DIY Speakers for on-wall behind screen?

[chirpie]

I tried searching for this, but came up empty handed. (Found one thread over a year old that never went anywhere)

I'm looking to change the front of my theater. (My first DIY project) It's currently speakers in front, screen behind.

http://www.facebook.com/media/set/?set=a.3254403514694.2151843.1105233204&type=1&l=b1031615b6

I want to sell the front three speakers and go with a DIY design that may be something like the Klipsch KL-650-THX or the JTR 8HT.

The priorities are as follows:

- Goes on wall. No baffle step correction.

- High Dynamic Rage

- Some finesse in music reproduction, not TOO frat house ;-)

- Can build 3 for roughly $1000-$1500

Additional details:

- I'd like them to be no deeper than 8 to 10 inches, but I have plenty of leeway in the width and height. (up to 20 inches wide and 50 inches tall)

- They don't need to go any lower than roughly 70 hz

- The screen material is SMX http://www.smxscreen.com/audio-measurements.html Not sure if I'd muck with the crossover to catch any characteristics of the screen


So the stupid question is, has anyone else ever tackled a project like this one? It shouldn't take as long to build as my clearwave rbrs (http://www.facebook.com/media/set/?s...3&l=b4fd4477ea) because I have no need to finish them properly. (Out of sight, out of mind.)

Any and all ideas welcome. :-)

[lhwidget]

My first thought is; Can you build a really sturdy "false wall" behind the screen?

This gets you away from all the wonky cancellations caused by a 8" to 12" offset between the speaker baffles and wall.

Second thought; If you have access to measuring equipment (or a friend with measuring equipment) you could install the speakers and screen, then take measurements for the crossovers with both in place. This should let you voice the speakers around any frequency response problems the screen might cause...

[cjd]

Ive got the design, just have to share it. 3 ways, RS180x2/RS150/27TDFC. intended for behind an SMX screen. I cross at 70Hz. Just did some RTA the other day and was surprised how flat they really are.

[chirpie]

My first thought is; Can you build a really sturdy "false wall" behind the screen?

This gets you away from all the wonky cancellations caused by a 8" to 12" offset between the speaker baffles and wall

The stage has 2,000lbs of sand in it, and it's two layers of 1/2 inch plywood with roofing felt, deck screws and liquid nails. It's a solid foundation to screw into. I'd build the false frame out of a combination of that and 2x4 (no 1x3, too wimpy) I think a solid screen wall is definitely attainable.

Second thought; If you have access to measuring equipment (or a friend with measuring equipment) you could install the speakers and screen, then take measurements for the crossovers with both in place. This should let you voice the speakers around any frequency response problems the screen might cause...

That I don't have, or any friends who are in possession of it. Which is why the next post left me so excited... ^_^

Ive got the design

Woo-hoo!

just have to share it.

D'oh!

3 ways, RS180x2/RS150/27TDFC. intended for behind an SMX screen. I cross at 70Hz. Just did some RTA the other day and was surprised how flat they really are.

Well dang, looking at the specs, that almost sounds… perfect? Weirdly perfect even.

I assume this is the driver grocery list in question?

Dayton Audio RS180-4 7" Reference Woofer 4 Ohm x6

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-374

$47.24

SEAS Prestige 27TDFC (H1189) Textile Dome Tweeter x3

http://www.madisoundspeakerstore.com/seas-soft-dome-tweeters/seas-prestige-27tdfc-h1189-textile-dome-tweeter/

$49.30

Dayton Audio RS150-8 6" Reference Woofer 8 Ohm X3

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-354

$39.45

Maybe 2 to 300 bucks in crossover parts?

Even with the enclosure and other odds and ends parts, that should put me at around $1,000 or slightly above if I'm not mistaken. Spot on.

Tell me to back off and be patient if you like, but might I ask a few questions?

What would be the average sensitivity of these speakers as well as the average ohm and max wattage loads? (I only ask because the midrange looks to be the weak link in the spl, but I guess if the crossover is high enough on the bottom end, it might be just fine)?

What's the proposed crossover points? I see the tweeter digs pretty far down, so there's flexibility there, but I was just curious.

