I've just started reading about subwoofer design and I'm full of dumb questions. I've tried googling but it's difficult to find specific questions answered, as you can imagine.
If I'm looking to build a bass solution for a home theater and I'm already considering a setup involving both 2x18" drivers and 2x10" drivers, and if I have a preference for low frequency extension, low group delay, and all those other good things... Do I really need to build the individual cabinets as large as the Vas indicates? My understanding is that building a cabinet at lower-than-Vas simply means that the driver can't extend all the way to Xmax which I probably don't care about since I'm not interested in max SPLs in a home setting.
If I were just building one then I could see it mattering more, but with several and with having the bass range split between smaller and larger woofers, wouldn't that free me up to be a bit more conservative in the size of the [sealed is my preference] enclosures?
I'm assuming I'd still want to hit the goal of Qtc of .707, though... Or is that also flexible when it comes to having multiple subs where they can support each other?
If I'm looking to build a bass solution for a home theater and I'm already considering a setup involving both 2x18" drivers and 2x10" drivers, and if I have a preference for low frequency extension, low group delay, and all those other good things... Do I really need to build the individual cabinets as large as the Vas indicates? My understanding is that building a cabinet at lower-than-Vas simply means that the driver can't extend all the way to Xmax which I probably don't care about since I'm not interested in max SPLs in a home setting.
If I were just building one then I could see it mattering more, but with several and with having the bass range split between smaller and larger woofers, wouldn't that free me up to be a bit more conservative in the size of the [sealed is my preference] enclosures?
I'm assuming I'd still want to hit the goal of Qtc of .707, though... Or is that also flexible when it comes to having multiple subs where they can support each other?
For sealed, you can put them in as small a box as you want now that relatively cheap DSP can correct it to flat/whatever response with the trade-off being [much] reduced efficiency, so having enough power to hit Xmax may be required just to get modest output.
Then there's the rapid heat rise [I^2T] on any 'sustains' that will cause further 'one note' peaking, so at the extremes you'll have to make compromises that further reduce efficiency/BW.
Room modes chop up bass, so a lot depends on room modes and where the subs are and IME before modern electronics that it takes different Qt, so quickly switched to very low tuned vented [aka EBS alignments nowadays] and 'critically' damped the vent to dial them with the 'Click Test': Click Test | GM210 | Flickr
Then there's the rapid heat rise [I^2T] on any 'sustains' that will cause further 'one note' peaking, so at the extremes you'll have to make compromises that further reduce efficiency/BW.
Room modes chop up bass, so a lot depends on room modes and where the subs are and IME before modern electronics that it takes different Qt, so quickly switched to very low tuned vented [aka EBS alignments nowadays] and 'critically' damped the vent to dial them with the 'Click Test': Click Test | GM210 | Flickr
Quick note on EQ: more power into a speaker = more flux modulation in the motor = more harmonic distortion.
Otherwise, I'd weld a steel plate over the cone and drop kilowatts in there.
I do wonder, though, about the wisdom of splitting up the LF range. Instead of 2x 18" and 2x 10", I'd probably go for 4x 12" or 4x 15".
Chris
Otherwise, I'd weld a steel plate over the cone and drop kilowatts in there.
I do wonder, though, about the wisdom of splitting up the LF range. Instead of 2x 18" and 2x 10", I'd probably go for 4x 12" or 4x 15".
Chris
Biggest downside with a smaller cabinet is you will get quite some compression distortion.
There are quite some articles about it, Linkwitz also divided quite some words on his website about it.
Depending how small you make the cabinet, this can get quite substantial.
But, yes, besides that one should watch the max power.
Although that also heavily depends on the context.
Hmm, it's my understanding that DSP can do wonders correcting for compression, just not the [considerable] distortion due to heat rise, but with multiples this can be dealt with if enough are used and/or reduce its HF BW.
As for Linkwitz, I haven't read much of his work beyond the LR XOs, but I assume it predates what a dbx system recently proved to me how HIFI/SQ it can turn a real mess of a large multi-way system in a disaster of a room, so for now stand by my assertion that at least sealed alignments can be reduced considerably when appropriate drivers, DSP system is used.
As for Linkwitz, I haven't read much of his work beyond the LR XOs, but I assume it predates what a dbx system recently proved to me how HIFI/SQ it can turn a real mess of a large multi-way system in a disaster of a room, so for now stand by my assertion that at least sealed alignments can be reduced considerably when appropriate drivers, DSP system is used.
You can't correct for compression distortion, aka the compression of the air that will get more significant in a smaller box.
This distortion is also very easily measurable.
Well, very technically, you can compensate, with a bunch of very smart and clever algorithms, which absolutely non of those kind of DSP's support.
And only to some extend, since that compression has a non-linear part in it.
Anyway, to put it in simple words, a smaller box will give more distortion.