Crossover frequency for MM 6501

rebos123

I have a set of mm 6501 in the front door of my Mazda 3 and am running active through a JBL MS-8 processor. My question is what frequency should I crossover between the mid/woofer and tweeter?

goosonano

frequency or angular velocity does not change frequency is an integer or a number (angle l/r).

rebos123

hmmm. Maybe I should rephrase my question.

I am using a JBL MS-8 sound processor in my Mazda 3. The MS-8 has the capability to specify what the crossover frequency can be between two drivers in a 2-way active setup. I have installed a set of mm 6501 components in my front door (6.5 inch woofer in the door, tweeter in the sail panel) and I am not using the stock passive crossover.
My question is this: What frequency should I set the high pass crossover between the woofer and the tweeter? I could not find any specs on line as to what the passive crossover from polk is designed at.

MacLeod

Generally 4 KHz works best at least for a starting point.

rebos123

thanks - I will use that.

Vital

IIRC when i called Polk with that same quastion they said cut off for MM's passive x-over was at 3,200.
Call Polk to verify but you don't have to follow that 100%.
See what point sounds better in your car/install.

thiggy

I'm looking for the same info. May try to call at work tomorrow. It's the only piece of the puzzle that's missing right now and I'm shooting for a sunday install.

thiggy

Called support today and received an email response to use 3kHz w/ 12-18dB slope.

MacLeod

Hmmm, thats an awful shallow slope for tweeters. Youd be getting a lot of upper midrange coming thru with that, especially at 12 db/oct.

Well since youve got an active crossover, might as well try them all. Also try the mids at 2KHz @ 12 db/oct and the tweeters at 4KHz @ 12 db/oct. Depending on the install and location, that can work. Im gonna say tho that both mid and tweet cut at 4 KHz @ 24 db/oct will likely sound the best.

arun1963

Polk will suggest slopes based on the passives slope. I think most passive xovers use shallow slopes. Reason could be, 99% of the buyers use components as a plug and play application with pratically 0 dsp. That and the manufacturers belief in the 'blend theory'. Shallow slopes for better blend.

The balance 1% are going to ditch the passive anyways and will have enough dsp to know that its balance at the xover points and with whats above and below, that counts. Unlikely that you will get here with shallow slopes. Steeper slopes give much better tonality and imaging.

I wonder how my car would sound if I just kept the steep slopes and turned off everything else ie TA / Eq etc..........I'll let you know this evening. Mac probably already knows the answer.....lol

arun1963

arun1963 wrote: »

I wonder how my car would sound if I just kept the steep slopes and turned off everything else ie TA / Eq etc..........I'll let you know this evening. Mac probably already knows the answer.....lol

Without the TA and the eq, it sounds bad both ways

MacLeod

arun1963 wrote: »

Polk will suggest slopes based on the passives slope. I think most passive xovers use shallow slopes. Reason could be, 99% of the buyers use components as a plug and play application with pratically 0 dsp. That and the manufacturers belief in the 'blend theory'. Shallow slopes for better blend.

I dont know this for a fact but my theory is that manufacturers come up with their crossover points when designing speakers on the sound board. When you get the speakers in the car and one mid is 90 degrees off axsi while the other is 20 and the tweeters are mounted 3-4 feet away and also at different axis, thats gotta change how theyll respond.

arun1963

That's a valid point. It's very easy to imagine companies testing car ausio speakers on boards in a far field environment

thiggy

MacLeod wrote: »

Hmmm, thats an awful shallow slope for tweeters. Youd be getting a lot of upper midrange coming thru with that, especially at 12 db/oct.

Well since youve got an active crossover, might as well try them all. Also try the mids at 2KHz @ 12 db/oct and the tweeters at 4KHz @ 12 db/oct. Depending on the install and location, that can work. Im gonna say tho that both mid and tweet cut at 4 KHz @ 24 db/oct will likely sound the best.

Roger that, I was planning on going with the 24 db/oct, I just want to be sure not send anything lower than the tweets will like. I'll probably try 4k to start and go from there. Just need the parts for my window so I can finish up the door and I'm in business. I'll post up the results.

MacLeod

What Im wondering is if that is the crossover point or the cutoff point. If you cutoff the mids at 2K at 24 db and the tweeters at 4K at 24 db, your crossover point is where the two meet at equal levels which would be something like 2.8K. Cause the crossover point of the SR's is 3.1K but the tweeters are cut off near 6.3 and the mids below 2K according to the Car Audio and Electronics magazine test on them. They ran a frequency response graph of just the mid and just the tweeter so you could see where they were rolling off independently.

arun1963

Well, the white paper on the SR 6.5's say that the xover frequency is 3100 hz with the mid cut at 12 db and the tweets at 18db. It doesn't say if Both drivers are cut at 3.1 or if 3.1 is the balance point based on staggered points. I've run the SR's actively x'd at 3.15 @ 24 db slope. I always felt that this was a bit lower than what the tweet could actually handle.

MacLeod

I know theyre not cut at 3.1. Thats just it, I cant find that link on the CA&E site (can find the review but not the freq response graph) but it plainly shows the tweeter starts rolling off around 6K and the mid at under 2. Ill keep digging and maybe I can find it somewhere.

Vital

Since this thread went into SRs - what effect will SR5250 passive x-over will have on a set of SR65000 speakers?

MacLeod

Probably negative cause the mids are cut off higher as is the tweeters.