Dual MCM FLH

[jbell]

yea, lowes is weird about the arauco. One store by me carries it, the other never heard of it...

Hey for any good horn folders out there. I've got one I'm working on right now. I'd like to make a single MCM FLH. I've played with hornresp, and have what I think satisfies my current need.

It's going in a corner (the .5pi) and I'd prefer taller. (aka, not cube) I've also found that the closer to to square aspect you keep the path, the better it works, especially when things get small like this. (so this will be starting off at 2"x2")

In case anyone is wondering, the goal is to buy one of these
http://www.consumer.philips.com/c/ho...71d_f7/prd/us/
for a church youth building, and replace the speakers with something with some oomph.

It has a high pass at 40hz, and crosses at 150, so I worked till I got something that was no louder at 150, than 40. yea I know I could have done a lot different in this design, but I think this will work in it's given purpose.

so... suggested folding?

[danielm]

I picked up a sheet of Arauco ply yesterday at Lowes with some other stuff. Just checked and looks like they charged me for CDX... $24 and some change. I got a bunch of items and didn't notice.
I should have bought twenty pieces at that price.

[jbell]

nope, 24 bucks is the going rate for arauco.. just picked up several sheets, and that's what I was charged as well.

For anyone thinking a dual mcm is a little much.. I agree, I was looking for something a little more pack friendly, so I made what I call, a bass-stick. 12x16x48. 4 of them set up in a V shape with a top plate, should give mighty respectable output. (131db 40-200@20v per driver) It's also brain dead simple to build. Knocked this one together in an afternoon.

Here's pics of the first trial, it's breaking in at the moment, but initial tests line right up with hornresp.

THANKS DAVID for HORNRESP... I'll cap-attack that one. David needs a big shout out for his efforts. It makes people like me, look like they know what they are doing.

[danielm]

131db 40-200@20v per driver??? What you been smokin' Jim?

[jbell]

no smokin... you run the sim.
Real world on single cabinet is slightly outrunning the sim.

4 cabinets@20v per driver = 131db.

[davygrvy]

Hey Jim, This is neet. Compression ratio is kinda high at 8.32:1. Is the driver surviving it? Is it safe to go that high?

[jbell]

no sweat... that little 8 takes a lickin' and keeps on poundin'

I was leery of the compression ratio as well, but that was the only way I could get flat response. I asked and asked... but finally decided to go against the 3:1 conventional wisdom. Hey for $25, I figured it was worth a shot, and if I shredded a cone.. no worries. As it turns out, with a 40hz high pass... man it sounds great, without it, it sounds a bit muddy down low. My thought is that the high compression ratio chokes lower freq more than upper, which is why I don't like hearing 30hz out of this. (my earlier dual driver cabinets that keep the first part of the horn segment to be almost square doesn't have this issue) I have not pushed a cabinet to failure, so I don't know if it'll thermal or physical fail first. My guess, especially with a very small rear chamber, is it'll melt before it tears.

I think the compression chamber helps keep the cone alive as well. All of my current efforts with the 55-2421 are all FLH with compression chamber. (as much as I like TH... this driver is just a FLH native...)

I am hesitant to turn my single driver cabinets over to others, because I like to keep them under 20v per. In that case, the dual driver cabinets (8ohm total, drivers in series) are much safer in others hands. I'm currently working hornresp on making the bass-stick 17" interior dim, so I can dual driver it, just for this reason.

At some point I'll stop playing with FLH designs and this driver... but right now... it's just too tempting...

[davygrvy]

Segment 4 is the V-couple part, right? It must be cause I'm scratching my head. What's the degrees spread to get that volume? I'd think section 3 would be a bit shorter than 120 unless the change is happening not where the top turn is. This is really neet.

I wish I had a special CAD app that took hornresp export files as input and would fold cabinets for me. I talked with bgavin about that once, but he got "ownershippy" with me about intellectual property. That's no way to start a team project, ya know?

[danielm]

"Ownershippy" and "DIY" just don't mix well.

I noticed MCM has raised the price on this driver. Hmmm... the party maybe over.

[jbell]

Originally Posted by davygrvy

Segment 4 is the V-couple part, right?

You got it. I left segment 3 at 120, because the v-couple starts at the bottom of the cabinet. Couple is 90 degree. I intentionally designed it for a 90 degree, that's why it's only 12" front to back, 16 wide, and 48 tall. I left segment 4 in, just because that's how I will use it outdoors.

As far as price on mcm, you have to look for discount codes. If you are not on the mailing list, you can google for them usually. The one that just ended on the 31st, had 55-1740's on sale for $15.99... and 55-2421's extremely cheap too. I grabbed another 8 of each, just because.