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David,
I have been following your reviews of the Harmonic Technology CyberLights. It seems to me and maybe others that the significant improvement noted makes a strong case for buying a high quality integrated, thereby eliminating the nasties caused by the IC between amp and preamp. Your thoughts?

Michael Condon

You make an interesting point, Michael. Certainly we have seen that there are times in fine audio when "less [path] is more." For example, I think back to the early and middle 1990's, when there was such a proliferation of PCM digital processing chains: transports, converters...then anti-jitter and additional processing boxes. It got to the point that I saw combinations of gear that would either fail to link-lock, or would lose the link intermittently. It was too much.

Not good!

On the other hand, integrateds face the challenge of other trade-offs: how to find the highest degree of combined functions, without significantly compromising performance. You are right that integrateds lose some of the signal path, but they do so by increasing the proximity of a multiplicity of functions, some of which are not necessarily good neighbors. Power supplies, shielding, EMI, optimal signal pathing, thermal dispersion, function control, optimal performance, assembly considerations...all of these enter into the mix. Inevitably, multiple design parameters (e.g., power output, optimal signal pathing, thermal dispersion, power supply) have to be less than they could be, simply to gain the physical proximity that an integrated must have. That's why I've been willing to live with longer preamp to amp signal paths, even with the RFI and coloration issues, just because I preferred to try to solve that problem rather than compromise on the others.

Then again, different pokes for different folks...you may prefer a different set of listening room challenges, which is perfectly fine.

I am doing two things to address this question personally, and which I will share with our readers in due time:

1. evaluate the Harmonic Technology CyberLights in my own listening room, and assure myself that the IC's involved in the analog-to-photonic conversion sound good; and,

2. review a high quality integrated. Kevin Hayes of VAC has promised to send along his very promising VAC Phi Beta integrated; if he gets it here in a timely fashion, I hope to share my impressions of it before year's end.

All the best,

david

David W. Robinson, Editor-in-Chief, Positive Feedback Online

Hello,
Just wanted to extend my kudos to Mr. Beard, for it is the love of music and not the equipment that makes the audiophile.

Regards,
L.J. Phillips

Dear Mr. Phillips,
Your kind words are greatly appreciated.

I still enjoy audio, but have avowed to never again allow the process to take precedence. I have recently decided to build a new 2 channel system, albeit a more modest one. I am going to continue writing for PFO, having a new focus on lower cost components that offer excellent value for the audiophile on a budget. From now on, I am going to enjoy listening as well as writing (hopefully) good reviews in the bargain. One thing I can promise, I will never again be reviewing gear by listening to one "great" track over and over and over and over…

Dear Editor,
Are there any plans for a review of this new speaker ? I had the opportunity to hear the VR9's recently, but it's too expensive. Kevin told me about the 7's. But I would like a professional review opinion before I pluck down 30 big ones. By the way the 9's were probably the best speakers I've ever heard. Thanks to Jonathan Tinn of Chambers Audio and his customer Andrew Clamps for setting up the audition. There is such a great camaraderie amongst we audiophiles.

Redell Napper

Dear Editor,
I like to comment on Brad Morrical's review of the Sonic Euphoria PLC. When I first received my own fully balanced Sonic Euphoria PLC about 6 months ago, I too thought something was not sounding right with this passive pre-amp. So I decided to look inside and make sure all solder connections were good. (There are not that many to check.) I found one wire that had a bad solder connection to one of the autoformer. After re-soldering that one connection, all was right with the world. My Sonic Euphoria PLC easily out-classed my Audio Research LS-7 which I looking to replaced. I hear no problem whatsoever in the bass as was reported in the review.

Ricardo Hernandez
Sacramento, Calif. 

Dear Editor,
While reading through the letters section, I notice in Greg Weaver's response to Dudley Miller's email regarding Vinyl Zyme a link to Greg's Audio Analyst website. While surfing the site I read through his DIY project for homemade room lens Helmholtz resonators and noticed something I thought I should mention.

In the article Greg states "What we have done, fellow Musical Meddlers, is create a troika of triple Helmholtz resonators, with each resonator tuned to a slightly different frequency by the amount of batting filing the tube."

