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Old 09-08-2013, 11:16 AM
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IB sub and speaker in same enclosure help

Ok, so Earmark had lead me on to check my install for a possible error to my set up. I have under the observer seat 1 7.7" JL and 1 10" JL IB5 both installed in the walkway on the observer side. He told me you can't have them in the same space because it will cause sound issues from the one. I wasn't sure at the time but thought they were in separate compartments. But they are not. They occupy and use the same air. I have since turned the 7.7" speakers off in the front via turning down the input control on the amp.

I need suggestions to fix this. I can't relocate my sub without reupholstering the sides.

Here is a photo.
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Old 09-08-2013, 11:36 AM
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Originally Posted by Traxx822 View Post
Ok, so Earmark had lead me on to check my install for a possible error to my set up. I have under the observer seat 1 7.7" JL and 1 10" JL IB5 both installed in the walkway on the observer side. He told me you can't have them in the same space because it will cause sound issues from the one. I wasn't sure at the time but thought they were in separate compartments. But they are not. They occupy and use the same air. I have since turned the 7.7" speakers off in the front via turning down the input control on the amp.

I need suggestions to fix this. I can't relocate my sub without reupholstering the sides.

Here is a photo.
If you can make a small-ish enclosure for the smaller driver, you can eliminate the problem. This can be made form whatever material you find, whether MDF with polyester resin coating (that's the resin used for fiberglass when epoxy isn't used), PVC pipe with a cap, etc. If the 7" is crossed over high enough, the internal volume won't be as critical as if it wasn't crossed over at all, or if the crossover was set to a lower frequency. An 8" PVC elbow with some kind of flange would increase the internal volume without protruding as far into the space behind the speaker.
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Old 09-08-2013, 12:36 PM
MLA MLA is offline
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As large as that enclosure is, I think the effect the woofer will have on the full-range will be minimal, compared to enclosing the 7.7 full-range. That locker is probably 4+ ft2, not counting the passages to the other parts of the boat. Its totally wide open as opposed to a smaller, more air confined enclosure.
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Old 09-08-2013, 12:46 PM
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As large as that enclosure is, I think the effect the woofer will have on the full-range will be minimal, compared to enclosing the 7.7 full-range. That locker is probably 4+ ft2, not counting the passages to the other parts of the boat. Its totally wide open as opposed to a smaller, more air confined enclosure.
Proximity matters, too. The woofer will still modulate the sound coming from the smaller driver and that will show up as certain sounds being muddy, sounding like they're jittery and affecting some sounds via phase cancellations. If the woofer is capable of extreme excursion, this is more likely.
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Old 09-08-2013, 01:10 PM
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Proximity matters, too. The woofer will still modulate the sound coming from the smaller driver and that will show up as certain sounds being muddy, sounding like they're jittery and affecting some sounds via phase cancellations. If the woofer is capable of extreme excursion, this is more likely.
I understand the principal and effects completely. Closing the full-range in a too small of an enclosure will effect its mid-bass, so its the lesser of 2 evils. Which will have the least negative effect. The ideal fix is a large enclosure behind the 7.7
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Old 09-08-2013, 01:42 PM
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I understand the principal and effects completely. Closing the full-range in a too small of an enclosure will effect its mid-bass, so its the lesser of 2 evils. Which will have the least negative effect. The ideal fix is a large enclosure behind the 7.7
You could download a program like WinISD and, using the parameters of the 7.7, model the enclosure to see what effect a variety of enclosure volumes will have on mid-bass.

What frequency is the HP crossover setting?
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Old 09-08-2013, 02:14 PM
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From direct experience, I can tell you that any enclosure smaller than a net 1.0 cu.ft. will have an impact on the midbass of the IB 7.7" speaker. Not only will you hear a difference with the speaker played in isolation but you will see a dramatic reduction in the 7.7" excursion on heavy midbass material. Keep in mind that with a smaller enclosure, like a pod for example, that most of the internal displacement is occupied by the speaker leaving very little remaining air.
The large boat cavity shared by the IB 7.7" and IB sub is very compliant. If the two speakers are two feet apart then the sub's affect on the 7.7" will be substantial as the 7.7" becomes a sympathetic radiator for the sub. This is problematic in two respects. The sub and 7.7" intentionally reproduce different bandwidths. The modulation of the 7.7" by the sub will be out-of-phase to a degree (180 degrees +/- the stored compliance of the boat cavity). And that constitutes muddy sound at higher volumes. In this case, the negative influence of the isolation pod is still the lesser of the two evils.
If there is considerable distance between the two speakers and the cavity is expansive, then four feet or more apart may not justify the isolation pod as the fix is worse than the original problem.

David
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Old 09-09-2013, 08:14 AM
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Wow thanks for the replys guys. As you can see the speakers are a mere inches apart. When I have the 7.7" turned off and the IB running medium volume to loud volume the 7.7" moves in and out. Earmark said to check that way in the other thread.

jimn, the crossover is set on 12 I believe. There is only three options. 0,12 & 24.

I bet I could make something out of fiberglass. Trying to figure out how to secure it without driving screws through the other side.

Sent from my HTC One using Tapatalk 2
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Old 09-09-2013, 08:33 AM
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I guess I could flange the ends and drive the screws that hold the speakers in through that. I only need to make one and have enough polyester fiberglass and resin to get this done.

Right now I turned the input on the front speakers to 0

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Old 09-09-2013, 09:12 AM
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Originally Posted by Traxx822 View Post
Wow thanks for the replys guys. As you can see the speakers are a mere inches apart. When I have the 7.7" turned off and the IB running medium volume to loud volume the 7.7" moves in and out. Earmark said to check that way in the other thread.

jimn, the crossover is set on 12 I believe. There is only three options. 0,12 & 24.

I bet I could make something out of fiberglass. Trying to figure out how to secure it without driving screws through the other side.

Sent from my HTC One using Tapatalk 2
The three settings would seem to be the crossover slope, which tells you how much it attenuates the low frequencies. 0 would be Off, 12 would be 12 dB/octave and 24 would be 24 dB/octave (an octave is the doubling or halving of the frequency). Look for a control near this one with larger numbers. If you can post a photo of the part of the amp with the controls, that would be good, too.
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