BillFitzmaurice.info

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

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

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?

Bruce is correct.

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

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.

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.

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.

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.

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

If you think it might need padding use an LPad.

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...

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....