dbg (11/23/82)
There have been a number of inquiries regarding buying
systems. I have some suggestions that a few of you may be
interested in trying, but first let me get a few things
out of the way.
If you have looked at moderate to low cost systems
(under $1200), you have probably concluded that there
is little difference in the electronics. It is generally
agreed that the critical components in the chain are
those performing the mechanical coupling. In a low
cost system we can narrow these down to the cartridge
and the speakers (ie transforming the groove information
into an electrical signal, AND transforming the electrical
signal into sound waves).
I have many times seen the advice that half of the amount
to be spent on a system should be spent just on the speakers
and the other half on all the rest. But what about those
records that you're going to buy monthly, weekly, dayly?
That's where a lot of your money is going to be spent.
If you own 200 albums at a replacement cost of say $8 each,
then .......
Well, the point is, don't skimp on that turntable-tonearm-
cartridge combination. Once a record has been damaged
$10,000 worth of equipment will not restore the original sound.
If you want to save money, do it somewhere else.
That brings me to what I wanted to talk about originally --
designing and building your own speakers. That has been
a hobby (in college it was a lucrative and satisfying business)
of mine for years. You might be suprised at the results given
a little thought and preparation and guidance. Its a way
of saving money on that first system and a way of getting
involved in audio. If you run into difficulties, this newsgroup
seems to be a very good source of information. I currently
favor the subwoofer and full range satelites approach but
I have not experimented with it yet. I can probably recommend
parts for a reasonably good 10" two-way bass-reflex system though.
A. N. Theil
Thats NOT my name--just an inside joke I couldn't resist after
the bass-reflex comment.
ihldt!dbg
Dave Green
p.s. This computer science thing is just a living while I get ready
to get back to my real interest -- dbg Loudspeakers (among others)spj@spanky.UUCP (08/10/83)
Recently I decided to attempt to design and build a pair of speakers using commercially available components. I did a bit of research regarding crossovers and discovered what appears to be a controversy as to which passive crossover is best. Most sources cite the 6db per octave design as best due to desirable phase effects, but warn against its use in the general case because most drivers don't have sufficient bandwidth to handle the gentle crossover slope. Although Linkwitz has advocated even order all pass crossovers, and even provides design information for passive crossovers, Thiele warns against using them because the input impedance is not constant, apparently this would cause problems in cascading sections for a mid-range filter. Meanwhile, Linkwitz warns against using third order Butterworth filters because of a tilt in the polar response pattern. Can anyone out there help me sort this out? I am not an electrical engineer, so I don't expect my layman's analysis to be perfect. Also, can anyone recommend sources for drivers? I know about Speakerlab, but their prices seem kind of high.....
jeff@tesla.UUCP (Jeff Frey) (11/28/83)
I regard my old feeling that the law of diminishing returns in loudspeakers begins to apply immediately above the Large Advent loudspeaker (or whatever number they give it these days) as now verified, by having listened to a pair of KEF 105.2 and 104.2 loudspeakers. Naturally the listening conditions, etc., were not the same for the KEF/Advent comparison so purists may quiver but at least the signal sources were the same, several CDs with which I was familiar, including the Delos Tchaikovsky 5th, Canteloube Songs of the Auvergne (Kiri Te Kanawa), Schubert`s Trout Quintet, and a few others. The KEFs were driven by a Kyocera CD player and a Mark Levinson amplifier. I found them to have a marvelous presence in the mid and high ranges, but also to have a bass that was not too well defined. The mid/high performance of the KEFs is due to the small free-standing boxes those drivers are mounted in (among other things, of course) so when I got home I pulled my two-Advents-per-Channel out of the large bookcase they were in and stacked them (vertically) on one another, woofer-to-woofer. I also replaced the Radio Shack #256 gauge speaker wire they were wired up with with #14 twisted pair. The purpose of bringing the speakers out of the bookcase was to eliminate reflections from the surrounding planes, thus approximating this aspect of the KEFs. I did a little voltage-drop calculation on that RS wire and figured that exchanging it for something heavier might be a Good Thing, which would be reflected in a greater effective dynamic range. The tweeter on the lower Advent, by the way, is effectively out of business because it`s right on the floor and the speaker response is switched to "high cut". THe result of all this was a reduction of sibilance on the vocal material, a reduction of sound localization at the speakers, and somewhat greater bass clarity, which I ascribe to room dynamics. I`m glad I heard the KEFs, and was able to calibrate my own system against them. Four large Advents probably cost around $600 with discount today; the KEFs are $3200. I heard the KEFs at Gala Sound in Rochester, a place with an excellent selection of really top-quality equipment. Joe Gala really knows his stuff and doesn`t apply too much hype (although some is excusable when a $3000 sale is possible). The place is really worth a trip of a couple of hours (a three-star audio shop, as Michelin would rate it) if you are interested in comparing all the topmost-quality stuff in one location. Jef