Orion open baffle/dipole questions

[ocdSCHACK]

Here's the deal,
I have decided to build a pair of Orions clones. I would prefer to build clones to save money on the tweeter and mids, but at my current purchasing rate I may just build the real things. I couldn't resist and bought another pair of the 8ohm 10" Peerless XXLS while the price was good.
Here are my question(s):
Does anyone have the dimensions for the H-frame baffle used for the orions? I know it is approximately an 11.5" square for each woofer, but what is the depth and how are centers lined up (viewing from the side)?

Just a warning, the question of my next post will be something like this:
Any recommendations for the highs and mids? I'll be getting two or four 8" woofers for mids and two or (probably four) tweeters.

[djg]

Re: Orion open baffle/dipole questions

You are aware the Orion has a custom electronic active crossover? It is a system, not just a speaker.

[evilskillit]

Re: Orion open baffle/dipole questions

Yeah, it would be more accurate to say "I want to build a speaker that looks like an orion" :D In which case just design a 3 way dipole or see if you can take someone else's that already exists and make the cabinetry look like the orion.

[johnk...]

Re: Orion open baffle/dipole questions

Here's the deal,
I have decided to build a pair of Orions clones. I would prefer to build clones to save money on the tweeter and mids, but at my current purchasing rate I may just build the real things. I couldn't resist and bought another pair of the 8ohm 10" Peerless XXLS while the price was good.
Here are my question(s):
Does anyone have the dimensions for the H-frame baffle used for the orions? I know it is approximately an 11.5" square for each woofer, but what is the depth and how are centers lined up (viewing from the side)?

Just a warning, the question of my next post will be something like this:
Any recommendations for the highs and mids? I'll be getting two or four 8" woofers for mids and two or (probably four) tweeters.

If you want to build a speaker "like" the Orion, a good place to start would be with ABC Dipole.

[ocdSCHACK]

Re: Orion open baffle/dipole questions

I'll try again; "I want to build a speaker that looks like an orion." I am going to use the Behringer 2496 active crossover, but haven't yet decided on the Mids and Highs. I'm ready to start building as soon as I get the woofer enclosure dimentions...
I have 4 XXLS 10" woofers and was wondering if anyone has the dimensions of the H-frame baffle for the woofers that is used with the Orion? Or any other proven design?

If you want to build a speaker "like" the Orion, a good place to start would be with ABC Dipole.

I looked through that site before, but didn't find what I needed. If I were starting from scratch It might help, but I'm looking for a proven design since I'm using such common woofers for this type of "enclosure."
I've also looked at the Orion site, but the formulas in one section are incomplete, and then he uses the same variables to describe something else in another section. It's way too unorganized, and the info would be hard enough even if it was in order.

I'm just hoping for a simple proven h-frame for the peerless xxls or xls woofers.

[djg]

Re: Orion open baffle/dipole questions

Have you looked at Paul Carmody's two open baffle designs?

http://undefinition.googlepages.com/diy

[johnk...]

Re: Orion open baffle/dipole questions

I'll try again; "I want to build a speaker that looks like an orion." I am going to use the Behringer 2496 active crossover, but haven't yet decided on the Mids and Highs. I'm ready to start building as soon as I get the woofer enclosure dimentions...
I have 4 XXLS 10" woofers and was wondering if anyone has the dimensions of the H-frame baffle for the woofers that is used with the Orion? Or any other proven design?


I looked through that site before, but didn't find what I needed. If I were starting from scratch It might help, but I'm looking for a proven design since I'm using such common woofers for this type of "enclosure."
I've also looked at the Orion site, but the formulas in one section are incomplete, and then he uses the same variables to describe something else in another section. It's way too unorganized, and the info would be hard enough even if it was in order.

I'm just hoping for a simple proven h-frame for the peerless xxls or xls woofers.

After a flat baffle the H frame is about the simplest form of dipole woofer. If you can mount the drivers on the baffle then the length of the H isn't particularly critical once a reasonable depth (from the point of sensitivity) is established. For example the major effect of a 20% change in length will a change in sensitivity of 1.5 dB, (increasing for the longer H) and a shift in the dipole peak by 20% (lower for the longer H).

If you accept that the dipole peak should be at least an octave above the woofer LP crossover and not more that 2 octaves above, then that will give you upper and lower limits for the length. Note that this length variation yields a 6dB difference in sensitivity. What length you choose at that point is more a trade off between cosmetics (size) and sensitivity. Equalization, on the other hand, will be dependent on the driver TS parameters and what the target response is for the woofer system. Dropping an XXLS woofer in a system designed for an XLS will give different bass response. You can correct for that with your DCX.

[ocdSCHACK]

Re: Orion open baffle/dipole questions

John K...
thanks for your help, but I do have a few questions:

For example the major effect of a 20% change in length will a change in sensitivity of 1.5 dB, (increasing for the longer H) and a shift in the dipole peak by 20% (lower for the longer H).

First, in simpler terms, I read this from your statement: A longer baffle=more sensitive=lower dipole peak. Did I read that correctly?

Next, when you say a longer "H," are you referring to the center baffle being in the center of the total length? (i.e. a 2" longer baffle makes the baffle longer by 1" on each side)

Here's my confusion: Linkwitz has the formula for the resonance i a symmetrically divided frame as:

The speed of sound / (4 x (.5 x the total length))

I put it in simpler English than him, and I assume 4 is used because it's the reciprocal of 1/4, as in 1/4 of a wavelength. But where does baffle size come in to play? I don't see any mention of the size, only the length. Should I assume a perfect cube?

