Hi there,

Have recently bought and re-foamed some CX 50s (6 in total).  When I opened them up to take out the drivers, I noticed that the cabinets were filled with some kind of lagging or insulation (see photo); behind both the mid/range driver and tweeter.  Is this the previous owner messing about, or is this original?  Has anyone got a photo of what the inside of a CX 50 should look like?

To be honest, they did sound a very quiet, light and tinny (although extremely clear) even when I was pushing them hard and I'm wondering whether someone put the insulation in to deaden the bass.  I have taken the insulation out of one of them and they (unsurprisingly) sound a lot louder and much fuller, if not a bit too bassy.  Was there a middle ground initially?

Any comments welcomed.

Nick

 

 

 

That insulation is definately original, the same is used for almost all other Beovox speakers from the period. The CX speakers were probably meant for use with a Beovox Cona subwoofer in the first place, thei design is naturally as bass-lacking

Thanks.  I'd better put the insulation back in then...and get a sub.

If they have just been refoamed they will "loosen up" with use. I found that my CX50's sounded very base light at first but sounded a lot better after a few weeks. Give them a bit of time and put the fluffy stuff back in.

I'm still not 100% sure that the lagging is original as no-one else confirmed that they have seen it in CX 50s they have refurbed.  I just think they sound a lot better without it...

 

That filling is very typical B&O-style, here seen in a Beovox S75

Thanks.  I take the point.  My issue is that the entire cabinet of the CX 50s is essentially full with the stuff, whereas any photos of refurbs I have seen the cabinets are empty.  It literally soaks up all the bass as there's no room for any movement behind the bass driver. 

I can see that it looks like the right stuff, but it just doesn't feel right and wondered if anyone had encountered it specifically in CX 50s before.

Thanks

Nick

It doesn't "soak up the bass" it improves it. In a sealed enclosure the fiber fill acts to reduce the speed of sound in the cabinet, making the driver think the cabinet is larger than it actually is. It's used to tune system Qtc to extend LF response and improve damping.

Removing it will increase system Qtc, which means a higher LF cutoff, and often a peakier upper bass with a large peak in response with degraded damping. Some people mistake this for "more" bass, but it's at the expense of extension and damping.

That looks exactly like the stuff that was in my CX50's. I usually use polyfill in my designs but this is what I'd expect for a European speaker of this vintage.

Yes, definitely it takes a couple of hundred hours after a refoam (or after a crossover recap) for the sound to sparkle as it should.

It can be disappointing when first listening after doing the work, but just a little patience is needed.

Menahem

Nick:

Thanks.  I take the point.  My issue is that the entire cabinet of the CX 50s is essentially full with the stuff, whereas any photos of refurbs I have seen the cabinets are empty.  It literally soaks up all the bass as there's no room for any movement behind the bass driver. 

I can see that it looks like the right stuff, but it just doesn't feel right and wondered if anyone had encountered it specifically in CX 50s before.

Thanks

Nick

My CX 50s were as you described.  Nearly full of the stuff.  Just like my second pair of M70s.

With both pairs of M70s, my S45-2s, and my S40s, I discarded the B&O damping material and replaced with different material.  (I hate that B&O stuff.  With a passion.)  With my CX 50s, I left the B&O damping material as is.  (The description of my CX 50 refurb is buried within the long thread about refurbing my M70s.)

My advice is to experiment and let your ears decide what is best.  But I'm a tweaker; "original" doesn't matter to me much.

 

Yes, my CX50 have the same fill material and it took several weeks of playing the speakers for a few hours a day for the bass to sound full. It's just the required break in time for the new foam. The same thing happened with my C75s, but the break in time seemed much shorter for them.

My CX 50's are exactly the same inside.  I'll also echo what others have said re: loosening up after the refoam.

My 3702 has the same awful stuff inside, and as Rich I dont like it, will run a test with another fiber material.