction, woo! Silverhairbp's overstating the case when he kindly refers to it as a "design."

I DO intend to FAST them, that's what I bought them for.

I was just messing around trying out the AR-SXO crossover topology for the first time, while breaking them in on my office system. (0.1mH, 8R2, 0.4mH btw Ultrakaz)

I think I should have made it clearer that my only point is: fool around sometimes good things happen that you don't expect.

Too low of efficiency IMHO to mate properly with the Heil.

[automaticmojo]

Part of the problem. aside from clipping, is running the Heil too low.
The use of a transiton driver, crossing over to the Heil around 2500 is the only way to go IMHO-exactly what the ESS AMT3 did. The Heil is now in it's ideal range.
The AMT3 is the best desgn ESS produced, and when properly refurbed, resealed, and recapped will give most speakers a serious run for their money-the imaging and detail is amazing.
I have had Great heils for years- those diaphrams are hard to blow, unless you bypass the fuse, and drive your amp into clipping/DC.
The fuse doesn't effect the sound one bit-I have experimented many times-can't hear any difference period-so keep them fused, or don't over drive them.
Easy to do, as they play so clear-with little compression-so it's hard to tell your taxing your amp.
An ideal modern AMT3 would be to take 2 Eminence/OCS 1040SF's, or perhaps a Audax PR240MO, operating in a 3.0 Cu ft enclosure.
The woofers crossing over to a Audax HM130CO driver at around 500 to 750 hz, and the Audax Crossong over to the Heils @2500hz.
2 way designs with a 6 1/2 to 8 inch woofers, are better then the larger 2 way designs as far as midrange/midbass reponase goes (i.e. hole)-but you are really defeating your ourpose by running a low efficiency woofer-thus having to excessivley pad the Heil to achieve frequency balance.

Originally Posted by chrisb

Jimbro - if these were from any of the original AMT1 family, the drivers themselves were quite good - in fact the tweeter is still a world class device - recently "reissued", and quite worth the asking price, and the woofer did a pretty respectable job of trying to keep up - however the cabinets and particularly the crossovers were a joke. Keep in mind that these were introduced during the heyday of the big gas SS amp and receiver wars and it wasn't uncommon to see them driven to clipping with 150WPC or more - "Just because we can, dude" . If you've ever looked at the quality of components and needless complexity of the XO, it's not hard to understand how in conjunction with all that power the ribbons could get overdriven. IINM the current models & replacement diaphrams have been ruggedized, albeit at the expense of minor sacrifice in sensitivity and dynamics / HF extension.


Now, streamline the XO (biamp particularly) and run the AMT with that nice little 3-5 watt tube amp, and it's a whole 'nother freakin barbeque

[chrisb]

Originally Posted by automaticmojo

Part of the problem. aside from clipping, is running the Heil too low.
The use of a transiton driver, crossing over to the Heil around 2500 is the only way to go IMHO-exactly what the ESS AMT3 did. The Heil is now in it's ideal range.
The AMT3 is the best desgn ESS produced, and when properly refurbed, resealed, and recapped will give most speakers a serious run for their money-the imaging and detail is amazing.
I have had Great heils for years- those diaphrams are hard to blow, unless you bypass the fuse, and drive your amp into clipping/DC.
The fuse doesn't effect the sound one bit-I have experimented many times-can't hear any difference period-so keep them fused, or don't over drive them.
Easy to do, as they play so clear-with little compression-so it's hard to tell your taxing your amp.
An ideal modern AMT3 would be to take 2 Eminence/OCS 1040SF's, or perhaps a Audax PR240MO, operating in a 3.0 Cu ft enclosure.
The woofers crossing over to a Audax HM130CO driver at around 500 to 750 hz, and the Audax Crossong over to the Heils @2500hz.
2 way designs with a 6 1/2 to 8 inch woofers, are better then the larger 2 way designs as far as midrange/midbass reponase goes (i.e. hole)-but you are really defeating your ourpose by running a low efficiency woofer-thus having to excessivley pad the Heil to achieve frequency balance.

or for that matter the stock woofers and PR from AMT1, Eminence Beta6 midrange, and a new enclosure designed to emulate the originals - for customer who'd just spent the best part of $400 having surrounds replaced all 4 active and passive drivers and grilles rebuilt.




