Quick question - Joe Akroyd of Royd audio, covered the back of the midbass drivers with some kind of material. I've read about this technique before but can't remember the details. The thing I'm most interested in is what it would do to the thiele small parameters?
I suppose I could get a driver out of the shed and do some experiments, but thought I'd ask here first (because it's easier).
I suppose I could get a driver out of the shed and do some experiments, but thought I'd ask here first (because it's easier).
David Weems, in one of his designs, stapled fibreglass tightly over the back of a woofer to provide damping.
This allowed a reduction in the optimum volume of a ported enclosure by lowering the Q of the woofer.
He stated that this gave a controlled, natural sounding bass response.
This allowed a reduction in the optimum volume of a ported enclosure by lowering the Q of the woofer.
He stated that this gave a controlled, natural sounding bass response.
also lowers sensitivity. Someone wrote an article about this back in the 50s, but IIRC there wasn't much detail, maybe a couple of graphs. Of course that was before TSPs, best thing to do is try it & measure.
Also, see post 30 here:
Enclosure for high Q driver
Also, see post 30 here:
Enclosure for high Q driver
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'Audio' Mar 1965 p22:
AUDIO - Consumer audio and music magazine from 1947 to 2000.
don't know that it'll be much help, but the ads from that time are interesting
AUDIO - Consumer audio and music magazine from 1947 to 2000.
don't know that it'll be much help, but the ads from that time are interesting
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It's a simple tradeoff, but hard to model. There are too many variables.
Easier to change treatments and measure.
In so-called aperiodic enlosures there are so many ways to implement your stuffed port-between two chambers, a la the big Dynacos, betwen box and room, behind driver, twixt it and the box, around the box perimeter(pseudo-cardioid), etc...
If you look in an old console, you'll see this technique used a lot.
Easier to change treatments and measure.
In so-called aperiodic enlosures there are so many ways to implement your stuffed port-between two chambers, a la the big Dynacos, betwen box and room, behind driver, twixt it and the box, around the box perimeter(pseudo-cardioid), etc...
If you look in an old console, you'll see this technique used a lot.
Thanks guys. I only asked because it's the nearest thing I can find to the Lockwood Tannoy aperiodic shelf (a material covered shelf between the driver and port). There's a guy over at the artofsound forum that built some very nice cabinets for his 15" Tannoy monitor golds, but is suffering with some bass boom.
Tips & Trucs (luidsprekers), Nederlands Forum over Oude Radio's
It says that linen cloth was tightly wrapped around the frame to reduce the resonance by about 6dB. Later on they used an air pocket behind the dustcap which was able to reduce it by about 10dB.
It says that linen cloth was tightly wrapped around the frame to reduce the resonance by about 6dB. Later on they used an air pocket behind the dustcap which was able to reduce it by about 10dB.
Just occurred that this trick could work well for the open baffle guys when drivers are too high Q and boomy.
Eminence Alpha 15A spring to mind...
Eminence Alpha 15A spring to mind...
