BSC or not? That is the question.

[moniker]

Sorry this is so long, but I need some serious advice. ;x(

This forum has really great designs for speakers with crossovers for in-room or in-wall use. The question is, which to use in my application? I have a problem in that I don't know which sort of crossover to use and cannot properly design one on my own. :M

My situation is shown below. The first pictue is the front wall of the HT I am helping a friend complete. It is 12' high and 19' wide, has large windows and is made of concrete block. 8O

Unfortunately, the-one-who-must-be-obeyed has decreed that all speakers must be built in. So the only alternative is to build a sort of window box for the woofers and CC and some sort of cabinets for the L and R speakers. This is shown in picture two.

The situation is worse than it looks because the room is only 15'6" deep and that limits screen width so that the L and R speakers will be much wider than would otherwise be ideal. :E

At this point it seems the "window box" and vertical cabinets will be at least 12" deep and perhaps 18" deep. So the CC and L and R speakers will be faced with a wider than usual cabinet face and be stepped away from the wall by 12" to 18".

The question is which crossover should I use. One with the baffle step correction or one without? Probably something inbetween is right but I cannot design it so I guess the best bet is what I am looking for. :huh:

I am leaning toward the Natilie P and the WTMW CC that is soon coming and will use either four 12's or four 15's for the subs. :T

There are two more issues I need help with. They are the appropriate way to aim the L, R and CC toward the listener. With the CC so low, I suppose it needs some aiming. With the L and R so far apart, I suppose they need some aiming. Any suggestions on smart ways to do that will be appreciated. ;x(

If anyone sees problems with the concept or improvements or any warnings, please let me know. :lol:

Thanks for wading through this long post and thanks for such a great forum with all the helpful members here. :T

[TacoD]

1) use the one with BSC and make the port at the front of the cabinet.
2) yes you can point the loudspeakers to the listening positions. Otherwise you listen off-axis and the sound is still good but the treble range is attenuated.

[ThomasW]

Well Taco and I are going to disagree on this...

The BSC designs are for a baffle 9" wide (not 36" wide). And for the speakers to be placed approx 36" or more away from ANY boundry, ....a boundry being (rear-wall side-wall, floor, or ceiling).

It doesn't appear to me that the installation meets the criteria for having BSC.

You don't need to port the L>C>R because they won't be running low enough to utilitze port output.

Yes, if possible aim the mains at the listener. I'd build the boxes as free-floating entities within the 3' frame, that way they can be aimed at the listening position.

You gain nothing by having the L>C>R 18" deep

[cjd]

I agree with Thomas.

Also, Is this a front-projector setup? Can't tell. But consider an acoustically transparent screen and go truly in-wall. SMX may still be offering by-the-foot if you want to make your own screen frame. Not sure why you have screen width limitations unless I'm again missing part of the picture. :P

Also, if it's just a distance to screen limitation on width, consider a constant-height setup with anamorphic lens for the 2.35:1 films.

C

[moniker]

Just a bit of clarification. This project is in new construction going up for a longtime friend of mine.

My friend is consulting with a local HT "guru" and the guru is suggesting "invisible speakers" from http://www.stealthacoustics.com/. These are limited distribution items for installers only (imagine the mark up!). The guru claims they are HiFi and will do subwoofer duty too! :rofl:

Interestingly, the invisible speakers will not work as front or CC because the wall is cement block and glass and there is no room for installation. He is suggesting all speakers be placed on the side walls! :bash:

I reiterate. Imagine the mark up! 8O
Please help me save my friend from this guy. :frypan:

The Natalie Ps with real subs will be ever so much better. :T

Actually, my friend has asked me to do the HT around the guru who is putting in "elevator music" throughout the rest of the house so I would like to do at least a journeyman's job on the HT room.

I plan to use closed boxes if it works out that the system can be crossed over and integrated well without using vents. This is a build it once situation. There will be no cut, build, measure and then try it again, so I am looking for a reasonable solution from jump street. I have measurement capability (ARTA) and intend to use limited parametric Eq in this installation.

