Loudspeakers: spikes or decoupling?

[jayne lee wilson]

He went a lot further then that! He measured the vibrations.



He's an American audio expert so maybe he hasn't looked at what the BBC is up to in particular. But given his impressive website I wouldn't be surprise if he's looked at "thin walled speaker design". But I'll leave you, or the OP, to dig into his website if they want to look into this in detail.

Sorry, think I'll pass on that one... there's that thing called music to listen to...
This guy might do better listening more, measuring less... (subjectively, of course....)

[johnb]

Thanks for the very interesting responses to my opening post.

About the article that Mal provided a link to: the author mentions IsoAcoustics (the manufacturer of the Gaia feet I mentioned) and writes:

The IsoAcoustics testing page shows the impressive photos at left of a "laser vibrometer" test conducted by the National Research Council in an anechoic chamber in Ottawa, Canada. The photo description is equally impressive sounding. But there's no audio measurement data! These photos show only that vibration (orange) doesn't travel down through the stand to the table (green). At least that's what they claim is shown. Apparently they tested only at 75 Hz, so we'll never know how well this product isolates other frequencies.

That might have been the case when he wrote the article but the current IsoAcoustics website shows test results for speaker vibration with spikes/with Gaia across the audio frequency spectrum (you need to scroll down a bit): http://www.isoacoustics.com/isoacous...r_colorization

I'm not sure that his own testing reflect my own circumstances (i.e. a suspended wooden floor) but it is always interesting to read contrary views.

I suppose I could do my own tests, similar to those he did (I have a measurement microphone etc which I have used for DRC setup measurements). But I very much doubt whether I will ever get round to doing so.

I think the point he makes about Bass Traps is particularly valid. People interested in audio quality can spend considerable amounts on kit whereas some of that money would be much, much better spent on Bass Traps (and I am as guilty as anyone). The problem is most of them are not exactly attractive when placed in a domestic situation.

Bryn,
You mentioned paving slabs. I seem to remember the PMC website recommending putting their speakers on heavy stone slabs. I haven't checked whether that is still their recommendation.

[Eine Alpensinfonie]

My Wharfdale speakers are designed to be filled about half way with sand.

Sand-filled Wharfdales. Great speakers, but I haven’t seen any in years.

[Anastasius]

Only 20kg

Lightweight. Now these were proper heavyweight loudspeakers.

http://www.saturn-sound.com/images%20-%20diy%20projects/diy%20-%20horn%20loudspeaker%20mk2%20-%20hi-fi%20news%20-%20oct%2067%20-%201.jpg

They sounded pretty good as well !

[gradus]

Only 20kg

Lightweight. Now these were proper heavyweight loudspeakers.

http://www.saturn-sound.com/images%20-%20diy%20projects/diy%20-%20horn%20loudspeaker%20mk2%20-%20hi-fi%20news%20-%20oct%2067%20-%201.jpg

They sounded pretty good as well !

I remember the articles but you actually heard them as well. I imagine they required little power for great volume and earth-shaking bass. I wonder if they are still working?

[Lordgeous]

I remember as a kid visiting a quite well known hifi writer and record reviewer at his home in Headingto, Oxford (maybe he was Percy something?). The two downstairs rooms of his house had been converted into one space and each fireplace/chimney had a bass speaker installed in the aperture (Stereo), utilising the whole chimney as cabinets!

[Dave2002]

(msgs 19,20)
I thought those horn under floor speakers could go down below 30 Hz. I met JC once after a Prom concert, quite by chance - in the Arena. It was fairly obvious who he was - hardly anyone else would have speakers like that under the floor. He said that he had a cheat - the system also had a low frequency oscillator which he could switch in or out - perhaps around 8Hz. If he was listening to music, such as Mahler's 8th (not sure if he did listen to that) at the climactic parts he would discretely feed in the oscillator signal to make the room shake, by means of a button under his chair. This usually impressed his friends. He said it didn't really matter too much what the frequency was if it was low enough - as one couldn't "hear" the low notes, only feel them.

He also commented that few recordings at the time actually had any signals below 30 Hz, so to get really deep notes required fixes such as the one mentioned.

