JBL L 150 Speaker Construction

[bluenote.ted]

Hi,
Does anyone know why the midrange driver in the L150 speaker is isolated inside the enclosure with a sub-enclosure which appears to be a sealed cone made out of cardboard-like material ?
Thanks,
bluenote.ted

[Robh3606]

Hello ted

Yes to isolate it from the backwave preasure of the woofer and to load it properly. Without the subenclosure the midrange cone would be modulated by the woofers backwave and potentially overdrive and damage it.

Rob

[BMWCCA]

What he said, but because . . . the L150 is not a bass-reflex enclosure like most other JBLs. Using passive radiators requires a sealed box.

[rdgrimes]

FWIW, the L150, L96 and L112 all use the same MF isolation tube. It's a plastic tube that's glued to the front baffle. Without it, the LE5 cone almost flies out of it's frame. Been there......

They use it whether the box is sealed or not.

[bluenote.ted]

Thanks for the info on this aspect of the L150 speaker. this hard paper (and not plastic) cone sub enclosure for the midrange unit makes me wonder why they did not do the same thing for the tweeter which is immensely more easily removable. I would hate to have to replace the midrange unit as one would need to use a razor knife and who knows what else. I wonder why they did not just isolate the midrange and tweeter upper area inside the box. Any ideas on the above-mentioned??

[Allanvh5150]

The 044 in the L150A and the 033? from the L150, are sealed units so they are already protected from ouside influence. The LE5 midrange is very easy to remove from the cabinet although sometimes they do stick a little.

[rdgrimes]

Thanks for the info on this aspect of the L150 speaker. this hard paper (and not plastic) cone sub enclosure for the midrange unit makes me wonder why they did not do the same thing for the tweeter which is immensely more easily removable. I would hate to have to replace the midrange unit as one would need to use a razor knife and who knows what else. I wonder why they did not just isolate the midrange and tweeter upper area inside the box. Any ideas on the above-mentioned??

The L150 and L150A use different parts. The main reason for not partitioning the cab is that they need the total CF for the woofs. Being sealed means it needs more CF inside. The isolation tube is a bit if a pain, but it functions very well. It should also have about 1 SF of 2" fiberglass stuffed in it, and the hole for the wires should be sealed with goop.

Some later models of JBL speakers with built-in subs did have partitions in the cab.

I can attest to the fact that with the older cabs, these tubes do tend to come loose. I'm not sure how the MF driver is attached in the 150, but it's very easy to remove in the 150A.

[bluenote.ted]

I have a pair of L 150's and not L 150 A's.
The hard paper cone is totally enclosed with the goop surrounding the wires that go into it. I'll tell you something, the paper cones are rock solid surrounding the back of the midrange drivers, and I cannot even imagine how one would begin to remove the midrange driver if I ever had to replace them. I know the tweeters are easy to remove. I have already done it once. But the midrange drivers are a whole nother story ! I would be very interested to hear from anyone who knows how to do it. I would imagine you would have to cut out the paper sub-enclosure cone first, but even that process would stretch the wires to the breaking point. I don't think JBL expected that these drivers would ever be removed. ??? By the way, this is my very first posting of a thread on this website and I am thankful that such a great community as this exists on line. And the speakers sound great !

[rdgrimes]

The LE5-10 mid driver simply lifts out the front. There's enough slack in the wires to allow you to lift it up and disconnect.

[LRBacon]

Don't forget to remove the 4 screws holding the LE5-10 in place before trying to pull it out from the cabinet. They may be hex or Allen head screws.

Larry