An atypical OB Line array

[johninCR]

It's been over 2yrs since I built my last OB line arrays. In the meantime I've been chasing dynamic OB bass output in as small a form as possible, but none of the folded forms got me where I wanted in my narrow 12' x 21' room. I finally decided to go back to arrays.

They consist of 5 15's per side. The center driver is a coax, the Hawthorne SI. The next 2 drivers are Warrior 15's that I picked up at http://www.musicsupplycenter.com for the whopping price of $20/ea. The top and bottom are low bass drivers, the Hawthorne Augie.

I have them mounted on doubled up 18mm plywood with just enough side supports for rigidity, which I have placed against the side walls giving me as much boundary reinforcement as possible and to keep them out of the way. The idea was to ensure dynamic bass for any type of music I throw at them by using a floor to ceiling bass array. I roll the Augies off very low. Then I let the Warriors run up higher on a 1st order filter. Then I roll off the top and bottom off for the coax woofer leaving the tweeter in the center for the top end.

I was trying to obtain array behavior starting at the bottom with a gradual transition to point source for high frequency. Not only did it work, but the results surprized me, even with, at this point, a guesstimated 4-way active cross. Not only do I have way more bass than I need, but these 18.5"x86" monsters absolutely disappear. In addition, I'm getting the sonic signature unique to arrays. That is instead of bringing the performers into your room like a good point source setup can do, you are transported to the venue of the live performance with the sense of greater size and space, but in this case the sharp imaging and placements in the soundstage of a point source speaker are retained. It's the best of both worlds with the only compromise compared to a full range array being the sweet spot is only slightly enlarged over a point source, but in my setup I don't need the "sweet area" instead of a sweet spot for two.

I put a couple of rubber feet on the bottom and they're held upright by bungie cords attached to a rafter a few inches above. This decoupled connection keeps the woofer from transferring energy into the structure, and it give each speaker unit a resonant frequency of less than 1hz. This combines with the woofers just idling along to very little baffle vibration.

I'm one happy camper, and I know the best is yet to come as I get things measured and really dial in the XO, but they're sounding great already.

[Pano]

Those look great! Certianly NOT typical. Just wait 'til Magnatar see these.

I like the increasing size from the center out idea. What are x-over points and EQ?

Nice rig.

[johninCR]

Originally posted by panomaniac
Those look great! Certianly NOT typical. Just wait 'til Magnatar see these.

I like the increasing size from the center out idea. What are x-over points and EQ?

Nice rig.

Magnetar was my hero with those OB WMTMW's with using those Madison 21's. If I was stateside I would have scooped up both pairs at auction. When I found out he dismantled them, I decided someone needed to have a manly stack of drivers on OB, so why not me, especially since I already had the drivers to pull it off.

I'm not sure what you mean by increasing size, unless you're talking about Magnetar's. Mine are all 15's, except for the screw-in tweet for the center coax.

Regarding the XO & EQ, I'm just having too much fun playing around with Thuneau's program that I haven't settled on anything. I need to measure things and import the FRD's, so I can do it right.

[Kensai]

Impressive. Inspiring even. Wonder if it will be inspiring enough to get me off my lazy butt and build the 6' tall arrays of 6"x9" drivers I've been thinking about. Only need another $40 worth of drivers plus the cost of building and standing the baffles up. I can't bungie mine like you did, so any thoughts on keeping these things upright? I'm a little wary of having so many 30oz magnets so far off the ground with a little one running about.

Kensai

[johninCR]

Kensai,

With a little one around I'd at least run some kind of safety cable. Just paint it the same color at the walls and it would be nearly invisible. Then you can rest easier with a smaller base and higher center of gravity.

[ScottG]

I also use the Madison driver.. specifically two 10 inch 16 ohm Knights in parallel for just the midbass (60-250). Pretty "punchy" drivers for an open-baffle config. (while still providing the benefits of open baffles in this range.)

I'm surpised you were able to get them to ship to Costa Rica. Several years back (when they were steelsound and I purchased mine), they wouldn't ship anwhere but the continetal US.

[Kensai]

Under the slope of the vaulted ceiling in there and my wife's critical eye, cables to the ceiling just won't happen. Maybe I can tack cables to the backside of the entertainment center.

What do you think of securely bracketing a base plate behind the baffle, possibly framed in by wings or partial wings, with a vertical post for mounting weights? Use cheap free weight plates with layers of foam between to keep them silent. Should be about 12lb of magnets in each line, so less than 20lb each counting the rest of the drivers and the baffle material. Think maybe 20lb of weights would keep it stable?

Or maybe the plate could be attached to the baffle a bit higher then ground level so that the lines would tilt back a few degrees. Weighting the plate this way should apply a strong downward force on the baffle. Seems like that would be more stable than having the base plate attached at 90 degrees at the floor.

Kensai

[Pano]

Hey John - I forgot you are in Costa Rica. San Jose? Cool place!

What I meant by the expaning size was -

1" in the center
15" around the middle
2x15 farther out
2x15 lower frequency out farther.

You come to the center as the frequencies go up. Or go out to the edge as the frequncies go down.

Keep us informed of your crossover progress.

[johninCR]

Originally posted by ScottG
I'm surpised you were able to get them to ship to Costa Rica. Several years back (when they were steelsound and I purchased mine), they wouldn't ship anwhere but the continetal US.

I have a Miami shipping address. Between shipping, duties and taxes it tripled the price, but still a bargain compared to anything decent available here.


Kensai,

Without some attachment up high, you'll need both mass and width and depth at the base, especially if they sit on carpet. My placement worked perfectly and I have no base at all. They balance on the rubber feet.


Panomaniac,

Will do. Yeah, CR is cool. Great weather, probably not too different from Maui, but Maui is still one of those dream vacations in the future.