Crossover opinions
Scooter
Posts: 9
As a frequent voyeur and rare poster here on the DRPA boards (thanks for sharing the knowledge), I'd like to solicit opinions about the Xover settings to use with my bands' primary PA setup.
I play in a couple of rock bands (some common memebers) with audiences of 200-500 every weekend. Our primary speaker setup (we collectively own quite a few speaker cabs, so we have a choice on what we play with on a particular night) is a pair of JBL PRX518S subs with JBL PRX535 tops. (Yeah, I know the JBL PRX is not the best, but I was out-voted by the rest of the band members) We've been running this system for a couple of years with a DRPA. The PRX series was one of the better options for powered sepakers when we bought them a few years back, but there are much better options available now. Since our PA is generally sufficient for what we do, we aren't really considering buying new/different equipment right now & the PRX stuff makes for an easy set up. Our durmmer usually plays a vdrums kit that really pushes our PRX system hard and takes up a good deal of headroom. Getting the drums loud enough is pretty much our only ongoing PA issue.
The PRX 518 subs are ridiculously underpowered (500 watts RMS, 1000 watts peak). The newer 718 is a bit better, but we've passed on getting the newer versions. The 518 does not have enough wattage/efficiency usually to get great clarity and \"thump\". They do an \"OK\" job, though. My biggest complaints with the cabs are the 500 watt RMS and the fact that the input sensitvity is mic level, not line level (the 535s can be switched to either mic or line level inpts). Also, the internal Xover in the PRX 518S is pre-configured to cross at 125hz (too high IMO).
Since the PRX 518 subs have such wimpy amps in them (which clip freqently if we cross them @ 100hz), and since internal Xover is a little high, we always run them with the DRPA. I usually set the high pass to the 535s around 80hz as the 535s are capable of driving frequencies down into the 60hz range, and it \"frees up\" the 518s to only drive the really low frequencies. I generally set the DRPA to send the 518s a 40hz-80hz signal in an attempt to \"leave some headroom\" on the 518s (yeah I know 40 is a little low for these cabinets). The amps on the 518s usually won't clip when set this way unless we have to \"turn up\" due to the # of bodies in the rooms we play (we play a different venue every Fri/Sat night). I was thinking about setting the Xover a little lower (down to 70hz) as the 535s have a 15\" driver that will handle frequencies down into the 70s and the 535s have never been pushed to clipping (at least I've never seen them clip while we're playing). I'd like to get some opinions on what the \"right\" Xover setting is for our setup. Is 70/80/90hz Xover a good/bad idea with this setup (or should I stick with 100/125)? why?
It seems to me that we're probably not working the low end of the 535 cabs hard enough (since they never clip). If I high pass the 535s at 125, it seems to me that the 15s in those cabs really aren't pushing much of anything (since JBL specs on the 535s indicate that the 15\" is low passed at 430hz) Thoughts??
I've read the read me first sections (quite a few times), including gain structures and crossovers, but I'm really looking for some pointers on fine-tuning our system to get more clarity (and maybe a little more \"kick\")out of the equipment we have. Maybe it's not possible with the PRX series, but any input/suggestions are appreciated.
I play in a couple of rock bands (some common memebers) with audiences of 200-500 every weekend. Our primary speaker setup (we collectively own quite a few speaker cabs, so we have a choice on what we play with on a particular night) is a pair of JBL PRX518S subs with JBL PRX535 tops. (Yeah, I know the JBL PRX is not the best, but I was out-voted by the rest of the band members) We've been running this system for a couple of years with a DRPA. The PRX series was one of the better options for powered sepakers when we bought them a few years back, but there are much better options available now. Since our PA is generally sufficient for what we do, we aren't really considering buying new/different equipment right now & the PRX stuff makes for an easy set up. Our durmmer usually plays a vdrums kit that really pushes our PRX system hard and takes up a good deal of headroom. Getting the drums loud enough is pretty much our only ongoing PA issue.
