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 Post subject: Help tuning T48's
PostPosted: Tue Apr 18, 2017 6:16 pm 
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Joined: Sun Sep 28, 2014 5:21 am
Posts: 25
Location: Melbourne
Hi guys,

Before we delve into it, some specs on my setup:
2x 24inch wide T48's loaded with Eminence 3015 LF's
1x QSC GX7 amplifier
1x DBX Driverack Pa+

So, Im having a bit of difficulty with my system. I've got it going, and it sounds loud enough, but I'm not super happy with the character of the sound. As a friend said recently, it lacks the "boom" that you typically expect from a large sub (just for reference I play pretty much exclusively electronic, tech, minimal, etc).

In terms of the driverack, im running -6db of limiter, with an over easy of 2 to help softern the limiters effect. This is where i think the first issue arrises. When driving the signal from the mixer to the rack, you can see the limiter kicking in very early (the headroom meter for the low end barely lights up at the bottom, and you can see the limiter kicking in at the top of that meter. This is really throwing me as the signal coming off the mixer isn't clipped, its typically well within safe levels.

In terms of the eq of the Titan, its makes noise, but I feel like it shoud be much better. The bass doesn't seem to have much authority, and the kick tends to have a weird almost clang or slap to it at higher levels, which doesnt feel right at all. I had them apart recently, to check for air rush, and it turned out there was some, but they are now tight as a drum... at least around the driver and driver cover.

Any advice would be much appreciated. Also if anyone has some settings for the DBX that you're willing to share with me, both for the setup, and eq I would be most greatful.

Thanks in advance.


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 Post subject: Re: Help tuning T48's
PostPosted: Tue Apr 18, 2017 7:25 pm 
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Joined: Mon Nov 28, 2011 11:12 am
Posts: 5647
Location: Ilfracombe Queensland Australia
I use something else, but IIRC for the Driverack series, over easy should be off.
You want the limiter to hit when it needs to, so you want a hard knee.
AFS should be off too.

Please explain to us the entire process you used to set your limiter. ie signal at how many Hz, what sort of mixer, signal input to unity gain or no, master outputs to unity gain or no, crossover points and slope and type etc etc.

Other than that, if you never used or heard horn subs before, but only listened to DR subs, then, horn subs can take a while to get used to.
Horn subs naturally filter harmonics, which is the cause the "boom" associated with DR subs.
When horn subs are sorted though, they are often described as loud, low and tight.

Clang or slap could be the driver hitting the access panel brace, or to tight a tolerance on the driver mount, something worth checking.

Finally, don't trust your ears, by guessing output. Measure output with an SPL meter, so you know what's going on...

_________________
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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 Post subject: Re: Help tuning T48's
PostPosted: Tue Apr 18, 2017 8:43 pm 
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Joined: Tue Jul 29, 2008 12:56 pm
Posts: 1867
Location: Tucson, AZ
If you're running one or two cabs, you need to set the LPF a lot lower than you think you need. Most people start at 80hz. :cop: Instead, start low (like 35-40hz), adjust the gain up to get the punch back, then adjust up again from there. You'll likely settle on somewhere between 40-70hz using 12-18 dB oct slope.

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 Post subject: Re: Help tuning T48's
PostPosted: Tue Apr 18, 2017 11:13 pm 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
First of all, make sure you are using the limiter and not the compressor. Turn the compressor totally off. Do not use the over easy function.

Did you set your limiter with a voltmeter to get at the -6db setting? Run us through the process you used.

_________________

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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 Post subject: Re: Help tuning T48's
PostPosted: Tue Apr 18, 2017 11:14 pm 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
Radian wrote:
If you're running one or two cabs, you need to set the LPF a lot lower than you think you need. Most people start at 80hz. :cop: Instead, start low (like 35-40hz), adjust the gain up to get the punch back, then adjust up again from there. You'll likely settle on somewhere between 40-70hz using 12-18 dB oct slope.



Do you mean the HPF? I'm not understanding what you are describing here.

