Dual MCM FLH

[jbell]

Well, I'm far enough along in my test cabinets, that I thought I'd create a thread for this.

I reformed by dual 55-2421 cabinet to end firing, moved the first horn path to center, instead of offset, and made it out of fresh ply, so it's 'to length.' VERY respectable numbers down to 43hz. No it's not flat to 40. but it's within a half step, so I'm happy.

The numbers aren't bad.. I especially like the very flat 103db through the 50's and 60's, a little dip in the 80's, and then off to the races as you hit low hundred's.

For $50 in drivers and 1.5 sheets of ply.. it's pretty respectable.

Measured C-weighted, corrected to flat, rounded down to nearest .5 db 2.83v / 1M / Drivers in series

HZ DB
40 99.5
43 102
46 102
50 103
53 103
57 103
62 103
66 103.5
71 102
76 101
82 101
88 101
95 102
102 104.5
109 107
117 108.5
126 107
135 105
145 102.5

[saddlesore]

JBell - What are the physical dimensions of the box?

As a "horn-rookie" it is going to be interesting to see how your sub compares to Patrick's dual 8" MCM sub that he is making over in the "smallest TH-sub thread".

That is, both of you are using the same drivers (dual 8" MCM's) and the rest of us get to learn/see the results. Thanks again for all the sweat and sawdust!

Steve

[littlemike]

Jim,

Nice looking response for a pair of 8's. Any updates on performance?

In the pics it looks like the cabinet is end-firing, am I seeing things wrong?

[jbell]

performance numbers are above. cabinet is 21x24x33. They are being installed this week, will let you know how they perform 'in room'

Yes, I refolded to 'end firing' for a couple reasons. First, in this auditorium that they are going in, end firing happens to work better, and second, I wanted to try them with as a base for my tops. (in my pa on the cheap application that I'm working on.)

They can easily convert from end to 'normal' firing.
One interesting thing to note. I goofed up one of them, and didn't transition on the first flare correctly, and got an extra db at 66hz, vs the 2nd one that is basically flat. If you look at the pic above, you'll see what I did wrong... Not sure, but the extra db at 66hz almost seems like a bonus.

[jbell]

Got everything in place in my auditorium install. Dual MCM is in an 'upper' tricorner of the room. It took awhile to get the room modes evened out on positioning/aiming into the corner, but I finally got a +-3db throughout the room. I had to aim the sub into the corner at about a 30degree to one wall angle, with enough room to corner, so that sound could come out both sides about evenly.

Basically the room is -10db vs 1meter levels, which means that about 10-12volts is about all I can stand, before metal conduit, etc. starts buzzing like crazy.

That's with one of them... don't think I need to install the 2nd.

A FLH that's flat to 40 (like a TH...) is pretty cool.

[David_Web]

Looks really interesting.
How would they preform in 2pi? (single)
Max SPL according to HR?

[jbell]

The numbers above are a single cabinet, drivers in series for 8ohm, outdoors over grass, so very close to 2pi.

Low 120's outdoors at 1M is as far as I've pushed. Indoors, once I get much above 100 at listening position, things start vibrating, so I can't really open it up, without things starting to sound nasty.

Unfortunately, it'd probably take a week to vibration-proof this building, just so I can turn it up a little.

[boydon_lepasci]

Originally posted by jbell
Unfortunately, it'd probably take a week to vibration-proof this building, just so I can turn it up a little. [/B]

You'd be surprised how fast an airless spray gun can put one of the various coatings on a large area. Then you crank it up and bury the stubborn spots again. It makes everything(wires, pipes, ducts, structural...) look the same, but still servicable in the future

[jbell]

I thought I'd update this thread with last weekend's success.

A pair of these for outdoor events, seem to work very well.
zed14 and an xti1000 make for an easy set up.

flat to 40 is nice... very nice.

[danielm]

Jim has all the fun...

Straighten that kick drum head.