Hi all,
I'm finalizing my HT this winter and I will be building my speakers soon and I need a bass/subwoofer solution. I started another thread regarding my main speakers which will all be line arrays (cheap ones with old 4" NSB drivers and Apex JR tweeters). I will build most of them as 2 ways and while this might be okay for the surround channels playing down to 80 or 100HZ, the main front channels probably need to be three way. I was thinking on making bass towers to handle all the low end for the front.
I was thinking of doing 3 towers of 4 15" woofers. I found the following 15" woofer for only around 20$. MCM Audio Select 15" Woofer with Poly Cone and Rubber Surround 200W RMS at 8ohm | 55-2974 (552974) | MCM Audio Select
I was hoping it could fulfill two needs.
1. Handle the frequency range below 80 HZ for the front 3 channels.
2. Handle the subwoofer duties in the same time.
All my speakers will be active using the miniDSP platform so I will have an capable way of doing crossover and eq.
Yes, that woofer might not be the best but shouldn't it be capable enough if its 12 of them?
Is this feasible? Can the towers do both duties and if so how low could I expect them to play?
Thanks.
I'm finalizing my HT this winter and I will be building my speakers soon and I need a bass/subwoofer solution. I started another thread regarding my main speakers which will all be line arrays (cheap ones with old 4" NSB drivers and Apex JR tweeters). I will build most of them as 2 ways and while this might be okay for the surround channels playing down to 80 or 100HZ, the main front channels probably need to be three way. I was thinking on making bass towers to handle all the low end for the front.
I was thinking of doing 3 towers of 4 15" woofers. I found the following 15" woofer for only around 20$. MCM Audio Select 15" Woofer with Poly Cone and Rubber Surround 200W RMS at 8ohm | 55-2974 (552974) | MCM Audio Select
I was hoping it could fulfill two needs.
1. Handle the frequency range below 80 HZ for the front 3 channels.
2. Handle the subwoofer duties in the same time.
All my speakers will be active using the miniDSP platform so I will have an capable way of doing crossover and eq.
Yes, that woofer might not be the best but shouldn't it be capable enough if its 12 of them?
Is this feasible? Can the towers do both duties and if so how low could I expect them to play?
Thanks.
Hi.
Its a cheap driver and needs about 10 cu ft per driver
sealed, and that gives you a f-6dB of around 38Hz.
(Though I'd say around 5 cuft is the best choice.)
Each tower would need to about 40 cu ft which is massive.
Around 2.5 cuft per driver and and a Linkwitz Transform
with very big amplifiers will work better at some extra cost.
12 15"ers with 6mm Xmax should be enough for most people.
rgds, sreten.
Its a cheap driver and needs about 10 cu ft per driver
sealed, and that gives you a f-6dB of around 38Hz.
(Though I'd say around 5 cuft is the best choice.)
Each tower would need to about 40 cu ft which is massive.
Around 2.5 cuft per driver and and a Linkwitz Transform
with very big amplifiers will work better at some extra cost.
12 15"ers with 6mm Xmax should be enough for most people.
rgds, sreten.
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yea 10 cuft per driver will be a massive tower! Anything between 2.5-4 cuft per driver might be feasible though since I will have these behind a transparent movie screen and won't be seen. Linkwitz transform can be done with the miniDSP. When you say very big amplifiers how big are you referring to? Will 300w per tower be enough?
Are you planning to have them shipped from US to France? Have you thought that through? The shipping costs will far outweight any savings on the drivers. I don't order from MCM because even shipping to Canada is so expensive!
International shipping might indeed be to expensive but I have not yet investigated it. I arranged for LCL shipping of all my NSB drivers from PartsExpress many years ago so its not a dead end problem for me. But if I can find an equivalent type of driver here for similar funds it will indeed simplify things.
That's 75w per driver. Make it more like 200w per driver and I reckon you're on to something.
When it comes to bass, its all about headroom.
Chris
125dB peaks at 20Hz? You might even hear it.
Note it was 800w per tower, so 2400w total. If you want to get loud and low in a small box, you gotta throw power at it.
And with 12 of 15" drivers each doing 6mm of one-way travel, you get 115dB @1m @20Hz, assuming a sealed box.
Chris
Yes HT build that also will include 7 line arrays. Its in a purpose built room (two de-cupeled walls, well insulated) and it will contain a lot of bass treatments as well.
Yikes. 800w per tower sure does add up. I keep it in mind though. If I can cover that full range at 125db I'll be very happy. Probably won't ever use it but who knows.......
No, 800W TOTAL. In fact, in that box size vented, you will run out of Xmax at around 800W divided amongst all the drivers.
I just tried modeling a sealed box alternative, I'm still running out of Xmax ~900W divided amongst all these drivers in sealed boxes 5^3 per driver worth of sealed. So.. hmmm...
How much box space can you afford?
I just tried modeling a sealed box alternative, I'm still running out of Xmax ~900W divided amongst all these drivers in sealed boxes 5^3 per driver worth of sealed. So.. hmmm...
How much box space can you afford?
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Actually I can probably afford around 3.7 ft3 per driver. I was thinking towers of 1ft deep 2 feet wide and 6.5 ft high. This way they will match my line array dimensions.
Thanks for modeling them for me. I have not actually learned how to do that!
But if that volume will play the low range at 125db why would I need bigger boxes? Quality of sound?
Load them isobarik?
They do have an Fs of 32Hz so there is always the option to run a passive radiator to tune them down to 22Hz and high pass them at 20Hz.
