BillFitzmaurice.info

Hey guys so I've got a not quite tuba question but you're the guys I go to for this stuff

I built a Selenium Pro audio folded horn about 3 years ago using these plans

I built it (before I found you guys of course ) and made it half the width (20'') of the plan for easier transport using this15'' woofer
Specs:
300 watts RMS
Fs: 33 Hz
Vas: 11.1 cu. ft.
Qms: 5.13
Qes: 0.32
Qts: 0.30
Xmax: 3.0 mm

This thing has been sitting in my garage for a while now acting as a table and garage sub so I decided to sell it on Craigslist to fund my T39 build

Now here's my question the guy I had come over listen to it wanted to put some more power into it as I was only using an old 100w peavey, but I don't want it to blow during the demo. I agreed to meet him again tomorrow, take the sub outside so he can hear outside without a room since he'd like to be able to do outdoor shows with it, and put some more power into it.

What frequency should I low pass it at, and what recommendations for my xti 2000 do you suggest? -6 or -12 db limiting? The horn is probably a 10 ohm load, so the xti would give about 69 volts, so a -6db is about 34V (115 watts) and -12db is 17V.

I'm awful at measuring path length since I'm never sure where to place my line, but if I place the tape measure along the path it's about 4-5-ish feet, which tells me this thing is like a 60hz horn.

Does it really mean that, that huge heavy thing that is bigger than my TT only goes to 60hz??
I guess I'm just spoiled, but that just seems awful...

The plans for the sub says it "can be used from 40 to 200 Hz with maximum efficiency" but I'm not sure I believe that after looking at the numbers...

What do you guys think, cross at 50hz and call it a compromise?

Charles Warwick wrote:
Does it really mean that, that huge heavy thing that is bigger than my TT only goes to 60hz??

As far as the horn loading goes yes, that's it. Below that it works as a direct radiator, with direct radiator sensitivity. With only 3mm xmax I wouldn't put more than 100 watts per driver into it, high-passed at 40Hz.

This thing looks ALOT like the design I've been playing with. I think this is going to help me, thanks man. And yeah, as Bill said, with that xmax, I'd high pass at 50hz and no more than those watts.

I'm awful at measuring path length since I'm never sure where to place my line, but if I place the tape measure along the path it's about 4-5-ish feet, which tells me this thing is like a 60hz horn

Plans say on page 2 that the medium length of the horn is 147.2cm.

Saves any tape measures.

Dave Non-Zero wrote:Plans say on page 2 that the medium length of the horn is 147.2cm.Saves any tape measures.

Hahaha, nice, I'm so unobservant.

Here's a picture of it in case anyone is curious: http://i10.photobucket.com/albums/a104/ ... SC2308.jpg It effectively looks like a T30 without the extension.

So, the guy came over today and I hooked up my xti 2000, -6db limiting 48dB HP at 45 hz and 110hz LP, on one channel and the two OT12's on the other.

Sounded quite loud wedged in a corner of the garage, not so much when the guy pulled it out of the corner to see what it sounded like 5-6 feet out (well duh), and pretty decent when we moved it outside. A good bit weaker outside especially when he choose some dubstep as a sample material so it wasn't especially loud since part of the bassline seemed to be below 50hz.

But regardless, he seemed satisfied and hauled the monstrosity away and left me with 200 bucks! The damn thing was made of 3/4 MDF and weighed far too much.

Now I get to go to Lowes tomorrow to buy some plywood for 2 t39s. Excellent.

Thanks for the advice guys!

hauled the monstrosity away and left me with 200 bucks!

result!

Glad to hear that you're "on the road to recovery"!

Charles Warwick wrote:Now I get to go to Lowes tomorrow to buy some plywood for 2 t39s.

Unless your Lowes carries 1/2" 5-ply Arauco, don't bother. If there is a Menard's close by, phone them and ask for "Baltic Birch" or 5-ply fir or pine. Tell them you are building cabinets, but you don't want any thin veneers.

DJPhatman wrote:

Charles Warwick wrote:Now I get to go to Lowes tomorrow to buy some plywood for 2 t39s.

Unless your Lowes carries 1/2" 5-ply Arauco, don't bother. If there is a Menard's close by, phone them and ask for "Baltic Birch" or 5-ply fir or pine. Tell them you are building cabinets, but you don't want any thin veneers.

+1, call around first since (in my area) only a few lowes carry it, not all of them.

DJPhatman wrote:Unless your Lowes carries 1/2" 5-ply Arauco, don't bother. If there is a Menard's close by, phone them and ask for "Baltic Birch" or 5-ply fir or pine. Tell them you are building cabinets, but you don't want any thin veneers.

I have checked around various places and still have yet to find BB in the central iowa area for a reasonable price. Our local lumber yard used to carry it but went out of business a few years back

I can get BB in Des Moines (about 45 minutes away) for about 70 bucks a sheet, but I can get the 1/2 Arauco from our Lowes here in town for 20 bucks a sheet, so the Arauco wins for me.

On a side note, has anyone been noticing a good amount of voids in the Arauco they've been buying? These are the mouth panels for 4 J110:


It might have just been that sheet, I don't know, but I feel like there are more than there used to be...

Voids are a problem with cabinet designs that use large unbraced panels. We don't.

Wow, that sucks. My three arauco that I got about three weeks ago are almost flawless, even better than the ones I used first and those were better than what you posted.

Looks about like most of the acuaro I get.