_________________

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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 1:05 am 
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Joined: Mon Nov 28, 2011 11:12 am
Posts: 5647
Location: Ilfracombe Queensland Australia
Bruce Weldy wrote:
Radian wrote:
If you're running one or two cabs, you need to set the LPF a lot lower than you think you need. Most people start at 80hz. :cop: Instead, start low (like 35-40hz), adjust the gain up to get the punch back, then adjust up again from there. You'll likely settle on somewhere between 40-70hz using 12-18 dB oct slope.



Do you mean the HPF? I'm not understanding what you are describing here.


What Radian means is to utilize the subs natural rising response.
High pass remains the same as per plans for the amount of cabs in use.

Make the Low pass lower as Radian described above, but because of the natural rising response from sub, in the case of the T48, from 70Hz and upwards, and a gentler slope, you don't end up with a hole as you might expect.

Another way to skin that cat you might say...

_________________
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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 3:41 am 
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Joined: Sun Sep 28, 2014 5:21 am
Posts: 25
Location: Melbourne
Thanks for the quick response guys. I've got time in my workshop tomorrow night so I can sit down with them and go through the above points. The limiter was set using the 60hz sine wave through the driverack and manually checking the voltage across the amp terminals method. That said it was done some time ago, and so I will do it again tomorrow as I now have a pioneer djm 800 to push the signal out to the dbx.
As for the sound of horn subs, most of my time is spent around funktion 1 systems at festivals, so I do appreciate the difference. Mine just feel gutless :(
I've got the driverack at home, and looking at it now, I did have some compression active, and overeasy on the limiter activated as well. This was on the advice of a sound guy down here... I'm now questioning his merits. Afs is not activated.
The crossover is:
HP 40Hz, BW 24, 0.0 db.
LP 100Hz, LR 12.
Few novice questions, why is the HP the low end (40hz) and LP (100Hz) the top end? The language is counterintuitive...
Also when setting the limiter and you refer to unity on the mixer, that is going to be "0" on the master output of my DJM?

Thanks again, sorry for the limited knowledge.


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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 4:07 am 
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Joined: Tue Jul 29, 2008 12:56 pm
Posts: 1867
Location: Tucson, AZ
Bruce Weldy wrote:
Radian wrote:
If you're running one or two cabs, you need to set the LPF a lot lower than you think you need. Most people start at 80hz. :cop: Instead, start low (like 35-40hz), adjust the gain up to get the punch back, then adjust up again from there. You'll likely settle on somewhere between 40-70hz using 12-18 dB oct slope.



Do you mean the HPF? I'm not understanding what you are describing here.
No. I meant it exactly as it's typed.
Grant Bunter wrote:
Another way to skin that cat you might say...
The right way to skin the cat. The cabs aren't flat unless there's a pile of them. Using the LPF contours the power response without the use of EQ and establishes the bottom half of a constant-voltage network. :ugeek:

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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 4:19 am 
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Joined: Wed Mar 25, 2009 7:07 pm
Posts: 1291
Location: Medicine Hat, Alberta, Canada
Basshund wrote:
When driving the signal from the mixer to the rack, you can see the limiter kicking in very early (the headroom meter for the low end barely lights up at the bottom, and you can see the limiter kicking in at the top of that meter.


Play a 60 hz tone, at what voltage (measured with a dmm set to AC volts) does the limiter turn on?

_________________
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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 4:20 am 
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Joined: Mon Nov 28, 2011 11:12 am
Posts: 5647
Location: Ilfracombe Queensland Australia
Basshund wrote:
I've got the driverack at home, and looking at it now, I did have some compression active, and overeasy on the limiter activated as well. This was on the advice of a sound guy down here... I'm now questioning his merits. Afs is not activated.
The crossover is:
HP 40Hz, BW 24, 0.0 db.
LP 100Hz, LR 12.
Few novice questions, why is the HP the low end (40hz) and LP (100Hz) the top end? The language is counterintuitive...
Also when setting the limiter and you refer to unity on the mixer, that is going to be "0" on the master output of my DJM?


Sounds like you set the limiter correctly, but, if it was some time ago, pays to check.
Always set limiters with no cabs attached.
The final test is if you slide your outputs to max suddenly, and max output voltage for your voltage displacement limit on the amp doesn't change. If it does, it's not set right.

