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Author Topic: SRX718s help needed  (Read 2846 times)

Plamen Milev

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SRX718s help needed
« on: September 19, 2021, 06:18:19 PM »

Hi,

I have 2xSRX718s and would like to power them in parallel mode on a bridged QSC [email protected]
My question is what power I should limit them to?
For limiter I use DCX2496 and measure voltage output with multimeter and pink noise.
The RMX4050 can run [email protected] and I was thinking to limit to [email protected] or 80v
Is this OK?

Thank you.
« Last Edit: September 19, 2021, 06:21:16 PM by Plamen Milev »
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Chris Grimshaw

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Re: SRX718s help needed
« Reply #1 on: September 20, 2021, 02:48:03 AM »

Yep, it'll probably save your woofers from too-high peak levels.

However, the simple peak limiter on a DCX2496 can't monitor the long-term average power levels which can often burn out drivers. If you want to make sure the speakers never burn out, you either to lock down the peak limiter until the drivers don't even get warm (ie, you lose a lot of potential output), or use an amplifier or limiter that can monitor the average power level.

One of the reasons I went with the Powersoft T-series amps is that they can monitor the real power being dissipated in the loudspeaker.

Chris
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Tracy Garner

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Re: SRX718s help needed
« Reply #2 on: September 20, 2021, 03:21:36 PM »

Hi,

I have 2xSRX718s and would like to power them in parallel mode on a bridged QSC [email protected]
My question is what power I should limit them to?
For limiter I use DCX2496 and measure voltage output with multimeter and pink noise.
The RMX4050 can run [email protected] and I was thinking to limit to [email protected] or 80v
Is this OK?

Thank you.

I run a 718 pair in stereo with an iTech8000 which is 2100wpc @8ohm. I haven't found the need to use a limiter. The same thing with the 728. There are some older threads here where you will get specific info on how to limit this combination.
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Paul Johnson

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Re: SRX718s help needed
« Reply #3 on: September 20, 2021, 04:26:13 PM »

I've got 4 VRX918s which are pretty much the same cabinet and had a series of shows to do with them - running unlimited from two amps - one speaker to each output. Power wise at max, probably too much - but as the sound ops were all in the know, I figured few problems. It was a new VRX PA, so new to all of us. The shows were comedians and tribute bands - so think Queen, Michael Jackson, Abba, The Drifters, Four season. Nothing metal or mega. In fact - the contractual requirement was mainly for the Comedians, and The Drifters, not the tributes. However, most of them asked if they could use our PA rather than their own because it fit the shape and size of the auditorium - low roof, 1400 seats on a rake and wide and deep. First mistake was saying yes, but biggest mistake was NOT putting the old speaker crossover in the system. This was run from an X32 with crossover duties done in the desk - but no limiter engaged. We thought it unnecessary.

The Queen show pushed the volume - very loud at the mix position but also a long way, so it was excruciating at the front. The PA actually managed fine and was just too loud. Deaf band op? I don't know but no issues. We did have issues with one of the shows which was, frankly, a train wreck. Equipment failures meant their tracks, via Qlab were not all available in the mix - it sounded very strange and they tried to compensate with volume, but worst, mega amounts of bass. RMS the amp was capable of 1200W into one sub, and we lost one of the subs - nasty clicking type sounds on the transients, when investigated next day. A new driver has arrived so I'll fit it, and we used a spare similar sub for the following shows with no incident once we inserted a limiter into the X32. The Behringer amps with the built in zero attack limiters were powering the one pair of subs, but the other amp was a different brand without the limiters. Some of the Queen songs are VERY bass heavy and with the limiter in, plus the amp limiter - the system was safe even though mega loud. The screwed up mix from the train wreck show was just a mess up top but kick and bass guitar at the bottom and unpleasant to listen to. I now know that loud bass with the just in case limiter is safe - but with no limiter - too dangerous.
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Plamen Milev

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Re: SRX718s help needed
« Reply #4 on: September 20, 2021, 04:49:31 PM »

I run a 718 pair in stereo with an iTech8000 which is 2100wpc @8ohm. I haven't found the need to use a limiter. The same thing with the 728. There are some older threads here where you will get specific info on how to limit this combination.
My worry is that I play pre-recorded music (djing) so in my case [email protected] bridged seems to me like asking for trouble.

