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Perhaps that is why I find the adjustment of frequency (now at 70 HZ) and the .. adjustments .. very finicky"

Posted by Timbo in Oz (A) on October 3, 2016 at 23:16:57

In Reply to: Bi-Amping - Horizontal and Vertical posted by Lifer on October 2, 2016 at 16:41:02:

Dear Lifer,

This is a quite long response, but I do hope you will read it. It took me most of an afternoon. Please feel free to get back to me and ask questions. You will also need to read the review referenced below.

At the outset I note that the EOS design needs a good deal of power.

From my reading you may have cascaded a 4th order active 70Hz HP/LP filter with the original design's own HP/LP filters designed for the same purpose, and which likely operate between 55 up to above 70Hz, and not symmetrically around 70Hz as your insertion of the DBX active xover assumes.

If I am correct you have added a 4th order HP active filter to a 4th order acoustic filter (the upper module's reflex port) and have a steep 8th order acoustic high-pass slope which does not meet or match the acoustic low-pass slope, which might be 5th order or even 8th. That is, there's a notch in the sound you hear but not a room-cancellation dip. This fits with 'finickiness.'

If that is the case I would not be at all surprised that you have found the adjustments with an added 4LR xover difficult or finicky. Especially if the original HP/LP crossover was not set to 70Hz, as I suspect. Yes, real-world passive HP/LP spkr filter pairings often have a wide pass-band.

If the slopes / pass-band are anything like those reported by Stereophile in a review of the EOS Signature (click below) you have likely damaged the intended sound.

In other words? I think erik-sq is likely to be absolutely right! And, you may well be better off doing it all passively with the original crossovers. But wait, there's more further down.

Even if you have bypassed the Base Module's crossover/s, IE including any High-Pass elements - that does not of itself guarantee that you will get the full benefits of high SS power in the bass - without damaging the overall coherence of the sound as intended by EOS.

So, why do I think that?

i) In the review linked below it is stated that the Base Module's HP slope rolls off slowly above 70Hz (IE not at 4LR) and that the Base Module covers the band-pass 25Hz to 55hz. It seems likely to me that EOS may have done the same thing as they did with the two-way module's crossover's and arranged slopes that will help fill in for the distances between the bass driver below in the Base Module, and the smaller one in the main module.

ii) IIRC this model was an attempt at time and phase coherency by EOS, at least for the upper module. Noting that any high-pass filter that EOS applied to the upper module - to integrate it with the Base Module's sound - would need to be first-order _electrical_ only, so as not to affect the performance of the whole design. ? Ask if you like? You have put in a 4LR high pass which, if I am right, is unnecessary and may damage the time/phase coherence EOS may have been aiming for.

iii) As the 2-way upper module is itself a reflex box, it thus already has its own low-pass but acoustic filter (the port) cascading the acoustic output to 4th order, so EOS probably did NOT add any HP filtering. Addendum? "But as KR stated, there is no high-pass filter in the Eos Signature's feed" referring to the main / 2-way module.

So EOS have 'designed by listening' just a single and likley shallow 'low-pass-only' filter for the Base Module's feed.

You could of course return to the original design's intent if you were to use only the original passive crossover's for the Base Module and the 2-way module that sits on it and, passively bi-amp horisontally. I think you should try this, soon, anyway. But, see below first about gain matching.

The power losses involved would likely cost you the same number of db per amplifiers, less than <3db for both modules.

IF however you do really want the full benefit of maximising the power available from using an active xover, AND without losing EOS's intended integrated and coherent sound, which I am guessing you have managed to do.

Well, the only reliable way to do that is to get someone to measure the transfer function of the passive filters as used by EOS to integrate the Base Module to the upper module. And then, build those /that as active line-level filters.

It will likley be just a pair of LP filters.

I would retain any inductance-rise-eq that EOS has soldered across the larger driver's terminals in the Base Module and across the smaller bass drivers in the upper or main module. This is so the matching of the bass/base module to the smaller 2-way module is tightly maintained.

I would expect that active crossovers closely matching the transfer function of the OEM passive items would then have audible benefits. It would play louder and likely more detailed and nuanced, even nicer.

But, I am not convinced that this will always be noticeably better than passive bi-amping, with a big SS power amp in the bass. That is, passive horisontal bi-amping.

There is however one slight downside to horisontal passive bi-amping using a big bass power amp. The more powerful bass amp /amps need to be gain-matched to the other stereo pair of amps used for the mids and HF. It is possible that they will match anyway.

But, you can add fixed-cut passive attenuation inside the amp/amps with the most gain, to achieve matching gain. The MFrs of both models should be able to tell you the amps' gains.

The sole benefit of using matching stereo amps to vertically bi-amp, using the OEM passive crossovers is that the amp's gains do match.

I've had a stressful few days, and TMFW&Finance wants help with dinner, so I am done editing and re-reading.

Lifer, I look forward to your response.

Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger

• Artemis-systems-eos-signature-loudspeaker-amp-base-module-me   (Open in New Window)

Edits: 10/03/16 10/03/16 10/03/16

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