A similar idea is now used in some home cinema systems, where there seems to be a new fad for butt/bottom shakers.

[gradus]

I remember as a kid visiting a quite well known hifi writer and record reviewer at his home in Headingto, Oxford (maybe he was Percy something?). The two downstairs rooms of his house had been converted into one space and each fireplace/chimney had a bass speaker installed in the aperture (Stereo), utilising the whole chimney as cabinets!

Could that have been Percy Wilson Technical Editor of The Gramophone for many years?

[MrGongGong]

I remember as a kid visiting a quite well known hifi writer and record reviewer at his home in Headingto, Oxford (maybe he was Percy something?). The two downstairs rooms of his house had been converted into one space and each fireplace/chimney had a bass speaker installed in the aperture (Stereo), utilising the whole chimney as cabinets!

So that's TWO low frequency loudspeakers for the "stereo" low end ?
I guess physics wasn't his strong point then

I spent most of yesterday in a rather splendid recording stuidio, ATC/Genelec monitoring and the rest... but only ONE sub ?

Bass traps
Pseudoscience nonsense from Russ Andrews and chums ...

[Lordgeous]

Could that have been Percy Wilson Technical Editor of The Gramophone for many years?

Thanks for that. Gosh, I think it was. I see from obituaries that he did live in Oxford. My memory is notoriously bad so I hope I haven't done him a disservice with inaccurate technical remembrancies! I do remember being knocked out by the superlative sound of his home system though.

[richardfinegold]

He went a lot further then that! He measured the vibrations.



He's an American audio expert so maybe he hasn't looked at what the BBC is up to in particular. But given his impressive website I wouldn't be surprise if he's looked at "thin walled speaker design". But I'll leave you, or the OP, to dig into his website if they want to look into this in detail.

I think the Bob Ludwig quote went over Mal’s head, Jayne.
I once heard it explained thus. Imagine that a Martian spaceship lands invisibly during a World Cup Soccer finals. The Martians are studying Life on Earth and have noticed that such events are of importance to Earthlings but being unfamiliar with the concept of competitive sport they are trying to figure out why. Using their scientific instruments they measure the following: The rate of photosynthesis of the grass; the amount of Oxygen and CO2 consumed in the stands; the amount of beer consumed; the temperature before and after the match. They then return to base and write their report, as ignorant of the significance of the event as when they started.
Mal, the point is that the known audio parameters that are measurable may only scratch the surface as to helping us determine why something sounds the way it does

[Richard Barrett]

I spent most of yesterday in a rather splendid recording stuidio, ATC/Genelec monitoring and the rest...

This is the kind of thing that alerted me to all the pseudoscientific bollocks invented to sell "high-end" domestic sound equipment: if you go into an actual studio you'll see tangles of pretty ordinary looking cables everywhere, not solid copper wires as thick as your arm; and so on.

[MrGongGong]

This is the kind of thing that alerted me to all the pseudoscientific bollocks invented to sell "high-end" domestic sound equipment: if you go into an actual studio you'll see tangles of pretty ordinary looking cables everywhere, not solid copper wires as thick as your arm; and so on.

Exactly
And (as I'm often banging on about) why buy some overpriced DAC when you can get the RME one that was probably used to record the music in the first place for half the price?

[Bryn]

This is the kind of thing that alerted me to all the pseudoscientific bollocks invented to sell "high-end" domestic sound equipment: if you go into an actual studio you'll see tangles of pretty ordinary looking cables everywhere, not solid copper wires as thick as your arm; and so on.

I would add that such cables are likely to be of the balanced XLR connector variety, rather than with the unbalanced RCAs employed by many 'high end' domestic installations.

[johnb]

Mal, the point is that the known audio parameters that are measurable may only scratch the surface as to helping us determine why something sounds the way it does

"Known audio parameters"? Does that imply there are unknown audio parameters?

That kind of comment makes me distinctly nervous and seems the sort of disclaimer used by the the more way out members of the "audiophile" community.

After all it is physics - and there are only certain variables that relate to loudspeakers, e.g. phase, timing, coherence, frequency response, in-room resonances and decay times, etc.

As for Russ Andrews, I confess that I'm skeptical about some of the stuff he sells.