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Author Topic: Lab Sub handling  (Read 18039 times)

Benjamin Goulart

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Lab Sub handling
« on: November 12, 2013, 06:27:21 pm »

What kind of power (in volts, please) can each lab sub handle with, say...

no HPF?

HPF set at 25hz 48dB/oct butterworth?

HPF set at 27hz 48dB/oct butterworth?

HPF set at 30hz?

HPF set at 35hz?

What HPF setting would be required for it to handle 3000 watt peaks, or is 2000 watts the limit regardless of roll-off?  Not sure if the 2000 watt figure I've seen thrown around is continuous, program, or peak, but I assume it was meant at the default 35hz LR 24db/oct HPF.

Is thermal handling a bigger problem than over-excursion, and would new Class D designs with their PWM supplies be less likely to cause thermal issues with the drivers since they have a tendency to crap-out (or tapper off, to use a euphemism) on extended sin-wave-like signals?

Conservative estimates based on simulation and/or experience, accounting for manufacturing variance is cool.  I don't want to necessarily assume the drivers in mine are the best examples Eminence ever produced, though they've apparently run without a problem for 20 years so far.

Thanks for your time.
« Last Edit: November 12, 2013, 07:03:58 pm by Benjamin Goulart »
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Ivan Beaver

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Re: Lab Sub handling
« Reply #1 on: November 12, 2013, 08:34:16 pm »



Conservative estimates based on simulation and/or experience, accounting for manufacturing variance is cool.  I don't want to necessarily assume the drivers in mine are the best examples Eminence ever produced, though they've apparently run without a problem for 20 years so far.

Thanks for your time.
The drivers are rated at 400 watts each.  I doubt you have had them for 20yrs-since the lab 12 has not been made that long-unless you are using a different model number

How much power they can "handle" depends a lot on what the source material is-freq wise-dynamic range wise and so forth.

If you are doing "dance" type material-with long sustained low freq tones-the power "handling" will be less than with a dynamic type source that has short notes.

There are no "exact" ratings-only ratings based on a particular set of test tones or application.

The nice thing about standards is that there are so many to choose from.
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Ivan Beaver
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Benjamin Goulart

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Re: Lab Sub handling
« Reply #2 on: November 13, 2013, 12:14:59 am »

The drivers are rated at 400 watts each.  I doubt you have had them for 20yrs-since the lab 12 has not been made that long-unless you are using a different model number

How much power they can "handle" depends a lot on what the source material is-freq wise-dynamic range wise and so forth.

If you are doing "dance" type material-with long sustained low freq tones-the power "handling" will be less than with a dynamic type source that has short notes.

There are no "exact" ratings-only ratings based on a particular set of test tones or application.

The nice thing about standards is that there are so many to choose from.

Don't know why I said 20 years.  I think it said 2003 or 4 inside.  Hah.  Sorry.  Not sure which image of the date I was thinking of in my head when I typed that in.

Do you know of anyone with an already-defined model (and some tutorial info) on the labhorn for hornresp so I could at least see what the simulation suggests the excursion will be at the various settings?  I assume that is not taking into account thermal issues.  I'm not sure where to even begin with the sim values.  I saw one listing of values someone used, but several of them appeared blank from the hornresp version I tired.

Anyone done a simple open air excursion test with a 10hz sin wave to see at what point these drivers reach xmax?
« Last Edit: November 13, 2013, 11:18:02 am by Benjamin Goulart »
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Art Welter

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Re: Lab Sub handling
« Reply #3 on: November 13, 2013, 11:45:04 am »

What kind of power (in volts, please) can each lab sub handle with, say...
no HPF?
HPF set at 25hz 48dB/oct butterworth?
HPF set at 27hz 48dB/oct butterworth?
HPF set at 30hz?
HPF set at 35hz?

What HPF setting would be required for it to handle 3000 watt peaks, or is 2000 watts the limit regardless of roll-off? 

Is thermal handling a bigger problem than over-excursion, and would new Class D designs with their PWM supplies be less likely to cause thermal issues with the drivers since they have a tendency to crap-out (or tapper off, to use a euphemism) on extended sin-wave-like signals?
As Ivan said, "it depends".

If the compression chamber is well sealed (no air leaks) the usual failure mode is thermal, the Lab 12s driver can only handle 200 watts sine wave continuous.

The horn cut off is around 35 Hz, a 24 or 48 BW at 30 Hz will protect the driver from excursion below without affecting the LF much at all.
The highest excursion for most program music will be around 60 Hz, the HP filter won't offer any protection there. However, the impedance is pretty high at 60 Hz, so less power is dissipated in that region.
The way to cook the drivers is hit it hard at 40 Hz, where the cone hardly moves at all and the impedance is about the same as the DCR, about 2.2 ohms for the two drivers in parallel.
The Lab 12 are not very good at loosing heat to start with, and in the small compression chamber the surrounding air does not offer much cooling

An amp's current limiting will make a big difference in that regard, there are some Crown amps that put out less power at 2 ohms than at 4, for instance.

The Hornresp simulations below are from:
http://audioroundtable.com/PiSpeakers/messages/17389.html

Hornresp has gone through many updates since then, it now has a filter simulation as well.
That said, below Fc or Fb, Hornresp is not all that accurate predicting excursion, the Lab 12 suspension limits excursion past Xmax more than the simulation would indicate.

