A whole slew of basic questions

**Ryan Anderson** · **10-07-09, 03:25 AM**

One thread on here I really loved was a conversion from IB to LLT. I simply can't see not using the rear radiation from a cone whenever possible. To get down to 8Hz, you have to move a TON of air. Tuning around there should about double output, 1/2 the drivers/power required? I don't know the exact numbers...but I see where the IB seems better... no space taken up, and is as big as your attic.

Why not build an LLT in the attic? If you're willing to do some extra work, would it be possible to use multiple subs larger than the width between rafters? I know... it's crazy... but I've seen a LOT of time, money, and labor put into some really nice systems here... why not build a HUGE LLT in the attic?

**robh** · **10-07-09, 06:59 PM**

There's not enough room to build an LLT in my attic, nor is there enough room to build an IB manifold. I only have about 2-3 feet of space above the ceiling in the area this would need to go in. And besides, anything really large is not going to work in that room. I did some rough calculations last night, and I'd need no less than about 36 cu. ft. to get the performance that I'm after. I don't want 6 ft tall subs unless there's absolutely no other way to avoid that. And even then, I'd be more likely to just abandon the whole thing since there's no where I could put something like that in my living room and not have it look like complete .

**Mike P.** · **10-07-09, 07:21 PM**

You can state what the biggest size box would be that you're comfortable with and we'll see what we can come up with.

**robh** · **10-08-09, 12:32 AM**

OK, in a somewhat surprising turn of events, the WAF said that I could go 6 ft. high. The space available next to the speaker is 2x3 ft., which would completely fill the area next to the speaker. I might be able to get to 2.5x3.5, but that would not be easy.

The downside is that she says if I do this, there's no more. While she would possibly relent eventually, especially if something just shows up (forgiveness/permission), this would likely take quite some time. So... that's one reason the IB is rather attactive over the LLT option. It would really hide the subs.

**Ryan Anderson** · **10-10-09, 06:27 AM**

I'm up listening to Toccata in D minor off my modified surround sound, can't sleep as usual...and so I started surfing. I thought to share these in hopes to reignite your quest

http://www.allypallyorgan.org.uk/organpresent.php

The boot of bottom D and C of the 32ft reed, showing the Willis starter-motor

The longest pipe currently in the organ, bottom C of the 32ft reed. This pipe survived from the 1929 instrument and can be contrasted with D, behind it, which was remade.

what I'd give for this thing to be completely refurbished and have a real good listening session

**seattle_ice** · **10-10-09, 10:44 AM**

Some of those historical Pipe organs are unbelievable.

**robh** · **10-13-09, 01:45 PM**

Well, I've come back to something someone said earlier about building an LLT in the attic. I didn't think that was feasible at first, but I've come back to that and it looks like I might be able to swing something like that. I was actually considering combining bit of IB design with bit of LLT design to do a hybrid. I could enclose maybe 50-100 cubic ft in the attic, with the woofers (4-8?) facing down through the ceiling into the listening area, and a port or two as long as they needed to be to make the ports effective in my desired tuning target. I would probably use the new Exodus 21s with a fs of 16.3 and Qts of .42. Does is seem as though I may finally be on the right track to produce something that might have a chance to do what I want it to, assuming the room doesn't kill it? And speaking of which, for figuring the modes in the room, so I need to do something more than put a sub in the listening spot and start measuring across the ceiling until I find 1-2 favorable spots?

And thanks again to all who have replied. I knew this would be a challenge, but I guess I underestimated it. The difficulty, however, has made me more determined than ever to pull this off with results as close as possible to my stated goals.

And I already have buy-in from the wife on the possibility that I might be cutting big holes in the ceiling and framing them in, etc.

**Ryan Anderson** · **10-14-09, 11:19 PM**

Quote:

robh wrote:

Well, I've come back to something someone said earlier about building an LLT in the attic. I didn't think that was feasible at first, but I've come back to that and it looks like I might be able to swing something like that. I was actually considering combining bit of IB design with bit of LLT design to do a hybrid. I could enclose maybe 50-100 cubic ft in the attic, with the woofers (4-8?) facing down through the ceiling into the listening area, and a port or two as long as they needed to be to make the ports effective in my desired tuning target. I would probably use the new Exodus 21s with a fs of 16.3 and Qts of .42. Does is seem as though I may finally be on the right track to produce something that might have a chance to do what I want it to, assuming the room doesn't kill it? And speaking of which, for figuring the modes in the room, so I need to do something more than put a sub in the listening spot and start measuring across the ceiling until I find 1-2 favorable spots?

