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bostarob 20th June 2002 07:13 AM

In wall speakers
I am helping my neighbor, Dana, an experienced woodworker, design and build a home theater. It is going to consist of five in wall speakers and a sub. The in wall speakers have a seas tweeter and an audax 5 1/4" woofer. The woofers will go in a ported box of a little less that .2 ft3 and have a f3 of around 80 Hz (very well damped speakers, total Q is .25). The sub will be a blueprint 1201 powered by a dayton 250W sub amp. The amp has a variable lowpass xo that I can match to the speakers' mechanical roll off.

Now I have never done an in wall speaker before. What do I need to know? Vibrations?
I also need some help with the mid/tweet crossover. The 6 ohm tweeter is about 2db louder than the 8ohm woofer. I also want to cross over as low as possible to keep dispersion at a max.
I would flatten the woofer's impedence, adjust tweeter level, and make a 2nd order LR filter centered at 2.5 kHz. That's about all I know how to do. No baffle-step, because it doesn't really have a baffle.

What would you guys do? I don't have much in the way of measuring equipment(SPL meter, frequency generator/counter, and a multi-meter), and I'm not buying anything unless it's really really cheap:D .
Thanks in advance,

pinkmouse 20th June 2002 12:15 PM

Hi Andy,

Sounds like an interesting project...

I don't know much about crossovers, but this sounds to me like an ideal use for actives, that way you should be able to set your levels easily with gain pots, and just using tones and your level meter around the crossover point get a fairly good balance, as any variations in sensitivity of your spl meter are liable to be at the frequency extremes, and therefore you shouldn't need to work out a correction curve for any measurements taken.

As regards boxes, the main influence will be the depth of the wall, as having the rear panel of the enclosure too near to the front could result in reflections interfering with the drivers and causing cancellations, etc.

If you have a shallow stud wall, I would mount an angled baffle behind the driver to defelct the rear radiation from the driver down (or up!) away from the driver.

Fixing the enclosures into the wall would be a matter of trial and error, as it all depends on how rigid each wall is, and they all likely to be different.

If you have masonry walls, you should mount each one directly to the wall, as this will maximise damping of the enclosure.

With stud walls, screwing directly to the framing may prove effective, or it may be worth using a surrounding box lined with stiff foam, such as flightcase foam, in which your main enclosure is a very tight fit.

hope this gives you some food for thought...



Bill Fitzpatrick 20th June 2002 03:41 PM

It took some years for the concept of speakers AWAY from the walls to finally settle in. Now, no serious audiophile type would place their speakers against a wall.

Home theater arrives and people are mounting speakers in the wall! I don't get it.

pinkmouse 20th June 2002 07:39 PM

Ah, but speakers in walls could be ideal, just think no edge diffraction problems, and the achievability of rigid mounting, not to mention all the cables, stands and speakers cluttering up the floor,( increased wife/partner approval factor!!!).

However you do lose all the tweakability of changing cables, stands, toe in etc..


Bill Fitzpatrick 20th June 2002 09:32 PM

:( Sigh

pinkmouse 21st June 2002 12:27 AM

Just think Bill, it could be worse, I haven't picked you up on the spelling of theatre...

Seriously though, any theoretical types out there who can give us an educated viewpoint?


Bill Fitzpatrick 21st June 2002 01:32 AM


Theater, as I have spelled it, is correct. Consult a dictionary if you don't believe me.

In-wall speakers are for the masses, it make the requirements of multi-speakers more digestible. For almost two decades now, audio reproduction perfectionists have known that speakers against a wall are a no-no if a believable sound stage is to be established.

I had heard a rumor that one person still has their speakers in the corners of the room. Are you that person?

pinkmouse 21st June 2002 01:51 AM


Yes, if you use Websters rather than the Oxford English Dictionary, ( grins and ducks!)

Seriously though, I have speakers set well into the room with loads of toe in to get a good stereo soundstage in my room, and I know what you're saying, but I am open minded enough to wonder if in wall speakers may have some of their own advantages.

I don't know, I have never tried it- have you?



Bill Fitzpatrick 21st June 2002 04:57 AM

I didn't notice until now that you are in the UK. We'll call it a draw.

Sure, in-wall speakers have their advantages as you well pointed out; no stands, no wires to trip over, etc. And, there is no reflection from the rear wall to provide a delayed signal which, when combined with the direct sound from the speakers, can add to or subtract from the already existing irregular frequency response due to the reflections from the floor, side walls, ceiling and rear walls. In addition, in-wall speakers, particularly if they are in the corners and even more so if they are in a tri-corner do sound quite a bit louder, perhaps an important point considering some of the wimpy home theatre electronics available.

So, back to Bostarob. You ask what we would do, home theatre wise.

Here's what I do. I don't have in wall speakers. I bi-amp. I don't have ported speakers. I have 2 12" woofers per channel. I avoid 5.1, 6.1 or 7.1 and I guess next week they'll have 8.1. I don't want anyone but myself to manage my bass. My home theatre system kicks *** and does so because I have avoided all the ********. My VHS driven system beats the **** out of every DVD HT system I've every heard and I saved a ton of money. It is my opinion that current home theatre technology sucks. Remember when CDs first arrived? Just awful sounding. Now we get to do it all over again; lots of fluff and bells and whistles but no meat. Gentlemen, we are being taken for a ride . . . again. Promises, promises, promises and the check is in the mail.

planet10 21st June 2002 07:28 AM


Originally posted by Bill Fitzpatrick
I didn't notice until now that you are in the UK. We'll call it a draw.
In Canada we say that "theatre" is the Brit spelling, and "theater" the Yank spelling, and then go ahead and use either.

In wall speakers have some big advantages. I have built a few hang-on-the-wall-like -a-picture speakers, and own a semi-commercial pr designed by a friend. Because they are at a room boundary they cause maximum excitement of the standing wave that they sit at the end of. This can make them tricky to sound right -- if you are designing the room you could make sure the far end of that axis is severely non-parallel.

They can be made to image -- it's just not as easy as when you can pull the speaker out into the room. You should build the speakers into an appropriately thin/wide enclosure that is independent of the walls, and placing them in front of the wall listen and tweak their placement before you commit to installing them. If the box is of any volume it will get tall and you may want to take advantage of the 1/4 wave resonance.


PS: Bill, your signature is almost the same as mine -- i know where mine came from, where did yours :^)

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