Need help with replacing woofers on a Technics SB-501

[kaguhara]

Hello, I have the chance to get these apparently really good speakers, but the seller is giving them for cheap because it arrived with one woofer missing. I'm a total newbie at DIYing speakers but I figured I could ask forums for some help.

Technics SB-501 specs: Technics SB-501 specifications Technics

The options available to me right now are the EAS-30PL120, the woofers from Technics SB-6000 which I'm not sure they match, or from the Diatone DS-35B I own right now.

I'm also open for suggestions from Japan Vintage Speakers market, since they're available to me through Yahoo and Mercari. Searching AK, apparently its bigger brother SB-1000 can fit but sadly they're probably rarer than the SB-501s woofers themselves.

for reference, I'm just gonna be listening to them at around 15 watts or lower.

 

[swechsler]

I probably wouldn't try to get another Technics woofer to match. However, you're lucky on a few points:

1. It's a sealed cabinet, which makes it a bit easier to match up than if it was ported
2. You have a frequency response graph
3. The crossover frequency and slope are published

So if you're interested in this project, what I'd do is search for a modern woofer that will fit the cabinet and has approximately the same sensitivity (92dbB/W/m) as the published sensitivity of the system. Then I'd calculate the internal volume of the cabinet, and use some software like WinISD to model the proposed replacement woofer in the cabinet, to see if you can approximate the response of the original woofer. If that model didn't work, try another.

Once you've found a suitable woofer, using the impedance graph of that woofer (hopefully it will have this listed with the specs), you can use an online crossover calculator to design a new high pass crossover (you'll only need two components - one inductor and one capacitor - similar to the existing design), using as the crossover frequency the published frequency from the spec sheet (and hopefully that's correct; manufacturers have known to change specs before or during manufacturing).

As you can see, speaker design is complicated (it's not just dropping a bunch of drivers in a box), and an actual speaker engineer would spend a lot of time listening and tuning, trying different drivers. I don't know what the audio market is like where you live, but in the US, this sort of project is rarely cost effective, and you'd be better off just buying a properly working pair of speakers, no matter how good the original deal seems.