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a/d/s M20


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#1 Guest_nathanso_*

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Posted 26 January 2007 - 05:52 PM

Here's a rarity, the a/d/s M20. $3500 MSRP in 1991.

I've owned a pair (not these pictured) for a few weeks and am duly impressed. In addition to the visible midrange-woofer and tweeter, inside each cabinet is a set of 8" woofers in bandpass configuration. Anyone have any a/d/s M20 or M30 speaker info?

http://www.n8softwar...20/ads_m20a.jpg
http://www.n8softwar...20/ads_m20b.jpg
http://www.n8softwar...20/ads_m20c.jpg

#2 Guest_nathanso_*

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Posted 12 June 2008 - 03:48 AM

I gave these away to a friend only to get them back some months later (too big, low waf). In my previous testing with my McIntosh MC7300 amp I found their bass to of the one-note variety, though a powerful note it was. Now returned to the roost, they ended up in my family room HT system powered by a new 100wpc Panasonic class D HT amp. And lo and behold.. multi-note bass at last.

#3 Diamonds&Rust

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Posted 14 June 2008 - 07:55 PM

I gave these away to a friend only to get them back some months later (too big, low waf). In my previous testing with my McIntosh MC7300 amp I found their bass to of the one-note variety, though a powerful note it was. Now returned to the roost, they ended up in my family room HT system powered by a new 100wpc Panasonic class D HT amp. And lo and behold.. multi-note bass at last.


Strange, isn't it?

The room, the electronics, the... everything.

No wonder we can't just "settle" on something and be done with it.

I've been *very* surprised by my little Panasonic class D receiver every time I've asked it to drive anything other than AR 12" woofers.

#4 tysontom

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Posted 01 July 2008 - 03:27 PM

[quote name='nathanso' date='Jan 26 2007, 06:52 PM' post='71146']
Here's a rarity, the a/d/s M20. $3500 MSRP in 1991.

I've owned a pair (not these pictured) for a few weeks and am duly impressed. In addition to the visible midrange-woofer and tweeter, inside each cabinet is a set of 8" woofers in bandpass configuration. Anyone have any a/d/s M20 or M30 speaker info?

These a/d/s/ models, the M20 and M30, were the last of a dying breed from this company. Both the M20 and M30 utilized dual-woofer band-pass bass enclosures. The "modern" band-pass configuration derives mainly from the excellent work done by brilliant KEF speaker designer, Laurie Fincham. Fincham was able to capitalize on the essence of sealed acoustic-suspension woofers feeding into a tuned port or "band-pass" enclosure. The result was greatly improved low-frequency extension and low distortion, but a relatively narrow upper-bass range caused by the acoustic cut-off frequency -- a great advantage. Therefore, typically, the crossover frequency was in the 150-200 range, and lower-frequency extension could be as low as 18 Hz as in the case of the KEF R107 and the a/d/s/ M30, and almost identical design. This design, also using the excellent 24db/octave Linkwitz-Riley crossover network, was originally introduced by KEF with the model 104, I believe, but the biggest contribution came in 1979 with the KEF flagship R107, a speaker using two 10-inch a/s woofers mounted in sealed enclosures firing into a tuned port. The R107 was among the finest loudspeakers ever designed. I would think that the M30 -- rarely seen -- would have also been in this category. It is quite possible that Laurie Fincham had a part in the design of the M30, but there is no reference to that assumption.

The M20 and M30, therefore, were very similar in performance in low bass to the KEF 104 and 107, and each speaker was at the top of its class. The quality and precision of a/d/s/ drivers (not to mention use of butyl-rubber surrounds) was probably an advantage over the KEF drivers, which used stamped metal baskets and foam surrounds. The real key to the band-pass enclosure was proper tuning and alignment. Without this element, the speaker could sometimes have peaky, one-note bass.

--Tom Tyson

#5 Guest_Musicman159_*

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Posted 10 July 2008 - 05:32 PM

I saw and listened to both of them (M20 and M30) back in the late 80s in a HiFi store in Laredo Tx. I actually bought a pair of M30 in Rosewood finish but before taking them out of the store I end up not taking them and getting a pair of B&W 801 Matrix S3.... I still regret not keeping the M30.

I would buy a pair of M30 or M20 in good condition (specially in rosewood) at anytime they become available.

The only problem with these speakers is that they are VERY current hungry. I am not surprised about the comments regarding the sound with the McIntosh 7300. The older McIntosh amps had high watts but low current output (not the case of ne newer models). I actually saw a MC2500 lighting up the power gad LED like a Christmas tree drving a pair of M20 not at very high volume.

The owner of the store had a pair of the M30 at his home and the only way to drive them correclty was using a pair of Threshold SA-12e monoblocks. These are monsters. Only 250 watts but with current output over 130 amperes.

If somebody want to drive the M20 or M30 to their full potential a high current amplifier is needed.

#6 tysontom

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Posted 11 July 2008 - 02:02 AM

I saw and listened to both of them (M20 and M30) back in the late 80s in a HiFi store in Laredo Tx. I actually bought a pair of M30 in Rosewood finish but before taking them out of the store I end up not taking them and getting a pair of B&W 801 Matrix S3.... I still regret not keeping the M30.

