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Author Topic: PRX 718 XLF vs ?  (Read 10256 times)

Randall Hyde

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PRX 718 XLF vs ?
« on: August 22, 2014, 12:01:34 PM »

Before you even post, yes I have searched the board...

Last year I was running a pair of JBL MPro 418s subs off a Crown XTi 4000 amp on my "B" rig. The "B" rig consists of four JBL PRX 625 cabinets (run in a dual PA configuration, vocals and back line each through their own pair) and four PRX 715m cabinets as monitors, plus the aforementioned subs. Decent sound for <100; okay sound for as many as 250. I've actually used the rig for crowds as large as 1,000 (though you obviously don't get "rock show" sound levels at that point; closer to 80-85 dB near the back and subs output is non-existent at that point; but it's what the promoter wanted).

Due to an unfortunate trailer accident, the MPro 481s subs were destroyed.  Until recently I was substituting a JBL SRX 728s from my "A" rig for the pair. However, the weight and size of the 728s made this impractical for my "B" rig (some shows need to be set up and struck by one person) so I finally got around to purchasing a pair of JBL PRX 718 XLF subs.

To say that I am underwhelmed is putting it mildly. The 418s/Crown combo was quite a bit superior to the new boxes. Granted, the XTi 4000 cranks out a lot more power (1,250 *real* watts per channel into 4 ohms versus the mythical "1,500 watts" that JBL claims for the PRX 718 XLF). I can hear the 718 XLFs working, but you can't *feel* anything. Not even from 20' away. I've tried boosting the subs; I can *hear* it's getting louder (to the point it messes up the sound) but still no thump. As for the cross over, I've tried three things:

1) High-pass on the back line pair of PRX 625 at 90 Hz (recommended)
2) High-pass on the back line pair of PRX 625 at 80 Hz
3) High-pass on the back line pair of PRX 625 at 100 Hz

Note that I run aux-fed subs in this system, so just feeding the back line output to the subs and taking the (internally cross-over) output to the PRX 625 cabinets isn't workable. Also, the subs are center-clustered so they're not fighting one another (though there will be some interference with the tops at the cross-over point as the back line speakers are left/right on the stage; however, the 418s cabs were run the same way w/o any problems).

Am I doing anything obviously wrong? (Well, besides the good old "not enough subs" line -- remember the 418s cabs worked fine for this system).

My current attitude is that it's time to cut my losses, sell off the PRX 718 XLF cabs and buy something else that will work. If I can find them locally (SoCal) I'm leaning towards buying a pair of SRX 718s cabinets (and running them off the XTi 4000). If none are available, I might consider getting a pair of VRX 918s subs and running them off the Crown.

Any suggestions on other subs that might work? Here are my restrictions:
1. I'd prefer powered subs. But passives running off the XTi 4000 are fine.
2. I usually center-cluster the subs in front/center of the stage. Most stages I work with are 2' high so the sub cabinet can be substantially higher than 2'. This, for example, eliminates things like the Danley TH115.
3. One (strong) Person needs to be able to lift and position the sub. This requirement affects weight as well as size (e.g., a dual 18" cabinet just won't work here; though two single 18" cabs would).
4. It needs to fit in the back of my (camper-shell-covered) pickup with the rest of my gear (which is one reason going to more subs is out of the question -- I have packing issues). The MPro 418s was perfect, so is the PRX 718s. Something around that size is what I need (and no more than two).
5. I'd prefer something in the $1,000 range (each); but I can live with sub-$2,000. I.e., the price point of the PRX 718 XLF is perfect. The QSC KW 181 is doable. The VRX 918s barely so.
6. I really need to get at least the performance I was getting out of the MPro 418s cabinets. Anything less and I've already got a solution. Better performance would be, well, better.

Would love to hear from folks who have experience with the PRX 718XLF and some other sub.
I have not listened to a KW 181 side-by-side (or anything else beyond the 728s and 418s). Note that I bought the 718 XLF based on glowing reviews around here, so I take comments like "I've always used a KW 181 and it's great" with a grain of salt unless the poster talks about how they've used the PRX 718 XLR and it didn't work for them.
Cheers,
Randy Hyde


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Scott Holtzman

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Re: PRX 718 XLF vs ?
« Reply #1 on: August 22, 2014, 12:15:30 PM »

Wow - typed a whole message and only the quote was there.

Bottom line was I said that I run KW181 in the size rooms you indicate and I would call them palpable.  I have never heard the 718xlf but I assume that all three of the big guys at this price point, the 718xlf, the KW181 and the ETX118s from EV are all at the limit of sub $2000 front loaded bass reflex designs at the differences are marginal and may not even be perceptible.

