Posted by Lew on April 09, 2003 at 14:51:56:
In Reply to: Re: Re: Re: M-2 and MA-1MKII.2's posted by Brian Walsh on April 07, 2003 at 19:02:32:
I have no doubt that the U1 is the flagship of the Sound Lab line of speakers, and deservedly so. Primarily, the rigid metal frame is likely to have a firmer grip on the panel, resulting in a few Hz of extended low bass response and perhaps in better low- and mid-bass definition. The trade-off is that the hollow steel tubes resonate and could give a slight coloration to the all-important midrange. I am sure most serious users will add dampening material to the tubes, which is likely to be either sand or lead shot. I would like to point out that this will merely alter the resonance frequency and will not eliminate resonance. The M1s on the other hand have a minimal support structure for the radiating panel. This can result in a slight reduction of low end extension and in some loss of midbass definition on transients, but the M1 can be stiffened in various ways without adding hollow steel tubes, which I believe were a less than perfect way to stiffen the U1. I definitely heard the effect of the tubing on the sound of my previous pair of U2s. After several thought experiments in which I ruled out the use of sand or lead, for reasons alluded to above, I settled on hardwood dowels, purchased at a local lumber yard. I selected a size that would fit very tightly into the hollow tubes flanking the panel (after I applied some rubber tubing to the circumference of each dowel) and which filled the tubes from top to bottom. This had the effect both of stiffening the overall support structure and of reducing the amplitude of any remaining resonance. Made a noticeable difference in the neutrality of the sound of the speaker.