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Old 7th March 2016, 08:49 PM   #1
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Default Building Compact Subwoofer with 8 inch speakers

Hi guys,

I'm new to building speakers. My church, sits 100 - 150 people, needs a compact subwoofer that will be placed under stage (in an 24 in. x 13 in. opening) in the center. The stage is not very large and has no room for a 15 - 18 inch subwoofer. I have attached a photo of the stage.

After doing some research and talking to technical support at parts-express.com, looking into building a very compact subwoofer using two 8 inch BC 8FG64 woofers (600 watt 8 ohm each) using two 12 in. x 12 in. x 12 in. cabinets from Parts-Express.

Will I get enough bass from these speakers? If so, what other parts (crossovers, high pass filters, etc) would I need?
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Old 7th March 2016, 09:14 PM   #2
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How low of a frequency do you need to hit? That driver seems to be more of a midbass driver, with an f3 near 80Hz by my calculations. They certainly have the power handling though.
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Old 7th March 2016, 09:18 PM   #3
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What does the main PA look like? - Those look like some serious wedge monitors for vocal use, so I'd expect a fairly hefty main system to reflect this.

IMO, a pair of 8"s in a room that big won't help much. Put them in a fairly big TH tuned quite high, and you might hear them from the back. Those small sealed boxes won't help the drivers.
You'll need an amplifier, and (presumably) a feed from the mixing desk. Something like an NU3000DSP will do nicely - a few hundred watts per side, and all the crossovers etc built-in.

Chris
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Old 7th March 2016, 09:27 PM   #4
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Is the stage hollow all the way back. Can't help wondering if you view the slot you have as the port you could fit something meaty in there.Either that or behind the plants and in front of the drummer isolation unit. (I really want to photoshop animal from the muppets in there).

Last edited by billshurv; 7th March 2016 at 09:46 PM. Reason: spelling
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Old 7th March 2016, 09:39 PM   #5
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Exactly billshurv! If there is more depth than 12", then a BP4 is possible with a 15" or more.
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Old 7th March 2016, 10:59 PM   #6
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Quote:
Originally Posted by Jensen567 View Post
How low of a frequency do you need to hit? That driver seems to be more of a midbass driver, with an f3 near 80Hz by my calculations. They certainly have the power handling though.
Thanks for the info! I was hoping for 50Hz. I thought these speakers would work as a subwoofers based solely on it's frequency range.
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Old 7th March 2016, 11:06 PM   #7
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Quote:
Originally Posted by chris661 View Post
What does the main PA look like? - Those look like some serious wedge monitors for vocal use, so I'd expect a fairly hefty main system to reflect this.

IMO, a pair of 8"s in a room that big won't help much. Put them in a fairly big TH tuned quite high, and you might hear them from the back. Those small sealed boxes won't help the drivers.
You'll need an amplifier, and (presumably) a feed from the mixing desk. Something like an NU3000DSP will do nicely - a few hundred watts per side, and all the crossovers etc built-in.

Chris
Hi Chris,
The mains are two EAW FR129z speakers. Each box has 12 inch woofers and a 1 inch HF driver. Speaker is 500 watts each.
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Old 7th March 2016, 11:07 PM   #8
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Quote:
Originally Posted by billshurv View Post
Is the stage hollow all the way back. Can't help wondering if you view the slot you have as the port you could fit something meaty in there.Either that or behind the plants and in front of the drummer isolation unit. (I really want to photoshop animal from the muppets in there).
Hi,

That area of the stage is at least 2 feet deep.
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Old 7th March 2016, 11:11 PM   #9
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1. 8" drivers are likely not going to produce enough bass to keep up with those stage monitors

2. You're likely to get a nice notch in the response due to the subwoofer being located that far from the back wall. Measure that distance, then the "notch" frequency is going to be 345/4*d.

3. I suggest trying out (maybe renting) a small sub and placing in that location first to see how it sounds, before committing to a design.

4. Consider locating the sub (or subs) high on the wall near the ceiling if you don't have space for it on or in front of the stage.
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Old 8th March 2016, 02:31 AM   #10
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Quote:
Originally Posted by Jensen567 View Post
How low of a frequency do you need to hit? That driver seems to be more of a midbass driver, with an f3 near 80Hz by my calculations. They certainly have the power handling though.
I forgot to mention that I was planning to add a 2 inch in diameter, 7 inch long port to each cabinet. I don't know if that changes anything though but thought to share the missing information.
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