Correct tap 2 or 4 Ohm for the 1,7 Ohm curve

[damacman]

And you have the behemoths!

[TWInsall]

When you have speakers with extreme impedance variations below 8 ohms I prefer direct coupled amps. You have the necessary voltages for the normal impedance spectrum and as the impedance drops the voltage stays in relation ship with the other parts of the spectrum keeping the correct voicing for the speaker and being able to put out the correct amount of current to keep things from getting distorted and colored. My speajkers dip to 2.2 ohms at cabinet tuning freq but my 207 handles it perfectly. 7300 and newer amps with autoformers sound bloated and similar to tube amps with tube bloom. Tube bloom is a good thing with. some speakers, but not mine. I really enjoyed the 7200 for a long time when I had a stereo system and bi amping but now that I tri amp and bi- amp with 7 speakers using 12 channels the two 207's do the job perfectly. My speakers are 7 db more efficient so 200+ watts is plenty.

How long are your speaker wires and what is the speaker cable resistance? That might be influencing things, too. What Mac recommends is three runs of 12 or 10 awg between each MC 2K and the speakers.

[TWInsall]

Using two different taps with both feeds mismatched loads is a disaster waiting to happen. Get your self a Direct coupled amp for the woofers that is rated down to 1.5 ohms then using an electronic crossover use the 2K amps for everything else. Just a bigger version of a MC 901. Boulder 3050 at 3000 watts and the Bryston at 1600 watts dosen't always measure as well as a Mac amp, but with those extremely high damping factors you are not going to believe the quality of the bass. So clean and with. enough power should really rattle your teeth. I liked the old Crown Reference series, but they won't be strong enough for you. You are going to want to use a MEN 220 as your electronic crossover and to get the best matching between the two different amps.

I have tom agree the cone area of the new 1.1k woofer is two small, about the same as a 13.5 inch woofer. A pair XR-7 or ML-2 can almost produce more level as they are not ported. XRT 28, 30 with the low distortion woofers easily surpass the 1.1. The JBL DD67000 using the same woofer technology and two 15" woofers that are 7 db more sensitive will really out perform the 1.1 K and both are ported. JBL voicing can be a little forward, too. IF I were in the speaker market it would be Magico S7 for point source speakers and XR 290's for line arrays. I don't need the line arrays to produce more than 112 db at 4ft so needing really big amps would be just a waste. I imagine a 452, 462 or pair of 601's, would be more than adequate.

We all know Mac changed their amp design philosophy when the 352 came along. A MC 501 will more than meet specs delivering more than 500 watts from the 8 ohm tap driving a 4 ohm load, 700 + watts as I remember. Where older Mac amps like the 2500/ 2600 can run 24 hours a day at at 110 % power at the given tap, where the new amps around 33 to 40 % out put will over heat and and shut down with out adequate air circulation and or extra external cooling. Older amps are continuous duty amps the new amps are more capable of handling broader impedance swings requiring more current and of course the have magnitudes less distortion and more signal to noise. The new amps could n't handle driving speakers continuously flashing their power guard lamps 50% of the time like the older amps. But who would want to. Disco owners for one, Rock groups for another and others driving their stacked pairs of ML-4's and XR 19's, and single XR 290's pairs. I have seen 290's take everything a 2600 had to give and ask for more. Can you imagine a 2600 driving a pair of 1052's to zero levels and not having a driver failure. If I hadn't seen it one night for over 4 hours I wouldn't have believed it playing Sheffield and Mobile fidelity records and selected CD's. Charlie Randell took out woofers on 1K 's using a pair of 601's at a show in San Francisco. So treat those new Mac woofers with care.

[Charles]

Originally Posted by TWInsall

Using two different taps with both feeds mismatched loads is a disaster waiting to happen. Get your self a Direct coupled amp for the woofers that is rated down to 1.5 ohms then using an electronic crossover use the 2K amps for everything else. Just a bigger version of a MC 901. Boulder 3050 at 3000 watts and the Bryston at 1600 watts dosen't always measure as well as a Mac amp, but with those extremely high damping factors you are not going to believe the quality of the bass. So clean and with. enough power should really rattle your teeth. I liked the old Crown Reference series, but they won't be strong enough for you. You are going to want to use a MEN 220 as your electronic crossover and to get the best matching between the two different amps.

I have tom agree the cone area of the new 1.1k woofer is two small, about the same as a 13.5 inch woofer. A pair XR-7 or ML-2 can almost produce more level as they are not ported. XRT 28, 30 with the low distortion woofers easily surpass the 1.1. The JBL DD67000 using the same woofer technology and two 15" woofers that are 7 db more sensitive will really out perform the 1.1 K and both are ported. JBL voicing can be a little forward, too. IF I were in the speaker market it would be Magico S7 for point source speakers and XR 290's for line arrays. I don't need the line arrays to produce more than 112 db at 4ft so needing really big amps would be just a waste. I imagine a 452, 462 or pair of 601's, would be more than adequate.

