Hi guys, been a while since I've posted here. Got some iso acoustic isolation pods for my speakers and I was surprised how much of an effect it had on clarity all the way up into the midrange and it got me thinking. How much more resolution could I get out of a driver by using a second opposing driver for force cancellation. Its always been in the back of my head to try it. I had an idea but I'm not sure how effective it would be or what other problems would arise.
What if if I used a concealed driver inside of a sealed enclosure within the speaker (box within a box). I'm absolutely sure this is not a new idea of course. Is that because it doesn't do much? If I could calculate the rolloff of the interior driver due to high frequencies not passing through the box to the outside, if I ran them in series, presumably I could get some of the lower bass to fill in as well. I was thinking of using a driver like the SEAS CA22RNY H1471. If the second driver filled in the low end a little bit better maybe I could get away with using a 1st order crossover and then using a horn up above 1.3khz or so.
Just wondering if anyone has tried anything similar or if you know any preexisting designs that have done similar and how it sounded.
What if if I used a concealed driver inside of a sealed enclosure within the speaker (box within a box). I'm absolutely sure this is not a new idea of course. Is that because it doesn't do much? If I could calculate the rolloff of the interior driver due to high frequencies not passing through the box to the outside, if I ran them in series, presumably I could get some of the lower bass to fill in as well. I was thinking of using a driver like the SEAS CA22RNY H1471. If the second driver filled in the low end a little bit better maybe I could get away with using a 1st order crossover and then using a horn up above 1.3khz or so.
Just wondering if anyone has tried anything similar or if you know any preexisting designs that have done similar and how it sounded.
i hope you're driving a car with a V12 engine because otherwise you may not actually be canceling out all the vibrational forces properly ...
Monitor Audio has a commercial variation that is an elegant way of hiding the push-push woofers.
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dave
dave
Thanks Dave. Yeah I guess I didn't do a good job of explaining what I was thinking. I'm familiar with push-push woofers facing eachother, or even side to side back to back (like the kef blade) but I was wondering about back to back push-push woofers (or would this be called pull pull? perhaps thats the confusion) with one of them being concealed inside the box but still connected (probably with long bolt standoffs going through rubber grommits fitted into the holes that lead to the inside woofer chamber). From a physics standpoint, I'm not even sure that the inside woofer would effectively cancel motion from the outside facing woofer. So this is why I was inquiring. Cheers.
The 3rd one. Except in my mind I was envisioniong the back of the inside woofer not being exposed to the outside woofer. (box within a box)
In each of the "isobaric" configurations in post #7, the cones move the same direction, they double the vibration component compared to a single, while not increasing output potential.
An isobaric configuration allows a slightly smaller box for similar low frequency response.
In a well-braced heavy cabinet, vibration is so little it doesn't amount to much acoustically.
Wasting the cost and output of a woofer to simply reduce vibration is not a cost effective idea, each driver would need twice the excursion for the same output as two, almost four times the expense, while nearly tripling the enclosure volume.
When the woofers are used for low frequencies, placing them on opposite sides of the cabinet to reduce vibration can reduce cabinet cost and weight without reducing output, so is cost effective.
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Ah ok, does that include designs like Kef Blade then?
So if I'm I'm picking up what you're laying down a more cost effective way to reduce cabinet inertia induced distortion would be just to increase the mass of the cabinet ala Eggleston speakers? Another idea on my speaker bucket list is to do a concrete enclosure one day.
The KEF Blade marketing doesn't seem to make too much of cabinet vibration, they probably don't want to throw their front facing woofer designs under the bus 😉
The Blade has different polar response than their front facing series, and seems to be more a diffraction reduction and aesthetic decision that allows use of already developed drivers rather than an anti-vibration driven choice.
The Blade is pushing the upper crossover frequency limit of side mounted woofers, I wouldn't want to go above around 150Hz in opposing woofers myself.
That said, KEF's choice of the Uni-Q coax requires a higher crossover to "keep up" with the four woofers.
Opposing woofers would be a more cost effective way to reduce cabinet vibration, adding weight costs money in construction and shipping.
That said, I have not seen any indication that "cabinet inertia induced distortion" (whatever that is) in any well braced cabinet of typical weight could compare in audibility to other forms of distortion like IMD, diffraction, or polar and frequency response variations.