[Brian Cheney]

Some years ago at an AES meeting guest speaker John Meyer of Meyersound Labs, a sound reinforcement contractor of many years experience, described equalization as "pushing on jello"  You'd knock something down, and something equally bad would pop up elsewhere in the spectrum.  Plus the effects of boost of cut were dependent on microphone and listening position, since path lengths of late arrivals changed drastically as one moved around in the venue.  Echo was almost impossible to eliminate in larger areas, and reflections of unequally dispersed frequencies would combine and break up in unpredictable and usually highly undesirable fashion.

Audiophiles situated in typical listening environments have it much easier.  Many  learned that acoustical treatments (absorption, reflection, diffusion) can break up room modes, and shifting speaker and listening position can  defeat two (side to side, front to back) of the three major modes, the last of which is floor to ceiling.  Audiophile speakers are seldom further than 15 ft from a wall (the critical distance from which reflected energy is perceived as echo), and listeners who sit well back in their rooms can enjoy a randomization of the late arrivals, or even listen from an adjoining space where the directional nature and poor directivity of most speakers has evened out.  Thus the "sounds live in the next room" effect that many have observed.

Many audiophiles therefore have learned to shun equalizers and active EQ.  And they are for the most part justified in so doing.  Even a 1/3 octave graphic equalizer will miss critical frequencies you want to tame, and most parametric EQ's lack enough bands to be really helpful.  Plus most people, especially experienced engineers, rely on microphone measurements and microphones, unfortunately, simply do not possess the discrimination or directional characteristics of the human ear: what measures flat rarely sounds flat.

Now if a speaker had on-axis response exactly the same as its off-axis response full range, and early reflections in its vicinity were tamed with absorptive panels (like Sonex) and bass traps (many different brands), then active EQ would indeed be helpful, particularly if it were of the parametric variety with a large number of pole frequencies, variable Q's , and levels adjustable in small steps, say 0.1dB with sufficent range (say +/- 15dB) to squelch even the wildest FR peaks and valleys.

I'm not giving you all this buildup just to say sorry, hasn't happened yet.  In fact, the future is now.  As most visitors here know VMPS has made constant directivity speakers for three years.  On axis and off axis response is the same down into the bass range, where the woofers transit into 4 pi or omnidirectional space which is natural for music.  The pattern is hypercardiod, which means little energy beyond the plus and minus 90 degree dispersion of our CD speakers goes into the room behind or beside the speaker.  This controlled directivity makes active EQ not only possible, but desirable, in a way not heard before.

Enter the digital EQ of the DCX2496, a highly flexible, sonically neutral, active crossover and equalizer with many bands of parametric EQ, 30dB of range, and levels adjustable in 0.1dB steps, all with a quick learning curve and a low price.

This is a new age, the age of micro-equalization, and the possibilities are impressive, even spectacular.  As an example, the Bruce Thigpen designed, Neodymium motor, push-pull planar midrange panel we use has a characteristic 2.5dB hump in the 1kHz to 3 kHz range.  I have always left it alone, since it added some not unpleasant forwardness to the sound and a notch filter would have created havor with the smooth phase response of our first order slopes.  With the DCX2496, I can reduce that hump to flat with a few clicks.  Astongishingly, moving the pole frequency from 2 kHz (center of the hump) to 1.9kHz proved even more effective, a phenomenon not to be anticipated from mic measurements and indeed, not visible in same even with the highest resolution my measurement programs offer.  The CD waveguide which makes for 180 dispersion of all frequencies down to mid panel cutoff (till now 280 Hz), also introduces an HF rolloff which many VMPS owners have noticed.  This rolloff can be completely eliminated by the DCX, also with a few clicks.  Same for the floor-to-ceiling room mode (I have the common 8ft ceiling height, and cut 71Hz by 4dB to eliminate the effect).  I can increase heft and weight in the low range with a 2 dB boost at 35Hz and can vary its Q in an instant.

I will post more about the subject in the next weeks.  Suffice it to say new vistas in high quality home audio have opened.  All you need is a constant directivity speaker like any of our Ribbon Monitors, a decent room, and biamping with the DCX.

[Hipper]

I have RM30Ms with the normal crossover.

Like some others (Warnerwh comes to mind) I have a Behringer DEQ2496 Digital Equalizer. Along with Auralex foam on the live end walls, this makes a major contribution to the sound I enjoy.

