Calling all DCM Time Frame experts. I just picked up a pair of TF-275 speakers with a blown tweeter. It seems like there is very little info on this model online. It's rarely mentioned and I could not find a crossover schematic anywhere. Price wise, I was able to determine it fit between the TF-250 and the TF-350. That's pretty obvious, based on the model number, but does anyone know the chronological order of these three models? I can't imagine why they would have three models so close in size, specs and price all available at the same time. Based on nothing more than pure speculation and a few hunches, I am wondering if the TF-275 is a later model that replaced both the TF-250 and TF-350 at the bottom of the Time Frame food chain. Anyone know the dates the various models were introduced and discontinued?
I learned a few more things in my research. First, the TF-275 uses the same tweeter, and most likely, the same midbass driver as the TF-600. Basically, it uses the exact same concentrically mounted midbass/tweeter sandwich as the TF-600. Here's what it look like with sock pulled down:
So, it's basically half of a TF-600 with no additional midbass driver and no rear facing tweeters. That also makes the crossover much simpler as there is no time delay circuitry for the rear facing tweeters. I didn't take any photos of the crossovers, but I will when I pull them out for a recap. The crossover only has three caps: two 3.3uF NP electrolytics and one .47uF film cap.
You can read more about my restoration/repair work
here (no refoam needed the TF-275 midbass driver uses rubber surrounds just like the TF-600).
In any case, one other thing that makes me wonder if the TF-275 is a later model is the condition of the inner sock "headliner" material. It's in beautiful condition, with absolutely no deterioration what-so-ever. Much better than all the photos I've seen online of disintegrating black foam. These TF-275s are in overall excellent condition (other than the blow tweeter), but the condition of the headliner fabric makes me wonder, again, if these are a later model. Unfortunately, these didn't come with any labels on the terminal cups. So, no serial numbers to go by. In fact, it took me a while to figure out exactly what model I had.
The good news is replacement tweeters are available, and they are cheap (about 3 bucks each, from Parts Express). They are: Goldwood GT-302/S 1/2" Mylar Dome Tweeters (DCM recommended replacement for the TF-600).
Parts Express Part Number 270-175. I'll go ahead and replace them both, so the right and left channel speakers match. I also ordered some Audyn Q4 caps (two 3.3uF and one 0.47uF per speaker) to recap the crossovers. So, about $9.00 per speaker to replace the tweeters and recap the crossovers. Should be money well spent.
These are my first DCM speakers and I'm already hooked and scouring Craigslist for some of the larger models (I think I'd like to give the TF-600s a try, as they seem to be the closely related to the TF-275s). As shown in my restoration thread, I temporarily hooked up a little Audax tweeter just to verify that there are no other hidden problems and they sound great. I listened to them all day, even pulled out some of my favorite SACDs for the occasion. Maybe I should change my username to DCM_Fan.
