[ekovalsky]

Have you noticed a decrease in high-frequency content (Brian says a 6db/octave dropoff above 10kHz), or did you use the adjustability of the tweeter to remove this?

This thread has wandered so far off topic... maybe all this CDWG stuff should be split and put where it belongs.

Since that is the current topic, I have a question.  If the CDWG introduces a 6dB/octave roll off beyond 10khz as BC states, how can that be compensated by potentiating tweeter output with the L-pad ?  This solution is stated on the new & improved VMPS Europe site, along with more obvious and seemingly effective solutions like Behringer, TacT, DEQX, etc.  Increasing the tweeter L-pad level will raise the entire band from about 7khz (or whatever the latest x-over point is) to 20khz by an equal amount, and increase output from 3.5khz to 7khz to a somewhat lesser degree as the tweeter is fed from a second order high pass filter, down about 12dB at half the crossover frequency.  Setting the L-pad so that upper treble is restored, there will be an approximately 3-6dB rise in the lower treble -- not a good thing.

Not correcting this roll off is listed as another option.  While some CDs are definitely recorded a bit on the hot side, introducing a 6dB roll off above 10khz will destroy eliminate any soundstage depth and also take the air and sparkle out of good recordings.  This would be a real shame in a speaker that uses a fine ribbon tweeter.  And, unless the bass is rolled off too, the sound may seem unbalanced.

With my full range speakers, I have found (by playing with various target curves) the best balance and soundstaging with -3dB at 20hz and 20khz.  I am not using correction above 5khz; the speaker's natural response is -3dB at 20khz at about 4m.

[Brian Cheney]

Eric,

You are correct in thinking the level controls will not provide proper CD EQ.  Since it is a characteristic and not just a level issue, it is best addressed actively.

I have not used CD EQ as of yet on my speakers, but will at CES.  It will be switchable in and out so that the effect of CD-type dispersion can be demonstrated.

[ctviggen]

Brian, what type of CD EQ are you using?  I plan on creating a digital room correction system using:

http://drc-fir.sourceforge.net/doc/drc.html

But this will take a while.  In the meantime, I was going to provide no additional EQ.

[Brian Cheney]

I don't want a CD speaker to sound dull to the first-time listener.  This is why I redid the RM 30 and 40 as lower Q bass systems. Psychoacoustically, less bass translates into more trebles.  

I have not changed the level controls on my CDWG equipped speakers so far, and at CES I will use a preamp with pre-pro type tone controls.  I also have a graphic equalizer in reserve, as yet unused.

Room correction will of course do the job while allowing the user to flatten response at the listening position.

[ctviggen]

Personally, I think the benefits of the waveguide far outweigh the detriments.  I think that improving the off-axis response of a speaker is always good.  And providing a constant field, at least within some portion of the front of the speaker, will also be good.  This is essentially one purported benefit of array-type speakers -- increase the field within a certain angular dispersion, thereby limiting room interaction.  And, with my hearing, I don't think I'll miss 6db of treble at 20kHz.  Hell, I don't think I'd miss 10dB of treble at 20kHz.

[warnerwh]

A Behringer DEQ 2496 can do what's needed for little money and all in the digital domain.

[Bob Wilcox]

Brian stated:

I have not changed the level controls on my CDWG equipped speakers so far, and at CES I will use a preamp with pre-pro type tone controls. I also have a graphic equalizer in reserve, as yet unused.

What is the intended long-term VMPS solution to the EQ? Inserting external devices in the signal path often results in signal degradation.

Will new internal crossovers eventually be offered for CDWG speakers that will provide the optimal EQ?

Thanks

Bob

[Brian Cheney]

Passive filters cannot provide boost.  An old fashioned "bad" tweeter with a rising top end would do the job.  We're still investigating the possibilities.

[DFaulds]

Passive filters cannot provide boost.  An old fashioned "bad" tweeter with a rising top end would do the job.  We're still investigating the possibilities.

They can't provide boost, but you can pad down specific ranges with notch filters and then simply use the higher efficiency of the ribbon tweeter to help with a 10K+ rolloff.

[Brian Cheney]

Unfortunately that's not a good solution for phase coherency.  Notch filters ring.

[James Romeyn]

It's ironic that the almost-extinct but once upbiquitous "Treble" analog tone control offered 10 to 12 dB of boost at a 10 kHz pole...  

A small, active, stereo, affordable, high-pass 6 dB EQ @ 10 kHz is one solution.  It could be offered in analog &/or digital domains.  If variable boost (continuous or multi-position) impedes performance &/or adds to much cost, only an in-out switch is required to accomodate CDWG on vs. off.  Looks aren't critical because the EQ could be hidden.  One box could contain digital, analog, or both domains.  

The advantage of using a custom ribbon tweeter with the treble boost built-in is that it does not require the entire audio signal to pass through it, necessary for the above.    

If the EQ was engineered inside the tweeter, & if flat performance was desired whether the CDWG was on or off: Could the 6 dB cut-EQ at 10 kHz be introduced by simply placing some precision-engineerd cloth in front of the tweeter?  

My 25W tube amp powering only the 90.5 dB ribbon array has plenty of power.  Because the CDWG requires 1.5 dB greater midrange output, the amp will loose 25% of it's wattage.  I hope it's not missed.

