Variable sound quality, JBL PRX rig

Lisa Lane-Collins

Lisa Lane-Collins

Sophomore
Dec 9, 2012
270
0
16
Adelaide, Australia
Another question for you good folks.

So I had this rig set up, to 615s, one either side mounted to the walls, quite high up, maybe 4 metres from ground level, 2 618s-xlfs under the side of the stage pointed at the wall. It sounded ok sometimes, terrible mostly, a touring engineer worked some magic with the DSP and it sounded amazing. Then it sounded amazing Without his DSP programming (just running full range). I finally convinced the pub to let me move the subs back out so they would be lined up with the tops (because surely that will be better right?). And it sounds terrible again. At present it's running totally flat so tops are doing full range and sounds like it has no low mids, or mids actually for that matter. Super painful treble, not much bass, kinda sounds like the subs and tops Aren't working together. Every track with vocals sounds like the vocals are buried in the mix when the should be at the front. The question of out of phase does cross my mind but I tested that a couple of weeks ago and it seemed that everyone was all good.

Suppose questions are many fold, can these PRXs even be coaxed into sounding good?

Is the reduction of sub frequency bouncing around (due to being pointed at the wall) worth the loss of volume?

Could it be something other than the speakers that sucks all my low mids out? (Like a bad mic cable, or the DBX drive rack, or the fact that they are very high).

Tomorrow I will go in with a DB metre and SMAART tools and at least try and tune this thing properly with technology (because I've failed to do this by ear). I'm feeling apprehensive, is that gonna cut it? Can the 615s even give me the full range I want and the volume I need? (See other thread for contemplation of increasing it to two a side).

My other thought was that maybe I should bypass every facet of my installation and play something (from a CD, not a bad mp3), through a separate mixer, plugged straight into the speakers, see if that sounds better, work my way back from there.

Soooo not the right rig for the room but with not much cash in the bank, I'm really hoping I can get better sound out of this than I have today, which surely I can, because this time last week it sounded infinitely nicer, and the only thing that has changed is moving the subs into (what is theoretically) a better location. Sigh!
 
Re: Variable sound quality, JBL PRX rig

Lisa Lane-Collins said:
Another question for you good folks.

So I had this rig set up, to 615s, one either side mounted to the walls, quite high up, maybe 4 metres from ground level, 2 618s-xlfs under the side of the stage pointed at the wall. It sounded ok sometimes, terrible mostly, a touring engineer worked some magic with the DSP and it sounded amazing. Then it sounded amazing Without his DSP programming (just running full range). I finally convinced the pub to let me move the subs back out so they would be lined up with the tops (because surely that will be better right?). And it sounds terrible again. At present it's running totally flat so tops are doing full range and sounds like it has no low mids, or mids actually for that matter. Super painful treble, not much bass, kinda sounds like the subs and tops Aren't working together. Every track with vocals sounds like the vocals are buried in the mix when the should be at the front. The question of out of phase does cross my mind but I tested that a couple of weeks ago and it seemed that everyone was all good.

Suppose questions are many fold, can these PRXs even be coaxed into sounding good?

Is the reduction of sub frequency bouncing around (due to being pointed at the wall) worth the loss of volume?

Could it be something other than the speakers that sucks all my low mids out? (Like a bad mic cable, or the DBX drive rack, or the fact that they are very high).

Tomorrow I will go in with a DB metre and SMAART tools and at least try and tune this thing properly with technology (because I've failed to do this by ear). I'm feeling apprehensive, is that gonna cut it? Can the 615s even give me the full range I want and the volume I need? (See other thread for contemplation of increasing it to two a side).

My other thought was that maybe I should bypass every facet of my installation and play something (from a CD, not a bad mp3), through a separate mixer, plugged straight into the speakers, see if that sounds better, work my way back from there.

Soooo not the right rig for the room but with not much cash in the bank, I'm really hoping I can get better sound out of this than I have today, which surely I can, because this time last week it sounded infinitely nicer, and the only thing that has changed is moving the subs into (what is theoretically) a better location. Sigh!
Click to expand...
If you have Smaart 9and use it properly) then there is almost no reason for the dB meter.

Are you talking about PHASE or POLARITY? They are very different things and often misunderstood.

You need to start with making sure each cabinet is working properly-BY MEASURING-not by playing a CD.

Then slowly start adding other components to the system and see how the results change-IN VARIOUS positions around the room -NOT just a single listening position.
 
