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Raise crossover point?

David Jayne

David Jayne

Jan 16, 2006
16,337
8,096
Brookfield, CT
#1
I'd like to know how to modify the crossover in my UL310. To my ears, there is too much Hi Mid information reaching the tweeter, which makes it quack like a duck. Multiple amps, multiple basses- it's always there unless I dial back the tweeter level, but then there's no treble, so I want to modify the filter cutoff point, raising it. Not sure by how much yet.
Anyone willing to help me on this? I can supply pictures of the crossover but not schematics. Tks, Dave
 
#2
You may not need to raise the crossover point but give it a steeper rolloff like a 3rd or 4th order. Going to need the model of tweeter, any specs you can find, part values of the filter that's on there now. Plenty of guys here who could help out.

This site http://www.diyaudioandvideo.com/ has a calulator to find out the right part values for what you're trying to do. The impedance curve of the tweet that's in there now would be of great help.
 
#3
If you can find it in a search there's an old thread on here about a tweeter mod to an avatar410. In that case there was a gaping hole in response where the 10's rolled off but the tweeter hadn't picked up yet. Solution was to replace it with a tweeter that could handle a lower crossover point, lower the filter point to take up the gap and put a steep rolloff on it to keep the mids out of the tweet. Maybe not the same problem you're having but the same principles will apply to fix it. Going to have to reverse engineer your current filter to see where you are now and where to go with it from there. You're going to have to take it out and list the part values on it and in what order they're laid out. Hopefully one of the experts will chime in here.
 
#4
dmusic148 said:
I'd like to know how to modify the crossover in my UL310. To my ears, there is too much Hi Mid information reaching the tweeter, which makes it quack like a duck. Multiple amps, multiple basses- it's always there unless I dial back the tweeter level, but then there's no treble, so I want to modify the filter cutoff point, raising it. Not sure by how much yet.
Anyone willing to help me on this? I can supply pictures of the crossover but not schematics. Tks, Dave
Click to expand...

Wow. The Epi tweeter and crossover is considered to be among the most airy and beautiful sounding on the market. From what I understand, and from what my ears hear, the Epi crossover is very high, and has a very steep drop off. Hence, only the very upper treble comes through that tweeter.

Most find a setting between 9 and 11 o'clock (depending on how much high end sizzle you want) is optimal with this circuit. I hear NO upper mids, or even lower treble coming out of that circuit (versus, for example, the Bergantino AE's, where the crossover seems to be set much lower, with a gentler roll-off).

Something else going on here. What other cabs are you comparing this to?

Edit: Not saying you aren't hearing what you are hearing, but rather that the crossover point and slope would not be your issue, since again to my ears, the Epi tweeter has one of the higher crossover points and steepest drop-off slope compared to most other two way cabs I've played or owned (which is a lot of them!).
 
#5
OK, here's what I've got. I assume the yellow things are caps. Large one reads '6.8J / 250v', small reads '2.7J / 250v.' Don't know if that's enough info(values). If not I'll take it apart so I can read them with a meter. Also don't know the resistance of the coil(choke?). Again, if needed I'll disconnect one end so I can measure it. If needed I'll try to draw a schematic, but it looks pretty simple.
My meter reads 7ohms at the tweeter(disconnected). Thanks guys/gals.
DSC01140.jpg

DSC01141.jpg
 
#6
KJung said:
Wow. The Epi tweeter and crossover is considered to be among the most airy and beautiful sounding on the market. From what I understand, and from what my ears hear, the Epi crossover is very high, and has a very steep drop off. Hence, only the very upper treble comes through that tweeter.

Most find a setting between 9 and 11 o'clock (depending on how much high end sizzle you want) is optimal with this circuit. I hear NO upper mids, or even lower treble coming out of that circuit (versus, for example, the Bergantino AE's, where the crossover seems to be set much lower, with a gentler roll-off).

Something else going on here. What other cabs are you comparing this to?

Edit: Not saying you aren't hearing what you are hearing, but rather that the crossover point and slope would not be your issue, since again to my ears, the Epi tweeter has one of the higher crossover points and steepest drop-off slope compared to most other two way cabs I've played or owned (which is a lot of them!).
Click to expand...

There could be something else going on, voicing of the other speakers maybe but he says the "quack" he doesn't like goes away when he rolls the tweeter off, problem is it takes away the whole top end and not just the offending sound.
 
#7
will33 said:
There could be something else going on, voicing of the other speakers maybe but he says the "quack" he doesn't like goes away when he rolls the tweeter off, problem is it takes away the whole top end and not just the offending sound.
Click to expand...

+1 That's what is so strange. The Epi tweeter sits WAY on top of those drivers versus other cabs.

I believe Passinwind (our resident crossover guru) dug into the Epi crossover and posted that it's a very high order 'low pass' type design with a steep roll-off slope, but I can't quite remember.

Maybe he will pop over and give his 2 cents on this.
 
#9
dmusic148 said:
I know, Ken. I've read that it's airy and whatnot. Not to me. I'm comparing it to my trusty old Goliaths, which sound much, much better IMO.
Click to expand...