[Bob Wilcox]

Jim R. wrote

The advantage of using a custom ribbon tweeter with the treble boost built-in is that it does not require the entire audio signal to pass through it, necessary for the above.

I agree that altering the entire signal is undesirable. A desirable solution would introduce no crud into the signal chain. I don't believe adding devices like the Behringer will maintain lucidity.

Springing for TRT crossover caps doesn't make a lot of sense if you then degrade the signal in front of it.

Bob

[warnerwh]

If the Behringer is strictly used in the digital domain there's zero loss of any lucidity I can detect with my RM 40's.  Just run digital out from your transport to the DEQ 2496 and digital out to a dac. The CS4393 dac and analog stage in the Behringer is not that bad by itself btw. The improvement that can be gained with the DEQ 2496 and it's own dac is much more than just adding your own dac that may be better in most every case I'd suspect. Also the with the DEQ 2496 you can improve the entire frequency spectrum.

Even in my LEDE room with bass traps I feel the DEQ 2496 has been a killer bargain.  A well treated room still has significant amplitude variations, not to mention that all speakers also have significant variations. If you just used it to tame your rooms bass modes and to give that last octave a gradual boost to make an accurate compensation for the CDWG to 20khz it's a wise investment.

Anybody who owns any system that costs over about 2k should have one in their system. I've found amplitude variations to have a huge affect on the presentation of the sound. It doesn't matter what brand speaker it is either. This is something that you have to hear it to appreciate it.

[Bob Wilcox]

The Behringer would not serve my SACD and phono front ends well. I like the new tweeter approach. If the european VMPS site is correct, there may be new woofers as well.

Bob

[Brian Cheney]

I have several new ribbons on hand to evaluate.

For CES I'll be playing the RM30C with two New Original Subs (w/amp) and the sound certainly does not lack for highs even without EQ so far.

[BrunoB]

I have several new ribbons on hand to evaluate.

For CES I'll be playing the RM30C with two New Original Subs (w/amp) and the sound certainly does not lack for highs even without EQ so far.

Here is a suggestion:

For my own 626R, I have modified my ribbon tweeters and, if I remember correctly, the treble was rising above 10KHz. Unfortunately, I don't have have my measurement setup at hand to reconfirm what I had found. The modification I made involves the removal of the front plate and attaching the tweeter to the enclosure by another means. My explanation is that removing  the front plate decreases the horn size of the tweeter by a factor of two.  I am not sure about this, but if it works, it could provide a relatively simple and acoustically neat solution (no filter mod and no electronic EQ). And if the the tweeter is hidden behind the CDWG, there would be no esthetics issue.

Bruno

[Woodsea]

I plan on getting the cdwg.  Now I am wondering if the 2496 can also help with HT, or is it just for stereo?

[SWG255]

Listening to the RM40s at Woodsyi's with the CDWG, i didn't feel a lack of soundstage depth, sparkle, or air in the sound. In fact, i did hear a wider and deeper soundstage, with better instrument and vocal localization within the image, and of course a much wider and deeper sweet spot, I'd say it's now more than a couch length in width, at least more than the length of Woodsyi's listening couch.

I also noticed that the image stayed intact as one moved around the room, a trick i didn't think was possible without loss of pinpoint localization within the image. The instrument and vocal localization of the RM40s with the CDWGs would be the primary reason to upgrade in my opinion.

[SWG255]

Looking at Woodsyi's RM40s with the CDWG, i noticed the foam "half-moons" had to be removed from the "sides" of the tweeter ribbon. Why couldn't the CDWG be used for just the mid-ribbons, leaving the foam in place for the tweeter? I couldn't really tell if the CDWG impinged much on the exposed width of the tweeter ribbon.

Thanks.

[James Romeyn]

Listening to the RM40s at Woodsyi's with the CDWG, i didn't feel a lack of soundstage depth, sparkle, or air in the sound. In fact, i did hear a wider and deeper soundstage, with better instrument and vocal localization within the image, and of course a much wider and deeper sweet spot, I'd say it's now more than a couch length in width, at least more than the length of Woodsyi's listening couch.

I also noticed that the image stayed intact as one moved around the room, a trick i didn't think was possi ...

C'mon, what are you, some kind of shill for VMPS?  You must be on the take.  Another VMPS conspiracy to sell snake oil posing as an audio improvement...

yust kidding...I just thought it would be fun to save samples from having to post his reaction.

If the CDWG masked only the ribbon mids, you would most likely have inferior performance.  The lobing problem would not be solved, & the treble dispersion would be inferior.  Subjectively, most or all beta testers' reactions, regarding hf rolloff, are inconsistent with the theoretical predictions.  Meaning people don't react negatively to the alleged measurable rolloff.  If the speaker had the hi q passives, with decreased bass energy, this would balance well with a slight hf rolloff, producing what may be perceived as proper balance.

Regarding balance, George Louis of Reality Check (digital systems & solutions) knows the 50-60 year old algebraic formula that states a theoreticaly correct relationship between hf & lf rolloff for loudspeakers: To the extent the speaker's bass is limited, so should be the treble extension, to achieve a balanced presentation.  Consistent with this is some audiohile's puzzlement at mini-speakers with severely limited bass cutoff coupled with tiny super extended metal domes.  If the "woofer" is only 5", the speaker may sound worse with extreme treble extension & better with only moderate treble extension, unless a sub is employed.