Hi . . . I'd like to build a sealed subwoofer that will hit certain low frequency sound pressure levels. Could somebody please help me understand the characteristics of a driver that would lead to the smallest sealed box size for a given low frequency (f3) and volume displacement?
Assume driver cost and power requirements don't matter. I want to swing +/- 0.15 liter at 40 Hz, so something like a 7" driver with an Xmax of 8 mm would be fine, but I could live with either larger or smaller drivers, if Sd and Xmax get me to that 0.15 liter volume displacement.
I can simulate various drivers all day long using WinISD, but I'd rather understand how to interpret driver specs such that I can identify suitable candidates up front.
To put it another way, what is it about a particular driver that might make it more suitable for a small enclosure? I am familiar with Efficiency Bandwidth Product and its use for determining whether a driver might be better used in a sealed or vented enclosure, but given the fact that I'm willing to throw power at the problem I'm not sure how much I care about that spec. Of course, my ideal driver would have to not melt in trying to achieve that 40 Hz and +/- 0.15 liter spec, either, so maybe I *do* care about power in a roundabout way.
Any hints or links or whatever would be greatly appreciated. Thanks!
Assume driver cost and power requirements don't matter. I want to swing +/- 0.15 liter at 40 Hz, so something like a 7" driver with an Xmax of 8 mm would be fine, but I could live with either larger or smaller drivers, if Sd and Xmax get me to that 0.15 liter volume displacement.
I can simulate various drivers all day long using WinISD, but I'd rather understand how to interpret driver specs such that I can identify suitable candidates up front.
To put it another way, what is it about a particular driver that might make it more suitable for a small enclosure? I am familiar with Efficiency Bandwidth Product and its use for determining whether a driver might be better used in a sealed or vented enclosure, but given the fact that I'm willing to throw power at the problem I'm not sure how much I care about that spec. Of course, my ideal driver would have to not melt in trying to achieve that 40 Hz and +/- 0.15 liter spec, either, so maybe I *do* care about power in a roundabout way.
Any hints or links or whatever would be greatly appreciated. Thanks!
If money is no object the various seas 26lroy drivers are very nice, play sealed in very small volumes but are expensive.
With DSP you can use appropriate drivers with good xmax in too small an enclosure and correct with a Linkwitz transform for a flat frequency response.
That means it practically widens your choice of drivers if you have a certain maximum size in mind.
This might end up calling for much more needed amplifier power though which you should consider.
Of course you can also correct for room resonances you might have, using that DSP. A sub that goes down low might reveal those room resonances and a sealed sub might excite those too.
You can use simple programs like winisd to simulate the frequency response sealed and see what volume you end up with. You can apply Linkwitz transform in that software as well so you get an idea.
That said, there are many threads here where people asked for small sealed sub drivers. You should read those first. There is so much good advice to find here already.
And the choice of drivers is vast.
Have a look at the loudspeaker database too. It allows searching for specific driver criteria like xmax, size, Qts, bad etc. If you know what you want.
With DSP you can use appropriate drivers with good xmax in too small an enclosure and correct with a Linkwitz transform for a flat frequency response.
That means it practically widens your choice of drivers if you have a certain maximum size in mind.
This might end up calling for much more needed amplifier power though which you should consider.
Of course you can also correct for room resonances you might have, using that DSP. A sub that goes down low might reveal those room resonances and a sealed sub might excite those too.
You can use simple programs like winisd to simulate the frequency response sealed and see what volume you end up with. You can apply Linkwitz transform in that software as well so you get an idea.
That said, there are many threads here where people asked for small sealed sub drivers. You should read those first. There is so much good advice to find here already.
And the choice of drivers is vast.
Have a look at the loudspeaker database too. It allows searching for specific driver criteria like xmax, size, Qts, bad etc. If you know what you want.
Something like this driver would work very well in a small sealed sub with a minidsp and would still be cheaper than a seas 26lroy for example:
Pluto sub - Peerles 830668
I have the 830669 from that same line of drivers and they are very nice.
Pluto sub - Peerles 830668
I have the 830669 from that same line of drivers and they are very nice.
Thanks, joensd. I did a search and didn't turn up the direct answer, but that's OK.
So what specs on the Seas drivers lead them to working well in a small enclosure? It seems in general a smaller Vas might be desirable. What about Fs? Should I be aiming for something under 40 Hz and then letting the cabinet air stiffness bring it up towards that 40 Hz mark? Other thoughts?
I really appreciate the help.
So what specs on the Seas drivers lead them to working well in a small enclosure? It seems in general a smaller Vas might be desirable. What about Fs? Should I be aiming for something under 40 Hz and then letting the cabinet air stiffness bring it up towards that 40 Hz mark? Other thoughts?
