wiring up a 2 way crossover

[bigjohn]

Hi all,

I want to try a crossover in my rig. I've not bought one yet... I'm just looking at manuals and stuff...

Rig will be an svtii preamp > crossover > power amp > 2 acme low b2s.

the preamp's outputs are 2 unbalanced 1/4 mono jacks, left and right.


All the crossovers I've looked at, apart from xlr balanced inputs, all seem to have 2 stereo inputs which then come out as 4 1/4 jacks. High & Low Freq for each channel.

Obviously this is to plug in subs and speakers for each channel.


However, I don't want / need that. And I don't want to have to plug in one cab as the high and one as the sub. What I want is to be able to use both channels on the crossover, one for each cab, and use the crossover to independently control which frequencies are getting into each cab.

But that leaves me with 4 unbalanced jacks going into the power amp. Or two balanced XLRs which will only have a a "high" or "low" output signal.

Any ideas?


Cheers

John

[Huge Hands]

Depends on the crossover I guess.

Some of the simpler ones may have fixed, or variable "High" and "Low" outputs but some of the clever ones will give you four separate outputs that can all be high, all be low, some high, some low, some mid - blah blah blah, the world is your adjustable oyster.

Still not 100% sure of what you're trying to achieve from you first post? Not a top and a sub, but different frequency range to each cab?

Edited June 18, 2009 by Huge Hands

[Mr. Foxen]

Run the lows to both B2s and have another amp/;cab for higher stuff, like a guitar combo or something.

[bigjohn]

[quote name='Huge Hands' post='517314' date='Jun 18 2009, 12:38 PM']Depends on the crossover I guess.

Some of the simpler ones may have fixed, or variable "High" and "Low" outputs but some of the clever ones will give you four separate outputs that can all be high, all be low, some high, some low, some mid - blah blah blah, the world is your adjustable oyster.

Still not 100% sure of what you're trying to achieve from you first post? Not a top and a sub, but different frequency range to each cab?[/quote]

Ah ok.

Well, ideally I'd like a crossover that when I put 2 1/4" mono jacks in, I get 2 1/4" jacks out. But I can't seem to find one.

I like to be able to filter out the top and bottom ends on each channel, for each cab independently. So it could be used as a top and a sub if I set the crossover like that, or I could set them to be the same. Or I could use the bottom cab more full range, and use the top cab for middle. So yeah, not specifically a top and a sub, but a different range to each cab.

[bigjohn]

[quote name='Mr. Foxen' post='517316' date='Jun 18 2009, 12:42 PM']Run the lows to both B2s and have another amp/;cab for higher stuff, like a guitar combo or something.[/quote]

I stuggle to get everthing in the car as it is!

[Stewart]

OK, assuming one channel, feeding one cab, you can choose 2-way mode and have either the high or low output.

If you set the frequency to 100 Hz, you'd get deep rumbly sound from the low out
You'd get very bottom-light output from the high-out.

If you set the frequency to 40Hz, you'd get almost nothing from the low output - the high output would have the entire audio range except 40Hz and below (which aren't real notes on a 4 string) - this is possibly what you'll be after...

If you select 3-way mode (and have sufficient range on the controls, then you could use the mid output to have nothing below 40Hz as previously, but also nothing above (for example) 4000Hz)

The stereo/twin channels mean that you can have differing frequencies for each amp channel/cab, but you won't be able to have 2 way and three way simultaneously (on any that I've encountered)

Note also that you do not want to be changing frequencies on the fly while the amp is on - you'll get very surprising noises...

Does that make sense?

[alexclaber]

Don't do it!

If you want to be able to mess with their tone independently then I'd use a stereo graphic EQ but I can't think why you'd want to. As soon as you stop the cabs working in unison you're cutting your sensitivity and power handling significantly and once you get more than about 10' away the wavefronts will be pretty much combined whatever you do.

Alex

[Stewart]

I agree absolutely - having different frequencies set for the two cabs is a very bad idea

[escholl]

[quote name='alexclaber' post='517366' date='Jun 18 2009, 01:37 PM']Don't do it!

If you want to be able to mess with their tone independently then I'd use a stereo graphic EQ but I can't think why you'd want to. As soon as you stop the cabs working in unison you're cutting your sensitivity and power handling significantly and once you get more than about 10' away the wavefronts will be pretty much combined whatever you do.

Alex[/quote]

+1, it would make much more sense to go with the traditional biamp setup.

