Monitor 12 Idea (from a newbie)

CGTIII

Since side-by-side mids cause smearing, I wonder if it would take much crossover mod to only use the outer pair on each? Suppose that would also result in lesser response from the PR, but many folks use a sub anyway...

Perhaps this idea has already been tried on other models as well.

CGTIII

This suggestion thread is with apologies to the purists. Idea arose for Polkie who'd been given a pair of 12s with a tweeter and a couple of mids already dead to make the best of them most easily and using the fewest additional parts.

Or perhaps a crossover could be swapped in that was already for two mids and the same tweeters.

westmassguy

Not a good idea. You 'll throw off the voicing of the speaker. The PR is sized and weighted for four woofers.
See this thread for an alternative:
http://forum.polkaudio.com/discussion/173834/westmassguys-idea-employing-damping-to-mitigate-comb-filtering-and-lobing

[Deleted User]

And your two mid-woofers not being used will become passive radiators adding to the problem of too much PR for just two mid-woofers.

Westmassguy has a cure if you want to address smearing. There's a recent thread from someone that did David's trick and seemed to be quite happy with it. I have Monitor 12 series 2's and understand the smearing concept but simply don't hear it. Only thing I did to mine behind the drivers was pull out the poly fill and line the back, underside of top, and side walls with Ozite trunk liner, then put the poly junk back in. I pushed it deeper into the cabinets than it came out, then added lamb's wool between the drivers and poly junk. And make sure it's all behind the 6.5's, staying above the PR.

CGTIII

Thanks. I'd not read that thread yet. Quite ambitious!

soundfreak1

Polk had a cure for that back in the day called the RTA12B than the "C" model. Just saying. I think it's easier to go with that "mod" than trying to make the m12 do what the RTA does!

Jazzhead

I did the mod that westmassguy suggested above. Before I did it my speakers sounded very good, and actually did a good job of "disappearing" with decent imaging (westmassguy had rebuilt the crossovers and I had done many other improvements). However, the damping mod enables the image to "lock in" better, and improves the detail, clarity, resolution, and size of the soundstage. The best analogy I can present is it's like using a stereo photograph viewer - like when you are looking at two air photographs and they come together and you can then see a 3D image. The other thing I noticed is that before I did the mod I could move left and right in front of the speaker's "sweet spot" and hear some subtle "blips" in the image. I'm guessing this was acoustic lobing? (a lot of this acoustic theory goes over my head, but I know what I hear). Anyway, that phenomenon is long gone, as well as my speaker's tendency to get 'shouty" when if I gave them a lot of power. Now that the mod is done I do have to provide a bit more power to equal the pre-mod volume level, but the sound is much more flat and pleasing. I still listen in the "first watt" as my speakers are fairly efficient.

Faustin

Jazzhead - Wait until those c/o's get some hours under their belt. They will settle in and you will be amazed as they really come to life

Jazzhead

Faustin: You are my inspiration actually. David sent pictures of the RTA's you refurbished (a thing of beauty) before I started this process. I know my original RTA's don't have the sophistication of the later models, but they are sure sounding good with all of the mods, along with David's crossover work etc. Listening to music is a daily thing with me and I am enjoying the improvement immensely.

HzTweaker

I have been consulting @westmassguy about the Imaging and sound stage of my monitor 10As and he sent me @Jazzhead thread http://forum.polkaudio.com/discussion/173834/westmassguys-idea-employing-damping-to-mitigate-comb-filtering-and-lobing

I'd like to say to Jazzhead, I think you did a great job on your mods. I bet combined with those hot-rodded Xovers they sound great!

I'm pretty sure I want to accommodate theses mods to fit the 10s cabs. I'll have plenty of questions following the start of the project. But for now the main issue I'm experiencing with my 10s are tried Xovers, so I'll probably focus on that first (after the CRS build is finished or stalls).

Jazzhead

HzTweaker: Thanks for the kind words. We have a great resource in westmassguy and others here on the forum. You can't beat the "trial and learn" approach that is practiced on this forum. And yes, I am a bit stunned at how good 36 year old speakers can sound.