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-   -   15 Inch/38cm PA (sub)woofer (http://www.diyaudio.com/forums/subwoofers/80356-15-inch-38cm-pa-sub-woofer.html)

tubee 27th May 2006 07:52 AM

15 Inch/38cm PA (sub)woofer
 
Hi all

I found a 38cm PA speaker, they wanted to throw it away at the shop where i get my parts. The speaker was dead and the former user bought a new one. Unfortunate i don't have a camera at hand.

I measured the connection: zero ohm, but after scratching the isolation of the voice coil winding itself a 2nd measure: 6.1 ohms!! So its a bad connection, and after some soldering it plays again! :)

Some features: No brand name is stamped on it, only a code on (18cm ferrite!) magnet: 330772
I guess its an american or english make of late 1980's.
Steel pressed basket, textile 2 roll surrounded paper cone, at voice coil standard yellow cotton surround. Voice coil is 80 mm diameter, decompression hole in pole peace of 25mm.
Cone has rather thin (estimated 0.3/0.4 mm thick) not straight shape but has a "Nawi- membrane" or trumpet like. It plays easily to 3000hz and then rolls off. Cone dispacement is about +/- 5 mm.

Now i am figuring out what to do with it:

Could it be possible to enlarge cone mass with tissue paper/ with water mixed woodglue, to build a active subwoofer of it for my stereo/surround purposes. After that apply a dampening layer over cone (i experimented more often with speakers)

Well, what do you think?
Regards:

tubee 27th May 2006 08:42 AM

I have been searching for a cheap (+/-80W) sub amp.
Also any suggestions?

tubee 28th May 2006 08:46 PM

Well i don't get any response here.

In meantime thought things over. Its worthwile, because a friend of my, percussionist, said this PA speaker would cost around 300 Euro.

Can measure TS parameters via soundcard & poweramp (speaker workshop or Arta) and then calculate the casing for it as a subwoofer.

When TS parameters are not perfect for a sub, i could make cone some heavier with glass fibre/tissue or aluminium foil.

Thinking about 60 Litres bassreflex (+/- 42 * 42 * 50cm) with a dia 100mm pipe, length +/- 200 mm. Then have to find a cheap 100W amp or build one.

But first i will try it unmodified in a cheap made plywood box of around 60L, thinking about bassreflex (+/- 42 * 42 * 50cm) with a dia 100mm pipe, length +/- 200 mm. Then have to find a cheap 100W amp or build one later. First tests can with a standard amp here, see wat comes out of that giant.

Bazukaz 28th May 2006 08:55 PM

Hi,
What about leaving the speaker as it is and using a linkwitz rilley to equalise f. response, or using this http://sound.westhost.com/project48.htm
?

In my opinion , sealed box and lighter cone can have better transient response.
Regards,
Lukas.

tubee 29th May 2006 05:50 PM

Hi Lukas, thanks for reply.

With searching to a diy sub amp, this site came across too, but i did not look at it properly. I Agree with you, a heavy cone with port is allways "later" in time them a light one in a closed box (better transient / impulse performance) I have bass reflex surround speakers, but stuffed the ports.

With this equalizer there is problably no phase switch or pot needed anymore, but not sure about that. (all speakers are and stay in phaze without smearing) And funny enough he uses a 38cm speaker too.

tubee 22nd June 2006 12:22 PM

2 Attachment(s)
Here it is, will put it in a 60L enclosure soon.

tubee 22nd June 2006 12:26 PM

2 Attachment(s)
Backside, cd is for comparison

audiomachines 22nd June 2006 02:58 PM

hi sir,

I think it is a celestion or a wharfedale model.

regards,
audiomachine

tubee 22nd June 2006 03:22 PM

Yes Audiomachines, i thougt also this would be a UK (or USA?) manufacturer.

mashaffer 23rd June 2006 12:24 AM

might want to look here for my evolving plan for a 15" MI driver.

mike


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