In order to achieve this sound I used a Berhringer ECM8000 microphone which is cheap and presumably not that accurate. The DEQ2496 has a 31 band graphic equalizer (GEQ) plus a 10 band Parametric Equalizer (PEQ). You can also adjust the left and right channels seperately. There are a few guidelines on the internet but basically I placed the speakers where I wanted without much consideration for the sound (right back against the wall and almost in the corners), only fine tuning the toe-in. I then attempted to get a flat response at the listening position by using the GEQ and then filling in any blips between bands with the PEQ. After this I followed some advice on the internet as to adjustments for best sound and finally tweaked it a bit by ear for my own tastes.

Although the DEQ2496 has its own DAC, and ADC, it sits between my CD Transport and DAC and so works only in digital which is what most people recommend (my DAC acts as a Pre-amp so I don't know how I would use it if I had a seperate Pre-amp). When I occassionally play vinyl I feed the anologue signal from a phono amp to the DEQ2496, through its ADC, then eqaulizer and then out as a digital signal to my DAC.

I've not used a Tact or DEQX (which are ten times more expensive) but am very happy with the Behringer, which I've had for two years now.

For me, Digital Equalizing is the way to go. As I've mentioned before, I find it the single most important piece of kit I have (even before the speakers - sorry!).

[Brian Cheney]

Can't argue with you there.  In coming weeks I will outline more applications for the DCX which astute listeners can do without help from mic measurements.

[Scottdazzle]

Brian and Hipper,

I also have RM30M with the normal (Auricaps) crossover - just got them a few weeks ago.  The thing I don't understand about digital equalization is what effect the process will have when playing vinyl.  Can either of you discuss the tradeoffs of digital equalization while playing records?

Scott

[Brian Cheney]

I just posted on this subject in the SDE thread.

If you have outboard analog crossovers adding the preprogrammed DCX ($599, you must biamp) is easy. 

LP sound through the DCX is quite good but not the equal of analogue direct.  As I mentioned, it is quite possible to do it both ways.  All you need is a bass amp.  If you want me to prematch levels for you, send me both amps and for $150, I'll balance them out with the DCX for the VMPS model you own.

[Hipper]

Scott, I'm afraid I'm no expert on playing vinyl with a digital equalizer. As Brian alludes, the problem is you have to convert the analogue sound to digital using an analogue to digital converter (ADC) and then convert it back to anologue using the digital to analogue converter (DAC). The Behringer DEQ2496 that I use (and Brian's DCX) has an ADC and DAC but as it costs about $300 there are probably better possibilities for converters.

I don't play vinyl much - I've concentrated all my efforts on CDs now but there are still some records not on CD (although I'm in the process of converting them to CD and removing the scratches etc.).

Ideally it is generally thought that we should have the simplest possible signal path, so all this converting may be frowned on, but I find when playing vinyl that the difference in sound from using the equalizer is so startling (at least in my circumstances) that any possible loss (and I can't really say if there is any loss) from the ADC and DAC is not really noticeable. I should add that I use a Son of Ampzilla amp which is said to have some tube like qualities, so this may help.

[Scottdazzle]

Thanks. More food for thought.

[Brian Cheney]

For those who don't want to biamp and still get the benefits of digital EQ, the DEQ2496 is available for about $300 and provides the EQ functions of the DCX2496.  Any VMPS owner going this route can contact me for recommended EQ characteristics for their particular speaker.

[PLMONROE]

If you want me to prematch levels for you, send me both amps and for $150, I'll balance them out with the DCX for the VMPS model you own.

Obviously the would be the optimum step to take. A major drawback for me is that each of my amps have a shipping weight of 115 pounds. In addition, both the major shipping companies seem to take every step possible to insure that, without exception, every parcel arriving at my address is damaged in one form or another! 

How about a quality six way volume control? What are the drawbacks to this solution?

Paul

[Brian Cheney]

If you are biamping with identical amps you don't need to go through a level matching trip to the factory and risk shipping damage.  The program was designed around identical amps (I use a pair of the Son of Ampzilla).

It's only when the two amplifiers have different input sensitivities or large differences in input impedance that level matching becomes a really good idea.  Since the woofer section is less efficient that the mid/treble, the bass amp runs 4 to 5 dB hotter than the mid/treble amp.  A SS bass amp will typically have an input sensitivity of 1.2 to 2V, whereas a tube mid/treble amp can often be twice that sensitive.  This means the bass amp needs to run at an even nigher level than if the amps were the same..

We will make a 6way passive volume control available.  This is a lossy component I would rather keep out of the chain, however, and I think active level matching should sound better.