RTA12 Inquiry

stubby2

Just curious if anyone has seen/owned a pair of RTA12 with the short cabinets and the vertical mount Peerless tweets.
Found a pair at decent price but had not seen that particular combo.

Thanks!

stubby2

Sorry, I just realized my error in description of the RTA's I am considering.
Horizontal mount tweeter on the short cabinet.

Jazzhead

I own a pair (original owner). They sound good in their stock configuration (they have the Peerless tweeter) and can sound very good with enough modification. They have some inherent problems that were fixed with the later versions (12B, 12C). In the earliest version both midwoofers operate at the same frequency which causes an audible comb filtering problem (to my ears this affects their imaging capability). In the later versions the outer driver frequency was rolled off to prevent this (these speakers are used in a "right and left" mirror-imaged position):

http://www.hifi-classic.net/review/polk-audio-rta-12b-339.html

The other major issue addressed was diffraction from the tweeter output off the top of the cabinet. This causes some audible smear in the upper frequencies. As stated in the article above, later versions employed an antidiffraction device/ramp.

There is a mod for the comb filtering problem that is quite effective:

https://forum.polkaudio.com/discussion/173834/westmassguys-idea-employing-damping-to-mitigate-comb-filtering-and-lobing

I eliminated the diffraction problem by fabricating a diffraction device/ramp (basically I copied Polk's design) from dynamatted aluminum (you also have to modify the "tophats"):



The original crossovers greatly benefit from an upgrade. DHS Speaker Service did a fine rebuild of mine with Sonicaps and Mills resistors (a favored combo here on the forum). I also replaced the binding posts and internal wiring, and foamed the internal driver baskets. These speakers respond well to lots of power.

The originals sound fine in their stock configuration, but if you do all the standard mods recommended on the forum, along with these outlined above they are very musically accurate and detailed, with good bass and imaging. Obviously, I enjoy doing these mods - some may not, but I've found it all to be very rewarding.

stubby2

Hey Jazzhead, thank you for all the info and the photo of your modded 12's. I bet those are some sweet sounding speakers!

The pair I'm looking at have the same style cabinets as yours but have the 12B tweeter housing and diffraction spoiler. Polk was always tweaking things on the fly so maybe these are a product of the transition from original style to the "B" model.

Gardenstater

Audio Jan 1980:



Audio Oct 1981(note the more elaborate diffraction treatment than usually seen):

stubby2

Yes. If you take the tweeter housing from 1981 and place it on the cabinet from 1980 you would have what I'm looking at.
Not the bigger diffraction ramp, though.

Gardenstater

Without revealing your sales link do you have a picture or screenshot? Sounds like you found a missing link that escaped the factory!

stubby2

Had I been a smart guy I would have snapped a photo!

SeleniumFalcon

stubby2

Here are some pics the seller took for me.