No big rush on my part, I'm still a few months away, but I like doing a fair bit of advanced planning when I can. I also think this could be a popular DIY design with the A/V projector crowd. Between some Seymour AV DIY material and a project like this, you could be dropping jaws for around $1,300 bucks for the entire front wall. What an age we live in. ^_^

[cjd]

Pretty sure it's the 8ohm RS150. Ive measured 115dB sustained (with ear protection!) Though you're stupid to watch a movie that loud. I usually watch at 75dB... I'll see about digging up the design and sharing it finally. The screen is part of the design so not many folks would find it useful so I've just been super lazy. Also mine are full in wall with acoustic treatment on it. A false wall 4-6" behind the screen would be ideal. about 8" deep on the boxes. No sub in room was flat to 50hz on the RTA sweep.

C

[chirpie]

Pretty sure it's the 8ohm RS150. Ive measured 115dB sustained (with ear protection!) Though you're stupid to watch a movie that loud. I usually watch at 75dB... I'll see about digging up the design and sharing it finally. The screen is part of the design so not many folks would find it useful so I've just been super lazy. Also mine are full in wall with acoustic treatment on it. A false wall 4-6" behind the screen would be ideal. about 8" deep on the boxes. No sub in room was flat to 50hz on the RTA sweep.

C

That would be VERY much appreciated. My entire front wall is treated acoustically, so I can just move materials around as needed if/when I rip it all out. (I edited the link to the 8 ohm version for my own future reference.)

I just need to do some measurements on the can lighting to see if I'll need to move/rewire them. It's double dry wall with green glue and boxes built around the lights, so I really hope I don't have to do that. ^_^

[lhwidget]

Sounds like you're set. I can't think of a better way to do this. cjd's designs are very good

By the way, nice theater! I hope you post some pics of your build.

[cjd]

Looks like I have to open the project files with the M-Audio sound card wired up (something about the stock one fails to work properly with SW when it's a file I'd used for taking measurements. Go figure.) And I haven't gotten to that yet. But I do remember.

[chirpie]

Looks like I have to open the project files with the M-Audio sound card wired up (something about the stock one fails to work properly with SW when it's a file I'd used for taking measurements. Go figure.) And I haven't gotten to that yet. But I do remember.

Entirely at your discretion good sir, seeing as you're helping me out. Very much appreciated. :-)

[chirpie]

By the way, nice theater! I hope you post some pics of your build.

Thank you good sir! This will be a turtle project, and I will need to rip part of the ceiling out, but I'm not afraid. My wife might be though. Poor girl. :-)

[royceb]

I'm kind in the same boat as well. I've decided to do the acoustically transparent screen with three of the same speaker behind it. Right now, my thought was to build a third NatP to go with the two I have now but cjd's design has me interested as well.

[cjd]

Thanks for the reminders.

[agrippa]

You might check these out. they come in kit forms from madisound

http://zaphaudio.com/ZA5/

They have an inwall and car version as well.

[agrippa]

sorry cjd. I didn't see you post. I look forward to what you come up with. Your designs are very nice

[lhwidget]

Thank you good sir! This will be a turtle project, and I will need to rip part of the ceiling out, but I'm not afraid. My wife might be though. Poor girl. :-)

My mother-in-law kept turtles. If her's ever built speakers, they kept them in their tunnels under the garden, I never saw any.

You have exceptionally gifted turtles...

:rofl:

[cjd]

The page is still a WIP but...

http://www.divine-audio.com/ht-mains/

C

[fbov]

cjd - I CAN SEE THIS PAGE!!!!! (and from work where eldamar is not allowed) bookmarked

I'm kind in the same boat as well. I've decided to do the acoustically transparent screen with three of the same speaker behind it. Right now, my thought was to build a third NatP to go with the two I have now but cjd's design has me interested as well.

If you have the thought to build a third NatP, even if you'd keep it upright, I'd suggest a Modula CC in its place. Jon did something to that design that improved dialog tremendously over the NatP's (on-axis where I sit and lobing's a non-issue, as well as in the wife's far off axis seat) plus addressing virtually all lobing issues, so perhaps orientation doesn't matter (not a first for Jon).

If the highs are muted behind the screen, reduce or remove R3 to increase tweeter level slightly, in case you weren't aware of that option.

HAve fun,
Frank

[cjd]

cjd - I CAN SEE THIS PAGE!!!!! (and from work where eldamar is not allowed) bookmarked

Nice! I bet someone found my sketchbook and said "NUDE PHOTOS" and that was that...

Poor bears, zebras, elephant, ... er... ok, there are a couple people too.

C

[royceb]

cjd - I CAN SEE THIS PAGE!!!!! (and from work where eldamar is not allowed) bookmarked


If you have the thought to build a third NatP, even if you'd keep it upright, I'd suggest a Modula CC in its place. Jon did something to that design that improved dialog tremendously over the NatP's (on-axis where I sit and lobing's a non-issue, as well as in the wife's far off axis seat) plus addressing virtually all lobing issues, so perhaps orientation doesn't matter (not a first for Jon).