Free standing speakers are routinely pointed toward the listener. But this situation seems substantially different due to the nearness of wall boundries. Here there are many potential discontinuities, edges and nearby reflecting surfaces to be considered and I am not quite sure what to do.

I see three basic possibilities for the L and R speakers (perhaps there are more?).

First - build closed L and R rectangular columns and build in the speakers. That would result in the speakers firing parallel to the side walls and being about 18 inches from the side walls and about 18 inches from the front wall. This does not seem like a good solution to me, especially in a 19' wide room.

Second - (I am leaning in this direction) build open or partially open L and R rectangular columns with open shelves in them. The L and R speakers can be placed on an open shelf and aimed where we want them. This seems like a better idea (and has the best WAF) but it involves many more diffracting edges and cavity resonances too. This method should result in a lot of bass lift so the BSC should not be necessary. Right/Wrong?

Third - build triangular columns with the three sides made up of the side wall, the front wall and a baffle joining the two. The angle of the baffle could be such that it aims at the listening position. This will also create a lot of lift on the L and R speakers and it will have a very wide baffle. This has a low WAF. This is probably ideal for the no-BSC crossover. Right/Wrong?

It seems there are no real good solutions (unless someone can suggest one) and I do not know which plan is the most benign or which of the crossovers presented on this forum would be best in each instance.

I suspect others have had similar problems and have found solutions that they will share.

I hope this thread will generate some discussion and help me settle on a reasonable solution to the problems in my friend's HT build out.

Thanks :T

[moniker]

It seems clear that there were some responses while I was writing my big reply.

Thanks. :T

Here are some answers.

This is going to use a projector and the screen will come down from the ceiling.

The front wall is concrete block and glass. No way to put speakers behind the screen.

When not being used for HT, the screen will be rolled up and the windows will be available for light. When used for HT, heavy curtains will be closed across the windows and the screen will be lowered.

The problem with screen width is viewing distance. The room is only 15'6" deep and for reasonable bass response the prime seating position will be about 10' from the screen. Even when using the THX 36 degree reccomendation the screen will not be terribly large.

Thanks for the lens suggestion. I will check on it. :T

[TacoD]

Well Taco and I are going to disagree on this...

The BSC designs are for a baffle 9" wide (not 36" wide). And for the speakers to be placed approx 36" or more away from ANY boundry, ....a boundry being (rear-wall side-wall, floor, or ceiling).

It doesn't appear to me that the installation meets the criteria for having BSC.

You don't need to port the L>C>R because they won't be running low enough to utilitze port output.

Yes, if possible aim the mains at the listener. I'd build the boxes as free-floating entities within the 3' frame, that way they can be aimed at the listening position.

You gain nothing by having the L>C>R 18" deep

No problem! :T You know the Modula far better than me. For European standards 36" is a reasonably distance, most of our speakers are tuned for this boundary loading.

[ThomasW]

He is suggesting all speakers be placed on the side walls!

That in and of itself is reason to fire him.... :roll:

Can you post a floor-plan? That would be very helpful

[Nathan P]

Ugh, do not, I repeat, do not let him listen to this "guru" too much! A friend of ours had all in wall speakers put into his house for multiple rooms, and while the sound is "clear" the imaging etc is terrible due to the less than ideal locations provided by the in walls (Actually in ceiling, even worse I would think.) And I'm not quite understanding, the big W is willing to allow a projector and screen hanging from the ceiling but not box speakers? Anyway to talk her out of it? And how are you going to do inwalls at all in a concrete wall?

[moniker]

Hi Guys,

It is embarassing for me to say much about this HT room. It is in the largest and most expensive house currently being constructed in my county. And that is saying a bunch because it is on the gulf on the west coast of Fla where there are a lot of very nice houses.

When the first plans were drawn, my input resulted in a HT room that was 19' x 25' with a 5' x 19' room on the other side of the viewing wall for equipment and in wall L, R, C and subs. Things changed after a while, especially after the family hired an English architect to get the "details" right. Of course the Englishman has no use for HT and considers it a blight. That, coupled with increasing desires by she-who-must-be-obeyed, has resulted in some amazing changes. One of the wife's closets is over 400 sq ft! The pantry is over 100 sq ft and the formal dining room now can comfortably seat 20 for black tie dinners. Of course, this family never does formal in house dining!

