Ideas? - Screenwall Sub (1 Viewer)

[Gregory]

I'm in the process of a basement remodel. My screenwall is constructed of 2x10's. To the left and right of the screen I have two stud cavities that are 9 1/4" deep, 16 1/8" wide and 88 1/4" tall. It's possible I could add MDF to the front and back and make two sub enclosures.
My question to all the diy sub gurus here is what kind bass could I get out of these areas(or is it a bad idea?) with a buget of $600. I haven't ever built a sub so I don't know a whole lot about their design, but I have many tools and the skills to use them.
Thanks in advance. Maybe I'll get some pictures of the project up soon since I enjoy seeing others.
Greg

 

[Greg Monfort]

How much amp power is available, or is it part of the budget? To get good results from whatever you may build, a sub EQ will be needed if you don't already have one. What's your current sub/location, to get a frame of reference?

GM

 

[Gregory]

Currently I don't have a sub location, I'm still in the construction process. I haven't run the wiring yet. I was planning for a back coner location. The room is sealed and smallish at 10 x 16.5 x 7.5. I have 2 free channels of a Marantz MM9000(150W@8Ohms), but could also add another amp. We'll say $600 does not include the amp. The volume of the boxes would be 7ft^2 or around 200L.

Greg

 

[Greg Monfort]

Well, you're not going to meet reference, but your room is small enough that I don't believe you'd want it. If you sit mid way, then there'll probably be a ~9dB drop over distance, but room gain should negate much of it in the bottom octave.
Four Tempests + shipping and enough fiberglass to stuff the cavities ought to eat up $600. In sealed cabs, with 150W/pr, you'll never make them sweat, but should still get 110+dB/listening position out of them in the midbass, and I'm betting close to this at 20Hz with room gain. Later, if it's not loud enough you can get a hummer amp and use EQ to further boost them if duplicating the Maxell tape ad is the goal.
GM

 

[Ned]

Why would you "not want it" in a small room? Room size has nothing to do with reference being good or bad as long as the space is acoustically treated. Of course that's the big gotcha. Virtually no one is willing to spend the money and effort to add acoustic absorbers/diffusers

 

[Greg Monfort]

Yes, and no. The smaller, and more sturdily constructed the room, the harder it is to control modes, and why studio control rooms are shaped the way they are, with diffusor walls and external bass traps.
Of course if a car boomer is the frame of reference, then my response is moot.
GM

 

[Chris Carswell]

Greg,
I like the 4 tempest idea, my kinda guy
I was going to say IB but not enough room to do so I guess.

 

[Andrew Pratt]

Can you get to the other side of the wall you wanted to mount the subs in? If so why not consider an IB sub?

 

[Chris Carswell]

ah ha, someone else was thinking about the IB idea as well

 

[Gregory]

The concrete foundation is directly behind the wall. However, there is a crawl space in the back of the room which the rest of the house sits on. It would probably be perfect for an IB. That is where I'd really like to locate the sub anyway. Hmmm...

 

[Andrew Pratt]

I owned a Shiva based sub and a large tempest tube sub before I built my dual tempest IB and I've been very impressed with the sound quality I'm getting from the IB sub. I just need the BFD to tame a null at 50 Hz and I'll be set.

 

[Mark Seaton]

Greg,

First, it will be hard to come up with a much better option than the Tempest to maximize your $600 and existing amplification. Four Tempests are probably the way to go. There are a few interesting options you have, and considerations to make.

My first question would be to take a closer look at what's going on at the screen wall. While each cavity is 7 cu.ft., if there are adjacent cavities you can always create openings between them and get a space 2x the size. I would also take a look at the spaces directly behind the screen where you could mount the subs below the screen using the space behind. Power wise, the Marantz will handle 4 Ohms fine, so you have a few wiring options depending on what sort of space is found.

If you wire up the drivers as 16 Ohms each and then parallel them 2/ch. you have one response set. The other option is to only connect one voice coil of each driver, with 2/ch. on the Marantz. This will give you similar output at the upper range, but change the low end response. If you have more space to take advantage of, then this will probably be preferred. With such a small, sealed room though, you will see a good deal of low frequency gain, much like in a car subwoofer. In your room, I would expect this to start taking effect in the mid 20s. My suggestion for wiring both coils of a Tempest would be to use one per 200L cavity. I haven't looked at the possibilities yet with only one coil connected. For the IB in the crawl space, this would be the preferred connection.

Now, the IB is a great idea, but in such a small, solid room, you need to look at placement of the subs and the seats, to see what you can address with modal problems in the room. This is where I see the front wall offering more flexibility. Understand also that with such large enclosures, you would be getting rather similar performance to the IB. The main concern with the front wall is the front surface vibrating. My suggestion would be to find 13 ply Baltic Birch for the cover/baffle.

Give us some more details of the layout and you should be able to create some really awesome performance.

As for "reference level" I certainly believe it is worthwhile, yet I question if your main speakers would have a chance of meeting such levels. With 4 drivers in the real room, I'm guessing peaks to ~115dB at the seats may be within reach. This is about the figure most designers would use for a "shy of extreme" system, with 125dB peaks being about ideal, but I doubt it is multiples the budget mentioned. Fortunately just supplying 3-4 times the power would be a great upgrade when you feel the next itch.

Regards,

 

[ThomasW]

Gregory

Since you're located in Colo Springs, you're about 35-45 min away from my place (Denver off I-25 & Hampden) on a good traffic day. I'll be happy to demo both the IB's if you're interested. Email to set up a day/time

The crawl space is a great place to put the drivers.

BTW, 4 Tempests is certainly overkill for a small room

Regards
Thomas

 

[Greg Monfort]

>BTW, 4 Tempests is certainly overkill for a small room
====
A rather strange comment coming from a person with a twelve Shiva sub. As you well know, more efficiency = lower distortion.

GM