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Author Topic: DSP setup  (Read 15611 times)

Nathan Riddle

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DSP setup
« on: February 12, 2016, 01:35:31 pm »

I have 4x QSC K12s, 2x TH118's, 2x RMX2450s, 1x DBX studio (original model)

Need to figure out best settings for a dsp for my setup:
*crossover point
*time delay [for correct phase response]
*limiting settings

I have been trying to learn about how to properly setup the dsp for our small sound system. I've been researching to properly phase align not time align systems and I understand what needs to happen electrically/acoustically. What I'm lacking is material on HOW to do it properly.

I feel like any material I have read is indirectly related to my problem and more directly related to building speakers or crossovers etc. I'm fine with learning more about everything, but I need the specifics related to my setup not how to build some random analogue crossover.

I'm not looking for handouts, I'm looking to learn. If I could get links to past threads or articles on how to do it properly that would be great. I'm looking to understand not just be handed a set of parameters (while I'd love that too simply because I'm partly loosing my mind after all of this research and having gotten nowhere).

I'm also to get a new dsp as ours is old and sometimes the screen flickers off randomly and the unit resets. Suggestions welcome. I'm thinking Ashley or xilliica ~500-1k range...used - because it is cheaper. What I really want is a rms limiter on the subs so that I can have other crews run the system without worrying that it is being run too hard so that thermal damage occurs. I'm pretty sure that only happens in the amp though and I only know of iTechs that do that.
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Jonathan Betts

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Re: DSP setup
« Reply #1 on: February 12, 2016, 01:59:26 pm »

Lol! I'm in the process of doing some testing on a similar setup.



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Nathan Riddle

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Re: DSP setup
« Reply #2 on: February 12, 2016, 02:28:46 pm »

Lol! I'm in the process of doing some testing on a similar setup.

Well that's fantastic! Tell me/us how it goes! I think eventually I'll want that SM80 setup I think you have pictured there  :).
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Scott Slater

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Re: DSP setup
« Reply #3 on: February 13, 2016, 09:37:41 am »

The K speakers don't need any processing, since it's already built in.  The switch on the back should be set for "Sub Mode", which adds a 100Hz HPF, so your crossover point for your subs should be around there somewhere as well.  I would use an RTA and pink noise to even it out as much as possible.

Time delay will be different for each show depending on placements of the individual speakers.
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Scott Slater

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Re: DSP setup
« Reply #4 on: February 13, 2016, 10:00:45 am »

One more thing to add:  For the TH118s set an HPF at 25Hz w/24dB Butterworth if your DSP device supports it.  The LPF on the sub, with the K's should be somewhere around 85-100.  The RTA will help you get it to the best setting.
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Ivan Beaver

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Re: DSP setup
« Reply #5 on: February 13, 2016, 11:44:28 am »

I have 4x QSC K12s, 2x TH118's, 2x RMX2450s, 1x DBX studio (original model)

Need to figure out best settings for a dsp for my setup:
*crossover point
*time delay [for correct phase response]
*limiting settings

I have been trying to learn about how to properly setup the dsp for our small sound system. I've been researching to properly phase align not time align systems and I understand what needs to happen electrically/acoustically. What I'm lacking is material on HOW to do it properly.

I feel like any material I have read is indirectly related to my problem and more directly related to building speakers or crossovers etc. I'm fine with learning more about everything, but I need the specifics related to my setup not how to build some random analogue crossover.

I'm not looking for handouts, I'm looking to learn. If I could get links to past threads or articles on how to do it properly that would be great. I'm looking to understand not just be handed a set of parameters (while I'd love that too simply because I'm partly loosing my mind after all of this research and having gotten nowhere).

I'm also to get a new dsp as ours is old and sometimes the screen flickers off randomly and the unit resets. Suggestions welcome. I'm thinking Ashley or xilliica ~500-1k range...used - because it is cheaper. What I really want is a rms limiter on the subs so that I can have other crews run the system without worrying that it is being run too hard so that thermal damage occurs. I'm pretty sure that only happens in the amp though and I only know of iTechs that do that.
How are you running the 2450s on the TH118s?  are they bridged?  And bridged PROPERLY?  I say properly because very often people simply flip the bridge switch and hook them up normally.

Also the ch 2 on the 2450s MUST BE TURNED ALL THE WAY DOWN!!!!!!!!!

Are the speakers hooked between the two PLUS terminals?

If you don't all sorts of weird things start to happen to sound-and not in a good way.

The only way to get a good phase alignment (the only proper method of aligning) is to use a measurement system that shows phase.  That is a whole 'nother can of worms.

You can get an alignment at one freq in which the cabinets sum just fine-but they cancel freq either higher or lower.  You can't use the "send a freq at the crossover freq and adjust time" method and know what is happening AROUND the crossover freq.

