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Author Topic: I'm about to dive in!  (Read 10525 times)

Chris Parsons

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I'm about to dive in!
« on: September 08, 2004, 10:17:11 pm »

I've decided to finally build two of these monsters.  They will go under my JBL 4732's.  

I have a series of questions that may have allready been asked but i'd like to know what everyone thinks TODAY Smile


Is there any reason(s) to NOT build version 3.0?  

I live in Santa Cruz, CA.  Any suggestions from you bay area people as to where I can get 3/4" baltic birch?

What's the best glue (bang for the buck) and where do I get it?

How much wood should I buy?  What thinkness?  

What size Tee-Nuts and screws for the drivers?


Thanks for your time!

-Chris Parsons







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Al Limberg

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Re: I'm about to dive in!
« Reply #1 on: September 08, 2004, 11:02:13 pm »

Hi Chris,
Welcome to the sawdust club!  I'll try to answer your questions where I feel qualified and try not to BS you in areas where I'm not.

In order of appearance:

#1  Brad does absolutely gorgeous woodworking and its obvious from the pics he has posted.  I'm fast approaching 16 units completed - the first 8 from Tom Danley's original plans (call it version 1) and the second batch of 8 from the updated drawings (was that Peter?).  I have not attempted version 3 and probably won't simply because compound mitre joints are tougher than Chinese arithmetic to me and his plans call for at least 4 (or maybe 6) instead of the 2 per version 1 and 2 specs.  I also went back and dug out the measurements Too Tall has done on my subs with Praxis and found no real sign of the 'dip' at 50hz that Brad's prediction software expected.  Since extended high end response isn't necessary for my purposes (80Hz is fine for either my indoor or outdoor system low mids), I think it makes more sense for me to go with what I know.
#2  Not being from the bay area, I'd simply suggest getting on the horn and using your yellow pages and shop shop shop for your birch.  Make sure you ask for discounts on quantity.
#3  For general purpose gluing, I recommend Franklin Tite-Bond Professional Carpenter's Glue.  It's basically a pale yellow waterrproof variant of good ol' Elmer's!!  You should be able to find it at any lumber retailer (Lowe's, Home Depot, etc. for about $13-15 a gallon - yes  - buy the gallon!)  For critical joints (such as the module and those joints between the module and the box, I highly recommend West System epoxy products.  Too Tall will argue with me but I prefer the 'filetting' powder to mix with the 2 part epoxy to thicken it and let it act as a filler as well.
#4  You'd think a guy who had finshed 12 and had 4 in the oven would be able to quote you exactly how much wood you need, wouldn't you??  I've had the benefit of having a storage facility stocked with a bunch of 4x4 'mill-end' sheets of birch so my experience doesn't mesh well with the use of 5x5 sheets altho my supplier now has birch in 4x8 so life is better for me.  If its of any help, I manage to get 8 modules and all the internal braces out of 10 5x5 sheets in my last batch.  Using the 4 x 4 sheets for just the external box, 7 were required(per pair).  I guess that would translate down to 4 4x8 sheets and 3 5x5 sheets with enough leftover to let you make a mistake or two without feeling like suicide was necessary (again - per a pair).  I should add that frankly, I have taken a few small liberties with the original plans.  As regards the end product I believe they make absolutely no difference, but they do keep my wood consumption down a little.  Where i have cheated is on the internal braces that connect the modules to the side walls.  The rear brace and the 'foot' brace have been downsized slightly (very slightly on the foot brace) - just enought to keep me from using an additional sheet of plywood with about 90% scrap remaining!

Oops  Guess I already answered #4!

#5  I used 10-24 T-nuts to mount the speakers and the handles and jack plates and 1/4-20 for the aluminum lids and the rubber feet that I use.  Obviously 10-32 would work as well as the 10-24 - it just came down to what was readily available to me.  You might look for a distributor in your area - I have found the one locally that serves the hardwares here and they aren't shy at all about selling them to me  (and the screws as well) at about half of the hardware price in 100 piece boxes.  (That's one half of the hardware price when I buy them by the hundred there).

#6  Spend a little time making up a plan - what to do in what order.  I assure you, gluing the baffle boards before installing the T-nuts could be a real bummer!  If you end up building version 1 or 2, sit down and make the adjustments to the baffle board dimensions so you can dado them in to the sidewalls of the modules - life is immensely easier if you do - do the same for the braces between the module and the side walls and dado the side walls.

Best of luck  and have at it!! It's worth it.


Al
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Chris Parsons

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Re: I'm about to dive in!
« Reply #2 on: September 09, 2004, 06:48:35 pm »

Thanks for the lenghty reply Al  Very Happy  

Okay, I found what seems to be a great supplier of birch plywood.  Luckly it's 5 min. away from my home!

Here are the options:

5'x5' Baltic Birch 18mm , for $39.55
4'x8' Shop Birch (from china)18mm, $34.99 (on sale from $50)!!!

I know that Baltic Birch is reccomended but the shop Birch, which looks/feels damn close to the baltic, is going for such a great price.  

-----------------------

Do I only need 18mm plywood?

-----------------------

I'm still lost as to what verson to build.  If ver. 3 takes a wood-working pro then it might not be my gig.  But on the other hand, I want these to sound as great as possable.  What are some things to consider?

