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[David Haulman]

Met Tom Danley; Ivan Beaver and got a t shirt. Great InfoComm. Thanks !!!!!!!

[Ivan Beaver]

Met Tom Danley; Ivan Beaver and got a t shirt. Great InfoComm. Thanks !!!!!!!

The coolest thing I got was a 1 foot measuring stick-with a built in SPL meter. The "stick" is the circuit board.

One of the things I saw that shows a lot of promise is from Eminance.  It is a "passive" loudspeaker protection circuit (that is computer programmable) that goes between the amp and the loudspeaker.  No external power needed.

It provides such things as "RMS" limiting-peak (freq dependant) limiting-overexcursion and others.

It is not available yet (hopefully in a few months)-but I saw some demos that were pretty amazing.  Such as a Lab Gruppen 6400 mono bridged with pink noise applied and driven to full clip-into a  4" loudspeaker-among other tests.

I will be getting one for testing soon.

[John Roberts {JR}]

The coolest thing I got was a 1 foot measuring stick-with a built in SPL meter. The "stick" is the circuit board.

Shouldn't it be 1 meter long? 

One of the things I saw that shows a lot of promise is from Eminance.  It is a "passive" loudspeaker protection circuit (that is computer programmable) that goes between the amp and the loudspeaker.  No external power needed.

It provides such things as "RMS" limiting-peak (freq dependant) limiting-overexcursion and others.

It is not available yet (hopefully in a few months)-but I saw some demos that were pretty amazing.  Such as a Lab Gruppen 6400 mono bridged with pink noise applied and driven to full clip-into a  4" loudspeaker-among other tests.

I will be getting one for testing soon.

"Passive" in electronics means simple (not-active) components like resistors, capacitors, inductors, etc.

From looking at press, and patents and stuff, that unit looks like it is very "active" and probably stealing power from the audio waveform to run it's internal processor. This shouldn't be a problem with modern low impedance solid state amps, and as long as the transients it needs to protect against don't come immediately following a very long silent stretch  (even that could be managed with a battery or big ass capacitor).

The speaker protection is apparently provided by a high current MOSFET switch in series with the speaker load to disconnect the amp from the speaker when the voltage is too high. By chopping the signal on and off at a very fast rate, well above audio, the speaker see's the average voltage as determined by the on-time vs. off-time duty cycle. A little like a light dimmer works (very little). A 50% on/off chopper duty cycle would effectively deliver 1/2 the amplifier output voltage to the speaker, and 1/4 the power.

Since this is just intermittently disconnecting the speaker from the amp, there is no power wasted or heat generated so both are reasonably happy when limiting. The speaker just behaves like it is getting less drive voltage, the amp acts like it is driving a higher load resistance

 I wouldn't even read too much into any warts that may show up in early testing, since this looks like it is can be programmed to do whatever you want, within it's general constraints.  One always important question is what will the per unit cost be. That will depend a bunch on manufacturing volume, plus a royalty on top of the actual manufacturing cost.

veddy interesting...

JR
   
   

[Craig Leerman]

From looking at press, and patents and stuff, that unit looks like it is very "active" and probably stealing power from the audio waveform to run it's internal processor. This shouldn't be a problem with modern low impedance solid state amps, and as long as the transients it needs to protect against don't come immediately following a very long silent stretch  (even that could be managed with a battery or big ass capacitor).

The speaker protection is apparently provided by a high current MOSFET switch in series with the speaker load to disconnect the amp from the speaker when the voltage is too high. By chopping the signal on and off at a very fast rate, well above audio, the speaker see's the average voltage as determined by the on-time vs. off-time duty cycle. A little like a light dimmer works (very little). A 50% on/off chopper duty cycle would effectively deliver 1/2 the amplifier output voltage to the speaker, and 1/4 the power.

Since this is just intermittently disconnecting the speaker from the amp, there is no power wasted or heat generated so both are reasonably happy when limiting. The speaker just behaves like it is getting less drive voltage, the amp acts like it is driving a higher load resistance

 I wouldn't even read too much into any warts that may show up in early testing, since this looks like it is can be programmed to do whatever you want, within it's general constraints.  One always important question is what will the per unit cost be. That will depend a bunch on manufacturing volume, plus a royalty on top of the actual manufacturing cost.

veddy interesting...

JR

I spoke with the designer at length last month, and did an article about the D-Fend unit in this month's Live Sound International mag.

It does draw its power from the amplifier's output. The unit has three independent filters that can be set to specific freq ranges, and independently adjusted for threshold, etc.  When the output of the amplifier is within the rated parameters set for the speaker, the unit is not in the circuit. When the amplifier's output exceeds any of the set parameters, the unit kicks in very quickly (within a few microseconds) and you are correct in that it basically fools the amplifier into thinking there is a higher impedance load attached. No power is soaked up and there is very little heat generated.  The unit can be mounted inside a box and  used to protect individual drivers in a system, or set up to protect an entire box.

