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Author Topic: Getting the MUD out, looking at crossovers  (Read 10630 times)

Vic Turner

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Getting the MUD out, looking at crossovers
« on: April 16, 2004, 06:40:51 PM »

I run an inexpensive set up, 12 channel Carvin board with 2 Carvin 15's with horn, and 2 Behrenger 18's. The question is about the 18's. I know the gear is not considered top notch but any other venue that would require a larger set up usually the venue provides the gear for live music applications, at least in my area. We have had a lot of muddiness from our system. Doing research mostly on this great site I recently found a few things that may help this dilemma. One would be delay and EQ, the second would be the crossovers in the Behrenger 18 subs. They are passive which from what I gather is not the best way to go. According to the website the specs are: Low pass 175hz, slope 9db/oct. High pass 175hz slope 12 db/oct. I'm a noob to this so it's all Greek to me right now, but that will soon change. I know Behrenger is not the best, nor Carvin for that matter but the cool thing about the subs are you can incorporate active crossovers. The question is with the specs provided and a brief description of my gear could the crossover be part of the culprit for the muddiness and if so what steps could be taken to correct it? Is an active crossover the answer if so which one? Could the Carvin 15's w. horns benefit from an external crossover as well? Thanks in advance!!
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Michael Prasuhn

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Re: Getting the MUD out, looking at crossovers
« Reply #1 on: April 16, 2004, 10:45:13 PM »

Are your subs self powered? It sound like you may be reading the spec of the crossover first, to the sub, and secondly, passed on to the top box. Otherwise, that spec really makes no sense. If you could provide a model number, perhaps we could help.

-Mikey P
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Fred Garrett

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Re: Getting the MUD out, looking at crossovers
« Reply #2 on: April 16, 2004, 10:48:05 PM »

Hello,

 The biggest thing I see is that the crossover point is 175Hz which I think it too high for your situation (an 18" crossing to a 15"), I would generally cross that setup over no higher than 120Hz, and if the 15" can handle it I would cross them over at 90Hz. I have never heard an 18 I liked above 150Hz, and like I said, I like 90Hz a lot better, so yes an 18 running all the way up too 175Hz could very well be your problem.  Also, the X-over slopes (9db/oct & 12db/oct) aren't doing you any favors either.  As for your mid-hi boxes, the easiest way to see if they need an external crossover is to just listen to them by themselves with the passive crossover.  If the sound is decent and clean, then just use the internal crossover.  Internal crossovers for horns are very common, and they can sound very nice.

Do you know how to calibrate and balance your system with an active crossover?  If not, then let me know and I will be happy to type in the technique I use.

HTH!
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Vic Turner

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Re: Getting the MUD out, looking at crossovers
« Reply #3 on: April 16, 2004, 11:39:40 PM »

Mikey P wrote on Fri, 16 April 2004 22:45

Are your subs self powered? It sound like you may be reading the spec of the crossover first, to the sub, and secondly, passed on to the top box. Otherwise, that spec really makes no sense. If you could provide a model number, perhaps we could help.

-Mikey P



Hey Mikey P, no we run a Nady power amp for the set up, and a seperate amp for our wedges. Those specs were off the Behrenger website and I just copied it exactly. The model is 1800 it's the Behrenger 18 sub.
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Vic Turner

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Re: Getting the MUD out, looking at crossovers
« Reply #4 on: April 16, 2004, 11:47:20 PM »

Square wrote on Fri, 16 April 2004 22:48

Hello,

 The biggest thing I see is that the crossover point is 175Hz which I think it too high for your situation (an 18" crossing to a 15"), I would generally cross that setup over no higher than 120Hz, and if the 15" can handle it I would cross them over at 90Hz. I have never heard an 18 I liked above 150Hz, and like I said, I like 90Hz a lot better, so yes an 18 running all the way up too 175Hz could very well be your problem.  Also, the X-over slopes (9db/oct & 12db/oct aren't doing you any favors either).  As for your mid-hi boxes, the easiest way to see if they need an external crossover is to just listen to them by them selves with the passive crossover.  If the sound is decent and clean, then just use the internal crossover.  Internal crossovers for horns are very common, and they can sound very nice.

Do you know how to calibrate and balance your system with an active crossover?  If not, then let me know and I will be happy to type in the technique I use.

