Lab 12 recone kits

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CoronaOperator
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#16 Post by CoronaOperator »

Attenuating just the peaks isn't leaving the signal intact.

A "peak limiter" is a compressor that attenuates the voltage peaks at a ratio of infinity:1. So there won't be any peaks above your threshold. As you raise the volume the "body" of the signal below the threshold rises normally just like a compressor does. Brents graph shows that - +V and -V is the maximum voltage allowed to pass through the limiter and the area under the curve (area I shaded blue) is the power that is passed. Notice there is more area of blue (power) on the right "peak limited" signal when overdriven hard. The dotted line in red is what the limiter cutoff.
Image

An "RMS limiter" is different than a peak limiter as it monitors the signal and reduces the gain if the average power of the signal exceeds the threshold you set. They do leave the signal as is although at a reduced level. They are useful to maintain a signal below your speakers RMS thermal rating however they still let the peaks through and when they kick in they alter your top to sub ratio. They are also usually fairly slow to kick in ~5 to 10 seconds before they work their magic. Ideally you would want both a peak limiter and an RMS limiter engaged to fully protect you. You don't really find RMS limiters on DSP's until you get to a dbx venue 360 or fancier unit.

Even if you set both types of limiters you are not fully protected. The RMS thermal ratings of your driver were tested in a climate controlled room run "free air". Running EDM (sine waves) through your wooden (insulator) subs for 72 hours straight in the desert heat can still fry them from the heat build up in the cabinet. The seasoned OEM veterans in the EDM festival world only run their cabinets at 1/4 their rated capacity to make it through long festivals in the blistering heat. Of course they bring lots of cabinets to make up for that.
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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Seth
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Re: Lab 12 recone kits

#17 Post by Seth »

Interesting. Thanks for the explanation CO. I didn't know there was such a thing as an RMS Limiter and must have mixed the two up somewhere along the line. Now I'm wanting to see the waveform of a limited signal on an oscilloscope. Why would they not just have it work the same as a compressor w/o makeup gain, and leave the waveform intact ? Makes no sense to me why they'd just clip the signal instead of attenuating it. This day and age, DSP? I'm astonished.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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BrentEvans
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Re: Lab 12 recone kits

#18 Post by BrentEvans »

SethRocksYou wrote: Mon Oct 01, 2018 10:54 pm
BrentEvans wrote: Mon Oct 01, 2018 9:34 pm When these idiots start redlining gear (which includes playing hard into the limiter so it's always limiting), they start driving the power curve up so you end up getting more power per volt.
I thought limiters left the signal intact. Like compression, attenuates signal peaks. No?
Normally not. Compression doesn’t necessarily leave the signal intact either. Most of the time you’re using a relatively short attack and release time when using compressors on channels, otherwise it sounds like it’s “pumping,” and you get unexpected volume changes. Limiters by necessity have a 0 attack time (or virtually zer0 in some cases) so a damaging signal can be cut off, and they usually have 0 release times as well. Dbx has an “over easy” feature on driveracks which adds a little bit of light compression before the limit point to make it sound less clipped (similar to the way many people run an outboard compressor on their main bus set to lightly kick in a few dB before the syst4m farts out) and give you a few more dB of signal headroom, but the actual limit point is still a 0 attack point.
99% of the time, things that aren't already being done aren't being done because they don't work. The other 1% is split evenly between fools and geniuses.

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BrentEvans
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Re: Lab 12 recone kits

#19 Post by BrentEvans »

SethRocksYou wrote: Tue Oct 02, 2018 10:56 am Interesting. Thanks for the explanation CO. I didn't know there was such a thing as an RMS Limiter and must have mixed the two up somewhere along the line. Now I'm wanting to see the waveform of a limited signal on an oscilloscope. Why would they not just have it work the same as a compressor w/o makeup gain, and leave the waveform intact ? Makes no sense to me why they'd just clip the signal instead of attenuating it. This day and age, DSP? I'm astonished.
Leaving the signal intact would sound like limiting by riding your master fader. That’s not what you want, because it’s a noticeable change in gain structure. With the clip method, tickling the limiters is completely unnoticeable, which is what you want it to be. Hard into limit is going to sound like crap either way.
99% of the time, things that aren't already being done aren't being done because they don't work. The other 1% is split evenly between fools and geniuses.

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Seth
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Re: Lab 12 recone kits

#20 Post by Seth »

If that's the way it is, I'll just have to rearrange my reality to match. I find I have to do that a lot around here. Thanks for the explanation Brent.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

ACUA
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Re: Lab 12 recone kits

#21 Post by ACUA »

:noob: Amen!
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CoronaOperator
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Re: Lab 12 recone kits

#22 Post by CoronaOperator »

Presents came today. I measured the Re of the coils and they are ~4.5 ohms so they match the specs of the 6 ohm originals even though they are labeled Lab12ARK. They are factory eminence replacements as well from q-components in Canada.

Image

If you look at the picture, they came with 2 different sizes of dust covers. The bigger ones seem to be the Lab12 factory ones, I wonder why they put in the little ones? There is 3 of each so you could go either way. I have DATS speaker driver measurement system so maybe when I recone them I'll measure the T/S parameters of both with them just tacked on. The weight will be different but I wonder if the structural flexing of the cone would be different? I'll use the factory size to be consistent, but I'll test just for curiosity.

I've done plenty of recones with preassembled kits. This will be my first time doing it from scratch.
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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Bill Fitzmaurice
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Re: Lab 12 recone kits

#23 Post by Bill Fitzmaurice »

The smaller dust covers would raise Fs, lower Qes and more.

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