The technology was developed by a division of the SLS speaker company (the guys with the cool ribbon driver cabinets) and Eminence is the licensed distributor for the MI and pro audio markets. SLS will include the device in their products, and Eminence has told me that in addition to licensing the technology to other manufacturers as an OEM unit, they will soon have some products of their own that include the unit. They also stated that they will have some stand alone type units that could be retrofitted into existing speaker cabinets, and the price of a completed circuit board with USB connector (for programming with a computer) would probably  be UNDER $100!

I see a lot of applications for the unit. For installed systems, its a good insurance policy, not to mention it would prevent having to go up on a ladder or lift and fix a blown driver, which is very hard to do in many cases after the install is complete.  For folks who rent stuff over the counter, it would all but eliminate blow speaker cabinets (I say all but, because I'm sure there will be one idiot who will still manage to blow up the rental gear even with a D Fend unit in place.  ("Hey Bob, check out my new CamLock to Speakon adapter") 

In the MI world, I can see a lot of uses for the technology in bass rigs, guitar amps, and keyboard rigs. And for the average production house, its a cheap price to pay for the peace of mind that your gear will be working day in and day out, with less down time for repairs, and less money spent on replacement drivers and diaphragms.

VEDDY interesting indeed!

[John Roberts {JR}]

I spoke with the designer at length last month, and did an article about the D-Fend unit in this month's Live Sound International mag.

It does draw its power from the amplifier's output.

Thanks for the confirmation... easy guess on my part.

The unit has three independent filters that can be set to specific freq ranges, and independently adjusted for threshold, etc.  When the output of the amplifier is within the rated parameters set for the speaker, the unit is not in the circuit. When the amplifier's output exceeds any of the set parameters, the unit kicks in very quickly (within a few microseconds)

As series protection, it seems it is "always" in the circuit with the mosfet switches turned hard on. The mosfets are turned off (chopped) to provide protection. 

 and you are correct in that it basically fools the amplifier into thinking there is a higher impedance load attached. No power is soaked up and there is very little heat generated.  The unit can be mounted inside a box and  used to protect individual drivers in a system, or set up to protect an entire box.

I specifically avoided the word "fooled" (I don't much care for that characterization). The amplifier puts out a voltage source that is unchanged. It is not fooled, but the load is only presented to the amp output for a fraction of the time, so it only draws current for that "on" fraction of the time. Fooling the amplifier suggests it does something different. It continues to put out a low impedance voltage source. The chopped load draws less current and makes less power in the load.

This is clearly superior to lossy series protection schemes, and a novel application of a mature technology (PWM).

The technology was developed by a division of the SLS speaker company (the guys with the cool ribbon driver cabinets) and Eminence is the licensed distributor for the MI and pro audio markets. SLS will include the device in their products, and Eminence has told me that in addition to licensing the technology to other manufacturers as an OEM unit, they will soon have some products of their own that include the unit. They also stated that they will have some stand alone type units that could be retrofitted into existing speaker cabinets, and the price of a completed circuit board with USB connector (for programming with a computer) would probably  be UNDER $100!

I looked into the merchantability of a stand alone speaker protection box and one dynamic that discouraged me was the need for the end user to set precise thresholds for robust protection of individual drivers and situations without forfeiting performance. Of course if the end user sets the thresholds you have some wiggle room to avoid liability if drivers still blow up, but too many failures and the product is tarnished, too little output and the product will likewise be unloved.

For those reasons I see this as potentially more attractive to manufacturers not typical end users (of course there may be a few exceptions reading here). Even with the USB interface, the end user still needs to know what to set the protection thresholds to. 

I see a lot of applications for the unit. For installed systems, its a good insurance policy, not to mention it would prevent having to go up on a ladder or lift and fix a blown driver, which is very hard to do in many cases after the install is complete.

In reliability engineering, added protection circuitry is always a double edged sword. More protection is good, but added complexity is always something else that can fail. As a series switch, you can't just put a fuse in series with the active circuitry to open up and fail harmlessly. A bypass relay could mitigate against failure but that would need to be normally closed and held open to effect protection, yet something else to fail. (FWIW, solid state power devices often fail as a short circuit, so this may already fail as turned fully on or bypassed. I don't know and won't speculate further).

For folks who rent stuff over the counter, it would all but eliminate blow speaker cabinets (I say all but, because I'm sure there will be one idiot who will still manage to blow up the rental gear even with a D Fend unit in place.  ("Hey Bob, check out my new CamLock to Speakon adapter") 

Yes, clearly a target application... making unpowered speakers that can't be blown up, even when mixed and matched with different power amps. Properly dialed in this should be very helpful.

In the MI world, I can see a lot of uses for the technology in bass rigs, guitar amps, and keyboard rigs. And for the average production house, its a cheap price to pay for the peace of mind that your gear will be working day in and day out, with less down time for repairs, and less money spent on replacement drivers and diaphragms.

VEDDY interesting indeed!

One thing that is worth thinking about in the context of this product is that it's strength is that it is independent of the rest of the active system, so can be installed inside an unpowered speaker cabinet and still protect the driver(s). This is most useful for that one application.

