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#1 of 15 OFFLINE   MikevZ

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Posted September 01 2005 - 04:13 PM

Hi All,

Long time lurker, first time poster.

I need some new mains for a second stereo setup. Bit of a fan of doing stuff myself, I built my surround rears from a kit and am keen to give it a shot for some new fronts.

Don't need anything huge (don't have much room), just a simple 2 way bookshelf unit. I have found a couple of Vifa 5" CW2100's on special, which will do for the midrange/woofer. I can get a Vifa tweeter unit and crossover easily as well (tuned to the tweeter) - as I can't imagine building the crossover myself. Actual construction would be ok, but I don't know what I'm doing for the planning side of things.

What I wanted to know was, how successful have people been in creating the 'boxes' out of Sonotube, PVC etc..? I kind of like the thought of having two different sized tubes, one for the woofer, one for the tweeter, fixed together to form the speaker.

Advantages would be that the tweeter would sit in it's own tube, so wouldn't be subjected to air pressure waves from the woofer and they'd be strong and easy to make.

Any suggestions as to the material to use? I'd imaging I'd have to damp them down a lot and figure out a good way to mount the two tubes together (maybe cut a groove on one of them)..

Throw some suggestions at me!

Thanks -Mike

#2 of 15 OFFLINE   SteveCallas

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Posted September 02 2005 - 01:25 AM

That idea is exactly what I was talking about in the other DIY mains thread, except with more drivers. Once you have the drivers mounted to the tubes, build a normal speaker cabinet. Then, have braces inside the cabinet, but with circle holes cut out for the size of the sonotube for the tweeter, and a larger one for the sonotube of the woofer. Line the inside edge of those holes with weatherstrip to ensure no chattering. I'd stuff the tubes with poly batting.

I don't know if this has been done before, but I would imagine it would sound pretty good and have no internal resonances. When you put your hand on the cabinet, you shoudln't feel any vibrations at all. Also, you could still port the woofer enclosure, just make the hole in the MDF for the end cap of the tube match up with a hole in the outer cabinet, and place a port through both holes.

#3 of 15 OFFLINE   MikevZ

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Posted September 02 2005 - 06:02 PM

Hi Steve, sort of on the same track. I thought it through last night and will do the following:

- Whole cabinet is one cylinder - no box required
- Woofer and tweeter mounted on front end plate (1" MDF)
- Port installed somewhere on cylinder body
- End plates will support cylinder body... ie.. integrated leg
- Crossover to be mounted on rear end plate

Bought the drivers and tweeters today to ensure I didn't miss out on the Jaycar special. The Vifa's were only $29 each.

My father-in-law will rebate the MDF to sit properly and seal the tube, as well as create a routed rebate for the driver and tweeter.

I need to figure out:

- Where to place the port
- Exact length of cylinder
- What to use if I can't find Sonotube or suchlike
- Crossovers...

Surely someone's done this before - anybody know of anything?

Cheers -Mike

#4 of 15 OFFLINE   SteveCallas

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Posted September 03 2005 - 01:33 AM

Ok now you lost me - what advantage are you gaining by doing this? Or are you just doing it because you don't want to build a cabinet?

What you were originally planning, with each driver in its own tube, appears to have many advantages.

#5 of 15 OFFLINE   Chris Lanni

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Posted September 03 2005 - 04:57 AM

How about this?

Parts Express Showcase

Close to what you want to do, minus one driver.

Gods Love
chris

#6 of 15 OFFLINE   MikevZ

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Posted September 03 2005 - 05:03 PM

STeve - yes, that's the point. I was looking for a way to get around building a cabinet, as I'm under the impression that I'd need to lasercut the grooves and rebates to get a great solid box sorted. I don't have access to a decent tablesaw etc..

So, I thought a tube would be the best way to get the 'cabinet' constructed more easily. However, you're right about the isolation of the tweeter and the driver.... so why don't I look at still having two tubes, mounting the tweeter inside the main driver tube?

That way I get around the issue of combining the two cylinders externally, have the isolation and don't have to build cabinets?!


Chris - pretty much bang on, thanks for the link!

Thoughts?

Cheers - Mike

#7 of 15 OFFLINE   SteveCallas

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Posted September 04 2005 - 01:51 AM

Ok, but if you are going to build a little half arch out of wood to sit the tube on, how hard would it be to build a couple 8 shapes out of MDF instead that could hold two tubes?