And thanks again to all who have replied. I knew this would be a challenge, but I guess I underestimated it. The difficulty, however, has made me more determined than ever to pull this off with results as close as possible to my stated goals.

And I already have buy-in from the wife on the possibility that I might be cutting big holes in the ceiling and framing them in, etc.

This would definately be the best: biggest and lowest tuned combined with the most actual displacement. I think this would be simply amazing!

**robh** · **10-15-09, 12:13 AM**

I've got a set up modeled in winisd that involves 256 cu ft and 2 12" ports. I think the problem I'm running into after reading the docs on the diycable site for the Exodus 21 is that winisd doesn't take room gain into account, and I can't figure out how to model room gain. So while I'm showing very flat response, that's strictly from the drivers, yes? Is there a way to model room gain? Or another package that can model room gain?

**Ryan Anderson** · **10-15-09, 12:43 AM**

Quote:

robh wrote:

I've got a set up modeled in winisd that involves 256 cu ft and 2 12" ports.

:-O

:-D

**Mike P.** · **10-15-09, 04:49 AM**

Quote:

I've got a set up modeled in winisd that involves 256 cu ft and 2 12" ports.

How many subs?

**robh** · **10-15-09, 09:49 AM**

Quote:

Mike P. wrote:

How many subs?

4. But I need to figure out how to approximate room gain. I'm also strongly considering splitting it into to boxes to make thing more manageable.

**Mike P.** · **10-15-09, 10:20 AM**

What are the room dimensions, is the room closed or open to other areas?

**robh** · **10-15-09, 10:50 AM**

Approx. 22x24x9, and it is open to other areas. The total area I need to pressurize is about 1400 sq. ft. with an average ceiling height of about 8.5 ft. And I'm trying to figure out how to model the "6db per octave" number that I keep hearing as the approximate room gain. I'll be mapping out modes and nulls the old fashioned way. Going to walk around carrying an SPL meter with a sub playing pink noise at the listening position.

**Ryan Anderson** · **10-23-09, 12:40 AM**

Quote:

Ryan Anderson wrote:

I'm up listening to Toccata in D minor off my modified surround sound, can't sleep as usual...and so I started surfing. I thought to share these in hopes to reignite your quest

http://www.allypallyorgan.org.uk/organpresent.php

The boot of bottom D and C of the 32ft reed, showing the Willis starter-motor

The longest pipe currently in the organ, bottom C of the 32ft reed. This pipe survived from the 1929 instrument and can be contrasted with D, behind it, which was remade.

what I'd give for this thing to be completely refurbished and have a real good listening session

I made a mistake, scoobydoo6v92 informed me that Bottom C aka Low C is a 32' for 16.4Hz.

**fredk** · **10-24-09, 10:27 AM**

Quote:

Going to walk around carrying an SPL meter with a sub playing pink noise at the listening position.

Thats a good idea. I started out thinking my room was 11 x 20 x 8, but after playing with sub positioning and measureing sweeps at various locactions I figured out that the room was behaving like a 20x20x8 room. The section that comprises my kitchen (walled off) and my diningroom area were effectively coupled to the livingroom area.

**robh** · **11-12-09, 06:19 PM**

After discussing this with Kevin @ Exodus, I've settled on an IB design, and depending on what the room can deliver, I may add a Linkwitz transform, of if I'm lucky, just a bit of EQ to fine tune the response. This will be a 4 driver IB design using the new Maelstrom 21 and ceiling mounted.

**robh** · **11-12-09, 06:26 PM**

Quote:

Ryan Anderson wrote:

One thread on here I really loved was a conversion from IB to LLT. I simply can't see not using the rear radiation from a cone whenever possible. To get down to 8Hz, you have to move a TON of air. Tuning around there should about double output, 1/2 the drivers/power required? I don't know the exact numbers...but I see where the IB seems better... no space taken up, and is as big as your attic.

Why not build an LLT in the attic? If you're willing to do some extra work, would it be possible to use multiple subs larger than the width between rafters? I know... it's crazy... but I've seen a LOT of time, money, and labor put into some really nice systems here... why not build a HUGE LLT in the attic?

Coming back to this, the area has a vaulted roof, and after looking at this, there's just no practical way to build much of anything over the listening area. I'd have to have a base of at least 8X8, and I just don't see a way to achieve that. I would be limited to a height of about 3-4 ft, thus the crazy huge width/depth.

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