Speaker level high pass crossover

[joecool85]

My brother plays bass and just added a 2x10 cab to his setup.  He normally just uses his 1x15.  He likes to boost his EQ around the 30hz mark but the 2x10's hate that and distort badly.  So he has asked me to make a high pass crossover for him.  I'm thinking a ~10db of cut at 50hz should keep them from distorting.  We're going to try some different values to see what he likes best.  I just want to make sure I'm on the right track.

I used this site for the calculator: http://www.apicsllc.com/apics/Misc/filter2.html

And this one for some information: http://www.the12volt.com/caraudio/cross6db.asp

His 2x10 cab is 8ohms (not sure if it's 2x16ohm or 2x4ohm inside, but that doesn't matter).

From what I figure, if we use a 100uF cap in series with his cab it would give us:

3db cut at 200hz
6db cut at 100hz
12db cut @ 50hz
18db cut @ 25hz
24db cut @ 12.5hz

Is this right?  If so, I think something I might make a switchable box with a 47uF and 100uF caps with a parallel position giving 147uF for 3 distinct crossover points.

[joecool85]

This is what I had in mind for a schematic.  Switch up would be both caps in parallel (2 x 100uF), middle position would be just one cap (1 x 100uF) and last position would be 1 cap and a jumper that shorts it so effectively pass through signal.  Would this work?  Shouldn't be any harm "shorting" the cap to jumper across it for a "full signal" pass through right?

[LJN]

I'm pretty sure that the bigger the capacitor, the less distortion. don't know too much about the rest. but, the capacitors are easy, you can always go bigger until you get rid of the distortion, but I think that if you go too big, you could run into some problems.

[joecool85]

I'm pretty sure that the bigger the capacitor, the less distortion. don't know too much about the rest. but, the capacitors are easy, you can always go bigger until you get rid of the distortion, but I think that if you go too big, you could run into some problems.

That's sort of right.  The bigger the cap the less low frequency is allowed through (which if the speaker couldn't handle the low signals then what you said is right).  Too large of a cap and it won't change anything at all.  Too small of a cap and your speaker will sound like a horn driver.  Also, you are apparently suppose to use non-polar/bi-direction caps.

[DartPlayer170]

 

[gbono]

First order high pass filter(s) http://en.wikipedia.org/wiki/High-pass_filter

Use non-polar capacitor with sufficent working voltage. You might try experimenting with a higher order - Linkwitz-riley http://www.linkwitzlab.com/. Best solution is bi-amp since the filter (passive design) "interacts" with speaker response.

[DartPlayer170]

Is there any 'real' evidence that non-polar caps are better than electrolytics in signal path designs?

[phatt]

Hi Joe,, just a couple of points you might need to consider.

Is the box sealed or open backed?
If opened backed it's not going to do much.
If sealed back just fill it up with a pillow or like and see if it helps as this will make the cubic space smaller and raise the speaker Q.


I'd be shooting for a smaller cubic size as trying to make a brick wall at 30Hz is near to impossible via simple crossover ideas.

If he is using both the 15 and the 10's at the same time then you could use a simple Cap to limit low freq going to the 2x10. If so then start rolling off the 10's around 150hZ.

I'd be checking (with more knowledgeable folk) how the cap coupling of 2x10 from a big amp effects sability,, I believe some may haveproblems when cap coupled.

Phil.

[joecool85]

Hi Joe,, just a couple of points you might need to consider.

Is the box sealed or open backed?
If opened backed it's not going to do much.
If sealed back just fill it up with a pillow or like and see if it helps as this will make the cubic space smaller and raise the speaker Q.


I'd be shooting for a smaller cubic size as trying to make a brick wall at 30Hz is near to impossible via simple crossover ideas.

If he is using both the 15 and the 10's at the same time then you could use a simple Cap to limit low freq going to the 2x10. If so then start rolling off the 10's around 150hZ.

I'd be checking (with more knowledgeable folk) how the cap coupling of 2x10 from a big amp effects sability,, I believe some may haveproblems when cap coupled.

Phil.

I'm not sure on the cab design as I haven't seen it myself or researched it online.  He is using with the 15 at the same time and I am doing exactly as you said - using a simple cap to limit low frequency.  I am just using a 3 position switch to enable a couple options.  One will pass through, another will have one cap and the last will have both caps in parallel.  With one cap it will start the roll off at 200hz and with both it will start the roll off at 100hz.  Seems like we are on the same wavelength here.

[phatt]

Hi Joe,
        Wow a first, 2 musicians on the same wavelength  .

I run a small rotating speaker alongside my Laney SS Amp and needed to stop to much energy from driving the low wattage driver inside the cut down old Yamaha Organ roto system.

Can't remember exact value of the Cap (guessing it's 47uF BP) but I can run the main Amp at full power now with heaps of bass and the rotory speaker can keep up.
Phil.

[J M Fahey]

I would just ... ahem!! .... just not boost that 30Hz band.
There's no "music" there, only trouble, unless you have a gigantic (literally) bass cabinet.
What's the point of boosting something that later must be killed either with a highpass filter or an undersized box?
I don't get it.
It's a recipe for farting, and I'm not talking overeating chili con carne or bean burritos here

[joecool85]

Hi Joe,
        Wow a first, 2 musicians on the same wavelength  .

I run a small rotating speaker alongside my Laney SS Amp and needed to stop to much energy from driving the low wattage driver inside the cut down old Yamaha Organ roto system.

Can't remember exact value of the Cap (guessing it's 47uF BP) but I can run the main Amp at full power now with heaps of bass and the rotory speaker can keep up.
Phil.

Cool, good to hear it works for you.  This will be 100uF caps.  So, no cap, 100uF, 200uF for values.  My brother is excited.  After I build it I'll put up some pics and then once my brother tries it I'll let you know how he likes it.

[joecool85]

I would just ... ahem!! .... just not boost that 30Hz band.
There's no "music" there, only trouble, unless you have a gigantic (literally) bass cabinet.
What's the point of boosting something that later must be killed either with a highpass filter or an undersized box?
I don't get it.
It's a recipe for farting, and I'm not talking overeating chili con carne or bean burritos here

He boosts it because on a 5 string the "B" is 30.8hz and even on his 4 string it helps give him more "chunk".  I can verify this as I've heard it.  His 15" speaker loves it and it sounds great with his 70s/80s rock cover band.  It's just that the 10" can't keep up on the extreme lows and they do "fart" as you put it.  This filter should keep the flatulence to a minimum and let him keep the "chunky" sound on his 15".  Ideally he would bi-amp, but for now that isn't an option.

[J M Fahey]

Now you've hit the nail straight in the head.
Bi-amping would be great.
Let his 15" handle what it can and send the couple 10" what *they* can handle, courtesy of an LM3886 or similar.
He might mount it on the 2x10" cabinet itself. :tu:

[LJN]

Now you've hit the nail straight in the head.
Bi-amping would be great.
Let his 15" handle what it can and send the couple 10" what *they* can handle, courtesy of an LM3886 or similar.
He might mount it on the 2x10" cabinet itself. :tu:

I think that Juan is right. Go for it and let us know what happens.