Well, enough of that. If you look at the pictures in my first post you will get an idea of what the viewing wall looks like. Attached to this message is a floor plan I sketched out. Pardon the amateurism but I am not a cad guy. Anyway, the scale is pretty much right and you can see the mess of it. The platform will have a couple steps up all the way around. I did not sketch that. Contraty to the way it looks on my sketch, it will be almost impossible to wall mount decent surround speakers because of the way the walls are constructed and what is behind them. Don't ask!

Due to size constraints it seems to me that all that can be done here is 5.1. There is not really room for rear effectors unless they are put in the ceiling aiming down at the listeners.

I have almost gone mad with FRD's Room Mode Calculator (thanks FRD). It ain't a pretty picture. So I am doing what I can with what I have available.

As for the guru, he is what he is, a merchant maximizing his income. I have no interest in dealing with him and will let him do the job of setting up all the security and closed circuit cameras (the family has a couple disabled children), financial screens, elevator music, etc. I will be asked about speaker placement in some rooms, but I have little taste for it when the speakers are going to be vibrating pieces of sheet rock. In that case my friend is going to get what he and his wife ask for, but they surely will not get quality sound, especially for the money throughout the rest of the house.

In any event, take a look at the prior sketches and the current floor plan. Don't cry too much for me. Rather, if you have some good ideas, let me know.

I haven't accurately calculated the room's cubic volume but it is less than 3,500 cub ft. So I guess from what another poster here suggested, four RS315HF's in low Q alignments should get the job done.

And Nathan, the architect asures me that with all the crown molding, cournices, and crap he will put up that the screen will essentially dissapear when it is sucked up into the ceiling. :roll: Now how about that projector? :B

Any help and suggestions are appreciated.

Thanks again. :T

[ThomasW]

A ~19' wide room is a nightmare for smallish box speakers needing to be basically 'hidden' in the corners.

How far out into the room will 'she' allow the woofer box and some side columns? And how much floor space could the columns occupy?

BTW how big a lot is this house on? Perhaps 'he' can builded a proper dedicated HT as an 'out-building'...

[Brian Bunge]

This kind of thinking drives me nuts. You'd think that a guy could have one room to himself and decorate it any way that he sees fit. Also, when built properly even speakers can look like fine furniture.

Thank God my wife loves my work and that fact that I have a little bit of an eye for decorating.

[moniker]

"A ~19' wide room is a nightmare for smallish box speakers needing to be basically 'hidden' in the corners."

That is why I posted here for help. The situation is a real PITA.

"How far out into the room will 'she' allow the woofer box and some side columns? And how much floor space could the columns occupy?"

Well, to be fair, it is not really "she" at this point. The room design is fixed and there is no more than 3' from the side walls to the windows. Probably, from a design standpoint, the cabinet edges will end up about 18" to 24" from the side walls. I will have to see about that.

"BTW how big a lot is this house on? Perhaps 'he' can builded a proper dedicated HT as an 'out-building'... "

The lot is very large for a gulf front parcel. But the house is over 15,000 sq ft under air conditioning. And there is more spread around outside. Also it is an integrated design like a Tuscan mansion, including lime stone cladding for the whole structure. There is not one more sq inch available for out buildings.

"This kind of thinking drives me nuts. You'd think that a guy could have one room to himself and decorate it any way that he sees fit. Also, when built properly even speakers can look like fine furniture.

Thank God my wife loves my work and that fact that I have a little bit of an eye for decorating."

I agree. And I think speakers ARE furniture. They have a function just like a table or chair and look just as good to me even if not particularly well finished. Its a form follows function thing for me.

What drives me crazy is spending large sums on fireplaces, monster formal dining rooms, and monster formal living rooms all of which no one uses here in Florida. But the wives and architects have great power in home design. It is as though they are designing for people who do not live there.

Congratulations for having a fine eye and a fine wife. No doubt your eye helped in finding the ideal wife.

Later

[ThomasW]

The question was how far out into the length of the room can the sub box and side columns extend?

