Small speakers that sound like big ones
- Thread starter ossy
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irb
pfm Member
My guess would be that the cause was more likely to do with reflections than with the woofers humming along. After all, if woofers can act as passive radiators, they would presumably do it at the woofer/box fundamental resonance, and that would surely be at a frequency that is difficult to localise.
S-Man
StrivingON
Seems to be a lot of guessing and presuming in your reply.
Everything that is not (over)damped can resonate. Just depends on the frequency.
When my door rattles due to low bass output, it's very easy to hear where it's coming from... that's how I know it's the door - confirmed by holding the door and the noise stops.
Ever wondered why speaker manufacturers invest so much effort into cabinet design to stop them singing along?
RobGordon
Well-Known Member
Off the back of this thread I picked up some JPW Mini Monitors cheap locally. The hype on these is unjustified (well using my amp anyway). The people saying "no bass" are right, and all round the modern Wharfedale Diamond 220s trounce them. In case anyone was wondering.
Tony L
Administrator
Agree entirely. The most disastrous example I’ve heard was just a little Peavey guitar amp. If it was in the room the whole soundstage collapsed, what was 3d just flattened and became 2d. I successfully blind-tested it with a friend decades ago.
PS My assumption is the LS3/5As would sound better again had I removed the Tannoys from the room, but that is obviously not easily done!
I bought a Ruark Vita 50, which is a rebadged MJ Acoustics 50. Probably not the best sub in the world, but it fills out the bottom end nicely, making those mids and highs sparkle. Not filtered, by the way- the Dyns bass units are still in the equation. Cost me £80 a few years back. Maybe try a BK Acoustics Gemini 2 to test the water?
irb
pfm Member
Of course I'm guessing and presuming - I wasn't in your room to hear what you described.
I'm just trying to comment on what is more or less likely, and I tried to keep my tone non-dogmatic.Yes, everything in a room will have a tendency to vibrate. But of all the things in the room, the audio gear, and especially the speaker drivers, are just about the only stuff that is deliberately designed to have a minimal resonant signature in the audible range. Hence my post 78. (And hence why I'm pretty sure that the whole single-speaker dem room thing was just a marketing ploy.)
Of course, there's still the fundamental box/woofer resonance (one frequency for a sealed box, or two for a vented enclosure). But could the resonance(s) of an undriven woofer really be excited sufficiently by another speaker, such that audible sounds are emitted in sufficient quantities to modify the total response of the system? It really seems very unlikely to me. A bass radiator (which has no voice coil to provide damping) moves in response to the pressure inside a loudspeaker enclosure. A room is much bigger than a speaker enclosure (even a Tannoy
) and the pressure variations are correspondingly much lower. Also any movement of an undriven woofer would be damped by its magnetic circuit. All in all, it seems most unlikely that undriven woofers would resonate enough to be audible.
S-Man
StrivingON
Of course I'm guessing and presuming - I wasn't in your room to hear what you described.
Yes, everything in a room will have a tendency to vibrate. But of all the things in the room, the audio gear, and especially the speaker drivers, are just about the only stuff that is deliberately designed to have a minimal resonant signature in the audible range. Hence my post 78. (And hence why I'm pretty sure that the whole single-speaker dem room thing was just a marketing ploy.)
Of course, there's still the fundamental box/woofer resonance (one frequency for a sealed box, or two for a vented enclosure). But could the resonance(s) of an undriven woofer really be excited sufficiently by another speaker, such that audible sounds are emitted in sufficient quantities to modify the total response of the system? It really seems very unlikely to me. A bass radiator (which has no voice coil to provide damping) moves in response to the pressure inside a loudspeaker enclosure. A room is much bigger than a speaker enclosure (even a Tannoy
An undriven speaker has no electrical damping (Qes), only some mechanical damping (Qms).
Vented box speakers have 1 resonant frequency, not 2.
irb
pfm Member
Maybe I expressed myself poorly.
I still don't think Tony's undriven Tannoys could boost the bass of his LS3/5as. I can't see any mechanism by which this could occur. If you still think otherwise, do you have any thoughts on how it could work?
(Incidentally, I have owned LS3/5as in the past, and there were tracks on which the bass extension was improbable, like Tony describes. I had no other speakers in the room.)
irb
pfm Member
Good point. I think Bob Carver did something like this is his ALS speakers, with a view to generating a feedback signal. Of course, if the cones move a little in response to the movement of the air around them (just as all sorts of other stuff in the average room does), that doesn't necessarily mean they are in turn generating further audible air movement. They are essentially acting as (inefficient) microphones.
To generate sound, without electrical input, they would have to be made to resonate. And my suspicion is that there will be many things in the average room that are more inclined to resonate than undriven speaker drivers, which are deliberately designed to not have an audible resonant signature.
PS Extra, undriven speakers within a room will reflect sound, of course. They make make a significant different that way, especially if they are large.
When I was a kid I got a 'Be An Electronics Engineer' kit from Philips filled with components. You could build everything, one was a telephone between two rooms where the two small speakers where used as microphones, while also being used as speakers. So it would be a surprise if a speaker (that's not connected to a driving amp) did NOT generate a voltage.
As been said above, everything in a room can 'rattle' along with the sound in the room, every physical object has a at least one resonance frequency. I doubt though that a HiFi speaker would be worse than a rack of CD's or flimsy plaster sheet walls.
S-Man
StrivingON
The Tannoys have a resonant frequency at approx 40Hz. The issue with resonance is that it stores energy and releases it later (think about a ruler twanged on the edge of a table).
The energy released later will change the envelope of the sound, IME this is perceived as fuller bass. It may not be easily measurable as increased SPL.
irb
pfm Member
Yes, I understand that resonance means stored energy, thanks.
The thing is, how much energy is being absorbed by a woofer from the room? And how much of that energy is stored and released later? (Bear in mind that speakers are very inefficient transducers/microphones.) I think the amounts are likely to be very small, and I suspect that the only resonating things in a room that will make an audible contribution to the total sound will be things with very high Q resonances. Speakers are designed to have very modest Q resonances, which is why it seems to me that they are among the least likely things in a room to 'sing along'.
Clearly I'm not going to persuade you, though.
S-Man
StrivingON
Yes, I understand that resonance means stored energy, thanks.
The thing is, how much energy is being absorbed by a woofer from the room? And how much of that energy is stored and released later? (Bear in mind that speakers are very inefficient transducers/microphones.) I think the amounts are likely to be very small, and I suspect that the only resonating things in a room that will make an audible contribution to the total sound will be things with very high Q resonances. Speakers are designed to have very modest Q resonances, which is why it seems to me that they are among the least likely things in a room to 'sing along'.
Clearly I'm not going to persuade you, though.
I will ask my pal with a PhD in acoustics, at the weekend.
If he doesn't know...
irb
pfm Member
In the meantime, here's an old Stereophile discussion, with both sides of the argument represented: https://www.stereophile.com/content/controversy-single-speaker-dem-myth
S-Man
StrivingON
I asked my pal (inventor of the priciple behind the Kef KC62 drive unit control). He said that I am right. He did add that the effect of the passive radiator is unpredictable, it could absorb some frequencies whilst augmenting others.
His overall conclusion was "remove unused speakers from the listening room and then they can't have any effect on the sound". Hard to argue with that logic!
irb
pfm Member
Carl Sagan: 'One of the great commandments of science is, "Mistrust arguments from authority." ... Too many such arguments have proved too painfully wrong. Authorities must prove their contentions like everybody else.'