I've got 4 VRX918s which are pretty much the same cabinet and had a series of shows to do with them - running unlimited from two amps - one speaker to each output. Power wise at max, probably too much - but as the sound ops were all in the know, I figured few problems. It was a new VRX PA, so new to all of us. The shows were comedians and tribute bands - so think Queen, Michael Jackson, Abba, The Drifters, Four season. Nothing metal or mega. In fact - the contractual requirement was mainly for the Comedians, and The Drifters, not the tributes. However, most of them asked if they could use our PA rather than their own because it fit the shape and size of the auditorium - low roof, 1400 seats on a rake and wide and deep. First mistake was saying yes, but biggest mistake was NOT putting the old speaker crossover in the system. This was run from an X32 with crossover duties done in the desk - but no limiter engaged. We thought it unnecessary.

The Queen show pushed the volume - very loud at the mix position but also a long way, so it was excruciating at the front. The PA actually managed fine and was just too loud. Deaf band op? I don't know but no issues. We did have issues with one of the shows which was, frankly, a train wreck. Equipment failures meant their tracks, via Qlab were not all available in the mix - it sounded very strange and they tried to compensate with volume, but worst, mega amounts of bass. RMS the amp was capable of 1200W into one sub, and we lost one of the subs - nasty clicking type sounds on the transients, when investigated next day. A new driver has arrived so I'll fit it, and we used a spare similar sub for the following shows with no incident once we inserted a limiter into the X32. The Behringer amps with the built in zero attack limiters were powering the one pair of subs, but the other amp was a different brand without the limiters. Some of the Queen songs are VERY bass heavy and with the limiter in, plus the amp limiter - the system was safe even though mega loud. The screwed up mix from the train wreck show was just a mess up top but kick and bass guitar at the bottom and unpleasant to listen to. I now know that loud bass with the just in case limiter is safe - but with no limiter - too dangerous.

That's exactly why I feel the limiter is a must and since I have DCX2496(A+B for tops and C for sub(sum of A+B)) and DEQ2496 I have no excuse not to set it. The thing is I have no experience with the speakers (SRX718s) and hence my post.
I did a gig and had limiters set up to [email protected] bridged but my tops couldn't keep up with the subs so I had to reduce the gain on the bass. They were 300W continious each. I now have Yamaha S115V rated at 500W continious each so time to revise my set up.
I also stack my SRX together for extra dB gain and always against a wall.
« Last Edit: September 20, 2021, 04:53:02 PM by Plamen Milev »
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Mike Caldwell

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Re: SRX718s help needed
« Reply #5 on: September 20, 2021, 07:32:04 PM »

I've got 4 VRX918s which are pretty much the same cabinet and had a series of shows to do with them - running unlimited from two amps - one speaker to each output. Power wise at max, probably too much - but as the sound ops were all in the know, I figured few problems. It was a new VRX PA, so new to all of us. The shows were comedians and tribute bands - so think Queen, Michael Jackson, Abba, The Drifters, Four season. Nothing metal or mega. In fact - the contractual requirement was mainly for the Comedians, and The Drifters, not the tributes. However, most of them asked if they could use our PA rather than their own because it fit the shape and size of the auditorium - low roof, 1400 seats on a rake and wide and deep. First mistake was saying yes, but biggest mistake was NOT putting the old speaker crossover in the system. This was run from an X32 with crossover duties done in the desk - but no limiter engaged. We thought it unnecessary.

The Queen show pushed the volume - very loud at the mix position but also a long way, so it was excruciating at the front. The PA actually managed fine and was just too loud. Deaf band op? I don't know but no issues. We did have issues with one of the shows which was, frankly, a train wreck. Equipment failures meant their tracks, via Qlab were not all available in the mix - it sounded very strange and they tried to compensate with volume, but worst, mega amounts of bass. RMS the amp was capable of 1200W into one sub, and we lost one of the subs - nasty clicking type sounds on the transients, when investigated next day. A new driver has arrived so I'll fit it, and we used a spare similar sub for the following shows with no incident once we inserted a limiter into the X32. The Behringer amps with the built in zero attack limiters were powering the one pair of subs, but the other amp was a different brand without the limiters. Some of the Queen songs are VERY bass heavy and with the limiter in, plus the amp limiter - the system was safe even though mega loud. The screwed up mix from the train wreck show was just a mess up top but kick and bass guitar at the bottom and unpleasant to listen to. I now know that loud bass with the just in case limiter is safe - but with no limiter - too dangerous.

I hope you did some on the spot contract re-negotiation got paid extra to deal with that!!!

