Paul's Posts — 27 October 2012
By Paul McGowan
We’re in the middle of our mini series on power and vibration control for our hi fi systems. Yesterday I explained that vibrations, caused by the loudspeakers in our listening rooms, were inevitable and instead of focusing on minimizing or eliminating them we would be better served to treat them like we would room reflections.
When you play speakers in the room you get reflections off the room walls. You can try and absorb and minimize those reflections or you can scatter and diffuse them instead. Over the years we’ve learned that diffusing them is a much more effective tack than absorbing and this is because when the reflections are diffused, our ear/brain mechanism will interpret them as random unrelated noise and easily ignore their contributions.
If we use the same technique on vibration and microphonic control we get the same results – that of the ear/brain ignoring their contributions. Diffusing is far better than reducing and here’s why.
If you try and damp out the vibrations occurring in your room you will be only partially successful – because you simply cannot eliminate them all. Whatever is left is still a focused and related ghost image riding on your music and, although reduced, it will still be perceived as distortion and smearing in your listening environment.
Cones and spikes under equipment, for example, reduce microphonic effects but don’t diffuse it – in fact they probably make it worse and here’s why. Cones and spikes work by reducing the contact area between the equipment and the vibrating surfaces. They are, by their very nature, extremely rigid and transmit specific frequencies to the equipment – thus further focusing the unwanted energy. Several manufacturers have used varying hardness materials within a cone to help this issue, but in the end their purpose is to reduce contact area and thus reduce surface-borne vibrations. The second problem they have is that they do not address airborne vibrations.
In fact, at least half of the microphonics issue comes from the airborne vibrations and, unless your equipment is in an acoustically shielded environment, there’s little any of these isolation bases and cones and feet can do to help. They are valuable under the speakers but I would recommend not using them under the electronics.
So the best answer is, again, diffusion and masking rather than absorption, isolation and futile attempts at vibration reduction.
Tomorrow I’ll show you how this works.
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oxbow
Hi Paul,
Thanks for the great series.
I don’t agree with your blanket comment on the effectiveness or otherwise of various products to reduce vibration transmission. My ears are particularly sensitive to vibration artifacts and this has led to a 30 yr search of tweaks. I have found that various products (such as spikes, sand bags, or roller balls work really well under some components and are useless under others. Some components are more sensitive to interconnects than others.
My biggsest bang-for-bucks came from a dedicated line from my power box, and a quality filter (later replaced with a PS Audo regenerator). These gave me blacker backgrounds and clearer pictures on my TV; and a wider soundstage, and dramatically more detail from my stereo. But it still benefits from little tweaks like the aforementioned or moving a speaker a half inch.
Best advice that I have received: “Trust your ears, not your (or someone else’s) head trip”.
And: “It all depends”.
Regards,
Bill
Paul McGowan
I am with you on that. Trust your ears.
I would suggest that one can make blanket statements with some degree of accuracy some of the time if we manage to keep them fairly broad and reasoned – but in the end no one thing can be perfect for another thing – as you say, it all depends.
Thanks for reading.
paulsquirrel
Hi Paul.
Finale there is a qualitative measure (>50% of distortion is air-borne) helping to start tweaking at the most effective levers.
Can one consequently conclude that closed/ sealed speakers or even better in-(concrete-)wall speakers with small membranes minimizing the surface of impact are the best protection against air-borne vibrations?
Should one “glue” the bottom of the electronic device to the heavy rack shelf and remove the cover plate both minimizing the impact-area? The last measure always worked find in my system.
However I made most convincing experiences with sophisticated footer designs being a major design feature in turntables!
But following your argumentation I feel that the biggest potential for improvement lies in the speaker design? Would you agree here?
Finally I believe that the vibrations created inside the device by the transformer or other components oscillating on the pc-board are a major cause of sound degradation – thus mechanical grounding and/or minimizing the vibration by damping measures would be the only solution here – not diffusion!
Final conclusion: no transformers inside the device housing the sensitive audio circuits and battery-/super caps-power supply.
Regards
Michael
Paul McGowan
Certainly the speakers play a big role but you’ll never get them to not create the problem unless you turn them off – for it is the sound pressure levels we want from them that can do the “damage”. However, if instead you mean cabinet vibrations and building inert cabinets then I am with you. I have never seen anything in a speaker design more important that getting rid of the cabinet resonances.
As you’ll see in tomorrow’s post there is a method to my madness about diffusion – but diffusion done right and with a purpose. Stay tuned.
Soundminded
I’m so diffused!
I know it’s off topic but speaking of diffusion;
http://www.audioheritage.org/html/profiles/jbl/paragon.htm
If you’ve never seen one of these ten foot monsters you’ve missed something. Of the 1000 or so that were made it appears no two were exactly alike.
