Can someone double check this sub modeling?

I am a newbie! Need to make sure I am getting the correct numbers here. Unibox is giving me fits.

It's a 105 Liter sealed enclosure.

Looking to use 2 Peerless 850146 in it. The way it's modeling for me it shows about -16dB at 20Hz. Is that in room?


Also I'm using the PE 300-792 plate amp. Will this 120 watt sub amp be able to drive 2 of those Peerless wired in parallel decently? Or do I need more juice?

Thanks!
 
Greets!

Box programs assume aneochoic half space, i.e. buried flush with the ground plane out in a huge flat field, so in-room response won't be anything like it down in the lower octaves due to room modes/misc. losses. Expect a sawtooth looking response instead. Since we are amplitude oriented creatures, we tend to only hear the peaks down low as long as the nulls aren't too broadband, so expect a somewhat more powerful output than the program predicts, though it still won't 'sound' very loud due to our hearing curve. FWIW, using some measured specs I get -15 dB/20 Hz so I guess you have a 'handle' on Unibox. ;)

With 120W you're right at the Xmax limit down low, so looks fine, with well over 100 dB/20 Hz/m peak capability depending on positioning/room size even with some thermal power compression, so unless you're trying to reach DD/DTS reference in a HT app or split all the drywall joints with organ symphonies (been there, done that :() it should be adequate.

GM
 
I actually will be building 2 of them. 2 of those Peerless per side, in 2 105 liter enclosures so I can have "stereo" bass. From what I've modeled, stereo subs will give me *much more* output potential, and seems to "smooth out" the frequency response even more.

I'm still not certain what drivers I'll end up using, it's just those 850146 are really good "bang for the buck" woofers, and have a really good reputation. A single Vifa MA26 (twice the $ though)subwoofer yielded slightly better extention capabilities in my sealed cabinet. But, with less output potential and also less "coolness factor" of 2 woofers per side (these subs will double as stands for my satellites ala Wilson Watt/Puppy).

I'm still learning too!! ;)
 
I actually will be building 2 of them. 2 of those Peerless per side, in 2 105 liter enclosures so I can have "stereo" bass. From what I've modeled, stereo subs will give me *much more* output potential, and seems to "smooth out" the frequency response even more.

I'm still not certain what drivers I'll end up using, it's just those 850146 are really good "bang for the buck" woofers, and have a really good reputation. A single Vifa MA26 (twice the $ though)subwoofer yielded slightly better extention capabilities in my sealed cabinet. But, with less output potential and also less "coolness factor" of 2 woofers per side (these subs will double as stands for my satellites ala Wilson Watt/Puppy).

I'm still learning too!! ;)
 
I actually will be building 2 of them. 2 of those Peerless per side, in 2 105 liter enclosures so I can have "stereo" bass. From what I've modeled, stereo subs will give me *much more* output potential, and seems to "smooth out" the frequency response even more.

I'm still not certain what drivers I'll end up using, it's just those 850146 are really good "bang for the buck" woofers, and have a really good reputation. A single Vifa MA26 (twice the $ though)subwoofer yielded slightly better extention capabilities in my sealed cabinet. But, with less output potential and also less "coolness factor" of 2 woofers per side (these subs will double as stands for my satellites ala Wilson Watt/Puppy).

I'm still learning too!! ;)
 
Greets!
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>Would that mean that you could use one peerless 850146 in a 50 to 60 litre sealed box,build 2 of them (with an amp each) and run them in stereo - getting similar results - but better because its in stereo.
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Correct, or just use one big amp.........
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>Also - why use the 850146 and not one of the sub speakers eg 830452 ?
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The latter appears to be designed for auto and/or bandpass apps, so not really all that well suited for music/HT apps.
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>I actually will be building 2 of them. 2 of those Peerless per side, in 2 105 liter enclosures so I can have "stereo" bass. From what I've modeled, stereo subs will give me *much more* output potential, and seems to "smooth out" the frequency response even more.
====
Hmm, a three-peat posting......caffeine overdose perchance? ;)

I guess I could have used some when I posted yesterday though, I forgot to halve the power level to 120W/pair, so with only 60W/driver the low end for two drivers is pretty anemic below 30 Hz if there's not a lot of room gain. With four drivers/two 120W amps though, you should have an adequate amount of SPL for all but 16 Hz organ notes and really low special effects.

