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PostPosted: Mon Dec 04, 2017 2:35 pm 
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Good day all. I read this Forum looking for my specific answer but couldn't find it.

I am new to Forum so please be gentle. I helped my associate build 4 Titans a while back and we finally built 2 for myself. I now have 2 x T39 30'' Wide with Dual 3012LF (4Ohms). Below was both my procedure for limiting my DriveRack Pa2 as well as question(s), clarification of procedure. Thanks in advance.

1. Downloaded a 60 Hz Tone and played it through my Serato and out of a Mackie Mixer. Made sure that the Mackie Board was at 0db.
2. I bridged a QSC RMX2450 and with no Speakers connected turned up to 55 Volts.
3. Set -6d Limiter with Over Easy Off on Drive Rack for Low end. This seems to be working correctly because I can turn up DJ and Mackie Mixers into red but 55 Volts remain the same as the amp output.
4. I switched from the 60 Hz Tone and played a Hip-Hop song with decent bass..... Meter only spiked to about 32 Volts max

QUESTION - Should I be using "Real World" or Recorded Music and set limiter to maybe 50 Volts or is this 55 Volts from the 60 Hz Tone the correct point of setting speaker handling limits? Xover point was 45 with one T39 hooked up. I may do 42.5K when both are being driven as per something I read on 2 30'' Dual from Mr. Fitzmaurice. Would it be catastrophic for speakers if I limit to the 45-50 Volts using a good bass example from regular music?

Another question - I think the RMX 2450 is rated at 650W Stereo at 4Ohms. Even if it may barely reach 55 volts for 2 boxes, it would still be better professionally speaking to have a bit more headroom correct? I am thinking of 2 XLS 2002 or 1 XTi 4002.

I wanna give as much info as possible - Why 2 Dual? - Pack Space - 4 T39 at 20'' Wide will not fit in my vehicle. These 2 30'' just fit. I am eying some tops for sale in the Forum but I have to sell some Powered stuff first. These were tough to build.

Thanks in advance,
Richness

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2xT39 30'' 3012LF Dual.


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PostPosted: Mon Dec 04, 2017 3:17 pm 
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Location: Ilfracombe Queensland Australia
Richness wrote:
1. Downloaded a 60 Hz Tone and played it through my Serato and out of a Mackie Mixer. Made sure that the Mackie Board was at 0db.

Check

2. I bridged a QSC RMX2450 and with no Speakers connected turned up to 55 Volts.
3. Set -6d Limiter with Over Easy Off on Drive Rack for Low end. This seems to be working correctly because I can turn up DJ and Mackie Mixers into red but 55 Volts remain the same as the amp output.

Something hasn't worked out right here I think.
A bridged RMX2450 outputs 1300W/8ohms and that's 101V. I don't think a -6dB setting on the limiter is going to reduce output by 46V.
Set the attenuators to max, and use the limiter to end up with a figure of 55V output. In other words, keep decreasing the dB reduction until output in volts is correct.
It wouldn't surprise me if you came back to us and said "I can't seem to reduce output by 46V with the limiter, it doesn't have enough reduction".
On your driverack, you should see the limiter light engaging at 55V if you have done it right.


4. I switched from the 60 Hz Tone and played a Hip-Hop song with decent bass..... Meter only spiked to about 32 Volts max

QUESTION - Should I be using "Real World" or Recorded Music and set limiter to maybe 50 Volts or is this 55 Volts from the 60 Hz Tone the correct point of setting speaker handling limits?

The 60Hz sine wave is the right tool for the job to set limits

Would it be catastrophic for speakers if I limit to the 45-50 Volts using a good bass example from regular music?

It could be

Another question - I think the RMX 2450 is rated at 650W Stereo at 4Ohms. Even if it may barely reach 55 volts for 2 boxes, it would still be better professionally speaking to have a bit more headroom correct? I am thinking of 2 XLS 2002 or 1 XTi 4002.

Your RMX does 50V at 4 ohms/channel. Yes, some headroom is preferable.
If you can find amps with the correct output and avoid bridging, that's the way to go...



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Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...


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PostPosted: Mon Dec 04, 2017 3:55 pm 
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Location: Medicine Hat, Alberta, Canada
Richness wrote:
Hip-Hop song with decent bass..... Meter only spiked to about 32 Volts max


That's because your DMM doesn't read fast enough to measure music. The sine wave is a steady signal that it can read accurately.

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Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience


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PostPosted: Mon Dec 04, 2017 4:12 pm 
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Location: Austin, Texas
Richness wrote:
2. I bridged a QSC RMX2450 and with no Speakers connected turned up to 55 Volts.


Were the gain knobs on the amp at full, or only high enough to read 55 volts on the meter?

_________________
2xJ15, THT, 4xT39 3012 (2x15", 2x20"), 2xSLA Pro, 2x short SLA Pro (Dayton), W6


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PostPosted: Mon Dec 04, 2017 6:38 pm 
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Posts: 8
Thanks a million for the feedback gentlemen. Sorry for the late response I was expecting an email notification if a response was entered.

