Im just toying with a concept here.
I notice fairly large amounts of bass coming from some very small bluetooth speakers.
can this be upscaled for a much large woofer?
what are the limitations?
i understand several radiators can be used with one active driver.
could you for instance build a large box (wide and high but not very deep)
with say one active 12inch woofer in the center and surround it with as many 6inch passive radiators as you can fit around it on the front surface.
i understand you would need to adjust weights and find suitable drivers/ passives.
why?
i could spend money on a high quality active woofer, and then use many relatively cheaper passive radiators to make a high fidelity high spl woofer thats relatively small compared to a ported/horned equivalent.
is this conceptually viable and worth pursuing as an idea?
I notice fairly large amounts of bass coming from some very small bluetooth speakers.
can this be upscaled for a much large woofer?
what are the limitations?
i understand several radiators can be used with one active driver.
could you for instance build a large box (wide and high but not very deep)
with say one active 12inch woofer in the center and surround it with as many 6inch passive radiators as you can fit around it on the front surface.
i understand you would need to adjust weights and find suitable drivers/ passives.
why?
i could spend money on a high quality active woofer, and then use many relatively cheaper passive radiators to make a high fidelity high spl woofer thats relatively small compared to a ported/horned equivalent.
is this conceptually viable and worth pursuing as an idea?
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your not wrong, but larger passive systems have proven viable.
i have a peerless xls 10 with a passive thats quite good.
i have a peerless xls 10 with a passive thats quite good.
They actually do produce bass down to 70 Hz.
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Passive radiators are a great choice if you wanted to build a ported box, but could not fit the ports. Acoustically, these box types are similar. A high power 12" subwoofer in a small box with passive radiators is perfectly viable. It requires a beefy woofer and a huge amount of amplifier power though. Sunfire XTEQ 12 is an example. XTEQ Subwoofer EQ DUAL 12" Multivoltage | Sunfire
If you do not need such a small box, it is cheaper to build something with a larger box.
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Yeah, the little bluetooth speakers aren't bad. I keep a Sony SRS-XB12 around, which sounds pretty good. I'll do some measurements and find out exactly what it's doing.
With regards to scaling up the idea, remember that the PRs need to have twice the volume displacement available as the main driver(s). ie, 1x 12" driver needs 2x 12" PRs with the same Xmax, or 1x 12" with 2x Xmax, or 1x 18" with the same Xmax.
If we're still aiming for 70Hz-ish, then the T/S parameters clearly need to be different to a conventional subwoofer.
Chris
With regards to scaling up the idea, remember that the PRs need to have twice the volume displacement available as the main driver(s). ie, 1x 12" driver needs 2x 12" PRs with the same Xmax, or 1x 12" with 2x Xmax, or 1x 18" with the same Xmax.
If we're still aiming for 70Hz-ish, then the T/S parameters clearly need to be different to a conventional subwoofer.
Chris
Those bluetooth speakers and passive radiators seems to be tuned pretty narrow range (one big peak). It gives good efficiency but they sound one notey at the response peak where the best sensitivity occurs.
If size is not a problem, there are better methods than passive radiators to get high efficiency. Like tapped horns.
If size is not a problem, there are better methods than passive radiators to get high efficiency. Like tapped horns.
Tuning the frequency response such that it peaks at the (passive radiator) tuning frequency has another benefit. It allows for more low frequency sound output from a tiny woofer, as the passive radiator keeps the cone excursion of tiny woofer under control. This assumes that sound output is limited by cone excursion capability and not by thermal power handling. I think this assumption holds for 2" woofers, but not for 12" woofers.
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The best bluetooth speakers are doing a lot of tricks:
1) dynamic EQ so they have low bass when the volume isn't loud
2) harmonic synthesizer where harmonics of a tone that it can't play are created to make your brain think its there
3) limiting so the driver/amp are soft clipping and reducing bass extension when pushed
4) Using peaky tuning
5) and in the future stuff like kipple controled sound to get more linear excursion out of the drivers.
I have never used passive radiators as they are a lot more expensive than ports but in theory you can make a bit smaller box as you don't need the port air volume. There is also the advantage of less midrange leakage if the bass driver plays into the midrange.
1) dynamic EQ so they have low bass when the volume isn't loud
2) harmonic synthesizer where harmonics of a tone that it can't play are created to make your brain think its there
3) limiting so the driver/amp are soft clipping and reducing bass extension when pushed
4) Using peaky tuning
5) and in the future stuff like kipple controled sound to get more linear excursion out of the drivers.
I have never used passive radiators as they are a lot more expensive than ports but in theory you can make a bit smaller box as you don't need the port air volume. There is also the advantage of less midrange leakage if the bass driver plays into the midrange.
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Bass drums can have a wide range of tuning frequencies, and of course there'll be harmonics.
I've RTA'd a kick drum with a 16Hz fundamental. The harmonics at 32Hz and 48Hz were at +3dB and +6dB respectively, so realistic reproduction really can require extended LF response.
Chris
I've RTA'd a kick drum with a 16Hz fundamental. The harmonics at 32Hz and 48Hz were at +3dB and +6dB respectively, so realistic reproduction really can require extended LF response.
Chris