Ex Polk Audio RT25i's - Soft Dome Tweeters "KIT SET"
This kit set is offered for the experimenter/D.I.Y enthusiast who wishes to know more about the construction of these tweeters, which do share common characteristics with other similar design tweeters e.g Peerless.
Great opportunity to learn along the way and hopefully end up with a decent pair of Polk tweeters
Don't ask me how this happened but the tweeters need to be re-assembled, please read on ...
Polk Audio (USA)
Circa early 2000's
Part number: SL6510
40W RMS Power rating EACH
8 Ohm nominal impedance
2x Tweeters but in "kit set" form! (see more below)
Soft Dome - I suspect this is the silk material Polk used in their earlier dome's - NOT METAL!
1" (25.4mm) voice coil
Sensitivity: 92 dB @ 1W/1m
Frequency range: 2.5KHz ~ 25Khz
Sorry but I don't have a frequency response graph available (to check for "bumps" in the frequency response)
Spade terminals (+ terminal is larger to facilitate correct polarity connection)
Fits a 76mm mounting hole
Face (plastic) has a 95mm diameter
Mounting screws are spaced at 66.6mm on center to each other (triangular mounting ) or 83.8mm on the radius
Original mounting screws (6) are supplied
Packaged as described below, total weight is 900 gram
COSMETIC CONDITION:
Supplied as TWO SECTIONS!
The face with the soft dome and voice coil/terminals
All are in excellent condition i.e no damage to the dome or plastic frame
The "back-end" is the magnets, these are also in great condition
TESTING/NOTES:
I AM OFFERING THIS PAIR OF TWEETERS FOR THE EXPERIMENTER/D.I.Y ENTHUSIAST
The two sections of each tweeter need to be carefully aligned together and then secured in place.
Both voice coils measure 5.6 Ohm DC, this is NOT the impedance but the test was made to check DC continuity only.
In many loudspeaker systems, the tweeters are the first to "fry" but these tweeter voice coils are fine.
It will be necessary to VERY CAREFULLY clean all around the voice coil and the corresponding magnet face - at the moment they are quite "dirty" it actually looks as though ferrofluid remains in both sections. This will need to be replaced.
Here is a link to a forum that discusses such things: https://forum.polkaudio.com/discussion/170787/lets-talk-about-ferrofluid
Cleaning is critical to ensure smooth travel of the voice coil as current flows through it (audio) within the very strong magnetic field and corresponding physical movement of the dome.
Next step is the fitting/alignment of the rear magnet assembly to the face section.
SUPER STRONG MAGNETS (Material is unknown), when the magnet is mated with the face, TAKE GREAT CARE!! It is a good idea to use a non-ferrous "spacer" so that the alignment can be made correctly, the magnetic "pull or attraction force" is considerable!
The end result SHOULD be a fully functioning SL6500 dome tweeter set.
Since taking the photographs I have very carefully packed the face's and magnets onto backing cardboard along with the securing screws and then sealed in plastic. The domes in particular have extra protection above them to prevent damage to the dome material (sheet styro foam, not under pressure)
I am satisfied these will ship well in this condition, no matter what the orientation of the package while being handled.
