One day I dream of a beautiful home office or dedicated listening / home theater room with 5.1 surround from large format boxes and enough subwoofer to make you lose control of your bowels. For now, however, I live in a little Boston apartment and have a very compact 2.0 system that is rather lacking in the LF. Considering I happen to work for the greatest loudspeaker component manufacturer on planet earth, and that I have never before built a speaker from the ground up, I thought it was time to rectify that situation. I also thought it would be fun to enlist the forum's help and document the process.
My goal is to build a 2x8" powered subwoofer based on either the 8BG51 or a custom 4-ohm low Fs version (the tradeoff being much higher Vas) of that woofer, spec sheets for both attached. For fun, I would like it to look convincingly like a Clair BT-218.
Other goals:
For power, I am trying to decide between two Powersoft plate amps:
The D-Cell504 IS_p is just enough power. given the expected box tuning I think there is a good chance it will be able to power both 4Ω 8" woofers (1 per amp channel) close to their excursion limits. However, it has a limited DSP, is not networkable, has no AES ins, and is kind of a pain to program since you need a special adapter board. Also I have heard that the hole for the programming ribbon connection whistles, which I'll definitely hear in my little living room.
The Digimod 1500 or 2000 HV IS DSP-4 has plenty of power for either of the woofers, but is about 4x as much money as the D-Cell504. The DSP-4 gives me networking, AES In, a real power limiter (!), and impedance monitoring: all things that will make this sub much more fun for me. The AES is especially nice since I can convert to it straight from the Optical out of my Airport Express and stay digital until Powersoft's converters - which are much better than the ones in my Airport Express and don't force me to make unbalanced signal runs.
So, while I naturally would prefer the DSP-4 (and once you're paying for that DSP the difference in cost between power levels is irrelevant), it takes the cost of the project from "anytime" to "real money". I guess I'll have to think about it.
Box Calculations:
I spent some time in WinISD. It seems I can probably get away with a stiffly built (Ql = 20) 60L box tuned to 35Hz with ports about 10cm in diameter, which will end up being almost 1/3 meter deep. Fortunately I can fake some additional depth on the box just fine. I don't know diddly squat about this part, so maybe I'm missing something critical.
My goal is to build a 2x8" powered subwoofer based on either the 8BG51 or a custom 4-ohm low Fs version (the tradeoff being much higher Vas) of that woofer, spec sheets for both attached. For fun, I would like it to look convincingly like a Clair BT-218.Other goals:
- -3dB at 35Hz or lower (flat to 40Hz)
- Output is more or less irrelevant
- No port noise
- Able to reach max excursion with <1dB port choking
- Reasonable WAF
For power, I am trying to decide between two Powersoft plate amps:
The D-Cell504 IS_p is just enough power. given the expected box tuning I think there is a good chance it will be able to power both 4Ω 8" woofers (1 per amp channel) close to their excursion limits. However, it has a limited DSP, is not networkable, has no AES ins, and is kind of a pain to program since you need a special adapter board. Also I have heard that the hole for the programming ribbon connection whistles, which I'll definitely hear in my little living room.
The Digimod 1500 or 2000 HV IS DSP-4 has plenty of power for either of the woofers, but is about 4x as much money as the D-Cell504. The DSP-4 gives me networking, AES In, a real power limiter (!), and impedance monitoring: all things that will make this sub much more fun for me. The AES is especially nice since I can convert to it straight from the Optical out of my Airport Express and stay digital until Powersoft's converters - which are much better than the ones in my Airport Express and don't force me to make unbalanced signal runs.
So, while I naturally would prefer the DSP-4 (and once you're paying for that DSP the difference in cost between power levels is irrelevant), it takes the cost of the project from "anytime" to "real money". I guess I'll have to think about it.
Box Calculations:
I spent some time in WinISD. It seems I can probably get away with a stiffly built (Ql = 20) 60L box tuned to 35Hz with ports about 10cm in diameter, which will end up being almost 1/3 meter deep. Fortunately I can fake some additional depth on the box just fine. I don't know diddly squat about this part, so maybe I'm missing something critical.
) and can extend the low freq response by making the box "appear" to be twice as large.
