Basic advice on messing around with old cabinets

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piranesi

New Member
Pretty basic dummy question I think but here goes.

I grabbed a pair of Technics Sb-2440 at a garage sale for $5 but both the tweeter and Mid in both speakers are dead and only the woofers work. I'd like to mess around with them as a beginner's project though and see if I can make something nice out of them.

IMG_6178.jpg


I notice that those particular parts don't show up often on Ebay and I'm tired of waiting around to collect a set so I'm thinking about just tearing everything out and using the cabinets with a DIY kit.

Any thoughts on this idea? Or suggestions for what will fit this type of cabinet in terms of kits, crossovers, drivers? Are the cabinets any good? I honestly would rather tinker around with the electronics side and am not so much into wookworking so I'm unlikely to ever want to build a cabinet from scratch.

What are the main factors I need to take into consideration to turn these cabinets into a nice set of DIY speakers?

Or should I wait it out for the correct drivers? And if that's the better way to go, how would I go about matching another part correctly to the crossover and existing woofers?
 
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I'd pull each of the 4 non-working drivers and check them with a DMM--it is uncommon to wipe the tweeters and mids on both speakers. There may be a protection fuse on the crossovers, or something might have killed a couple caps in the crossovers.
 
Oops. I should have mentioned I already did that. They are all shot and the woofers are showing about 6 Ohm (they are rated at 8 so I think that's right on).

The image I posted before is just a generic shot I found. Here is what I've actually got in front of me.

5oaqCOr.jpg
 
Most Technics speaker cabinets are pretty thin. I'd brace the sides if you decide to continue with this project. These look like they came as part of a rack system, so getting specs may be a bit difficult, but if you can get clear pics of the crossovers with all the capacitor values visible, we can probably work out the crossover frequencies. With that info you can probably spec some inexpensive replacement mids and tweeters that will be superior to what was originally in there.
 
piranesi said:
Oops. I should have mentioned I already did that. They are all shot and the woofers are showing about 6 Ohm (they are rated at 8 so I think that's right on).

The image I posted before is just a generic shot I found. Here is what I've actually got in front of me.

5oaqCOr.jpg
Click to expand...

You are measuring the resistance of the driver, not the nominal 8 ohm impedance rating of your speakers. Chances are your drivers are working since you got a resistance reading.
 
Maybe search eBay for the drivers, using any part labels or numbers on them. Even if the speakers don't show up very often, but maybe the drivers do? Also, it looks like they use a sealed-back mid. Do a search on that too, and see what turns up. Other than that, I'd keep searching Technics speakers, to check for matches.

Good luck.
 
The cabinets look like a great place to start for educational purposes. Inexpensively built cabinets, as I suspect these are, are perfect to illustrate compromises made during design and construction. You may or may not decide to improve upon them.

How are they braced? What are they lined with? What crossover was used? What is the volume and port dimensions?

Any chance you have a spare 5.1 or 7.x channel AVR with 5.1 or 7.x channel inputs? Got a spare receiver or, better yet, a spare subwoofer amp?

If you really want to get into the DIY stuff, a spare AVR, subwoofer amp, and a 2x4 miniDSP crossover will allow you to drop in a mid and tweeter and run them as a 2.1 system (basically a 2-way speaker with subwoofer in the same cabinet). Of course this is far more complicated and expensive than just dropping in replacement drivers....but if you really want to get into DIY speaker building, read up on the miniDSP and jump on in to the rabbit hole.

Good luck!
 
^^^The minidsp is an excellent tool^^^

If you want to change the woofer, look into "enclosure modeling" to get a rough idea of what driver may work in a given enclosure. Winisd and Bassbox modeling software(not always accurate) will help with calculations based on a driver's TS parameters.

The "loudspeaker design cookbook" will give a good start on how to build a speaker from scratch.
 
Here is an easy and inexpensive option.

1. Remove the crossover.
2. Wire the woofer terminals to the input jacks on the back
3. You now have a pair of single driver full range speakers.

Good listening. :music:
 
This is all great. I think maybe I will try a few of these...just use these cabinets to try different things out trial and error and see how they sound instead of thinking I'm going to end up with something great when all is said and done.
 
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