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In the Forum: Audio Discussions
In the Thread: The loudspeakers for a powerful SET

Post Subject: Going Through PhasesPosted by Paul S on: 6/18/2010

Crossovers are so annoying, about impossible to nail down, and it's almost as though the more you study the problem, the fuzzier the "answer" gets.

For now, I would like to more or less forget about "phase" considerations, partly in order to get this thing rolling, and partly because I believe there is no perfect solution, in any case. I expect to make final decisions with my ears; I just hope I can get close enough to the XO points and lap curves I aim for to be able to reasonably evaluate the results by listening.

While I would still like to increase overall speaker efficiency, it's tougher than it looks at first. Part of the connundrum is that although additional drivers and channels raise the efficiency on paper, in fact the amp is further compromised by the added burden of all the added networking and feedback. Not to mention the "slice and dice" issues... I don't know if this makes "expanding" a wash, but I was thinking that for the present I'll just try to shift the frequencies around some while reducing XO parts count, and I'll see how that works to accomplish +/- the same things. I'll say more about LF to close, but generally speaking, one has a much easier path to hack if one simply lets go of real FR, going in.

Regarding the mid-top spectrum, a while back Yoshi sent me some Reps drivers that he had "castrated" by cutting off their whizzers. As it happens, I have been targeting the whizzers on my Lowther DX4s for a while and I am pretty sure that I could do better for that part of the frequency range. Simply put, I plan to sub the de-whizzered Reps for the DX4s and run the Audaphon ribbon down a little. I'll keep the lower notch filter I used for the DX4s for the nonce, and I'll just let the Reps run out of HF steam on their own, hoping they will meet the ribbons 1/2 way near 6.5k Hz. Yes, this violates my own ">8k Hz Ribbon Rule", but not by much, and so what? More on the XO changes, anon.

Regarding the low-mid spectrum, I mentioned in another post that my 15" Audax woofers were short on tone over about 125 Hz. Taking a harder look at this (ie, actually looking...), it's no wonder, since they are presently burdened with a very complex 3rd order XO at 100 Hz! I will run them up and I will run the Rep's high pass XO up to a 1st order 450 Hz from the DX4's present 2nd order 150 Hz high pass.

The aim here is to add weight to balance, gain better high-SPL-upper-mid clarity and balance, and make a more direct connection with the ML2s. If I wind up with "real", "spiky" "treble", I will be stoked! This will not address LF, of course. In the context of this thread, I apologize, but I am resigned that true LF will take more amps and more boxes. Present "LF" target is -3 dB @ 40 HZ with no help from the room; ie, business as usual.

Paul S

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