Brian Jojade

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Re: SRX718s help needed
« Reply #6 on: September 20, 2021, 10:11:43 PM »

My worry is that I play pre-recorded music (djing) so in my case [email protected] bridged seems to me like asking for trouble.

That's exactly why I feel the limiter is a must and since I have DCX2496(A+B for tops and C for sub(sum of A+B)) and DEQ2496 I have no excuse not to set it. The thing is I have no experience with the speakers (SRX718s) and hence my post.
I did a gig and had limiters set up to [email protected] bridged but my tops couldn't keep up with the subs so I had to reduce the gain on the bass. They were 300W continious each. I now have Yamaha S115V rated at 500W continious each so time to revise my set up.
I also stack my SRX together for extra dB gain and always against a wall.

Be careful with using a limiter, as it may make things WORSE not better.  While a limiter is great for taming fast high power peaks, that rarely is what kills subs. HF drivers are more often blown out with that sort of problem.

With subs, it's the average power over time that's usually going to be a problem.  With the dynamic range of music, hitting peaks means your average power is significantly below that peak.  However, if you throw a limiter in the equation, you now eliminate those peaks and the average power can go UP, thus increasing the chance for damage.

Putting a peak limiter on subs and hoping for it to provide protection means you need to massively reduce the capabilities of the speaker for effective protection.
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Paul Johnson

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Re: SRX718s help needed
« Reply #7 on: September 21, 2021, 02:52:18 AM »

The bit about renegotiation made me smart. Pre-covid, I decided that Id but the VRX system for my band because we flew out to do a show on a beach, and the provided PA was a VRX system. These get pretty poor internet comment because theyre not a line array, but people hate them. All of us including our sound guy thought they worked really for us. The theatre I look after is seasonal, so six weeks in the summer and the elderly EAW was perfectly OK but tired. The idea was to tour the VRX with the band and use it for six weeks in the theatre. The price here in the UK was almost full retail because nobody had them in stock, so I sourced them from dealers in Europe and one pair of 932 cabinets came from the US. They all arrived and I put them in the cases Id bought and three days later Covid hit. They sat in the store unused and the warranty expired. During covid the band leader was very ill and he cant sing, and our guitarist had a new mortgage on a house and got a full time job. Band is finished after over twenty years. I put the PA into the theatre at my choice, the venue unwilling to even consider a hiking if the agreed rate, so with just a few shoes left, its not yet recovered its cost by a long way, but it was paid for in my accounts for the past period and I guess I paid less tax. 4 subs, 8 tops and one blown already because I thought Id be in control of what people did with it, and I messed up. As its the first blown driver in probably 30 years, I guess the old system, that people used as extra to their own toured ones, was safe, while now, people see the new system and want to use it as a total replacement, and push too far.
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Plamen Milev

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Re: SRX718s help needed
« Reply #8 on: September 22, 2021, 05:34:13 AM »


With subs, it's the average power over time that's usually going to be a problem.  With the dynamic range of music, hitting peaks means your average power is significantly below that peak.  However, if you throw a limiter in the equation, you now eliminate those peaks and the average power can go UP, thus increasing the chance for damage.

Putting a peak limiter on subs and hoping for it to provide protection means you need to massively reduce the capabilities of the speaker for effective protection.

I take this onboard, it makes sense to me. It also gives me an idea that the limiter should be closer to the continious power rating of the speakers for pre-recorded music. I think I should go for 80-97V measured at the output of the RMX4050. Maybe closer to 80V. Surely at the set up and check stage before a gig I can see if I'm hitting those limiters and take note of my levels at the mixer stage.
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Paul Johnson

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Re: SRX718s help needed
« Reply #9 on: September 22, 2021, 06:35:06 AM »

I'm not convinced setting precise voltage limits prevents damage, because we have heat based damage, but also physical damage by 'over-excursioning' - I'm not at all sure that these drivers, with their odd design with big heat sinks gets damaged from continuous loud signals, but the sudden quite violent movements faults and clipping make them do? I have no proof at all - it's just a feeling, so I'm now looking at how effective these quick limiters can be at toning down these sudden, destructive peaks, rather than the overall level. I have no idea if this is a solution apart from what's happened recently and the failure I've had with a simply nasty sounding show, while a louder, continuous level show that was more 'musical' caused no grief?
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ProSoundWeb Community

Re: SRX718s help needed
« Reply #9 on: September 22, 2021, 06:35:06 AM »


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