nad1967

So I have upgraded my front speakers to a 3-way in my 87 FC.
My question is concerning the 3-way passive crossovers. I have a 6" a 4" and tweeter. When I hook them all up the midrange all but dissappears from the 4". I bought a used kef 3-way crossover to run my memphis speakers. It has good parts on it but, do I need to upgrade the capacitors to a lower hz for the midrange?

Thanks

nad1967

How ridiculous of me to ask that question in an rx7 forum.

Icemark

what is the cut off and slope on the mid range cross over???

Typically for a 4" there should be little lower mid range and mostly upper (800Hz and up).

And perhaps a slightly more detailed title would have produced responses sooner.

nad1967

the crossover is a KEF KDN30, the crossovers are at 250hz, and 2.5khz. I am assuming that the midrange would be at 750hz. Any ideas?

Icemark

HMMM I am not familier with that Kef crossover. I didn't think that Kef was still making car stuff.

If the listed points are 250Hz and 2.5kHz then that is what the are cutting the 4" at.

There should be plenty of mid range there.

Are you sure that you havn't accidentally hooked the 4" up to the high output??? There are dedicated High, Mid, and low outputs on the crossover, correct???

nad1967

the 4" is connected correctly to the mid range part of the crossoover. The kef crossover is an older model, i'd say early 90's. Think i might need to buy new or different capacitors? Know where i can buy a cheap 3-way passive?

RX-7-Tobi

Hi,

you should only use crossovers for speakers only sold with them.
Every crossover is designed for special speakers.
They most times have not only the cut off functions, they do egalize speakers characteristics like peaks ect.
Sorry that I have to say that.

Tobias

nad1967

memphis does not sell a 3-way crossover. They do reccomend this

MS4 high-pass (250Hz) capacitor to be wired in series with the positive input lead to the crossover: 160uf (micro farad) capacitor.
MB6 (250 Hz) low-pass coil to be wired in series with the positive input to the speaker: 2.5 mHy (milli henry) coil. You could also add a 500uf (80Hz) capacitor in series along with the coil to create a band-pass for the 6", which would block low and high frequency information.

1. The above mentioned components will be needed if you are using two amp channels to power the pair of 6" and the MS4.
2. If you have separate amp channels, one pair for the 6", and another for the MS4, then you have other options.

any crossovers come to mind?

schexy1

just build a crossover yourself.

nad1967

well I spent the money to buy this kef crossover and I am wanting to know why the dang midrange is non existant. Could it be a bad capacitor? How can I check?

Icemark

Hook the 6" up to it and see if there is any decent output.

Try playing something with womens voices, or acoustic guitars. Both are very strong in the mid range area you say the X-over has.

And I disagree with RX-7-Tobi, the X-over seldom cares what speaker is hooked up today.

RX-7-Tobi

Hi Nad,

makes no sense to put a 500uF cap as a high-pass for the 6". It's only 6dB/oct. That big caps are not good quality or cost more than your whole car.
Use a air coil for the 6" with big dia wirining. Costs much but better sound than coils with ferrite or someting in it.

For the 4" use a big cap with the 160 uF. Parallel To that put a very high grade smaller maybe 5-10 uF. Improves sound very noticeable.
Where's the low-pass for the 4"???
I guess it's around 3 kHz.

What do they recommend for the tweeters?
I hope 12dB and not the 6dB/octave slope.

Does your 4" play without any crossover? Try it. At normal volumens you should not be able to damage something.

Cheers,
Tobias

nad1967

My previous setup listed above was e-mailed to me by memphis. The midrange plays but it is "soft" in comparison with every other range of music. I guess it's just how the crossovers are made. I would like to try a different setting. I think I will just buy a larger capacitor for the 4" to try it out.

RX-7-Tobi

Hi Nad,

is memphis a good firm?
The caps and coils sound like if they just took the formulas every rookie can use in speaker books.
Usually you will not get a flat freq response when dividing e.g. low- and high-pass at the same freq.
That's because of the speakers have no fix resitance with that the formulas work. They have a impedance, resisitance depending on the freq. E.g. if 4 ohms is the nominal imp. then the lowest resisance (DC res.) only should be slightly under that. Then follows a peak at the resonance freq. (fs), resistnace goes down again to become bigger becuase of the inductivity of the voice coil. And anothe rthing why good firms do experiment the best crossover freq. is because the speaker have no totally flat response.
What does memphis recommend for the tweeters? Usually they are much louder than the mids and they need two resistors to let them play as loud as the other speakers.

mfg
Tobias