PMC TLE1 style sub

[MJL21193]

Quote: "...Oh, you can hear the difference easily enough "

Oh, no I can't. When I was 15 I made boxes that did all the work - flex, jiggle, emit alien flatulence. Now I build speakers where there are only one or two places sound comes from - the driver and the port. That is, sound that I can hear.

[Dr.EM]

Thanks a lot for the replies

I've very roughly drawn what I think is what Scottmoose specified, I expect i'm way off the mark though . The response down to mid 20's is good enough I reckon, my speakers (602's) are down 3db at 49Hz, so its a fair bit extra extension

I always thought MDF was the better material. Clearly that isn't the case, is plywood as easy to use (it doesn't split apart easily?). I don't see there being too much resonance in either material with a folded line however.

The push push construction is interesting. I'm not as keen on the physical appearance of it, but then I might find myself wondering if i've missed out on something by not using it in the future. For now I think i'll stick with the PMC type arrangement.

[MJL21193]

Dr.Em: What you have drawn looks good. You might want to position the drivers away from the start of your line, as in reverse the placement of your dividers.
What P10 and scottmoose are saying is that baltic birch plywood is better than MDF. As the resonant freq. of either material is greater than 200 Hz, I believe it doesn't matter. Baltic birch ply is pretty expensive though, and can be hard to come by.

First and foremost: have fun.

[planet10]

Another thing about MDF i just remembered -- i don't know if it is relevant, especially once a finish is applied, but MDF is not air tight. You will see on occasion a piece of 19mm MDF used as a convient platform for smaller pieces on a big vacuum hold-down CNC panel router. The vacuum sucks the top pieces down right thru the sheet underneath it,

We could have as much free MDF as we wanted. But we'd rather go out and buy BB ply because of the sonic benefits.

I am convinced that MDF has gained its status because some smart fellow promoted this new material (when i started speaker building it was not available -- we used K3 particle board) as new superior tech. He did it not because it was better, but because it was cheaper, cheaper to work with, and cheaper to finish. Now the myth is so ingrained even vetern speaker building companies believe it to be true.

dave

[MJL21193]

I have taken a break from burning all of my inferior quality speakers to write this. Another thing about MDF is that it doesn't burn well.

[planet10]

Originally posted by Dr.EM
I expect i'm way off the mark though

A ways off...

dave

[planet10]

Originally posted by MJL21193
Another thing about MDF is that it doesn't burn well.

Actually if you get the fire hot enuff it burns just fine -- even when it has been in the rain for months...

we burn a pile something like this 2x a year... mostly speaker boxes

dave

[jleaman]

Originally posted by planet10


Actually if you get the fire hot enuff it burns just fine -- even when it has been in the rain for months...

we burn a pile something like this 2x a year... mostly speaker boxes

dave

I vouch for this

[Scottmoose]

Well, it has to be good for something... the the bonfires be built. Vile stuff. Chipboard (particle board) is better. At least this one would be well-braced, but that's still not going to prevent audible panel vibrations. In this case, to push them below the passband of operation, you'd need to go to over 2 1/4in thick of the stuff, which instantly causes even more problems with energy storage. Nah. Not for me.

[pinkmouse]

MDF, yes, it can cause problems in wide range boxes with large unsupported panels, like the typical single driver lorn loaded cabinet, but for your limited bandwidth bass bin with all those internal baffles providing support, then I can see no problem, personally speaking.