Given the width of the room I doubt that smallish MTM's like the designs we've been discussing will be adequate for the task at hand.

If the columns/pillars can be turned into larger WMTMW or MTMWW designs then you stand a chance of creating a decent soundstage.

[Johnloudb]

Lineup Maxx

I agree with Thomas. I've no experience, but I've heard it's important to have fullrange speakers for all channels in a home theater. I'm thinking Jed's "Lineup Maxx" (MTMWWWW) might fit that bill. It's not yet finished, but Jed's moving right along, if you've got time to wait.

It's small in stature, but it should have a big sound. The Maxx has the four 5" subwoofers.

http://www.htguide.com/forum/showpost.php4?p=353979&postcount=333

[Paul W]

If I'm reading the drawings correctly, the L&R speakers are going to be extremely close to the sidewalls??? Ninety degree sidewalls only inches away will produce horrific reflections...probably nullifying any existing crossover design and/or hope of good sound.

However, if that is all you have to work with, consider building the L&R speakers into the corners with the baffle panels directly facing the listening area (triangular enclosures). Wall treatments on either side of each speaker may be appropriate, including using the space within the walls...try to build in as much physical tuning flexibility as possible.

The crossover for your buddy would be something like the Tact. Tact should get you closer-to-optimal for any given speaker location without having to do a custom passive crossover. Plus, you could upgrade to any desired drivers for less than the cost of the shoe racks in the closet


Edit: I just noticed the 18-24" distance...still too close, but you might "get by" with wall treatments and conventional boxes.

[moniker]

Right now it looks like the window box may extend about 18" into the room. Same goes for the fronts of the L, R and CC. Perhaps a better way to say it is that the L and R will have to exist in a foot print that is 18" x 18" in each of the front L and R corners of the room.

Attached is a simplified floor plan to show what is going on. The 1' high platform for the couch is deleted for clarity. This drawing, while ugly, is to scale and I have included important distances. Looking at my prior attachments, as ugly as they are, along with this one should give a good idea of the problems in this installation.

I have accurately calculated the volume of the room. It will be almost exactly 3,000 cub ft. So four RSHF 12's should do the job?

I am planning to use the NatP for the L and R. Aside from the speaker placement acoustical irregularities, I hope the NatP's (in concert with the CC, surrounds, rear effectors and subs) will be able to do the job (total SPL at movie peak loads like explosions, gunshots and special effects, of about 105db). I plan to use the Nat's in an AS mode with a Qt of about .6 and crossed to the SW's (also AS with Qt of about .6) at about 80 Hz. Of course the Nat's, surrournds, CC, and rears will all be "small".

What do you think of the plan, given the room volume and the distance of the various speakers from the listener? Suggestions on speaker designs to use, Qt, crossovers, etc. are greatly appreciated.

Surrounds and rear effectors will be difficult to implement due to the nature of construction (there is little or no room for a decent box to extend through to the other side of the walls). I may be forced to use some sort of in-wall design for them. Suggestions please?

And please keep in mind that the front wall is an outside wall made of solid concrete and glass. There can be no recessed speakers, or recessed anything else for that matter, in that wall.

It would be much better if I could use the equivalent of a shortened , floor standing NatP sitting on the window box for L and R and move them away from the side walls right next to the edges of the drop down screen. But that would place the NatP's in the middle of the side windows when the curtains are opened during non-HT periods (see all the attachments) and is not acceptable to she-who-must-be-obeyed, the architect and the wife's "hairdresser" advisors.

The bottom line here is that I would like the majority of listening to be clean, intelligible and free of distortion with enough headroom to be able to take demanding passages in stride. I have had the displeasure of visiting some rather wealthy person's homes who show off their HT rooms and at average listening levels the SQ is terrible. I want to do better for my friend.

I know this is a PITA project and really appreciate all the help you have been giving. When it is done (in about a year) I will post pics of the results.

Thanks, and if you want to PM me, please do.

[ThomasW]

Since this fellow obviously has a couple buck$ here's what I'd do.

