Eric's DIY Audio Projects

[EricS]

Over time, I'll add some more details and images to this thread, but I thought I'd start off with a few images of my home theater system. It is a DIY system that has taken several years to build...

The overall theater room is 14 feet wide and about 24 feet long.

Front view of the theater:
http://www.facstaff.bucknell.edu/esantane/movies/frontpano.jpg

Rear view of the theater:
http://www.facstaff.bucknell.edu/esantane/movies/rearpano.jpg

The front speakers are open baffle and stand about 52" high and weigh over 120lbs each. The surround speakers are acoustic suspension and use the same mid-woofer as the mains. Each front speaker is driven by its own 125w Class-A amp (a clone of the X-Aleph amp from Pass Labs). I had Class-D amps driving the surround speakers, but had to replace them with other amps as my local power utility began using two-way automated communication system (TWACS) that bled noise into the amps and out through the speakers that just drove me nuts!

I'll provide some additional details and some construction pics of the amps and speakers in a little while.

Eric

[struth]

A fantastic set-up Eric.. very impressive :respect:

[Idlewithnodrive]

WoW. You obviously enjoy a good film :)

[Firebottle]

....and good audio to go with it, :respect: Eric.

:)

[Ali Tait]

Very nice, lovely job!

[Macca]

Outstanding HT room - rear centre speaker as well, obviously taking it seriously ;)

Are the speakers your own design or taken from somewhere?

[walpurgis]

That's very smart Eric. Looks great!

[RichB]

Great theatre and something different from the usual Bose acoustimas type thing you usually see.

R

[agk]

Looks interesting Eric. More pics of the open baffles please.

[EricS]

No - I'm not a Bose fan...

As requested, here are some images of the open baffle speaker construction. It is not my design (I don't have the expertise), I am simply a copycat. They are a double layer of 3/4" MDF plus 18mm Baltic Birch. The outer red strip is 1x2" oak.

Here is a closer image of the front speaker:
http://www.facstaff.bucknell.edu/esantane/movies/AvroFelted.JPG

I ordered about a mile of 15ga wire to wind my own inductors for the crossovers:
http://www.facstaff.bucknell.edu/esantane/movies/IMG_3230.JPG

The glue-up was a bit of trick with the slanted sides of the cabinet:
http://www.facstaff.bucknell.edu/esantane/movies/IMG_3604.JPG

And the center channel presented a few challenges of its own for gluing:
http://www.facstaff.bucknell.edu/esantane/movies/RearBaffle1.JPG

Here is the center without the crossover installed:
http://www.facstaff.bucknell.edu/esantane/movies/IMG_7770.jpg

I added a few braces to the inside of the left and right speakers after discovering they vibrated a bit too much. I doubled the front baffle, I should have doubled the sides as well:
http://www.facstaff.bucknell.edu/esantane/movies/AvroBraces.JPG

I also added some metal shelf wall-brackets to the back of upright portion of the speaker to tame resonance. A double layer of wood and oak were not enough for the stiffness I was looking for. So I cut up the bracket, screwed it to the back of the baffle, and felted it with leftover scraps from when I felted the front:
http://www.facstaff.bucknell.edu/esantane/movies/AvroBracing.JPG

They require a little bit of power to really make them sing. As the volume level goes up, there is a discrete point where they just "pop" into an immersive 3D sound experience that I just love.

I'll post some images of the surround speakers next, to be followed by some details on the amps and room acoustic treatments.

Eric

[walpurgis]

Lovely job Eric.

(don't think we have any Bose fans here :). Mind you, I did like the first 901 speakers from over forty years ago)

[Firebottle]

Eric, even more :respect: from me, winding your own inductors.

Sounds like you know what you like, fantastic job :thumbsup:

[EricS]

Thanks for sharing your kind thoughts, everyone. It's surprising what an interest in DIY coupled with a pinch of OCD can achieve :lol: All in all, these project span about a decade or so.

[Floyddroid]

That looks amazing. Hats off to you good sir.:clapclapclap:

[awkwardbydesign]

Eric, even more :respect: from me, winding your own inductors.

Sounds like you know what you like, fantastic job :thumbsup:
I've done that. Which is why I buy them! Good man.
But I'm fascinated by the home theatre thing, as I'm not interested in films at home. I have DVDs I've been given for birthdays and never even unwrapped them! But then some people aren't bothered about music.

[EricS]

I've done that. Which is why I buy them!

Ha - There are two forces at work here. The larger of these two forces was looking at $400 for ready-made inductors or $150 for wire plus a coil winder :lol: The irony of the situation was that I was sitting on the couch winding my coils while my wife and I were watching an interview on TV where the interviewee was bemoaning the problem that no one makes anything anymore...

