Crossover points & such ques.

 

Bronze Member
Username: Alonzoub

Post Number: 23
Registered: Apr-10
Hi, so I read on these forums once about a style of choosing crossover points to allow the rolloff from the subwoofers lowpass and the mids highpass fill in an octave gap. I dont remember any details tho so if someone would like to explain to me how to choose the crossover points that would be excelent.

Also since the rears will be bridged on 2 channels to make a mono output and I would like to add a Lowpass filter to them so they dont play high frequencies, would I be able to simply build a small 3rd order lowpass and use the amp's built in highpass to create a jerryrigged bandpass?

A little background info:

I just finished purchasing every component of my new sound system for my car. Im taking my 100% stock 2005 Mazda 3 and adding a 10" woofer + monoamp, DLS components in the front and CDT mids in the rear powered by a 4 channel amp.

The 4-channel amp has variable crossover point between 30-500 Hz @ an 18dB/octave slope.

The Monoblock has a variable point between 45-200 Hz @ 18dB/octave slope.

Thanks in advance for any help.
 

Platinum Member
Username: Glasswolf

Post Number: 13761
Registered: Dec-03
http://www.glasswolf.net/papers/xosetting.html
 

Platinum Member
Username: Glasswolf

Post Number: 13762
Registered: Dec-03
http://www.glasswolf.net/papers/ampsettings.html
 

Bronze Member
Username: Alonzoub

Post Number: 25
Registered: Apr-10
That first post is exactly what I was talking about, thank you very much.

The crossover point for my DLS R5A components is @ 4500 Hz. Since the components filterbox doesnt use this rolloff fill method, should I set the lowpassfilter point for the CDT's in the rear to 4500Hz to match the fronts? And the R5A spec sheet didnt specify the slope used so should is a 3rd order ok?
 

Platinum Member
Username: Glasswolf

Post Number: 13766
Registered: Dec-03
if the components have their own crossover module, then just use that as it is.
if you want a HPF to cut bass from the midrange, try 100-125Hz for that, with a 2nd order 12dB/octave slope.

Subs can use a third order LPF, though. Most crossovers for components are 2nd order.

read this for rear fill setup
http://www.glasswolf.net/papers/rearfill.html
 

Bronze Member
Username: Alonzoub

Post Number: 26
Registered: Apr-10
I think you somewhat misunderstood. I AM going to use the crossover module that came with the DLS R5A components (fronts), but the CDT midrange (rear) speakers I bought did not come with crossovers. My question was can I use the amps HPF combined with a self built LPF to create a bandpass filter for the rear midrange speakers.

You suggested 100-125Hz on a 2nd order. The built in filters in my amp are 3rd order and there is no option for FULL signal so I have to use that filter.

Also I read your page about rear fill. In that you suggest using a 1st order LPF @ 2000Hz. What I was trying to ask In my previous post was, Since I know the components in the frontstage are filtered at 4500Hz, Should I also LPF the rear midrange speakers @ 4500Hz or would you stick to the 2000Hz 1st order filter you suggested in your rear fill page? Maybe somewhere in between?

I appreciate the assistance given so far, sorry If my post is a little confusing.
 

Platinum Member
Username: Glasswolf

Post Number: 13776
Registered: Dec-03
the rears are simply there for ambiance, and don't need to be matched to anything for the crossover points. you use a bandpass filter on those to cut the treble out of them, and to keep them from bottoming out. If you get anything above the vocal range in the rears, it'll draw the soundstage rearward and be distracting.
It'll also cause a float effect with the imaging if the signal to the rears is full stereo.
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