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Author Topic: LAB sub driver monitoring  (Read 4048 times)

Craig Hauber

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LAB sub driver monitoring
« on: February 28, 2008, 01:51:13 pm »

Has there been any talk of monitoring cone movement and VC temperature using sensors of some kind?  It would be cool to have an ethernet on the back of the boxes with continuous data output of these 2 parameters.  I was thinking of accelerometer-type sensor mounted on the back of the cone (they are tiny now)

Even cooler if there was a black-box you could plug them into that you also pass the final amp-drive audio through and it could act as the ultimate safety limiter.

The buried-woofer and horn style of boxes have always been a concern of mine.  By the time you hear overdriving or distortion it's too late, and the heat issue is a big deal too.

Just now starting to play with my first labsub and am curious about these things.  At least with direct radiating you can see what's going on, not to mention hearing the distortion long before damage is being done.  And the ports allow some degree of heat escape (not to mention the chamber the drivers sit in is huge compared to the LAB's)

My main sub of use is still the L-Acoustics dual-18 (Not for any real reason other than it matches the Vdosc properly and I can get lots of them)

Thanks
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Craig Hauber
CSA Productions Inc.
Ventura-Santa Barbara CA
www.csaproductionsinc.com

John Roberts {JR}

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Re: LAB sub driver monitoring
« Reply #1 on: February 28, 2008, 02:28:34 pm »

Craig Hauber wrote on Thu, 28 February 2008 12:51

Has there been any talk of monitoring cone movement and VC temperature using sensors of some kind?  It would be cool to have an ethernet on the back of the boxes with continuous data output of these 2 parameters.  I was thinking of accelerometer-type sensor mounted on the back of the cone (they are tiny now)

Even cooler if there was a black-box you could plug them into that you also pass the final amp-drive audio through and it could act as the ultimate safety limiter.

The buried-woofer and horn style of boxes have always been a concern of mine.  By the time you hear overdriving or distortion it's too late, and the heat issue is a big deal too.

Just now starting to play with my first labsub and am curious about these things.  At least with direct radiating you can see what's going on, not to mention hearing the distortion long before damage is being done.  And the ports allow some degree of heat escape (not to mention the chamber the drivers sit in is huge compared to the LAB's)

My main sub of use is still the L-Acoustics dual-18 (Not for any real reason other than it matches the Vdosc properly and I can get lots of them)

Thanks


Shhh....   I already have a rough design kicking around in my head...

It would be inappropriate for me to share what I've worked up on the WWW. There are several issues to manage to make this commercially viable for the mass market (low cost, easy to use, etc).

FWIW some of this can already be done with big dog installation amps, that have the right hooks, and using computer control. You're not going to find these at your local GC. Some high end powered cabinets may do some or all of this internally.  

Temperature sensing could be embedded into VC but adding dead mass and more leads to that assembly doesn't seem very desirable, direct excursion sensing while possible doesn't seem very practical either. I guess non contact radiated Infra red detection could be used but that is not inexpensive and probably doesn't have a clean shot at the VC. Simply measuring the temp of air in the box or speaker frame, could be better than nothing.

JR


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Iain_Macdonald

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Re: LAB sub driver monitoring
« Reply #2 on: February 28, 2008, 05:54:58 pm »

Craig Hauber wrote on Thu, 28 February 2008 18:51

Has there been any talk of monitoring cone movement and VC temperature using sensors of some kind?  It would be cool to have an ethernet on the back of the boxes with continuous data output of these 2 parameters.  I was thinking of accelerometer-type sensor mounted on the back of the cone (they are tiny now)

Even cooler if there was a black-box you could plug them into that you also pass the final amp-drive audio through and it could act as the ultimate safety limiter.

The buried-woofer and horn style of boxes have always been a concern of mine.  By the time you hear overdriving or distortion it's too late, and the heat issue is a big deal too.

