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trioid

Cornwall K33 question

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Hi All

Here is the situation, and then the question. Sorry for the details, but if someone out there is willing to help guide my thoughts, you will need to know the setup.

This music system here is all ‘tube powered’ except for the CD player. The speakers are Cornwall IIIs and they are assisted by a pair of SVS subwoofers. I currently use a DEQ2496 only for ‘tuning’ the subwoofers -- the higher frequencies go direct from the preamp to the main amps. The preamp has a second output pair that goes to the DEQ. The DEQ output right now goes to a Paradigm X-30 active X-over that is used only as a low pass filter. That works just fine, as my room is somewhat flat from 100 to 20K Hz (I have measured it). Below that, the DEQ boosts from 0 to a max of +8 dB over the range of 100 to 20 Hz.

Nonetheless being an audio nut case, I want to try out using the DEQ full range (after modifications*). The DEQ would go between the preamp and main amps. However, I don’t want to use the high pass on the Paradigm X-30 to go into the main amps – i just don’t like it. What I would like to try is running the pre amp to the DEQ then the output of the DEQ split to go direct to the main amp and through the active X over for the subs. The plan at this time is to more or less leave the equalizer settings I have below 100 Hz, and use the DEQ full range (let it auto equalize above 100 Hz only for room correction). With this setup, the Cornwalls are still getting the full range input.

Soooo, here is the question for you experts (and I hope it is not too stupid!). Will I over drive the K33 woofers? They would now be seeing as much as an extra + 6 dB at 20 Hz, for example. Up to this point, I have not had any problems running full range to them, and the system sounds rather good, if I do say so myself. Just as a reference, I listen at or below ~ 90 dB at 10 ft away Anyone??

* Mods to the DEQ (no plan to run digital in or out) – new input op amps, direct out from the DAC to capacitors (avoiding all output op amps and related circuitry)

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This got me to looking at excusion limits for CW. That requires modeling, etc. That is not completed.

Nonetheless. Classic wisdom is that vented speakers like the CW have a problem. It is that at freqs below the box resonance (about 36 Hz for all CW's) the woofer is not mechanically restrained by the box acoustic load. It is also true that acoustic efficency is falling off rapidly.

This means that freqs below the box resonance can drive the speaker to its mechanical limits and it will bottom out, sometimes making a clanking noise as the driver is being distroyed.

In the old days, recordings did not have content down there. And few people were cranking up the power in that range. So the CW would not be challenged.

Things have changed. Digital music does have content down there -- which can be impressive if your system has the capability -- especially sound tracks with explosions and effects.

Further, people use an equalizer to goose up the power. This is very bad because it is throwing power into the speaker at a point where it is close to death.

I do think you have something to worry about.

Wm McD

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Wm - Thank you!

That is exactly what I was wondering about. I think I need to reconsider all of this. In particular, looking for a really good active crossover. Anyone have a suggestion? Behringer has one, but one would have to modify (upgrade components) in that circuit as well, in my opinion.

Cheers, Jim

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In particular, looking for a really good active crossover. Anyone have a suggestion?

Here is one that I think will not dissappoint (2-in, 6-out). Rudy81 has at least one of these tri-amping his Khorns in his HT, and I think that he got a fairly good price on it (although probably not quite as low as the Behringer price). However, I haven't heard them and I haven't heard back from Rudy since he tuned it up.

I have a couple of Dx38s (2-in,4-out) and they are superb. These are the units that most use for their Jubilee two-ways when they are using active crossovers, and are the units that Roy Delgado (Klipsch) uses to develop Jubilee crossover/EQ files when they place the Jubilee in the anechoic chamber.

Here is a Mcintosh$$ MEN220 active crossover that is brand new to the market. It is a 2-in, 4-out design. One guy here (Mark1101) that I know has this one, and likes it a lot. He is running a K402(with TAD TD-4002 drivers) and MWM two-way system. I bet it sounds effortless and clean.

There is also a Yamaha SP2060 processor, although I don't have a good reference for that one. I heard this one vs. the Dx38 last fall on a Jubilee 2-way. It sounded pretty good to me.

Chris

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Hi Chris:

Interesting, and thank you for the inputs and handy links! Plenty to think over here, since with the Cornwall III, I can easily 'biamp' properly given a good Xover. The multiple outs allow the sub it's own range as well.

Later, Jim

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