I believe this statement to be slightly incorrect. I don't have any of my acoustics books with me here at work, but if I remember correctly, the center frequency for a Helmholtz resonator would be determined by the dimensions of the resonator, i.e. the length and diameter of the pipe. Since all resonators are the same, the center frequency is the same. What the stuffing actually does is affect the bandwidth of the absorption. In other words, an empty resonator will have a narrow absorption band. A stuffed resonator will effect a wider range of frequencies but the center frequency of the absorption will remain essentially the same. I believe that similar effects determine the absorption of tube trap type bass traps.

Having seen and "heard" the commercial versions of these things at shows and dealers I am very surprised at how much effect Greg claims for them in his listening room. I hadn't bothered to try them in my own system because I haven't been that impressed (particularly at the asking price). I would have to review my acoustics books for the formula to calculate the center frequency for these treatments. Greg doesn't mention whether he calculated this or why he chose the dimensions he did. On the surface of this it would seem that he has created a lot of absorption at a specific frequency. This doesn't seem very useful unless you already know that you have a problem at the tuning frequency of the resonator. Additionally, if absorption is what you are after, I would think that it would make more sense to vary the lengths of the tubes so that none of them are the same. This would help spread out the effect.

In any event, just building these and sticking them in your system without measurements to quantify the effect seems a bit hit or miss (not that I am guiltless of this). On the other hand, Greg also mentioned that the devices provide diffusion. I suspect if the soundstage was affected in the ways he has mentioned that diffusion and not the absorption effects are responsible. An experiment might determine if this were true. Temporarily plug the tubes. If the soundstage effects remain, then absorption is not the cause.

Enjoy the Music,

Will Wright
Seattle, WA

Editors,
Just today made up a gallon of Buggtussel Vinyl Zyme Gold. Cleaned some of my favorite oldies. This is truly amazing stuff. I had cleaned all of these records with Record Research (both the heavy duty stuff and the regular cleaner), I use both Last products on my needle, and brush the record while on the turn table. I really didn't believe that this stuff would make this much difference. One of my old records sounds like it is brand new and it wasn't even close to that before. Thanks again for another shot at bettering my system. I am gathering the materials to make a set of three Helmholtz resonators (room lens). Will let you know how that turns out in my basement room. Nearly finished now... I keep telling myself that. Dudley Miller, Indianapolis.

Hi David,
Thanks for forwarding this. I'll do my best to respond, and if you want to post it, that would be great.

Kudos to Bruce Beckner for his interesting and thoughtful letter on the subject of bass response in typical rooms. I'd be happy to jump into the fray and offer a few more thoughts on this topic.

First, Bruce is correct that most rooms will have at least one large resonant mode in the bass, and quite often several. "One-note bass" is a pretty common affliction. I would encourage anyone with an interest in this subject to buy an el cheapo Radio Shack SPL meter and a Stereophile Test CD with LF warble tones (am I allowed to recommend another magazine's products here?). For less than $50, you will have a very powerful tool at your disposal; just don't get too upset when you discover how uneven your room's response is. Many rooms will have severe problems in the 60-80Hz range, well above the roll-off of typical speakers, which makes Bruce's main room mode just below roll-off a "lucky accident" that cannot be counted on in most rooms.

Having said that, there are several issues here. One is that it is possible to minimize this problem by choosing both a good room and good placement within the room. Quite often, I find that the best results are obtained with what I call the "back-wall" setup, where the listening chair is pushed up almost against the back wall. The speakers are placed very far out into the room (typically 1/3 of the way from the front to the back wall, or more), and the back wall is heavily treated for absorption and diffraction. While not very wife-friendly due to the way-out-in-the-room speaker placement, this can yield a quite flat response in the bass, along with superb imaging.

The use of "bass traps" for typical room-mode eigen frequencies is almost impossible in most homes, due to the physical size of trap required to actually make a dent in the problem without "killing" the rest of the room's response from the midbass on up.

The other issue is the one I touched on in my earlier "reply". That is, most loudspeakers on the market are high-Q ported boxes, and as such, will automatically give "one-note bass" on their own. Before you get your feathers in a ruffle over this statement, study the physics behind ported boxes. They are resonant systems with a Q of typically 1.0 or more, and as such, will "ring" at a specific frequency when stimulated with an impulse signal. This is an unavoidable consequence of any high-Q system, whether it's a loudspeaker, a tuning fork, or a car with blown shocks. As such, any transient they see, regardless of whether it's at their resonant frequency or not, will produce a ringing at the resonant frequency. (For a graphic illustration of this phenomenon, refer to Loudspeaker Handbook by John Eargle, ISBN 0-412-09721-4, pp. 64 and 73, which shows impulse response data for sealed and ported boxes published by Richard Small in the 1970's.)

