Otop 8

High power and fidelity from an easy to build cabinet.
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Grant Bunter
Posts: 6700
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: Otop 8

#31 Post by Grant Bunter »

Uh huh.
Say 12.5 hrs to your place. A couple of more on a good day to the coast.
But you're still out west :)
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Mikesummers
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Joined: Mon Aug 24, 2020 8:09 pm
Location: Southchakalacky
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Re: Otop 8

#32 Post by Mikesummers »

Hi Bill etal. I am considering building the Otop8. I currently am enjoying my autotuba+klipsch rp600ms.
I purchased all of Bill’s plans.
Questions for Bill i guess: what is your opinion of the Selenium D220 compression driver?
https://www.parts-express.com/pedocs/sp ... -sheet.pdf
For home use i am considering splitting the otop8 in half. One 8 inch and one compression driver per side. I hope i can figure out the crossover. Is this a dumb idea?

I was considering an MTM design, but the horn loaded woofer accomplishes the same thing with fewer drivers i think.
Thx for the help
Mike

Bruce Weldy
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Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Otop 8

#33 Post by Bruce Weldy »

Mikesummers wrote: Sat Feb 27, 2021 8:13 am Is this a dumb idea?
By doing that, you totally negate all of the design that went into the box. No way whatsoever of telling what it would sound like. Tuning of the cab would totally change - you'd have to re-design the ports, etc.....possibly even need a different driver to work in the new size, etc....

Anyway, OTop 8 is designed as a live sound box. Why not look at the SLA line for home use?

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: Otop 8

#34 Post by Bill Fitzmaurice »

Bruce is correct.

Mikesummers
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Location: Southchakalacky
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Re: Otop 8

#35 Post by Mikesummers »

Can you splain a bit more? There is a rough plane of symmetry halfway down the box. So the mid horn would keep the same dimension laterally but not vertically (assuming throat reflectors adjusted to half box etc). Comp horn would be approx half of existing double design. Port would change, can it scale to box volume?

SLA doesnt interest me. Half an otop8 per side would fit nicely in my space.
Also how do the plywood comp horns sound compared to off the shelf horns ?
Thx

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Bill Fitzmaurice
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Re: Otop 8

#36 Post by Bill Fitzmaurice »

If you halve the woofer horn you totally change its response, and not for the better. If off the shelf horns worked we'd use them.

Mikesummers
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Location: Southchakalacky
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Re: Otop 8

#37 Post by Mikesummers »

Hey Bill since you’re an author anyway, why not write a “how to design a horn speaker” book? I would buy it, read it, and subsequently ask way fewer dumb questions.

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Bill Fitzmaurice
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Re: Otop 8

#38 Post by Bill Fitzmaurice »

If only it was that simple. It only takes an hour or two for me to get the basic design parameters using HornResp software, but that's with 52 years of horn design experience to lean on. Translating that into an actual design takes another two weeks or so, and that's using sketchup modeling, which I'm also expert with. Before this software going from idea to prototype took months. Books on horn design are mighty rare, and incorporate a lot of complex math, since they were written before modeling software existed. Sources to search are Harry Olson and W. Marshall Leach.

himhimself
Posts: 594
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: Otop 8

#39 Post by himhimself »

Best advice: Pick a design that most closely matches your need for form, then build it exactly per the plans. If it doesn’t meet your expectations (unlikely but possible) then feel free to start messing about. I’ve made a number of little build tweaks to my cabs but no change whatsoever to the basic design. No regrets,they perform amazingly.
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

Mikesummers
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Location: Southchakalacky
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Re: Otop 8

#40 Post by Mikesummers »

Ok i am almost on track, now leaning towards an OTop12 with comp driver and woofer. Hey Bill, you didn’t comment on the selenium D220 driver from above. Curve looks comparable to recommended eminence driver to my inexpert eye. Maybe a bit more efficient, so does it need a resistor added to the xover ?
Thx

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Bill Fitzmaurice
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Re: Otop 8

#41 Post by Bill Fitzmaurice »

If you think it might need padding use an LPad.

Grant Bunter
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Location: Ilfracombe Queensland Australia
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Re: Otop 8

#42 Post by Grant Bunter »

Mikesummers wrote: Mon Mar 08, 2021 3:41 pm ...you didn’t comment on the selenium D220 driver from above...
Did you compare the dimensions of the selenium to the NSD or it's most recent equivalent?
The available space for the compression driver is finite...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Bruce Weldy
Posts: 8007
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Otop 8

#43 Post by Bruce Weldy »

Mikesummers wrote: Mon Mar 08, 2021 3:41 pm Bill, you didn’t comment on the selenium D220 driver from above.
Thx
That's a screw-on driver and will require an adapter. That will add to the depth. I'd stick with the Eminence. Also, it's crossover frequency is listed as 2k....

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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