Now what.....

[503Timber]

Under some weird circumstances I acquired some drivers (essentially free)and want to get a project laid out and I'm not really sure how to go about it. The drivers are the following....

2- Eminence Alpha-15A 15" Driver 290-407

2- Dayton PS180-8 6-1/2" Point Source Full-Range Neo Driver 295-344

To date I have been a "change caps, clean pots" kind of DIY'r so this is new territory. I want the sub in a simple H frame and the fullrange to be OB on the top. I want the overall H frame size to be about 20"X20". The top section will be about 12" wide with 6" "wings" that will be hinged so I can adjust them on the fly. That's as certain as this project gets.....and I'm not too certain on that. I will be going as simple as possible on the xover and I'm thinking around 400hz.......? 3.3mH inductor on the woofer and a 50uF cap on the fullrange......am I on the right track?

I've looked over some of the material out there for OB and it just makes my head spin!

[Jim Griffin]

The best resource for your design is likely Martin J. King's website. He has examples of similar designs , a gallery of designs by others, and such. If you pay $25 you get access to his MathCad (you can use a MathCad Explorer version for free) spread sheet to model an open baffle speaker like yours in your own space.

I recently completed a similar design to yours with the Eminence Kappalite 3015LF Neo woofer and the Mark Audio Alpair 10.2 full ranger. As my woofer is a low Q unit, I used an active digital crossover primarily to equalize the design. The sound is excellent!

Openminded--A Mark Audio Alpair 10.2 Open Baffle Project

Quarter Wavelength Loudspeaker Design

Jim

[chris661]

One per side on a nice big open baffle, say 20" wide and as tall as you need for the FR driver to be at ear height. Centre the bass driver and offset the FR driver a little, so the baffle edge diffraction isn't so messy.
Add a simple crossover and you're good to go.

Chris

[503Timber]

A simple OB would be much easier for me......maybe I'll start there. The local hardware store sells 2'X4' sheets cheap.....two of those, some "L" brackets for feet and I'm done. In thinking about it further I may just want to run the Dayton wide open with no xover......? I'm shooting for a "minimalistic system" The fewer parts the better, so if both can just run with no xover that's even better.

[Jim Griffin]

Martin King has a study on his site that compares and open baffle, U-frame, and H-frame configurations. The U and H frames have extended lower frequency range cutoff points vs. the open baffle version. The H-frame can go the lowest of all in Martin's study. You would have to increase the width of the open baffle to equal the bass cutoff frequency of the other two configurations. Furthermore, by the time you add side supports to the open baffle you will have about as much complexity as the other two configurations.

[PeteMcK]

https://docs.google.com/viewer?a=v&p...3Mzdj&hl=en_US

[503Timber]

That's a good point Jim......I'll have to get into Martin's site again and see if I can make sense of it. I sure do like the H frame look better.

[Godzilla]

I did this with the Alpha 15 in H-frames and a TB 1808 full range driver. You could do the same or similar with the Dayton. I added a super tweeter but it's not needed.

http://www.hifisentralen.no/forum/in...h=235540;image

It was fun to find my project on what looks like a German site.

[503Timber]

Well I was able to round up two nice pieces of 2'X4' cabinet grade plywood from my apartments maintenance guy..... he even cut the holes for me. (Bonus of having your mom be the manager!) Holy cow is the Dayton overpowering the woofer. The woofer desperately needs to be xover too.....there is an unbelievable "shouty peak" around 2k. I'll have to sort all that out before I get to my final layout......but this will be a good way to break in the drivers I suppose.

[chris661]

Originally Posted by Jim Griffin

Martin King has a study on his site that compares and open baffle, U-frame, and H-frame configurations. The U and H frames have extended lower frequency range cutoff points vs. the open baffle version. The H-frame can go the lowest of all in Martin's study. You would have to increase the width of the open baffle to equal the bass cutoff frequency of the other two configurations. Furthermore, by the time you add side supports to the open baffle you will have about as much complexity as the other two configurations.

I suspect the extended LF response was due to the longer path length.


I'd take a first order series crossover - some reading here Note that varying woofer impedance isn't a problem for this crossover type, the crossover point adjusts for both to maintain a flat transfer function. Neat.

Chris