The PRX 518 subs are ridiculously underpowered (500 watts RMS, 1000 watts peak). The newer 718 is a bit better, but we've passed on getting the newer versions. The 518 does not have enough wattage/efficiency usually to get great clarity and \"thump\". They do an \"OK\" job, though. My biggest complaints with the cabs are the 500 watt RMS and the fact that the input sensitvity is mic level, not line level (the 535s can be switched to either mic or line level inpts). Also, the internal Xover in the PRX 518S is pre-configured to cross at 125hz (too high IMO).
Since the PRX 518 subs have such wimpy amps in them (which clip freqently if we cross them @ 100hz), and since internal Xover is a little high, we always run them with the DRPA. I usually set the high pass to the 535s around 80hz as the 535s are capable of driving frequencies down into the 60hz range, and it \"frees up\" the 518s to only drive the really low frequencies. I generally set the DRPA to send the 518s a 40hz-80hz signal in an attempt to \"leave some headroom\" on the 518s (yeah I know 40 is a little low for these cabinets). The amps on the 518s usually won't clip when set this way unless we have to \"turn up\" due to the # of bodies in the rooms we play (we play a different venue every Fri/Sat night). I was thinking about setting the Xover a little lower (down to 70hz) as the 535s have a 15\" driver that will handle frequencies down into the 70s and the 535s have never been pushed to clipping (at least I've never seen them clip while we're playing). I'd like to get some opinions on what the \"right\" Xover setting is for our setup. Is 70/80/90hz Xover a good/bad idea with this setup (or should I stick with 100/125)? why?
It seems to me that we're probably not working the low end of the 535 cabs hard enough (since they never clip). If I high pass the 535s at 125, it seems to me that the 15s in those cabs really aren't pushing much of anything (since JBL specs on the 535s indicate that the 15\" is low passed at 430hz) Thoughts??
I've read the read me first sections (quite a few times), including gain structures and crossovers, but I'm really looking for some pointers on fine-tuning our system to get more clarity (and maybe a little more \"kick\")out of the equipment we have. Maybe it's not possible with the PRX series, but any input/suggestions are appreciated.
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Comments
Dennis
The 535s never have a problem carrying the room and they're plenty loud for the smaller outdoor shows that we have to use our own PA with (mostly private parties). I actually like the 535s, just not the subs. Two 535s (per side) is probably more than we need, but two subs (per side) would be a huge improvement.
Narrowing down the spectrum that the 518s carry makes sense to me (to put more of the 80-100hz burden on the 535s). I'm just curious if it makes sense to go even lower with the Xover when there's less audio content at lower frequencies (even though the low end is what really makes a system kick).
Raise the HPF of the subs to a MINIMUM of 45 hz BW 18, probably 50hz under the circumstances... AND put the subs together for a free three db of sound...(6 db is twice as loud... 3db is considered the smallest noticable change... center clustered, both on one side... against a wall you get an additional 3db, in a corner... 6 db...so 2 together, in a corner 9 db FREE sound...HOWEVER... the farther apart the more you need time alignment...
Also 3 1/2 feet from ANY boundary will help wipe the kick drum first harmonic (THUD) from the face of the earth...3 1/2 feet up, 3 1/2 feet out and 3 1/2 feet from a side wall = 9db of cut I don't care if you have 10,000 watts the kick will have NO power what so ever..it's called \"Boundary Cancellation\"
The additional 80hz on up means very little to the subs... You may in fact experience a better clarity out of the 15's if you DON't push the low end with them...the BIG thing here is the VLF (very low frequencies) and that sub 50 hz is KILLING you...Are you running the 518's in bridged mono? What amp?
Gadget
That's exactly the kind of input I'm looking for. Thank you, Gadget. You made me think about a lot of things I had overlooked (room acoustics/chracteristics). I'm familiar (and have experienced) the effects of boudary cancellation/acoustic coupling. We can free up all the headroom we want and it will still have little/no effect.