[Bill Fitzmaurice]

[quote name='Stewart' post='517371' date='Jun 18 2009, 08:40 AM']I agree absolutely - having different frequencies set for the two cabs is a very bad idea[/quote]
+1. Bi-amping is only useful with cabs that are specifically engineered to operate within different frequency bandwidths, not with cabs that cover the same bandwidth.

[bigjohn]

Okay... Okay! Thanks for the advice.

But the crossover idea would still work if I wanted to stop low and high frequencies getting to the cabs (using the same frequencies for both cabs)?

Or am I best off using an EQ?


Basically, what I want is a sweepable high and low pass filter. I think

[Stewart]

Yes - you will need a 3-way crossover.

[bigjohn]

[quote name='Stewart' post='517442' date='Jun 18 2009, 03:09 PM']Yes - you will need a 3-way crossover.[/quote]


Ok. So say for instance I have a peavey vsx crossover... it does 2 and 3 way.

The face plate is as such...



The back plate is as such...




How would it work in terms of the controls? And how would I connect the outputs to a 2 channel power amp?

Edited June 18, 2009 by bigjohn

[Huge Hands]

[quote name='Stewart' post='517442' date='Jun 18 2009, 03:09 PM']Yes - you will need a 3-way crossover.[/quote]

Ummm - not necessarily, I don't think. As I said earlier, you could get a more programmable DSP unit that has filters on each output. 3 way would just mean that on a "stereo" input unit you'd have six outputs instead of four. However, it's been a little while since I've been in the game so not sure what's on the market. What I was saying earlier is that on a versatile unit you could set up two outputs to give you what you need and ignore the other two.

I'd tend to agree with Alex - if you just want a LPF and HPF I'd look into an EQ unit - you may then get a couple of extra bands to filter in the middle too and possibly cheaper than a crossover, depending on functionality.

[Huge Hands]

[quote name='bigjohn' post='517460' date='Jun 18 2009, 03:27 PM']Ok. So say for instance I have a peavey vsx crossover... it does 2 and 3 way.

How would it work in terms of the controls? And how would I connect the outputs to a 2 channel power amp?[/quote]

If you're using this unit, although it has a adjustable crossover frequency(ies), it has fixed H, M and L bands. It wouldn't do what you want it to do becuase it deals with each section on a separate output.

[bigjohn]

[quote name='Huge Hands' post='517467' date='Jun 18 2009, 03:36 PM']If you're using this unit, although it has a adjustable crossover frequency(ies), it has fixed H, M and L bands. It wouldn't do what you want it to do becuase it deals with each section on a separate output.[/quote]


I thought as much.

Does anyone know of one that'll output into 2 channels?

[Huge Hands]

[quote name='bigjohn' post='517473' date='Jun 18 2009, 03:40 PM']I thought as much.

Does anyone know of one that'll output into 2 channels?[/quote]

The problem you have (from reading into your intentions) is that you are after the top curve of the High portion, and the low curve of the Low portion [b]on the same output.[/b] You then want this mirrored onto a second output for your other cab. On a fixed crossover like the one you mention, the two curves never meet as they are always on separate outputs. Some higher end DSP crossovers (I'm specifically thinking of PA stuff such as XTA as that's what I know) can be programmed to do what you're asking as both ends of the filter are programmable.

However, what you are actually asking is for the crosover to work as an EQ filter. A lot of graphics have HPF and LPF controls/switches on them and give you all the EQ in between.

Edited June 18, 2009 by Huge Hands

[Stewart]

Doesn't look like you can (in the normal way)- it's designed to be used as a crossover in traditional 2-way designs (regardless of the 2/3way labelling) - you can't choose a frequency lower than 1kHz.

You need a 3way crossover (Low/Mid/High) where you can set the low frequency cutoff where you want it (40-50Hz probably)

However - you *could* use the 40Hz rolloff (not variable frequency though...) as your low frequency cutoff, and then set the high frequency cutoff with the frequency knob. You would leave the unit in 2way mode and just use one channel. Using Channel 1, just stick the input into INPUT and take the output from CH1 LF output.

That unit is old and strange though (18dB/octave, though the 40Hz rolloff is 24) - possibly noisy and/or unreliable... best bet - buy something else!

[bigjohn]

[quote name='Huge Hands' post='517481' date='Jun 18 2009, 03:47 PM']The problem you have (from reading into your intentions) is that you are after the top curve of the High portion, and the low curve of the Low portion [b]on the same output.[/b] You then want this mirrored onto a second output for your other cab. On a fixed crossover like the one you mention, the two curves never meet as they are always on separate outputs. Some higher end DSP crossovers (I'm specifically thinking of PA stuff such as XTA as that's what I know) can be programmed to do what you're asking as both ends of the filter are programmable.

