InWall AB805 rattles

larrymcg

I have 2 AB805s in front (and 2 AB755s in the rear) along with a Polk subwoofer. There is no crossover between the amp and the speakers so the full spectrum goes to all the speakers (which is supposed to be OK with these speakers).

In any case, the left AB805 rattles or buzzes on medium loud sound with significant low end content. I have taken the speaker out of the wall and it rattles anyway, so it's not the mount.

It seems that *both* the 6" drivers are rattling. I pulled the wires of each one and the other continued to rattle. I made sure everything is tight and held onto everything I could and the rattling does not stop. So it's the drivers themselves.

Since they are both rattling should I assume both drivers got blown somehow? Or could it be a bad crossover in the speaker itself?

I guess I'm trying to determine if I should replace the entire speaker or just both 6" drivers.

Thanks,
Larry

[Deleted User]

Hello Larry,
It would be best to telephone Polk at 1-800-377-7655 for parts ordering information, mention you are a Club Polk member for reduced parts prices and free shipping.
Regards, Ken

larrymcg

Ken, thanks for the info.
Anyone have a suggestion about replacing both 6" drivers versus the entire speaker?
Larry

larrymcg

So I got two new drivers - MW7008s - which is what Polk lists for AB805 speakers. Well, the old drivers turned out to be MW7006s - not ..008s. So I leaped to the conclusion that the 08s are compatible replacement or upgrades to the 06s and proceeded to put in the new 08s. Well, the result sounds worse. Now rather than a rattle it sounds more like IM distortion and it's real obvious in the midrange and low end even at moderately low volumes.

Could it be that the 08s are incompatible with the crossover??

Larry

PS: I tried reversing the right and left speaker connections and the problem stays with the left speaker.

[Deleted User]

Hello Larry,
I'm sorry you're still having problems with the speakers. The MW7006 was the driver used in the original M5 speaker (this is a "wedge" shaped speaker, not the book shelf Monitor 5 speaker), I'm not sure why it would be found in the AB805. When you say you hear IM distortion, intermodulation distortion, do you mean you hear one frequency modulating another higher frequency? Is it possible the problem is with the tweeter? Sometimes its easy to miss diagnose where the problem is coming from, especially if the problem frequency is near the common crossover point between the tweeter and drivers. The MW7008 is the correct driver for the AB805 and AB855.
Maybe if you could describe the distortion's characteristics a little more it would help?
Regards, Ken

larrymcg

The speakers that came out of the AB805 have Polk labels stuck to them that say AB805 MW7006 BD0714 with a manufacture date of Sept 1997 (I bought them in 1998 so that makes sense). They look exactly like the 7008s.

Now, back to the distortion: Maybe IM is not it. It's the mids and lows that are just plain distorted -- not a rattle anymore -- but a clearly distorted sound. Maybe it's similar to a buzzing but it's not as simple as a buzz. I can even hear it clearly on a FM talk radio (local PBS which has a very clear signal). When I listened it was a male talking. But it's way objectionable on music of most any kind. Does not take strong low notes -- it's there all the time.

With the old drivers I got the distortion (rattle) only with strong low notes.

Since I replaced 7006s with 7008s, could I have driver/crossover incompatibility now? Polk lists the RE8005-1 as the correct crossover. I guess I could pull the speaker out of the wall again and check what it has is it.

I might be able to record a sample and attach an mp3 -- ooops. looks like mp3s are not allowed. Oh, well.....
I could post an mp3 on my website. Would that help?

Larry

larrymcg

I finally got the time to really experiment with the AB805. An interesting fact from the previous posts is that these speakers are supposed to have MW7008's in them but they have MW7006's. I purchased a couple 008's since those are listed by Polk as the correct speakers. The results were lots of distortion.

Today my more thorough experimenting showed:

Both 008's distorted when driven via the crossover.
Both 008's sound fine with the crossover bypassed.
I think that means the 008's are not at all compatible with the crossover.

Both 006's sound fine whether or not the crossover is used EXCEPT that one of them rattles with mildly loud low content. Previously I had convinced myself that both rattled.

So, not having any extra 006's to try, I disconnected the bad one and put the speaker back in the wall with one operational MW7006. Sounds fine to me now. Since I also use a subwoofer I might not notice the missing MW7006.

Larry

[Deleted User]

Hello Larry,
At this point its probably best to send the complete speaker and the two drivers to us at: Polk Audio, 2550 Britannia Blvd., Suite A, San Diego, CA. 92154 attention: Gil Palmer. Include a short note giving him an outline of the situation, I'm sure he will get the speaker sounding perfect and return it very quickly.
Regards, Ken