#8 of 15 OFFLINE   MikevZ

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Posted September 04 2005 - 04:38 PM

That's a good plan, let me work on it....

#9 of 15 OFFLINE   Ryan T

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Posted September 05 2005 - 03:31 PM

I have built tube speakers in the past using PVC. My brother in law also built tube speakers but using sono tube instead of PVC. In both cases I think it turned out really good. The construction isnt terribly difficult and there doesnt seem to be and mojor resonance issues. Plus you get one really unique looking speaker Posted Image. You can see mine here. http://www.rtcustomd...s.net/pcss.html .


Ryan

#10 of 15 OFFLINE   MikevZ

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Posted September 05 2005 - 04:24 PM

Ryan - wow - yeah, that's pretty much exactly what I had in my head!

Couple of questions:

- You didn't feel that damping (dacron / deadener) would help at all, within the PVC tubing?

- Where did you get the tweeter casing from - or were they purchased this way?

- WinISD is difficult for me, if I do the calc, would you mind assisting to confirm that I've got the numbers right? I intend on porting as I was decent bass response but don't want to build a sub.

Awesome, I'm glad someone's done this and I'm not nuts!

Cheers - Mike

#11 of 15 OFFLINE   Ryan T

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Posted September 05 2005 - 09:26 PM

I used a VERY small enclosure so I did go sealed. The PVC was "thin wall" which is about 1/8" thickness. They also sell it in 1/4" I beleive. I listened to them both with and without poly batting inside the enclosures. I decided I liked the sound a bit better with the batting. It also seemed to cut down on the resonances a bit. I had also thought about coating the inside of the PVC pipe with truck bed liner to further dampen in. But since my tube is so shallow it wanst needed.

The tweeters are HI-Vi brand TN28's. They are dirt cheap (~$13 per tweeter) and sound pretty incredible in my opinion. They dont have the lowest Fs but they still seemed to handle a fairly low crossover point of 2,300 Hz (though I wouldnt push it any lower without increasing the crossover order).

I would be more than happy to help you out with the calculations for your speakers. What drivers are you thinking of now? Also do you think you'll go with PVC or sonotube?


Ryan

#12 of 15 OFFLINE   MikevZ

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Posted September 08 2005 - 08:09 PM

Thanks Ryan,

An update - the drivers will have to be Vifa BC14 5" units - the reason that I'm doing this is that I got 'em cheap!

I have found some perfect tubes for the tweeters, which I've bought and are happy with. These are PVC, which will be fine for tweeters and have an inward curling lip, which means that I can mount a circle of MDF from the inside, cut a hole in it and mount the tweeters to they are perfectly flush mounted - they'll look hot.

Cannot for the life of me find the right diamter sonotube in my city. Found a 4m length some 700 miles away, the freight would have killed me!

At the very least, if I end up building boxes for cabinets, then I'm going to mount the tweeters in the tubes. But I havn't given up the hunt yet!

Also can't find specifications for the BC14's - anyone know a resource?

Costs so far (AU$ - multiply by .8 to get approx US$):

- Woofers - $60
- Tweeters - $50
- Cable - $2
- Tweeter Tubes - $0.50
- Getting brain working - $priceless

Thanks for input, really appreciate it!

Cheers -Mike

Edit - I'm happy to use either PVC or Sonotube, however the largest PVC I can find in local hardware store is 100mm (about 5inch), which isn't big enough...

#13 of 15 OFFLINE   SteveCallas

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Posted September 09 2005 - 01:38 AM

Look in your yellow pages under concrete. Call as many places as you can and aks if they carry it, if not, ask them if they know of a place who does. I found over 6 places within a relatively short distance of me that carried a large variety of sizes when I was looking to get some tube.

#14 of 15 OFFLINE   Ryan T

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Posted September 09 2005 - 05:52 AM

If you want larger diameter PVC check the local plumbing supply stores. They'll tell you the prices per foot of PVC. I got a 6" x 10' tube for around $15 US locally. For sono tube check any local hardware store chains. Around here we have Home Depots and Lowes that sell the tubes in sizes from 8" x 48" to 12" x 48" for around $8 US per tube.



Ryan

#15 of 15 OFFLINE   KeithMoechnig

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Posted September 09 2005 - 08:29 AM

Don't get the stuff at lowes or home depot. It's cheaply made.
Your best bet is to call around concrete stores. They will tell you where they get it. Your other alternative is to "pick up" some at a construction site.