And RTA can help a little-but there are so many things wrong with using an RTA that you have to be careful.

Regarding limiting-that depends on a lot of different factors.

Some of which include depending on what sort of limiting is available in the particular processor.  The "recommended settings" may not be available-so you have to use something different.

So first we need to know what the parameters of the tools are.

Do you have a voltmeter?

Basically this is NOT a "step by step" process. There are a lot of variables that will depend on a particular situation-and then a different path needs to be taken-to put in a step by step procedure.

Yes there are some general guidelines-but with a lot of "fill in the blank" sections.

Congratulations for wanting to do it the right way and understand what is going on.

But it needs to be taken in a small chunk at a time process.

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Jonathan Betts

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Re: DSP setup
« Reply #6 on: February 13, 2016, 02:59:34 pm »

FWIW, I ended up using  a 12db Butterworth @ 35Hz, HP and  a 24db Bessel @98Hz on the TH118. I also inverted the polarity(th118) and added 1.5ms of delay to the k12. This was done using the processing in a IT 4000 and AH QU-24.
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Nathan Riddle

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Re: DSP setup
« Reply #7 on: February 14, 2016, 01:05:51 am »

Thanks for the responses. I've tried hard to take and understand the concept of "it depends" to heart and try to understand the complex underlying components at work that change things. I feel like the issue for me now is I've reached a certain level of knowledge that allows me to see how much I don't know or understand with sound and it is rather daunting to move pass that. I feel I lack either sufficient knowledge or tools or both to properly setup a sound system, people may like my input and what I do generally helps people, but I still feel very far from hitting the mark. And I've tried to turn here and actually posted a question to help me get to the point instead of waiting for it to surface in the knowledge.

That all being said. Let's get to some answers!

The K speakers don't need any processing, since it's already built in.  The switch on the back should be set for "Sub Mode", which adds a 100Hz HPF, so your crossover point for your subs should be around there somewhere as well.  I would use an RTA and pink noise to even it out as much as possible.

Time delay will be different for each show depending on placements of the individual speakers.

My logic behind not using the K speakers in "sub mode" is because i'm not sure what the slope of the HPF, what type or if it is even at 100hz. I felt that leaving it in as much of a full range point source I could control it better with proper dsp usage.

I'm not trying to time delay in the sense of aligning HF sound arrival to LF sound arrival as that is only good for a few points in the room. I'm trying to utilize time delay to correct for phase mismatching at the crossover point, but perhaps i am confused here and that also only occurs at a few points in the room (random revelation perhaps).

One more thing to add:  For the TH118s set an HPF at 25Hz w/24dB Butterworth if your DSP device supports it.  The LPF on the sub, with the K's should be somewhere around 85-100.  The RTA will help you get it to the best setting.

I believe just as Jonathan Betts stated I have my HPF around 30hz @ 24dB/oct BW I wanted some extra spl and giving up some of the super low notes we usually don't use wasn't a big deal. they still give us a wow when music goes low :)

Thanks, Ivan, I realize not knowing much about my current setup starting with the basics is probably a good idea. I'll try to answer everything you have stated. That being said I really appreciate all of your posts about considering all of the angles in sound and that there is no simple answer -hah, paraphrased your signature without realizing it-.


How are you running the 2450s on the TH118s?  are they bridged?  And bridged PROPERLY?  I say properly because very often people simply flip the bridge switch and hook them up normally. Each is bridged. Red binding posts used to custom speakon connector using 12ga wire. ch2 is all the way down. The 30hz filter is off (because they can go lower + dsp [stated above]) clip limiting is on.

Also the ch 2 on the 2450s MUST BE TURNED ALL THE WAY DOWN!!!!!!!!!

Are the speakers hooked between the two PLUS terminals?

If you don't all sorts of weird things start to happen to sound-and not in a good way.

The only way to get a good phase alignment (the only proper method of aligning) is to use a measurement system that shows phase.  That is a whole 'nother can of worms.

You can get an alignment at one freq in which the cabinets sum just fine-but they cancel freq either higher or lower.  You can't use the "send a freq at the crossover freq and adjust time" method and know what is happening AROUND the crossover freq.

Hmm, okay that makes sense given the crossover messing with phase/amplitude above/below the xover point. (I just researched this so I'm trying to incorporate this caveat in xover tuning properly)

And RTA can help a little-but there are so many things wrong with using an RTA that you have to be careful.

If RTA is used in outdoors (free field, I believe is correct term) would that help eliminate the inherent limitations with RTA? I know FFT is really whats needed, but I don't think we really don't need to spend money on FFT (while I would love it simply to learn more) when pros have done gigs for years without it.

Regarding limiting-that depends on a lot of different factors.

