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In Reply to: RE: Bi-Amping - Horizontal and Vertical posted by Lifer on October 02, 2016 at 16:41:02
Hi Lifer,
Interesting way to bi-amp, I'm glad you like the results so much. I'm curious why you chose to use a low pass filter. As I read your post, the woofer's original low pass filter is still in place, or am I mistaken?
If so, there are a couple of considerations:
- If you use an active high pass filter before the tube amps you greatly improve the dynamic range of that amp, since you are removing the largest part of the voltage swing which is always in the bass. Of course, not having the woofers in the circuit gets you some improvement by reducing the current draw, but the voltage swing remains. This may help stiffen up the amp.
- If you use no active filters at all you would maintain the original phase matching between woofer and mid/tweeter. By adding another crossover layer in addition to the woofer's low-pass you are probably getting a 6th to 8th order crossover instead of the original 2nd to 4th. Or am I misunderstanding that the woofer had no such filter?
If in doubt, I strongly encourage you to look into Room EQ Wizard or OmniMic to get detailed measurements of each section and examine the crossover region in detail.
Best,
Erik
Follow Ups:
Ok, I am a bit confused (better than my normal state), since I am not using the active crossover for the upper module I can't see how I am effecting the crossover to it. I am only using the active low pass because I need to limit the signal going to the bass module or else it trys to play it all and sounds awful.
The upper modules were sold separately and many people play them without the bass module so I think my approach is reasonable. If I sound defensive, please disregard.
I think we're all a little confused. :)
What's the "normal" hook up of the bass modules? Is there a passive low pass filter involved?
Best,
Erik
You will find that there is a low-pass filter for the Base Module but with the OP's items it's inside the Base Module and not in an external box.
The real flaw in the EOS design is that the main module is tuned to 40hz by a port but there is no HP filter to the main module.
So the design is prone to excursion overload below the port frequency, by high level (full power -3db) low bass (below 40 Hz signals going to the main module. Adding to this problem is the low sensitivity of the design.
You can either
i) fix that problem somewhere in the wide band-pass between the two modules and go with active low-pass alone, in the existing band-pass between the two modules. Plus a line-level passive HP to the amps driving the main module, 1st or 2nd order is doable.
(Because the MM is time & phase coherent, I think a 1st order PLL feeding the Main Module amps would retain more of its designed in impulse response. The response would cascade to 5th and cone bounce would fall enough to help.) OR
ii) get rid of the existing passive LP xover that is inside the Base Module and actively bi-amp 4LR at say 70 Hz. System headroom would increase even more dues to the higher xover.
Adding a 20Hz HP filter would avoid overloading the Base Module. There's a 40Hz subsonic add-on in the DBX xover which 'might' be convertible to 20Hz. Which would give even more headroom.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
You will find that there is a low-pass filter for the Base Module but with the OP's items it's inside the Base Module and not in an external box.
The real flaw in the EOS design is that the main module is tuned to 40hz by a port but there is no HP filter to the main module.
So the design is prone to excursion overload below the port frequency, by high level (full power -3db) low bass (below 40 Hz signals going to the main module. Adding to this problem is the low sensitivity of the design.
Not a simple active bi-amping proposition.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Thanks for your input to this thread. I agree with you.
Please review my response to Lifer.
I think I've got it right, but I have missed a few errors, etc.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
The 50:50 point is about 350hz.
Too much is never enough
Too much??
Forget my tag line. I don't customize it per post.
My point is that the power even split point for 'normal' music is about 350hz. Power needed falls OFf as a percentage of total BELOW and ABOVE that point. I'd say, however, in NO CASE to have less than maybe 20% of power in the bass end, regardless of crossover.
My panels cross at 600hz. And low-cut about 60hz. So, I don't feel TOO BAD having 2x200 per panel. ONE stereo amp per speaker. My Parasound A23 do well. And since I never redline it, I have NO idea which amp would give up first, the HF side or the LF side. The sub is another 250 or so and crosses about 45hz and is in no danger of running out of power.
Gain match of amps is very important with 2 different amps per speaker. I'd be tempted to work out a DLP solution which can make up for such differences.
Too much is never enough
My advice, from TomServo - the professional horn guy just this year, was to use asymmetric slopes at 150Hz. It was nice to have my own decision to do exactly that confirmed.
And I was planning to, for my QUAD 63s with a SWARM of omni/box subs. I did not want to run my subs above that point.
I will be using 3rd for Low Pass, plus 1/3rd octave Eq.This makes it easier for me to get the wring / phasing right.
The just will be complex, given that I will be switching for absolute polarity at spkr level, driving two big, sealed, DIY, clam-shell drivers, sealed subs (half-built) with a stereo power amp each, running OOPhase. A stereo integrated will drive two tall DIY TL subs using gifted KEF B139s.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
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