Re: Variable sound quality, JBL PRX rig

Going back to what sounded good seems to be the obvious solution, doesn't it?
I just don't get you, you said they sounded amazing, and then a couple of sentences later you question if the rig can even be made to sound good????

Subs work best when working together, and in a long room the distance between them will influence whether you are filling the room or just bouncing a lot of energy off the walls, the direction they are pointed in matters not at all. Mounting the 615 with a wall in very close proximity will certainly create some havoc in the upper bass and lower midrange, and if the horns are bouncing off the walls as well, the havoc will go on for most of the spectrum.

But, you tried something, it didn't work, so start with moving it back to what did work! If you don't want to move it back because you spent a long time convincing the bar-owner, and don't want to admit that you were wrong, then rest assured that you get more respect admitting a failed experiment than digging yourself into a deeper hole.
 
Re: Variable sound quality, JBL PRX rig

LOL. What Per says. If it sounds right it is right. Also another war story and learning experience for you. Let us know how everything turns out.
 
Re: Variable sound quality, JBL PRX rig

Lisa

I can assure you the PRX600 series CAN sound great. I think you're dealing with a rough room, and inexperience. Speaker placement is critical in a room like this.

If you have the tool or support to measure the room, by all means that will be the best method.

When I use my system I "tune" it by ear, using recorded music. I think if you have a good clear recording that you are familier with this can work. Listen to your bass bins from behind while pushing the polarity button.

Try moving a little closer to the speakers to listen to what they are doing. These are not "long throw" speakers IMO. I also question the use of a Driverack. I don't use one, and find the JBL's can sound very nice with just a little EQing. I run the 615 volumes straight up, and the XLF's at 3 o'clock. I do use the XLF "crossover".
 
Re: Variable sound quality, JBL PRX rig

Make sure the EQ boost switch is off on both speakers.

Make sure both speakers are set to line not mic.

Make sure the horns are functioning.

Personally, I would be amazed if fully functional speaker of this model could sound as bad as you indicate.
 
Re: Variable sound quality, JBL PRX rig

Silas Pradetto said:
Some rooms just make your day miserable
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The OP implies a lack of proper crossover hookup and moving stuff around that sounded fine because it didn't look right - Yup, working hard at it ;)~;-)~:wink:. If the OP really wants a hand please let us not have to guess as to how it is all hooked up and what this "DSP" you mention is...
 
Re: Variable sound quality, JBL PRX rig

A few points...

The best way to make a PRX rig sound good it to run your mixer straight into the XLF subs. Engage the cross-over in the subs. Run the output of the subs into the tops. Run the tops in full range.

The XLF's cross-over at 90 Hz. This will work quite well with the 615's which should be able to pound nicely on the mid lows.

Putting the subs together in the center of the stage gives you a nicer coverage pattern than one sub per side in most rooms.

Using a single sub and single top, bring the volume up to a respectable level with some relatively thumpy music. Have someone listen to the sound out front with the XLF phase switch in each position to tell you which one sounds better. My guess would be to leave it in the "out" position.

Finally, as others have said, the PRX powered speakers CAN sound very good. It is difficult to make the system sound bad IME unless you do too much to it.

btw haven't heard from the OP.
 
Re: Variable sound quality, JBL PRX rig

Ok, so, apologies for unfocussed nature of this reply and the inevitable information overlap between this thread and that other one I made (same solutions, well, used advice from both, anyway, enough lurking, time for some replying to awesome helpful responses!!)

Ivan - I believe I mean polarity. The flicky switch on the back of the subs where if you press one but not the other and everything is as it should be you more than halve the volume output.....when this manifests in the tops the stereo imaging goes to hell and you lose the illusion of centre.

Took this measuring advice to heart and obtained a db meter and a pink noise generating app (although possibly neglected to do each speaker individually for some reason). Found with music 10 metres back the PA was struggling to hit 95db. Also went on a quest to obtain an RTA mic. Whilst messing around with that trying to get the driverack to acknowledge signal and do it's auto things PA put out a little over 105 db at one point (felt rather sick after that little escapade).

Post Auto leveling and EQ everything sound MUCH better. I am wondering now if a bunch of untamed low end resonant frequencies I was never game enough to notch out on the graphic were perhaps masking frequencies higher up? I lost a bit of volume, but everything sounds nicer, tighter (as one would predict).



Per - With the speakers on the wall thing, I've pulled them out as far as possible (maybe 7 cms clear now and point in slightly), I do reckon that makes a bit of a difference. Could be speaker position slowly drifting closer towards the wall was affecting the sound? (I have another theory about that now to do with the master volume being turned up during intermission and second acts being done at louder volumes and speakers Never sounding nice when they are struggling).