Active powered products have access to the power amp input so can modulate the level going to the speaker without having to deal with the more difficult high current output side of the power amp.  I won't speculate, but I am curious to see the linearity of this protection device's on resistance. I don't see any mention of this, only a comment that this exhibits "lamp like" musicality. I'm not sure what that means.

=======
I realize I may sound overly critical (sorry it's my nature). I don't want to detract from the inventor's accomplishment. This is a clever way to protect a driver, when you don't have access to to the amp inputs.

The success of this will hinge on cost, execution, and perceived value.  This promises to allow non-powered cabinets to be as smart as powered cabinets, while I don't see the attraction of avoiding powered cabinets (perhaps a personal problem).

I look forward to read Ivan's hands-on impressions.

JR

[Ivan Beaver]

Shouldn't it be 1 meter long? 
"Passive" in electronics means simple (not-active) components like resistors, capacitors, inductors, etc.

   
 

Agreed a 1M would be "better-except that it would be a bit hard to bring home for most people (and that is a big circuit board)-and almost nobody actually measures at 1M-but I like your thought process.

By passive I meant that it did not require an external power supply.  Yes it does derive its power from the incoming signal.

I only had a short demo at the very end of the last day.  We did not actually listen to any music (and it would be hard in a show floor environment to actually evaluate the quality), but the signals on the scope were pretty impressive-for the limited inputs we looked at.

The real test will be playing with it in a product in a controlled environment.

The cost for manufacturers is very attractive and would be worth it in all but the cheapest products.

I am really hoping that it will do what it says it will.

I do agree that it is probably NOT for the typical person who simply "thinks" they can throw it in and their loudspeaker will be protected.  That person will typically not have enough intamate knolwedge of the particular loudspeaker he is using to properly set the parameters.

However for a manufacturer-who has the facilities to measure and properly set it up-it could be a "cheap insurance policy"-assuming there is no signal quality loss.

I will let you know what I find.

My hope is that since SLS is involved (and this is not some Chinese unknown product), there has already been enough testing so that it does not adversly affect sound quality.

[Iain.Macdonald]

.......

Nice idea. Just wondering, if it was driven to almost constant operation in a DJ like scenario, would it cause instability in the power amp.

Iain.

[John Roberts {JR}]

.......

Nice idea. Just wondering, if it was driven to almost constant operation in a DJ like scenario, would it cause instability in the power amp.

Iain.

Power amps that are stable with no load, should be stable with some fraction of the load, so I wouldn't expect issues, at least with pro SR amps.

I can imagine some obscure applications that might have issues. For example imagine a powered speaker using a poorly filtered class D amp inside. They may be counting on the speaker to filter the PWM waveform into continuous audio. If the protection chopper rate and class D PWM rate occur at frequencies within 20k of each other, there could be audible beats (birdies), but this seems pretty unlikely, since with a powered cabinet the protection could just pull back the amp at it's input, and there should be some filtering around all switched devices. 

Low level HF noise by itself, is not audible, but won't always remain silent in the presence of other low level HF noise. If there was some low level hash generated in the noise floor, this would only be present during limiting, so likely to be masked by the loud enough to require limiting, signal.

JR

[Iain.Macdonald]

Nice idea. Just wondering, if it was driven to almost constant operation in a DJ like scenario, would it cause instability in the power amp.

Iain.


Power amps that are stable with no load, should be stable with some fraction of the load, so I wouldn't expect issues, at least with pro SR amps.

I can imagine some obscure applications that might have issues. For example imagine a powered speaker using a poorly filtered class D amp inside. They may be counting on the speaker to filter the PWM waveform into continuous audio. If the protection chopper rate and class D PWM rate occur at frequencies within 20k of each other, there could be audible beats (birdies), but this seems pretty unlikely, since with a powered cabinet the protection could just pull back the amp at it's input, and there should be some filtering around all switched devices. 

Low level HF noise by itself, is not audible, but won't always remain silent in the presence of other low level HF noise. If there was some low level hash generated in the noise floor, this would only be present during limiting, so likely to be masked by the loud enough to require limiting, signal.

JR

Yes. Thanks for that. There could possibly be a problem with a few amps that have load sensing/impedance monitoring/auto adjust. Though Ivan saw it working with a Lab G, but who knows how it was set up. I also look forward to his tests. I can see this product being attractive to those producing MI type products.

Re your earlier post:

“Simplicity is the ultimate sophistication.” - Leonardo da Vinci

Iain.

[John Roberts {JR}]

I am not sure that any load sensing amp would be smart enough to be confused by this. If it senses for load impedance at low output (by sensing current vs voltage) it will get the correct cold impedance number and be fine. If it detects just peak current it will get different results depending on state of the protection and/or speaker. FWIW a normal speaker without a chopper in series will still exhibit different impedance cold vs. hot. I expect the amp will just react to whatever it experiences at any given moment.

This is mostly speculation on my part, about the only way I can imagine internal amp protection being wrong is delivering redundant protection, but who knows? We'll learn more after some units get into the field. 

JR

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