Monitor 7B Tweeter Works but no Sound from Mid and Sub

raymondlee2900

I recently bought a used pair of monitor 7b and found out they actually are broken. I hear the tweeters but I don’t hear any sound from the mid and sub. I was wondering if anyone may know the potential possibilities for this. I was going to open this later today after work.

Navy_Goat

Assuming the mid driver is not mechanically seized (magnet shift), I would recommend removing the mid driver to check connections. I suspect some sort of open condition between the crossover and mid driver. The monitor 7 is not a three way design to the best of my knowledge, so there is no "Sub". The larger "driver" is a PR I believe.

pitdogg2

Midwoofer and passive radiator design.

tonyb

I can't recall if there are 2 sets of speaker connections with the brass blades connecting on the 7b's, but if there are, make sure those are in place between the upper and lower sets of posts.

pitdogg2

tonyb wrote: »

I can't recall if there are 2 sets of speaker connections with the brass blades connecting on the 7b's, but if there are, make sure those are in place between the upper and lower sets of posts.

No only one set of binding post.
Take middle driver out iirc it's a mw6502 either way get the MW number off sticker. Try to see if its blown with a multimeter.

raymondlee2900

I think I remember hearing a rattling noise as well when I move it.

boston1450

Take 2 fingers one on each side of the woofer dome & lightly push woofer in. If they do not move in&out with ease-your woofer is spent. The magnet shift has probably occurred.. If that's not the problem - take the woofer out & inspect.... You should put a bead of LokTite on each side of the magnets to help prevent magnet shift in the future. Pls report back.... EDIT welcome to the forum

raymondlee2900

Sounds good, I’ll will work on this over break, thanks everyone.

mhardy6647

pitdogg2 wrote: »

Midwoofer and passive radiator design.

@raymondlee2900 is this (and the post before it) clear enough to you? The Monitor 7 family are all two way loudspeakers, appearances to the contrary The big cone at the bottom is a passive radiator (which is, in essence, "just" another way of building a bass reflex box that doesn't use an open port). The 7B uses a dome tweeter and a small woofer in a large-ish box with the aforementioned passive radiator.

The woofer and the passive radiator are 'acoustically' coupled in that large, tightly sealed box.

A likely failure mode at this late date, unfortunately, is magnet shift due to deterioration of the adhesive that was used to attach the magnets on the 6-1/2 inch drivers. You can test the condition of the woofers as described by @boston1450

Several threads at this forum on the magnet shift issue; do a quick search and read all about it.

Welcome & happy Thanksgiving (assuming you're in the US)!


One of my Monitor 7A in "rosewood" vinyl

raymondlee2900

I have fixed it, turns out the mid speaker wire was loose and detached from the speaker. Super easy fix, thanks everyone.

Navy_Goat

raymondlee2900 wrote: »

I have fixed it, turns out the mid speaker wire was loose and detached from the speaker. Super easy fix, thanks everyone.

Glad it worked out. How do they sound?

boston1450

@raymondlee2900 . Wonderful. Pls take advice on gluing magnets. Put a bead on each side of magnet to prevent magnet shift. Takes only minutes to do - as replacing them is becoming hard to get. Enjoy your speakers