What is the right replacement tweeter for my passive nearfield monitors?

February 28, 2011 6:15 PM

Passive nearfield monitor speaker repair filter. I need to replace a blown tweeter. I know the kind of tweeter but it's no longer manufactured and I need to select a compatible alternative. Please help.

I have a pair of secondhand HHB Circle 3 passive nearfield monitors; nothing fancy. They come with Audax TM025F1 tweeters, one of which is blown. It seems the tweeters aren't being made any more, but they're a standard size and fit and I could in principle replace the blown tweeter -- more likely both -- at reasonable cost, but I'm not totally sure of the details.

This discussion mentions some possible candidate replacements for these tweeters. Do I need to know more than this to make the right choice?

I'm not massively concerned about ideal matching that a pro mastering engineer would care about. Except I plan to get two tweeters so I'm using the same brand in each speaker, even though only one is blown, and it seems intuitively right not to upgrade the quality of the tweeters much or at all.

While I know I can get the tweeter out and connect the internal terminals to something else, I don't know if there might be problems with matching a particular replacement tweeter choice to internal bits I haven't looked at, like crossovers.

Thanks for any advice.

posted by galaksit to Technology (3 answers total)

Once you start replacing transducers in older multi-driver speakers with non-exact modern replacements, you're in for a lot of testing/crossover and impedance matching redesign, without any surety you'll get a "better" final result than you had originally, or even if you'll get as "good" a final result as you once had. The material improvements of the last 30 years, have barely kept pace with the claims such improvements have generated, much less with the proliferation of theories about how such basic devices as cone and dome audio transducers actually function. In general, magnetic material have become more permeable and cost effective in the last 3 decades, than they were in the 60s and 70s; this has led to more efficient drivers, especially tweeters, than were available in that era. The average gain has been about +3 db, and because of better cone/dome material formations, we've seen far higher instantaneous power handling, without major breakup, in today's dome tweeters, than we have in eras past.

That said, you might consider Goldwood GT-520 1" SoftDome horn loaded tweeters, as a replacement, or the Morel CAT 378 1 & 1/8" horn tweeters. The "horn" included in either of these designs is miniscule, for frequencies below perhaps 5 KHz. Much more than beaming due to horn loading, you'll need to think about efficiency matching to your existing transducers; mostly, that will be an exercise in selecting a carbon resistor and perhaps other passive components, that roll off your new tweeter response in approximate eveness, with your older drivers.
posted by paulsc at 7:36 PM on February 28, 2011

Response by poster: Thanks for your answer. Some of that is over my head, but are you suggesting that this cannot be done satisfactorily in a "plug and play" way? My electronics skills are fairly budding at this point. I might be interested longer term in actually working on the internals but for now I was thinking of just popping in something that basically works and remains in a rough zone of acceptability for monitoring. The speakers are from ~1999 and the tweeters were available until just a few years ago.
posted by galaksit at 9:08 AM on March 1, 2011

Response by poster: In fact the Goldwoods are too big for the enclosure. They aren't a replacement for the Audaxes, unfortunately.
posted by galaksit at 1:23 PM on March 11, 2011