Blown SDA-2B

F1nut

Have you tried a different amp?

TheRealSpinner

I only have the Adcom GFA 555. I would try the Marantz receiver/pre-amp that I am already using as the source for the Adcom, but it is only 8 ohm stable, hence the Adcom. I don't know that it would tell me anything, since it's part of the source.

I could try to bring the Onkyo receiver home from work. It seems like a long shot though.

F1nut

The 2B's are 6 ohm nominal, so that Marantz receiver should have no problem driving them unless you are cranking the volume level so high that it causes the Marantz to clip. In which case it will shut down, but it's got nothing to do with the 2B's being 6 ohm. So, hook the Marantz back up and play it at less than clipping levels to see if the speakers still sound bad.

BTW, a source is a CD player, turntable, reel to reel, etc. and not a pre amp or amp or receiver.

TheRealSpinner

F1nut wrote: »

BTW, a source is a CD player, turntable, reel to reel, etc. and not a pre amp or amp or receiver.

Thanks, I'll add that to my vocabulary.

As for the Marantz, I'll Ty it again, but doesn't quite make sense about clipping shutting it down. Before I bought the GFA, I was listening to the SDAs at a somewhat loud volume (but nowhere near as loud as I used to play my JBLs with it).

The Marantz volume goes up to "+15db". I never really understood what that was I reference to, but that's another matter. Normal listening volume is "-30db" or -25db". Party volumes would be closer to "-10db" and that was LOUD (with the JBLs). It seemed that I was turning it up to -20db regularly with the SDAs and "-10db" was still quiet enough to still hold a conversation (a loud conversation, but not like party volume loud). THAT was what was shutting off the amp; playing the SDAs at "-10db" for 15 or so minutes. There was never any clipping that I heard, and like I said before, it never happened with the JBLs. Turning the volume down fixed the shutdowns.

Come to think of it, I did have both the pin and blade hooked up (pin to pin, blade to blade), which might have added to the problem.

F1nut

The Marantz volume goes up to "+15db". I never really understood what that was I reference to, but that's another matter. Normal listening volume is "-30db" or -25db". Party volumes would be closer to "-10db" and that was LOUD (with the JBLs). It seemed that I was turning it up to -20db regularly with the SDAs and "-10db" was still quiet enough to still hold a conversation (a loud conversation, but not like party volume loud). THAT was what was shutting off the amp; playing the SDAs at "-10db" for 15 or so minutes. There was never any clipping that I heard, and like I said before, it never happened with the JBLs. Turning the volume down fixed the shutdowns.

The reason for the differences you describe is the efficiency of each speaker. The Polk's are 90dB @ 1w/1m. The JBL's efficiency is much higher. Therefore, it takes more power for the Polk's to achieve the same SPL of the JBL's. When you tried to crank your Marantz with the Polk's, it ran out of gas, clipped and shut down. Basic audio 101.

TheRealSpinner

I understand the differences in efficiency, and its effect, thanks. I also know what a clipped signal sounds like, and that was not happening. What I was noticing was even for its labeled volume (regardless of its db output), it would play audibly correct, but then cut out (I'm assuming from heat because the amp was very warm). This is why I was saying that the Marantz was not OK with playing the SDAs.

TheRealSpinner

OK, let's update...

I just got back from Polk distribution center in Vista, CA (I talked them into letting me pick them up in person). I got one of 6503, and two of RDO 194-1. I'm very pleased with the fix. :-)

I've read that the RDOs need 50+ hours of break-in, but I like them already. They seem to be much less bright, and take the edge off. At this point, I don't think the tweeters were blown; the reduced treble I was experiencing in the left channel from the test tones turned out to be the blown mid making extra noise that overpowered the tweeter, making me think there was less highs.

I am still very pleased that I bought the new tweeters, they are making my listening experiencing much more enjoyable.

Thank you, everybody, for the help.