XTI 4000 DSP For Titan 48's

[jon moore]

I know this subject has been beaten in ground but I am a little unclear.

I have 2 T48's that I will be run 1 per channel on my XTI 4000. They will be hp filtered around 40hz.

My amplifiers software has limit settings of 3db,6db,and 12db. which one should I use?

Again, I know you guys will tell me this is beating a dead horse but I really would like some help.

Thanks, Jon

[DJ Big Ronn]

I know this subject has been beaten in ground but I am a little unclear.

I have 2 T48's that I will be run 1 per channel on my XTI 4000. They will be hp filtered around 40hz.

My amplifiers software has limit settings of 3db,6db,and 12db. which one should I use?

Again, I know you guys will tell me this is beating a dead horse but I really would like some help.

Thanks, Jon

I would chose 12db for the most protection.

[bzb]

Go buy an el cheapo multimeter from Radio Shack ($10).

Hook your mixer up to the amplifier. Turn on the mixer and amp. Do not hook up speakers to the amp.

Download a noise generator, or burn noise to a CD. Play this through your mixer at whatever is the max setting you'll have on the mixer (max without clipping/peaking in the red).

Turn the gains up all the way on the amplifier.

Turn on the multimeter and set it to AC current. Touch the leads to the outputs on the amp - the screw plugs.

The number shown is the voltage coming out of the amp.

On the front panel, change the limiter setting to -3dB. Click through the rest of the option until the setting name is showing again on the screen. Check the voltage again. Now change to -6dB, then to -12dB, taking measurements. Whichever results in the voltage limit suggested is the one you use (60v for the 3015LF). The resulting voltage a little under is better than it being a little over.

[DJ Big Ronn]

Oh yeah, I almost forgot LOL

[DJ Big Ronn]

Go buy an el cheapo multimeter from Radio Shack ($10).

Hook your mixer up to the amplifier. Turn on the mixer and amp. Do not hook up speakers to the amp.

Download a noise generator, or burn noise to a CD. Play this through your mixer at whatever is the max setting you'll have on the mixer (max without clipping/peaking in the red).

Turn the gains up all the way on the amplifier.

Turn on the multimeter and set it to AC current. Touch the leads to the outputs on the amp - the screw plugs.

The number shown is the voltage coming out of the amp.

On the front panel, change the limiter setting to -3dB. Click through the rest of the option until the setting name is showing again on the screen. Check the voltage again. Now change to -6dB, then to -12dB, taking measurements. Whichever results in the voltage limit suggested is the one you use (60v for the 3015LF). The resulting voltage a little under is better than it being a little over.

I think he's talking about Hi-pass?

[bzb]

I think he's talking about Hi-pass?

Dunno, his question was about the limiter setting (-3, -6, -12).

High pass can't be set on the front panel. Well, it can't on the XTi 1000... I would assume they all have the same software.

[DJ Big Ronn]

I think he's talking about Hi-pass?

Dunno, his question was about the limiter setting (-3, -6, -12).

High pass can't be set on the front panel. Well, it can't on the XTi 1000... I would assume they all have the same software.

The 40hz threw me off, I assumed he was asking about hi-pass.

[jon moore]

I forgot to mention I am using the 3015lf driver.

Also, the question is about limiting. I have the system architect software for my amp and the limit options are 3db,6db, and 12db

I am hi pass filtering around 40 hz

I knew the dead horse smilies were coming.

Thanks,Jon

[Ron K]

Run your HPF @35-40HZ @ 48db per octave Butterworth. That should get you the most low end extension possible without hurting the driver. You could actually go a bit lower since you can provide a very steep cliff of a rolloff with the XTIs DSP capabilities but I doubt that will add anything worth value.

It's impossible to say where to run the limiters as the amount of voltage you feed the amp and how much attenuation you add or subtract from the input plays a roll in how much output voltage you get from the amp.

Do a search and you'll learn how to properly set up limiters.With the XTIs you simply adjust the available of the 4 settings to get what output voltage you need with the inputs run fully open.Adjust the input attenuators after for the desired SPLs.

It's probably helpful to also learn how to set up proper gain structure. I cannot stress this point. Most systems I am asked to look at because the operator or system designer cannot figure out why it sounds so bad. Usually they start with how powerful their amps are (doesn't really matter) and how much cash they spent.The most powerful amp in the world will sound like ass if the signal feeding it sounds like ass, unless you have some sort of magical unasser! You can try the Study Hall over at Pro Sound Web. Lots of good little tricks and plenty of learning there.

[jon moore]

Thanks for all the info. It has all been helpfull

Jon

[Landl.livesound]

Hey Jon,

I would add that it might be a very good idea to not lower the limiter lower than the 0dB standard. For what it is worth the XTi limiters really don't sound that good at all, I had heard this and then got to play with one just a while ago and I concur. (Now if looking for a good limiter the iTech series has some of the best built in limiters I've seen. I personally would actually switch over from QSC to iTech's if my rack wasn't already almost completed with QSC.)

Also with a T48 hanging off each channel with peaks just starting to clip the amp, each driver should only be seeing peaks of up to 550 watts (nominal impedance of the T48 is 10 ohms, if I recall correctly). So as long as the music that is coming through it has a crest factor of some sort the drivers will handle it with ease. Usually you can count on un-clipped music to have a crest factor of at least ~6dB, which means at the moment your XTi4000 starts to clip the average power going to each driver will only be around the 138 watts, which the VC should handle with no problem. (Now if you are playing dubstep, drums and bass, or anything with a very low low-end crest factor, because then you will really have to watch how much heating power you are sending to those drivers.)


So I would say leave the limiter at 0dB and right when you see the clip/limiter light start to blink lightly on peaks you know that's all you got.


Take Care!