Upper binding posts on Monitor75T not working

PHGraphics

2 weeks ago I finally unboxed and set up a pair of Monitor75T's I had purchased years ago. I know there is an ongoing debate as to the benefits, but I decided to bi-wire them.

The right speaker setup went as planned. I connected the cable to the bottom binding posts and heard what I expected. When I attached the other cable, the highs appeared, as expected. The left speaker setup did not go so well. Again, when I attached the cable to the bottom binding posts, I heard what I expected to hear, but when I attached the other cable to the upper posts there was absolutely no change in sound. As a test I attached the cable which had produced sound on the lower posts to the upper posts. There was no sound at all. As a second test I removed that cable from the upper posts and attached the cable I had originally run to the upper posts to the lower posts. That cable, too, produced a good low-end sound. In summary, both cables in my intended bi-wire system produced good sound when attached to the lower posts; neither cable produced any sound (or a change in sound) when attached to the upper posts. My conclusion: the problem has to be with the speaker's internal wiring. Does anyone have a different opinion?

I called tech support and all they could tell me was that Polk does not recommend bi-wiring and that I should try running a single cable with the factory jumper bars in place. I objected saying that just suppling the signal to the left speaker upper posts via the jumper bar, instead of via a discreet cable, was unlikely to get those upper posts to produce a signal, but they said they had no other suggestions except to take the speaker to an authorized repair center. (The nearest one is a 2-hour drive.)

Here is my question for people who know the inner workings of the internal electronics: is there a specific component (or group of components) in the crossover wiring which controls the reproduction of the signal arriving at the upper posts? If so, can I buy and replace that component myself?

All opinions and suggestions will be appreciated.

SeleniumFalcon

There are really only three parts that could be the cause. One is the high frequency tweeter, the second is the internal crossover network and the third is the connecting wire that goes from the crossover to the tweeter. The crossover is the probably the least likely cause, which leaves the connecting wire and the tweeter itself as the most probable. The usual troubleshooting is to remove the tweeter and test it by itself. It would require some basic hand tools, is this something you feel comfortable doing?

PHGraphics

I don't have time today, but removing the tweeter looks simple enough. I can try tonight or tomorrow. Once the tweeter is removed, can I just connect the speaker wire from the amp directly to the tweeter's contacts, or is that too much signal to be fed directly to the tweeter - without going through the crossover?

pitdogg2

very low volume only. You could also test it with a volt/ohm meter, it will either show some ohms or it will not. IF it shows zero it is bad.

PHGraphics

Well, I'm absolutely amazed, but I learned a lesson: always check the simple stuff first. When I pulled the tweeter, the green cable from the crossover to the tweeter was, in fact, loose and semi-hidden. It was far enough below the tweeter opening that I'm 99.99% certain that pulling out the tweeter is not what made the connector come loose. And that idea was reinforced when I was very surprised at the force required to firmly seat the connector on the tweeter's lead. But why in the world would that wire have come loose in a speaker being unboxed and used for the very first time? That question is the reason I didn't even think to check that before making this post.

So, thank you very much for your help -- and for saving me what could have turned out to be a long, needlessly expensive and emberassing trip to a speaker repair facility!

Toolfan66

Or swap the tweeters between the speakers. Have you just swapped the speakers from left to right?

F1nut

I believe he found the problem and his tweeter is working now.

msg

Larry's a really slow typist.