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Re: [OM] OT--Speaker rebuild question

Subject: Re: [OM] OT--Speaker rebuild question
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Wed, 5 Feb 2014 10:22:22 -0600
> Yep, noticed that the previously somewhat harsh piezo super tweeters
> are no longer harsh at all. I bet they still are and I remember what
> that sounds like but can't discern that anymore. Suppose I "grew" into
> them.

There is nothing desirable about a piezo tweeter to me. I've been
around some studio monitors that used them and the only thing that
could make them bearable were either earplugs or a square of TP
hanging over them. (TP is the sound-engineer's friend. Give me a roll
of gaffers tape and a roll of TP and I can rule the world--Nothing
fixes a rattling or buzzing instrument quite like a wad of TP and
tape).


> Speaker guy there is Larry Greenberg. I recall he helped me with
> something 10 years ago. He is quite the curmudgeon, though I didn't
> have any trouble with him. Place is a hole in the wall but he is
> competent.

I think you just described the best possible shop to have them
rebuilt. Be prepared to have your carefully selected and highly prized
speakers absolutely shredded by his opinion of them. My only grouse
with a lot of these guys is that they are total perfectionists and
will have the cross-overs tuned perfectly. Not only that, but the
speakers will be as close to flat as can be. Unfortunately, in nine
out of ten cases, you'll not like the results because you actually
prefer a little colorization of the sound. These guys (I've only known
a couple of female audio nerds and one is mostly deaf--she almost made
me deaf when I comixed with her and she had the studio monitors set to
ear-bleed sound levels), these guys will set up the speakers in a way
that do not actually help certain sounds. What most people don't
realize is that when the album is produced, it is produced with
speakers that have a little bit of sound colorization and the
expectation is that the listener will have speakers with similar sound
colorization.


> Can I expect the caps in the crossover to last anoher 10 years and the
> woofers to perform? I know if it were an OM, I'd be told to send it to
> John
> for a CLA. The parts are available. I was hoping AG with his
> engineering and audio experience would give you a +1 to leave it be, or
> -1 at least to render another brief opinion.

The caps in the crossover should be just fine as long as the speakers
have seen regular use. Non-use speakers will suffer severe degradation
in less than five years. Unless the crossover is of very very high end
design, I would probably go with a new one built by someone who knows
his stuff. Theoretically, a properly used speaker should never need
the crossover maintained or replaced, but I think that 20 years is
where you need to seriously consider a major overhaul. If nothing
else, the interior sound insulation and batting could stand some
attention and the box screwed and glued some more. Oh, one thing which
will absolutely require the overhaul is if the crossovers were built
using lead-free or low-lead solder. That stuff has been growing hair.
Audio components like this NEEDS leaded solder. If ANY hair is on it,
it needs to be rebuilt. Period. No exceptions.

However, at 20 years, not only does the crossover need an overhaul,
but everything about the speakers could stand some attention. If I
really liked the speakers, I'd be tempted to do some reengineering of
a few things on the interior and maybe even convert it to a portless
design. But I'm weird because I prefer a tuned chamber design (like
Fernando's speakers) as it keeps the speaker cone diameter down and
off-axis distortion low. I REALLY dislike multiple cones mounted in a
big flat faceplate. Almost without exception, those speakers give me
the willies as time-coherence is pretty well lost unless you are
within 5 degrees of on-axis. I'm good with frequency response losses,
but I'm NOT good with time-smear. I'm one of those freaks of nature
that can hear the time smear from an AKG C414 microphone. It's like
MPEG compression, once you can hear the turds spinning, nothing is
ever the same again.

I've always been tempted to build my own speakers. I am pretty sure
that I could build a world-class pair for about $2000 in materials
that would be time-coherent on and off axis to about 45 degrees as
well as being flat response down to about 40 Hertz without artificial
means and without needing to be the size of a fridge. Fernando's are
VERY close to what I would do, but with a few twists. "Only 25 Hertz"
you ask? I said FLAT. Below 40 Hertz, you are into room acoustic
issues and few rooms can actually handle anything below that point.
Besides, flat at 40 means down 9 at 20. (give or take, depending on
cabinet design). As I would use a tuned-chamber design, the drop off
occurs acoustically within the cabinet and doesn't require a high-pass
filter. Avoid electronics whenever possible. With an adjustable tuning
chamber, you can completely alter the cut-off point across an octave
range. With luck, you can probably avoid bass traps in the room.


-- 
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
-- 
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