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Low Earth Orbit
DIY Audio
Small-ish Home Theater Subwoofer
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<blockquote data-quote="Bennett Prescott" data-source="post: 7356" data-attributes="member: 4"><p>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.</p><p></p><p>[ATTACH]158121[/ATTACH]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.</p><p></p><p><strong>Other goals:</strong></p><ol> <li data-xf-list-type="ol">-3dB at 35Hz or lower (flat to 40Hz)</li> <li data-xf-list-type="ol">Output is more or less irrelevant</li> <li data-xf-list-type="ol">No port noise</li> <li data-xf-list-type="ol">Able to reach max excursion with <1dB port choking</li> <li data-xf-list-type="ol">Reasonable WAF</li> </ol><p></p><p><strong>For power, I am trying to decide between two Powersoft plate amps:</strong></p><ol> <li data-xf-list-type="ol"><a href="http://www.powersoft-audio.com/en/products/amp-modules/digimodis/d-cell504-is.html" target="_blank">D-Cell504 IS Series</a></li> <li data-xf-list-type="ol"><a href="http://www.powersoft-audio.com/en/products/amp-modules/digimodis/digimod-1000-is.html" target="_blank">DigiMod IS Series</a></li> </ol><p>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.</p><p></p><p>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.</p><p></p><p>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.</p><p></p><p><strong>Box Calculations:</strong></p><p>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.</p></blockquote><p></p>
[QUOTE="Bennett Prescott, post: 7356, member: 4"] 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. [ATTACH=CONFIG]158121.vB5-legacyid=6710[/ATTACH]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. [B]Other goals:[/B] [LIST=1] [*]-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 [/LIST] [B]For power, I am trying to decide between two Powersoft plate amps:[/B] [LIST=1] [*][URL="http://www.powersoft-audio.com/en/products/amp-modules/digimodis/d-cell504-is.html"]D-Cell504 IS Series[/URL] [*][URL="http://www.powersoft-audio.com/en/products/amp-modules/digimodis/digimod-1000-is.html"]DigiMod IS Series[/URL] [/LIST] 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. [B]Box Calculations:[/B] 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. [/QUOTE]
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