Hey Square, so how can I make this inexpensive rig rock? I have no clue how to calibrate a crossover at all. Secondly if any of you guys can recommend a good inexpensive active crossover and what bells ans whistles should it have and specs that would be much appreciated. We ran our 15's for a while by themselves and they were muddy too, but they are Carvins what I hear Carvin is not known for thier loudspeakers, maybe a X-over would make em sound better? Thanks again guys, I am a noob but I am learning a ton from this site.

HTH!

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Karl P(eterson)

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Re: Getting the MUD out, looking at crossovers
« Reply #5 on: April 17, 2004, 01:46:52 AM »

Carvin board into Nady amps with carvin tops and behringer subs?... Sounds like the beginning of a nightmare....

Honestly, I am usually one to try and refrain from flat out saying "scrap the gear and start over" but in this case.... I think you should give it heavy consideration. The fact that your gear sounded muddy before you even got the subs really shows that your just operating on gear that simply cant deliver the goods...

I would suggest getting rid of your nady amp, subs and tops and moving to something like 2 JBL MPro418SP powered subs with 2 JBL Mpro415 passive tops, use a dbx 1231 for a decent entry level graphic here.

Another option would be powered mackie tops with a MPro 418SP powered sub with a 418S passive sub slaved to it youd need to use a driverack pa here to get a good crossover and eq.


You could also try the new Turbosound TXD series, One TXD-121 with a TXD-215 under it, powered by a RMX 5050 on the bottom (one channel per side) and a RMX 2450 (one per side) on the highs, use the driverack pa for system tuning here.

All of this is MI line type equipment which could most likely give you good sound.

If you possibly could, Id recommend replacing the board as well with either a allen heath mixwiz, soundcraft something, or a mackie SR something (the mackie will be cheaper, just _dont_ get anything but the SR series).

If you go with any of these lines, you may find yourself wanting to work with your monitors as well before all to long, you should probably just work within whatever line you choose for your mains for your monitors and you would be happy.

Anyhow, while you may not need to replace every single last piece, I do have to admit that I don't believe its possible for you to achieve anything that resembles a "rockin" system till you up your quality a bit.

Karl P
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Brian Fehrman

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Re: Getting the MUD out, looking at crossovers
« Reply #6 on: April 17, 2004, 03:02:08 AM »

Hi,

An active crossover would be a good start. Alot of the "mud" you are hearing may be attributable to harmonic distortion caused by driver over excursion(trying to get your low frequency drivers to go lower than they should go). With the high crossover point and shallow slope of the passive crossover in your subs you could also be getting alot of coupling overlap in the mud(150-400Hz) region. An active crossover with a steeper slope(24dB per octave) can help to solve some of the overlap problems. If you don't have a system EQ with a high pass filter, check your amp to see if have one there. Even a simple 12dB per octave 30Hz high pass will help reduce driver over excursion. The subs you mention will have little if any output below 30Hz, so you won't lose bass, but you will reduce mud. If your budget is limited, keep in mind that an active crossover will require you to have separate amplifier channels for your subs and mid-hi boxes which your passive crossover didn't require.

While better gear is always easier to work with, you can usually make even low cost gear sound decent with a little knowledge, research and experimentation. Several manufacturers make good low cost two way active crossovers(DBX 223XL, Ashly XR1001, Rane AC22) that will allow you to maximize your gear w/o dumping everything and starting over.

Brian
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rhythm1

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Re: Getting the MUD out, looking at crossovers
« Reply #7 on: April 17, 2004, 03:24:55 PM »

Motown wrote on Fri, 16 April 2004 23:40

I run an inexpensive set up, 12 channel Carvin board with 2 Carvin 15's with horn, and 2 Behrenger 18's. The question is about the 18's. I know the gear is not considered top notch but any other venue that would require a larger set up usually the venue provides the gear for live music applications, at least in my area. We have had a lot of muddiness from our system. Doing research mostly on this great site I recently found a few things that may help this dilemma. One would be delay and EQ, the second would be the crossovers in the Behrenger 18 subs. They are passive which from what I gather is not the best way to go. According to the website the specs are: Low pass 175hz, slope 9db/oct. High pass 175hz slope 12 db/oct. I'm a noob to this so it's all Greek to me right now, but that will soon change. I know Behrenger is not the best, nor Carvin for that matter but the cool thing about the subs are you can incorporate active crossovers. The question is with the specs provided and a brief description of my gear could the crossover be part of the culprit for the muddiness and if so what steps could be taken to correct it? Is an active crossover the answer if so which one? Could the Carvin 15's w. horns benefit from an external crossover as well? Thanks in advance!!



