Tri-amping on the Cheap or reclaiming old equipment from the trash heap & polishing that turd into Gold, Baby, Gold!

[jeffca]

This isn't a revelation to me or a DIY article... just a bit of proselytizing.

 

Being a proud owner of Paradigm Reference Active LCR-450 mains and a pair of their Servo 15 subs as well as a Mackie SRM450 for a decade, the virtues of active loudspeakers aren't news to me.

 

But, after re-tasking some cheap pro audio gear and retro-fitting an old pair of Boston Acoustics T830's with new Scan-Speak woofers, I'm amazed at how fantastic some cheap, old crap can sound.

 

The rig is as follows:

 

• Boston Acoustics T830 speakers (circa 1988) with new Scan-Speak 22W/8534G Discovery 8" woofers

 

• 3 old Carvin power amps: two HT150 (mids/tweets - power chip amps circa 1998) and a DCA300 (discreet amp circa 1987)

 

• Behringer DCX2496 digital x-over

 

• Dayton 5-way terminals, Supra wiring and some cheap generic quick connects both gold plated & base metal

 

Currently, I'm in the process of voicing the speakers. It's a pretty arduous task involving hours of listening to music... how terrible.

 

While mid and high drivers could stand upgrading, I was shocked at the difference subbing out one of the HT150's for an old Adcom 535mkII made in the sound. While I hate to use thoroughly unscientific terms to describe audio, it's apt in this case... with the 535 hooked to the mids, this rig sang! It just wasn't me loving it. My partner in crime came over for a recording session and he was impressed as well.

 

I'm now very seriously considering the purchase of a used 535 from Ebay so I can have that goodness all of the time. These cheap Carvin chip amps are really only good for powering dipole surrounds or any other speaker where amp quality isn't critical. They're too noisy and just don't have what it takes to resolve real detail.

 

So, as it stands, the system's imaging is razor sharp as the mid/high on each channel on each speaker is powered with it's own amp and the bass response is amazing for a pair of 8" woofers. And, of course, bypassing the passive X-O improves efficiency by several db's and decreases amp and speaker distortion/nonlinearities by about an order of magnitude due to the elimination of some really old, reactive elements from the signal chain. Capacitors age like vinegar, not fine red wine.

 

As I listen to two vocal titans of last century, James Brown and Robert Palmer, tear through a live rendition of JB's I Got You (I Feel Good), I'm loving life!

 

So, what other cheap improvements could be made? Both Dayton and Morel offer 2" dome mids that are direct replacements (flange size-wise) for the BA mid driver. The Dayton is actually a pretty good transducer, but most likely won't be able to keep up with the Morel in almost any aspect. The Dayton's also an aluminum dome while the Morel's treated fabric. The price differential is $100 and change ($40 vs. $144) so I'll probably do the Dayton and, maybe later, go for the Morel.

 

Also, I could replace the tweeters with Vifa XT19TD00-04 3/4" Ring Radiators. With a little cajoling, I think they could fit perfectly into the BA tweeter flanges (they're an odd size that no one else, including BA, now uses).

 

Is this something you should do without any experience, techinical/scientific expertise and a bunch of cheap equipment lying around? Probably not. But if you have an adventurous spirit, a decent understanding of basic loudspeaker design and some cheap equipment gathering dust, go for it! You can make some old speaker useful again.

 

You will be happy that you did. Trust me.

 

jeff