If the highs are muted behind the screen, reduce or remove R3 to increase tweeter level slightly, in case you weren't aware of that option.

HAve fun,
Frank

Thanks for the recommendations! I'll give up some thought.

[gdub25]

Ive got the design, just have to share it. 3 ways, RS180x2/RS150/27TDFC. intended for behind an SMX screen. I cross at 70Hz. Just did some RTA the other day and was surprised how flat they really are.

I have a very similar need to chirpie and it sounds like these speakers would be the perfect fit behind my audio transparent screen. Are there still plans on sharing the design? I checked out the link to cjd's website and didn't see any information for behind screen speakers there. Did I overlook it by chance?

If building these speakers isn't going to be an option, I was planning to go with some Natalie P's and a Modula MTM center channel. Any big problem with going this route for a behind screen application? I'm new to speaker building as well as home theater in general. Through reading over the past few months I've learned a ton, but no where near enough to do this without some guidance.

[cjd]

I linked it above. http://www.divine-audio.com/ht-mains/ I just realized I need to post box info and driver layout. Tomorrow if I can remember.

[---k---]

Link broken. Page not found.

[cjd]

Link broken. Page not found.

Oops. It was there, just not published for anyone but me to see? Should be there now.

[gdub25]

I've tried to put together a BOM for these, but since this is my first time trying to build my own speakers, I'm not sure about a lot of it. When getting parts for the crossover, is it simply a matter of buying resistors, caps, and inductors with values that match those on the plans, regardless of the brand or type? I saw that all the inductors used were 18ga Jantzen, but past that I just started guessing. For example, when I look at capacitors at Parts Express, there are 9 categories to choose from including the different brands and types. I tried to find the cheapest of each part to try and keep cost down. Is this acceptable or will it cause trouble?

[lhwidget]

I've tried to put together a BOM for these, but since this is my first time trying to build my own speakers, I'm not sure about a lot of it. When getting parts for the crossover, is it simply a matter of buying resistors, caps, and inductors with values that match those on the plans, regardless of the brand or type? I saw that all the inductors used were 18ga Jantzen, but past that I just started guessing. For example, when I look at capacitors at Parts Express, there are 9 categories to choose from including the different brands and types. I tried to find the cheapest of each part to try and keep cost down. Is this acceptable or will it cause trouble?

cjd will have the best answer for your questions, but there are a few general rules of thumb/schools of thought on your questions.

For inductors, wire gauge (which controls the coil's DC resistance) and inductance values are both important. Stick with air core types when air core types are used in the schematic. Subbing a metal core will substantially reduce the inductor's resistance and could affect the XO's performance.

For caps:
1) Non-Polar capicitors are required. Standard electrolytic are polarized and will fail.

2) Non-Polar electrolytic (NPE) are a special design sub-class of std electrolytic capacitors, and they can be used. Most designers at cjd's level of expertise tend to not use these, or only use them where larger values are required. It depends on your cost threshold, values above 20 µF start getting pretty expensive, and the cost increase isn't linear, but all film type caps are more expensive than their NPE equivalents.

3) The "film" type (poly, polypropylene, metalized film, etc) are non polar and typically considered the best to use. These caps will outlive NPE's and are considered by most designers to sound better. Another advantage is greater accuracy in the listed value of the cap. NPE's are typically speced with +20% tolerances, film caps are typically rated at ± 5% or 10%. Parts Express offers a fairly cheap line of film caps rated at ± 1%.

If I was building a cjd design, I would at least use film caps in the tweeter/mid XO, and only resort to NPEs for the largest values in the mid/woofer XO.

If cjd offered any advice, I would follow it accurately.

EDIT:
By the way, to get the odd values required in the XO, buy caps that add to the value required and wire them in parallel. Like for the 39 µF cap you could use one 30 µF cap and three 3 µF caps, twist the leads together, and treat it like one 39 µF cap.

If this kind of accuracy is needed, I'd recommend the PE 1% polys.

[chirpie]

(I haven't gone anywhere, just lurking at the moment. Thanks cjd!)

[gdub25]

Thank you very much for the information. That certainly got me started in the right direction. I've put together a Bill of Materials that includes everything I need...I think. I'm not confident I know what all the symbols on the crossover design are but I think I got it. Anyone mind taking a look and making sure this looks accurate? This list is for the first crossover design on the page. It looked the simplest, and the others are mentioned to possibly cause problems with impedance. As a beginner I think it would be best to keep it simple.

