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View Full Version : IB sub and speaker in same enclosure help


Traxx822
09-08-2013, 12:16 PM
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.

JimN
09-08-2013, 12:36 PM
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.

MLA
09-08-2013, 01:36 PM
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.

JimN
09-08-2013, 01:46 PM
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.

MLA
09-08-2013, 02:10 PM
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

JimN
09-08-2013, 02:42 PM
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?

EarmarkMarine
09-08-2013, 03:14 PM
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

Traxx822
09-09-2013, 09:14 AM
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

Traxx822
09-09-2013, 09:33 AM
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

Sent from my HTC One using Tapatalk 2

JimN
09-09-2013, 10:12 AM
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.

Traxx822
09-09-2013, 10:18 AM
Jim are you talking about the dial that spins? And which one? The one for the sub or 7.7?

I know I have the 7.7's at 80 and the sub at 60

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JimN
09-09-2013, 11:19 AM
Jim are you talking about the dial that spins? And which one? The one for the sub or 7.7?

I know I have the 7.7's at 80 and the sub at 60

Sent from my HTC One using Tapatalk 2

Yes- that control. If you make an enclosure for the mid-bass, you'll be able to raise the sub't crossover frequency a bit to cover for the higher HP crossover frequency. Also, since the smaller drivers aren't required to handle the lower frequencies, they won't have a problem when the volume control is turned up. It will definitely help the mid-bass sound quality because the driver won't be affected by the sub. I would probably raise the sub crossover to about 80 Hz and the mid-bass to 120 Hz- you may not even notice the gap because this is the range where your engine makes most of its sounds and trying to overcome the noise floor in this region requires more power than most systems can provide while maintaining the full dynamic range (max output minus noise level).

EarmarkMarine
09-09-2013, 12:14 PM
Well, with a 60 hz lowpass crossover, you can be pretty sure that this contributed to the early subwoofer failure. It's an open field boat....not an enclosed car cabin. The meat of the bass is from 50 to 80 Hz. The roll-off begins 1/3rd octave below the crossover frequency. So at 60 Hz LP you are beginning to roll off the sub BEFORE/BELOW you get to the meat of the bass. To get ample output you are making the sub work inordinately hard with excessive excursion. Keep in mind that to reproduce one octave lower at the same amplitude, it take four times the power and four times the excursion. You are pushing the train up a hill. Again, it's a boat, not a car, so you do not want to gap the high and low pass crossovers unless you are running the subs really hot and that is a mistake with 10s. Gapping the crossovers simply reduces output in an area that is crucial to the perceived output. Use a symmetrical frequency. Raise the frequency up which generates more output and forces you to gain down the sub which compliments the reliability. The highpass on the 7.7s determine the sub lowpass....not the other way around.

David

Traxx822
09-09-2013, 12:21 PM
Yes- that control. If you make an enclosure for the mid-bass, you'll be able to raise the sub't crossover frequency a bit to cover for the higher HP crossover frequency. Also, since the smaller drivers aren't required to handle the lower frequencies, they won't have a problem when the volume control is turned up. It will definitely help the mid-bass sound quality because the driver won't be affected by the sub. I would probably raise the sub crossover to about 80 Hz and the mid-bass to 120 Hz- you may not even notice the gap because this is the range where your engine makes most of its sounds and trying to overcome the noise floor in this region requires more power than most systems can provide while maintaining the full dynamic range (max output minus noise level).

Very interesting. Thanks for helping me put this together. Its been a battle since install.

Couple questions about the slope setting and the crossover setting:

I have the slope on 12 instead of 24 or 12 because it seems to control the cone better. One side or the other seems either too tight and not enough base and the other is violent and distorted unless input is turned way down. The way the cone moves nice and smooth at 12 makes me happy so I left it there. Why?

Also I can switch between 4 channel and 6 channel but on 6 channel the sub picks up a lot of higher pitch noise that shouldn't be coming from a sub. Unless I turn the crossover way down and I can't hear them anymore. This also sounds decent when turned up like the above set up but since it just doesn't seem right to me to be running the amp like that I didn't leve it this way. Good decision?

Also, for the enclosure, since it's pretty tight, one side might have to be considerable bigger than the other due to the vaulted top side of the enclosure. Is the shape going to affect the sound if one side is significantly larger?

I have 4 M6.5IB on the tower. They are run by a M4/400 I have the input turned up about 80% and the crossover at 100 & each speaker is @2 ohm - 4 channel. They are loud, and I can hear them at 70 feet easy and don't seem distorted. At surf speeds I don't turn it up all the way as it is pretty loud. And my WS420 has the mic and it echo's when I talk through it. So I am pretty happy with it. But is there anything you can think of that might be able to make this better. Here is what I have noticed, I can hear at 70' all vocals, highs and some mid bass even. Hard rock sounds awesome, new age music with lots of bass sounds decent but not great.

I have been dabbling with the idea of upgrading my tower speakers. I really want the white 7.7" sport grills with the tweeter pods in either JL or MC pods. If I was to upgrade, could I use the same amp? the M4/400. And what speakers or suggestions can you make to get nice mid bass and deeper bass out of it.

Traxx822
09-09-2013, 12:29 PM
Well, with a 60 hz lowpass crossover, you can be pretty sure that this contributed to the early subwoofer failure. It's an open field boat....not an enclosed car cabin. The meat of the bass is from 50 to 80 Hz. The roll-off begins 1/3rd octave below the crossover frequency. So at 60 Hz LP you are beginning to roll off the sub BEFORE/BELOW you get to the meat of the bass. To get ample output you are making the sub work inordinately hard with excessive excursion. Keep in mind that to reproduce one octave lower at the same amplitude, it take four times the power and four times the excursion. You are pushing the train up a hill. Again, it's a boat, not a car, so you do not want to gap the high and low pass crossovers unless you are running the subs really hot and that is a mistake with 10s. Gapping the crossovers simply reduces output in an area that is crucial to the perceived output. Use a symmetrical frequency. Raise the frequency up which generates more output and forces you to gain down the sub which compliments the reliability. The highpass on the 7.7s determine the sub lowpass....not the other way around.

David

OMG I had to read this 4 times.

So leave it at 12 and turn it up to 75-80?

The highlighted sentence made a few light bulbs come on. Thanks

EarmarkMarine
09-09-2013, 03:07 PM
Odin, who administrates the Earmark on-line store, walks his customers through a step-by-step tuning prescription based on a seven-page pro tuning draft written by Earmark specifically for open-air boats. And then there is another advanced version if you have the tolerance for that technical level. But he can keep it as simple as you want. He will make the identical system components sound much better and improve the system reliability and efficiency in the process.
Odin has been with Earmark since 1992 and has worked in installation, sales, purchasing and management. A musician since 1984, Odin combines his love for music with a technical understanding of audio extending well beyond mobile and marine electronics. Odin has performed with local band Southbound since 1999, worked as the in-house sound engineer for hundreds of local and national touring artists at local music venue Hank’s Texas Grill since 2004 and collects and restores vintage amplifiers. I would consider Odin, with his considerable prosound, automotive, and marine audio background, to be one of the leading experts on system tuning and gain structure.

While I still help out on the forums, I am retired from Earmark.

David