21w/8554 owners please help

recently changed my 2 way scanspeak 21W/8554 and 2905/9700 combo from a 60 L vented enclosure to a 20 L sealed one.

they are comparably well braced, although the new sealed one is veneer LDF, and the vented was all MDF

external crossover unchanged, pseudo 1st order about 3k.

2 problems:

1. the woofer seems to scream in the midrange, which was previously not a problem

2. the bass is not as tight as i'd hoped with a sealed design.

any feedback on box size, damping etc.?
I'm using 8 Scanspeak 21w/8554's in a line array (4-per side). I mounted them in .80 cu foot sealed boxes from Parts Express. I've paired that with a Bohlender Graebner RD40. These are great 8" drivers with a nice warm midrange. I've had them crossed over as high as 800 hz and now at 400 hz.

I've heard Kevlar just rings at 3khz. These 8554 drivers have a slight bump in frequency response at 800 hz and another small hump at 1200 hz. Those I can live with sonically without EQ'ing out. I personally wouldnt run it in a 2-way above 2000 hz.

I am wondering if I wouldnt have been wiser to use the "revelator" doped paper cone woofers from Scanspeak. Or possibly the magnesium/aluminum drivers from Seas.
Two observations

Firstly, the 21W/8554 is not really suited to sealed box use, and hence it's lightweight bass will make the 3kHz rise that much more audible.

Secondly, the 21W drivers are woofers and not midwoofers. I wouldn't run them much above 1kHz, and most certainly not in a 2-way system.

The 21W/8554 was apparently used in the Phoenix dipole. You can read about that at http://www.linkwitzlab.com/x-mid_dist.htm. I have heard this driver operating dipole in a large open-back box and am guessing that the Phoenix sounds good.

I've read that a 22L sealed box should produce bass output downto F3 78hz. Im fairly happy with the drivers sound quality and output in a range from 90 to 1100 hz in this size sealed box.

But like you I've found out through experimentation that it just works better in a large IB or vented box. How does one know that before committing to the expense of building the box though?

I just thought of bumping this 5 yr old thread =)
The 21W is best suited in a small vented box. The low Qts suggests no larger than 40L vented. I have mine in a 35L vented enclosure crossed at 2Khz to a D2904 7100. Very musical although I am very much going against the laws of speaker theory. 25Hz is very much audible and this woofer plumbs the depths, obviously with less authority than say; a peerless XXLS 12''.

My current system is a 2 way MTM with the 8'' kevlar driver and the midrange is extremely good. Just as transparent as my other 6'' kevlar + D2904 7100.

I yearned for a 2 way that could deliver powerful, articulate bass, yet with a midrange that is of acceptable quality. Top end is fantastic with the Scanspeak D2904.

20L closed box for the 8'' will deliver terrible results. Pls do not build one =S