Bi-Amp 3.5 Way Speakers

[slhijb]

Want to bi-amp my new diy 3.5 way speakers using my Marchand XM-9 two-way electronic Xover. High-pass filter will use an OTL amp to the tweets & mids (which use a passive Xover) and low-pass a SS amp to the woofers, which are crossed at 80Hz. The purpose is to bi-amp keeping the high-pass signal as simple and transparent as possible to the existing passive high-pass Xovers.

To accomplish this I’m thinking of completely bypassing the high-pass circuitry in the XM-9 by sending the high-pass signal directly from the input RCAs to the high-pass output RCAs in the XM-9. As I see it, this results in a high quality subwoofer. Good idea? Recommendations?

[slhijb]

Anyone please? Just want to make sure I'm not missing something. The fewer components in the signal path the better and since the tweeter and mid already have a good passive Xover, bypassing the high pass circuitry on my active 2-way Xover seems like an obvious and good idea. Am I right?

Marchand XM9 Schematic:
http://www.marchandelec.com/ftp/xm9man.pdf

Thanks!

[PeteMcK]

If I understand you correctly, you should be using the connections as shown in the top diagram on p13 of the Marchant pdf, with the crossover freq set to whatever current mid to woofer xover freq is (which should be higher than 80Hz for a 3.5 way), and the passive parts for that removed.
The Lo output will go to the amp driving your woofer and .5 woofer.
If you bypass the HP filter, you will send a full range signal to the mid/tweeters, negating any benefit of having the filter there in the first place.
However, you have clouded the issue by mentioning a subwoofer...
Re. "The fewer components in the signal path the better" - too few is probably worse than too many...

[tinitus]

Hard to say, it may work or it may not work as perfect as you hope...sorry, but I think its pretty much unpredictable
Bi-amping doesnt appear to be as straight forward as one would expect
Tried it twice, with little luck
Dont know why it didnt work, but suspect something with ground interaction in passive xo, among other things like different amps
Well, bi-amp didnt actually sound much different from using just one amp
The major problem appeared to be a phase issue

[PeteMcK]

Tinitus, If you have a high power amp and don't listen too loud, I think you may not notice too much difference. I use 40W amps, and even though I don't play too loud, bi-amped sounds better to me, and judicious choice of xover slope and freq allows me to do BSC as well, simply by tweaking the woofer volume. I'm using 1st order line level passive at 200Hz.
Can you describe your phase issue in more detail? What order was the passive you were replacing?

slhijb, if you want fewer components in your signal path, line level passive 1st order has only 4/channel...

[infinia]

Originally posted by slhijb
Good idea? Recommendations?

Hi
I think it's important to keep the High Pass filter to limit the mids from LF content which has many benefits to lower distortion already.
But you could bypass the XM_9 HPF function and get the function back by modifying/adding the mid/tweet amps in/out coupling caps.

[sreten]

Hi,

To bi-amp a 3.5 way you need to turn it into a 3 way, BSC by EQ.
Consequently the required active c/o functions are complex, they
will need to include EQ to arrive at the required acoustic targets.

How do you get a 3.5way crossed at 80Hz ?????

/sreten.

[tinitus]

Originally posted by PeteMcK
Tinitus, can you describe your phase issue in more detail? What order was the passive you were replacing?

I was not doing active, only plain bi-amp, so I didnt make any changes to xo
Dont know why there was phase problems, other than my suspicion is that in a well balanced xo there may exist some interaction within the passive xo...impedance maybe?

[PeteMcK]

Re:"I didnt make any changes to xo",
umm, you did remove the original speaker level passive xover, right?

[tinitus]

Originally posted by PeteMcK
you did remove the original speaker level passive xover, right?

Do you mean attenuation L-pads ?
no I didnt change a thing
And to be honest, I didnt spend much time with the bi-amping as it didnt present any improvement
But I suppose that with a little more effort I could have made it work

But my future 3way with pro drivers WILL be biamped but it will start out as bi-amped, which I hope will make the difference