Crossover considerations
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Posted on Jun 18, 2011 02:34 am
GCT
Member Since: May 14, 2011
Hi
We're getting a sound system together for events. So far we have
4 subs JBL 2241 18 600w
2 JBL 2445 horns
Complete Beyma 1200w passive xover 4x15 + 2 Horns
2s,3s,4m way crossover.
I was thinking 3 way active using the 4 Beyma 15's as mids removing the passives and Beyma horns. What xover points would be good?
On quick listening the JBLs go nice together 2 way active 600Hz xover. I could just add the 2 systems together. Active JBL 2 way plus passive beyma 2 way. Is there a lot to gain going 3 or even 4 way?
Any thoughts would be appreciated
Thanks
GCT
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Jun 18, 2011 10:40 am Three way would be the way to go. The benefit would be more power going to just that driver. Giving you more head room.
As for the crossover points. That is going to take a little tweaking here and there to get it just right. A two way crossover is easy. You just set the points between the subs and tops and then your done. But, with a three way, it takes a little more fineness. A the points between the 15" and horn with determine directionality, pattern, phase, and clarity.
600hz is really low for a horn. And could cause damage to the horn. As there are not designed to move that far to produce anything really lower then 1khz.
Typical is somewhere in the range of 1.2khz or 2khz. But, with different slopes for the HPF. (I'm not sure if your crossover allows for different slopes. It maybe fixed.)
Now, I rather prefer the Turbosound theory of crossover points. And that is to move the point a little higher than most. This keeps all of the vocal range in what we call the paper (Just the 15") Which makes them standout a little more. Turbosound will cross the mid and highs somewhere in the 4khz range.
Now in doing so, your horns will be more directional. But, sometimes a tighter pattern is rather nice to have. Also, you may have to run the 15" in flip polarity. As with most three way systems, the mids will rise up, or be pulled down in direction due to time alignment, and summed energy points of the other two drivers. (Subs and highs) So try flipping the polarity while tweaking your system. See what sounds the best, and try to listen to where the mid range is. when doing so. You might find that it is stronger in a particular area in normal phase, and gone in the same area when flipped.
For your subs, Try either 80hz, 100hz, or 125hz. Playing around with the point a little will do the same thing for the bass, as it will the horn. It will tighten up the sound, and will widen or narrow the subs a little. Plus it can remove some standing waves in a room. But, not always.
So, try this for your overall settings and see what you think. 80hz for the sub. 100hz to 2.5khz on the 15", 4khz and on up to the horn. Run the 15" on a negative polarity. See what you think of this. If it's not to your liking, I'll help you tweak it a bit until you do.
Jun 18, 2011 10:46 am One thing that I failed to mention is that I would run the horns down about -6 to about -10 dB from the 15", and the 15's down about -3db.
this will give it a flatter sound, and help protect the horn in a high SPL situation.
GCTMember
Since: May 14, 2011
Jun 18, 2011 01:18 pm Thanks Rob.
That's the info I have been looking for. The crossover is the Behringer CX 3400 so it's only LR with a CD EQ setting and time alignment for the subs and phase buttons on each band.
I'll get back to you as soon as I've tried it; I'll need to put switches on the mids to remove the passives as they are borrowed; hopefully tomorrow I'll try something.
Many thanks.
GCT
GCTMember
Since: May 14, 2011
Jun 18, 2011 01:49 pm So we have:
1200w of JBL subs
500w of Beyma mids
150w of JBL top
per side leaving the Beyma horns out.
GCTMember
Since: May 14, 2011
Jun 18, 2011 06:23 pm OK Sounds good. Played with the controls as you said at low volume and got the idea.
When you talk of dBs I am thinking SPL meter reading while playing back pink noise?
Do the horns need a protection condenser in series tuned to lowest crossover permissible?
Cheers
GCT
Jun 18, 2011 06:34 pm I'm afraid that I don't know what you're asking about for the horns?
If you're asking about a capacitor for the horns. You shouldn't need that. The crossover will take care of any tuning. Unless your trying to change the slope of the crossover point.
Either way, just by lowing the level going to the amp should help protect them. Plus, you can always turn the inputs to the amp down as well.
Jun 18, 2011 06:39 pm Sorry I just saw that it was a question about dB and SPL.
When I say a negative dB level, I'm referring to the output of your crossover. It should have a level knob on it for each output. Typical is for them to mark it off in dB units. SPL is what you measure in the air. SO, by lowering the dB output of the crossover will limit the SPL in the room.
GCTMember
Since: May 14, 2011
Jun 19, 2011 02:53 am As I'm building the horns myself it's common to put a capacitor in series as a failsafe 6dB/oct at the lowest crossover i.e. 500Hz for the 2445. When I saw some JBL cabinets, when in Bi-Amp mode the passive crossover is removed from the circuit. My question is if the series condenser is still left in the circuit - I haven't got one to check. It's DC protection and against a mistake with the crossover on setup.
GCT
Jun 19, 2011 01:32 pm Got ya. I didn't know that the crossover was removed. And yes that is a common practice. (I didn't know that you had an electrical background.)
