OT15 - built at last: amazing!

[GeoffBass]

Hi all,

I FINALLY got my first of 2 single 15" OT15's up and running (despite SWMBO's best efforts!). At this stage, I haven't put the piezo's in, but all I can say is........ WOW!!!!

The clarity of midrange tone was very obvious, even very slight adjustments of the tone control pot on my bass yield quite significant changes in tone, and for once, can be easily heard!

The drivers I used were Foster C380K60's, formerly part of a three way 15"-10"-horn system I built about 20 yrs ago. The difference between the same driver, first in a 42.5 Hz -3dB reflex enclosure, to the OT15, is amazing. Notwithstanding the fact that the reflex enclosure never had the passive LPF on it, even without it on the OT15, it still produced a major increase in clarity. These particular drivers have a fairly decent upper midrange, not what you generally get from a 15" driver, so for bass, even pop and slap style playing has plenty of bite and sizzle, without exaggerated fret noise.

My previous rig used a JBL E155 and 2 x E120's biamped. While the bottom end is a little less with the OT15, the tone is sooooo much better, and I can pick it up easily - the old pair of boxes weighed in at over 220 lb, and was a large stack!

I wound my own inductors, using the plastic reel from a roll of bricklayer's string, 2mm diameter enamelled wire, with 7 layers of neat winding.

If you have an LCR meter, you can do the job easily. Just wind on say, 5 layers, then connect the LCR meter to the bared end of the winding, and, using an alligator clip, bite through the varnish, measure the inductance. Make sure you don't have any steel too close to the winding, especially through the middle! If your reading is too low, add another layer and try again. Each layer adds progressively more inductance than the previous, so you may find you need to unwind a few turns to get it spot on. It doesn't matter that you pierce the varnish - its only in one spot here and there, and you need to give the finished winding a coat or two of Isonel motor winding varnish or similar, so a nick here or there doesn't cause any drama.
It didn't take long, it cost peanuts, and works so well!

Thanks Bill for your excellent design work, I have yet to hear one of your 10" driver based enclosures, but if this is anything to go by, I am certain that I won't be disappointed!

Cheers,

Geoff

[tdogg]

pics?

[Mikey]

pics?

Yes! Pics please!