[sys1]

Sorry for the double post, dial-up connections suck.

[Val]

That's what I thought, mac.

As I understand it, it is important to point to a basic difference between DEQX speaker correction and room correction. Ideally, speaker correction should be as flat as possible (as I believe is designed into the program); room correction is the one to be modified as per subjective preference.

Val

[ted_b]

Wow, that's quite a User Group document.  Mac or anyone in the DEQX user community, do you know if this kind of user group support is being generated and/or coordinated? I realize that it's still early in DEQX's market awareness, but for some these secondary considerations (dealer support, user community, third party support) can tip the scale.  
Ted_B

[ctviggen]

But how can one perform speaker correction without affecting room correction (and vice versa)?  It seems to me if you modify the speaker response, you modify the room response (and vice versa).  

Putting on my EE cap, the two ways to modify the signal would be in the time domain or the frequency domain.  Using the frequency domain, you could flatten the response.  I'm not sure where time-alignment would be performed.  I doubt you could do that in the frequency domain, but perhaps you could delay frequencies a bit.  

Speaking of this, George, do you note any delay between when you press "play" and when you get sound?  There has to be a delay.

[mac]

I realize that it's still early in DEQX's market awareness, but for some these secondary considerations (dealer support, user community, third party support) can tip the scale.  
Ted_B

There is a DEQX user group that's moderated by the folks at DEQX.  The level of support is 1st rate IMHO.  I think there's also a public DEQX user group but I'm not sure how active it is.

[SWG255]

This question seems to strike at the "philosophical" difference between the TACT and DEQX systems. The TACT seems to rely entirely on correcting the speakers' abberations in the room at the listening position, while DEQX advocates a two-step process where one measures the speakers nearfield to build a speaker correction profile, then one measures at the listening position to obtain a room profile. I have no idea whether TACT's approach or DEQX's approach is better, or even if it matters. I can see that some speakers like dipoles and large arrayed systems might not yield accurate nearfield measurements, thus reducing the effectiveness of the DEQX approach.

This technology will only get better and better as processing power increases for the dollar spent, and the manufacturers and audio customers gain experience with it. Adding in small high-performance digital amplification and this technology makes the idea of really terrific active loudspeakers for relatively little money look very promising.

These are wonderful times to be an audiophile!  

But how can one perform speaker correction without affecting room correction (and vice versa)?  It seems to me if you modify the speaker response, you modify the room response (and vice versa).  

Putting on my EE cap, the two ways to modify the signal would be in the time domain or the frequency domain.  Using the frequency domain, you could flatten the response.  I'm not sure where time-alignment would be performed.  I doubt you could do that in the frequency domain, but perhaps you could delay frequenc ...

[Val]

I have no idea whether TACT's approach or DEQX's approach is better, or even if it matters.

One is better because it involves an extra step that does matter. DEQX's speaker correction optimizes the speaker drivers intrinsic response and the phase and time relationship between drivers beyond anything a passive or active analog crossover can do.

Val

[ctviggen]

Thanks for that information.  I still think that nearfield would be corrupted by room response, but perhaps not as much as at the listening position.  I wish I had the software to test my system, as I'd take the measurements nearfield and at the listening position to see what the differences are.  But still, any change to the response of the speaker would be a change to the room response (if such things can even be distinquished).  I guess you could send a signal for nearfield and measure response very quickly (fractions of a second, before the wave could interact with the room), then let play no sound, then play another sound and measure the response very quickly, etc.  I wouldn't want to be in the same room while that's going on, but it could be possible.

[Val]

I don't know if this is the way DEQX does it, but for measuring frequency response a fast-Fourier transform (basically an impulse) has long been used in order to minimize room response. I know they recommend placing both the speaker and the mic halfway between floor and ceiling.

Val

[ctviggen]

But all an FFT does is take time domain samples and convert them to frequency domain "samples" (i.e., bins).  I don't see how this would get rid of any room interaction.  Or, do you mean that an impulse response is taken, using an FFT?  That might be interesting.  I'll have to review my books on the sections containing the impulse response.  (What I previously described was essentially an impulse response - a very short tone then silence.)

[Val]

ctviggen, I was referring to this:

http://www.stereophile.com/reference/100/index8.html">time domain/frequency domain

Val