I saw it done once about 20 years ago, a guy used two isobarik groups (4 woofers) which uses the same air space required as one woofer. Two isobarik groups equal the same efficiency and impedance (wired series/parallel) as one woofer would in the same sized box. Asked him why he would do it and the answer was push/pull distortion reduction and the woofers handled 4 times the power. The odd ball way he did it gained 6dB from that extra power handling in the same box size and he claimed it reduced distortion.
The passive radiator allows low tuning without taking up the space required from huge ports. Three 92dB isobarik subs at 800 watts total in theory should be in the low 120dB range I'd guess. At least it would fit in the room and you won't have any issues with Xmax running 12 woofers at 800 watts.
They do have an Fs of 32Hz so there is always the option to run a passive radiator to tune them down to 22Hz and high pass them at 20Hz.
I saw it done once about 20 years ago, a guy used two isobarik groups (4 woofers) which uses the same air space required as one woofer. Two isobarik groups equal the same efficiency and impedance (wired series/parallel) as one woofer would in the same sized box. Asked him why he would do it and the answer was push/pull distortion reduction and the woofers handled 4 times the power. The odd ball way he did it gained 6dB from that extra power handling in the same box size and he claimed it reduced distortion.
The passive radiator allows low tuning without taking up the space required from huge ports. Three 92dB isobarik subs at 800 watts total in theory should be in the low 120dB range I'd guess. At least it would fit in the room and you won't have any issues with Xmax running 12 woofers at 800 watts.
I modeled based on 200ft^3, or nearly 17ft^3 per driver. With 3.7ft^3 per driver....
This is at 1 meter, and doesn't take into account room loading. With lots of EQ this would work fine. The port size isn't bad either, only need about an extra 2ft^3 worth of space dedicated to the port for the whole system to get that tuning.
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hi,
a few years back when the house was built I made two holes in the concrete floor to prepare for an IB subwoofer. There are two holes at 40*50 cm each. They are venting into my crawlspace. Would it be feasible to run these woofers as a poor mans IB? Then I could build two towers with 6 woofers each and have three woofers in oposite directions to cancel out vibrations.
Feasible?
a few years back when the house was built I made two holes in the concrete floor to prepare for an IB subwoofer. There are two holes at 40*50 cm each. They are venting into my crawlspace. Would it be feasible to run these woofers as a poor mans IB? Then I could build two towers with 6 woofers each and have three woofers in oposite directions to cancel out vibrations.
Feasible?
That said....
Take the same 3.7ft^3 x 12 drivers, but divy up the same box space amongst 6 drivers instead (7.4ft^3 per driver) and you get the result below...
(maxPe was ~525W in this case)
Notice that for less than half the power the bottom end is just as loud as 12 drivers in an equal amount of sealed box space.
3.7ft^3 per driver kills efficiency really bad in this case.
Take the same 3.7ft^3 x 12 drivers, but divy up the same box space amongst 6 drivers instead (7.4ft^3 per driver) and you get the result below...
(maxPe was ~525W in this case)
Notice that for less than half the power the bottom end is just as loud as 12 drivers in an equal amount of sealed box space.
3.7ft^3 per driver kills efficiency really bad in this case.
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The point of sealed + eq is that you can put the drivers in a cabinet not much bigger than the drivers, provided you have the amplifier power to make up for the inefficiency of the drivers in tiny boxes.
If you can get a single driver to run out of power handling and excursion at about the same time, you'll be using the smallest cabinet possible (per driver, you'll need to multiply it all up for more drivers), while getting full output. Anything else is bigger than it needs to be.
Chris
If you can get a single driver to run out of power handling and excursion at about the same time, you'll be using the smallest cabinet possible (per driver, you'll need to multiply it all up for more drivers), while getting full output. Anything else is bigger than it needs to be.
Chris
Dropping the box size to 2ft^3 per driver will accomplish what Chris is talking about, however the results would not be positive IMO:
2db loss of maximum output through most of the bottom end, and twice the power requirement accomplish the lower output levels.
It sounds to me like you have room to build 3x15ft^3 boxes. To me, that screams 3 drivers, not 12. I would be looking at buying 3 decent 18" drivers. You'll get better bottom octave performance with lower power requirements.
2db loss of maximum output through most of the bottom end, and twice the power requirement accomplish the lower output levels.
It sounds to me like you have room to build 3x15ft^3 boxes. To me, that screams 3 drivers, not 12. I would be looking at buying 3 decent 18" drivers. You'll get better bottom octave performance with lower power requirements.
So long as power handling limits are not reached, any given driver will have the same maximum low frequency output in any sized sealed cabinet. Its simply a function of cone area and Xmax.
The problem is that very small boxes are very inefficient at low frequencies, so you have to throw power at them to get the cones moving to get the output you want.
Chris - simply pointing out another method of doing the same thing.
Hi Chris,
The comparison was 2ft^3 sealed vs 3.7ft^3 vented per driver Sorry I should have been more clear.
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The more I sim those woofers, the more I would lean towards using 6 rather than 12. When limited to 45ft^3 for all of the woofers, 12 does nothing but increase initial costs, increase power requirements, and increase long term operating costs compared to 6. Once it's EQed out flat the additional drivers do nothing but waste more energy.
The comparison was 2ft^3 sealed vs 3.7ft^3 vented per driver
Sorry I should have been more clear.-------------------------------
The more I sim those woofers, the more I would lean towards using 6 rather than 12. When limited to 45ft^3 for all of the woofers, 12 does nothing but increase initial costs, increase power requirements, and increase long term operating costs compared to 6. Once it's EQed out flat the additional drivers do nothing but waste more energy.
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