In the front corners make a floor to ceiling wedge. In each wedge build in the new 'WMTW', in addition put in a pair of either the 10"-12" RS drivers in the corners as true "woofers". Bi-amp these woofers and run them down to 60Hz, maybe a tad lower depending on how they integrate with the sub.

For the subs go with something that has more exursion than the PE RS drivers. Since TC-Sounds is bailing on the low buck DIY builders, go with a few of these....

http://www.acoustic-visions.com/~acoustic/products/subwoofer_drivers/CSS_SDX15/

I'll need to ponder what to use for the effect speakers.....

[PMazz]

Why not a L-C-R matched setup in the top of a window seat?

[Brian Bunge]

I was just thinking something along the lines of Pete's Media Center could work well.

[moniker]

Guys,

Again, I apologize for a monster post, but I think I have worked out a clever solution. It may sound crazy, but I think it will work. :B

We have 19' of window seat. With all that space, it could be used as storage. Why not have a flip top to the window seat and store the L, C, and R speakers in the window seat until used for HT? Then, when the room is not used as a HT, the speakers could be hidden away in the window seat. 8O

I broached the idea to the H&W and they liked it. Of course, my scheme is that after they do the "put it away" routine a few times (the speakers will be heavy), eventually the speakers will never be put away and the L, R and C will stay in the best place possible for the room. Heh, heh, heh.... sneaky. :T On the other hand, if they do put the speakers away after each use, upon next use they will probably place the speakers in the right places. Why not? If they have to move them anyway, why not place them properly? Heh, heh, heh.....sneaky. :T

Ok, so here's the deal. When in use for HT, a heavy vynil light-blocking curtain fronted with a heavy decorative curtain will be pulled across the front wall. In front of that, the screen will be dropped down. On each side of the screen will be the L and R speakers and just below the screen, in the center, will be the CC. The attachment here shows the new plan. 8)

It seems to me that the effect will be that of an acoustically dead front wall with the speakers effectively pushed up against it. So now for the original thread question. Should the L, R and C crossovers use BSC or not? Does anyone have any experience, comments, suggestions or theory about this?

I sure would appreciate Jon chiming in 'cause he is the crossover designer. ;x(

Next question - For HT use in this application which would be the smartest design? Modula MTM, NatP, or the new WTMW design? The electronics will not be super high end but will be high quality HT stuff with substantial amplification for good headroom. I am thinking 200+ watts per channel. Does this sound right, or is it too much amp power? Any suggestion for decent electronics for this system? And how about sub amplification, I am thinking Behringer A500's for that? Suggestions?

Next question - I am planning to have the built in subs directly below the L and R speakers and am thinking of a crossover to the subs at about 80 Hz to simplify the system because a lot of HT electronics have a fixed LFE crossover at 80 Hz (more flexible would be better but that is what is out there). What volume AS box for L, R and C is suggested to cross to the low Qt subs in this case?

Next question - should I consider crossing over to the subs at a higher freq because of the nearness of the subs and the advantageous load reduction to the L, R and C speakers? All non-subs will be used in the "small" mode.

And last Question - What about the surrounds and rear effectors. Any suggestions there?

This sure has been an interesting work up for me. I have never before had the chance to do a project like this and would like to get it right. With your help, and a lot of head scratching, it looks like we have come up with at least a reasonable solution. Now if we can fill in the details we should have a slam dunk here.

Thanks guys. I can't wait for your answers to the questions I have posed. I realize I have a huge bunch of questions and I appreciate your taking the time and effort to respond to me. But you guys have the skill, talent, and experience to help me get a decent job done with this project and save one more guy from the advice of an "expert" who wants to vibrate panels of sheetrock for good HT sound.

Thanks again...can't hardly wait. :T

[ThomasW]

The amount of BSC needed isn't simply a function of the absorption coefficient of the blackout curtain, it' a function of all the materials on all the surfaces in the proximity of the speaker.

Since the minimal difference in price isn't an issue for this builder go with the new small WMTW. A amp that delivers stout 100 watts or more will work fine.

The A500 doesn't really have enough power for subs in a room that big.

Electronics depend on whether or not he wants a receiver of separates..