How do they do that?

Posted by: Tony Lockhart on 08 September 2001

Just a silly thought that entered my head after a few beers.... How does a speaker drive unit produce different frequency sounds at the same time?
Tony
Posted on: 08 September 2001 by garyi
I have had many an argument about that. How the hell cana cone of eight inches produce the sound of a voice, drums and a bass guitar at the same time, surely the bloody thing would explode!
Posted on: 08 September 2001 by Don Atkinson
after a few beers.... How does a speaker drive unit produce different frequency sounds at the same time?

Probably the same way as it did before a few beers!

Like your ears (and mine), and the recording mike, I don't think that speaker drive units are conscious of different frequencies. They all just capture, or reproduce the convoluted, aggregated result of the combination of sounds (frequencies, tones etc)by distorting in peculiar ways.

Your brain (but not mine), and an audio-spectum analyser, might be able to separate out the combination into simple frequencies. And I think some of us try to do this when we auditon new kit. But we're less likely to do it after a few beers!

Cheers

Don

Posted on: 08 September 2001 by Tony Lockhart
I think I'll try whisky next.
Tony
Posted on: 08 September 2001 by Don Atkinson
I think I'll try whisky next

Careful!!

Next you'll be asking 'how do the orchestral sounds know which microphone to go to, left or right?'

Now they might manage this ok for stereo, but just think of the confusion for these poor sounds when trying to sort themselves out in full pro-logic or 5.1 home cinema systems. Confused in = confused out?

Cheers

Don

Posted on: 09 September 2001 by Cheese
quote:
might be able to separate out the combination into simple frequencies
Hmm, I doubt it. AFAIK, every sound on this earth (even a scientifically produced 1kHz-frequency) is in itself a harmony of several sounds - a bit like elements, molecules, atoms, subatoms etc.

We listen to infinity everyday, folks big grin but I still don't have a clue how sound reproduction works in the first place !

Is Andrew W around ?

Cheese - may all beings be happy smile

Posted on: 10 September 2001 by Greg Beatty
...reading in Listner a year or two ago about a type of distortion that is caused by virtually all conventional speakers. It happens because higher frequences are being produced by a cone that is moving to produce the lower frequencies. This introduces sortof a dopler effect for the higher frequencies.

The writer wrote this in the context of hearing a prototype dem of a speaker circuit that was designed to remove this type of distortion. He claimed the difference was obvious and very significant. He went on to claim that this soon-to-be-patended technology would be standard on all speakers within a few years.

Does anyone know what has become of it?

- Curious GregB

Insert Witty Signature Line Here

Posted on: 10 September 2001 by Steve B
Ok, so lets suppose you used 2 drive units to produce those 2 different frequencies. Wouldn't the sound waves emanating from each one interact in the same way they would if they came from the one drive unit?

Even if they didn’t, wouldn’t your ear drums suffer from the same Doppler effect of the one drive unit?

Am talking crap?

Steve B

Posted on: 10 September 2001 by Arye_Gur
I can tell you how Naim engineers build the speakers :
quote:
... Naim's engineers dance naked around Stone Henge every night praying for favourable sound quality from the Druid gods (however appealing a notion this may be)
.

If you doon't agree with this quote, please address bam...

Arye

Posted on: 10 September 2001 by Don Atkinson
Steve B,

Quote Am talking crap?

Possibly. (but high quality nevertheless)

AFAIK:-

To generate the Doppler effect, the source of the sound needs to be moving towards (or away from) the listener, as well as emitting the sound.

The usual example is an express train blowing its whistle. The whistle is the sound source and the train is the thing that is moving it. The sound of the whistle changes (=distortion) as the train approaches, passes then disapears.

If part of a single speaker cone is emitting high frequency sound (=the whistle), but at the same time that bit of cone is itself moving as part of a large scale bass excursion of the cone (=the train), then I guess you would have the sort of Doppler effect (on the high frequency bit of the sound) that Greg was talking about.

You wouldn't get that effect with two speaker cones side by side, in this case you would probably get some sort of mutual inerference -(please don't ask for a description of mutual interference!)

Cheers

Don

Posted on: 10 September 2001 by Greg Beatty
...for saying it more clearly than I did.

I have moved and not unpacked everything, but I will see if I can locate the said issue of Listener tonight.

Anyone else have this issue handy?

Anyone else care red face

- GregB

Insert Witty Signature Line Here

Posted on: 10 September 2001 by Mike Hanson
I don't have the issue handy, but I do recall various mentions of it in the hi-fi press about a year ago. A device was created by Kimber (the cable people), that was supposed to have reduced the problem somehow. Many people suspected it would be licensed and incorporated into speaker designs from many different companies, but I haven't heard anything more about it for quite some time now.

-=> Mike Hanson <=-

Posted on: 10 September 2001 by Martin Payne
quote:
Originally posted by Greg Beatty:
...I will see if I can locate the said issue of Listener tonight.

Anyone else have this issue handy?


This distortion mechanism is described in Martin Colloms' book 'High Performance Loudspeakers'.

It applies specifically to a single drive unit which is reproducing a note with large excursions (i.e. bass) and another higher note.


quote:
AFAIK, every sound on this earth (even a scientifically produced 1kHz-frequency) is in itself a harmony of several sounds - a bit like elements, molecules, atoms, subatoms etc.


Actually, a sine-wave is the fundamental constituent of all sound (much like an atom is the indivisible unit of a chemical element).

All other sounds are composed of combinations of sine waves, with varying volume levels and phase relationships.

cheers, Martin