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What do you guys/gals think of PVC for FR enclosure?
What do you guys/gals think of PVC for FR enclosure?
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Old 7th November 2017, 11:45 PM   #71
Think is offline Think  Netherlands
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What do you guys/gals think of PVC for FR enclosure?
Interesting topic; I made 4 PVC pipe speakers with 10cm (~4") rain gutter PVC pipe and 2 end caps each. Driver to the back of the PVC end cap in which I drilled a 6,9cm (~2 3/4") hole and mounted a wire mesh fan grill (computer style) to them with the same 4 bolts and nuts on the front. I used Visaton FRS 8M drivers.
I tested them in different lengths (10,20 and 30cm which were acceptable in WinISD) and settled with the shortest.
I also put in pillow stuffing from a little to completely full but ended up without, just bare pvc. Standing waves from the back end cap are no problem as the driver magnet is bigger then the hole in the front on where the speaker is mounted.

With 2 on each side and the upper ones rotated inwards, I get a very nice coverage of the highs as well, but there is not much 'air' and they all highs sounds alike.
I'm going to upgrade them with some tweeters
which probably will be crossed over in the 5k-7k range. (above vocal range)


The magic of using round or cylindrical boxes is that they are extremely strong, and they brake up pressure waves perfectly. Compare a 'round' with a rectangular garbage can when you fill them with water... the rectangular one will deform, the cylindrical won't.

No matter how thick you make a squared box, it will deform more then a much thinner walled cylinder made of a the same material. The force of bending is complete annihilated by the cylinder shape.

(sorry for my English)
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Old 8th November 2017, 03:12 PM   #72
Dr1v3n is offline Dr1v3n  United States
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I plan for no filling to start with. I do have some felt and acousti-stuff on standby tho. I'll listen and find out if there are any objectionable sounds. The rectangular boxes I have the P7's in now are also bare internally. The slight 'boominess' was not objectionable, but noticeable.

Now on to mass production. I have to transfer the drivers, wiring and binding posts for 16 enclosures. I only have 4 tubes painted. It's raining today, was hoping to paint before assembly but that's not possible and I am eager to start although this means total reassembly and paint in the future.
Also, I was shorted hardware on 4 of the binding posts... I should be able to wire up all 12 drivers next week. For now I'll be listening to 8 tubes per side, even though you'll see 12 tubes, in a soon to be posted pic, mounted to confirm spacing... Thanks for visiting!
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Old 8th November 2017, 05:19 PM   #73
Think is offline Think  Netherlands
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What do you guys/gals think of PVC for FR enclosure?
I started with no filling, but found my drivers sounded harsh, but that seemed to have come from not being driven in. With time, lows got better, highs less harsh and I removed the filling.
If you use rectangular boxes, it's probably best to make their sides in different lengths. I like to use the golden ratio 1 : Phi (~1.62) whenever possible. This ratio is not only pleasing for the eyes, but also creates the least resonances (box noise) in a box.

You could also experiment with spiraled arrays to get a better horizontal coverage of the highs.

Tip: Keep your drivers as close as possible for the most coupling and least combing effects.
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Old 8th November 2017, 07:11 PM   #74
Dr1v3n is offline Dr1v3n  United States
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Quote:
Originally Posted by Think View Post
...Tip: Keep your drivers as close as possible for the most coupling and least combing effects.
I've tried this with all drivers equally spaced and aimed straight forward. With my small room, I could hear the combing effect when I raised and lowered my ears vertically about 3 ft away....
You do know I can angle each speaker enclosure at any angle vertically? As they are magnetically attached. In previous experiments, a slightly convex arrangement got rid of all anomalies, very smooth vertical and horizontal. Which is one reason I have high praise for the MA P7 drivers and still design around them in this fashion with even more drivers.
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Old 8th November 2017, 08:16 PM   #75
Dr1v3n is offline Dr1v3n  United States
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One side done. Still need external wiring/painting. Took over 4 hours just for 1 side deconstruct/reconstruct
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Old 8th November 2017, 08:49 PM   #76
planet10 is offline planet10  Canada
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What do you guys/gals think of PVC for FR enclosure?
Looks much tidier

dave
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Old 9th November 2017, 10:24 AM   #77
Dr1v3n is offline Dr1v3n  United States
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It does look better, hopefully will sound EVEN better...
But I do notice from the last pic itself even, each tube is not precisely lined up vertical. This is because I'm only depending on 1 screw to connect the base magnet to the tube and both surfaces are not flat. I think 2 more screws per mount are in order to properly aim each one horizontally. Shouldn't be too difficult (I hope). The lazy part of me wants to use drywall screws despite the coarse threads, which I have on hand. I will try this first, after all I'm just drilling holes. If they don't work, I'll get fine thread stainless steel screws and nylon locknuts.

Cheers!

EDIT: I will figure out why my camera take such crappy photos!!

Last edited by Dr1v3n; 9th November 2017 at 10:27 AM.
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Old 9th November 2017, 04:36 PM   #78
chrisb is offline chrisb
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I wouldn't recommend drywall screws - they're very easy to snap off, then you're totally pooched. In our commercial millwork / cabinet shop, we exclusively use Robertson Brand Lo-Root screws - similar to Lo-RootŪ Screws - Lee Valley Tools

They're worth every penny.
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Old 11th November 2017, 09:30 PM   #79
Dr1v3n is offline Dr1v3n  United States
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Thanks chris...
Construction complete. Wiring them up. Each side has 12 8ohm drivers.

Decided for each 3 drivers in parallel for 2.66 Ohms, then wire each group of 4 total in series. Total impedance approaching 11ohms.

Been listening to HDTV built in speakers. Absolutely terrible, but does show contrast. Can't wait!
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Old 12th November 2017, 02:53 PM   #80
Dr1v3n is offline Dr1v3n  United States
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Definately needed EQ. Too much Mid from the P7's. Currently EQing them, but tempted to get 2 more 8" Dayton subs per side to 'naturally' EQ without the DEQ2496. I have another Audiosource Amp3 to put to the task. Crazy, I now understand why these array guys are all about DSP.
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