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Old 1st October 2013, 09:05 PM   #1
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Default Question about multiple subs in one box.

I slapped together a ported box to use a 8" sub I had kicking around. The box is about 9 x 9.5 x 33" and has the driver on one side and a flared 3" port (6.5" long) on the other. A Kicker DX250.1 is powering it. At 4 ohms it's only rated at 140w. At 8 ohm it's even less but it shakes the car like a pair of 12s are back there.

My question is... How would adding a second identical driver effect the tuning and the sound quality? I know to account for the displacement of the additional driver and may have to adjust the port length. I think now it's tuned to 44hz and plays clearly down to 25~30 with a sweep I found on Youtube. It sounds incredible and I wouldn't want to ruin that but being able to parallel two subs to get 4 ohms might give me a little more output out of it. It's that, or gamble on replacing the current driver with a DVC.
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Old 1st October 2013, 09:08 PM   #2
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One speaker per chamber.
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Old 1st October 2013, 09:09 PM   #3
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Quote:
Originally Posted by Brian Oshman View Post
One speaker per chamber.
What's the reason behind that?
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Old 1st October 2013, 09:13 PM   #4
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Bridge the amp, it will see the speaker as 4 ohms.

Running two or more woofers in the same undivided enclosure will affect the way it operates. It will cause over excursion and distortion and will change the Q since the box is set up for one speaker and the size of the box is based on the parameters of the speaker.

If you want to add more woofers then build a new box with separate chambers.
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Old 1st October 2013, 09:39 PM   #5
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I have no idea what the ts parameters are for this driver. I just built a box sized to fit the car and tuned the port for 44hz. I wasn't expecting much and was blown away when it sounded as good as it did. I couldn't be happier with how it turned out so maybe I shouldn't mess with it.

Wouldn't 2 small speakers in parallel just act like a single larger speaker?

It's a single channel class-d amp.

Last edited by lazzer408; 1st October 2013 at 09:50 PM.
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Old 1st October 2013, 09:57 PM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by lazzer408 View Post
I have no idea what the ts parameters are for this driver. I just built a box sized to fit the car and tuned the port for 44hz. I wasn't expecting much and was blown away when it sounded as good as it did. I couldn't be happier with how it turned out so maybe I shouldn't mess with it.

Wouldn't 2 small speakers in parallel just act like a single larger speaker?

It's a single channel class-d amp.

Hi,

2 drivers will act as though they are in half box sizes tuned to 44Hz.
Given your method it may or may not work depending on the drivers.

rgds, sreten.

Changing the driver is a crapshoot. I'd stick with being lucky.
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Last edited by sreten; 1st October 2013 at 10:00 PM.
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Old 1st October 2013, 11:13 PM   #7
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Quote:
Originally Posted by sreten View Post
Changing the driver is a crapshoot. I'd stick with being lucky.
Your probably right there. The port was tuned that high because I listen to a lot of classic rock. I started with 32hz then 38hz but the kick drum was dominating the bass guitar. At 44hz it much better but I was concerned about over-excursion or the system just not being efficient at very low frequencies. Neither of those problems are present in the vehicle. If it works don't fix it?
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Old 1st October 2013, 11:18 PM   #8
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The woofer works (as in makes sound with the least effort) the least at the tuned frequency. Since you tuned it to your liking you created efficiency.
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Old 1st October 2013, 11:36 PM   #9
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Quote:
Originally Posted by Brian Oshman View Post
The woofer works (as in makes sound with the least effort) the least at the tuned frequency. Since you tuned it to your liking you created efficiency.
Right, but at frequencies above or below the tuned frequency the cone will move a lot more. At very low frequencies of say 20~30hz I was worried about over-excursion especially being just an 8" driver. Although it's tuned to 44hz, it easily played (in the vehicle) down to 20hz on a sweep (without distortion or over-excursion). It's roll off seems to start at about 30hz. This is only using my "ear-dyno" but it sounds good to me.
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Old 2nd October 2013, 01:13 AM   #10
neela30 is offline neela30  United States
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I don't know much about that brand of sub or what bracing and stuffing may be subtracting from the internal demensions of the box but the box may be a little oversized even with it being a ported enclosure. I suspect that it sounds "bigger" since the larger box will extend the low frequency response to a point. The sub was probably designed for a ported enclosure in the first place but I don't know if it is rated for the power going to it.

A sealed, much smaller box (roughly half the size) would increase the power handling and tighten up the bass (less low end).

As mentioned before, one sub per chamber or the subs work against each other dramatically reducing efficiency (in most cases).
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