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Mark audio OB?

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I've gotten the option to buy 4 eminence alpha 15s for a very reasonable price and was thinking about running 2 per side with a mark audio fullrange and a dsp active crossover. I was wondering which driver should I match with them and/or is there anything I should change or be aware of that isn't glaringly obvious to me? Thanks in advance!
 
frugal-phile™
Joined 2001
Paid Member
Ceratinly any real-world OB (not like some of the ones we’ve used — 17 ft wide) will have helper woofers. The Alpha 15 is a darling of the OB crowd due to its low price (i’d suggest a good price is on the order of $100USD for the quad) And its high Qt means that one can design a baffle without any need for EQ to level the bass.

Any of the Mark Audio can be used as a midTweeter, but the trade-offs have to be considered before choosing. Budget is of course 1 of those. With 2 amplifiers you do not need to worry about relative sensitivities, but you do need to consider how loud you want to play and how low you will need to XO. The louder you want, the bigger drivers should be considered. The XO is really determined by the baffle shape, primarily the width. You can look at MJK’s and Linkwitz’s discourse on these subjects and the math. The lower the XO the better off you are with a larger driver. A smaller driver will have better HF dispersion, and to a certain extent an advantage thru the midrange. For optimum performance the Alpair 7.3/6.2x/5.2 should be looked at. On a budget the Pluvia 7 becomes a choice. Certainly any of them fall withing the set of better FRs available.

Personally i’d look to the A10p or the A6.2p. I have 8 OB 10” looking for a home and i have a baffle concept and the A10PeN in mind.

One thing i question is whether the quality of the A15s will drag down the quality of the whole system. I was not overly impressed with them, even with some mods (i still have more to do), But some people find them just fine. If you can get a fast price what do you have to lose? With the DSP you can correct some of the holes, and you will have very high XO flexibility (what DSP XO?). If you find the Alphas are not up to snuff you can simpley replace them. Pure Audio for instance has an OB specific 15” evolved from their use of the A15. Eminence has pricier woofers that come recommended (but you will need to use your EQ) and at the high end probably the Acoustic Elegance.

Hopefully that gets you started. You have some research to do.
 
As far as the woofers go I was definitely thinking about running a higher priced woofer and using the dsp to correct for any issues but with the price of these 4 woofers being less than a single driver of the others I was considering, even if I upgrade I'm not really out much. I was trying to pick between the alpair 6 7 10 12 all the pen series as I'm not a fan of the metal cone sound and I've heard nothing but amazing things about the enabled drivers and have been dieing to dry some. I was originally thinking about running a horn but wasn't happy with the bass I got so I was then thinking about running a 6pen with two 12pw in a double stacked onken enclosure but that's a tad out of my price range at the moment. I know that I'm going to be happy with any pen alpair I get, its just finding a way to augment them with some tight dynamic bass. Am I headed down the wrong road with the ob?
 
frugal-phile™
Joined 2001
Paid Member
We designed the A12pw Mar-Ken to be versatile, and an A6.2PeN MTM is definitely in our thots.

Do note that the A7p is an outlier in the line. The A7.3 sounds more paper-like. When we 1st heard about the A7p we hoped for similar voicing vis-a-vee the metal A7 as the A10p to the A10.3 and the A6.2p to the A6.2m. It didn’t happen. We are still lobbying with Mark Audio re this. Treatment & lonnnggg break-in seem to sort its issues.

dave
 
I was originally thinking of doing a Trio 15 style, but I'm slightly worried that having the fullrange on such a wide baffle could screw up the imaging, isn't the narrower the baffle the better as far as imaging goes? Would it work if i had the two woofers placed vertically and then the full range off axis to the side either on the edge of the baffle or placed completley seperate out from the main baffle so that it can have its own baffle tailored to it? Or would the deviation from the main vertical axis that the woofers are on create its own imaging dificulties. Would I be further ahead running a H or W baffle with the woofers and put the fullrange on top?
 
As Dave said, M J King OB Theory and Siegfried Linkwitz will tell you almost all there is to know about open baffle. The baffle for your wideband doesn't want to be so large as to impede the reflection from the front wall. A frame for the woofer has a resonance caused by the cavity. It's useful to have separate baffles so you have more flexibility with positioning
 
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