Well, I object to some of the advice given here--you're asking for help with what you've got, and some people are telling you to buy all new stuff. Not helpful. Someone else suggesting underlapping frequencies, which is a recipe for MUD in your case as well.

The answer is yes, you should actively cross over everything when you're using this setup. You can run mono and run the subs off one channel and the mains off the other channel of your amp, but I don't know how much power you're sending--probably not enough. Get a bigger amp for the subs as soon as you can, and get a DBX little crossover or something like that.

Engage a subsonic filter at 50hz--your subs won't go lower than that and it will save you lots of power. There's not much information down that low in your situation anyway. Then low pass the subs at 125-150, but with a 24db/octave slope. AN octave is a doubling of frequency, and this number gives you a spec for how much lower the signal will be at a given frequency. So, if you lo pass at 150hz@24db/octave, then the signal is 24db attenuated by the time the signal reaches 300 hz, and 48db down at 600. See how this works? It filters out what you don't want, and sharper slopes filter more--it is a steeper slope.

So, to continue, these things will vary a bit with the room, but I would use the hi pass filter for the subs (this is actually called bandpass, because you're allowing 50 and up and 150 and downm so it's just a band of frequencies being passed). My QSC sub amp has the 50hz filter so I don't have to use the crossover to do that. Then I set my crossover (in your case) to 150 lo pass for the subs. Then set the top cabs to 200hz or so. They won't go much lower than 100, anyway. So, you'll have the subs playing 100 hz full volume, and the tops will be playing that 100 hz, too--but 24 db attenuated. At 150, it's 12db down on the tops, and the subs run up to that. The fact that subs and tops are covering the 150-200 range at attenuated levels should make up for the underlap, but play around with it--try 150 lo, 150 hi, 125 lo, 150 hi, etc., until you find what you want.

But in short, the active crossover is crucial--because as you've noticed, look how shallow the slopes are on passive crossover networks! Passive crossovers also sap power--a good reason to pull them out of the loop if possible--bypass them once you're using the active crossover. Good luck!

David
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Karl P(eterson)

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Re: Getting the MUD out, looking at crossovers
« Reply #8 on: April 17, 2004, 04:53:43 PM »

David,

While the advice you gave is all very good, simply adding an active crossover, two more cheap amps, and removing the passive crossovers won't do him that much good. The problem is that his system sounds muddy, even when when he takes the subs out of it and just straight powers the mains. The chance that the the passive crossover(s) are to blame, is honestly very low. No, the issue here is a combination of parts which simply won't give what they are looking for. Now its true that you could change the amps for a higher quality amp (QSC RMX 2450 would be a good match.) and that might help you... but you still have bad sounding mains and a noisy board with minimal equalization. Change the mains out as well and you still have a noisy board with minimal equalization. add an EQ and you still have a noisy board....

All of this contributes to "mud" in your system. I still suggest he look at new equipment.... maybe via the route of renting (spend a little money and rent two or three parts and change them all out till you find a combination that sounds best, which will probably be to replace board, amps and speakers, and add an active crossover.) From there you have to decide how good you want your sound.

Anyways, hope this clears up my thought process a little bit.

Karl P



Oh, one thing to note.... You have to be very careful when you suggest to someone to pull the passive crossovers.... While this may be something to do if you know what your doing. Telling someone to do this without also explaining the new requirements (more amps, more cables, how to find and insert the correct crossover points, etc) and the possible dangers involved.. (if he sends the wrong information to the HF driver he will fry that puppy before he figures out whats wrong, etc....) or, if nothing else, document how to build a protection circuit for it and help him as he does it.
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Vic Turner

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Re: Getting the MUD out, looking at crossovers
« Reply #9 on: April 17, 2004, 07:38:49 PM »

Thanks everyone for the responses. You are all right I feel. I'd been given some great advise as far as getting my current gear to sound better, and your right it's kinda crappy stuff. We just can't afford an Allen and Heath board let alone all the other things to upgrade. So let me ask this, keeping the cost down and knowing what I currently have, what gear would make this set up sound better..forget totally rockin? I'm thinking different 15's, an active cross over for sure what else? What are some decent 15's that won't break my wallet? What could I do to salvage this thing? Sure I can get an active crossover but the Carvin 15's are tired ande just didn't do it by themselves let alone with subs now. I think to if we upgrade our board we are in the Behrenger price range there too unfortunatly or something simular. Any help is greatly appreciated, thanks again!!
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