I really appreciate the help.
Sealed box design routine: Closed Subwoofer Box Equations Formulas Design Calculator Qtc Speaker System Total Q fc Resonance
From this we see that the lower the driver's Qts' and higher the box's Qtc, the smaller it is, conversely, a matching Qts'/Qtc = infinite box size [Vb] and obviously the lower the Vas spec, the smaller the box.
F3 is a function of Qtc, Fc, so work it backwards to find the driver's optimal Fs, Vas, Qts'.
Qts': Qts + any added series resistance [Rs]: Calculate new Qts with Series Resistor
All that said, with relatively inexpensive DSP now a reality, using the biggest driver with sufficient Xmax, desired Fs, you can cram in the desired box size and EQ it flat makes finding a driver a ~trivial pursuit.
. . . and let me point out that both the Seas and Peerless designs referenced in this thread have more Vd than I need. I am really trying to figure out how to drive enclosure volume to an absolute minimum given an SPL and F3 frequency target. Honestly, I'm not even all that worried about fidelity, this is a design exercise to see how far things can go.
Looking at the page GM referenced it appears that minimizing cabinet volume is an exercise in minimizing Vas/alpha, which in turn implies larger ratios of Qtc/Qts. This then implies minimizing fc/fs. What I don't yet know is whether or not I'm caught in a loop!
Looking at the page GM referenced it appears that minimizing cabinet volume is an exercise in minimizing Vas/alpha, which in turn implies larger ratios of Qtc/Qts. This then implies minimizing fc/fs. What I don't yet know is whether or not I'm caught in a loop!
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You come here, you're already down the rabbit hole. 
Not really, for 40 Hz, look to prosound horn drivers with Fs in the high 20s-low 30s, Qts in the low 0.2 range with lowest Vas, then cram it in the box and use DSP to EQ it flat.
The main problem is this much motor isn't cheap, so will probably have to compromise in the low-mid 0.3 range. Again, work backwards using your desired F3.
Not really, for 40 Hz, look to prosound horn drivers with Fs in the high 20s-low 30s, Qts in the low 0.2 range with lowest Vas, then cram it in the box and use DSP to EQ it flat.
The main problem is this much motor isn't cheap, so will probably have to compromise in the low-mid 0.3 range. Again, work backwards using your desired F3.
Another question: what's the deal with the Tang Band subwoofers and woofers? Are they legit? They seem to occupy a spec space that no other manufacturer tries to compete in, which makes me leery.
I built a couple of small boxes with them a few years ago and they seemed to work OK, but I didn't have great measurement capability to verify performance. I also have no idea about quality control or reliability.
I built a couple of small boxes with them a few years ago and they seemed to work OK, but I didn't have great measurement capability to verify performance. I also have no idea about quality control or reliability.
I used this method on TB W6-1139SIF
Simple Trick for Measuring Woofer Stroke / Excursion - YouTube
I used 40 Hz and increased volume until I could hear obvious motor noise then measured the displacement which was about 25mm which would correspond to 2 Xmax (TB quote 11mm). Note Xmax is usally measured from magnet and VC measurements. I agree with this guy it is just part of the picture. If the airflow and suspension has been badly designed and do not match the VC/magnet design then this becomes the limiting factor at higher volumes.
I think this is a good test if you are able to before buying. Just need a camera and some ears.
Simple Trick for Measuring Woofer Stroke / Excursion - YouTube
I used 40 Hz and increased volume until I could hear obvious motor noise then measured the displacement which was about 25mm which would correspond to 2 Xmax (TB quote 11mm). Note Xmax is usally measured from magnet and VC measurements. I agree with this guy it is just part of the picture. If the airflow and suspension has been badly designed and do not match the VC/magnet design then this becomes the limiting factor at higher volumes.
I think this is a good test if you are able to before buying. Just need a camera and some ears.
No, as you already mention yourself, with a DSP it can all be corrected.
An isobaric system is just a acoustic way of doing exactly the same thing.
Maybe only in a bit more extreme case it can help, since you don't have to boost as much. But that would be a very niche situation.
In general you also can't go to small, since a smaller box will always lead to higher distortion. (see explanation on Linkwitz' website)
Honestly I don't know.
On a professional level I have extremely mixed results with them at best.
Their datasheets are just strange, often not providing the right freq resp.
T/S seem to be a big hit or miss.
And a couple of years ago all of a sudden the exactly same products got twice as expensive. (while the rest of the market stayed relativity constant).
Ever since then they have been spending a lot into marketing.
Not to say they are terrible.
I just see most of the time better or cheaper alternatives.
Definitely don't see and agree with the idea that there are no competitors for similar solutions you're talking about.
Except for a very few exceptions here and there.