Anyway, adding a second 'sub' system only adds 3 dB, which is barely audible down low. Still, the midbass 'slam factor' is right up there when you need it.

Right, 'stereo' subs do allow for positioning them to average out room modes somewhat, which can subjectively sound louder even though they may not be quite as loud when measured.
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>But, with less output potential and also less "coolness factor" of 2 woofers per side (these subs will double as stands for my satellites ala Wilson Watt/Puppy).
====
To ~cancel out rocking coupling motion issues at high excursion a bi-polar layout is preferred, which unfortunately zaps the 'coolness factor', so like Wilson, a really rigid/massive construction is required for best performance.

GM
 
GM,
Triple post was crazy, I did have Red Bull this morning!

As for the bi-polar configuration, I have read that as well, but "coolness" will have to prevail and I'm using an extra thick 1.5" baffle and also bracing internally to firm them up as you suggest.

Now you have me worried about the plate amps. I don't want to "rob" performance and got them for a really good deal which was why I bought them ($49 each!). I have 7 days left to return them if I want to opt for something more, but , I'll need spend 5 times that amount to get, say the two of the 200 watt jobs. The room is 17' wide by 30' deep, FYI.

Hmmmm......
 
Thanks guys, I have always wanted to build a pair of subs- maybe this will be a good incentive to get me going.
I have looked at the sub amp modules {Wes components code s400w}- 400 watt into 4 ohms with remote control that sells for $259 Aud, aprox $200 U.S each - this seems to be too cheap to be of any quality ? I guess the best way is to try it and see.
 
Greets!

Depending on their various system designs, this may be true for them, or if you parallel two drivers off the same amp, but when you add separate systems of the same impedance like we're talking about here, there's only a 3 dB gain due to a doubling of pressure: 10*log10(10^P1/10)+10^(P2/10))

GM
 
I must disagree. Unfortunately I can't remember any other sources (than genelec.com) that discusses this issue:

When two subwoofers are positioned close to one another mutual coupling is the fortunate by-product. This is due to the long wavelengths, associated with low frequencies, causing constructive superimposition. For mutual coupling the subwoofers must be place within ½ a wavelength of one another (85Hz upper crossover frequency ½ wavelength is approx. 2m). For example, two subwoofers give a 6dB increase in acoustical output at the listening position - see table below.

Total number of subwoofers SPL increase compared to a single subwoofer
1 0.0 dB
2 6.0 dB
3 9.5 dB
4 12.0 dB
 
Greets!

OK, let's try this another way........

You get up to ~ +3 dB/doubling of cone area assuming they are <WL/pi of each other, not the 1/2WL they say, so as frequency falls, there's increasing overlap, ergo increasing gain. Visualize it this way, draw two circles so that they just touch. This puts them ~WL/pi from each other. Over distance they will sum a very minor amount in a room due to reflections, but the theoretical +3.01 dB won't occur until they are ~completely superimposed on each other. IOW the distance between them is so small compared the WL being reproduced that they appear ~as one radiator.

So where does this other theoretical ~ +3 dB come from?

GM
 
I can't seem to find any theoretical explanation for the 6 db increase but it has been mentioned on several web pages. Here's a few web pages I bumbed into.

http://www.bullysubs.com/design_phil.html
http://www.audio-pro.nl/produkten/brochures/db/CenEseriesconfiguraD95.pdf
http://www.avforums.com/forums/archive/index.php/t-22754.html
http://www.linkwitzlab.com/thor-measmt.htm

I don't know anything more about this issue than what I've read on the internet. Everyone knows that internet is full of bs so I might very well be wrong about this.
Be that as it may, in any event it would be nice to know the truth. :)