-----------------------  


Thanks again for your time

-Chris Parsons
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Al Limberg

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Re: I'm about to dive in!
« Reply #3 on: September 09, 2004, 07:30:46 pm »

Sounds like decent prices on the birch for you Chris. The 5x5 price is about $8 more per sheet than I paid last time but my last purchase was a 33 sheet buy and that was last winter and I know prices have gone up.  I'm not familiar with the chinese but I wouldn't be surprised it that is what all my 4x4 sheets are in reality - they have been really good - not quite on the same quality level as the real stuff but it has been fine to work with and has held up fine, whatever it is!  As far as the version 3, Brad's main claims (and I have no reason to doubt him) are extended high end that he needed for his home theatre rig, and smoother in the 50Hz range (which hasn't been an issue with mine).

Maybe Brad will chime in and give us his feelings on degree of difficulty,etc.

Al
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Chris Parsons

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Re: I'm about to dive in!
« Reply #4 on: September 10, 2004, 02:41:55 am »

I'll probablly be crossing these at 120Hz.  

I'm thinking to by just enough baltic birch for the modules and then use the shop birch for everything else.  
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Jeff Woodford

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Re: I'm about to dive in!
« Reply #5 on: September 10, 2004, 07:34:19 am »

i got 2 labs out of 6 sheets of 8x4 marine ply with some to spare.
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Jeff Woodford
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Too Tall (Curtis H. List)

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Re: I'm about to dive in!
« Reply #6 on: September 10, 2004, 11:12:36 am »

Chris Parsons wrote on Wed, 08 September 2004 22:17

I've decided to finally build two of these monsters.  They will go under my JBL 4732's.  

I have a series of questions that may have allready been asked but i'd like to know what everyone thinks TODAY Smile


Is there any reason(s) to NOT build version 3.0?  




Al is a really good test case for building these because he had almost no experience in wood working before about 4 or 5 years ago. His advantages have been that he uses my wood shop, which includes significant professional tools (large 5HP tablesaw with T-Square fence system, Biscuit cutter, air nailers, Bosch plunge router, etc).

His other advantage is if he REALLY gets stuck I help him figure it out. Even then he would figure it out eventually, but it gives me an excuse to hang out. Wink

In any case over all he his done this project by himself and made and fixed all his own mistakes. So to make a long story longer when he says version 3 is more difficult, I would add that for someone without extensive woodworking experience of this kind it is a poor risk.


   For performance if the graphs are correct the version 3 is a little flatter over all before any EQ. My apologies to Al, but some of the measurements I have of LAB sub version 1 do indeed show a dip around 40 or 50Hz followed by a peak around 30Hz. To my mind not enough to make the version 3 design worth doing. A little EQ and I have the same response. In addition once EQ'd to give the same response as version 3 I believe version 1 will produce the same level output.

Version 3's true advantage is response above 80Hz. There version 1 is a dog.



Chris Parsons wrote on Wed, 08 September 2004 22:17


I live in Santa Cruz, CA.  Any suggestions from you bay area people as to where I can get 3/4" baltic birch?




You said something about a shop grade Birch. My only concern would be that it has the same number of plys and that the inner plys were also solid Birch. Please keep in mind the odds are high that both of these use "interior grade" glue which means water will delaminate the plys. Check if they are interior or exterior glue. If they use interior glue make sure the entire exterior is heavily sealed and pay attention to any end grain showing. Al uses West System Epoxy to apply woven fiberglass to the outside edges which gives them strength, wear and a total seal if you didn't quite get a joint to close. Also as long as you don't splash water into the horn mouth it will make a dandy boat.








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Too Tall
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Brad Litz

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Re: I'm about to dive in!
« Reply #7 on: September 11, 2004, 12:30:25 am »

Al Limberg wrote on Thu, 09 September 2004 18:30


Maybe Brad will chime in and give us his feelings on degree of difficulty,etc.

Al


The v3.0 cabinets do have compound cuts set into dado grooves in the driver module. If you cut these wrong you will have big trouble. If you cut them accurately, they go together very easily. To help avoid mistakes, I now have drawings of the compound cut pieces posted on my web page in addition to the CAD models and viewer links:

http://www.geocities.com/hulkss/index/

I do appreciate the compliments I have received about my cabinent consruction. Just cut the pieces accurately and you will have good success. The only significant wood working I have done is my two LABsub cabinets and two Klipschorn cabinets that I built in the 70's. I bought a table saw just for the LABsub construction, maybe I'll use it again some day. I benefited greatly from all the great tips posted on this forum by those who tackled this project before I did.
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Brad Litz

Chris Parsons

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Re: I'm about to dive in!
« Reply #8 on: September 14, 2004, 01:18:49 pm »

I've desided to go with Peter Sylvester's LAB plans.  I like how detailed the documentation is.  Brad's plans are a bit over my head Smile

Will I run into problems useing these plans with 18mm ply?  


Thanks,

-Chris Parsons
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Chris Parsons

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Re: I'm about to dive in!
« Reply #9 on: September 14, 2004, 01:22:55 pm »

Okay, my brain just started working today and I noticed the "18mm Panel Layouts" link on Peter's site...
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