In addition, this high Q causes a "hump" of several dB in the frequency response at the resonant frequency. With an overblown time-domain response and an overblown frequency-domain response, if their resonant frequency also happens to coincide with a room mode, things can get ugly in a hurry. And they often do.

That is one of the many reasons it is so advantageous to use low-Q sealed-box loudspeakers. Not only do they have far superior transient response, but their frequency response is inherently flat, so it does not exacerbate room modes. In addition, their roll-off is twice as shallow as a ported box, meaning that they tend to give a much flatter response in combination with the natural LF boost in typical home listening rooms. While a ported box will sound much more "impressive" initially, because it has "more bass", it gets very fatiguing in the long run. The constant one-note assault is just too much to take, and it makes you want to get up and turn the volume down, or the entire system off.

The Ultimate Monitor / BOMB system is a rather unique case, because it isn't every day that you see a small sealed-box monitor with a -3dB point (anechoic) of 32Hz and a system Q of 0.7. While these numbers don't mean much to most people, this is every bit as deep as typical midsize floorstanders, and much flatter and faster to boot. So in this regard, I must disagree with Bruce. The intent in our case was never to limit the bass response, but rather to extend it as far as possible given the physical excursion limits of the drivers, and to keep the system Q low enough to preserve excellent transient response. The tradeoff, as I've stated, is in limitation of the maximum attainable SPL.

I would also say that it is exceedingly rare to find any small speaker with a useful response much below 40Hz. Most of them are ported boxes with a resonant frequency in the 40-50Hz range, along with the typical sharp "hump" in the frequency response at resonance, and they fall like a brick below that. As such, they are missing more or less the entire bottom octave, and yes, any "bass" in that range will often be due to a bad room mode, which is not the same as real bass. The only exception to this was the Sonus Faber Extrema, but it would be a real stretch to call it a "small" speaker. The Extrema was also rather unique in its ability for users to adjust the system Q "on-the-fly", and trade off frequency extension vs. transient response by varying an electrical resistance applied to the passive radiator.

On the subject of subwoofers: Those who have visited our website will note that I strongly recommend the use of subwoofers rather than the BOMBs for all applications requiring maximum extension and SPL's. Specifically, I recommend the use of RELs or others of a similar design, which allow the main speakers to run full-range without any high-pass crossover. I very strongly believe that this is the best approach to subwoofing, and gives results far superior to those employing high-pass filters for the main speakers. There are two main reasons for this, in my opinion:

First, I strongly believe that any "sub-sat" system should use a crossover point below 80Hz, because once the crossover goes above 80Hz or so, it becomes highly audible. So there is no need for extra high-pass filtering if the main speakers are chosen correctly, because no one should ever be using a 100Hz crossover point anyway. The Ultimate Monitors were designed for this approach from the start, and work extremely well with the subs set at around 50Hz (+/- 10Hz depending on the room), which is ideal.

Second, the Ultimate Monitors are a sealed-box design, and as such, have very linear power handling all the way down to the infrasonic range, along with a 12dB/octave roll-off which automatically matches the second-order low-pass filters used in most subwoofers. Thus, they are an ideal match for subwoofers "as is", without needing further protection from LF over-excursion. The same cannot be said of ported speakers, which have a 24dB/octave roll-off and are at high risk for LF over-excursion as well.

There are many who still adhere to the traditional view that a subwoofer should "relieve" the main speakers from reproducing bass, via a high-pass filter. I will state very strongly that this particular benefit not only is of dubious value in our case (due to the extraordinary performance of the ScanSpeak "Revelator" magnet system in a sealed-box loading), but is also overshadowed by the damage done to the main signal's fidelity when it passes through that high-pass filter. It is not just that it's another piece of electronics, although that undoubtedly cannot be beneficial. The real damage is caused by the midbass phase shifts the filter introduces, which are unavoidable and wreak havoc on the musical realism of the system.

I would urge anyone who has never heard a good "sub-sat" system, using high-quality sealed-box monitors and high-end RELs or similar subs, to audition one at your earliest opportunity. I firmly believe that this approach will almost invariably give results that are superior to those attainable with typical 3-way floorstanders of equal cost. The setup can require weeks or even months of effort, but when integrated properly, they truly do give the "best of both worlds". They combine the unbeatable "disappearing act" of monitors with the unbeatable extension and flatness of dedicated subwoofers, and they do it at a bargain relative to full-range speakers of comparable quality. When the setup is right, it simply sounds like the little monitor speakers have seamless extension flat to 15Hz, which is an amazing experience.

