I want to build a sub for a home theater system. I am planning on using the Dayton 12" Titanic Mk III and the 500W plate amp from Parts Express. Modelling this in WinISD as a ported box gives a box of 3.5 cu. ft. and a tuning frequency of 20.31Hz. Will increasing the box size to 5 cu. ft. and lowering the tuning frequency to 18Hz (to increase low frequency extension) have any negative effects? I will be using this sub with a magneplaner speaker system. Will it be fast enough for these speakers, especially with the modifications to increase the low frequency extention? Any help would be appreciated.
You can alter the box size and tuning in WinISD and answer your own question as far as that goes.
No one can say if the sub will be 'fast' enough as the word 'fast' does not describe anything that a sub woofer does. The only thing about a sub, or any other speaker, that moves and thus could be assigned the term 'fast' is the cone/voice coil assembly, and the speed at which it moves is always precisely that of the frequency of the signal sent to it by the amplifier.
Lastly, moving the Fb from 20 to 18 Hz wouldn't necessarily have a negative effect, but it wouldn't have a positive one either, as your ears would not be able to tell the difference. Even if there were any sonic information available at 18 Hz, and there isn't much, the output differential at 18 Hz from a 20 Hz box versus an 18 Hz box would be perhaps 1 dB, which at 18 Hz you cannot differentiate. Even at 1kHz where the ear is most sensitive differences of 1dB are inaudible to the average person.
www.billfitzmaurice.com
No one can say if the sub will be 'fast' enough as the word 'fast' does not describe anything that a sub woofer does. The only thing about a sub, or any other speaker, that moves and thus could be assigned the term 'fast' is the cone/voice coil assembly, and the speed at which it moves is always precisely that of the frequency of the signal sent to it by the amplifier.
Lastly, moving the Fb from 20 to 18 Hz wouldn't necessarily have a negative effect, but it wouldn't have a positive one either, as your ears would not be able to tell the difference. Even if there were any sonic information available at 18 Hz, and there isn't much, the output differential at 18 Hz from a 20 Hz box versus an 18 Hz box would be perhaps 1 dB, which at 18 Hz you cannot differentiate. Even at 1kHz where the ear is most sensitive differences of 1dB are inaudible to the average person.
www.billfitzmaurice.com
Well, yes, if you're talking about harmonics as opposed to fundamentals, and not coincidentally that is where the harmonics of the human female voice lie, allowing her to be heard by her mate at distances far greater than the average male would prefer, thus being just one more piece of proof the God indeed is a female- or a male with a lousy sense of humor.
A more correct term for speed, would be dynamic range (I think), or rather the speakers ability to differentiate notes very close together. As I understand, smaller diameter and/or lighter speaker cones have a higher dynamic range compared to larger and/or heavier cones. Also closed boxes are better than vented (but you lose the really deep bass in a closed box). I also understand that humans can't hear below 20Hz but we can feel below that frequency and this is why I would like to go as low as possible, in the home theater, without affecting the dynamic range too much. Hope this makes sense.
danbmellow said:
I agree - 'fast' in this sense is really about detail. The pace at which a bass string produces a note is different to the pace at which a kick drum does, 'fast' refers to the speakers ability to produce enough detail to tell the difference. Sealed units are generally recognised at being better at this because of their shallow roll off - but there are some fantastic ported units out there which you would consider to be 'fast' too.
I'm going to make my usual recomendation-forget the box(and 12" woofers)-build an IB subwoofer 2 or 4 -15" woofers in an IB will give you the best bass you'll ever hear-but you have to be able and unafraid of cutting holes in your house
All of what you say is reasonably correct except for one very important thing: almost none of this applies to the frequency range covered by a sub. Build your box with the Dayton 15 according to the manufacturers recommendation, enjoy your system, and stop losing sleep over it. The only point you might consider is closed versus vented purely from the standpoint of cone overexcursion; if you play loud stay sealed. If you want as low as you can go at moderate volumes go vented.
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