Help with OB/Ported 2-way (1st DIY)

[krips]

Hey guys. The drivers I'm going to be using are the CCS FR125 and CCS SDX7. I was planning on going OB with the FR125 and having the SDX7 tuned to 35hz in .6cf. WinISD tells me that with a 2" port it would have a first port resonance of 675hz, and hit its xmax at 29hz. Here's a pic of what I was thinking of (please excuse my primitive sketchup abilities ops: ).
The Cabinets
The Edge Response
It looks to me like it should be crossed at about 500hz, but I'm just guessing here. What do you guy think? Also, are there any serious (or even minor) flaws in my design as you can see it? Have I given enough information? Any help would be appreciated.

[krips]

Anyone?

[Undefinition]

It looks to me like it should be crossed at about 500hz, but I'm just guessing here. What do you guy think? Also, are there any serious (or even minor) flaws in my design as you can see it? Have I given enough information? Any help would be appreciated.

Well, I have to ask: is this your first dipole/OB design? Is this your first speaker design?

In a sense, this project seems very doable. You have a full-range driver handling the OB duties, so technically you're only doing a 2-way. Plus, you're doing vented bass... so at least you don't have to wrestle with the headaches of dipole bass.

On the other hand, your OB section has a very small baffle, so you are going to experience rear-wave cancellation at a pretty high frequency. Off the top of my head, I have no idea what htat frequency would be, but it can be simmed fairly easily using the FRD tools or (my personal preference) Jeff Bagby's Response Modeler. So that would be the first thing you'd want to look into, in order to find a sensible XO frequency.

Personally, I like to give OB drivers as much room to work with as possible, so I try to cross at 250 Hz or lower (honestly, once you get above there you are in midrange territory, which sort of buzzkills the whole "OB experience," in my opinion). In order to lower the cancellation frequency, I like to use a small U-frame on my dipole designs (this, in a sense, causes the baffle width for the rear waves to increase by 8" or so).

Here are the two OB projects I've done.
http://undefinition.googlepages.com/diy-aethers (this explains a lot of the theory which might help you in your endeavor)
http://undefinition.googlepages.com/diy-sunflowers (a more sophisticated version of the first speaker)

My "dipole theories" are based on my own personal experimentation, some of the writing of John Kreskovsky and Siegfried Linkwitz, trusting my ears, and the guidance of this guy:

http://members.optusnet.com.au/~gradds55/ARGOS/blackwood.html

[krips]

Thankyou for your response. This is my first crack at my own speaker design, and my second attempt at a speaker build. I will read the links you've provided me later tonight when I get home .

[ThomasW]

Krips,

You may want to use our search engine for dipole designs. I think you'll find a wealth of information

[Dennis H]

On the other hand, your OB section has a very small baffle, so you are going to experience rear-wave cancellation at a pretty high frequency. Off the top of my head, I have no idea what htat frequency would be, but it can be simmed fairly easily using the FRD tools or (my personal preference) Jeff Bagby's Response Modeler. So that would be the first thing you'd want to look into, in order to find a sensible XO frequency.

Paul, his sim in The Edge shows the dipole peak and where it rolls off. It's a slick little program for flat baffles although it doesn't do U or H frames.

Edit: oops, no it doesn't. Krips, you need to check the open baffle box.

[krips]

Ah, how embarrassing. I usually do that. Apparently I was to hasty in my excitement to get my post all ready :P . It look to me to be basically the same though once OB is checked. The peak's a little higher and the drop-off a little steeper. I'll try and do some searching for OB designs.
Can anyone point me to a program that will show me (or even guestimate) the effects of adding 'wings' or sides to the baffles?

[Undefinition]

Ah, how embarrassing. I usually do that. Apparently I was to hasty in my excitement to get my post all ready :P . It look to me to be basically the same though once OB is checked. The peak's a little higher and the drop-off a little steeper. I'll try and do some searching for OB designs.
Can anyone point me to a program that will show me (or even guestimate) the effects of adding 'wings' or sides to the baffles?

I don't know about a program that does it. But I just used a normal dipole simulation for the Aethers. I took note of where the dipole roll off was happening, then crossed above that... not all that complicated, I guess :roll:

Anyway, you're going to want a baffle of around 10-11" would be my guess. With 4" wings on the sides, that makes the "rear baffle" about 16" or so. That should push the dipole roll off down to a reasonable level... oh, but don't forget to put a wing on the top too, or you'll have a double-roll off (yes, I did it on the Aethers, and I would never do it again, nor recommend it to anyone)

[krips]

Well, that should work fine then with the design I posted originally, as it sported a 10.5" wide baffle. Essentially, what you're saying is that I should build my 'box' approximately 4" deep and have it open-backed?