Suggestions for my first dipole using left over drivers?

[jimluu]

Hi, I have 4 Focal 6w4254 mids, a pair of ow1 from an abandoned project. I want to use them in an open baffle design, similar to the arvo or iris. Does anyone have experience with these drivers? Zaphaudio site doesn't think hightly of the Focals for some reason. Should I just ebay them if they are so bad?

thanks. jim

sorry for not providing the specs....zalytron site is down.

Note from moderator.
Two threads dealing with the same subject have been merged

[ThomasW]

Realistically the Xmax is too low for OB used...

[jimluu]

is xmax that important if I use it between 250 and 2500hz?

[BobEllis]

According to Linkwitz's SPL_Max spreadsheet you should be able to hit 110+ db down to 250 Hz or so with the 6W254 in a 350mm effective path difference. Now you've got me thinking about what to do with my 4...

[jimluu]

Just found 4 Focal 12" poly woofers.....how about wmtmw crossed at 300/2500, and a pair of PE 15" IB woofers per side on the bottom. It might be slightly larger than I wanted.

[BobEllis]

What's the Xmax on the 12" woofers? You may not get very low with them if they are typical low xmax Focals.

I've been tossing around the idea of using a pair of PE RSS315s per side in a similar setup. There's free shipping for the next few days.

[jimluu]

What's the Xmax on the 12" woofers? You may not get very low with them if they are typical low xmax Focals.

I've been tossing around the idea of using a pair of PE RSS315s per side in a similar setup. There's free shipping for the next few days.

I think that the x-max on the 12" is only around 8mm. I plan to use them only from 80 - 300 hz, then a pair of PE 15" rs or ib series on each side. I want a truly 'over-the-top' design since this is my last pair of speakers that I planned to build.

...edit: just bought a 2 pairs of rs180s, so I guess I may not be done yet.

[BobEllis]

You'd need 600 mm path difference to allow a 12" Focal (assuming ~530mm sd) to keep up with the mids (110 dB) down to 80 Hz. An H frame would work if you dont want the width. The RSS315 would do it with a 400 mm difference.

I gave up on being "done building" a LONG time ago

[jimluu]

You'd need 600 mm path difference to allow a 12" Focal (assuming ~530mm sd) to keep up with the mids (110 dB) down to 80 Hz. An H frame would work if you dont want the width. The RSS315 would do it with a 400 mm difference.

I gave up on being "done building" a LONG time ago

I was going to mount the focal mids and the focal woofers on a 14" wide common baffle in a wmtmw config. In order the achieve the 5-600 mm or so path difference for the woofer, I'm thinking about using the U-frame instead of the H-frame for cosmetic reasons. Can I stick a 12" long and 12" diameter sonotube behind the woofer for a simple U-frame?

[jimluu]

Suggestions for my first dipole using left over drivers?

Hi, I have 2 pairs of focal 6w mids, a pair of ow1 tweeters that have been sitting around for a while. They were part of a kit that I bought from Zalytron around a year ago. I also have 4 focal 12v726 12" woofers sitting around. I've lost interest in building the typical box speakers and am thinking of putting these in a dipole configuration. Admittedly, I am not an engineer and am too old to learn new tricks so any thoughts and advice would be much appreciated. I'm thinking about using a 13" baffle, WMTMW configuration with the above drivers. For crossover, something real simple, maybe a first order at 500 and 3000. To bring up the bottom end, I plan to get a 15" rhytmic active servo sub each side. Think it will sound ok?

Focal 6w specs: http://zalytron.com/pictures/6WSpecifications.pdf

thanks. jim.

[cjd]

hmmm

good morning physics... care to take a step outside for a while?

Actually am confused about the sorta re-post.

[jimluu]

hmmm

good morning physics... care to take a step outside for a while?

Actually am confused about the sorta re-post.

I've been thinking for a while. Now that the weather is warmer, I'm getting ready to build. Maybe I'll just do it and see how it turns out. The only thing I don't have yet are the rhythmik subs. At around $1000 a pair, it's the only additional expense. Do you think it will work with this set up? thanks.

[cjd]

I can't share thoughts on the Rhythmic.

Crossover, you can't just slap textbook values in there and have them work as expected 99.999% of the time. And first order on those Focals looks, well... not sure about that. 3kHz is high for them in the first place. Going to OW1's I'd see about 4th order around 2200Hz perhaps. You could stretch things and go 2500ish 2nd order perhaps. Either way a zobel on the Focals is probably required. You'll be looking at less ideal vertical lobing from driver interaction too far off-axis with the center to center spacing vs. frequency even in this range.

500Hz means your center to center needs to be pretty small - with a 1st order network impossibly so. Maybe try pushing to a max of 350Hz 4th order. 200Hz 2nd order maybe.

If you're just messing around to mess around, ... do whatcha feel like. But your initial proposal DOES pretty much throw physics out the window.

My (more in-depth) thoughts.

C

[jimluu]

thanks cjd. Is there a way to make these drivers work in an IB? If the physics is all messed up does it mean that they can only go in a box?

[cjd]

Oh, you can go open baffle. Or do you mean IB? I'm even more confused now.

I'm simply saying you seem to be going at this without any understanding of how you plan to get to the end. You pick crossovers based on "real simple" - I assume simple to assemble being the key? Not really sure. You pick topology separately from crossover points (at least, the two don't mesh in my mind).

Yes, you absolutely CAN get the components you have chosen to work together open baffle. But you're going to have to apply yourself to the science of speaker design for best results. This doesn't mean you have to push extreme slopes and such either, but you have to understand what your choices MEAN and how to work within the limits of your chosen components.

I can mount the wheels from my wife's car on my car. I can go find standard thread nuts that snug down just fine at the hardware store. But it's not going to work very well at all - my car comes with OEM 185/60/15 and hers 185/65/15. Both cars have metric threads, and of course a standard thread won't be secure - not to mention the right shape to properly hold the wheel in place. Offset is fine, 36mm and 40mm, as is bolt pattern (5x100). But this is a vague analogy to what you are doing. Bigger tires look better, they fill out the wheel well better. And they physically fit. (topology decision). Now let's connect it all as simply as possible (hardware store nuts) without really understanding what it is we're doing. I can go in a straight line and it's probably ok (sitting JUST in front of the speaker just so *might* get what seems to be acceptable performance). Try to turn and all is lost. (power response, off-axis, who knows what all funkiness you'll find).

C