tallclyde said:
I'm going for a sloped U-baffle . I have a parallel thread running on AC . JohnInCR had some good advice for me there - check out http://www.audiocircle.com/circles/index.php?topic=39460.msg359618#msg359618
Regarding the dimensions, I'm trying to make the baffle relatively narrow (see fig). One foot is about as narrow as I can go (maybe an inch or so narrower, but that's it). I'm deliberately tapering the array at the top to give me the option of reverting to a transmission line type design or a K-slot design if needed. I also plan to brace the wings . One thing I'm not sure of (read John's post) is how to get an effective roundover without showing off all the ugly plywood plies). The wing taper dimensions were chosen for economy (I had a 4 x 8 sawn up into four 1 x 12 and some scrap) rather than specifically following any design. I also figure that by increasing the taper towards the bottom, we can get a bit of help from floor / corner loading (if I stay with the OB design).
An externally hosted image should be here but it was not working when we last tested it.
zobsky said:
One way is to glue a solid wood piece as the corner to roundover. You do need a gluing or nailing block inside the corner for something to attach the baffle and side to. The outside corner wood can be made as large as needed for the radius roundover you want. With large roundovers you need two glue blocks per corner
I've now routed out the cutouts for the woofers (cutout diameter = 4.75"). I left about 2 mm between the flanges.The center to center distance between the woofers is now 135 mm .
The woofer centers are 6.5 " from one end of the 12" baffle ie. slightly off-center.
I might also consider mounting the woofers a bit askew (see pic) for aesthetic purposes. I'll have to make sure that the tweeter frames don't overlap, though.
At this time, the baffles have 4 coats of danish oil and 1 coat of finishing wax on them.
The woofer centers are 6.5 " from one end of the 12" baffle ie. slightly off-center.
I might also consider mounting the woofers a bit askew (see pic) for aesthetic purposes. I'll have to make sure that the tweeter frames don't overlap, though.
At this time, the baffles have 4 coats of danish oil and 1 coat of finishing wax on them.
An externally hosted image should be here but it was not working when we last tested it.
I cut the wings too. Here's a mock up with the wings + baffle (in reality, the wings will be glued to the other side). I plan to paint or stain the wings dark to eliminate / reduce reflections from the projection screen in an AV setup.
An externally hosted image should be here but it was not working when we last tested it.
I've starting wiring the(70) tweeters. To avoid going insane during this task (or maybe it's already too late for that), I've decided to spread this job over the week @ about 15 per day.
I'm using cat 5 plenum for the wiring since I don't foresee an individual tweeter receiving more than a few milliWatts each . Using audio-hype approved wires would drive the cost of the project through the roof.
Pig-Tailing the Tweeters
I'm using cat 5 plenum for the wiring since I don't foresee an individual tweeter receiving more than a few milliWatts each . Using audio-hype approved wires would drive the cost of the project through the roof.
An externally hosted image should be here but it was not working when we last tested it.
Pig-Tailing the Tweeters
I glued up the sides and painted two sides.
Three compromises:
* I decided against the roundovers for cosmetic reasons and also against cutting a 45 degree bevel (limitations of my tools).
*I glued the edges parallel to each other. If I end up with a standing wave resonance between the two parallel side walls, I'll glue in a 2 x 4 at an angle .
*The wings are of identical dimensions. If needed, I'll make one longer by tacking on a strip of wood.
Not the best picture, .. but you get the idea
Three compromises:
* I decided against the roundovers for cosmetic reasons and also against cutting a 45 degree bevel (limitations of my tools).
*I glued the edges parallel to each other. If I end up with a standing wave resonance between the two parallel side walls, I'll glue in a 2 x 4 at an angle .
*The wings are of identical dimensions. If needed, I'll make one longer by tacking on a strip of wood.
Not the best picture, .. but you get the idea
An externally hosted image should be here but it was not working when we last tested it.
I've finished painting the sides and have started wiring up the tweeters
An externally hosted image should be here but it was not working when we last tested it.
planet10 said:
Hopefully, it won't be too long now . I got all the tweeters and woofers mounted this evening (using 236 screws, whew). The tweeters have all been pig-tailed. The woofers haven't but they are relatively fewer in number and easy to reach, so I plan to wire them up in-situ.
Thanks God for Cat 5 plenum . I'm not sure if the type of Cat5 matters, but I've heard of people using the plenum grade for audio related stuff, so that's what I stuck with here. It's "relatively" cheap and has 4 twisted pairs per cable. I used a single twister pair per driver.
Each tweeter line has used up about 6 ft of Cat5 (about 6-7" per tweeter). I foresee this project using about 18 ft total.
FWIW, I used a hinge bit to center the pilot holes for the woofer mounting screws. I'm not a tool junkie but investing in the correct tools really helps speed things along when building arrays, because much of the work involved is repetitive.For the record, I used #6 x 0.75" wood screws for the woofers and likewise, #4 x 0.5" screws for the ApexJr tweeters. All purchased at my local Home Despot (where the cashiers can't differentiate between a 2 x 4 sheet vs 4 x 8 sheet , .. this is the truth ).
