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POSITIVE FEEDBACK ONLINE - ISSUE 17
 
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Our readers respond…we respond right back!

Send your comments to either drobinson@positive-feedback.com or dclark@positive-feedback.com

 

 

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…

Cheers, and thanks for reading.

Gary


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

Hello Redell...
At this point, having done the VSR 4's pretty thoroughly, I'm hoping to get a pair of the VSR 9's in the door here for a review, though I wouldn't mind doing the 7's as well. This is still at the discussion stage, so we can't promise anything yet.

As a former owner of the original VSR-4's, the VSR-4 Silver Edition, and the VSR-6's years ago, I am a fan of Albert's brilliant design work. If it's up to me, PFO will be doing a lot more work with the VSR line, Redell. We'll post any scheduled project in our "Coming Soon" section.

And you're quite right: Jonathan Tinn is a very special person, who always does things in a superlative way. In my experience, there's no better dealer in fine audio than Jonathan.

All the best,

david

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


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 Ricardo,
It is interesting that you found something so small as a solder connection to make such a large change in the overall sound of the unit. I would not have suspected such a thing unless there was a clear failure to produce sound from the unit at a particular setting I did not do such a check as I found that all the functions of the preamp were working correctly. I also have the feeling that most other customers will not be so inclined to do such a check (although now that you have made us aware of it they might) if there is nothing obviously amiss with their unit. Unfortunately, I could not keep the Sonic Euphoria as I had to make a decision within 30 days whether or not to keep the item. If I still had the unit I would indeed do as you suggest and then reevaluate the preamp. As it is, I found nothing functionally wrong with the preamp and have reported the sound that I heard accordingly.

Best Regards,

Brad Morrical


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

You are indeed correct. I cannot say now (I originally authored that piece in 1999) whether I was trying to simplify the matter or if it was just plain haste on my part that caused that misstatement, but thank you for pointing it out.

The fundamental frequency of the resonator is entirely a function of volume as described by diameter times length. Also, as you correctly point out, the internal batting merely widens the Q around that center frequency. Effectively, that polyfil material plays a "sonic illusion" on physics by convincing the air in the tube that it is actually a somewhat larger space. The dissimilar loading for each tube is meant to afford each one with a slightly different tonal impact, in theory, offering a more significant result.

I also agree the diffractive/diffusive properties of these devices have the strongest effect on the soundstage and imaging. I think that point effectively demonstrated in the first and second paragraphs under "The treasure" section of that work. Yet the third paragraph of that same section goes on to note the impact they had on timbre and tonal balance. The rest of that section, such as demonstrated by paragraph four, notes more detail about their impact, sometimes individually singling out one or the other attribute, sometimes combining them both within the same paragraph.

While there is no question in my mind that the diffractive component is the stronger of the two forces these devices bring into play (perhaps 66 to 75 percent diffractive/diffusive with the remaining 33 to 25 percent being their tonal contribution), these devices impart two distinct and different effects.

I hope that clears it up a bit. Thanks for reading, and for taking the time to write.

Greg Weaver the audio analyst©


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 Dudley,
I am happy to hear that you found Buggtussel’s Vinyl-Zyme as effective as I have. Kevin’s formulation is truly ear opening, and is by far the most effective cleaning solution I have come across for the sonic restoration of older LPs. Other fluids may be more successful at the removal of mold release agents (Polytetrafluoroethylene, or Teflon™) and other contaminants specific to new vinyl releases (such as Duane Goldman’s Disc Doctor Miracle Record Cleaner or Brian Weitzel’s Record Research Labs Super Vinyl Wash), but for those “pre-owned” acquisitions or records you’ve had forever, nothing else comes close in my experience. Thanks for reading, and for taking the time to write.

 Greg Weaver the audio analyst©


Hello David,
First off, thank you for a great online magazine. One of the best out there in my opinion. I look forward to each issue. Keep them coming.

