Discussion arising from Geddes loudspeaker

[planet10]

Originally posted by dlr
That's nothing more than the pressure in the box for constant radiated power for given box volumes.

Which -- barring a bit of arithmetic gymnastics is exacty what i said.

The only important point is that if the resonant frequencies are raised, they may be more easily damped, since most damping materials are more effective at higher frequencies.

It is not the only thing. Raising the panel resonance frequency also means that the resonance is less likely to get excited in the 1st place. Push it high enuff and the natural damping in the panel material is suffiicent.

If you have some other point of which we're unaware, I don't see it. Raising resonances above the passband of the driver/XO used isn't new, IIRC that was one of the points Gedlee (or someone in the thread) made early on.

No one is disputing that this technique is new... the paper i quoted in from 1972, and alot of this stuff was well understood decades early.

Earl's 2 points that brought this part of the discussion up, where that the vertical brace in the Fonken was oriented incorrectly and that a preferred bracing was a set of point braces, both points which are incorrect based on the research done all that time ago, and information that has been readily available for a looonnnggg time.

He did make some very good points about how MDF is not really stiff enuff to make an adequate brace, and that a brace with its centre cut-out is not as effective, yet we see MDF shelf braces all the time so it is clear that these simple guidelines have still not become pervasive.

dave

[ShinOBIWAN]

Dave the cabinets I build are more dead than anything I've seen from yourself, no doubt about it. What's funny is that yes I don't follow those simple guidelines you keep banging on about either.

Yours is the true way of course. Can't be doing with folks like that.

[gedlee]

Originally posted by planet10

Earl's 2 points that brought this part of the discussion up, where that the vertical brace in the Fonkon was oriented incorrectly and that a preferred bracing was a set of point braces, both points which are incorrect based on the research done all that time ago, and information that has been readily available for a looonnnggg time.

He did make some very good points about how MDF is not really stiff enuff to make an adequate brace, and that a brace with its centre cut-out is not as effective, yet we see MDF shelf braces all the time so it is clear that these simple guidelines have still not become pervasive.

dave

Dave

Please don't assume that because I quite arguing that I cncede to your points. I still stand by my claims.

[MJL21193]

Originally posted by ShinOBIWAN
Dave the cabinets I build are more dead than anything I've seen from yourself, no doubt about it. What's funny is that yes I don't follow those simple guidelines you keep banging on about either.

Yours is the true way of course. Can't be doing with folks like that.

No question your boxes are dead silent, but maybe it's actually doing more than is necessary. I wasn't being sarcastic above (everyone expects that maybe) when I said I'd re-program myself. I see now what Dave has been saying.
It's so simple. With truly effective bracing, you drive resonance up to the point where, given the energy in the box at that frequency, it can't be excited.
There will be no need for extra panel damping, since there is next to nothing to damp. Brilliant, actually.
I owe Dave an apology for badgering him and not giving him enough credit.

HMM, if I didn't see that, maybe there IS something to this Enabl stuff...

Nah, I won't go THAT far.

[planet10]

Originally posted by ShinOBIWAN
Yours is the true way of course. Can't be doing with folks like that.

There are many ways to skin a cat. I have no doubt that your speakers have dead cabinets.
Your methodology is near the brute force (but gourgeous) end of the spectrum, i try to play at the elegant/minimalist end.

dave

[Kevin Haskins]

I love MDF...it is cheap, easy to machine and available everywhere. I don't hear any huge differences just substituting baltic birch for MDF.

In my opinion, much of the dead cabinet hoopla is overrated. Its another one of those topics like cables that people will endlessly debate but there are far more important design considerations to focus upon.

I'll disagree with you on this one Dave.

[planet10]

Originally posted by gedlee
Please don't assume that because I quite arguing that I concede to your points. I still stand by my claims

In designing my speakers I'm just taking advantage of the established research & experimental data from those who laid the ground work long before me.

And by talking about it, i'm pointing out that this work has all been done for anyone that might benefit.

dave

[planet10]

Originally posted by MJL21193
No question your boxes are dead silent, but maybe it's actually doing more than is necessary. I wasn't being sarcastic above (everyone expects that maybe) when I said I'd re-program myself. I see now what Dave has been saying.
It's so simple. With truly effective bracing, you drive resonance up to the point where, given the energy in the box at that frequency, it can't be excited.
There will be no need for extra panel damping, since there is next to nothing to damp. Brilliant, actually.
I owe Dave an apology for badgering him and not giving him enough credit.

Thanx John. It is very fullfilling seeing someone put all the connections together and have the light go on. My on-going evangilism for plywood (or other light, stiff, damped panels) makes much more sense in light of the entire systems approach that i employ.

dave

[ShinOBIWAN]

Originally posted by planet10


There are many ways to skin a cat. I have no doubt that your speakers have dead cabinets.
Your methodology is near the brute force (but gourgeous) end of the spectrum, i try to play at the elegant/minimalist end.

dave

Then why keep saying MDF is unsuitable for loudspeaker cabinets? I'm not looking for compliments on my own work, that wasn't the point at all. The point is that success with MDF isn't rare, the data backs it up as a suitable material and it has additional benefits such as easy machining, easy to finish and cheap.

[MJL21193]

Originally posted by planet10


Thanx John. It is very fullfilling seeing someone put all the connections together and have the light go on. My on-going evangilism for plywood (or other light, stiff, damped panels) makes much more sense in light of the entire systems approach that i employ.

dave

My lights are on now, for sure. I can be a bit daft about some things at times.

In all fairness, the same results can be had with MDF as the panel material. My lack of confidence in it as a brace material hasn't changed. MDF panels with plywood bracing would be a good compromise.
I still don't believe there is an audible difference between these materials.