[Folsom]

My best recommendation for those speakers is to remove the middle crossmember. I suspect not a soul will do it, but whatever.

[S Clark]

Why in the world would you remove the bracing? I can't imagine that you reduce bass boom by making the box more resonant?  ???? 

[Tyson]

What's a crossmember?

[opnly bafld]

Why in the world would you remove the bracing? I can't imagine that you reduce bass boom by making the box more resonant?  ???? 

IDK how effective it would be with 3/4" mdf, but with thin wall designs the idea is to move the resonances higher.

[Hobbsmeerkat]

The bass boominess is an odd issue to have, esp with the XLS.. they aren't a boomy or bass-heavy speaker, by any means.

It's likely to either be a room issue, or you're simply use to your old speakers having a rasied top end or weak bass, so matching the volume means the lower mids & bass will be more present, since the XLS is a rather balanced speaker.

I know others have mentioned reducing the stuffing if its too full.
But aside from that and the suggestions that others have made, im not sure there's much else that can be done or tried without more info...
A simple frequency response graph of one speaker at a time in your room from the listening position may help give us some more useful info to help you with your problem

[hawkeyejw]

The bass boominess is an odd issue to have, esp with the XLS.. they aren't a boomy or bass-heavy speaker, by any means.

It's likely to either be a room issue, or you're simply use to your old speakers having a rasied top end or weak bass, so matching the volume means the lower mids & bass will be more present, since the XLS is a rather balanced speaker.

I know others have mentioned reducing the stuffing if its too full.
But aside from that and the suggestions that others have made, im not sure there's much else that can be done or tried without more info...
A simple frequency response graph of one speaker at a time in your room from the listening position may help give us some more useful info to help you with your problem

This. It’s impossible for anyone to provide much help without knowing what response you’re actually getting from your speakers.

[Folsom]

Why in the world would you remove the bracing? I can't imagine that you reduce bass boom by making the box more resonant?  ???? 

Well then I guess you should build some heavier super braced and stuffed to the brim with polyfill cabinets for your Altecs.

For the X-LS encores as best as I can tell the brace gives an undesirable self resonance point that makes it sound meh.

[S Clark]

For the X-LS encores as best as I can tell the brace gives an undesirable self resonance point that makes it sound meh.

Is this speculation, or have you done this? 

[Folsom]

Is this speculation, or have you done this?

Done.