Yeah, and I think I might have hurt myself with this one. I limited at the peak of the 2450's which is more than the continuous power of the TH118's and now sometimes when one heats up it can stink badly. so yeah... another story :P I'd really like an Itech so that I can set thermal, rms, and peak limiters and not worry about cooking anything ever...(hopefully), but things like wireless mics and light are more important than an amp that will only gain us 3-5db. Though honestly, what is your opinion on a new amp? would an itech or PL380 be that much better than the rmx to justify the cost?

Some of which include depending on what sort of limiting is available in the particular processor. not much. just an over-easy peak limiter...  The "recommended settings" may not be available-so you have to use something different.

So first we need to know what the parameters of the tools are.

Do you have a voltmeter? yup, dc-amp, ac-amp, vac or vdc, plus an o-scope.

Basically this is NOT a "step by step" process. There are a lot of variables that will depend on a particular situation-and then a different path needs to be taken-to put in a step by step procedure.

I'm all ears for learning more and doing this process with help. I think i'd just like some more bang for my buck.

Yes there are some general guidelines-but with a lot of "fill in the blank" sections.

I think i'm searching for the "correct" blank parts, i'm logical and i try to understand but I am afraid I might assume something incorrectly as I've already done with the limiting (thinking the peak limiter would keep me safe) 

Congratulations for wanting to do it the right way and understand what is going on.

But it needs to be taken in a small chunk at a time process.

FWIW, I ended up using  a 12db Butterworth @ 35Hz, HP and  a 24db Bessel @98Hz on the TH118. I also inverted the polarity(th118) and added 1.5ms of delay to the k12. This was done using the processing in a IT 4000 and AH QU-24.

Sweet i'll look into that. I think what I want to try next is instead of boosting subs on the amps and messing up the crossover point (which is why I have my mains at 100hz and subs at I think 90hz to help fix the acoustic crossover point. I don't think I ever liked the sound of the Bessel but then again I liked LR 2x gigs ago on the system but the last gig I couldn't get it to sound good no matter what xover type I used. So I feel a bit humbled and now I want to learn some more; take the system out to a field and give it a good tuning.
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Ivan Beaver

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Re: DSP setup
« Reply #8 on: February 14, 2016, 10:11:21 am »

I would not get new amps.  The ones you have are a good match for the subs.

HOWEVER, let's dig into the limiter you have a bit.

What sort of controls does your current limiter offer?  And what is the range of the controls?

Knowing that will help in setting up the limiters with a volt meter.

Rather than me giving you some numbers and then you saying your DSP doesn't have those numbers- let me know what sort of "choices" I have to work with.

It is faster/easier that way.

Yes an RTA outside is a bit better-ASSUMING there are no other noises outside-like traffic etc.

But there are ways to kinda get around that.

But let's do one thing at a time.

Personally I prefer a 24dB BUtterworth on the highpass on the subs.

It gets rid of the stuff the subs can't do better.

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Nathan Riddle

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Re: DSP setup
« Reply #9 on: February 14, 2016, 01:24:50 pm »

I would not get new amps.  The ones you have are a good match for the subs. Interesting you say that. While I understand we won't get much more db out of them by increasing wattage going to them I feel like a better amp would make them sound better and give us a little more punch from the added program level peak hitting power. Given how many people rave about how musical they sound, I was hoping new amps might give them some more impact or gumption. Obviously the bang for the buck isn't there; but I was at least hoping for more sound quality. And i'm not going to replace them anytime soon. But we're probably getting 1 or 2x more TH118's in the future so i'm trying to figure out the best amp by doing my research. I felt like the i-techs would be best because of the protection (which at this point for me is a huge deal, since we're usually running things pretty near capacity) plus the added benefit of more power.

HOWEVER, let's dig into the limiter you have a bit. I have attached an image of the manual. As you can see there is a threshold and a over-easy feature. I want to get a better dsp both for sound quality and for better limiting (since amps with dsp will be a long time down the road). Perhaps xilica if it sounds good [i have one i'm going to A/B with]

What sort of controls does your current limiter offer?  And what is the range of the controls?

Knowing that will help in setting up the limiters with a volt meter.

Rather than me giving you some numbers and then you saying your DSP doesn't have those numbers- let me know what sort of "choices" I have to work with.

It is faster/easier that way.

Yes an RTA outside is a bit better-ASSUMING there are no other noises outside-like traffic etc.

But there are ways to kinda get around that.

But let's do one thing at a time.

Personally I prefer a 24dB BUtterworth on the highpass on the subs. Yup that's done. It is at least at the recommended freq (closest the xover gets is 25hz) or it is a bit higher probably around 30hz; at least last I tuned it was.

It gets rid of the stuff the subs can't do better.

I don't have the dsp with me now as the gear is in storage, but I want to go get it and work on it today/tomorrow.
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ProSoundWeb Community

Re: DSP setup
« Reply #9 on: February 14, 2016, 01:24:50 pm »


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