We all know Mac changed their amp design philosophy when the 352 came along. A MC 501 will more than meet specs delivering more than 500 watts from the 8 ohm tap driving a 4 ohm load, 700 + watts as I remember. Where older Mac amps like the 2500/ 2600 can run 24 hours a day at at 110 % power at the given tap, where the new amps around 33 to 40 % out put will over heat and and shut down with out adequate air circulation and or extra external cooling. Older amps are continuous duty amps the new amps are more capable of handling broader impedance swings requiring more current and of course the have magnitudes less distortion and more signal to noise. The new amps could n't handle driving speakers continuously flashing their power guard lamps 50% of the time like the older amps. But who would want to. Disco owners for one, Rock groups for another and others driving their stacked pairs of ML-4's and XR 19's, and single XR 290's pairs. I have seen 290's take everything a 2600 had to give and ask for more. Can you imagine a 2600 driving a pair of 1052's to zero levels and not having a driver failure. If I hadn't seen it one night for over 4 hours I wouldn't have believed it playing Sheffield and Mobile fidelity records and selected CD's. Charlie Randell took out woofers on 1K 's using a pair of 601's at a show in San Francisco. So treat those new Mac woofers with care.

I don't think Mac would agree with you in much of what you say.

[dag johnsen]

Originally Posted by Charles

I don't think Mac would agree with you in much of what you say.

Probably not

[dag johnsen]

Originally Posted by damacman

And you have the behemoths!

Yes I am very lucky to have them!

[rob725]

I've not tried playing reference volume for 4 hours, but have flirted with the red protection lights for a song or two and so far, knock on wood, I've not broken any drivers. I also have run the 1.25 amps at fairly high volume for long periods of continuous use (during break-in) and have never felt them get hot. I would agree though, that if I were outfitting a club, I would go another way; but for my little theater, the 1.25s, 901s, and 1.1s seem up for the job.

[Charles]

Someone sent me a PM about the 2301 who may not be able to receive a PM. When I sent the reply it didn't go through. I checked with Ivan and the issue is not with me.

I think both the 2301 and the 2KW are in need of update. I think the solid cinch binding posts result in significantly better sound because few will bother to tighten binding posts every few days. Also, there needs to be a parts upgrade.

I think the 1.25KW is the best general purpose amp Mac is currently making. A brief digression is necessary.

Years ago I owned Dalquist DQ10's, the improved version with the new woofer and super tweeter. The DQ10 was the first time aligned loudspeaker. It sounded great. It was powerd by a MC275 power amp. Being a young professional I was very busy and could never figure out whether to leave the amp running or not.

So I bought the new MC2100, 105 watts per channel SS Mac amp. Not knowing what it would sound like, I was quite surprised when it sounded much like the MC275. I still remember my impression.

The MC2100 and the 1.25KW are basically the same amp. They have autoformers, taps, and the same basic amplification circuit. I know for a fact that when Mac designed there first SS amps they tried to duplicate the sound of their tubes, hence the autoformers and taps. Also the use of negative feedback in their SS circuit has never wavered.

Mac SS sounds "tubey" for want of a better word" for this reason. The same basic sound signature present in the 2100 is present in the 1.25. If you are looking for classic SS sound, look at Dag, Boulder, or Accuphase. If you are looking for classic tubes look at AR.

Of course there has been massive improvement in parts, transistors, power and current capability, etc. but Mac remains very confident in their technology and their sound both tube and SS.

I'm waiting on the 2.1KW. I think it will be totally competitive with the Relentless or the top Boulder or Constellation. I'm hoping these new products might arise next year.

[TWInsall]

If you use the 2 ohm tap you are reducing the available voltage and current to the rest of the speakers spectrum, effectively reducing the.over all out put level. New Mac amps drive lower impedances better than they did with the century series and the 7000 series, so I would use the 4 ohm tap, too. My woofers measure about 3,2 ohms but have a resonant narrow spot where the impedance dips to 1,6 ohms and my 207 has never had any issues.

[FreddieFerric]

Originally Posted by tom1120s

Bi-wire.

4ohm tap for the bass and 8 ohm tap for the mids/highs. Yes, you can do this plus I bet the speakers will sound better than if you just used the 4 ohm tap for everything.

Those are very capable amps so I think the 4 ohm tap will suffice for the lows.

This is my setup with my Canton's and my MA8000. Works great and sounds great.