Thank you @ CoronoOperator - makes sense

whines wrote:
Richness wrote:
2. I bridged a QSC RMX2450 and with no Speakers connected turned up to 55 Volts.


Were the gain knobs on the amp at full, or only high enough to read 55 volts on the meter?


YES sir @ whines Thanks

@ Grant Bunter - I did what Whines is asking about.
I slowly increased the gain on the amp to get to 55 volts when I bridged the RMX 2450. I made a little mark to remember the spot. It was about 9:30 on the Amp. Can I do it this way and be sure not to increase the amp? When I did it this way the 55 V output at the amp remained the same even if I went past clipping on the mixer. I am not sure about maxing out the gains plus I may eventually have different amps with different power ratings. What Amp would you recommend for my bass set up now to run 4 ohm stereo on these 2 bins?

I liked the logic of using even 2 XLS 1500 or 2002 in Bridged mode so if one goes out then I still have some bass. Instead of relying on 1 amp for all my bass needs. Told you I have been reading for a couple hours...lol

_________________
2xT39 30'' 3012LF Dual.


Last edited by Richness on Tue Dec 05, 2017 2:20 pm, edited 1 time in total.

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PostPosted: Mon Dec 04, 2017 7:09 pm 
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Joined: Mon Nov 28, 2011 11:12 am
Posts: 5665
Location: Ilfracombe Queensland Australia
Richness wrote:
whines wrote:
Were the gain knobs on the amp at full, or only high enough to read 55 volts on the meter?


YES sir @ whines Thanks

Setting a voltage in this fashion is asking for trouble, and it's not voltage limiting. Say some dude decides you're not loud enough, grabs the amp attenuators, and winds them to max. I'm pretty sure you can work out what happens next.

@ Grant Bunter (fixed that for you) - I did what Whines is asking about.
I slowly increased the gain on the amp to get to 55 volts when I bridged the RMX 2450. I made a little mark to remember the spot. It was about 9:30 on the Amp. Can I do it this way and be sure not to increase the amp?
No, refer to my answer above.
When I did it this way the 55 V output at the amp remained the same even if I went past clipping on the mixer. I am not sure about maxing out the gains plus I may eventually have different amps with different power ratings.

Sure, but it's not voltage displacement limiting, and that's one of the features that you bought a driverack to do.
Go back to your plans and re read and thoroughly understand "protecting your drivers".
Especially the bit about transients. They happen to fast to read on a multimeter, but that is one of the things that will blow your drivers.
When you've set things up properly, you should see the limiter light come on at 55V.

If you change amps, go back and start all over again with limiting.


What Amp would you recommend for my bass set up now to run 4 ohm stereo on these 2 bins?
Something with say 70V output at 4 ohms per channel, about 1200W.

I liked the logic of using even 2 XLS 1500 or 2002 in Bridged mode so if one goes out then I still have some bass. Instead of relying on 1 amp for all my bass needs. Told you I have been reading for a couple hours...lol
Not really lol, you must have missed:
viewtopic.php?f=10&t=19292

Some people regularly bridge for subs. The person who immediately springs to mind is Bruce Weldy.
He will tell you he's not had any problems doing that, but he is also a super experienced SE with years, no, decades, under his belt, and knows (more often than not hehehehe) exactly what he is doing. That's not the case with you.

If you can get amps that prevent having to bridge, and still have enough output, that's got to be a good thing right?



_________________
Built:
2 x DR 250 (melded array) with March 2012 plans.
4 x 20" BP102 T39's, 2 x 28" 3012lf loaded underway.
3 x WH8 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...


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PostPosted: Mon Dec 04, 2017 8:18 pm 
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Joined: Mon Dec 04, 2017 10:16 am
Posts: 8
Lol, It was Bruce's input I was following. Ok I guess I will look into a Xti4002. Sorry for not getting your last name correct. Thanks again for your assistance guys.

_________________
2xT39 30'' 3012LF Dual.


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PostPosted: Tue Dec 05, 2017 12:02 am 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6127
Location: New Braunfels, TX
Richness wrote:
Lol, It was Bruce's input I was following. Ok I guess I will look into a Xti4002. Sorry for not getting your last name correct. Thanks again for your assistance guys.


The xTi4002 should do the trick nicely. My rig grew into my current amp configuration, but there have been pluses to doing it the way I do. However, starting from scratch - the single amp should be your best bet.

If you go with smaller amps bridged, then the 1500s would be sufficient. Don't get the 2000 - it's too much power.

_________________

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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PostPosted: Tue Dec 05, 2017 8:16 am 
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Location: Huddersfield, UK
Richness wrote:
@ Grant Buttler - I did what Whines is asking about.


The most misquoted name on this forum. Ever. :lol:


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PostPosted: Tue Dec 05, 2017 9:46 am 
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Location: Austin, Texas
Richness wrote:
Thanks a million for the feedback gentlemen. Sorry for the late response I was expecting an email notification if a response was entered.

Thank you @ CoronoOperator - makes sense

whines wrote:
Richness wrote:
2. I bridged a QSC RMX2450 and with no Speakers connected turned up to 55 Volts.


