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In need of advice for my Fostex FE126 bass reflex build

post #1 of 17
2/18/11 at 10:03pm
Thread Starter 

I have found a decent deal on a pair of drivers and am in the middle of getting a quote for materials (since I lack tools). Now I need advice on the cabinet!

 

I found this on diyAudio and I thought it seems like a good idea since it is simple and the measurements are in inches. The lumber place I am dealing with doesn't have boards in metric measurements.

This guy used pine, I like the look of it but I'd like to see it stained to a different color. Is pine a good material for this sort of build? Also are there any guides on how to finish cabinets, as in stain and make them look nice?

newspeakers004.jpg

 

Do you think they'd provide sufficient bass? I am in a small room and they will most likely be sitting on impromptu stands. 

 

One last thing, the Fostex designs call for a 105mm (diameter) hole for the driver. That converts to 4.13 inches. Should a 4 inch circle be good enough?

 

Thanks.

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post #2 of 17
2/22/11 at 6:54am
Thread Starter 

Bump.

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post #3 of 17
2/22/11 at 7:24pm

Pine isn't known to be a good speaker cabinet material.  Most DIYers use MDF, but the preferred material is baltic birch.  Pine is the toughest wood to finish.  Stain will blotch unless you use a pre-conditioner and it may blotch even with a pre-conditioner.  And, no, you won't get much bass out of a 4" driver in a bass reflex cabinet.  A back-loaded horn (buschorn) would give more low-end excursion.  You'll need a subwoofer if you want bass.  The only way to determine if a 4" circle will be good enough is to measure the drivers.  But, you can use a plunge router and a jig to make a circle of any size.

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post #4 of 17
2/22/11 at 8:02pm

At least 3/4" thick MDF. It is also important that they are braced well inside to minimize enclosure resonance. You want that resonance to be very low in frequency. Like HW said a 4" driver will not get you much bass. Bass is about moving air, a lot of air.

 

You also need to put some dampening material inside and a low audio frequency filter.

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post #5 of 17
2/22/11 at 8:10pm
Thread Starter 

I decided against the above design. I am going to be building something along the lines of the Fostex BR cabinet. 11.5 inches tall, 11.5 inches deep, 7 inches wide. All of this in 1/2 inch think baltic birch. I am in a small room so I just need a touch of bass, maybe it will be sufficient, maybe not. 

Worst case scenario I will sell these can build a two way system. How does one stain baltic birch plywood?

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post #6 of 17
2/24/11 at 1:54pm
Thread Starter 

Is $48 too much for an 8 foot by 4 foot sheet of 1/2 inch think baltic birch plywoord, plus cuts and glue?

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post #7 of 17
2/27/11 at 11:23am

Not at all - I paid $19 for a 2'x2' piece at Rockler on sale. Just make sure your sheet has minimal curves and twists. I recommend Titebond III glue. You will also need some foam or wool insulating material.

 

The 4" hole will be sufficient, but you might have to notch just a bit where the driver frames meet the hole.

 

In looking through all the DiyAudio designs, I am taken by the various Fonkens, though I used a Martello for my 3" drivers, documented here.

 

You can stain Baltic birch with any stain, preferrably a wipe on, and make it one step with stained wipe on poly - probably 2-3 coats.

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post #8 of 17
2/27/11 at 4:24pm
Thread Starter 

They are doing the cuts for free. They generally don't do the cuts in house since it is a large establishment (84 Lumber) but he said he will find someone with the tools to do it and I can come in an make sure they do the cuts correctly. 

I was under the impression you didn't have to flush mount the driver. Anyway, talk more about the stain, I didn't understand that last bit. 

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post #9 of 17
2/27/11 at 6:28pm

Well, you are getting a good deal, if the cuts are included, as Lowes/Home Depot usually only include 1 or 2 cuts free.

 

The stain can be done as part of the final finish, where the wipe on poly(urethane) can have the color in it. Just wipe (or brush) it on, and let it dry. If you use multiple coats, you may have runs, which you would sand down, then apply the final coat. There is also Watco / Formby/tung/linseed, and boundless other oil based options. Spray lacquer is also an option.  

 

You will want to practice on some scrap of your same material.

 

But, let's not worry about the finish until you have the glue up and sanding done. I usually use 80/120 on the belt sander, then 100-150-220-320 on the palm sander, OOOO steel wool by hand, followed up with a tack rag.

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post #10 of 17
2/27/11 at 6:45pm
Thread Starter 

Thank you very much. I may have these done by the weekend. What to do with the other 20+ square feet of material?

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post #11 of 17
2/27/11 at 7:31pm

Fonken Primes?   :-)

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post #12 of 17
2/27/11 at 7:42pm
Thread Starter 

Well, better yet, a different speaker design. Needles? That's for later though.

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post #13 of 17
2/28/11 at 9:39pm
Thread Starter 

I got the drivers today. I couldn't help it. They are in shoeboxes right now with PVC pipe bass ports. Pictures tomorrow. They sound great!

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post #14 of 17
3/4/11 at 5:16pm
Quote:
Originally Posted by mralexosborn View Post

I got the drivers today. I couldn't help it. They are in shoeboxes right now with PVC pipe bass ports. Pictures tomorrow. They sound great!


lmao

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post #15 of 17
3/30/11 at 4:14pm
Thread Starter 

There are all done now. XD

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