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PVC Alpair 6 Pensil

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Hello,
I've a pair of Alpair 6 that I've used in OB with a H frame subwoofer.
Now I'm looking for a new house for this speakers.
I'm not able to use wood with good results and I'd like to make something different.
I'm thinking about a Pensil made with PVC pipe, I've seen many ideas on the net but I need some help for the right dimensions of the pipe.
Can you help me?
Thanks a lot.
Guglielmo
 
And do you think about the tuned port?
Do you know the tune frequency?

I'd worry if I didn't, for the excellent reason I designed them. ;)

I must calculate with the thichnes of the PVC and tune sperimentally (circular section) looking at the impedence curve?

Well you could. Alternatively, you could use the designed vent CSA and length. If the PVC pipe is too thin, just add a lip around the inside of the vent hole you cut to get back to the requisite 3/4in length.
 
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ABS Alpair 7

Bonjour diyAudio. This my first post...

I built two enclosures with black ABS pipes and fittings for the Alpair 7. ABS seems stronger and cheaper than PVC. Since these are my first diy speakers, I can't tell if the result is perfect, but I must admit that I'm very pleased. The sound is a bit aggressive in the mid range, but I guess I'm not used to full-range speakers. I plan to use DRC to equalize them, but I'm not in a rush. They're not finished; maybe I'll use passive filtering instead.
 
Pictures?

dave

Bonjour Dave.

I first wanted to build a Pensil, but your design for the Alpair 7 was not ready, then I was intrigued by the "triffid", a bass reflex enclosure:

http://www.diyaudio.com/forums/full...-chr-70-application-thread-9.html#post1802936

Rabbitz helped me a lot, his advice were priceless. My "triffidus" design is a bit different than the original "triffid", and as you can see it's not finished.

There's still no wooden base, and no binding posts (the cable goes out through the port)...

Only the top fittings are glued together; when the pipes are inserted into the fittings, it seems solid enough. They're easy to insert and remove after heating the fittings with a small paint stripper. Maybe I'll glue everything when I'm satisfied.

The second picture shows how the Alpair is attached to the ABS fitting. The diameter was almost perfect but I had to use a small file to cut little grooves. The screw holes are right between the fitting and the glued ring, and it's very solid. The whole interior is lined with 3/8" industrial felt (but only 1/4" around the basket).

The last picture shows how I listen to them; they stand behind a 32" HD monitor (a TV), spaced by 16" (from centre to centre) in a ambiopole configuration, driven by a T-amp and a Linux computer with cross-talk cancellation software.
 

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That make sense... Rabbitz mentioned that there could be boost around 800Hz), even with a thick felt liner.

But I don't know how the Alpair 7 sound in a "normal" enclosure; maybe there's not much difference. I would have to build a Pensil 7 to compare (and or measure the frequency response, something that, as a newbie, I'm not yet familiar with).

Do you think that :
- this could be fixed with DRC or passive EQ?
- these internal reflections can cause some sort of distortion?

Thanks for your help.
 
What would be an ideal wooden enclosure size, if it were to have a transmission line made out of ABS pipe attached and used as part of the stand?

I have some smallish, to be more precise, 0.19 cuft internal volume (329 cu in) left over from a JBL model 5 with a 5" woofer and a tweeter, nicely finished cabinets and will shortly have some EnABL'd Alpair 7 drivers and with their xmax it intuitively seems a good match.

Bud
 
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The very reason for the query. Tap test has found a need for nine rings across the driver, including two on the mounting fascia and two on the center dome. I intend to look for the most needed, as some of the changes are more dramatic than others and I worry about picking the phase up and bringing it out in front, on the top end, ala soongsc's original, many rings test, soooooo long ago now.

I could just put them in these boxes, which have a port tuned to a 5 inch (alleged) driver and see what happens, but I would be more happy with something that produces bass that suits the already crisp clean sound.

Bud
 
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When Chris found out i'd sent them, he said "Bud is gonna need a box for those :)"

We are doing a 2nd rev of the fonken-like enclosure for them now.

Let us know what you need enclosure wise.

One needs to be really gentle when tap testing these.

We are lobbying for a driver without the add-on bezel cover so that the transition from the surround over the bezel to the box is basically flat.

Despite the big bezel the driver is a nominal 4"

dave
 
Actually, anything you might have that will work well with the driver. If you are in the midst of designing / making them, I can just treat the drivers and bring them to the show.

The tap test was done with no force at all, just enough local sound to determine when the direction of emission changed. The tool was small, light and gently curved. There are no surface marks at all ,even under 7X jewelers glasses.

Bud
 
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