Gah! Just wrote a long post and got timed out! here goes AGAIN!
So, I have 2 Eminence Beta 12" drivers from Celestion active stage monitors (250WRMS AMPS!)
I want to build these into larger Cabs to use as Subwoofers for my Home theatre.
I have some loudspeaker design experience.
Eminence says these units are designed for Bass guitar and PA and as such they recommend cabs upto 140L (about 5cu feet).
However, after putting figures into WinISD Beta, the plots tell me I could get usuable bass down to 30Hz or lower if I use 275 (10cu feet ish) vented cabs. These are the largest I can accomodate.
I'm not sure how to interpret the other plots but delay increases rapidly around 30Hz. I can get a flatish responce from 70-30Hz andI have plenty of power to play with.
My questions are therefore, is it worth using largest Cab size, or will the quality be severely affected? Mostly I play rock and Movies.....though I do enjoy a bit of Jazz bass too. Is 30ms noticable? Phase goes right off too but I imagine these subs will need to be wired out of phase.
Are there other more complex but smaller cabs that will give me what I want?
I'm confident I can build anything, but not sure if its worth using any curved designs.
I last designed and built 3 way speakers (tasty 6.5" Kevar Audax and seas tweeters) about 15 years ago, so my knowledge may be out of date.
So, I have 2 Eminence Beta 12" drivers from Celestion active stage monitors (250WRMS AMPS!)
I want to build these into larger Cabs to use as Subwoofers for my Home theatre.
I have some loudspeaker design experience.
Eminence says these units are designed for Bass guitar and PA and as such they recommend cabs upto 140L (about 5cu feet).
However, after putting figures into WinISD Beta, the plots tell me I could get usuable bass down to 30Hz or lower if I use 275 (10cu feet ish) vented cabs. These are the largest I can accomodate.
I'm not sure how to interpret the other plots but delay increases rapidly around 30Hz. I can get a flatish responce from 70-30Hz andI have plenty of power to play with.
My questions are therefore, is it worth using largest Cab size, or will the quality be severely affected? Mostly I play rock and Movies.....though I do enjoy a bit of Jazz bass too. Is 30ms noticable? Phase goes right off too but I imagine these subs will need to be wired out of phase.
Are there other more complex but smaller cabs that will give me what I want?
I'm confident I can build anything, but not sure if its worth using any curved designs.
I last designed and built 3 way speakers (tasty 6.5" Kevar Audax and seas tweeters) about 15 years ago, so my knowledge may be out of date.
Well 275 litres is massive. It will be very loud and require not that much power, but very low bass will not be as present as if you used a proper sub driver. A proper sub driver would tend to be fine with a smaller box too.
PA speakers are made for SPL and actually designed not have that low resonance frequency. At normal listening levels they are not that great at subs. OK for music, but really for cabs that size I would be expecting a lot more.
PA speakers are made for SPL and actually designed not have that low resonance frequency. At normal listening levels they are not that great at subs. OK for music, but really for cabs that size I would be expecting a lot more.
After a bit of looking around, its seems I might be better off using them aspart of a full range setup, as a bass/low mid in a smaller cab instead. I'd still be interested in other designs around 140L mark that can extend the bass. I've seen mods done to them, removing the dust cap and possibly using a phase plug. Seems to extend the bass significantly. What about weighting the diaphragm? Is that something recommended these days? Doping?
I can't afford to buy a sub driver, and it seems difficult to ebay these Celestion qxa122's as they were not sold in this country (700 Euros elsewhere!) and no-one seems to know what they are. I don't want to part with them for less than £200. They are fanastic in a very large room/dance floor but useless for home hifi, mids sound very harsh distances less than 20 feet, very lacking in bass. Good for annoying the neighbours and as a guitar combo but that's it. Amps are noisy too but they have a huge amount of gain.
I can't afford to buy a sub driver, and it seems difficult to ebay these Celestion qxa122's as they were not sold in this country (700 Euros elsewhere!) and no-one seems to know what they are. I don't want to part with them for less than £200. They are fanastic in a very large room/dance floor but useless for home hifi, mids sound very harsh distances less than 20 feet, very lacking in bass. Good for annoying the neighbours and as a guitar combo but that's it. Amps are noisy too but they have a huge amount of gain.
I agree. At 274L you can do MUCH better with a proper subwoofer.
My older sonosub was around that size (260L), had a 15 inch Tempest subwoofer driver, tuned to 17Hz, and a response that was pretty flat down to 16 Hz.
