Sloped baffle

Bombaywalla, the DEQX is not plug and play. The correction requires separate measurements of the drivers and the room. Generating the appropriate corrections is not a trivial matter. For me, having the distributor come to my home to do the installation was the only way to go, but some do it themselves. Once a year or so, we will meet up in a remote session over the internet to remeasure and tweak the curves.

Levinskih01, the volume control is superb, although it does not have as many steps as my ARC preamp. One nice thing is that I can keep the ARC at its optimal volume level and do the volume adjustments with the DEXQ. For digital sources, I bypass the preamp. Although some tube richness is lost, I want to get the maximum resolution possible from the digital source. With an analogue source I slightly prefer having the tube preamp before the DEQX, but I don't consider it essential.

Hello to all,

I am happy to answer some questions on design. Before that, I need everyone to truly understand the simple difference between the definitions of phase and time coherence.

Please open that earlier link to my illustration, and study the differences between waves combining. Then consider the following:

1) Time coherence-
Send the speaker a 'beep' near the crossover frequency between mid and tweeter.
Unplug the mid.
The beep coming from just the tweeter arrives at the ear 'X' milliseconds after the signal left the tweeter.
Now, turn on the mid; unplug the tweeter.
If the beep from the mid arrives at THAT SAME INSTANT, the mid and tweeter outputs are TIME COHERENT at that one frequency (perhaps not at others).

2) Phase coherence-
The mid's beep arrives at least one FULL cycle later than the tweeter's. Thus, their peaks and valleys still line up, making the two drivers IN PHASE. Yet they are not time coherent since the two beeps' beginnings and endings did not line up.
Any decent speaker is PHASE COHERENT. If not, cancellations occur at its crossover points. To market that a speaker is 'phase coherent' or 'phase linear' is only a 'feel good', to impress those who know little of speaker design.

Referring to my illustration, note that a time-coherent speaker is automatically phase coherent. It is redundant to write that a speaker is "time- and phase-coherent."

A speaker that is 'phase coherent' or 'linear phase' you can bet is not time coherent. Several speakers companies claim to make time coherent designs, but Stereophile tests reveal those claims to be completely false.

By the way, metal dome tweeters are no lighter than soft-dome tweeters. Visit Madisound.com to examine the specs of the best tweeters for yourself.

There are other misunderstandings I would like to address, but first, everyone must have a clear understanding of what IN PHASE means versus what TIME COHERENT means (hint- the latter always involves a stopwatch). For your own edification, I strongly suggest all of you discuss some examples such as:


Two cars traveling along the highway, one always fifty feet behind the other. As they travel, their RELATIVE phase is UNCHANGING (their phase relationship remains CONSTANT).

Two cars start off at the same instant, and travel along side by side. They are again in phase, since their relative positions are unchanging, and they are also now time-coherent.

===========

Two bicyclists crank their pedals at the same RPM, in the same gear. Thus, they travel at the same speed.

But notice when one rider's pedals are UP and DOWN, the other rider's are always in some other position. Because both riders' RPMs are staying constant, the pedals' RELATIVE PHASE remains constant. But these two sets of pedals are not "IN PHASE" with each other, since their peaks and valleys (their ups and downs) are not happening at the same time.


Time coherence, at its most fundamental, is about beginnings and endings lining up. Phase is only about peaks and valleys of any REPETITIVE cycles lining up. Music has BOTH characteristics.

Hope this helps.
Best,
Roy
Green Mountain Audio

Thanks Roy. For those of us time and phase dummies who have already invested in expensive gear, and who are confounded by the difficulties associated with meaningfully auditioning speakers, what are your thoughts about using the DEQX unit to unscramble the time coherence egg?

As an fyi, which I may have mentioned in this thread or elsewhere, I auditioned a pair of Vandies and another speaker (Brand X). All conditions were held constant. Notably, the amp was the same model as my former amp. I struggled to get happy with the Vandy Treos. Spent close to 90 minutes with them. Played all kinds of music. Moved my listening chair forward, backwards, sideways. Even listened backwards. :)

I was getting ready to walkout and the dealer offered to compare another speaker that is similar to mine. Same set up, amp, etc. Brand X ate the Vandy's lunch. It wasn't even close.

Maybe I like sonic swill??? Dunno

Back to my Q: Any thoughts or comments about the DEQX??

Thanks Roy. Again, you beeped. I'll counter with pop, bang, whack, pow, and all the other 60's Batman fight words that seem to have something else in common. Not arguing you're goal of recreating as accurately as possible but the words describe multiple, changing tones that appear to define our hearing ability more than the actual sound. So, my rhetorical question becomes: Is the b and p really in beep or is that our imagination?

Hi Roy, thanks for coming back. Your contributions are most welcome.
I have few questions for you.
Could you explain the pros and cons of making a speaker time coherent either by analog/digital/active/passive means?
If one were to use digital eq that only deals with room considerations and not speaker refinement, would there be a chance (and if so how much) of altering the time coherence of speakers such as yours?
The late John Dunlavy seemed to be somewhat unique (there might be another but for the life of me I can't remember the name of the manufacturer that was once a regular contributor here) in that he used W M T M W driver, as well as down firing woofer configurations. He told me that because of his previous experience in military antenna array technology he had more experience than most in wave propagation technology. Others who tout their speakers as time coherent seem to stick with more traditional W M T arrays. Is this due to size and marketing considerations, or something else?
Though most manufactures of speakers designed for time coherence seem to make fairly similar placement suggestions, they do vary a bit, from equi-T, to equilateral triangle, to wider than near, etc.. Why would that be?
It would seem to me that ideally a speaker designed for time coherence would have a sealed box, yet none of your current offerings seem to be designed that way. Am I wrong? If not, why aren't they?