Ah.. that's EXACTLY what I was guessing:smug: Yes, compared to the uber sizzly and metalic sounding (IMO and IME) top end of the old Goliaths (super upper, upper treble sizzle), the Epi circuit would sound a bit more meaty.

I liked the Goliath tweeter/crossover also (even though they are universally hated), but have moved away from that 'pure upper treble click' type of metal horn top end.

You comments make sense to me now. Good luck on the modification. If you can't make it work, the new GoLight series from SWR might be the way to go.... that soon to be released Marcus Miller sealed 410 looks very cool, and is only 55 pounds.
 
#10
Judging by the size of the caps that's a 3rd order high-pass at about 5kHz. That's about average, and the result is an octave wide response hole between the useful high end of the woofers, perhaps 2.5kHz, and the lowermost extension of the tweeter. That's typical of woofer/tweeter cabs. Going to a higher passband would not be an improvement; to get what you're looking for you need to use a tweeter that crosses over an octave lower. Your 'quack' is likely the result of trying to get out of the speaker content in that 2.5kHz-5kHz octave that it's not capable of delivering.
 
#11
billfitzmaurice said:
Judging by the size of the caps that's a 3rd order high-pass at about 5kHz. That's about average, and the result is an octave wide response hole between the useful high end of the woofers, perhaps 2.5kHz, and the lowermost extension of the tweeter. That's typical of woofer/tweeter cabs. Going to a higher passband would not be an improvement; to get what you're looking for you need to use a tweeter that crosses over an octave lower.
Click to expand...

I always mix up those hi pass and low pass terms!

Yes, that's basically what I remember from Passinwind (I think he estimated 6K, but can't quite remember) and what I hear with my Epi's, a relatively high crossover point with a steep drop-off, leaving that nice dip in the upper mids that sounds so good for certain tone goals (i.e., it automatically removes some of that upper mid 'gank and clank' from your tone, resulting in what many describe as a beautiful airy top end that kind of sits on top of the drivers. It's a beautiful sounding crossover and voicing for many of us, and per my post above, only SWR Goliath lovers would hear it as 'having too much upper mid content:D

IMO, being a former Goliath user and also gigging various Epi's for years, his 'quack' is the exact opposite of what you describe. The 'hole' between the top end of the woofers and the tweeter on the Goliath is about a mile wide, versus the much smaller frequency distance of the Epi (which is still quite a bit more extreme than many others I've heard).
 
#12
You are correct, Bill- some of the offending quack is coming from the speakers, but the vast majority is coming from the tweeter. I can zero in(roughly) on these frequencies using the EQ on my amp. Boosting Hi Mid control and sweeping the frequency center, I land here, the quack zone. The range of the control is 700hz to 6kHz, so this would be, what, 2-3K?
DSC01143.jpg
 
#13
Seems like it would be around 3+K (if my 'knob position to octave' ratio is right... which it might not be!). The MB mid control Q seems relatively wide to me, so I'm pretty sure (again, compared to the Goliath) that you are hearing IMO the very low end of the tweeter response (as you posted in your OP), since the Epi has more 'low treble' coming through that tweeter than the Goliath.
 
#14
See any burnt parts? Is there a bulb fuse? Maybe check the actual tweeter, sometimes when they blow they'll sound harsh, crappy and not necessarily be silent. Has the L-pad ever got really hot? As you say it's always been like this though they may all be fine
 
#16
alexclaber said:
Yep, looks like about 3kHz. Could be the tweeter distorting when hit by the 3kHz output (depending on how steep the highpass filter really is in practice), could be the break-up modes of the woofer.

Alex
Click to expand...

If it's a 3rd order 6kHz HP, as has been guesstimated by others, then it would be -18db at 3kHz. It's really doubtfull that the woofer makes it past 2-2.5k before dropping off at about the same 18-24 db/octive naturally. I don't see how 3k could be the problem. Makes more sense--if I were to guess--that the woofer has a big spike around 2-2.5 kHz (many go up as much as 10db) and this is the problem. But that theory doesn't square with this:

dmusic148 said:
...makes it quack like a duck...unless I dial back the tweeter level, but then there's no treble...
Click to expand...
 
#17
Unless I'm mistaken, the Q of that control is probably a full octave or at least a half-octave, so cutting 3khz probably doesn't mean precisely a cut at 3khz - it's going to be a curve extending out from 3khz in both directions, right?

So the offending frequencies might be closer to 4khz even or higher.

Also, if that MF-high frequency setting is evenly distributed, it's looking a lot closer to 4khz that it's set at to me than 3khz. Assuming each "notch" on the EQ dial is exactly the same it's around 4.3khz. Not sure though.
 
#18
dmusic148 said:
Also don't know the resistance of the coil(choke?). Again, if needed I'll disconnect one end so I can measure it.
Click to expand...

The choke's inductance is its most important property. You won't be able to measure that without expensive test equipment. You'll have better luck finding numbers printed somewhere on the choke assembly.
 

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