Finally, I would venture a guess that Bruce's suggestion for a "shootout" will be a very challenging task. First, the variables in setup alone are enough to make one wonder about the legitimacy of the results. Setting up subwoofers optimally is a far harder task than is generally appreciated. On top of that, the system-to-system variables would be overwhelming-- how do you compare Vandy 5's to a set of Ultimate Monitors plus REL Stentor III's? They're completely different beasts. And I think the Vandys are excellent speakers; it's just that you're no longer comparing apples to apples. The "qualitative" variations between different bass-loading techniques (sealed, ported, passive radiator, ARM, TL, etc.) could easily swamp out any differences between the in-room performance of the various systems. Lastly, as Bruce pointed out, six different listeners are going to have six different opinions about what is "best", so what's good for the goose might not be right for the gander. Having said that, I'm firmly in the camp of adjustable subwoofers, whether they're attached to the mains ala Vandy 5's, or stand-alone units like the RELs. No traditional 3-way will allow the same level of in-room tuning as a sub-sat system, and it shows.

Best Regards,
Karl Schuemann
AudioMachina

David,
First, let me thank you for your efforts and the apparent success of PFO. It's on my very short list of on-line audio publications that I read regularly. (There are some on-line audio publications that I don't read at all!)

The dialog between you and the designer of this speaker was particularly illuminating in that it gave us an insight into how this designer managed the inevitable set of trade-offs associated with building a loudspeaker—even at the rather elevated price level at which he chose to work. While any six randomly selected audiophiles likely will have six different sets of preferences as to what to optimize, it's nice to know what this designer was thinking and why.

The most interesting part of the discussion to me was the colloquy between the two of you on the subject of bass reproduction. I don't think there it can be seriously disputed that the concept of "high fidelity" audio reproduction must include the reproduction of bass frequencies—that's part of the music. But the tradeoffs associated with doing that are particularly nasty—primarily because nearly everyone's home listening room is of a size that's going to have a resonance peak somewhere in the bass range. Therefore, no matter how "flat" the speaker measures, if it reproduces even as low as 40Hz, what we're going to hear in our room is, to some degree or other, "one-note bass" at that resonant peak, which can be as much as 6 or 8dB. I don't believe that resonance can be killed by careful speaker placement; although it might be attenuated by a lot of bass traps, but they are large and pose "decorating issues."

Your apparent preference is to put up with some room resonance in order to hear the bass in the music (and perhaps to limit the loudness level of your playback to avoid exciting that resonance too much). Mr. Schuemann, and many owners of standmount speakers, chooses the opposite trade-off, which is simply to limit the low-end extension of the speaker and avoid exciting the "room boom." If the owners of standmount speakers are lucky (as is the case with my speakers in my room), the low frequency roll-off of the speaker is complemented by the lift of the room resonance; and the net result is a slightly more extended bass response, without any peak. However, that does not cure the other limitation of standmount speakers—evident to the ear and visible in any distortion test (such as those published by SoundStage!)—which is their inability to reproduce the lowest 1/2 octave of their bass response loudly. Typically, the standmount speaker's last half octave of bass response at moderately loud levels has a high proportion of second harmonic. This is relatively benign; but the lack of the fundamental deprives the music of the sense of weight that true bass imparts, whether the instrument being reproduced is a cello, a double bass, a Fender bass, or even an acoustic piano—leave alone a bass drum.

It seems to me that the most promising solution to this problem is either a subwoofer with a parametric equalizer (as the Velodyne Digital Drive subs) that also has a line-level cross over to move the (unequalized) main speakers' response out of the bass range (regardless of their inherent bass reproduction capabilities) or a full-range speaker with a self-powered bass reproducer that includes a parametric equalizer, such as the Vandersteen 5. Either type can then be custom-tailored to the particular characteristics of the room in which the system is operating.

It would be interesting for PFO to precipitate a discussion on this topic among designers and, even better, to run a comparison of the different alternatives (conventional full-range speaker, full-range speaker with parametrically adjustable bass, stand mount speakers with parametrically adjustable sub) in the same room. The test wouldn't be so much about which combination goes the lowest, but about which has the most satisfying bass reproduction.

Anyway, that's my suggestion.

Regards

R. Bruce Beckner

Hello Bruce...

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