But, a non electrolytic capacitor is a very good practice to do. Not a bad idea to put a inductor in there as well to filter out a little more, and protect to horn. Plus, this way you can control the slope a little more. Instead of the -6 dB per octave, I would go for more of a -24 dB per octave. And 500hz is still a little low for the horn. Shot more for the 800hz to the 1khz range. -6 dB per octave at 500hz (Should a accidental reverse of the cable happen...... Which it does on a regular basis. As you pointed out.) And yes... Should your amp go DC on you (God forbid!!!) it offers a better protection.
Sorry about the confusion at first. The term condenser is an older term. You don't see it being used very much unless you're talking about mic's. (For some reason the term never left microphones.) And I wasn't 100% sure that is what you were going for. Do you need a good online calculator for this? Or are you good on this?
GCTMember
Since: May 14, 2011
Jun 19, 2011 04:49 pm No problem f = 1/2piRC
I'm english; could explain it. At least I was. lol. Condenser is old fashioned/english but I guess I'm showing my age.
PA sounds great. Just put it all away. Many thanks Mr Stemple.
I think we'll look for a better mid setup (when we can) as it's doing a bit more work than I thought it would (and it's borrowed) but it's nice to know we don't need any more horns. The mid phase reverse is real good. At first it ALL disappeared as you have to duplicate the left and right channels on the xover - and it's the first time we have plugged it all in.
Many thanks
Graham
Jun 19, 2011 05:23 pm COOL!!!! Someone I can get in depth with! Yay!
I rather prefer 12" mids at times. If you can find a cabinet that you can rent for a short period of time. See if that fits your bill a little better.
Where are you in England? I have some connections with Turbosound, and they maybe able to help you with either finding a rental house, or even with set up help as well.
GCTMember
Since: May 14, 2011
Jun 19, 2011 05:37 pm Spain lol - that's SOUTH of England.
So how much power do we need in the mids for 1200w subs per side?
GCT
Jun 19, 2011 06:11 pm Not sure. All depends on the SPL of the boxes. But, I would imagine you would want something in the 99 - 105 dB range. Combined with you horns, you should get a total of about 118 - 122 dB.
GCTMember
Since: May 14, 2011
Jun 20, 2011 02:48 am So I'm thinking 2x12 cabs. I have a design with a 152ยบ angled front baffle - closed box.
Got any suggestions/favourites for a good sounding 12" mid ?
GCTMember
Since: May 14, 2011
Jun 21, 2011 02:43 am Cheers
GCT
GCTMember
Since: May 14, 2011
Jul 29, 2011 02:17 pm OK we now have our 4 x 2226H bought and cabinets almost completed for our first event next weekend. Will look around for some 12" later on as budget permits. Thanks for your help.
Cheers
GCT
GCTMember
Since: May 14, 2011
Jul 31, 2011 08:54 am So far we have
1x 2445
2x 2226
2x 2241
per side
I like the look of the 12" 2206 600W for mids.
Do you suggest 1 or 2 per side?
Cheers
GCT
Jul 31, 2011 11:35 am Depends on the throw that you're looking for. If you want a longer throw, then go with two. If a shorter throw is needed, go with one.
GCTMember
Since: May 14, 2011
Jul 31, 2011 11:56 am So how many metres is considered long throw? Most of our gigs will be outdoors "fiesta del pueblo". Most small towns have at least 1day of events a year.
Jul 31, 2011 12:05 pm I would say that 100 meters is long throw. If you follow the -6 dB rule for your boxes, it should be about 80 to 90 dB at that distance.
GCTMember
Since: May 14, 2011
Jul 31, 2011 06:39 pm Sorry, what's the -6dB rule.
Jul 31, 2011 07:02 pm when ever you double the distance from the point source PA, you drop -6 dB.
So, at one meter, let's say that you measure 130 dB. At two meters, it will be around 124 dB. At four meters, 118. At eight, 112, at sixteen, you should read about 106. and so on.
Jul 31, 2011 07:03 pm And just FYI. A line array is a -3 dB drop per double the distance.
GCTMember
Since: May 14, 2011
Aug 01, 2011 08:39 am Oh Thanks Mr Stemple. Would that be pink noise or 1K sine. C Weighted?
Always a pleasure to chat.
Graham
Aug 01, 2011 10:32 am The should follow in general. So, any noise. But, you do have the issue of pattern to consider when testing. Off axis measurements maybe skewed due to pattern control of single tone burst. Pink noise would be a better choice for off axis. Straight on I don't think it really matters.
GCTMember
Since: May 14, 2011
Aug 01, 2011 12:15 pm Cheers
GCT
GCTMember
Since: May 14, 2011
Aug 08, 2011 08:36 am Hey , glad I put my caps in the horns as the first time out they had the wrong buttons pushed on the xover so the horns got 120-20k and survived a whole rock set. The 2445s are pretty robust. We can try them as subs next time lol
Thanks for all your help
GCT
Aug 08, 2011 08:30 pm Anytime brother!
Glad to hear that all is up and running! :)
GCTMember
Since: May 14, 2011
Aug 09, 2011 11:37 am Well, we're still waiting for 2 2226's still shipping. We popped a couple of Beymas in one cab for the first gig. They have identical bass response to the JBLs but 250w. Clients happy so off to a good start.Looking for a big amp -probably Behringer -for the low mids.
Cheers
