Is my HT a candidate for IB?

**cynical2** · **03-10-08, 04:43 PM**

The back of my Home Theater (located in my basement) has an good sized unfinished room on the other side of the wall. So, my question is whether or not putting the sub at the back of the room (rather than the front) is OK.

Room is 18'5" x 15' x 8'. Back wall is 15' W x 7' H (~12" raised tier for 2nd row seating causes height to be 7' rather than 8').

The 1st 3 questions that I have:

My pj is on a shelf that's mounted to that wall. It can't be vibrated throughout the movie. One thought that I had was to build a box in the unfinished room, mount the driver to it, and then have something like a foam gasket between the box and drywall to "decouple" the wall (and consequently the pj shelf) from vibration. Would this work? Any other ideas that would work better? Any proven designs? Hanging the pj from the ceiling is not an option. The ceiling joists are very long at this location in the house, and make up the floor to our main living area (family room). I started with it hung from the ceiling, and even tried to isolate the mounts, but it just didn't work out.
I'm also concerned about the thought of having the sub in the back of the room. I know the reco for a single sub is typically to locate it at the front of the room...but then I also know that subs are supposed to be "non-directional".
If I can get past issues (1) and (2), at what height should I mount the IB? Behind the chairs? Above the chairs? In the corner where there is no chairs (the left edge of the wall in the pic)?

If this is feasible, the plan would be to get an EP2500 to drive it.

Thanks for your help!
Jim

**Sonnie** · **03-11-08, 02:24 AM**

I do not think there will be a way to keep that wall from vibrating that much... but it might be that you could do an SLLT similar to what Rodny did. If you can anchor the box to the floor on the other side of that wall, it might keep the wall from vibrating so much. The idea is to keep the box from vibrating and you should be fine.

You may also have to experiment with your crossover setting and phase to get it to work right in the rear, but many people have subs in the rear of their room.

To determine the best location, the proper way will be to place a sub in your main listening position and use a mic and REW to measure the response at various locations back there. Just go from one side to the other with the mic and measure about one foot from the floor next to the wall, then move up a foot and remeasure... and so on. I doubt there will be much difference from the floor to the ceiling, but you can check it anyway. I would suggest trying to mount them as low as possible.

**cynical2** · **03-11-08, 05:44 PM**

Thanks, Sonnie. Can I just do that with my current sub (Paradigm PS-1200)?

Also, do we have a thread somewhere for "recommended gear", like mics, etc?

**Sonnie** · **03-12-08, 03:14 AM**

Yes... absolutely. I did mine with one of my SVS PB12-Plus/2 propped up in my main recliner.

I don't think we have a thread per-se, although there are probably lots of threads on mics in the SPL Meters | Mic's | Calibration forum. Your best bet is to probably just pic up a Galaxy CM-140 SPL meter if you plan to only use it for REW and setting up your sub. It would be your cheapest route at about $100 through probably Musician's Friend.

I am checking with brucek... I thought we had a Sticky on what all is needed. If not, maybe we can get one.

**cynical2** · **03-12-08, 09:38 PM**

Thanks for the advice and mic info!

**Sonnie** · **03-12-08, 10:37 PM**

brucek is working on a sticky for everything needed to connect REW to your computer depending on what mic or meter you use.

Check out the REW Help Files as well... they are very helpful on connections.

**cynical2** · **03-13-08, 04:42 PM**

Quote:

Sonnie wrote:

brucek is working on a sticky for everything needed to connect REW to your computer depending on what mic or meter you use.

Check out the REW Help Files as well... they are very helpful on connections.

Thanks, will do!

**thxgoon** · **03-14-08, 11:48 AM**

Ya, what Sonnie said for placement

I don't think the walls will be the problem for vibrating your pj as much as the amount of bass you'll be pumping into the room. My subs are not connected to anything other than the concrete floor of my basement and the projector still gets a good shake during loud scenes.

Also, in the past I had a sub located at the rear of the room and it sounded great! Just depends on the room and the setup.

What drivers are you thinking of using?

**cynical2** · **03-15-08, 01:18 AM**

Quote:

thxgoon wrote:

Ya, what Sonnie said for placement

I don't think the walls will be the problem for vibrating your pj as much as the amount of bass you'll be pumping into the room. My subs are not connected to anything other than the concrete floor of my basement and the projector still gets a good shake during loud scenes.

Also, in the past I had a sub located at the rear of the room and it sounded great! Just depends on the room and the setup.

What drivers are you thinking of using?

Interesting...

I'm still in the "figuring out what I want to do" project phase, so it will be a while before I make any decision on drivers.

I thought that these AE IB15's looked interesting. 4 of 'em for $400 isn't bad. Chrisbee used them in his build.

**Blaser** · **03-15-08, 04:50 PM**

Hi Jim,

I know you are a "picture guy" more than a "sound guy"

, and I am quite the reverse (or propably was).

First of all your room looks fantastic (Chapeau!!). Can you tell me why you don't put your front wall as an option? Do you have a faux wall?

By the way bass is non-directional but either placement of the sub or yourself in the room will greatly affect how loud you hear it. Also, sometimes due to room modes you may have bass SPL varying a lot within few inches (no joke), so that you may hear it louder in an ear than the other and this gives an effect of being directional but that is not so frequent, so don't bother (I was just replying to your question).

You can use an amazing program if your room is a "shoe box" to similate how good your boxed sub(s) will do at your listening position. http://www.pvconsultants.com/audio/r...s/room060d.exe
It will help you a lot. If you can't find a sweet spot for a box, only then you may propably consider an IB (but I am large box biased).

Regarding vibration of the projector, as far as it is mounted to a hard wall, I believe you will never have any problem. FYI, I have dual 18" in my 1800 Cu Ft room and no problem at 125 db+ ...nada!

Have Fun!

**Blaser** · **03-20-08, 05:38 PM**

Jim,

Any news?

**cynical2** · **03-20-08, 06:01 PM**

Hey Ahmed,

Thanks for the info you shared. I've been buried with work for a week...it's nearly killing me.

To answer your question...no faux wall at the front. An exercise room (that I can't lose any space from) is on the opposite side of that wall. The rear wall is the only option...it has an unfinished storage area that I can cut into on the other side of it. I wasn't really worried about the pj vibrating in general...only if I used the pj wall and the IB wall were the same. I would think vibration could be an issue in that case.

At this point, I'll probably end up either building LLT (something that will lay on it's side such that I can hide it in a stage)...but it'll be a couple months before I can start in earnest.

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