I would buy a pair of M30 or M20 in good condition (specially in rosewood) at anytime they become available.

The only problem with these speakers is that they are VERY current hungry. I am not surprised about the comments regarding the sound with the McIntosh 7300. The older McIntosh amps had high watts but low current output (not the case of ne newer models). I actually saw a MC2500 lighting up the power gad LED like a Christmas tree drving a pair of M20 not at very high volume.

The owner of the store had a pair of the M30 at his home and the only way to drive them correclty was using a pair of Threshold SA-12e monoblocks. These are monsters. Only 250 watts but with current output over 130 amperes.

If somebody want to drive the M20 or M30 to their full potential a high current amplifier is needed.


These are some interesting comments, but I don't follow you on the requirement for such high current for these a/d/s/ speakers or the McIntosh solid-state power amps not being able to deliver sufficient current current up to their rated power. Most of the Mac amps had multiple output taps, including 4-ohms and lower, such that full current commensurate with the rated power (per Ohm's Law) would be delivered to any load, continuously, both channels operating. I had a MC2500 amp for many years, and it had a 1-ohm, 2-ohm, 4-ohm tap, in addition to higher-Z taps, which would be very compatible with the M30's 4-ohm impedance and 91 dB sensitivity. With each lower-impedance tap, of course, the amp would swing twice the current across the load for a given voltage, and the amp was rated for full power into each impedance tap. In other words, there is no way that a MC2500 has insufficient current to drive an M30 or M20 speaker, especially since the M30 is rated at 91 dB sensitivity.

I had my MC2500 amp tested at a McIntosh Clinic soon after I purchased it, and it delivered over 725 watts-per-channel RMS continuous output into 4 ohms right up to the point of throwing the 15-amp breaker on the test bench. The voltage sag was so great that the lights on the test bench grew dim. The maximum input power dissipation for the MC2500 was close to 22 amps, so the amplifier could easily overload a 15-amp standard wall circuit; after that test in the dealer showroom, I wired in a dedicated 20-amp circuit at home used only for the amplifier, and the voltage never sagged. So now the MC2500 could deliver its full-rated (plus some) power into any load, continuously with approximately twice that amount as an instantaneous peak, before the Power Guard circuit softened the output. Several Krells and Threshold amplifers, among other exotic amps, were designed to be able to produce very high brief power peaks, and this is where the high current comes into play, but these power levels are very brief before distortion sets in. The point is, the MC2500 could effortlessly drive an M20 or M30 to its full capabilities, and for that matter, any loudspeaker designed for home use. I would suspect that if an M20 was causing the Power Guard light to flicker with the music at "not very high volume," most likely the speaker was connected to the wrong output tap on the amplifier, thus limiting the actual power being delivered.

--Tom Tyson

#7 Guest_nathanso_*

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Posted 28 February 2009 - 05:08 PM

I saw and listened to both of them (M20 and M30) back in the late 80s in a HiFi store in Laredo Tx. I actually bought a pair of M30 in Rosewood finish but before taking them out of the store I end up not taking them and getting a pair of B&W 801 Matrix S3.... I still regret not keeping the M30.

I would buy a pair of M30 or M20 in good condition (specially in rosewood) at anytime they become available.

The only problem with these speakers is that they are VERY current hungry. I am not surprised about the comments regarding the sound with the McIntosh 7300. The older McIntosh amps had high watts but low current output (not the case of ne newer models). I actually saw a MC2500 lighting up the power gad LED like a Christmas tree drving a pair of M20 not at very high volume.

The owner of the store had a pair of the M30 at his home and the only way to drive them correclty was using a pair of Threshold SA-12e monoblocks. These are monsters. Only 250 watts but with current output over 130 amperes.

If somebody want to drive the M20 or M30 to their full potential a high current amplifier is needed.


I decided to re-visit my M20's which have been deployed in an HT system in our den these past months. So I hand-trucked them into our living room and positioned them just inside my regular 2-ch speakers, a pristine set of Acoustat 2+2's. The M20's sure looked petite, so juxtaposed! My amp these days is a PS Audio HCA-2 (a keeper, finally!) and it had no trouble driving the M20's, producing ample volume and loads of multi-note bass. After a few days, though, my brain was missing the crystalline clarity of my stats and the M20's headed back to the den, though the experience left me seriously considering a powered sub for my 2-ch system.

#8 Scotty speaker nut

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Posted 11 January 2011 - 11:17 PM

I have bought and sold SO MANY speakers since I got into stereo in 1975. I just found what I think MAY be the ones to settle on: A/D/S/ MV30/t They are tower speakers with two 5 1/2" woofers and a 1" dome tweeter. VERY heavy! The sound is phenomenal, great sound stage. I just wish they were more efficient. But then I got spoiled by my DCM KX-12s. Anyone else had these A/D/S/ ? All I've found is they were made in 1996 and retailed for $1200 USD. Certainly the most expensive speakers I've ever owned! Got them for $90! Here they are:

http://therobbcollec...s.blogspot.com/




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