[U]DRIVERS[/U]

6	Dayton Audio RS180-4					([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=295-374&scqty=6] 295-374[/url])
3	Dayton Audio RS150-8					([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=295-354&scqty=3] 295-354[/url])
3	Seas Prestige 27TDFC Textile Dome Tweeter	([url=http://www.madisoundspeakerstore.com/seas-soft-dome-tweeters/seas-prestige-27tdfc-h1189-textile-dome-tweeter/] h1189[/url])


[U]CAPACITORS[/U]

3	Dayton Audio 1.0uF 250V Polypropylene	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-410&scqty=3] 027-410[/url])
3	Dayton Audio 2.0uF 250V Polypropylene	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-414&scqty=3] 027-414[/url])
3	Dayton Audio 6.8uF 250V Polypropylene	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-424&scqty=3] 027-424[/url])
3	Dayton Audio 12uF 250V Polypropylene	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-430&scqty=3] 027-430[/url])
3	Dayton Audio 20uF 250V Polypropylene	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-436&scqty=3] 027-436[/url])
3	Jantzen 39uF 400V CrossCap			([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-946&scqty=3] 027-946[/url])
3	Jantzen 68uF 400V CrossCap			([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-952&scqty=3] 027-952[/url])


[U]INDUCTORS[/U]

3	Jantzen 0.25mH 18 AWG Air Core		([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=255-214&scqty=3] 255-214[/url])
3	Jantzen 0.27mH 18 AWG Air Core		([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=255-216&scqty=3] 255-216[/url])
3	Jantzen 0.75mH 18 AWG Air Core		([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=255-240&scqty=3] 255-240[/url])
6	Jantzen 4.5mH 18 AWG Air Core		([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=255-282&scqty=6] 255-282[/url])


[U]RESISTORS[/U]

3	Dayton 10 Ohm 10W Precision Audio Grade 	([url=http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=004-10&scqty=3] 004-10[/url])

One thing I noticed was the Dayton caps are 250V, and the Jantzen are 400V. This ok or do I need to do like lhwidget mentioned and add caps together to get the odd values?

If this kind of accuracy is needed, I'd recommend the PE 1% polys.

I put this together before reading your recommendation so I haven't used the 1% caps in this list. If they are really needed I can refigure, but it looks like they cost quite a bit more and I'm already stretching my budget as it is.



cjd, big thanks for this. Also, not to rush, but any update on the box info?

[Hdale85]

Higher voltage should be fine.

[cjd]

Huh. My comments on the crossover parts disappeared. The parts list looks right.

I'll try to draw this up shortly but in the end the baffle layout and box volumes are the key. Every install may be slightly different in need as far as depth.

The boxes I did are 7" deep internally. Can't go too much less and have room for anything behind the woofers to manage reflections off the rear surface.

Do try to leave space behind the mid and woofers for foam or fiberglass, and some air space too. Need to allow that airflow.

Drivers are vertically aligned (you can offset the mid-tweet ~1" either way as well, just keep the to vertically aligned.) 1/8" spacing between mid and tweet, 1.5" space to the woofers.

Volumes here are minimum; you can go bigger quite happily. You can go smaller if required but not too much smaller.

Total 40L+ for the RS180-4's. 20L+ (.7cu/ft, 1220cu/in) volume per RS180 since you may need to split the space. F3 of 60Hz. Sealed.

5L minimum for the RS150 (.175cu/ft, 305cu/in). Sealed.

[gdub25]

Space isn't really of any concern for me. I have 24 inches between my screen and wall so boxes can be as deep as needed.

I've got a lot more reading and learning to do before I'm ready to tackle this, but if you post up a box design that would really helpful. Our house is still bein framed right now so I've still got a couple of months to get this together. I'm kind of hoping chirpie will get started before me so I can follow his lead.



Thanks again.

[chirpie]

Just wanted to say I'm not dead. Work just seems to gobble up my free time with reckless abandonment.

I'm gonna start drawing up some plans on the room modification and will post them in the near future.

[gdub25]

I was hoping you'd beat me to building these so I would something to follow, but it looks like I'll be getting started first. Construction of our house will be done in the next month and we'll be moving in soon after. I plan to start building these speakers right away but am going to need a fair amount of help from the more experienced here.

[cjd]

Just holler. I'm on the edge of nowhere right now (Hawaii) so may not always respond quickly...

Hoping to discover I'm still alive out here but who knows.