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Old 9th May 2010, 10:45 PM   #1
djn is offline djn  United States
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Default Need help with OB design - cheap, cheap, cheap

Hi All, I never had much interest in OB speakers, but to be fair, I never really listened to them. Well, this past weekend was the AK fest and I sat and listened to the Salk Audio OBs for a couple hours. Now I want to build a pair with stuff I have laying about. So, what are the critical specs I need to look for in the drivers? I have a lot of drivers and would rather go about this with some clarity of thought vs. just trying everything I have to see what works.

Here is what I have so far.

TWEETER:

The old but wonderful Philips tweeter. The back is enclosed so not really OB. Here is 1. the spec sheet and 2. a crossover designed for them.

http://www.troelsgravesen.dk/WWDT_files/ad0160.pdf

WWDT (at the bottom of the page)


MIDS:

The Parts Express PA130 5" midrange driver.... here is the spec sheet

http://www.parts-express.com/pdf/295-010s.pdf


WOOFERS:

And this might work for the woof - I have 4 of them. - CERWIN VEGA S-10.8 10" 8 OHM 400W STEALTH WOOFER

This is all I could find on them

• Woofer Size: 10".
• Frequency Response: 40Hz -500Hz.
• Power Handling: 200 watts RMS (400 watts Maximum).
• Sensitivity (2.83V @ 1 meter): 93dB.
• Impedance: 8 ohm.
• Mounting Diameter: 9.0" (22.86 cm.).

I posted this in the Fun OB thread but then realized that I was highjacking the thread and so I am starting this thread.

Panomaniac posted a number of posts about the RROW and that makes a lot of sense. But, I don't know enough about crossover design to figure a crossover out.

P.S., this is all stuff I have laying around for years if you are wondering why I would chose these componants.

Cheers.
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Old 9th May 2010, 11:31 PM   #2
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You might look at Martin King's OB projects they cover a little of the theory
behind a good OB. One of the things to look for in a woffer is a high QTS this is
one of the things Martin discusses in his article. Both Martin King and Nelson Pass
both like the Emminence Alpha 15A for use on an open baffel and it's cheap!
I built Martin's 2 way OB and am verry verry pleased with the results.
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Old 9th May 2010, 11:58 PM   #3
djn is offline djn  United States
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Thanks for the link Woody. Looks like I have some reading to do. The other option I have is using two subs that can go up to 150hz and mounting the Mids and tweets OB on top of them. Has that been done before?
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Old 10th May 2010, 12:49 AM   #4
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I would not use 10" woofers on OB. You just won't "get no satisfaction." 2 per side, maybe - just.

How big a baffle can you stand? That's going to determine a lot. It's hard to make a good, small OB.
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Old 10th May 2010, 01:47 AM   #5
djn is offline djn  United States
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I have not worked much in the last year so I really have to work with what I got. These will be for a small listening space so I don't have room for large baffles. I do however have a number of subs around the house to augment the bass.
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Old 10th May 2010, 02:28 AM   #6
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If you're resigned to using what you have on hand, then I say "go for it" using what you have on hand. I would be sure open baffle is what you want if you really don't have a lot of room for these. They really need ~3 to 4 feet behind them to work well and give that wonderful open sound.

I agree with Panomaniac's advice to read up on what Martin King has posted on his website. That's how I came up with my 2-way open baffles. I would also take some time to read through Panomaniac's OB thread as well. You may not be using the same components, but getting different ideas/perspectives/opinions is not a waste of time- IMHO.

Since you're looking at using 10" woofers, I would definitely recommend spending time on the MJK papers regarding H-Frames. 10" woofers are what come with the Linkwitz ORION speaker, so it can definitely work if implemented right. If you can afford the fee for Martin's worksheets, I think that would be a better investment than buying different drivers.

If you can't afford MJK's sheets/fees then spend as much time as you can researching different ideas/implementations as possible and build what you want with what you've got. Start with cheap scrap wood and once you've got something you're happy with, then worry about a "finished" product.

A really long reply, but you shouldn't feel discouraged by not having exactly the same things as everyone else has. Work with what you've got if that's what you want.

Good luck!
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Old 10th May 2010, 02:34 AM   #7
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depends on the Q of the CV woofers - if Hi Q, they'll probably be OK, if Low Q, then you may have to equalise the bass end considerably. It's pretty easy to try if you've got a spare sheet of ply or chipboard lying around...
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Old 10th May 2010, 02:44 AM   #8
djn is offline djn  United States
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Yep, wood is something I do not lack around here. I will start reading tomorrow. I printed out MLKs articles on OB design and H and U frames. I most likely have all the crossover components needed as well. Should be fun. P.S., I do have three feet behind the OBs. I don't know if this will hurt the sound, but they will be in front of a wall of plate glass windows....floor to ceiling, wall to wall. Cheers.
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Old 10th May 2010, 02:50 AM   #9
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Quote:
Originally Posted by djn View Post
Yep, wood is something I do not lack around here. I will start reading tomorrow. I printed out MLKs articles on OB design and H and U frames. I most likely have all the crossover components needed as well. Should be fun. P.S., I do have three feet behind the OBs. I don't know if this will hurt the sound, but they will be in front of a wall of plate glass windows....floor to ceiling, wall to wall. Cheers.
Use heavy drapes then
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Old 10th May 2010, 02:54 AM   #10
djn is offline djn  United States
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Quote:
Originally Posted by Moondog55 View Post
Use heavy drapes then
When work picks up, that is on the list.

Also, I just remembered that I have WT3 Woofer Tester and I will test them the CVs tomorrow. Good night all. Cheers.
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