After 4 years with my beloved SR's and 3 years competing in SQ competitions with both the SR5250 and 6500, Ive learned a lot about them and thought Id share some of the tidbits Ive come across in the way of tuning these beauties......plus Im bored and this will kill a good 20 minutes.
If youre going to separate the tweeter from the mid, wire them out of phase. In both my truck and my car, they blended in and the image pulled up higher a ton with them out of phase. Having them wired in phase with each other also caused some cancellation at the crossover point.
The SR5250's will play well passed 5 KHz at 90 degrees off axis but I found 5 K to be the best crossover point for them with the mids low and the tweeters high in the car. Any higher than 5 and things thinned out a little too much. I also found using shallow slopes like 12 db worked well. I found a 12 db cutoff slope on both mid and tweet made them blend in very well and kept my stage nice and high.
The SR6500's will play sky high for a 6.5. They dont start rolling off til passed 6.5 KHz @ 90 degrees off axis but they dont "play well" higher than 4. For these speakers I believe 4 KHz is the best crossover point. This was the case in my big Dodge Ram and in my little Honda Accord. 3.2 KHz got a little "thicker" and 5 KHz got too "thin" but 4 KHz was the most realistic. However, unlike the 5250's Ive found a steeper slope works better here. Ive got mine cutoff at 24 db/octave. I tried them at 12 db like the 5.25's but it gave the midrange a little too much "reverby" sound and I never could dial it out.
As sweet as the ring radiator tweeters are, theyre a BITCH to tune in a car. Theyre very directional and can give you fits cause theyll play some frequencies louder on one side of the car than the other. For instance, 10 KHz is 4 db louder from the left tweeter but 12 KHz is 3 db louder from the right tweeter and so on. This doesnt necessarily affect the SQ from them but does wreak havoc on your imaging. The upside is that once theyre dialed in they sound awesome! Very clean and smooth. They dont play down low very well so forget about crossing them over anywhere near 2.5 K or even 3. While theyll get that low, they wont play with enough balls to blend in properly with the mids.
Since the tweeters are so directional, the best place to mount them is up high. The A pillars are my favorite, but you can also use the dash. These tweeters are very smooth and even firing off the windshield, they wont be harsh so long as theyre attenuated.
Speaking of which, turn em down! If you dont have a crossover with a level on it then use the one on the passive crossover and cut em the full 3 db. Mine are at -8 right now.
The SR5250's have excellent midbass for a speaker as small as they are. I never got dinged for weak midbass when I ran them in '07. That being said, dont run them too low. 50 Hz is the absolute lowest I would go. They will play much lower but they wont sound good. They get sloppy below 50.
The 6500's have weird midbass. They have a lot of energy but they dont have great "punch". They seem to dip around 63 Hz which is where the punch is. However, they are pretty boomy at 80 Hz so youll want to cut that frequency a bit especially if youre listening to jazz or music with a stand up bass guitar in it.
The 6500's have a double edged sword thing going on with their low end response. While theyll play down to 40 Hz all day long AND sound good doing it, frequencies below 63 Hz will cause them to bottom out pretty quick if you crank em up too much. If you listen to your music at a fairly low to moderate level then cut them puppies off at 40 Hz and enjoy all that wonderful up front bass. But if you listen at pretty stout volumes then youre gonna want to cut em at 63 Hz and let the sub handle everything below that.
As for midrange, both the 6500 and 5250 are near perfect at it. All youre gonna have to do is cut whatever frequencies the car's interior is causing to peak and then let the SR's do the rest. This is a huge benefit in tuning cause getting a realistic midrange dialed in aint easy. Luckily the Polk engineers did all the legwork.
The SR mids are just stupid off axis. Impressive enough the 6500 will do 5 KHz while still being able to hit 40 Hz but the 5250 will play up to 8 freaking-KHz at 90 degrees off axis before rolling off and that is just insane! It also means that you can mount these babies pretty much anywhere and not have to worry about getting them on axis which makes them easier to mount in the kicks if you want to and not have to worry about taking up leg room.
I have noticed the 6500s have a little peak around 800 Hz. The 5250s didnt have this but the 6500's do both in my old Ram and in my Accord so youre gonna want to doctor this frequency range up some.
The 6500's are gonna give you some problems in focusing up the imaging. For some reason the midrange focus in the 630-1200 Hz range seems to want to smear to the right. This was true in my Ram and Accord. I cant get it figured out. I do know that seating position affects it. With my seat leaned way back, this problem is gone - with it in a driving position, its there so when installing yours, take that into consideration. The 5250's didnt have this problem.
Dont enclose the SR's! They work best in free air.
Well thats all I can think of off the top of my head. If I think of any other wonderful tidbits Ill pass em on.