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Author Topic: JBL STX825 how many SRX81SP  (Read 926 times)

Sean Zurbrick

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Re: JBL STX825 how many SRX81SP
« Reply #10 on: March 14, 2019, 05:02:01 pm »

While I agree you could have more subs per top box if you want a universal setup that will work outdoors, it seems odd that you have no noticeable increase in low end at all.

Are you using the crossover in the 6002 and your 818SP? If not that would be the first place I'd look. I see the 818SP can be crossed over as low as 60 Hz. Given your tops are double 15's, that's where I'd start.  I just can't tell from the Crown manual if the 6002 can be set lower than 90 Hz. It has a "custom" crossover function but I don't see any documentation on what that means. So if the amp will do it, experiment with 60-80 crossover setting. Being under-subbed in some situations, you may find this doesn't work all the time as you might get more mid-bass from your top boxes than low lows from 1 sub per side.

Another thing to check is that you aren't running the tops out of phase with the subs. That would have them fighting each other and cancelling out some of the low end. You also can get come cancellation if you're in phase but running full signal to the tops so they are duplicating the sub frequencies. Some setups play better with doing that than others.  Worst would be if you are doing both - full frequency tops and out of phase with the subs.

500-600 people is a big reception for sure, but as a guy that's done ~200 wedding receptions, there aren't many time I could have maxed out a 4 sub / 2 top system and kept everyone happy. When "dance time" starts I generally toe in the mains to focus on the dance floor and the system is running on cruise control, and that's with a live band. But outdoor is a different story, particularly on the low end.
« Last Edit: March 14, 2019, 07:26:16 pm by Sean Zurbrick »
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Rick Powell

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Re: JBL STX825 how many SRX81SP
« Reply #11 on: March 14, 2019, 06:28:48 pm »

Another question, i am thinking about why the srx 812p and srx815p have 2000 crown amp and the srx818sp have only 1000 crown amplification
1. I don't have experience but many times have been told that cranking up the gain on the SRX sp boxes is done by some people to offset the low gain sensitivity.
2. Maybe the higher wattage because they are dual amplifiers in the 812 and 815, electronic crossover between the speaker and the horn, and probably underutilizing the amp side that is going to the horn.
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Scott Bolt

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Re: JBL STX825 how many SRX81SP
« Reply #12 on: March 15, 2019, 07:28:07 am »

While I agree you could have more subs per top box if you want a universal setup that will work outdoors, it seems odd that you have no noticeable increase in low end at all.

Are you using the crossover in the 6002 and your 818SP? If not that would be the first place I'd look. I see the 818SP can be crossed over as low as 60 Hz. Given your tops are double 15's, that's where I'd start.  I just can't tell from the Crown manual if the 6002 can be set lower than 90 Hz. It has a "custom" crossover function but I don't see any documentation on what that means. So if the amp will do it, experiment with 60-80 crossover setting. Being under-subbed in some situations, you may find this doesn't work all the time as you might get more mid-bass from your top boxes than low lows from 1 sub per side.

Another thing to check is that you aren't running the tops out of phase with the subs. That would have them fighting each other and cancelling out some of the low end. You also can get come cancellation if you're in phase but running full signal to the tops so they are duplicating the sub frequencies. Some setups play better with doing that than others.  Worst would be if you are doing both - full frequency tops and out of phase with the subs.

500-600 people is a big reception for sure, but as a guy that's done ~200 wedding receptions, there aren't many time I could have maxed out a 4 sub / 2 top system and kept everyone happy. When "dance time" starts I generally toe in the mains to focus on the dance floor and the system is running on cruise control, and that's with a live band. But outdoor is a different story, particularly on the low end.

Same here Sean.  Of course most weddings include some older people so you canít open up the system until later in the night.

I also donít see how there would be no difference in low end when adding two 18 subs.  I have a neighbor with a QSC system like this.  It thumps pretty hard.

To get the system balanced so the tops can be opened up for larger venues,  you will need 2X18 per side.  It is more expensive to use single 18ís for this; however, you can carry it much easier and it allows for scaling down for a smaller venue
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Will Knight

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Re: JBL STX825 how many SRX81SP
« Reply #13 on: March 15, 2019, 05:11:20 pm »

Hello to everyone
I own 2 jbl stx825 amplified with 1 crown xti6002, i recently owned 2 srx818sp.
The bass from the subs is very little in comparison the bass from the stx. How many srx818sp i must have to have correct system audio output? To feel the bass from the srx818sp's

You have not said yet how you're connecting these units to your mixer (and what type of mixer)?  Are you going direct?  Using Aux Sends for the Subs? using a Loudspeaker Processor?  What are the attenuator settings on the Amp? 818's? There's only 1dB difference in Max SPL between the STX825 and SRX818SP at Peak (NOT watts). Depending on your crossover settings and whether you have a SubSynth enable (it should be OFF), you should notice a difference with the 818's.  But as been mentioned already, if you can handle the size, get 1 828 and use it along with the 2 818's.   
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Glen Hansen

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Re: JBL STX825 how many SRX81SP
« Reply #14 on: March 15, 2019, 10:09:59 pm »

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Kiriakidis Christos

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Re: JBL STX825 how many SRX81SP
« Reply #15 on: March 24, 2019, 09:02:24 am »

My system is pioneer cdj400/djm400 -> soundcraft signature 12mtk. The main output of soundcraft goes to 2 x xti2002 bridged (2000 watts each stx825, sometimes i put -1 db the limiterand  goes to 1600 watts) and the 2 subgroups goes to srx818sp. I was insert the presets for stx to the xti via audio architecht. I have not cut the laws of the stx because they have plenty of them and they play them very loud and clear.
« Last Edit: March 24, 2019, 09:08:52 am by Kiriakidis Christos »
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Patrick Cognitore

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Re: JBL STX825 how many SRX81SP
« Reply #16 on: March 25, 2019, 01:22:45 pm »

Is is possible that that the gain staging going to the subs is not quite right? Are you able to get full output from the subs with your current routing - can you run the subs into limit form the group outputs?

Are the groups assigned to mains? If so, the main outs may have a bit more gain than the group outs and that won't help your cause.

Since you're just doing music playback have you tried feeding the subs from the main outs by using the link outs from the amps? This may not solve the above issue but will simplify routing.

Also, since you're running the tops full range is it possible that the tops and subs are not in phase in the range of overlapped low frequencies? Single 18's can only do so much, but you should definitely hear a difference when combining them with the STX tops, if the outputs of all speakers are summing properly. Where are the HPF and LPF of the SRX subs set? And the HPF of the STX tops?

I agree with others that more subs are needed to optimize the system's output, but I'd make sure that everything else is set up correctly and getting the most out of it before investing in more subs.

My system is pioneer cdj400/djm400 -> soundcraft signature 12mtk. The main output of soundcraft goes to 2 x xti2002 bridged (2000 watts each stx825, sometimes i put -1 db the limiterand  goes to 1600 watts) and the 2 subgroups goes to srx818sp. I was insert the presets for stx to the xti via audio architecht. I have not cut the laws of the stx because they have plenty of them and they play them very loud and clear.
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