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Old 18th June 2008, 08:12 PM   #1
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Location: blackburg va
Default first project, b20's

It took me long enough to finally get something. I would like you guys to know that your accomplishments allow me to start building with confidence. I went the cheap route with pioneer b20's with a goal of keeping the project at $100.

I am going to build some half chang enclosures and maybe crossover with a tweeter. I hooked them up to my main amp while in some cardboard boxes. I played some rap and some album leaf. To let you know album leaf is a band playing mainly instrumental ambient type music that could put anybody to sleep. They were played to get some comparisons to my radio shack mach 3 speakers. The first was to compare the bass with the 15 inch woofer and the other was to hear midrange and treble compared to the horns.

The mid's were slightly muffled and highs very light. When bracing the cardboard box the bass turned out to be impressive even though the box is about .8 cubic feet. The changs will take care of the bass and testing them with some really crappy free tweeters with a 1uF cap make me want to get helper tweeters. I'll wait to finalize that after i build the boxes.

In keeping cheap, i was going to buy 2 sheets of 3/4" mdf. Is there any decent plywood that you could recommend that would be enough and be around $50. What is a cheap tweeter i should get?

If anybody wants to make laying out their cuts on wood easier, you should look at this optimization program. download the free version. http://www.download.com/Sheet-Cuttin...dlPid=10285263
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Old 18th June 2008, 09:52 PM   #2
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Send me your address and I'll send you a pair of the tweeters
I was giving away for these at Burning Amp.
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Old 18th June 2008, 11:07 PM   #3
GM is offline GM  United States
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Default Re: first project, b20's

Quote:
Originally posted by krikus050

Is there any decent plywood that you could recommend that would be enough and be around $50.
None that I'm aware of, at least in the thickness required. If it's in the budget, seal the MDF inside and out with a decent sealer such as this to 'tighten' up its tone a bit: http://www.lowes.com/lowes/lkn?actio...801&lpage=none

GM
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Old 20th June 2008, 09:39 PM   #4
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If you like cheap and don't care about ugly, I've heard Oriented Strandboard (OSB) can be acoustically acceptable and the stuff is super cheap.

Haven't tried it myself, though.
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Old 21st June 2008, 10:23 PM   #5
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Default Re: Re: first project, b20's

Quote:
Originally posted by Nelson Pass
Send me your address and I'll send you a pair of the tweeters
I was giving away for these at Burning Amp.
I would love to send you my address but i am not able to since i have not made enough posts to email people. I am under moderation. Are these the tweeters you bought 200 of?

Quote:
Originally posted by GM


None that I'm aware of, at least in the thickness required. If it's in the budget, seal the MDF inside and out with a decent sealer such as this to 'tighten' up its tone a bit: http://www.lowes.com/lowes/lkn?actio...801&lpage=none
GM
I figured as much. I will probably go mdf then. I looked into much detail about staining it and some people say it looks decent with certain products. I will post my results and if it was easy or not.

Quote:
Originally posted by AdamThorne
If you like cheap and don't care about ugly, I've heard Oriented Strandboard (OSB) can be acoustically acceptable and the stuff is super cheap.

Haven't tried it myself, though.
I will look into this, thank you.

I figured if i buy 2 47"x97" sheets of mdf I will be able to make the half changs and the 3.0cu ft boxes. I will keep whichever i like best and give to other set to somebody.
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Old 22nd June 2008, 01:14 AM   #6
Nanook is offline Nanook  Canada
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Default MDF and all that.

kirkus050:

here's a rant against MDF: don't do it! Almost anything else is better. If you suspect you may try something better in the same cabinet spend some $$$ on Baltic Birch.

as impoverished as some of us may be, the results will be substantially better. OSB or even "chip board" has to better too: better dampening and less of the carcinogen formaldehyde !

in a pinch even use some sonotube (cardboard tube for cement forming columns and footings..)

As a minimum, maybe getting your local Home Depot or lumber yard to cut the MDF may be OK, as they cut it on a large panel saw, in well ventilated areas. If MDF, as suggested earlier, seal both the insides and out with a good primer , and paint . Some loudspeaker makers even take it further and suggest that if an enclosure is veneered on the outside it should be veneered on the inside and finished in exactly the same way.

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Old 22nd June 2008, 01:17 AM   #7
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Default stranded board...

stranded board might just be what the doctor ordered. dont be too afraid to try weird wood with these. they will sound good anyways.

You are in for a real treat. the b20 is a total overperformer.

I personally had the most luck sonically (and the best looks) with the driver back mounted against the paper gasket on the front of the frame. (screwed in from the inside of the cabinet).

it will require a removable rear panel, but that should not muck up the sound too much.

Nelson: got a link to what those free tweeters were?

I personally went on the super cheap and got the piezos with a .68 cap straight up. that was decent enough for my purposes.

enjoy,

Clark
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Old 22nd June 2008, 01:24 AM   #8
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Default Re: stranded board...

Quote:
Originally posted by krikus050
I would love to send you my address but i am not able to since i have not made enough posts to email people. I am under moderation. Are these the tweeters you bought 200 of?
ANYBODY can find me. Try the passlabs home page.

I bought 2000.



Quote:
Originally posted by blumenco
Nelson: got a link to what those free tweeters were?
Hi Clark, how many would you like? Do I have to send them all the
way to Japan?
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Old 22nd June 2008, 04:02 AM   #9
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Become the target of boys, run the risk that a doorbell ring might summon you to a flaming bag of doody on your doorstep.

...

Become the target of audio geeks, the bag is full of tweeters.


OTOH maybe it's your wife that is the target...

"But honey I HAVE to build it, I've got all these tweeters...!"
"... If I ever get my hands on the Pass guy..."

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Old 22nd June 2008, 01:21 PM   #10
mightym is offline mightym  United States
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B-20 cabinet design

Mr. Pass did a TL (?) design, however I can't find it on his site now....

I wondered how much material it took to produce? Maybe that it's not on his site, but here somewhere.

On the subject of OSB for speaker cabinets, don't let it get wet!, seal it well! Someone built a BIB with these Pioneer B-20"s and the little push in PE tweeter, and was very satisfied, except his distaff half wouldn't let them in the house.

The builders are now using an OSB product that is for subflooring, it looks to be about an Inch thick, and is rated for at least 16" span. This might be worth experimenting with. A builder told me he gets it for ~$25/sh.

John
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