The reason I wanted to move the subs was because people kept telling me to line up the subs with the tops so everything is time aligned and I can work out how to compensate for subs being in front or behind the tops but clear firing off in another direction? Simply melts my mind. Tis possible that they could sound loudest and nicest under the stage With the SMAART processing (although I have secret other reason for wanting them out along the lines of powered speaker needs to be able to cool itself and massive pocket of bass on stage/backstage makes everyone on stage feel sick). Post SMAART everything sounds nicer so I could be off the hook now, if it hadn't worked, I concede, I would have had to put them back where it sounded better.



Chuck - Checked :-) (well, not the cross over bit but both polarity switches are out currently, and having them both in made no noticeable difference when paired with tops).


Steve - Ugh, the Worst room! (See pictures, show and tell time :-D) The nicest I've ever heard them sound is when run like you say, no external dsp, just sub, then top. However, this is a dry hire situation and I am primarily looking for system protection (although the thought occurs to me now I could just have bought a compressor limiter, anyway). I've no doubt they are the right speakers for the job, but I will have to work with what I have for now (which will soon be four. Try 2 aside not for extra coverage but so none have to work as hard). Just curious but do you not find the PRXs to have some serious bite around 4k which is almost impossible to EQ out? (As in, when you EQ they sound dead and that middle ground is hard to find).


Steve or Tim - Can either of you confirm for me that the Flat response requires the EQ button to be pressed in? I've been puzzling over this for the last 12 months. Every time I try and logic it out using the mic/line switch for reference I draw the same conclusion.


Tim - Could volume factor into the PRXs sounding bad?


Ron - mentioned in passing but formal answer, it's a DBX driverack PA+


Scott - I've been lurking but putting off replying because it was always gonna be loooooooooong. I was hesitant to run full range because of the volumes required but if I crank 2 a side (with neither having to work as hard), I shall try that, I wonder if running full range will help negate the disconnect between sub and top?

Alright, time for pictures
 
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Re: Variable sound quality, JBL PRX rig

20131220_145054.jpgview from the desk, see where the ladder is? the subs where under the stage pointing at the ladder wall

20131220_145442.jpgtrying to show speaker placement in relation to the wall, sorry, bad photos and dont know how to rotate. still hoping tese pic will help convey a sense of the size and nature of the space

20131220_145417.jpg
 
Re: Variable sound quality, JBL PRX rig

With the measuring thing I discovered something else by accident. Tried doing a sine sweep from low to high and learned that, at around 3.6kHz (became 4.6 after RTA auto EQing) I get a second, divergent tone, quieter, but definitely audible, a couple of octaves lower, going down as the primary tone goes up. If these secondary frequencies are part of the overall sound when playing music, that can't be good but I suppose that warrants a thread of it's own really.
 
Re: Variable sound quality, JBL PRX rig

Lisa Lane-Collins said:
Steve or Tim - Can either of you confirm for me that the Flat response requires the EQ button to be pressed in? I've been puzzling over this for the last 12 months. Every time I try and logic it out using the mic/line switch for reference I draw the same conclusion.
Click to expand...

Button out: IN is for speech only applications.

Tim - Could volume factor into the PRXs sounding bad?
Click to expand...

In my experience my PRX sounds fine right up to the point where it thermals out from being outside with direct sunlight on the amplifier (back).

Ron - mentioned in passing but formal answer, it's a DBX driverack PA+


Scott - I've been lurking but putting off replying because it was always gonna be loooooooooong. I was hesitant to run full range because of the volumes required but if I crank 2 a side (with neither having to work as hard), I shall try that, I wonder if running full range will help negate the disconnect between sub and top?

Alright, time for pictures
Click to expand...

Could you clarify this a bit? Are you proposing to run 2 tops a side? (see comb effect)
 
Lisa Lane-Collins said:
With the measuring thing I discovered something else by accident. Tried doing a sine sweep from low to high and learned that, at around 3.6kHz (became 4.6 after RTA auto EQing) I get a second, divergent tone, quieter, but definitely audible, a couple of octaves lower, going down as the primary tone goes up. If these secondary frequencies are part of the overall sound when playing music, that can't be good but I suppose that warrants a thread of it's own really.
Click to expand...


If you are using any type of auto eq, that is likely the problem right there.


Sent from my DROID RAZR HD
 
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