XO design by others courtesy LMS measures and LEAP modeling

[automaticmojo]

Very nice indeed!
The Eminece Alpha 6A is actually a very good driver for the money, and a great substitute for the stock AMT3's transition drivers- as the tube volume of the transition drivers enclousre is right on the money with the Alpha 6A.

[automaticmojo]

It's easy to gain a db or 2 of sensitivity, plus lower your ESR by substituting quality poly caps, and large gauge inductors with the stock crossover. Unless your refering to the 4 coil Zobel network with the early design AMT3-the later 3 coild design in very straight foward-and fairly simple-and also rely's on the generious overlaps of the stock drivers.
The cabinet can be improved by a few basic items-sealing and strengthening.
ESS now has reissues for the AMT1 10" and 12" driver. AS for the AMT3 the 1040SF is the closest you will find to the stock woofer-a modern equivilent that keeps up a bit better then the stock Alnico's woofer did-but mind you the 1040SF's output is about even with the Heil-instead of 2-3db down-so in that respect the 'voicing" will change.But if you recharge the Alnio'x you will come close. The 1040SF is similiar to the stock woofer, in that in rolls of smoothly, and lacks a impendnence peak, typical of a lot of today's drivers.
The Alpha^A is a great substitute for the stock foam surround driver-but may need to be adjusted via a l-pad or resistor for the earlier desing that used the 4 coil Zobel and Peerless rubber surround transition/mid driver.

[automaticmojo]

Originally Posted by automaticmojo

It's easy to gain a db or 2 of sensitivity, plus lower your ESR by substituting quality poly caps, and large gauge inductors with the stock crossover. Unless your refering to the 4 coil Zobel network with the early design AMT3-the later 3 coild design in very straight foward-and fairly simple-and also rely's on the generious overlaps of the stock drivers.
The cabinet can be improved by a few basic items-sealing and strengthening.
ESS now has reissues for the AMT1 10" and 12" driver. AS for the AMT3 the 1040SF is the closest you will find to the stock woofer-a modern equivilent that keeps up a bit better then the stock Alnico's woofer did-but mind you the 1040SF's output is about even with the Heil-instead of 2-3db down-so in that respect the 'voicing" will change. But if you recharge the Alnio'x you will come close. The 1040SF is similiar to the stock woofer, in that has a smooth frequency reponse, rolls of smoothly, and of course efficient.
The Alpha6A is a great substitute for the stock foam surround driver-and should work for the earlier rubber surround Peerless transition driver as well.

[wallacefl]

Originally Posted by ultrakaz

Hi Simon,

You were clear enough. You opted to share your favorable result/discovery, but were met with negative responses from those who have not even heard your implementation. Good grief(!), I'm a bit surprised by the responses. Why not cross the 7.3 to a tweeter? Perhaps, one doesn't like the treble coming off a 4" aluminum cone, notwithstanding beaming and/or breakup. Personally, I think the 7.3 would make an awesome mid where the driver is being used in its most effective pass band, or even a mid-woofer where shallow slopes could be used in a smallish box. Keep up the "heresy", and don't be afraid to go outside the lines with creativity.

Having heard the 7.3 I think it would make a good little monitor(or midrange) but I have a pair of RAAL 20-xr ribbons and would love if someone could work up a 24db low pass crossover at 1800hz so I could try my little experiment...any help appreciated as I have no design experience or measuring equipment other than my ears.

[ultrakaz]

Originally Posted by wallacefl

Having heard the 7.3 I think it would make a good little monitor(or midrange) but I have a pair of RAAL 20-xr ribbons and would love if someone could work up a 24db low pass crossover at 1800hz so I could try my little experiment...any help appreciated as I have no design experience or measuring equipment other than my ears.

Hi Wallacefl, the beauty of the Acoustic Reality design is its simplicity; capacitorless, low parts count and first order-ish. Doing so preserves the single driver sound more or less. A proper 24db crossover is going to take a lot of parts and may very well suck the life out of the 7.3. Perhaps, an electronic low pass might be an easier propostion with added eq flexibility.

Or... Why not use the RAAL, which is reputedly not easy to blow up, in the AR crossover schema? You could half the value of the series coil to the 7.3 and crossover the RAAL an octave higher. Then adjust the R values by listening. Just don't turn it up too loud! Some may disagree, but your ears are your best tool.