Restore Speakers-DBX Soundfield 50

[mwb]

I own some older DBX soundfield 50 speakers which i purchased new from a audio shop in Louisville, KY back in the late 80's i think, anyway the speakers have started to just dissolve, and after reading the literature i got with them the midrange and woofers are paper and thus they have seen thier last days.

anyway upon trying to restore them, the cabinets are in great shape still, i was interested in either restoring them to original sonic quality or upgrading them to better then new.

i have the literature with mine that says Mark F. Davis of DBX designed this speaker and the senior project engineer Micheal Chamness,, Tom Miller and John Buzzotta, all of DBX were involved in some manner or another .

My delima, as far as i can tell the speakers are not marked with manufacturer and when i called dbx the person on the other end told me they were custom designed just for this project. When i do searches i find all these DBX ones from DAK etc.... which do not fit the description of my speakers. My questions are how do i find an adequate or better then adequate replacement for at least the midrange and woofers

below is the description of my DBX Soundfield 50's


Overall speaker specs
34Hz - 20kHz
91 SPL / 2.83v (=1 watt into 8 ohms)/1 m
4 ohms nominal, 2.5 ohms minimum
40 - 400 watts/ch at 4 ohms
10" woofer, 6/12" midrange, 4" upper midrange, 3 ultra-wide-dispersion 1/2" Tweeters per cabinet.
Crossovers- Phased arrangement: 200/800/3150 Hz, main axis
cabinet - Vented, braced 3/4" Dense Fiberboard.

The Woofers are additionally described below:
10"
1 1/2" diameter (38mm) Voice Coils with Extra-Long Throw (12mm)
recessed backplate
two layers of high temp copper wire wound on aluminum bobbin
zinc plated frames
compliance matched surrounds and spiders
foam and zinc diecast trim rings and low resonance


Midranges are explained as follows in thier brochure
smooth unboxy-sounding
large magnet ferrofluid-cooled
hi power handling
ideal resonance control and damping, and minimal "IM distortion
note: they do note that the speakers are not any type of plastic , not polypropylene or bextrene
they are paper the designer states that paper and that plastic or plastic-coated midranges and woofers have no sonic advantage

Tweeters
1/2" (12 or 13mm) Ultra-wide dispersion
ferrofluid cooling
oversized magnets
2-layer copper voice coils
mylar (polycarbonate) diaphragm/bobbin

 

[Swerd]

...the speakers have started to just dissolve, and after reading the literature i got with them the midrange and woofers are paper and thus they have seen thier last days....

When you say the speakers are dissolving, do you mean the entire cone, or do you mean the foam rubber surround? The attached picture shows what part the surround is.

Paper cones on speakers should last quite a long time. Polyurethane foam often dry rots after about 15-20 years depending on how much exposure to UV light or oxidizing atmosphere they got. If this is your problem, there are repair kits commonly sold that should get your speakers running again. A google search on speaker surround repair kits should find you a bunch of sources.

 

[mwb]

DBX Soundfield update

The paper is crumbling in the woofers, this could be from living near the ocean in florida for many years. also i bought these as a young lad and they have taken some punishment over the years, i powered them with a soundcraftsment A5002 amp as well.

But since my last post i have gotten some feedback from another forum that says maybe the speakers in the earlier model were special but in production they were not, so someone gave me the numbers off the back of thier speakers, at least the woofers and the midrange

they are as follows 23009300 871TNEor B mids
23009200 873TNB or 8

Can anyone tell me if these numbers mean anything and if so how do i track them down?

 

[Swerd]

Wow, that's the first time I've ever heard of paper speaker cones crumbling. Usually if a part fails from being overdriven, it is the voice coil, or the voice coil connection to the cone or spider. I suppose there is a first for everything. I bet the air near the ocean, full of water and salt, may have had something to do with that.

No those numbers don't mean anything to me. There are two good suppliers of speaker drivers, Parts Express and Madisound. Google those names. Call or email them to see if they can help. They do have a working knowledge of suitable replacement drivers for older speakers.

Madisound also has a web forum devoted to DIY speaker building, http://www.madisound.com/cgi-bin/discuss.cgi , where you can post this same question.

 

[Rickster71]

Try this guy, I've used him before.

Try www.classicloudspeakerservices.com

He has a book that cross-references the numbers on the speakers. (to find a replacement)
He also does "all" types of repair. He's very good, and priced right.