« Last Edit: August 22, 2014, 02:36:00 PM by Scott Holtzman »
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Ivan Beaver

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Re: PRX 718 XLF vs ?
« Reply #2 on: August 22, 2014, 12:43:52 PM »


2. I usually center-cluster the subs in front/center of the stage. Most stages I work with are 2' high so the sub cabinet can be substantially higher than 2'. This, for example, eliminates things like the Danley TH115.

I am assuming you meant LOWER than 2' not higher.

If you lay the TH115 on the side it is 22.5" tall-so less than 2'.

The TH212 on its side is even less (15")
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Randall Hyde

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Re: PRX 718 XLF vs ?
« Reply #3 on: August 22, 2014, 01:24:52 PM »

I am assuming you meant LOWER than 2' not higher.
Yes, thinking one thing, typing another.

Quote
If you lay the TH115 on the side it is 22.5" tall-so less than 2'.

The TH212 on its side is even less (15")
That's almost a great idea. Truck pack and weight the only problems. Putting two cubes in my (covered) pickup is easier than the TH115. One person lifting the TH115 is a problem, but I suspect I can tilt it up on the tailgate w/o too much difficulty (sadly, I suspect the weight is mostly at the bottom, especially with a powered unit?).

I *really* like the idea of the TH115 as it would kick butt on any other configuration I can afford on this rig (especially if I get a powered unit). I will have to think this through, play a little Tetris, and see if I can make it work.
Cheers,
Randy Hyde
« Last Edit: August 22, 2014, 01:29:45 PM by Randall Hyde »
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Randall Hyde

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Re: PRX 718 XLF vs ?
« Reply #4 on: August 22, 2014, 01:28:23 PM »

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Steve Eudaly

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Re: PRX 718 XLF vs ?
« Reply #5 on: August 22, 2014, 01:54:19 PM »

I often work a rig with a VRX 918s used for drum fill. Sometimes I'm provided an XTi 4000 for power, sometimes an iTech 6000. The XTi has a hard time getting enough output from the 918s before clipping, while the 6k works well. Obviously we're talking two very different amplifiers, and in this case the sub is being used by itself, not in multiples, but thought I'd chime in with the experience.

Rob Spence

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Re: PRX 718 XLF vs ?
« Reply #6 on: August 23, 2014, 12:56:36 AM »

Check polarity on the subs?


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Chuck Simon

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Re: PRX 718 XLF vs ?
« Reply #7 on: August 23, 2014, 10:02:58 AM »

I *really* like the idea of the TH115 as it would kick butt on any other configuration I can afford on this rig (especially if I get a powered unit). I will have to think this through, play a little Tetris, and see if I can make it work.
Cheers,
Randy Hyde

Didn't you state that the SRX 728 was too heavy?  You know the TH115 is pretty close to the same weight and well above your $1000.00 price limit.
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Randall Hyde

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Re: PRX 718 XLF vs ?
« Reply #8 on: August 26, 2014, 02:47:28 PM »

Didn't you state that the SRX 728 was too heavy?  You know the TH115 is pretty close to the same weight and well above your $1000.00 price limit.
Yeah, but if a TH115 can replace two <$2,000 subs, the price is okay.
Size and weight are a big issue here. *However*, one person can tote the TH115 around, including tilting it into the back of a pickup. One person can't handle an SRX 728s (or else we wouldn't be having this discussion).

To me, the big issue with the TH115 right now is that it's shape is fixed. It's easier to pack two single 18" cubes than the TH115 (or the SRX 728s, for that matter).

In another thread, someone mentioned the RCF subs. Looking into *one* of those, as well. However, there is no question in my mind that a TH115 would do the job if I could get it to *fit* into my "pickup pack".
Cheers,
Randy Hyde
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Randall Hyde

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Re: PRX 718 XLF vs ?
« Reply #9 on: August 26, 2014, 02:48:28 PM »

I often work a rig with a VRX 918s used for drum fill. Sometimes I'm provided an XTi 4000 for power, sometimes an iTech 6000. The XTi has a hard time getting enough output from the 918s before clipping, while the 6k works well. Obviously we're talking two very different amplifiers, and in this case the sub is being used by itself, not in multiples, but thought I'd chime in with the experience.
That's good to know. I actually have an iTech 6K laying around (used as a spare). I assume you were bridging the XTi?
cheers,
Randy Hyde
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Re: PRX 718 XLF vs ?
« Reply #9 on: August 26, 2014, 02:48:28 PM »


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