sootshe

No, not in the upper bass.............mainly the lower end. Since changing amps, I now have the ports plugged. With the new amp the bass was very soft withe the ports open. When I closed them up the bass came back to the tightness & level that I am used to.................................................and no, I don't get any resonance any more regardless of volume level......................ENJOY!

and finished..................the sides & rear are now 36mm thick..............no need for sand here!

and more glue

Here's the glue.

I've been through pretty much what has been covered here, in terms of the resonance coming from the bass bin and this is not in relation to getting the LS to play lower, but rather to get the best sound from what is there. .................Let me say first that if you haven't converted to one of the more popular mid range horn options & another alternative crossover, then the resonance from the bass bin might be the least of your troubles........................................................Once I'd cleared up those 2 issues, I realized that the bin braces just weren't stopping these resonances & I firmly believe that they are coming from the cabinet.................................................It shows up as others have described, in voice reproduction & was most sensitive to me with some styles of electric & acoustic guitar, at particular frequencies, making the speakers almost unlistenable to my ears...............................so, what to do...............................because I could feel & hear the resonance coming from the actual cabinet & to a certain extent reduce it by putting pressure on the side walls, I took the approach of adding mass to both the side walls & also the rear of the cabinet where the sound pressure is likely to be at it's greatest................where the 15 inch woofer pushes that huge amount of air out into the rest of the cabinet.....................I did this by adding another layer of 18mm ply to both sides & the rear with constrained layer damping of "Green Glue" between the panels & about 50 screws to hold each panel.......................................then the complete cabinet was totally re veneered again to preserve the finish ( a real pain to do....but worth it).................................and the result?.....................I couldn't be more pleased....................maybe I was lucky, but this has transformes the sound of these bass bins............the bottom end is soooo clean & powerful ........and the resonance? ........completely gone......................has it shifted to a higher frequency?............don't know, don't care..........they just sound soooo good now.

Those cabinets remind me of a set of Altec Model 19's that I once had......beautiful work Dave.

That's merely a way of protecting your specification from the opposition!

Bruce, I used it successfully with SS amps & now have switched to a CJ valve set up...................it's still a night & day difference....................you won't be disappointed.................you may have to plug the ports though.

Say what!!!..................But good to know that my ears were on the right track.[]

Now to throw a cat among the pigeons......................Here's one for the techno heads out there to ponder over.................I've used the mod very successfully & have always used SS amps.........................I recently switched to a tube amp & found that the bottom end wasn't as tight or defined as before.................it was actually very soft .......................& merely put it down to the fact that the valve amp wasn't as tight in the bottom end as the SS amp...............it was sort of boomy & muddy & a lot lower in level..................so I thought I'd plug the ports up & see if it made any difference..................now it sounds just fine, as tight as always & punchiness is back................without the ability to measure, my assumption is that the ported version is amplifying some frequencies that the valve amp is producing that were perhaps not there in the SS amp?????

I concur........in comparison with other speakers you'll find that it goes easily down into the low 30's. I still use a sub though, to round out the bottom end.

Hi Arash, Yes, those are my babies & to answer your question......I doubt whether you'll hear any difference in efficiency....I certainly didn't. Maybe if you measured there might be a difference, but not enough to be able to hear it. Once you've heard this mod you'll never go back to the standard setup again, it totally changes the sound of the LS. Don't forget to reinforce the side panels to remove the resonances. Mine have an extra 18mm layer on both sides, as well as the back, as well as the braces. This too changes the sound so much for the better. Good luck, John

Yes, I hear what you are saying......I already have an ALK uni, so I want to sell that & make this new crossover up. So if I was to remove the low frequency section it should be OK? Remove fuse from input low , through to inductor & remove inductor & wire from barrier block woofer +, remove 39 & 1 uf capacitors & wire going to input high & Bi amp input........then connect the AP12-500 from the mid out to the bi amp in & the input high on the uni (after removing the strap on the AP12..........Quote from ALK - "The network will operate in a 2-way system using the autotransformer to equalize the level to a wide range driver such as the Altec 902-8 with the woofer using the 2-way strap. By removing the 2-way strap an external crossover can be connected to transition between a squawker such as the Klipsch K55V or K55M and a tweeter in a three-way system. The squawker can utilize the same autotransformer. Three-way operation is recommended as not many drivers will operate safely from 500 Hz up." end quote............... .if this is going to work, do I put the transformer to attenuate the mids on the AP12 or the uni? Thanks, John

Thanks Speakerfritz........yes, found that diagram too, but I don't want to build the whole uni network, just the required part to go with the AP12-500.

Can someone help me with the above combination?................I'd like to construct an AP12-500 & use the high frequency section from the uni.............I've looked on Al's site & found the following.........ES to Uni connection.........ES to ES connection..........& ES to Uni connection.........But no AP12 to Uni connection....................yes, I know the AP12 is a direct alternative for the ES, but there seems to be 3 wire connections, bi amp connections, etc....................on his site it says not to use the transformer on the ES500 when you connect it to the uni, yet somewhere else it says to use the tranny on the AP12 when connecting to the uni............................. What I really need, if someone has the time & patience, is a diagram like the one attached,showing which part of the uni fits in to the AP12........ I don't really need it to be in 2 seperate sections (it could all be on the one board) & I don't really need it to be bi-wireable or convertible from 2 way to 3 way........just the basic AP12-500 with the Uni top end...........................I've looked at all the schematics but I'm not able to transfer that into a workable project...................if I had a diagram like the one attached & with the pictures on ALK's site I could construct it OK..........thanks for any assistance......John

The HF section would certainly work, but the woofers in parallel poses a problem. The Impednece and inductance have both changed. What woofers are you using? Dave Crites cast frame woofers

Dave, Can this be used for the Cornscala DBB or be adjusted to suit? Thanks, John

Yes, you'll have to prise the JBL label on the back off. They are usually just glued on & if you carefully prise it off you will be able to re attach it. When this is removed you will see the bolt ......undo this.......& you'll be able to get inside to see what has to be done.....be very, very, very careful of the diaphragm!

Fantastic......please let me know your thoughts. I've often tried listening to the LS without the BR extension, but it only lasts for about 5 minutes.....just isn't the same.

Any opinions?

I'm going to change from La Scala cabs to Belle bass bins & want to maintain the bass reflex mod to extend the bottom end. Does anyone see any potential issues with this? I figure it should be the same result with the Belle bins, but just checking. Thanks, [] John

and bracing of the cabs.......no room for a 2404 here.

and with crossovers

Wow, looks like it would surely get ones attention. Looks like John left some room for the Tweeter in between the two JBL 2123J's, I wonder if it was intened to be mounted in the top cab. Like this

Thanks Speakerfritz, This was my gut feeling after researching the Belle.....should be better in the mid bass & also smoother sounding. I guess I'll have to put a set together & try them side by side & see which I prefer. That can be my next project, as at the moment I'm working on a set of tractrix timber horns which will be fitted with GPA 390 drivers.....should be interesting. Thanks for the opinion on the sound difference....just what I was looking for, John