Shelf Physics

Hi Howard,
Since nobody else seems willing to dive in. May I jump in on your thread & try a bit of lateral thinking? Has anyone has ever tried listening to their system with the speakers in their usual place and their entire system outside the room? It would obviously need longer cables. But this would surely destroy, once and for all, the notion that the shelves/racks are seriously reducing acoustic feedback and that this is the reason for the "improvement" one is supposed to hear with different racks. This would be sound level sensitive in my view. A Fraim would only work at high volumes.
I'm more inclined towards the idea that racks filter micro-seisms. The natural low level vibrations that travel through everything as a results of the Earth's own activities. Earthquakes, volcanoes, plate movements, plus traffic vibrations, local foot falls, wind on building structure etc. etc. These affect microphonic parts of the system. Causing them to register their own sounds through the amplification of these effects. Thus affecting the music as perceived by the listener.
If it was simply a case of reducing acoustic feedback we could all simply fit our systems into heavy (security) safes in the listening room (or in the wall with a heavy door). With only a couple of speaker cable terminals and a sensor for the zapper visible externally.
The idea of a safe may have other benefits. Not least fom the theft point of view. But the heavy nature of the article would allow relatively easy isolation from the environment. High mass/ low compliance. Full isolation from both seismic and acoustic effects in one. Nirvana straight out of the box. Or rather in it. Then you can all start arguing which are the best shelves for use in the safe!

Nime

Everyone has the right to be wrong.

A decent rack also makes headphone listening better.

Racks don't just isolate the sistem fom the speaker output, they also dissipate, and/or absorb energy from within the components themselves.

Otherwise we could place our speakers on Mana Phase Umpteen with our electronic components on the floor.

As for other variables such as footfalls, and lorries travelling near your abode, most of us don't live in a constant earthquake/tremor zone.

As for wind, a solid structure doesn't move unless it's a serious wind - I'm thinking of a Scale ten or more



Regards,

Steve.

I used to think it might be possible to use an ordinary pickup cartridge resting on a surface (probably with a suitable raising block) to discover something about the natural resonance of the shelf or the framework while actually in use. Or (possibly) even better. A cheap acoustic guitar (surface) pickup would not break the bank. Don't try this with your expensive moving coil in your ARO at home though children. You'd obviously need a seperate amp to boost the signal to earphone (or external speaker) level.

Does anyone actually own a patent on their racks? Registered design perhaps. But what about a real patent? The'd have to prove a unique method of improving something to a sceptical patent examiner. That's much more difficult than simply registering a particular design feature.

Nime

Everyone has the right to be wrong.

quote:

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Originally posted by Nime:
Has anyone has ever tried listening to their system with the speakers in their usual place and their entire system outside the room? It would obviously need longer cables.

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Nime,

I used to run with this config in my first house.

It did sound astonishingly good. Let's put it this way - sceptics would come over thinking a £25K hifi was a ludicrous idea, and go away shaking their heads and agreeing that if you had the money the results justified the outlay.

I now realise, though, that it would have been a lot better with decent stands.

cheers, Martin

E-mail:- MartinPayne at Dial.Pipex.com

Gents,

I vaguely remember some old lectures in which we were tought that magnetic cores expand and contract during magnetic cycling. It explained why the transformers on overhead powerlines make a gentle humming sound.

Assuming that hifi transformer cores are made of the same material you could then conclude that our hifi powersupplies generate small vibrations that would need to be isolated from the rest of the gear.

Placing the gear in a separate room would not isolate these types of vibrations.

On the other hand, since the signal in most Naim gear is routed through the power supply, this effect may be negligible or the cables are not as sensitive to microphony (or perhaps I am just plain wrong)

cheers
Gus

"I vaguely remember some old lectures in which we were tought that magnetic cores expand and contract during magnetic cycling. It explained why the transformers on overhead powerlines make a gentle humming sound.

Assuming that hifi transformer cores are made of the same material you could then conclude that our hifi powersupplies generate small vibrations that would need to be isolated from the rest of the gear."


Gus,

the Naim transformers are famous for buzzing.

Naim have tried many fixes. It can be minimised by loosening the securing bolt, or placing damping material under the tranny, but it always makes the system sound worse. It seems very important that the vibrations from this be dumped out through the chassis and into the rack.

cheers, Martin

Thanks Guys. I got the response I expected. I intend to play with some cheap tweaks and see what transpires.
What confuses me is that Naim (and others) make VERY expensive supports, balls, sockets wood etc but put 4 small cheap looking door stops on the bottom of their kit. If the idea is to get the vibrations out of the kit into the support shouldn't the case feet be more solid?
On reflection as some one said if what ever you sounds better to you what other criterior do you need?
Thanks for your responses.

Regards

Howard

Howard,

just one word of warning - whenever you come up with a home-brew arrangement that works, you have to clearly bear in mind that it happens to work in your current config, in your room, and probably with your music choices too.

Any significant change elsewhere will mean that you must re-consider all such tweaks to see if they were merely compensating for some deficiency elsewhere and are now holding things back.

Case in point - I have a choice of two glass slabs that I can use in my home-brew arrangement under my CDSii. After I repositioned the DBLs & finally got the bass seal done properly, the one which was obviously the best before was then holding the system back very noticeably.

cheers, Martin

Good point Martin.I don't know really what my kit should sound like,its been made up over the past year. Each piece has been heard separately. I have not had any body round to critique the system and dealers are unlikely to have the same kit in stock any more.
Perhaps in time some "locals" can get together for listening sessions.

Regards

Howard

quote:

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Originally posted by BigH47:
Good point Martin.I don't know really what my kit should sound like,its been made up over the past year.

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Howard,

actually, I meant that it's fine to tune things to get the best sound that you can. Whatever works for you is right.

After a major upgrade (either a purchase or a major tweaking success) you may need to reconsider your current tweaks.

cheers, Martin

E-mail:- MartinPayne at Dial.Pipex.com

Jon W is right about the set up being difficult.I got the Keosa's (Birch finish) they sounded good in the shop, their footprint was a great deal smaller than Index plus on Sara stands.and the price £220. They look Ok without the "hairnet" grill covers on.IMO.
I am struggling to get a good soundstage and seem to have too much bass (or lack of treble).
Send a private message if you want to chat.

Regards

Howard

[This message was edited by BigH47 on MONDAY 20 January 2003 at 18:21.]