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Author Topic: JBL SRX835p for FOH Mains review  (Read 28748 times)

Scott Carneval

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Re: JBL SRX835p for FOH Mains review
« Reply #10 on: February 09, 2016, 09:16:52 am »

Here is the gated response I did at 1m using REW and MiniDSP Umic with cal file. As you can see the 3 way has a pretty narrow beam width compared to the more traditional 2 ways. (60 deg vs 90) So I believe the splay is correct. Any more, and there was an audible hole in the centre isle.
I've tried to bring up the dip at 2.5k and drop the peak at 12k. But that 12k peak could be the culprit. This week I intend to RTA and EQ around the room with my mic and laptop, and get it flatter. This is using the DBX 260, but I wondering if I would get better results with the new JBL iPad app for EQ, Just need to run a network cable up to the speakers.
Keep you posted.


That dip you're seeing is probably a cancellation due to either a reflection (maybe off of the metal ceiling) or interference from the other box. You said you got a hole when you splayed them further than 30 degrees...could it have been cancellation causing a dip in HF instead? Are they splayed 30 total, or 30 per box?

RTA is really not the correct tool for this. You need a multi-channel measurement system so you can run a transfer function.
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Samuel Rees

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JBL SRX835p for FOH Mains review
« Reply #11 on: February 09, 2016, 09:33:16 am »

Multichannel measurement is definitely recommended here rather than an RTA. Try using level measurement to determine the splay angle and see what that comes up with compared to what you have now. Measure one box out to -6 and then place and measure the other box such that it reaches -6 at the same spot. You may be splaying them too narrow in an attempt to get perfect coverage in the overlap area which isn't really going to happen when splaying two fairly wide boxes. I think the reason everyone here suspects splay is the boxes look pretty close in the pictures and too much overlap could very easily produce unappealing peaks and valleys in the high frequency, which fits your complaint well.

My other thought is that your preferences based on your home listening environment don't necessarily correlate to a specific measurement or tuning outcome. If you like more HF, add it, or don't.
« Last Edit: February 09, 2016, 09:44:59 am by Samuel Rees »
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David Sturzenbecher

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Re: JBL SRX835p for FOH Mains review
« Reply #12 on: February 09, 2016, 10:15:21 am »

The OP should also post back if he like the HF of just one box, and if it gets worse or better with the second box turned on.


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Cailen Waddell

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Re: JBL SRX835p for FOH Mains review
« Reply #13 on: February 09, 2016, 01:27:45 pm »


You've also got the weight of the hardware, which probably isn't much, but then the weight of the chain, which will be a considerable amount. If it's lightweight chain it's probably not rated. If it's rated chain it's probably not lightweight. Not trying to bust your balls here, but this isn't something to be taken lightly (pun not intended). If an engineer certified the rig, fine, but it needs to be mentioned for the sake of others reading this post.

And to further play devils advocate - engineered drawing or not, if you use a manufacturers product in a way other than it was designed and it fails... Good luck with any liability suit against the manufacturer for a failure of their product.


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Jonathan Johnson

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Re: JBL SRX835p for FOH Mains review
« Reply #14 on: February 09, 2016, 01:52:47 pm »

The speakers are 85lbs each. It was reviewed and approved by two different engineers.

Was the review of the design or of the installation? Did the review include the mounting to the structural steel? Was the hardware used as specified by the engineer? Not all eye bolts are created equal.

What stands out to me is the eye bolt going into the side of the roof purlin. It appears that most of the force is downward, meaning that there is a bending moment on the shaft of the bolt. This places a twisting force on the purlin; the force on the purlin is not evenly distributed around the hole, but rather is concentrated at the top (outward) and bottom (inward) with almost no force applied at the sides.

From my non-engineer "armchair engineering" viewpoint, I would have expected to see the eye bolt inserted into the flange of the purlin, placing the stress more axially along the bolt shaft rather than radially as it is now. It appears that all other suspended items are supported by the flange rather than the side of the purlin.