Were the gain knobs on the amp at full, or only high enough to read 55 volts on the meter?


YES sir @ whines Thanks

@ Grant Buttler - I did what Whines is asking about.
I slowly increased the gain on the amp to get to 55 volts when I bridged the RMX 2450. I made a little mark to remember the spot. It was about 9:30 on the Amp. Can I do it this way and be sure not to increase the amp? When I did it this way the 55 V output at the amp remained the same even if I went past clipping on the mixer. I am not sure about maxing out the gains plus I may eventually have different amps with different power ratings. What Amp would you recommend for my bass set up now to run 4 ohm stereo on these 2 bins?

I liked the logic of using even 2 XLS 1500 or 2002 in Bridged mode so if one goes out then I still have some bass. Instead of relying on 1 amp for all my bass needs. Told you I have been reading for a couple hours...lol


As others have pointed out, turning gain to full and THEN setting limiters is safer. That's what I do.

_________________
2xJ15, THT, 4xT39 3012 (2x15", 2x20"), 2xSLA Pro, 2x short SLA Pro (Dayton), W6


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PostPosted: Tue Dec 05, 2017 1:56 pm 
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Bruce Weldy wrote:
Richness wrote:
Lol, It was Bruce's input I was following. Ok I guess I will look into a Xti4002. Sorry for not getting your last name correct. Thanks again for your assistance guys.


The xTi4002 should do the trick nicely. My rig grew into my current amp configuration, but there have been pluses to doing it the way I do. However, starting from scratch - the single amp should be your best bet.

If you go with smaller amps bridged, then the 1500s would be sufficient. Don't get the 2000 - it's too much power.


After doing the gain and limiting process as instructed yesterday I am getting 50.4 Volts out of the RMX 2450 with the very rare red light clip. I think for now I will keep this amp (although this beast is HEAVY) for now to run these 2 dual T39s.

Bruce, I may go the route of bridging the XLS 1502 route if I decide to build or buy 2 more Single T39s. From assessing all options, 3 of the same model amps would be my best bet because I can set them all at max and limit them to the same voltage. I would use 1 on each dual T39 and 1 for a pair of sinlges down the road. Right now they are loud enough for me but bass is addictive like boost (turbo) so you never know.

Thanks again

_________________
2xT39 30'' 3012LF Dual.


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PostPosted: Tue Dec 05, 2017 2:03 pm 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6127
Location: New Braunfels, TX
Richness wrote:
Bruce Weldy wrote:
Richness wrote:
Lol, It was Bruce's input I was following. Ok I guess I will look into a Xti4002. Sorry for not getting your last name correct. Thanks again for your assistance guys.


The xTi4002 should do the trick nicely. My rig grew into my current amp configuration, but there have been pluses to doing it the way I do. However, starting from scratch - the single amp should be your best bet.

If you go with smaller amps bridged, then the 1500s would be sufficient. Don't get the 2000 - it's too much power.


After doing the gain and limiting process as instructed yesterday I am getting 50.4 Volts out of the RMX 2450 with the very rare red light clip. I think for now I will keep this amp (although this beast is HEAVY) for now to run these 2 dual T39s.

Bruce, I may go the route of bridging the XLS 1502 route if I decide to build or buy 2 more Single T39s. From assessing all options, 3 of the same model amps would be my best bet because I can set them all at max and limit them to the same voltage. I would use 1 on each dual T39 and 1 for a pair of sinlges down the road. Right now they are loud enough for me but bass is addictive like boost (turbo) so you never know.

Thanks again


That's the main reason I stayed with multiple amps instead of a single for four plus one for two. Makes it hard to set the limiter if the amps aren't exactly the same. I run two cabs off of each amp bridged. Or, you could step up to one of the new QSC 4 channel amps and handle all the subs and tops too.

_________________

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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PostPosted: Tue Dec 05, 2017 8:17 pm 
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Location: San Rafael, CA
6dB is a doubling of Voltage. So if the amp is capable of ~100V and he set the limiter to -6dB to get the output at 55V that sounds about right.

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Built:
1 Omni-15 Tall Boy
2 DR250s
2 Titan 39s


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PostPosted: Tue Dec 05, 2017 9:08 pm 
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billkatz wrote:
6dB is a doubling of Voltage. So if the amp is capable of ~100V and he set the limiter to -6dB to get the output at 55V that sounds about right.


I hope my meter is correct at this. I had to set the Driverack limiter at -17.5db to get to 50 Volts and out of clipping. Stereo 4ohm per Channel. I used the Parallel mode of the QSC. Mono output from DriveRack to Channel 1and used both Speakon from Amps. I think this is right since I got same voltage readings for both channels.

The -6db to get to 55 u mentioned has me unsure now.

_________________
2xT39 30'' 3012LF Dual.


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PostPosted: Tue Dec 05, 2017 10:02 pm 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6127
Location: New Braunfels, TX
Richness wrote:

The -6db to get to 55 u mentioned has me unsure now.


Forget the math.....the only thing that matters is the voltmeter. Just adjust the limiter until you get where you want to be.

_________________

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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