[EricS]

Here are some details on my surround speakers. They use the same midbass unit as the open baffles: Hivi M8A. The tweeter is a Focal TC120TD5. Here is a closeup of the completed speaker (without the felt on the front baffle):
http://www.facstaff.bucknell.edu/esantane/movies/CompletedSurround.jpg

Where would DIY be without Baltic Birch ply?
http://www.facstaff.bucknell.edu/esantane/movies/allcut.jpg

And the glue up (darn those slanted angles!):
http://www.facstaff.bucknell.edu/esantane/movies/clamped.jpg

All sides are double laminate of Baltic Birch and MDF:
http://www.facstaff.bucknell.edu/esantane/movies/DoubleWall.jpg

The front baffle is made from three layers:
http://www.facstaff.bucknell.edu/esantane/movies/3plybaffle.jpg

And with the crossover networks installed. sorry, no DIY coils on this one.
http://www.facstaff.bucknell.edu/esantane/movies/XOTest.jpg

A final touch was to brace the front baffle to the rear panel for additional vibration control:
http://www.facstaff.bucknell.edu/esantane/movies/BaffleBrace.jpg

The additional layers for the side panels were installed on the outside of the cabinet and colored to match the front speakers:
http://www.facstaff.bucknell.edu/esantane/movies/Orientation.jpg

The finished speaker was stuffed with lambs wool before the drivers were installed. These are incredibly stiff and heavy cabinets!

The completed speaker is just about one cubic foot in volume, stands about 19" tall, 11" wide and weighs in at about 55 lbs. The angled design allows it to be hung on the wall so the tweeters aims down toward the listening place and makes the bottom more recessed so no one bangs their head as they walk by. Two of them hang on keyhole hangers directly mounted to the stud (major pain to get them mounted!), and the other two are mounted on a header that spans two wall studs for proper placement. There is no baffle step in the crossover since they hang on the wall. Bass is clearly not their strong point, but they are superb for surround sound duty.

[petrat]

Very nice.
As the French say ... chapeau

[EricS]

Here are some details on my infinite baffle subwoofer. This bad boy is the real star of the show for action movies! It consists of four Tempest-X 15" drivers (technology from the now defunct Adire Audio) driven by a ~1000w Behringer amp. Each driver has a one-way X-Max of about 27mm, so the sub can displace about 16L of air at full stroke.

I constructed two wooden manifolds that open into the theater at the bottom of the screen and flank the center speaker. In the first picture I posted in this thread, you can see the wooden grille cloth stretcher frames on the wall behind the center speaker.
http://www.facstaff.bucknell.edu/esantane/movies/IMG_5729.JPG

Here is another shot "down the throat":
http://www.facstaff.bucknell.edu/esantane/movies/IMG_5722.JPG

The drivers face one another and the air exits the throat into the theater. Construction is the old stand by of Baltic Birch and MDF. I mounted a 2x2 crossbar to help keep the sides of the manifold from flexing and resonating too much.

Here are the twins before the drivers are installed:
http://www.facstaff.bucknell.edu/esantane/movies/IMG_5725.JPG

Installing the drivers makes each manifold weigh over 110 lbs. It was a major pain to drag them into the other room and get them properly placed in the cutouts I prepared. Each manifold is lagged to a vertical wall stud and to the supporting shelf on the other side of the wall. Because the movement of the drivers oppose one another, the forces cancel and the manifold structure itself is vibration free during even the most intense scenes. The rest of the house is not quite so lucky http://www.facstaff.bucknell.edu/esantane/movies/shakehousedown.gif http://www.facstaff.bucknell.edu/esantane/movies/hide.gif http://www.facstaff.bucknell.edu/esantane/movies/shakehousedown.gif
http://www.facstaff.bucknell.edu/esantane/movies/IMG_5734.JPG

The drivers have dual voice coils that are wired in parallel and the two drivers in each manifold are then wired in series. Thus, each pair of drivers presents an 8ohm load to the amp and receives just about 500w of power.
http://www.facstaff.bucknell.edu/esantane/movies/IMG_6074.JPG

Here is another shot of the frame I created to cover the hole I cut in the wall to install the sub:
http://www.facstaff.bucknell.edu/esantane/movies/ManifoldCover.JPG

And, finally, a waterfall plot of the response after a little parametric EQ was applied to tame some of the peaks in room response:
http://www.facstaff.bucknell.edu/esantane/movies/NewCorrectedWaterfall.jpg

The left side of the graph does not show all that this sub is capable of. Overall output easily hits 120dB at the listening seat and peaks at about 10Hz (room mode) and is just as strong at 7Hz as it is at 20Hz. I was simply awestruck the first time I fired it up after getting things dialed in! Good bass effects make your hair move - something I've never felt before I finished this sub! Movies take on a whole new visceral dimension. I'll post some details on the DIY amps next time around.

[tapid]

What times the first performance ? Very nice

[rikardo1979]

very impressive.especially as it is all DIY and done to very high professional standard
:clapclapclap::partytime:

[Sjobbe]

hahaha, that sub looks insane! very impressive work!

[JJMontague]

Very impressive, Eric! I wish I could dedicate a room to my theater. Mine shares the basement with our guest bedroom, a 2nd kitchen and dining room and an exercise space all in a large open room. Where do you source your baltic birch? I have to drive about an hour to get to a lumber yard that carries it.