1 plus 1-S, Various, difference between MK121-C and MK141-C?

Read more on the Acoustat 1 plus 1-S in our home audio section

Jim2004-02-23 22:21

Andy, I was referred to you as the one to answer this question. I am considering one of these two speakers. The Acoustat 1+1 MK 121-C and the 1+1s MK141-C. I understand that the 1+1 has a low frequency that is not in the other but, which one would be preferable to own. One having the built-in sub or the one without. Is there any advantage to the 1+1s? Please advise, Jim


Andy Szabo2004-02-23 22:21

The Acoustat Model 1+1 is available in two different versions. The much more common version, using the full-range MK-121 interface, is an ESL with no woofer(s). The 1+1 ”S” version, using the limited-frequency-range MK-141 interface, is an ESL mated with a common-mode woofer system. In this model, the ESL plays down to about 100 Hz, at which point the woofer system takes over. Both systems use the same ESL panels.

The full range, (MK-121) 1+1 is a bit shy on deep bass response. This may not be an issue, depending on the type and volume of music that you like. The bass signals it does reproduce are quite accurate and natural sounding.

The hybrid (MK-141) 1+1 ”S” has deeper, stronger bass response, thanks to the inclusion of the woofer system. However, the quality of the bass sound is not equal to the quality of sound obtained from the ESL portion of the speaker. The woofer itself is not all that great, and the woofer/ESL crossover could have been done better. This model was produced for only a short time in limited quantities, whereas the full-range 1+1 was produced for many years, and remains very popular even today. In concept, the 1+1 ”S” was a good idea, but its implementation was lacking. To date, over a hundred Acoustat questions have been posted on this site, and yet this is the first one concerning the 1+1”S”. That should tell you something!

My recommendation would be to buy the full range (MK-121) version of the 1+1. This will offer you several advantages. 1) You can listen to the speaker as a full range ESL if you so desire (and many people do). 2) You can always add a good quality subwoofer to the system if you like, crossed over at 80-100 Hz.

With the hybrid (MK-141) 1+1 ”S”, you are essentially stuck with the supplied woofer system. There is no way to convert the MK-141 interface to full range operation.

Michel Keinan2007-04-25 16:42

i want more information if you can send me male please

Mark F2010-08-01 05:17

Andy, I think I have a MK-131B 1+1s. Currently it sounds better without the sub. What in the frequency response of the panels? I'm thinking of getting two subs to supplement the panels. Are there any that anyone suggests? Or would I be better off waiting for a full range 1+1? Finally, if I can find a MK-121 transformer, would that do the trick?

Andy Szabo2010-08-01 16:55

The Acoustat MODEL 1+1S did use the limited frequency range MK-131 interface with a woofer module. The woofer, even in its original condition, was the weakest part of the system. Now, many years later, most of those woofers have suffered from surround-rot, so they either don't work or have been replaced with another woofer that may or may not be an improvement. So, upgrading your system is a good idea.

The panels in the 1+1 and the 1+1S are identical. Changing the interfaces to MK-121's would convert your speakers into full range Model 1+1. But that will depend on being able to find those interfaces, and they might be pretty expensive. And depending on your musical tastes, room characteristics, etc., you may find even the full-range 1+1 a little bass shy.

Adding a self-powered woofer system(or two) is probably your best bet. Most of them have variable frequency/phase/level controls, so it's relatively easy to dial-in the transition between main speakers and woofer. Many models are available, over a huge range in price. For my Spectra 4400's, I use an inexpensive 10" Dayton Audio unit, and even though I recognize that much better units are available, its addition to my system was a positive gain, and it has never done anything that detracted from my enjoyment of the music. The Dayton units are available from www.partsexpress.com, along with other sizes of woofer systems. Of course, if you have a big tax refund burning a hole in your pocket, models from Velodyne, REL or JL Audio would be even nicer.

By the way, if you go with self-powered woofers, I would recommend running the main speakers directly from your amplifier, rather than sending the line-level signal through the woofer's high-pass circuit first. The MK-131 will already roll-off the signal.

Andrew Sterling2015-10-09 10:18

Andy would you say the mk 131 B frequency response is 100 to 20,000k?

Andy Szabo2015-10-09 23:57

I am not sure of the exact operating range of the MK-131, as that interface was phased-out before I joined Acoustat. However, I think 100 Hz may be a little on the low side. It may be more like 150 Hz, or possibly as high as 250 Hz. Since it was used primarily with the Modular Hybrid (MH) Series, using one woofer per speaker (as opposed to a single common-mode woofer) one can get away with a little higher xover point without degrading imaging. Best to experiment with the woofer's crossover point if you are planning to use one with a MK-131-equipped speaker.

Andrew Sterling2015-10-10 01:03

Thanks Andy I was thinking along the same thoughts.
I also have a pair of MK 121 C medalion which are fabulous. Did a few things such as replaced the high frequency electrolytic with a Jensen film 56 uf vap. FOR THE High end. Bypassed the speaker fuse and replaced the slider pot with fixed s Vishay 14 & 2 ohm resitors. My amp is the Hafler HD 500 however it's been extremelymodified by Musical Concepts with ultra high end front end boards. 2 dual 500 watt ea. toroidal transformers for dualo mono. 156,000 uf power caps total. Also running 2 - 350 watt 12 inch sub woofers down firing rolled off at 60 hz.

Can you think of any other mods I can do to the 121 medalion ?
Andrew Sterling

Andrew Sterling2015-10-10 01:09

Andy almost forgot replaced on the MK 121 MEDALION all the diodes and 3000volt caps with 6000v. Caps. Sinatra images straight down the middle . Love this set up more than the 2+2 I use to have.

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