However, what you are actually asking is for the crosover to work as an EQ filter. A lot of graphics have HPF and LPF controls/switches on them and give you all the EQ in between.[/quote]


I can't find any crossovers that don't output different bands on different outputs. Thus my original confusion.

I'd be happy with two knobs, one a sweepable high pass, and one a sweepable low pass. I don't need any other EQ as my pre-amp has low, mid (with a mid range freq selector) treble, and a graphic EQ on it. That's plenty.

[Huge Hands]

I suppose you could use the "MID" band on your Peavey in mono mode which should mean that both the crossover frequencies would do this. It does seem a bit crude though, and you would have to parallel the output elsewhere (your amp?) to make two mirrored outs but they wouldn't work independently. It doesn't appear clear on your diagram which out would be the mid out in 3 way mode.

It almost seems like trying to use a sledgehammer to crack a walnut....

Maybe there are some boxes on the market (even a pedal) that just do what you're after? Not too much of a product catalogue index myself I'm afraid.

Edited June 18, 2009 by Huge Hands

[bigjohn]

[quote name='Huge Hands' post='517575' date='Jun 18 2009, 04:59 PM']I suppose you could use the "MID" band on your Peavey in mono mode which should mean that both the crossover frequencies would do this. It does seem a bit crude though, and you would have to parallel the output elsewhere (your amp?) to make two mirrored outs but they wouldn't work independently. It doesn't appear clear on your diagram which out would be the mid out in 3 way mode.

It almost seems like trying to use a sledgehammer to crack a walnut....

Maybe there are some boxes on the market (even a pedal) that just do what you're after? Not too much of a product catalogue index myself I'm afraid.[/quote]


I don't have the peavey, I just picked that one out as an example.


Thanks for all the replies... it does seem like there's no sensible solution to what I want to do... which makes me think I'm not being very sensible...

There is this thing I've found...


[url="http://www.kmraudio.com/catalogue/product_info.php/manufacturers_id/77/products_id/1269?osCsid=e50435c308b954ae8b0d4232792680af"]http://www.kmraudio.com/catalogue/product_...b0d4232792680af[/url]

That does what I want but it's for a studio console. And it's errr... £500!

Edited June 18, 2009 by bigjohn

[alexclaber]

[quote name='bigjohn' post='517565' date='Jun 18 2009, 04:48 PM']I'd be happy with two knobs, one a sweepable high pass, and one a sweepable low pass. I don't need any other EQ as my pre-amp has low, mid (with a mid range freq selector) treble, and a graphic EQ on it. That's plenty.[/quote]

[url="http://www.alembic.com/prod/sf2.html"]http://www.alembic.com/prod/sf2.html[/url]

There has to be quite a bit of irony in owning a pair of the widest bandwidth cabs on the market but then wanting to bandpass them!

What frequencies are you looking to have the filters set at?

Alex

[bigjohn]

[quote name='alexclaber' post='517592' date='Jun 18 2009, 05:12 PM'][url="http://www.alembic.com/prod/sf2.html"]http://www.alembic.com/prod/sf2.html[/url]

There has to be quite a bit of irony in owning a pair of the widest bandwidth cabs on the market but then wanting to bandpass them!

What frequencies are you looking to have the filters set at?

Alex[/quote]


I am Mr Irony sometimes

Well I was going to start by cutting out all the <40hz.

That Alembic thing does look interesting but it's a bit pricey innit!

[alexclaber]

[quote name='bigjohn' post='517607' date='Jun 18 2009, 05:23 PM']I am Mr Irony sometimes

Well I was going to start by cutting out all the <40hz.

That Alembic thing does look interesting but it's a bit pricey innit![/quote]

An easier solution might be to find a power amp with a highpass filter in - or use an fmod between your preamp and power amp. And then roll the tone knob off on your bass for the lowpass requirements.

[url="http://store.hlabs.com/pk4/store.pl?view_product=10"]http://store.hlabs.com/pk4/store.pl?view_product=10[/url]

The Superfilter is hideously expensive for what it does. Cheap compared to their basses though!

Alex

[Stewart]

You won't get a cheaper (or arguably better) solution than a linkwitz-riley filter crossover.

If you want to have both low and high frequencies filtered you would simply use the Mid output of a 3-way crossover (think DBX, Behringer, Samson etc etc)

The Low/Mid frequency control would be set to (example) 50 Hz, the Mid/High to (example) 3kHz. The Mid output would then consist of audio between 50 Hz and 3kHz. Nothing needs to be connected to Low output or High output, you just use the Mid.

You don't need to use two channels, you can feed several amps from any output.