S75 Crossover surprise… and new problem

[Levi]

First and foremost, I am pretty new to vintage equipment but am enjoying the education, and am taking my lumps – as well as wins – along the way.

I picked up a pair of very clean looking S75s a couple months back, and when I hooked them up to my SX850, they sounded very muffled. Voices in particular. From just listening to music, and doing research, it seemed like recapping the crossovers could be a solution. So, I ordered a recap kit (not from this site :/ ) and it arrived the other day.

Today, I got ready to dig in. I got the woofer pulled from one, looked inside, and got a bit of a surprise. The first thing I noticed was that the wires leading to the woofer had been spliced. Not the end of the world as they were soldered and shrinkwrapped, but that didn’t seem like a factory “feature”.

Then I looked at the crossover itself and was further surprised. The caps on the board all look like the caps I had sitting in a bag next to me, not what I have seen in my research. Then I realized that all of the wires to the speakers were spliced like the woofer speakers.

From this, my conclusion is that these crossovers have already been recapped.

Great right? Well, no, because of the poor sound quality.

So then I started down the path of a bad tweeter. I have a WIIM Pro hooked up to my receiver, downloaded a frequency app, and gave it a shot. First, I tested with a known pair of speakers that sound good to me, Infinity SM255s, and could hear from roughly 20hz to about 15000 hz. Seems reasonable.

Doing the same sweep test with the S75s, and I pretty much stop hearing anything around 9k hz or so.

Now, I want to put two caveats out there. One, in my mid 40’s with known hearing loss, I’m not the best person for a frequency test (hence the test with the 255s so I had a baseline for what I can hear). Second, I’m doing this testing with an SX-750 with questionable quality (it’s on my list for a good pot cleaning and whatnot). But that said, I did the test w/o touching the volume on the receiver, and only controlling via bluetooth.

Ok, so that’s my information, along with attached photos.

My question is, what are the ranges for the mid and tweeter in the S75s? I’ve only tested one of two speakers as of this writing, but I can say they have both sounded the same when I had them hooked up to the 850. I also have not pulled any of the speakers from the enclosure to ensure wires are hooked up, etc.

What are your thoughts? Crossovers probably good? Tweeters probably shot? I’d love to get these into a condition for daily use, and am willing to throw a couple bucks at them to do so.

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Location: Iowa

[Levi]

I did take some time to test each speaker with my DMM.

Woofer disconnected: 3.5
Super tweeter disconnected: OL
Tweeter connected: 5.8
Mid connected: 6.6

So I think I’ve confirmed the assumption.

What are good replacement super tweeters?

Location: Iowa

[Levi]

Well… super tweeters have been replaced, and the pair sounds amazing!

Location: Iowa

[pl212]

Interesting, were you able to find direct replacements for the super tweeters?

Location: Silicon Valley

[Levi]

I was! And they shipped quickly.

I found them via another post in this forum. In an effort to spread that love, here’s the link:

MW Audio MT-4115: 1″ Dome Tweeter

Also, interesting note – when I opened the second speaker I found that its crossover had not been rebuilt. Everything looked good on the board, so I opted to just swap the tweeter and cross my fingers. So far so good. To my ears, they sound the same.

Location: Iowa

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