Here are some pics:
Woofer frame/magnet damped with plumbers putty
An externally hosted image should be here but it was not working when we last tested it.
The twins, ...
An externally hosted image should be here but it was not working when we last tested it.
zobsky said:
Hope you had a nice electric drill for that (i have a bunch of 4V Makitas which are perfect as screwdrivers
It is nice to be able to lean on the billions of miles used for networks to be able to buy state-of-the-art quality for pennies... if it was only being used by hifi nuts for speakers wire it would be $50 a metre of some such.
I note that you didn't relieve the back of the woofer cut-outs....
dave
planet10 said:
Yes, .. 6A DeWalt Corded , .. fine fine piece of equipment.
I agree. I know I should have rounded out / chamfered the rear of the cut-outs. Chalk that one down to laziness. I didn't have much heart for it after all those cut-outs + the round over router bit I had at the time was worn out.. Nevertheless , there's still a fair amount of space for the rear-wave to "breathe" though a roundover would have helped.
Now, If I were using the audax or hivi A3S that I was initially considering, rounding over the rear of the cutouts would've been pretty much mandatory.
zobsky said:Thanks, .. I saw that a few weeks ago @ http://www.caraudio.com/forum/showthread.php?t=208488 (enjoyed reading the holy war too, .. it's amazing how uninformed some people are, even compared to yours truly)
Well that forum's moderator appears to be about 14 years old, give him time to mature a bit
I dragged one of the arrays up for preliminary testing. I used my behringer active crossover in 2 way mode.
Haven't run through all the tests I want to , but here are my brief impressions.
Big Room-filling sound (similar to what I get from horns or my 15" Stephens co-axial). Not quite the sonic purity I get from single drivers, but pleasant to listen to and can get much louder. Wide sweetspot (perfect for the intended A/V setup)
1. The usual near field effect (music in the next room is almost as loud as in the listening room). The foster wide-ranges work, and work well. It's almost as though they're made for open baffle arrays. I get output down to the 40 Hz, though the woofers are complaining at that point. Easily useable from 80 Hz upwards. Although, at that point, we've lost some bass "kick".
In short, perfectly usable for acoustic music, .. could benefit from a subwoofer (or two) for music with notable bass content.
2. The tweeter line is smooth. Not a detail monster, but smooth and pleasant to listen to, . kinda like the "PSB" sound. I crossed over at 3.5 - 4 KHz @ 24dB/octave. It seems to me like the woofer line is as or more a little bit more efficient than the tweeter line, . not what I had calculated, or maybe it's just that there isn't that much detail up there above 5 KHz (yes, .. my hearing extends way past that ..) I probably need to set up a frequency sweep. The power meters on my amp (marantz 170DC) are idling at between 1 and 2 W at a fairly loud level of music
3. I haven't yet braced the rear of the cabinet or stuffed it to damp the mids / highs coming from there. I expect the sound to improve somewhat as I do this. As I mentioned at the start of this project, I have plans to play with T-lines / K-lines too .
More to come as continue to work on these.( I haven't even got these on stands yet)
FWIW, in the background, you can spy a full range corner firing array I built with some of those cheap drivers that user BillF. was selling last year.
Also, the horribly finished (I claim full credit for that screw ub) but decent sounding brown box is an efficient Fitzmaurice AutoTuba horn loaded sub.
Haven't run through all the tests I want to , but here are my brief impressions.
Big Room-filling sound (similar to what I get from horns or my 15" Stephens co-axial). Not quite the sonic purity I get from single drivers, but pleasant to listen to and can get much louder. Wide sweetspot (perfect for the intended A/V setup)
1. The usual near field effect (music in the next room is almost as loud as in the listening room). The foster wide-ranges work, and work well. It's almost as though they're made for open baffle arrays. I get output down to the 40 Hz, though the woofers are complaining at that point. Easily useable from 80 Hz upwards. Although, at that point, we've lost some bass "kick".
In short, perfectly usable for acoustic music, .. could benefit from a subwoofer (or two) for music with notable bass content.
2. The tweeter line is smooth. Not a detail monster, but smooth and pleasant to listen to, . kinda like the "PSB" sound. I crossed over at 3.5 - 4 KHz @ 24dB/octave. It seems to me like the woofer line is as or more a little bit more efficient than the tweeter line, . not what I had calculated, or maybe it's just that there isn't that much detail up there above 5 KHz (yes, .. my hearing extends way past that ..) I probably need to set up a frequency sweep. The power meters on my amp (marantz 170DC) are idling at between 1 and 2 W at a fairly loud level of music
3. I haven't yet braced the rear of the cabinet or stuffed it to damp the mids / highs coming from there. I expect the sound to improve somewhat as I do this. As I mentioned at the start of this project, I have plans to play with T-lines / K-lines too .
More to come as continue to work on these.( I haven't even got these on stands yet)
An externally hosted image should be here but it was not working when we last tested it.
FWIW, in the background, you can spy a full range corner firing array I built with some of those cheap drivers that user BillF. was selling last year.
Also, the horribly finished (I claim full credit for that screw ub) but decent sounding brown box is an efficient Fitzmaurice AutoTuba horn loaded sub.
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