Here's a little more detail:
My cover band is the house band and play one venue the last Saturday of each month. The place is a nightmare acoustically and is where we have the most problems getting \"thump\". The room is approx 100 ft. wide and 300 ft. deep. The left stage wall has a line booths the length of the room (long way) that are elevated about 6 inches on a concrete pad. (So the left speaker stack sits about 1 ft off of a 6 inch concrete pad that runs the length of the room (long way). This results in having a speaker stack about 3 ft from the left side wall of the room (lined by booths - lots 'o boudary cancellation goin' on). The right side of the stage is generally open space, with the bar running the long right wall of the room starting about 15-20 ft away from the stage front. To top it off there's a row of booths in the middle of the room about 20 ft from the front of the stage that runs almost to the back wall. (To put it into visual terms, the right side is really the only large open area (other than 15 ft of dance floor in front of the stage. This venue has capactiy of just under 500, with capacity in the \"main room\" of about 300.
Not sure if that's real clear, but the salient point is that the left stack experiences significant boundary cancellation. (I've done a fare amount of research trying to get around this since we play this space frequently). The other \"kicker\" is that I've wanted to couple the subwoofers in front of us (or to one side), but we need the subwoofers to keep the 535s above chest level (so the highs don't get lost) - there's no house PA. As I type this I'm thinking this is a no-win situation. (We builit empty particle board boxes to lift the 535s another 15\" - so our speaker stacks are: sub woofer-riser box-535). the stacks are approx 30 ft apart.
The net effect is that we have to figure out a better way to set the speaker stacks up. Maybe flying them??
I was thinking that the kick drum first harmonic \"lives\" around 80hz, so I was a little concerned about using that as a Xover point. But (as you pointed out), I think the problem is more room acoustics than equipment related.
The subs have an internal amp (500 RMS 1000 peak). We set the subs up as stereo subs in the DRPA.
I'm curious why you say 45hz-50hz for the high pass to the subs. Your recommendations are consistent with the specs of the cabinet, but I'm wondering if you're saying \"stay in spec\", or if there's an acoustic advantage to raising the high pass floor. I'm ssing your point that Xover frequency is irrelevant.
Dennis
Or poles as Dennis suggested as a lesser solution...
The thing here is to get the system flattened...and get the sound ON the people and OFF the hard surfaces...You are very bass shy, and need to try ANYTHING to stack the deck...CAN you put them BOTH on stage right? Best would be to find a central FLY location for the smaller subwoofers and have a 260 to fix the delays... but I think you need to try the above first and see where you end up...( Yes I meant put the subs in the center of the room above the audience's heads if you have very small speakers and limited power, you will have your best results...it may not be possible...just indicating what would give you the BEST results with what you have (except for the 260 I guess
I was lucky enough in the last 2 venue's I went to where I could set the subs up against a boundary (a wall in this case) all on one side but not in a corner...the bass will then be omni directional, and from one source so you don't have comb filtering (position dependent for optimum results...) and the coverage is far superior... and NO power alley! That alone should brighten your day...
If you can do those things... your not going to BELIEVE
Ultimately, you should have more subs and more power and then you will be happier...BUT true audio nirvana can be accomplished!
Gadget
Don't even think of using the handels as fly points!!!!!!!
Dennis
Build some storage boxes for the tops that can be used for lifters.
Mic level input only on the 518's. I really doubt that.
DRA
JBLs specs say the 535 has pole mounts, and technically they do. But JBLs engineers did a poor job of exectuing this as the pole mount sockets are only two inches deep, so the 535s won't mount on stands safely (the cabs are 75 lbs each and are about chest high, so the center of gravity is pretty high). JBL really missed the mark on the pole mounts - I'd like to see someone try to use them (and then bravely run away from them) - they're extremely \"wobbly\" on stands. Very poor design.
The 518s input sensitivity is -25db-0db, so I guess it's not truly \"mic level\", but the 535 has a switch for line level inputs (+28db-+10db) and mic level (-25db-0db). It just seems odd that the 535s have line level sensitivity and the 518s don't.