With many movies having sub 20Hz content, you'll be missing out on a lot by settling for a PA driver that has little below 30Hz.
Very helpful replies people. I may yet use these as woofers and find something later for sub. At the moment I only have some very poor quality bookshelf speakers as my mains. Can anyone recommend a mid/tweeter combo to use with these as part of a 3 way? I have a single seas h398 going spare, might get another. The Horns currently with in the celestions are just nasty nasty and I cannot stand to listen to them. Even the cheapo bookshelfs sound better. At least I know I'll get punchy bass with these if not Sub. Must say that support for DIY builders is far far better than 17 years ago thanks!
If you had said for general music use, I'm sure the opinion would be different.
As I said, many movies on DVD and Blue-Ray today have a lot of content down to the single digit frequency range. (Granted, most subs don't get that far, and it is felt as pressure waves, not sound...) If you experience it, you'll understand.
I found my old frequency response graph... The top end was cut off as that was were I had crossed it over at around 80Hz.
An externally hosted image should be here but it was not working when we last tested it.
Joe L.
Wow, that is impressive. I never expected to get anywhere close to that. What kind of setup do you have that gives that kind of output? I don't expect I'll be able to match it until my kids have moved out and have no hair left lol!
Actually, I've since replaced that small sub with something more capable...
The driver that made that frequency response in my prior post is no longer manufactured, but it is a Adire Tempest 15" driver. It was in a 260L ported sonotube enclosure. The port was a piece of 6" diameter cardboard tube, somewhere around 24 inches long, tuned to just below 17Hz.
some specs on the Adire Tempest 15" driver:
Parameters
Nom: 2 x 8 Ohm, Power: 750 W, Fs: 18.8 Hz, Qms: 6.7, Qes: 0.4, Qts: 0.39, Vas: 317L, Sd: 779 cm^2, Xmax: 16.4mm, Re: 3.5 Ohms, Le: 2.9 mH, BL: 14.2, Mms: 195 grams, SPL: 89.1 dB @ 1W, 1m
The parts-express Dayton DVC 15" subwoofer is considered to be a clone of the Adire Tempest. (manufactured in the same factory) Dayton Audio DVC385-88 15" DVC Series Subwoofer 295-190
You can see the actual sub that made that frequency response here (260L tuned to just under 17Hz) :
HTGuide Forum - View Single Post - DIY Subwoofer Showcase
but... it was replaced a few years later with this pair of sealed 18" 12.5 cubic-foot subs built into the stage below my screen:
HTGuide Forum - View Single Post - DIY Subwoofer Showcase
Old (small) 15" Adire Tempest sub displaced 2.6L.
New (larger) subwoofers each have a 18" Ascendent Audio Avalanche driver with dual 2 ohm coils, wired in series for a 4 ohm load to the amplifier. Each driver has 6.5L displacement and is down-firing (Total displacement is 13 Liters)
I had to weatherstrip the closet doors in the room even with the smaller sub... the doors would rattle in the frames otherwise.I guess what I'm trying to point out is that home-theater bass in movies is very different than the needs of PA and music. Take a look at the spectrum graphs here:
War Of The Worlds (2005) - Home Theater Forum and Systems - HomeTheaterShack.com There is a ton of content below 30 Hz a PA driver cannot begin to reproduce,
even in kids movies: Finding Nemo - Home Theater Forum and Systems - HomeTheaterShack.com
(The 15" tempest driver seems to sell for between $100 and $125 in used-audio ads) The Dayton DVC is about the same new.
The 18" Ascendent Audio Avalanche drivers are unfortunately also out of production. They were much more expensive, but still under $300 on sale.
Last year I built four of the bass-sticks designed by J Bell. Good to only about 45Hz, but they are for ballroom dance music... and have 8" MCM woofers that were under $30 each. Again, great for PA use and music, not anywhere near as good for home-theater use.
Whatever your budget, watch this forum for ideas. You can find bargain drivers at almost any price level. You basically want a strong motor and as much displacement as you can get. When reproducing loud, low frequencies in movies, there is no replacement for displacement. (large xmax, large BL)
If you are going to the trouble of building something, at least target some decent performance. Perhaps you can sell the PA drivers and use the proceeds for a true subwoofer driver. Whatever you do, making sawdust can be a lot of fun.
Oh yes.. I have no kids... and very little hair, and I love to get immersed in a movie, to where I instinctively reach for the arm-rests on the chair when something un-expected happens to blow up on screen.
Joe L.
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