Yes unity would be zero on the master out.
Lots of DJ's love running their mixers above zero, into the red. You should avoid that, as it simply introduces distortion and sounds terrible. If you need more volume, add more cabs!

HP isn't counterintuitive, it only became confused once some people didn't understand what it actually means.
Car audio, and HT manufacturers and users are some examples of those who started using the terms incorrectly in some instances.

High pass actually refers to a filter that only allows frequencies above a certain cutoff frequency to be directed to the driver(s).
Similarly, LP only allows frequencies below a certain cutoff frequency to pass.
Neither HP nor LP are vertical lines if you were to see their effect on an SPL chart, because the filters fall off at xdB per octave, depending on the filter design.

So, for subs, you can have a high pass to protect your driver from over excursion, a low pass so you're not trying to reproduce the frequencies your tops/mains are reproducing, then a high pass on your tops/mains so they are freed up to reproduce what they do best because they are not also trying to reproduce lower frequencies...

_________________
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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 8:53 am 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
Grant Bunter wrote:
High pass actually refers to a filter that only allows frequencies above a certain cutoff frequency to be directed to the driver(s).
Similarly, LP only allows frequencies below a certain cutoff frequency to pass.
Neither HP nor LP are vertical lines if you were to see their effect on an SPL chart, because the filters fall off at xdB per octave, depending on the filter design.



Another way to say it is:

High Pass = Low Cut
Low Pass = High Cut

Those terms are often used on mixers and sometimes lead to confusion.....

_________________

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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 10:19 am 
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Joined: Tue Apr 30, 2013 5:56 pm
Posts: 656
Location: Colonial Beach VA
Hi Pass = lets highs pass through.
Low Pass = lets lows pass through.

Hi Passing the subs is what seems counterintuitive.

You need to make sure that content below what the loudspeaker is designed for doesn't get to it and let the magic smoke out.

Horns don't give you a warning. Just smoke.

High Pass (40Hz) and Low Pass (100Hz) the subs.

For the mains, no need to feed them what the subs are already taking care of.

High Pass (100Hz) the mains.

Hope this helps.

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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 10:44 am 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
Radian wrote:
Bruce Weldy wrote:
Radian wrote:
If you're running one or two cabs, you need to set the LPF a lot lower than you think you need. Most people start at 80hz. :cop: Instead, start low (like 35-40hz), adjust the gain up to get the punch back, then adjust up again from there. You'll likely settle on somewhere between 40-70hz using 12-18 dB oct slope.



Do you mean the HPF? I'm not understanding what you are describing here.
No. I meant it exactly as it's typed.


Ok, so you are saying to set the LPH at 35-45hz? If you do that and the HPF is supposed to be set at 40hz for 2-T48s, then you would get nothing.

I still don't understand at all what you are suggesting here.....not arguing, I just have no idea what you mean at all.

_________________

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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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 2:12 pm 
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Joined: Tue Jul 29, 2008 12:56 pm
Posts: 1867
Location: Tucson, AZ
Bruce Weldy wrote:
Ok, so you are saying to set the LPH at 35-45hz?
It's just a starting point.

What really makes no sense, and is the root of this thread, is that a four foot tall subwoofer has no "guts" because it's not getting enough voltage below 100 Hz. It is essentially a waste of space. Likewise with y'all fussing over limiters and the high pass for just the same. Break out the meter and take a look.

Listen to the cab first....then apply the filters. Not the other way around.

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 Post subject: Re: Help tuning T48's
PostPosted: Wed Apr 19, 2017 2:15 pm 
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Joined: Mon Jun 30, 2014 8:07 pm
Posts: 271
Location: Berea, Kentucky
Bruce Weldy wrote:

Ok, so you are saying to set the LPH at 35-45hz? If you do that and the HPF is supposed to be set at 40hz for 2-T48s, then you would get nothing.

I still don't understand at all what you are suggesting here.....not arguing, I just have no idea what you mean at all.



+1

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4 Jack 112L- 3012HO, melded array
2 Jack 112 (bought), straight array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF


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