Designing a built-in home speaker system

[MikeM]

I'm new here, couldn't find anything on search, but forgive me if it's been dealt with recently.

I'm turning an attic room into a home theater. Since I have the luxury of designing and putting in the walls myself, and hiding all the wiring therein, I thought it would be a great chance to build in the speaker system right into the walls. I have designed and built speaker cabinets before, but never an entire room.

I have the following questions:

1. I'm designing for Dolby 5.1 surround. Is there anything "higher tech" I should plan for? I really don't want to tear out walls, etc. a couple years later.

2. I've seen speaker enclosure design software. Is there public domain software available to model the room's natural frequencies or accoustic nodes. Perhaps I can solve potential problems by changing the geometry.

3. I suppose everybody has an opinion, but what drivers are best suited to home-designed projects?

4. Assuming an unlimited budget (that was a joke) what do you consider "must have" equipment. I'm thinking more in the category of interface and control rather than components. I have the basics (receiver, CD player, DVD player, VCR, TV).

Thanks for your help.

Mike Metzger

[AudioIsFun]

If you are going to be building the walls yourself, ideally it would be best to the speakers evenly away from the listener which would mean in a circle. It's probably not reasonable to build a circular room, but maybe just curve the front. I sat in a lecture from this gentlemen from DTS and he went over all the theatre designs since the beginning of theatres. All feature a circular front and back.

[Bill Fitzpatrick]

It's been over 20 years since it was discovered that speakers should be placed out into the room. Wall mounted speakers are for the unwashed masses.

[454Casull]

Though in-wall loudspeakers may have moot qualities, you can definitely put some sub drivers to work in a nice IB configuration. Great bass.

[navin]

Originally posted by MikeM
1. I'm designing for Dolby 5.1 surround. Is there anything "higher tech" I should plan for? I really don't want to tear out walls, etc. a couple years later.....

a. i'd consider 7.1 with 3 in fornt,. 2 inth side, 2 in the rear and atleast 2 subs if not 3 (1 in th rear).

b. how hi end do you want to get. is the system gonna be used for critical listening as well as AV/HT?

c. in wall sub are a plenty.

as far as in wall speaker there are many cos offering these systems for many years (even before the days of AC3, 5.1, THX and other AV.HT technologies). B&W for eaxmple has a large range http://www.bwspeakers.com/index.cfm/...0wall%20Series

in wall speakers have some limitiations. imaging may not be so precise. the range of drivers does not extend to the very critical (like VIfa's XT line etc..). In wall speakers esp. woofer need to be designed for that application. depth of drivers shouldbelimited to under 3", Qts of drivers can usually be quite high (0.6 and above), etc.

on the other hand if you are careful with wiring up the room and mixing in the decor u can end up with a discrete but very high quality audio system.

also there are many companies also offering surface mount options for example
http://www.bwspeakers.com/index.cfm/...0wall%20Series

[MikeM]

Thanks for all your comments. Very helpful. Wish I could do the round room idea. I'm thinking along the lines of building speakers into the corners of the room. The room dimensions are pretty small (about 6 ft. x 6 ft. with an 8 ft. ceiling) and I could use the space.

This will not be for critical listening, just TV/Movies and entertainment listening.

Any other design suggestions (besides 'go away' let's say)...

Mike Metzger

[catapult]

It's been over 20 years since it was discovered that speakers should be placed out into the room. Wall mounted speakers are for the unwashed masses.

That's a bit harsh. Many professional studios use through wall speakers. I don't think anyone who has listened to Jim Fosgate's reference multichannel room would fault the sound or consider him "unwashed masses."

Mounting the drivers flush with the wall with a large back volume (at least 4*Vas for a true infinite baffle) solves a number of enclosure and baffle related problems. Of course a speaker designed to be placed away from the wall will sound bass heavy if placed near the wall. The crossovers need to be designed for the application. The main complaint about flush mounted speakers is a lack of stereo depth and ambience. But that lack of ambience (reflections) is a good thing for multichannel where the ambience is either supplied on discrete tracks or extracted electronically with DPL2x or Logic7.

So, I say go for it.

[catapult]

I saved this from a thread at AVS when he invited some people over to demo DPL2 when it was brand new. At the time, he didn't have the side speakers connected although people said the imaging was good enough that they had to walk over there and check.

Thanks Kevin, bmoura, and phire3, for your nice comments concerning the PL II demo, it was a lot of fun!

