diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Swap Meet (http://www.diyaudio.com/forums/swap-meet/)
-   -   Eminence SW40128 Audio History (http://www.diyaudio.com/forums/swap-meet/114447-eminence-sw40128-audio-history.html)

gpsmithii 29th December 2007 02:01 PM

Eminence SW40128 Audio History
 
Own a piece of Audio history. I believe this driver was the center piece of an article from an old Audio magazine PASSIVE sub-woofer article. I purchased it and never got around to building the project. I can't find any specs to build the box, but as I recall it was to be around 1^3' sealed. I still have the crossover for the woofer and the caps for the 6db feed to the satellites. I know there where a couple of comercial offerings based on this article. Make me an offer as I hate to just throw it away.:smash:

Robert1954 15th September 2010 06:11 PM

Hi, Don't know if you still have this driver or any questions about it. Pretty sure I'm the author of the article you're referring to. I wrote it for Digital Audio magazine in 1985. Very surprised to learn that there were commercial products based on it. I'd be curious to know which ones ..??

... but regardless, I can answer questions about this driver. I currently own 7 of them and am in process of securing the best possible surrounds to re-foam them. Don't know why Eminence stopped making them, as they are the best affordable acoustic suspension woofers I've ever run across.

gpsmithii 28th September 2010 11:34 AM

Quote:

Originally Posted by Robert1954 (Post 2304174)
Hi, Don't know if you still have this driver or any questions about it. Pretty sure I'm the author of the article you're referring to. I wrote it for Digital Audio magazine in 1985. Very surprised to learn that there were commercial products based on it. I'd be curious to know which ones ..??

... but regardless, I can answer questions about this driver. I currently own 7 of them and am in process of securing the best possible surrounds to re-foam them. Don't know why Eminence stopped making them, as they are the best affordable acoustic suspension woofers I've ever run across.

WOW! Do you still have the article? T/S parameters?

Robert1954 12th October 2010 04:28 AM

I still have the article, but it's tucked away in my attic/crawlspace, and with recent shoulder surgery, I probably can't get to it for another month.

The T/S parameters were as follows: Fs=15Hz, Qts=0.48, Vas= 15 ft³. I had one with an Fs of 13.5Hz after quite a bit of use.

These are killer parameters for a sealed box. In 5 cubic feet you get about -6db at 20Hz. In 10 cubic feet, it's about -3dB at 20Hz... both with the slow roll-off of an acoustic suspension system. No EQ, no bass boost, no trick tuning needed... just a sealed box and a woofer. Kind of like a giant AR1/AR3. Dual voice coils, too.

Once I get my health back together I am going to refoam the rest of the ones I have.

EDIT: These Eminence drivers were sold by McGee Radio under their part number SW40128. The actual Eminence part number is 12424-1. They were available with square 40oz magnets (earlier) and round 40oz magnets later on. Both versions seem to operate the same (which is very good).

rkaudio 2nd February 2011 04:11 AM

Greetings Robert1954
 
I built the subwoofer described in your article almost 20 years ago. In fact, I recovered it from my basement where it sat silent for the last 10 years just last week. I enjoyed using it for a few more days before the foam surround finally gave out in a somewhat dramatic fashion! I guess you've had the same experience?

I found this thread while looking for a replacement driver, or at least a new model that could work in the same sealed enclosure volume. Unfortunately most modern 12" drivers have a higher Fr and a much lower Vas, better suited to a ported design. Ever find a way to replace the surrounds?

By the way, I actually have a photocopy of your article from "Digital Audio" magazine (January 1985) sitting in front of me as I write this. I can't believe I still have it! I though you'd like to know.

Robert1954 28th June 2011 04:47 AM

I now have 8 of these and every one had the foam rotted out. I am starting to re-foam them - problem was finding foam compliant enough to maintain the low resonant frequency. I "simply" bought foams from about 6 different vendors until I found one that was pretty flexible. The last one I rebuilt has an Fs of 14.4Hz.

I know Fs isn't the only thing that matters, but for a sealed design where you want to good very low frequency response, it's pretty important... that plus a moderately high Qt. This combination usually comes with an enormous Vas, but there's no "free lunch."

I'm thinking about building a pair of 5 cu ft isobarik sub-woofers. With the right tuning (duct length and diameter) they'd be down less than a dB at 20 Hz. I'm new to isobarik enclosures so want to do more research before building these.

My shoulder has healed enough for me to make it into my crawlspace, just haven't gotten around to it yet.

Cool that my article is still floating around :) Those pic were taken inside the house I was renting at the time. The woofer in the article is the one that measured Fs = 13.5Hz. That one is up next for re-foaming.

_henry_ 28th June 2011 05:15 AM

WOW fs=14hz?????

rkaudio, would u mind upload the article? love to see them.

cheers
henry

Robert1954 28th June 2011 04:41 PM

I'll try to get around to scanning the article and converting it to something useful like an Acrobat file (unless rkaudio beats me to it :) )

While there's generally copyright issues with posting an article from a magazine, I'm the copyright holder (since I'm the author), so I say "OK."

One thing I find amusing about this woofer is that it's the most ordinary-looking generic-looking 12" woofer you'd ever see... black stamped steel frame, 40 oz ceramic magnet, gray-ish pulp paper cone, foam surround. I just think the folks at Eminence decided to design a driver for very low frequency use in a sealed box.

I'm still somewhat stuck in the past, but my impression of what you see today is smaller ported (or "tuned") boxes that do very well down to, say, 30 or 35 Hz, and drop like a rock below that... or else a dedicated equalizer is needed to keep the frequency response flat. I think those are very good compromises since there's not a whole lot of musical "information" below 30 Hz, and besides, how many people can accept having one or two 5 cu ft boxes in their listening space? (I can...)


All times are GMT. The time now is 08:41 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2