The "Brutus Award" bestowed to Allen Wright's VSE modification for the Best SACD Modification is well deserved in my opinion. After reading your enthuiastic review of the VSE modded 9000ES I just couldn't resist the temptation of having my SCD-1 fitted with the balanced VSE level 4 mod, especially since one of the installers, Warren Gregorie is within driving distance of me. Incidentally, Warren is a pleasure to work with and comes highly recommended to anyone on the West Coast USA who is considering going the VSE route.

I have been following your "I Don't Drive Stock!" series from the beginning, and now have added most of the Audiocom modifications to my SCD-1 including Vishey resistors, Blackgate capacitors, Super Regulators, Super Clock II with Power Supply, and Richard Kern's "Transport Mod." The combination of these additions have improved the sound over the stock player substantially.

I did not expect the degree of improvement that I heard after Allen's Level 4 version was added to my Sony. Through the VSE outputs the sound is elevated to yet another level. The increased transparency is most apparent. It as if a layer of fog has been lifted which subsequently lets all the music come through. There is an ease to the music that which the previous mods just can't match. In other words there is more resolution but at the same time there is more a more natural, less HiFi perspective lent to the music. I hear a better resolution of dynamics, detail, micro-dynamics with an improvement of the timbre of acoustical instruments and voice. For example, massed strings sound less mechanical and more like the real thing and well recorded voice is very special and lifelike on good recordings.

The improvements are equal on both Redbook and SACD with an almost analog smoothness lent to the sound of better recordings, especially with SACD. With Allen's mods the merits of a good DSD recording really shine through and demonstrate its superiority over Redbook. Before having the VSE fitted to my SCD-1 it was almost as if SACD sound was restrained and held back somewhat, thus not allowing for all the sonic glory to come through.

Thank you for your excellent assessment of the VSE modded 9000ES and for enlightening your readers on the virtues of Allen Wright's VSE modifications. For anyone considering modification to their SACD player, I highly recommend going with Allen's VSE package.

Using your own words as written in your VSE modded 9000ES review in PFO, "If you can't get thee to a Meitner then do the next best thing: get thee to Sir Allen of VSE." I enthusiastically second that!

Best regards,
Bob Fosse

Thanks for sending you comments along, Bob; we'll publish them in "Reverberations." You're right, and you and I are hearing the same thing; the VSEI mods are stellar!

Glad to hear that you're enjoying PFO...helping our readers is one of the reasons that we do this, after all....

All the best,

david

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


Hi, Does your magazine have any plans to review any digital amplifiers? In particular I am curious about the Tact and H20 models.

Gerry Geisler

Hello Gerry... No, we don't have any plans to review the Tact line or H20's at this time. We might be looking at the Spectrons again soon, though...too soon to say.

All the best,

david

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


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...

I want to thank you for a thoughtful and literate response to the dialog between Karl Schuemann and me. Positive Feedback Online seeks to stimulate a true creative forum for fine audio, as our subtitle suggests; your letter is an excellent example of what we seek to stimulate in the audio arts.

You are correct as to my preference: I accept a degree of room resonance in order to have the deep foundations of the music. I have a couple of ASC tube traps in the rear corners to knock this down a bit, and have vents placed in the side rear walls behind speaker to allow bass overflow to go into spaces on either side of the listening room. It helps; so do the cambered side-to-ceiling interfaces, and the very solid construction (2" x 6" studs, wall-within-a-wall left and right). The room is by no means ideal...far from it...but it sounds much better than you'd expect. Nevertheless, there are certainly trade-offs, and I have made my choice quite willingly.

Your suggestion of a comparative evaluation of alternative designs is an excellent one. If both the candidate designs and the logistics could be resolved, I'd certainly be willing to have PFO host such a project.

I'm cc:'ing Karl Schuemann so that he can respond to your comments. Karl, if you do so, make sure that you cc: me; I'll see that this exchange is published in "Reverberations," extending our original interview and dialogue.

All the best,

david

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


 

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