From: moskowit@panix.com (Len Moskowitz)
Subject: Re: The great speaker debate: 15 vs 18
Organization: Panix Public Access Internet & Unix, NYC
Date: Fri, 22 Jan 1993 14:19:25 GMT

Pete Turner writes:

>The question is, what does (or doesn't) an extra 3 inches buy you over
>the 15? Better boom? Some better response? Less chances of launching a
>cone through the front row at your next gig? What?

First my background: I've been playing bass for 26 years and have played
through every combination of speakers you'd ever imagine.  I had an
Acoustic 370 with the huge 1-18" folded horn cabinet; a Road 1-18"
cabinet that was about as small as you can make a 1-18"; a few 1-15"
cabinets with a variety of speakers (EVM-15B, Utah, and others); a 2-15"
Ampeg cabinet; multiple late-60's (small) Bassman 2-12" cabinets; and
others too.  I'm also an electrical engineer who finds pleasure in
designing my own cabinets.  I've had an article in Speaker Builder and
am current with modern driver selection and cabinet design practices.  I
also build and sell some unique binaural microphones under the trade
name "Core Sound."

My opinion is that every speaker system trades off different performance
features.  My latest project is a 1-10" with a midrange dome-horn and 24
dB/octave acoustic slopes, all stuffed into a 1.5 cubic foot (small!)
fourth order (ported) box.  What motivated me was what you referred to
as the "shlep factor" -- I wanted something light.  But I didn't want to
compromise flatness or deep bass.  This new bottom rolls off to -3 dB at
35 Hertz and is reasonably flat up to roughly 7 kHz.  It'll easily
handle the low B on a 5-string.  It can put out 112 dB sound pressure
levels and handle more than 200 Watts.  That's not as loud as some
speakers, but none can beat it for depth and flatness.  If I want to go
louder I add more cabinets.

To get this performance I had to carefully select drivers that could
give this kind of performance in such a small enclosure.  Most 10's
couldn't get anywhere close to 35 Hertz -- most were up in the 60's and
that includes SWR and Eden and other commonly known musical instrument
drivers.

Back to the immediate topic:

The typical 15" driver in a three or four cubic foot box is going to
have a large peak in the mid-bass.  (Did you see Ralph Gonzalez's post
on this a week or two ago?)  That'll make it sound very loud and
impressive but it won't sound balanced.  It'll also have very poor low
bass response -- usually not lower than 60 Hz or so.  An 18" in that
size box will be even peakier and won't go as low!  Now it could be that
you like the peaky sound, and then I'd say: go buy it!  It's also true
that if the driver has sufficient power handling and enough linear
excursion, you can equalize the crap out of it to get low bass.  That
implies a very expensive driver (say a McCauley -- and that's big
bucks).  But otherwise, when you go from a 15" to an 18" driver without
changing the size of the box, all you typically get is *less* bass and
more peakiness.  That's what my old Road 1-18" cabinet sounded like.  An
EVM-15B in the same sized cabinet gave deeper bass and less peakiness.

That's not to say that an 18" driver won't get you a deeper bottom *if*
you use an appropriately large cabinet, but if you're interested in
small size and low weight, large cabinets are not what you're looking
for.  My old Acoustic 370 cabinet was the size of a medium sized
refrigerator.  It had its own hand cart built in and weighed close to
150 pounds.  Yeah, it went low and loud but I'd never go back to it!

My advice: If you like the 15" sound, use a 15".  Stay away from 18's
unless you can manage a big cabinet or you specifically want a very
peaky, weak bass sound.  If you want light weight, compactness, flatness
and deep bass, get a well designed 12" or 10" cabinet.  You can get away
with up to 2-12" (or 10") drivers in a reasonably small sized box.  Any
more than that and you start compromising deep bass extension.  Even
Eden notes that their 210T (2-10" woofers and a horn tweeter) goes
deeper than their 410T.  Their 110T goes a bit deeper yet.  And Eden
hasn't really managed to extract the deepest bass from the 10" drivers
yet.  As I've shown in my latest project, you could do much better if
you're willing to bite the bullet a little on efficiency.

Don't get caught up in the "if 15-inch is good then 18-inch must be
better" thing.  It's just not so except for someone who's more
interested in appearances than sound.

Hope this helped.

-- 
Len Moskowitz
moskowit@panix.com
Newsgroups: rec.music.makers.bass