Just now starting to play with my first labsub and am curious about these things.  At least with direct radiating you can see what's going on, not to mention hearing the distortion long before damage is being done.  And the ports allow some degree of heat escape (not to mention the chamber the drivers sit in is huge compared to the LAB's)

My main sub of use is still the L-Acoustics dual-18 (Not for any real reason other than it matches the Vdosc properly and I can get lots of them)

Thanks


Hi,

Old news I am afraid.

d&b already have a Patent on your concept. JBL also have applicable IP. RMS and Peak modelling in the analogue domain was a feature of a number of products. Meyer, RH, Nexo and EV et al had controllers with a sense line from the amp output and analogue modelling of drive. It's easy to work out a impedance, current, voltage, excursion matrix. There have been a number of loudspeaker controllers you could buy to use with any amp/speaker combo, but these didn't prove popular and I think they have gone from the market. Most loudspeakers are likely to be self powered in the future and these will all feature what you want. JR mentioned that some install amps already have this reporting feature. This is required over here in Europe for announcement/evac systems in public spaces.

Iain.
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John Roberts {JR}

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Re: LAB sub driver monitoring
« Reply #3 on: February 28, 2008, 07:46:28 pm »

Iain Macdonald wrote on Thu, 28 February 2008 16:54


Hi,

Old news I am afraid.

d&b already have a Patent on your concept. JBL also have applicable IP. RMS and Peak modelling in the analogue domain was a feature of a number of products. Meyer, RH, Nexo and EV et al had controllers with a sense line from the amp output and analogue modelling of drive. It's easy to work out a impedance, current, voltage, excursion matrix. There have been a number of loudspeaker controllers you could buy to use with any amp/speaker combo, but these didn't prove popular and I think they have gone from the market. Most loudspeakers are likely to be self powered in the future and these will all feature what you want. JR mentioned that some install amps already have this reporting feature. This is required over here in Europe for announcement/evac systems in public spaces.

Iain.


Indeed... This will all be moot in the future I often rant about when all speakers are powered with DSP inside... they will be smart enough to protect themselves.

Main problem between now and then to come up with a merchantable product is how to set these things up for specific speakers. Done right the amps really don't matter.

FWIW, most of fixed install line monitoring is more to confirm the VCs are still connected, and functional.

JR

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lawrencemueller

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Re: LAB sub driver monitoring
« Reply #4 on: February 29, 2008, 11:19:55 am »

In regards to temperature, I was thinking of a lo-fi monitoring device - a $20 oven thermometer with sensor. I was thinking I could modify one of these to give me a constant temperature reading of one of the drivers. I have no idea what the temperature rangeis , but I am interested because I'm machining my own version of the cooling plugs used in the Pi horns.
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Craig Hauber

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Re: LAB sub driver monitoring
« Reply #5 on: February 29, 2008, 01:37:15 pm »

I just need something to tell me when I'm at the end.  

Honestly I won't get to use the subs at full-power enough times to learn the audio characteristics of "I'm just about to blow"  Until probably long after I've blown a few (that's really not good for the show)  Also what's good at the beginning of the show might not work so well at the end when ears get fatigued, the audience gets louder and temperatures go up.

If there was a panel of led indicators that light-up with an over-temp warning or flashed at a certain amount of excursion I would be happy.

I remember a velodyne large home stereo subwoofer back in the 80's that had a tiny accelerometer mounted on the cone.
Or how about something as simple as a laser bouncing off a tiny mirror glued to the back of the cone -or even shoot it across the face to a senser that when the cone moves too far forward the surround interrupts the beam?
The signal line could go high (with adequate hysteresis built-in) and be used to trigger  one of the external control inputs on a modern DSP (Audia, Soundweb, Netmax etc...) for something like a .5 dB ramp-down every time it occurs until it stops occurring.

