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Hi .. I'm not finding info using Pro speakers (15"-18") for home theater.
Using extended bass alignment and large ported cabinets they seem like good candidates. Want into the low 20's.
Can anyone recommend woofers that would work? I know they will be limited on power. I can balance Fb and Vb to power limitations with UniBox.
Last thing ... I believe most PA speakers can be run close to Xmax limits and maintain linearity. Is this generally true?
Zene
Follow Ups:
Get yourself a Volt R3853 and stick it in a suitable transmission line.
You'll end up with something very similar to the PMC XB3 sub for substantially less money.
These are very highly regarded and in a test of 'super subs'(ie 10k and up) I once found on the net it was the only one which did not exceed 10% distortion at 16Hz. It also measured the least power compression. Read PMCs client list; if its good enough for those guys (Lucasfilm, Sony etc, it seems many if not most movie soundtracks are mixed on PMCs) its good enough for me and hopefully you too!
If that doesn't move enough air for you try Volts 18" R4504.
Pro-sound woofers tend to be poor candidates for HT subs. Fs values are too high, Qts values too low, xmax and xlim insufficient.
Bill ... What might be wrong with forcing Fb lower in a big box as long as Xmax was not violated at a reasonable SPL output? I have modeled several and they look OK on paper (UniBox) down to mid 20's.
Zene
With so many drivers available that work very well as subs I don't see the point in using a driver that's a compromise at best.
Don't want to jump in the middle of this... But for a reasonably good sized HT room - say 4500-5000 cuft. a good pro woofer can work fine... you need a large box though and a quiet vent for the BR load. The high power handing of Pro woofs work to your advantage even if the smaller xmax's don't - the visual impact of four 15's per side or even four 15's under the AV screen in impressive. 20 Hz is overrated. But Bill, you are right - there a soooo many woofs to choose from for a DYI project.
Not a compromise at all. I knew better to come here for any thinking.
HT boys are no help either. They go with the "follow the crowd", also.
No offence Bill, your wisdom is usually much appreciated.
Zene
Zene,It's got little to do with a lack of thinking, quite the opposite, Bill and many of us here have gone through the math, the experimenting, the listening, let alone the "thinking".
Frankly, you are acting badly.
Prosound woofers could be put into alignments like you wish, but you compromise performance more than already is done in the usual course of loudspeaker design. Impulse response, phase response, group delay suffer more when you try.
Your best bet is to alawys use a driver that is purpose designed.If you want to find out what you get by designing a sub this way, go ahead and try it-if you find the results acceptable, you're done.
Best regards,
The day I start following the crowd is the day I stop designing speakers for a living.Pro-sound sub drivers are optimized for the frequency range where pro-sound operates, 35Hz and higher. HT sub drivers are optimized for where the demands of LFE are highest, 35Hz and lower. When I tell you don't bother trying to use pro-sound drivers for HT it's for the same reason I tell musicians don't bother trying to use HT and autosound drivers for pro-sound applications: because it doesn't work. You don't have to take my word for it, you've got box modeling, confirm it for yourself.
What about "The Almighty Subwoofer"? http://member.newsguy.com/~stigerik/almighty/The Almighty Subwoofer uses the JBL 2226 and it does require active filters. But I've modeled quite a few high excursion 15" and 18" drivers that work as well or better than the JBL 2226 in similarly designed enclosures. My current favorite 'bang for the buck' driver is the Peavey Low Rider 15" ($176 @ Parts Express). In a 250 liter box tuned to 20-22Hz it requires a 6db shelf filter to get a flat response. A single Low Rider will do 110db or so at the stated Xmax.
Except for the need for an active filter, what is so bad about subwoofers built like this? Do they sound bad? Does the modeling not work out right? I haven't built anything like this, but I was planning on doing something like the Almighty Subwoofer here soon. I'd like to know why it wouldn't work. My own interest in this is because I was looking at building some high efficiency home theater speakers using pro sound drivers, and a couple subwoofers with pro sound drivers seems to me like they would be a better "match".
Ben .. I knew there would be someone out there to at least question the theory, not oppose it off hand. The JBL 2226 looked very bad on paper and so did the P.Audio clone of it. 15" Pro speakers have too high Fs, but P.Audio 18" Challenger Series looked good in 260 L which I think it really takes to get good deep solid bass, not 38.5 mm excursion from a 12" woofer, 2345 watts input in a 1.63 cu ft box, a port that whistles "Dixie" and boosted like crazy to even try to get 20hz. That's nonsense. It takes big to do big bass correctly. Been to a concert lately?
Model the C18-600LF and C18-650EL and have a look. Think 18's are too big, 20hz is 55 feet long. http://www.loudspeakersplus.com/html/paudio_18_subwoofers.html
Yes Bill, I know it takes full Xmax to reach 110dB, but they should run all day long without harm, and that is roughly 5mm with only 100 watts.
Want more dB or cut excursion a bit? Add another. I do sympathize with those that have space problems. It's not my fault that I do have the room (no wife). The space is there if you want it unless the room is 8 x 10.
Ben (others), you might want to read what Steve has to say about his LLT shelved designs. Just because it's shelved does not mean it must be boosted to get flat. WinISD and UniBox are not too savvy when it comes to acoustics. If done right the room will flatten that right out.
Zene
"Yes Bill, I know it takes full Xmax to reach 110dB, but they should run all day long without harm, and that is roughly 5mm with only 100 watts."In room my Tempest loaded THT horn loaded sub does 110dB at 20 Hz with one watt. I'll pass.
The in-room performance of that cab is adequate, but it's an awfully large and expensive speaker. It does prove that pro-sound drivers can be used to 20 Hz, but it also proves that it takes one gargantuan cabinet to do it. Using drivers with fs in the 20 Hz range similar performance can be realized from cabinets half the size and cost of this one.
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