I acquired VSM-MXs with a balanced BBAM bass equalizer in
the mid-2000’s. Over the years, I substituted
better piece parts in the crossover, wiring, and BBAM(adding a LPS), somewhat
along the lines of Bobby’s evolutionary path.
I eventually found what I was looking for in a two-way design that, in addition
to other virtues, has perhaps the most extended LF of any compact two-way employing a small mid/woofer. My only
complaint is that the signature of the VSM mid/woofer is a little dark, and the speaker is dynamically limited at higher SPLs or if placed in too large a room. Such is life, one might expect, with a 6.5” driver
called on to cover a wide frequency range from around 30hz to the 2200hz
crossover point. Also, while the front port adds warmth and useful
LF extension(with port effect to below 30hz), this woofer arrangement is not the
last word in delineation of LF.
Recent reviews and DIY forum threads on the new Purifi PTT6.5W04-01A mid/woofer were intriguing enough for me to try replacing the stock VSM Scanspeak 8545-01 mid/woofer with the Purifi. For a 6.5” cone driver, the Purifi has unprecedented low IM distortion across a wide frequency range, good low frequency extension, and handles relatively high SPLs without strain. This suggested good synergy with the +5db bass boost added by the BBAM. Purifi’s sensitivity, frequency curve, and recommended cabinet volume are quite close to the 8545 and the VSM cabinet. I purchased the 4ohm version. Purifi has since released an 8ohm version that may more closely match the 8545’s impedance.
One small challenge in the swap is to drill new screw holes at other points on a circumference that is 1-2mm smaller than the Scanspeak. I went one size up from Merlin’s stock screws, with a stainless steel boating screw that tightens with a square bit. The small diameter stock wood screws tend to loosen over time. If over-tightened or removed and replaced several times, they can strip the MDF.
The improvement over the 8545 is immediate and increases with break-in(now out to 50 hours.) The Purifi blends well with the stock Esotar silk dome tweeter and crossover point. Purifi is cleaner and more resolving than the 8545 across the frequency range, images a better soundstage, and is more dynamic. The performance is simply more revealing and exciting. With the BBAM boost there is ample LF output and extension. Stuffing the port tightens the bass and brings it into a better balance. You will almost forget it’s a 6.5” driver. At around $700 the pair it’s not cheap. But this a meaningful upgrade that extends the life of the VSM.