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Old 8th October 2015, 04:19 AM   #1
ReDress is offline ReDress  Canada
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Default A Newb Question About BSC and Multiple Woofers

Hey everyone,

I've been learning about BSC for a while now and was wondering...(Hopefully, the answer to this question isn't too obvious) if one employs multiple woofers, does that negate the need for proper BSC?

Seeing as how you have a drop of about 6 db as a result of the baffle, yet we have an increase of about 6 db as a result of the doubling of woofers in parallel.

Really, just looking for someone to confirm this thought (It would certainly alter my design thought process...)

But I digress, hopefully you can guys help me out with this
It's all appreciated

Much love/Many thanks in advance, everyone.
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Old 8th October 2015, 04:45 AM   #2
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if the 2nd woofer is crossed over at the baffle step frequency, that's correct
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Old 8th October 2015, 05:48 AM   #3
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And why .5 woofers are so popular with some of us
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Old 8th October 2015, 12:52 PM   #4
keilau is offline keilau  United States
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Quote:
Originally Posted by ReDress View Post
Hey everyone,

I've been learning about BSC for a while now and was wondering...(Hopefully, the answer to this question isn't too obvious) if one employs multiple woofers, does that negate the need for proper BSC?

Seeing as how you have a drop of about 6 db as a result of the baffle, yet we have an increase of about 6 db as a result of the doubling of woofers in parallel.

Really, just looking for someone to confirm this thought (It would certainly alter my design thought process...)

But I digress, hopefully you can guys help me out with this
It's all appreciated

Much love/Many thanks in advance, everyone.
The increase in efficiency of 2 parallel woofers is uniform across the whole woofer frequency range. The baffle step lose cause a drop slope toward lower frequency and no drop near the mid range.

You still need the BSC with parallel woofers. I just did a MTM speaker update with new woofers. The ARTA measurement confirmed the baffer step analysis using Jeff Bagby's tools. (Real baffer step and no BS-******** there.)

I am learning BSC recently myself. A whole bunch of fellow members on this forum offered a lot of useful comments to help me out. The link below is on a bookshelf DIY and the BSC issue, not the MTM I mentioned earlier.

The crossover for a modest DIY bookshelf speaker project

One of the things pointed out to me is that I did not need to compensate for the full -6dB drop of the baffer step. It is more likely in the -3 to -4.5dB range, dependent on the room and speaker placement. I found the -4.5 value worked best for my situation.

Last edited by keilau; 8th October 2015 at 01:14 PM.
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Old 8th October 2015, 03:27 PM   #5
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If the cross to the woofer from the mid matches the baffle step frequency then you can sort of compensate with greater efficiency from the woofer. That's basically the biggest stipulation. Other than that you don't even need two woofers to raise the efficiency, you can just use a woofer with 3-4db higher sensitivity than your mid if it's at the baffle step frequency or at least close. I would say if you're crossing within 20-30% of the battle step frequency you should be fine doing that.
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Old 8th October 2015, 06:38 PM   #6
keilau is offline keilau  United States
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Quote:
Originally Posted by maggiesnmacs View Post
If the cross to the woofer from the mid matches the baffle step frequency then you can sort of compensate with greater efficiency from the woofer. That's basically the biggest stipulation. Other than that you don't even need two woofers to raise the efficiency, you can just use a woofer with 3-4db higher sensitivity than your mid if it's at the baffle step frequency or at least close. I would say if you're crossing within 20-30% of the battle step frequency you should be fine doing that.
You are correct that people do not use dual woofer to increase efficiency. It is done to improve power handling and polar dispersion. There are many roads that leads to Rome. The final design is always a trade-off on what the speaker designer wants.

Two 7" woofers will have the same piston area as a single 10" woofer.

A single woofer with higher efficiency design usually means more restricted bass extension (higher resonance frequency, Fs).
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