Thanks ahead of time.

[johnk...]

Re: Orion open baffle/dipole questions

John K...
thanks for your help, but I do have a few questions:



First, in simpler terms, I read this from your statement: A longer baffle=more sensitive=lower dipole peak. Did I read that correctly?

No. Not longer baffle, longer H frame front to back, with baffle centered.

Next, when you say a longer "H," are you referring to the center baffle being in the center of the total length? (i.e. a 2" longer baffle makes the baffle longer by 1" on each side)

Again, length referres to over all length of the H frame, not the baffle size. The baffle is the flat piece in the center of the H where the drivers are mounted. Ok?

Here's my confusion: Linkwitz has the formula for the resonance i a symmetrically divided frame as:

The speed of sound / (4 x (.5 x the total length))

I put it in simpler English than him, and I assume 4 is used because it's the reciprocal of 1/4, as in 1/4 of a wavelength. But where does baffle size come in to play? I don't see any mention of the size, only the length. Should I assume a perfect cube?

Thanks ahead of time.

Linkwitz over simplifies.

First; the dipole peak is at C/(2 x Total length). That generally holds.

Second; the H frame resonance is a 1/4 wave resonance based on the the length of the duct from terminus to baffle. So this becomes:

Res F = C/(4 x Total Length/2) which comes out to be the same frequency as the dipole peak. That only hold true if the effective diameter of the duct is much less than the length. This would occur if the H frame were long and the baffle was small. like to mount a small diameter driver. Typically the opening, even for a single driver, has an effective diameter on the order of, or larger than L/2. The effect of this is to make the resonance lower in frequency and with lower Q. The figure below gives an indication of how the resonance behaves at the opening area goes from very small diameter to 4 time the 1/2 length of the H.



Thus an H frame of length L will have a resoannce who's frequency and Q will depend on the baffle size. Assuming the H opening are the same dimensions as the dividing baffle, bigger baffles yields lower frequency resonances with lower Q. You can see that as the center baffle becomes very large compared to L this tends to a flat baffle result and there is no resonance.

[ocdSCHACK]

Re: Orion open baffle/dipole questions

Sorry, I was thinking length even though I kept writing "baffle." I agree:

The baffle is the flat piece in the center of the H where the drivers are mounted.

I'll try to simplify what your saying to make sure I'm understanding correctly. In my example, the closed H frame is a square baffle with 4 panels that surround the baffle. We'll say the baffle is a 12" square made of 3/4" wood and each panel 12.75" long, for a total length of 12.75" and L/2(adjusted for baffle thickness) is 6" long for each the front and back of the baffle. Believe it or not, I'm trying to simplify! Because this is a cube which is symmetrically divided, can't I just compare the surface area of the 12"x12" baffle vs. 12"x6" edge per side to use for this?

Assuming the H opening are the same dimensions as the dividing baffle, bigger baffles yields lower frequency resonances with lower Q.

Or 12x12=144...144=3.14*r^2...r=6.77...d=13.54
so now I compare 13.54" to 6" and can say what with this info? I've confused myself on where to go from here...

Thanks, and I hope I'm not too far off.

[johnk...]

Re: Orion open baffle/dipole questions

I guess I don't understand what you are trying to compare. Try thinking in terms of cross sectonal area and length. Let's forget the term baffle. Let's look at you 12" cube. Suppose this was a closed box. Mount one driver on the front side and one on the back. Wired correctly you have a dipole with 12" over all length, a 12" 'dipole moment'. Now take off the front and rear panels and mount a single drivver on a panel centered in the cube. You now have an H frame of 12" length. The difference between this and the closed cube with 2 drivers is that it uses only one driver but introduces the resonance of the 6" long, 12" x 12" cross section duct. The behavior of the duct resonance is a function of the length of the duct (L total/2) and the duct cross sectional area. Provided that the crosectional area is such that it is just big enough to contain the drivers, like 12" x 24" for two woofers, then the dipole preformance is pretty much defined by the front to back length alone. So a 12" x 24" H with 12" front to back dimension with two XLS woofers will behave pretty much the same as a 12" x 12" H with 12" front to back dimension and one woofer except for the increase SPL capability. The differences will in the behavior of the cavity resonances because the two woofer H has twice the cross sectional area.

[ocdSCHACK]

Re: Orion open baffle/dipole questions

JohnK... thanks for the help. You cleared up a lot of stuff and also helped me to better understand your prior posts. I built the enclosure and most of the speakers, but still need to put a finish on them. I can't find my camera, but will take some pics before I finish. So my next question...

I would like some opinions on good mids and tweeters to complete this Open Baffle build. I'm looking at 4 tweeters, and 2 or 4 Mid woofers. 4 Mids if I choose an MTM. I'm planning on spending between $250-500; cheaper is better, but quality comes first.
I have been thinking these choices:

Mids - Dayton RS 7" http://www.parts-express.com/pe/show...number=295-374,
Dayton RS 8" http://www.parts-express.com/pe/show...number=295-376,
Hivi M8n http://www.parts-express.com/pe/show...number=297-446, or
Hivi M8a http://www.parts-express.com/pe/show...number=297-447.

For tweeters- ???

I would love any suggestions, opinions or reviews from some of you experts out there.