Crossover slope???

[badstang123 10+ year member]

If I'm using a pre amp eq that has a electronic crossover with a 18db slope and then I also use the crossover on the amp which has a 12db slope am I essentially getting a 30db slope if they are crossed over at the same point? Whether I am or not, should I be using one or the other, or is both okay? Thanks.

- Justin

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[noob with an RS 10+ year member]

lol if youre using both crossovers u dont just add up the crossover slopes...

 

[badstang123 10+ year member]

That's why I'm asking. I have no idea how it would work. If you could give a rundown and some practical advice in this situation it would be appreciated.

 

[noob with an RS 10+ year member]

im sorry i forgot to tell you.. turn the xover on the amp all the way up (if its for the amp sub.. otherwise turn it all the way down if its an amp for speakers).. this will basically defeat the purpose of the crossover on the amp.. because i suggest you use one crossover which would be the electronic crossover.. or u can use the amps for the crossovers and turn the xovers off on the electronic crossover.. whatever you find suits your taste better..

 

[badstang123 10+ year member]

It's for my highs. Instead of turning the crossover all the way down, can't I take it off hpf and put it on full? I believe that bypasses the crossover altogether, thus leaving just the electronic crossover doing the work as you say is best right?

 

[noob with an RS 10+ year member]

exactly. set it on full.

 

[badstang123 10+ year member]

I set if up using just one crossover and I think it does sound better. Not a huge difference, but it just seems like a crisper and more natural tone (Could just be in my head, not sure). I like it though, thanks for the help.

 

[thch 10+ year member]

i've posted this reply a few times, so if you want larger details, you might want to search these forums.

it comes down to basic signal/systems. basically each filter has an effect on the magnitude and phase of the input signal.

thus if you have a 12dB/oct slope and a -18db/oct slope, you get a -30dB/oct slope.

but what about the fine print?

ok. when people make filters, they usually try to aim for something useful. lets take the example of 1st order lowpass filters that are cascaded. the first filter will give a -6dB/oct response at, say 50hz. the second will give a -6dB/oct response at 500hz.

for the above example, the filter has a -12dB/oct final slope, but still isn't too useful. the slope is only -6dB/oct in the 50-500hz band, which is probably the "important" band. the 500hz LPF really doesn't do much.

the second fine print is that people define the cutoff as the -3dB point. if filter A is -3dB @ 80hz, and filter B is -3dB @ 80hz, then the combined filter is -6dB @ 80hz. hmm. seems the cutoff point, as we've defined it, has moved.

when you comine filters you will get the high final slope, but the slope "of interest" probably won't be as steep. further, the "cutoff point" moves, and you probably won't know what the phase response of the combined filter will be. for these reasons, its better to use just one filter if possible.

edit -- as for sound, steep slopes don't equate to magically good sound. choose what works for the speakers ect...

 

[GhettoTaurus]

Crossover slopes actually do add up. They're multiplicative to the signal output, so its communitive. 6000 = 30 X 20 X 10 = 10 X 20 X 30 = 200 X 30 = 600 X 10 etc,

But you should probably only use 1 crossover unless you want a super steep rolloff for whatever reason.

 

[badstang123 10+ year member]

For speakers, I'd advise only using one crossover ...
For subwoofers, however, you may want to combine two to get a steeper slope if your crossovers have a relatively shallow roll-off (i.e. -12 dB/octave).

That is exactly what I did with the speakers (One crossover now, 18db slope). On the sub I am still debating what sound I like more. I'm leaning towards using the same setup. Just a single crossover with a 18db slope. Everything seems to sound a bit more full and natural now. Thank you all for your input and help.

And thch, I read some of the threads you've posted in. I found a lot of useful and interesting information. Your contributions to this site are definately appreciated.

- Justin

 

[noob with an RS 10+ year member]

Crossover slopes actually do add up.

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