The rule-of-thumb margin of safety for overhead suspended loads is 10:1. (For loads not suspended overhead, it's generally 3:1.) If your load is 180 pounds (170 pounds for speakers plus another 10 for hardware), the suspension system must be rated for 1800 pounds. The failure of a single link should not result in catastrophic failure resulting in collapse. The loads need to be analyzed to determine the dynamic loading (including angles, which will change in a failure) on the other links should any one fail.
« Last Edit: February 09, 2016, 02:07:00 pm by Jonathan Johnson »
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David Allred

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Re: JBL SRX835p for FOH Mains review
« Reply #15 on: February 09, 2016, 03:54:13 pm »

For load rated hardware a design factor of (typically) 4x is used.  Meaning that an eye-bolt with a SWL, WLL, SL, etc of 400 lbs will not fail until 1600 lbs (if used properly).  I am not suggesting going beyond 400 lbs, but rather that 400 lbs is guaranteed (and twice on Sundays).  90 degrees loads on eyebolts is outside their design parameters.
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Trevor Crowe

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Re: JBL SRX835p for FOH Mains review
« Reply #16 on: February 09, 2016, 05:05:46 pm »

There are 5 mounting points. The eyebolts are m10 mcmaster carr rated at 1600 lbs verticle. Assuming 20% for side load that is 360lbs each. 170lbs total divided by the 3 main front mounts(the 2 back are mainly for tilting). But I do agree, they should have been mounted on the bottom of the flange, with 2" washers on both sides.
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g'bye, Dick Rees

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Re: JBL SRX835p for FOH Mains review
« Reply #17 on: February 09, 2016, 05:05:54 pm »

Agreed. 

Sound here is WAAAY down the list after dealing with the safety (and liability) issues. 

First:  make it safe
Second:  make it safe
Third:  make it safe

Edit:

Chain is not acceptable for flying loads overhead.

Where are the safeties?
« Last Edit: February 09, 2016, 05:20:11 pm by dick rees »
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Scott Carneval

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Re: JBL SRX835p for FOH Mains review
« Reply #18 on: February 09, 2016, 05:53:55 pm »

There are 5 mounting points. The eyebolts are m10 mcmaster carr rated at 1600 lbs verticle. Assuming 20% for side load that is 360lbs each. 170lbs total divided by the 3 main front mounts(the 2 back are mainly for tilting). But I do agree, they should have been mounted on the bottom of the flange, with 2" washers on both sides.

McMaster Carr rates their M10 eyebolts for up to 45 side loading. They are also de-rated to 20% at 45.

http://www.mcmaster.com/#eyebolts/=111zhgo

20% of 1600 is 320lbs.

You're still forgetting to include the weight of the hardware, as it is also suspended from the eyebolts.

I looked on the JBL website and my 01/2016 JBL dealer price sheet, I don't see any sort of splay/cluster brackets available for the SRX835. Did the ones in your picture come from JBL? If not, do they have a PE stamp?







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Jonathan Johnson

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Re: JBL SRX835p for FOH Mains review
« Reply #19 on: February 09, 2016, 06:14:16 pm »

Quote from: everybody
...blah blah engineering blah blah...proper rigging...blah blah...life safety...blah blah

Lest you get discouraged, please understand that the folks here want you to have a safe installation above all else. We're happy to help, but anything that looks like a potential physical hazard WILL get addressed before any technical issues.

Of course, no one here can MAKE you do things right; we just want to make sure you to understand the risks of not doing things right. We're also trying to help you make wise judgement so you, yourself can be better able to spot when something's not right.

Sometimes it seems the folks here are hard on newbies. Try not to take it personally. Take heart, we really DO want you to get the best sound possible out of your system. Safely.

But if you refuse to acknowledge unsafe situations, then you will receive no mercy.
« Last Edit: February 09, 2016, 06:17:12 pm by Jonathan Johnson »
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ProSoundWeb Community

Re: JBL SRX835p for FOH Mains review
« Reply #19 on: February 09, 2016, 06:14:16 pm »


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