I'm not looking for a polished manufacture-able product, I'm a hobbyist looking at this in a DIY way for FUN and education.  
(I install plenty of name-brand PA gear, the hobby is just one way of learning what goes on behind the grille of that gear as well as understanding it's design - or simply being able to see past the sales-speak to the reality of it)


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Craig Hauber
CSA Productions Inc.
Ventura-Santa Barbara CA
www.csaproductionsinc.com

Iain_Macdonald

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Re: LAB sub driver monitoring
« Reply #6 on: March 02, 2008, 02:53:22 pm »

Hi,

Real world - My view is that it's great to monitor what is going on, but useless if it tells you that it just blew up. The most important consideration, is to make sure that you always operate with the safe operating area. A glance back at the hundreds of postings on this topic. Clearly shows that the Lab Sub/Lab 12 driver combo, works well if it is within the SOA. People who have built the speaker and used it for years will confirm this. The next issue is making sure people don't overdrive it. A properly set up limiter with look ahead is the first answer. Next I would be looking at using an amp like the Powersoft K series or similar, which has user control of the output voltage.(see manual for description)

Homebrew funworld - First over-excursion. Whatever you can think of, somebody has already patented it or published a paper describing it. Laser sensing, magnetic positioning, optical encoding, extra voice coil with feedback, pressure sensing with a microphone(look at Meyer X10 Studio monitor, not what it's for but mounting idea), piezo sensor and more. Second, over-temp. Lawrence mentioned a cheap temp sensing kit and these are available from electronic hobbyist vendors. About $15 in the UK. You could put the probe in the air vent. But you need to be able to relate the pole temp to the voice coil temp. There is going to be a time lag between the two evening out. A number of people have tried putting IR sensors in holes drilled through the pole piece/magnet. That seems like a good idea. If you are going to be renting out the boxes, I would also suggest putting some temp indicating tape on the backplate of the driver. I am sure you use it in your installation business.

Iain.
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John Roberts {JR}

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Re: LAB sub driver monitoring
« Reply #7 on: March 02, 2008, 03:56:31 pm »

Craig Hauber wrote on Fri, 29 February 2008 12:37

I just need something to tell me when I'm at the end.  

Honestly I won't get to use the subs at full-power enough times to learn the audio characteristics of "I'm just about to blow"  Until probably long after I've blown a few (that's really not good for the show)  Also what's good at the beginning of the show might not work so well at the end when ears get fatigued, the audience gets louder and temperatures go up.

If there was a panel of led indicators that light-up with an over-temp warning or flashed at a certain amount of excursion I would be happy.

I remember a velodyne large home stereo subwoofer back in the 80's that had a tiny accelerometer mounted on the cone.
Or how about something as simple as a laser bouncing off a tiny mirror glued to the back of the cone -or even shoot it across the face to a senser that when the cone moves too far forward the surround interrupts the beam?
The signal line could go high (with adequate hysteresis built-in) and be used to trigger  one of the external control inputs on a modern DSP (Audia, Soundweb, Netmax etc...) for something like a .5 dB ramp-down every time it occurs until it stops occurring.

I'm not looking for a polished manufacture-able product, I'm a hobbyist looking at this in a DIY way for FUN and education.  
(I install plenty of name-brand PA gear, the hobby is just one way of learning what goes on behind the grille of that gear as well as understanding it's design - or simply being able to see past the sales-speak to the reality of it)





While this is silly simple, perhaps coating the VC cap with a temperature sensitive chemical that changes color with temperature might give you a mood ring display of VC temp rise...

JR
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Iain_Macdonald

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Re: LAB sub driver monitoring
« Reply #8 on: March 02, 2008, 06:45:06 pm »

Craig,

The link below shows the temperature labels I mentioned. They are really useful to record over temperature events in equipment. I used to put them inside equipment racks, and inside amps etc. You can soon tell if a customer hasn't cleaned filters or they've interfered with the rack cooling. Consoles were another candidate. The reversible types used externally, are useful on the air vent side of amps, on console surfaces etc., especially if you do open air events in the summer.

http://tinyurl.com/2w7yo5

Iain.
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