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Junior Varsity
JBL SRX / QSC PL236 underpowered?
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<blockquote data-quote="Silas Pradetto" data-source="post: 82115" data-attributes="member: 34"><p>Re: JBL SRX / QSC PL236 underpowered?</p><p></p><p>There is way too much calculating and theorizing going on in this thread. Here's how you figure this out:</p><p></p><p>1. Set up the DSP with the JBL-provided tunings. They suggest an 80Hz lowpass on the subs, which I would NOT increase, and a 80Hz highpass on the tops, which you could increase depending on how much buildup in the 80Hz range you end up with. There are significant implications to changing the crossover. It's not a bad thing to do, but will change phase alignment between tops and subs. Try to keep things where JBL suggests and use input EQ to tune the PA. (You want to use the input EQ as using output EQ will only equalize one passband, and therefore also change the phase alignment between passbands).</p><p></p><p>2. Set up amps stereo on the tops and bridged on the subs. Take note that bridging an amp immediately adds 6dB of gain, so unless the amp offers bridged gain compensation, you will need to gain the amp down 6dB to keep things even.</p><p></p><p>3. Run the rig at a gig. </p><p></p><p>This leaves the question: does it get loud enough?</p><p></p><p>If it does, leave it.</p><p></p><p>If it doesn't, get more rig.</p><p></p><p>After using the SRX stuff pretty regularly, it will take pretty much all the peak power you can throw at it. However, purchasing an amp that can deliver 3000 watts per box doesn't really make any sense, because all that extra power could only be used on peaks, and depending on limiters, melt the coils pretty easily. The money spent on a huge amp could be spent on more subs, and more cones is always better than more power. (Still, I was hitting my SRX subs with a LOT of power and it does make a difference. I was right at the limit of what could be done with 4 double 18s though).</p><p></p><p>Regarding clarity:</p><p></p><p></p><p></p><p>This is called mixing. I would not consider it a bad thing. </p><p></p><p>Regarding crossover:</p><p></p><p></p><p></p><p>There is only a recommendation for the crossover point. Note that subs have a high pass (low cut) and a low pass (high cut) to limit their passband. The 31Hz is the highpass and is to prevent overexcursion below box tuning. Do NOT change or ignore this. The low pass is the 80Hz spec, and this is subject to adjustment. Higher is possible, but they need EQ otherwise there is significant buildup in the 80-100 range. I like my SRX subs at 80Hz, and I still end up cutting 80 usually. See above for some other crossover implications.</p></blockquote><p></p>
[QUOTE="Silas Pradetto, post: 82115, member: 34"] Re: JBL SRX / QSC PL236 underpowered? There is way too much calculating and theorizing going on in this thread. Here's how you figure this out: 1. Set up the DSP with the JBL-provided tunings. They suggest an 80Hz lowpass on the subs, which I would NOT increase, and a 80Hz highpass on the tops, which you could increase depending on how much buildup in the 80Hz range you end up with. There are significant implications to changing the crossover. It's not a bad thing to do, but will change phase alignment between tops and subs. Try to keep things where JBL suggests and use input EQ to tune the PA. (You want to use the input EQ as using output EQ will only equalize one passband, and therefore also change the phase alignment between passbands). 2. Set up amps stereo on the tops and bridged on the subs. Take note that bridging an amp immediately adds 6dB of gain, so unless the amp offers bridged gain compensation, you will need to gain the amp down 6dB to keep things even. 3. Run the rig at a gig. This leaves the question: does it get loud enough? If it does, leave it. If it doesn't, get more rig. After using the SRX stuff pretty regularly, it will take pretty much all the peak power you can throw at it. However, purchasing an amp that can deliver 3000 watts per box doesn't really make any sense, because all that extra power could only be used on peaks, and depending on limiters, melt the coils pretty easily. The money spent on a huge amp could be spent on more subs, and more cones is always better than more power. (Still, I was hitting my SRX subs with a LOT of power and it does make a difference. I was right at the limit of what could be done with 4 double 18s though). Regarding clarity: This is called mixing. I would not consider it a bad thing. Regarding crossover: There is only a recommendation for the crossover point. Note that subs have a high pass (low cut) and a low pass (high cut) to limit their passband. The 31Hz is the highpass and is to prevent overexcursion below box tuning. Do NOT change or ignore this. The low pass is the 80Hz spec, and this is subject to adjustment. Higher is possible, but they need EQ otherwise there is significant buildup in the 80-100 range. I like my SRX subs at 80Hz, and I still end up cutting 80 usually. See above for some other crossover implications. [/QUOTE]
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