I have used Lab 12s in bass reflex, band pass, front loaded and tapped horns cabinets, they can take 49 volts sine wave (at any frequency) for short duration tests.
They start to smell after about 10 seconds at that level even in open air, vent hole out in a tapped horn.
2000 watt peaks are not a problem, but with a dynamic range of 12 dB (the crest factor for normal pink noise), the drivers will get hot enough that the impedance rises in just a few minutes, and level will drop by 2-3 dB.
If the level is raised another 3 dB to compensate for the thermal compression, smoke may ensue.
Heavy limiting could reduce the dynamic range to a point where 1000 watt "peaks" could be too much average power for a pair of Lab 12.

Art
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Benjamin Goulart

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Re: Lab Sub handling
« Reply #4 on: November 14, 2013, 11:28:26 am »

50-60 Volts appears to be the maximum safe thermal limit of the Labhorn sub if there are no restrictions on the type of signals, sweeps, or tests.

Is there a frequency at xmax v. volts graph anywhere for it?

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Ivan Beaver

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Re: Lab Sub handling
« Reply #5 on: November 14, 2013, 11:40:32 am »

50-60 Volts appears to be the maximum safe thermal limit of the Labhorn sub if there are no restrictions on the type of signals, sweeps, or tests.

Is there a frequency at xmax v. volts graph anywhere for it?
That would have to be a 3D graph-as the excursion will vary with freq
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Benjamin Goulart

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Re: Lab Sub handling
« Reply #6 on: November 14, 2013, 12:55:39 pm »

That would have to be a 3D graph-as the excursion will vary with freq

I'm thinking excursion being 1 at frequency, so it'd be frequency @ reaching xmax versus voltage in 2D.  In 3D, only the 1 region would interest me, anyway.
« Last Edit: November 14, 2013, 12:58:12 pm by Benjamin Goulart »
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Art Welter

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Re: Lab Sub handling
« Reply #7 on: November 15, 2013, 10:15:20 am »

50-60 Volts appears to be the maximum safe thermal limit of the Labhorn sub if there are no restrictions on the type of signals, sweeps, or tests.

Is there a frequency at xmax v. volts graph anywhere for it?
60 volts works out to around 1600 watts at the low impedance frequencies of the LabHorn.
From a thermal standpoint the drivers can only withstand 60 volts for peaks, the long term average should not exceed 30 volts.

Doubling voltage is a six dB increase in power, and doubling of excursion.
Using the 45 volt excursion plot in post #3 you can extrapolate what the excursion would be at any given frequency if you increased voltage.
The Lab 12 has 13mm Xmax, around 49V will hit Xmax in the 60 Hz range.
Hornresp also has a function to show thermal and excursion limited levels on the same screen, though I find that to be pretty useless, since I know exceeding Xmax sounds bad, and power level simulations don't have any time constants- there is a huge difference in average power between a punchy kick drum and a droning sine wave like synth bass line.
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Benjamin Goulart

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Re: Lab Sub handling
« Reply #8 on: November 15, 2013, 10:19:29 pm »

What voltage would xmax be at 30hz?

20hz?

10hz?

I don't think the class d amps with pwm power supplies can provide full power at lower frequencies for more than a few seconds at a time into very low impedances without voltage being time-limited and dropping to a fraction of that rated power with test signals or some dub step synth tone.  I would bet it's probably impossible to destroy these labhorns with the amp I bought since it's like that and has dsp & all sorts of limiting regardless.  I'll usually further limit it at 25-50 volts depending on how I have the HPF set, but even leaving it at the default 82 volts would probably be safe. 

60 volts works out to around 1600 watts at the low impedance frequencies of the LabHorn.
From a thermal standpoint the drivers can only withstand 60 volts for peaks, the long term average should not exceed 30 volts.

Doubling voltage is a six dB increase in power, and doubling of excursion.
Using the 45 volt excursion plot in post #3 you can extrapolate what the excursion would be at any given frequency if you increased voltage.
The Lab 12 has 13mm Xmax, around 49V will hit Xmax in the 60 Hz range.
Hornresp also has a function to show thermal and excursion limited levels on the same screen, though I find that to be pretty useless, since I know exceeding Xmax sounds bad, and power level simulations don't have any time constants- there is a huge difference in average power between a punchy kick drum and a droning sine wave like synth bass line.
« Last Edit: November 15, 2013, 10:24:33 pm by Benjamin Goulart »
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Ivan Beaver

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Re: Lab Sub handling
« Reply #9 on: November 16, 2013, 08:21:07 am »



I don't think the class d amps with pwm power supplies can provide full power at lower frequencies for more than a few seconds at a time into very low impedances without voltage being time-limited and dropping to a fraction of that rated power with test signals or some dub step synth tone.
Most class D amps would LOVE to be able to produce sine waves for a couple of seconds.  If you look at the specs-you will see full power for "typically" 0.08 seconds  (80ms) before dropping down.

Yes it makes a HUGE difference when doing dance type stuff.  Not as big a deal with "kick drum rock and roll".

There are a few out there that can do it a good bit longer-but that is one spec that the manufacturers don't like to talk about.
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