What does more power do for Magnepans?

El,

No, it is a digital multi-meter. Just slow to react. Less than $10 at RS.

To do total amp output I would have to undo the active biamp setup and reinstall the passive crossovers in the 1.6's. And get better measuring equipment! Your early results and postings gave me enough motivation to check the seperate panels driven by seperate amps. It was mostly just general curiosity.

But, I got a lot out of the little experiment. Learned a small fraction of electronics theory, its pratical application, and why there is so much potential in a vertical biamp setup with the Arcam/1.6 combo. Clearly, dividing the 2x+ current draw of the low frequency panels between the power supplies of a pair of 2 channel amps instead of using a single 2 channel amp and its power supply for the low frequencies has a great benefit potential. I think there is the potential for added IM distortion when running HF and LF through the same transformer in a vertical setup. We will see if I can hear it.

Here in Cincinnati, we are rained in today. Guess what I am going to do today. Go Vertical!

Then I got to quit fussing around with electronics and make some room treatments!

Jim S.

Jim, I am unfamiliar with Maggies and I did not quite follow your measurement scenario so maybe I am missing something. But I did learn a lesson the hard way on my speakers. Adding a second amplifier (identical to the first) did not double the available power. I did gain the benefits of going to an active crossover vs a passive crossover but the small power gain was pretty much the result of the crossover type change, not the extra horsepower up front. And maybe there was no power gain at all and it was just the change in presentation from the crossover change. Anyway, the failure to increase power was a major surprise and disappointment but an excellent learning experience.

Consider this for a two-way speaker (considering one channel at a time). One amplifier sees the combined impedance of two drivers in parallel. That combined impedance is less than the impedance of the highest impedance driver. The amplifier will have a certain output into that impedance.

Add a second amplifier identical to the first. Each amplifier channel will see the impedance of a single driver. That impedance will be higher than two drivers in parallel and the amplifier output will be diminished.

If I got this wrong I would appreciate a gentle education. Those few members who continually post negative and critical comments need not respond.

Don_s...In a 2-way speaker system of,say, 8 ohms, each of the drivers will be 8 ohms. True, the drivers are in parallel, but because of the crossover the power amp "sees" the woofer alone at low frequency, and the tweeter alone at high frequency, so the overall impedance remains 8 ohms.

Biamping does increase the effective power of the amp. If you do not biamp the HF signal is riding on (superimposed on) the LF signal. The peak signal, which is what may cause the amp to distort, will be the sum of the two, If you biamp properly using an electronic crossover, each amp has only the HF or LF to deliver. The HF, for example, starts from zero, rather than where the LF signal is, and therefore has further to go before distortion results.

This power gain was important back in the days when 20 watt amps were the rule, but today it is simpler to just get a bigger amp. Also, in the old days, intermodulation distortion (which occurs when a HF and a LF are amplified together) was typically 1 percent or higher, and biamping helped. But today's amps have lower IM.

Today biamping remains useful, and almost universally used, for the subwoofer/main speaker crossover, because the inductors and capacitors needed for frequencies below 100 Hz are large and very expensive. The only advantage of biamping the main speaker is to avoid the passive crossover. Makes you wonder why some people simply hook up two amps without using an electronic crossover, and bypassing the built-in passive crossover.

El,

Thanks. More coherent than I could of posted to Dan's question.

Dan... I went to active biamping for a couple of reasons. The 1.6's are reputed to benefit greatly from better crossover parts. My little Arcam Alpha 10's are 100w/8ohms 170w/4ohms and theoretically a little short of wattage at SPL levels I occasionally listen at. A Bryston 10B came up used at a good price, so let’s kill 2 birds with 1 stone. Improve the crossover with the Bryston (bypassing the stock) and get the best I can out of the little Arcams with active biamping.

After the change, it became obvious that I had been straining the amps through the stock crossovers. Clarity and control were immediately present and at much higher SPL’s. There is some reading available on the theory. I don’t really have a good enough grasp on the basics to completely understand all of the principals. In case you want to read it.

http://sound.westhost.com/biamp-vs-passive.htm
http://www.passlabs.com/products.htm (XVR1 manual)

Now the bad news... all those new and old pop/rock CD’s that I used to love so loud... well some of them aren’t so great when you can actually hear what is going on in the recording.

BTW – I made the change to a vertical biamp yesterday. It made a tremendous difference in presentation. Don’t know what to make of it yet.

Jim S.

Jim S wrote:
I made the change to a vertical biamp yesterday. It made a tremendous difference in presentation. Don’t know what to make of it yet.

--
Your results mirror mine. Vertical bi-amping rules! Or at least it's really different, and maybe better... Jury is still out.

I've been playing around with vertical bi-amping my Maggie 1.6's for the last month as well. Previously, I was horizontally bi-amping with an Innersound ESL-II at 600wpc into 4 ohms powering the bass panels and a McShane-modded 70wpc HK Citation II on the treble panels. I had carefully level-adjusted the two amps, using a RTA analyzer with a calibrated microphone, using a sweep generator to make sure the sound output was even across the frequency spectrum in my listening room, measured from my listening chair.

Even though I use an electronic crossover, I was concerned that I might be hearing phase anomalies with the mix of the two different amps. So I built a new modded Citation to match the first one. These tube amps have HUGE power transformers that will pass a clean 70kHz signal, very high quality! They seem to have enough power to do a credible job with the Maggies, especially since the amp outputs are connected directly to the drivers, with no inductors or capacitors in the signal path to soak up power.

Of course, 70 watts on each bass panel driver isn't all that compelling with Maggies, so I've also recently inserted a high-pass filter on the bass amps to cut off frequencies below 80Hz, which are handled by a pair of subwoofers. The amps seem to be quite happy with this load.

Gains: much more coherent image, but a somewhat thinner sound overall. Acoustic recordings and female vocalists are clearly more accurately reproduced. Piano is especially much more realistic.

Losses: I miss the iron grip that the Innersound had on the bass panels. I never used to feel the need for a subwoofer, but now it's mandatory, and the bass overall is a bit wooly, especially things like timpani.

Overall, I think vertical bi-amping with matched stereo amps has real potential with these speakers. However, if you want to do it with tubes, you face certain compromises in terms of full dynamics, or you need to spend megabucks for high-output tube amps. It seems silly to spend huge amounts for VTL-750's or whatever, but I think the resulting sound would be worth it! I haven't yet found a sand amp I like nearly as well on the mid/highs, but that certainly is next on my list to explore.

I'd be interested to hear your impressions after extended listening with your setup.

Dfhaleycko,

I will post impressions, but I think it would be better if I let Pal have his thread back and post to my system.

I haven't had a chance to sit down and listen for long periods. Too much work!!! I didn't expect a huge difference between horizontal and vertical with "identical" 2 channel amps (maybe not so "identical" after all). Just a little bit of extra headroom. But the presentation is different. Some talk of letting a system settle after changes. I am beginning to wonder if that isn't part of the difference.

I am going to run RTA when I get a chance and see if it measures slightly different. Will post the results.

Jim S.