I'm thinking (for this particular room) that building some empty stand cabinets for the 535s might be the easiest way to go. We already have a set of stands that gives about 15\"-20\" of lift (that sit on top of the 518s), so I guess we could build some that are a little taller and move the subs to the center or right. I've talked with the venue owner about doing a permanent install (of house PA) so flying (his) speakers might be an option in the near future.
This system (535s and 518s) sounds great outdoors (even though we could use a couple more subs), but 2 535s have always worked for us (indoors or out). It's really just this one room that we have sound issues with. I've been trying to solve it with DRPA settings and that's obviously not going to work. Time to build some more stands. Thanks folks.
DRA
I have some time to kill this weekend and would like to run some low end predictions for this venue on a computer program to determine sub placement. My prediction programs are all brand specific but hey, a single 18 sub is a single 18 sub. I would need a floor layout of the club with some reasonably accurate dimensions.
Dennis
G
Thanks for all the input on this, you folks are great. Dennis I'll porbably take you up on the acoustic modeling offer as this is a space I play at least once a month (playing there 3 times in Sept).
The owner is a friend of mine & it's my \"local watering hole\" (which is why we're the \"house band\"). They didn't book a lot of live music until my band started getting the place recognized as a live music venue. Now they book bands every weekend. To that end, I had a discussion last week with the owener about doing a permanent install of PA gear (speakers, power, and FOH snake). Flying speakers are a must based on the input here. Since every band has problems in this place, solving some of the acoustic issues would really be helpful (I run sound for one of the other bands that plays there since I'm familiar with the venue). Every band uses the same type of speaker setup and runs into the boundary issue here.
I guess I'm still a bit curious on the Xover point settings. For outdoor shows (or assuming no acoustical considerations), does anyone think would it make sense to bump the Xover point down in the 70-80hz range to save some headroom on the subs? Or is that putting too much work on the 15's. Just curious.
The good news is that the cabs are tri-amped. The bad news is the mids only go to 450hz (there abouts). If you have a female vocalist, not too bad, but for guys, you are at his upper limit (meat). So, the more you lower the 15' HPF the more that is affected. Sylabance (sp) will be fine though. In the end you'll need to try and compare. You won't hurt anything.
I'd try 70 & 90hz and stay away from 80.
DRA
I just looked those subs up and they are 3 db down @ 52 hz anyway...so all your doing by setting the HPF lower than 50 hz is wasting power!
As I said also the tops will sound better in the low mids if they aren't having to reproduce the low frequencies...
As a test...have the drummer play the kick as you start the HPF @ 40 hz and move it upwards as he continues to play... kick only... see where the best kick sound is... then inderstand that there is probably a peak @ around 60hz and 100hz.. use the DRPA PEQ's to implement cuts @ those locations vary the gain and center freq to find the sweet spots...
G
First I got a demo version of SIA Smaart by EAW and run it on an outdoor space (you can try this on your indoor space) I connected the RTA mic to an audio interface and tried various frequencies generated by the program at my sub.
Is really easy to tell by ear, which frequencies your sub reproduces without distorting. For your help you can take a look of the frequency response at the software measured by the RTA mic.
Most of us know that the average range of spectrum hearing begins at 20 Hz and goes to 20 kHz, but not all of us have had the time to actually “hear� each of the regular frequencies used in audio. You can do that with smaart.
In my case I have the lowest frequency set at 35HZ and the upper one at 118Hz on my Mackie sub both set at 24 LR. This setting on my DRPA gives me awesome results.
Now, you are mentioning that you have 2 subs. Sometimes I have the chance to have more than one Mackie sub. The usual thing to do is to place the subs on each side, but let me share with you something I have learn from Meyer Sound: Subwoofer arrays.
They say that one of the best ways to place subs is to place them close together. In my case I have tried to place two subs less than 3 ft apart on the center-floor of the scenario. Meyer Sound suggest to use a mathematic formula. I can’t draw it here, because I don’t know how, but use the rule of less than 3ft of separation, and it will give you as result to have a more even coverage of bass on your room. Also you avoid cancellation of phase by separating the subs and therefore minimizing the output of you system.
Dennis
Gadget