IB project with LLT transformation ability?

1921 Views 7 Replies 4 Participants Last post by kjgarrison, Jun 3, 2008

kjgarrison

Discussion Starter · May 31, 2008

Hi all. I've been working on an IB subwoofer project design, and I came across the LLT threads. This is a box being built inside of an entertainment center.

I always was worried a bit about sending the backwave of sound throuought the adjacent space (basement in my case). (WAF) So now I'm thinking about how I could design in the capability to easily add a port, or ports, and enclose the box from the backflow room, thus transforming to an LLT. Another concern is that I am limited to having only 2 15" drivers. Maybe not quite enough for an IB.

Room is big: 8000 cu ft (open floorplan)
Viewing/listening position is 9'
90/10 HT/music
not interested in insane loudness
Budget is in the $1K to $2K range.

I have a couple of preliminary questions.

First, can an LLT's port, or ports, go into another room of the house, or does it have to vent into the main listening room? The 'other room' would be the basement and the very same room the IB will backwave into.

Second, can Google sketchup diagrams be used in this forum?

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Blaser

· #2 · May 31, 2008

kjgarrison said:
First, can an LLT's port, or ports, go into another room of the house, or does it have to vent into the main listening room? The 'other room' would be the basement and the very same room the IB will backwave into.

It has to vent into the main listening room otherwise you will lose the benefit of a ported design. Consider the port as an extra driver...(where should it fire?)

Second, can Google sketchup diagrams be used in this forum?

Yes, why not. Just take a printscreen, edit in a drawing program like then post.

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kjgarrison

Discussion Starter · #3 · Jun 1, 2008

Blaser said:
It has to vent into the main listening room otherwise you will lose the benefit of a ported design. Consider the port as an extra driver...(where should it fire?)

Yes, why not. Just take a printscreen, edit in a drawing program like then post.

Thank you.

I was afraid it would have to vent into the main room. I have a problem with depth and therefore the length a port can be. I assume, since I have not seen otherwise, that ports must be straight (as in no right angles.) Correct?

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Mike P.

· #4 · Jun 1, 2008

45 and 90 degree elbows can be used with no problems.

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Blaser

· #5 · Jun 1, 2008

Cooool Mike

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kjgarrison

Discussion Starter · #6 · Jun 2, 2008

Mike P. said:
45 and 90 degree elbows can be used with no problems.

Perfect. So what I'm going to do is go ahead with the IB but figure out what ports would be required if it doesn't work out as IB and install bracing/supports to be able to cut the holes and put the port or ports in.

Backflow might be a WAF problem. I'm pretty sure it will be, otherwise why am I not telling her about it! (Easier to ask for forgiveness than permission. Besides she loves bass, and hopefully she'll be happy with the sound.)

My other concern is that modelling my IB with Unibox, I have to keep watts way down to around 120 watts to keep from pushing my proposed drivers (2 x Tempest-X 15") beyond Xmax. And along with this the SPL is only at around 110dB. Now maybe 110dB is plenty, I don't know, but I see why in the IB "cult" forum everybody seems to be starting off with 18" drivers, and those that start with "only" two frequently seem to upgrade to 4.

Thanks everybody.

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collo

· #7 · Jun 2, 2008

Because IB's don't have the "air spring" effect of a normal sized sealed box, or the loading of a port, excursion is always the limiting factor.

If you add up the thermal rating of a bank of IB drivers, it's usually quite a lot higher than the actual amplifier driving them.

110dB isn't a lot really.

Here are some designs for 2, 4 and 6 tempest-X IB's

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kjgarrison

Discussion Starter · #8 · Jun 3, 2008

collo said:
Because IB's don't have the "air spring" effect of a normal sized sealed box, or the loading of a port, excursion is always the limiting factor.

If you add up the thermal rating of a bank of IB drivers, it's usually quite a lot higher than the actual amplifier driving them.

110dB isn't a lot really.

Here are some designs for 2, 4 and 6 tempest-X IB's

Thanks. Upon further review, I might have a problem using Tempest-X. For the initial IB build, two is the max I have room for, and two would be much preferable to just one. However, if the IB doesn't work out and I close off the backflow end and make it into a box, the volume will only be ~500 liters. Maybe enough to qualify as LLT for one Tempest X, but not Large enough to make LLT for two. Vas is 324 liters.

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