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Old 20th February 2006, 08:47 PM   #1
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Default small passive subwoofer? am i crazy

Ok, I am trying to put together a small 2 channel setup for my tiny living space(10'x10'). I currently have two Bose bookshelf speakers powered by an Adcom GFA-535. I was thinking i could augment this tiny setup with a small passive subwoofer that would also be powered by the amp. I have a .5 cuft mdf box that i was thinking about putting an 8" dayton woofer into (ported). I guess my question is, is this a viable option for such a setup? I was also wondering what effect my small living space would have on the sound of any woofer, and could a custom woofer can be tuned accordingly.
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Old 21st February 2006, 12:30 PM   #2
rabbitz is offline rabbitz  Australia
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This would end in tears so take another route.

With a passive you have to build a crossover and it's hard to get the levels right. Buy a small PE plate amp like the 300-792 or 300-802 to go with your idea and you will be laughing as you can blend the SPL to suit your mains, crossover to suit your mains plus running them via speaker level, you can use the mains as satellites or run via the amp's pre outs.

Just do your driver, box and port homework and all will be well.
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Old 21st February 2006, 12:59 PM   #3
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I totally agree with Rabbitz, but a bandpass box (can vary bandwidth and sensitivity depending on design) may be of use if you insist on limiting yourself with a passive system.
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Old 21st February 2006, 09:34 PM   #4
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Thanks for the responses. I was trying to avoid another amp, I guess, to avoid more amp distortion, but it wouldn't be an audible difference anyway. The powered option does have definite advantages, and it's economical as well. I'm new to this, so I'll continue to research my options. Also, is it a common problem when WinISD says my port diameter and length should be 2.5" x 3' just to achieve a vent mach of .19? Do I have to sacrifice frequency response, right now i'm at the speaker spec of 28 hz.
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Old 22nd February 2006, 12:50 AM   #5
simon5 is offline simon5  Canada
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Yes it's a common problem, small boxes need very long ports.

Use a larger box, or use a passive radiator.
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Old 22nd February 2006, 12:43 PM   #6
rabbitz is offline rabbitz  Australia
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.... or try tuning a bit higher to shorten the port. Depends on how low you want it to go... <30Hz or <40Hz, music or HT.... all about compromises. Maybe sealed might be worth a look.

Remember that the volume of the port and driver has to come out of the box internal volume which makes it smaller again. You can always use an external port and get creative like Collo .


Once thing I didn't mention before is when you use an existing amp, there is a problem getting a mono mixed signal for a sub. You can't do it via speaker level and has to be done in the pre amp stage at line level. Another reason for a PE plate amp.
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