Do you think Dr. B*$# saw this before he designed his model $$$?
Paul McGowan
Mark. That’s the single coolest speaker I’ve ever seen. I am inspired. Thanks!
Soundminded
Photos can’t begin to do it justice. It’s even more impressive in the flesh. I think the combined unit weighs about 800 pounds. Over 50 years after its introduction, it is still a remarkable statement. I think many of them wound up in Japan. The price around the time it was first introduced was about $1800. At the end I recall around $4000.
Paul McGowan
Did you ever get to hear one extensively? What did it sound like? Was the idea they used of bouncing off the curved surface work well?
stuggs
Thanks for these articles on microphonics. Going forward any suggestions you have on diffusion in a room that would also be aesthetically pleasing would be helpful.
dr.goodears
“there’s little any of these isolation bases and cones and feet can do to help”
Michel Reverchons pioneering work in the area of mechanical grounding concepts has influenced almost every high-end audio engineer over the last three decades from the precision-milled aluminum chassis of a Jeff Rowland amplifier to the platter and plinth construction of a Basis or Walker Audio turntable to the enclosures of Wilson Audio and YG Acoustics loudspeakers to the passive isolation filters of Townshend Seismic Sinks and Critical Mass equipment racks to good old Granite slabs and shelves.
I agree that if a component is properly engineered the after market bases, cones and chassis dampers minimize effect and that much of the after market devices are poorly designed and constructed but numerous mass market kit can benefit from proper implementation of resonance tuning and damping external and internal.
With the evolution of wireless music servers dominating many music systems throughout the world today the opportunity to locate source components and electronics in another area of the home outside of the listening room mostly renders this discussion mute.
I guess that’s another sales advantage of your connected home systems engineering. But wait, the upcoming and revolutionary PS Audio amplifier needs speaker cables to connect to a loudspeaker. How do we overcome this limitation?
The solution may render many cable manufacturers obsolete, yet another common casualty in the internet era. Look at what it took to get ol Sam Runco back into the game again!
oliver T. Finch
Given a choice between resonance suppression and diffusion ,diffusion is better but the combination of the two is significantly better. This conclusion is based on personal experience and am using this with excellent results. Cones are part of the combination. They can give good results if done right. Cones alone are not very effective. You are very right. Regards.
Soundminded
To be perfectly honest Paul, I only saw and heard them about twice at audio shows, not usually places to make any critical judgments about anything. It was so very long ago. The first time I seem to recall they were on some sort of platform at ear level at some distance. I seem to also recall on another occasion seeing the back of one with a built in solid state power amplifier. I didn’t hear them for long and frankly I just can’t remember. They probably struck me as good but unremarkable. I’ve read reviews that claimed they could produce extremely deep powerful bass but I don’t remember hearing it during the shows. About the only thing I can remember is once thinking that it seemed to me JBL used the best loudspeaker drivers in the industry at that time to make the worst sounding speaker systems. I don’t think there was ever a JBL speaker I liked the sound of. There were other models that were truly irritating. One I’d heard years later seemed to be a tower with metal cone drivers. Another, a large studio monitor that had some sort of lens in front of the tweeter and I think the grill cloth had some sort of checkerboard textured block patern made from a foam material. Now come to think of it, I’ve never heard a horn speaker I liked, I was no fan of the West Coast sound. Also memorable for being fairly awful was a speaker I did spend some time with, the Altec A7-500. Very harsh treble. Another Altec speaker I had borrowed for a few years from a friend, the Flamenco I think had the same harsh treble.
But then I was no particular fan of most of the east coast speakers either. AR was very disappointing with its muffled high end. Large Advent was terrible IMO. I once liked the KLH model 6s I owned. I’m not so fond of them anymore. And just recently, in the last few years I’ve heard a few electrostatics and I found them badly flawed as well. I’ve come to the conclusion that the only one who will ever design a speaker I like is me. It’s only during the last 23 years I’ve become a really critical listener. There were some speakers that struck me at the time I heard them as very fine during brief exposures but I probably would have grown to dislike them. One in that category was Snell AIIi. Someone I know had a pair and I’d heard them on many occasions. It had an interesting and unique sort of distortion I liked.
BTW, there was a smaller version of the Paragon called the Metrogon. I can see you are as intrigued with this striking and unusual cabinet as I was. In a way, seeing it was one step down the road to perdition for me. It was the first time I ever saw anyone manufacture a speaker system where it was okay to bounce sound off of something deliberatly rather than aiming it direclty at the listener. If I’d only guessed then where that would lead me.
Paul McGowan