[woodsyi]

I have just finished taking apart a pair of RM40's and thought to share a few observations and have a few questions (more like pondering).

There is a boatload of insulation stuffed in the woofer chamber.  I am ignorant on this matter so here is a question.  In the sealed chamber with a passive radiator as the only "port" what does the stuffing do?  What would happen if the cavity was left empty or filled with some other material?

The bare cabinet is darned heavy.  I cringe at the fact the new MLS cabinets will be heavier.  I mean for moving the stuff into the basement.  I am sure the "denser" MDF will help with the inertness of the cabinet.  I wonder if MLS cabinets will still benefit from additional bracing.  Shouldn't  "MLS-Dorn Super Cabinets" be used in BCSE speakers?

The wires for the ribbons are so much thinner than those for the woofers.  Is this a cost/benefit trade off, logistic necessity (small space) or that high frequency signals don't benefit from thicker guage?

Some have complained about "amateurish soldering" but I like it.  I am assuming that "amateurish" means there are "healthy dose" of solder over each solder point -- like the way I glued my floor where the dastardly stuff was still woozing out weeks later!

What am I going to do with a pair of cabinets?  Should I buy some woofers and make them into The Taller Subwoofer?

[JoshK]

I think taller subwoofers would be a great idea, or maybe even an array of woofer drivers like old-Infinity era cabinets.  Tuning is going to be tricky but its doable I'd think.

[Tyson]

I'll take a shot at the stuffing question - stuffing does 2 things, it absorbs backwave, reducing "echo" in the cabinet, and it makes the internal volume "appear" bigger to the woofers.

[meilankev]

Woodsyi,

If the MLS cabinets are heavier, I agree it would be a chore getting them up/down stairs.  My Listening Room is upstairs, and the staicase takes a 90 degree turn halfway up.  For me to get my RM40s into this room, it took me hadling a furniture dolly plus two extra people pushing from below.

If I ever move, I might just leave the speakers with the buyer...

Kevin

[James Romeyn]

Stuffing converts the sound waves into heat, which damps & slows the interior bouncing of the waves.  Yes, it has an effect similar to increasing the cabinet volume.  But the coefficient of absorption of fiberglass insulation in the audio range is quite non-linear, reflecting negatively on performance.  This is why polyester, with more linearity, sounds better.  When I used to build speakers my favorite was to line the inner walls with 1/4" thick brown utility (wall) cork & tune the system for no stuffing.

Transient impact & speed is audibly increased when the foam gasket tape on the drivers is replaced with clear silicone sealant, eliminating the spring effect of the foam, which damps transients.  The silicone makes service a total hassle, so consider that, otherwise all systems go.

[Brian Cheney]

Fiberglass is the damping material of choice for speaker cabinets.  It is difficult to deal with.  Absorption spectra for fiberglass vs various materials including dacron and various fibers recently appeared on the Audioasylum speaker forum, do a search there.

Fiberglass is the only material reactive enough to provide lowbass damping.

[Sedona Sky Sound]

Since no-one has answered the wire question yet, I guess it is my turn to chime in. As a general rule for most speakers, the mids/tweeter need much less current than the bass (60%+ of the current goes to the bass in some speakers). The bass on VMPS speakers are particularly hard to drive effectively and definitely benefit from a larger wire (lower resistance). However, my experience is that larger wires tend to attenuate higher frequencies (keeping the geometry of the wire the same). For the bass wires, the attenuation of the higher frequencies is a non-issue (and potentially beneficial) and is more than compensated sonically by the ability to carry more current (which can be much higher than you realize during bass transients).

Therefore, you want to provide the smallest wire you can for the tweeter/mids that still provides minimal resistance to the expected current for that driver. I am a very firm believer in bi-wiring using different size wires for the mids/tweeter and bass. In the ScorpionWire cables I make, I use roughly a 14 AWG wire for the mids/treble and a roughly 10 AWG wire for the bass. I have tried many other configurations but this is the combo that seems to work best both for the RM40 and the RM/X. Of course, this subject is highly debatable (as are most things in audio) and every "expert" has their own opinion. As I always tell my customers, "Let your ears decide for themselves".            

Julian
www.sedonaskysound.com

[woodsyi]

Thank you gentlemen for sharing your knowledge.  I think I am going to ask the wiring to be upgraded as well.  Since it's such a PITA to service a pair of RM 40's at the factory --especially if you live in the East Coast-- I think it makes sense to get ALL the upgrade you can get while they are there.  MLS, TRT, FST, multilayer soundcoat, Analysis Wires -- what am I leaving out?  

Julian,  I gather then, based on your wire anlysis, that woofers on RM40 would be better served by thick copper cables than a thin silver/silvercoat cables.  Am I right?  Same with the Larger sub?  I am ruling out 6 awg pure silver for cost reasons.