Here is the list of the 2 channel audio material I played during the demo:

Whispers in the Dark (Yanni)
Tiny Geometries (Ray Lynch)
Oxygene, part one (Jean Michel Jarr)
Close Encounters (Tomita)
God of Thunder (Kitaro)
Reflections of Love (Hillary Stagg)
Hope Has a Place (Enya)
Fly Swatting cut from Ommaguma (pink Floyd)
Cows in the Barnyard, and Subway, Dolby surround encoded (provided by Dolby Labs)
Mama India (Andean Folk music, Group Aymaran, from Bolivia)
Angle of Music (from Phantom of the Opera)
Eye in the Sky (Alan Parsons)
Another Brick in the Wall (Pink Floyd)
I Get Around (Papa Doo Run Run, a take off on the beach boys)
Lemon Tree (Peter Paul, and Mary)
Goodnight, Irene (Vinyl recording, The Weavers Reunion at Carnegie Hall 1963)
Little Rock Getaway (Vinyl recording by Les Paul from the album Les Paul Now)

On music, and music video program material I used the PL II music modes. The center width control was set to the center position, the Dimension control set to full back.

I used the PL II music Panorama mode at times for a “wrap around” effect.

For movie soundtracks I used the PL II Movie mode.

Some notes regarding the system:

The System is Tri-Amped with three amplifiers per channel.

The crossovers are single pole passive filters placed at the amplifier inputs.

The amplifiers are push pull tube units of my own design with multiple (three) separate negative feedback loops.

The bass amplifier has bass equalization down to 15 HZ with a "twin T filter" equalizer.

The Tweeter amplifiers are 10-watt output RMS with 6L6 output and 6BQ7 driver tubes.
The Midrange amplifiers are 45-watts output RMS with EL 34 output and 6BQ7 drivers.
The Bass amplifiers are 60-watts output RMS with 6550 output tubes and 6BQ7 drivers.

The amplifiers are placed close to each speaker. The audio is fed with ordinary 300 ohm TV twin lead cable from the decoder. This wire was chosen because of the very low capacitance (approx 90 PF for 40 feet). It was necessary to shield 117 volts AC wiring when it parallels the Twin Lead cable, which is not shielded to eliminate hum.

All speakers use identical drivers. Each speaker system uses one 1-inch Seas Excel soft dome tweeter, two Seas 5 ¼ inch Midranges with phasing plugs, and eight ten inch woofers sold by MCM. The woofers have rubber surrounds, vented pole pieces, and treated paper cones. The tweeters are “set back” about one inch to provide “time alignment” with the midrange drivers. The enclosures are a very large infinite baffle with design with sound absorption material on all inside walls.

A custom made A/B switch with remote control is used to switch from the Tag to the Tube decoder.

The Tag decoder was fed from the optical digital outputs on the DVD and Laser Disc players.

The Tube decoder was fed from an outboard D to A converter for digital sources, and from a custom Phono preamp for vinyl.

For vinyl sources a low output Moving Coil Cartridge is fed to a custom made Phono Preamp of my design, which uses four 6922 tubes. A transformer with silver wire is used at the input of the preamp as a step-up device. The power supply is "shunt regulated" and uses one 6X4 rectifier tube and two 0A2 gas regulator tubes.

The room walls are covered with thick carpet, and carpet underpayment. The ceiling is a “drop ceiling” with one foot of fiberglass overhead for a bass trap. All speakers are flush wall mounted to reduce diffraction. The room is 24 by 34 feet with a 9 ft ceiling.

The large speaker enclosures are built into the four corners of the, which provides eight 45 degree angles instead of four 90 degree corners to reduce corner diffractions.

The center front speaker is placed in a cavity in the front wall. The tweeter and midrange drivers are mounted below the screen flush with the screen at an angle; the woofers are mounted behind the screen. The side speakers have not been installed, so I guarantee they were not working!

One final note, the tubes not only look “very cool as they softly glow in the dark”. They supply enough heat to warm the room on the coldest winter days here at 6000 feet high in the Rocky Mountains.


------------------
Jim Fosgate

[TNT]

6 ft, that would be soemthing like 1,8 meters or ?

Isn't that really small ?

/j

[Bill Fitzpatrick]

Originally posted by catapult
That's a bit harsh. Many professional studios use through wall speakers. I don't think anyone who has listened to Jim Fosgate's reference multichannel room would fault the sound or consider him "unwashed masses."

I retract my remark about wall speakers being for the unwashed. My mind was stuck in 2 channel mode.