Where should I cross MM6501?

rod wayne

Does anyone have any suggestions where to crossover mids and tweets on polk mm6501 in an active setup?

pentoncm

I highly recommend crossing at 4kHz. Many people like crossing low but the fact is that unless you have an expensive set of high end tweeters, crossing in the 2 to 2.5kHz area will significantly increase distortion and reduce power handling.

I would try out 3.15kHz and 4kHz, see which one you prefer. Are you time aligning your drivers? If you can time align and can do it well then I would say crossing at 3.15 would be ok. If you aren't good at time aligning yet or don't have the ability stay with 4kHz. Why? Because as you cross lower you are splitting the imaging information between another set of drivers messing things up. By keeping everything in one driver up to 4kHz, most of the imaging will be coming from the woofer, and then the tweeter will produce a little bit of imaging but mostly contribute to stage height and definition and clarity. If you crossed at 2kHz, then you split your imaging in half leading to a really messy imaging.

There seems to be a widespread fear of running mids above 3kHz(referring to other car audio forums). You want to run your mids decently high. The fact is the MM6501's do fine off axis I would say all the way up to at least 6kHz. How do I know this? Mine are in my door panels and my near vs. far responses in the 4 - 6kHz are within 2db of each other, that is pretty good for a 6.5 inch mid.

Bottom line I recommend comparing 3kHz through 5kHz and see what you like best. If you can use Linkwitz Riley Filters, Butterworth causes a nasty 3db peak at the crossover point.

pentoncm

Yes I know that some manufacturers do (Hertz comes to mind). But there are many examples of manufacturers not going under 3kHz. There is a benefit with going with a point source solution instead of splitting things between the woofer and tweeter. If it was fine to cross at 2 or 2.5kHz then more companies would do it. Distortion is a serious issue by running your tweeters down to 2kHz. Even if you set them at 24db per octave they will still be outputting quite a deal of information down to even 1kHz which is really low for a tweeter.

Morel crosses at 3.8kHz
HAT crosses high usually around 5 to 6kHz
Scanspeak at 3kHz
Polk crosses between 3kHz and 4kHz on their sets.
DLS Gothia uses crossover points ranging from 4 to 5.5 kHz

Scott Buwalda wrote a nice little piece on the Hybrid forums explaining his views on crossing no lower than 4kHz. I'm not saying that he is the master of car audio but he supplies some good info and a valid point of view.

arun1963

Most passive xovers on car components split a two way in the 2-3khz range, most not all. This has more to do with managing the beaming of a typical 6.5" MB driver `2-2.5khz. Since most MB are mounted in doors, hence typical on/off axis mounting and the beaming issue is accentuated. Allowing the tweets to play low is a kind of band aid for this problem.

The typical 0.75" tweet that comes with mid priced components, is not really suited to playing the 2-3khz range. The 0.75" tweet cut at say 2.5khz on a 12db slope will be playing 1.25khz loud enough for its effect to be felt and heard in the overall sound. Chances are this setup would make the 1.5-3khz range really harsh.

With a 1.25" tweet thats better geared to playing low, 2khz is about the lowest I would go. 3-4khz seems like a good place to start. The tweets on the MM can get harsh pretty quick if played too low. Where you lace the drivers and the level of dsp will also play a part.

Pointless discussing how home audio speakers are set up cause the environment and placements are totally different.

$0.02

pentoncm

SR and LSi use ring radiators that are completely different from domes. The entire diaphragm is supported with a RR tweeter reducing deformation and destortion. Because of this most radiators can be crossed lower and maintain good SQ. The whole thing regarding distortion relates to the environment you are in. In far field like in home theater where you can be 8 to 15 feet away from the speakers and the dispersion is much greater. Or in a car you have a near field where those tweeters are really close to your face and you are much more susceptible to hearing their flaws.

I agree crossing the average tweeter low won't destroy it but it can sound quite nasty on cheap set of domes with a high resonance point.