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Amplifier Comparison SpeakerPower SP2-12000 and Powersoft K20-DSP-Aesop

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For the record, if it were an A14K (which it wouldn't have been), everyone would know the reason why in short order. There would be no mystery.

 

Josh, seriously, I'm up for raiding Brandon's place before it's -30 degrees up there in the Swiss Alps.

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For the record, if it were an A14K (which it wouldn't have been), everyone would know the reason why in short order. There would be no mystery.

 

Josh, seriously, I'm up for raiding Brandon's place before it's -30 degrees up there in the Swiss Alps.

 

I just posted the SpecLab captures of the music track I used for testing in my theater thread.  Go  take a look. 

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That looks like some weird music.  Nothing else in the bass range except low fundamental clean sines.  Unusual.  What is the artist/track? 

 

Send your wife on an errand and give me the voltage reading. 

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For the record, if it were an A14K (which it wouldn't have been), everyone would know the reason why in short order. There would be no mystery.

 

Josh, seriously, I'm up for raiding Brandon's place before it's -30 degrees up there in the Swiss Alps.

 

I wasn't joking but that's up to him really. I could make it happen if we got a schedule worked out.

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8,000 watts into 1 ohm requires 90 amps of current. So, you might see why someone reading your name-dropping, spec-citing posts might ask for actual measurements, or might be curious about your 220V/30A circuit and SP 1-6000 driving the iPAL/DIY Horn?
 

Your math is correct, but you are plugging in the wrong numbers.  Yes, the amp will be supplying 90 amps to your sub to produce 8000W with 1 ohm.  However, it needn't pull 90 amps *from the wall* in order to do so!  Simply put, power output = power input * efficiency.  So a 90% efficient amp will need to draw 8900W (with rounding) from the wall to supply 8000W continuously.  If the mains service is 240V, then that will pull about 33 A.  That's far cry from the 90 A you stated.  Furthermore, the amp capacitance provides an energy reservoir that allows it to temporarily output more power than it takes from the mains line.

 

This is a big deal because you keep talking about low impedance loads like they require some herculean number of amps out of the wall to provide their rated power output at the low impedance they are rated for.  This is not true.  8000W is 8000W as far as the mains supply is concerned.  What matters is if the amp is up to the task of supply it for the load that's present.  The higher the impedance, the more volts the amp needs to be able to provide to supply that power.  The more interesting question is if the amp will misbehave or burn itself up when presented such a low impedance where it can easily be asked for way more power than it is designed to provide.

 

It remains a mystery what happened with the SP2-8000 and the HS-24.  Everyone was shocked by the outcome, although no one is denying it happened.

 

I can't believe I personally wasted so much time researching this issue.  Too bad there is, as you say, almost no data to clarify what caused it to happen.  That is what we call an anecdote, and a single anecdote does not amount to much evidence at all.  There's nothing wrong with reporting that it happened, but it's obnoxious to see this one anecdote used as a stick to beat the reputation of the SP2 repeatedly.

 

And of course, if someone can produce substantial evidence that the SP2 chokes so easily, then we will have more to talk about.

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And of course, if someone can produce substantial evidence that the SP2 chokes so easily, then we will have more to talk about.

 

I'm sure of two things. 

 

1. we can count on you lording over the discussion when that happens, Subject Matter Ego.

 

2. you won't be the one who contributes the data.

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For the record, if it were an A14K (which it wouldn't have been), everyone would know the reason why in short order. There would be no mystery.

 

Josh, seriously, I'm up for raiding Brandon's place before it's -30 degrees up there in the Swiss Alps.

 

Typically a 10 degree differential due to the elevation change from your place to mine. You missed the last one I hosted where there was a fresh 5 inches of snow on the deck. And that was the first week of November. And then it went back to 60 degree weather and didn't snow again for two months. Very unpredictable. I'm down to host something anytime really. I have been eyeing a weekend in November. Anyone have interest in that?

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That looks like some weird music.  Nothing else in the bass range except low fundamental clean sines.  Unusual.  What is the artist/track? 

 

Send your wife on an errand and give me the voltage reading. 

 

It's a track by Bass Launch called "Earth".  This one particularly is the "low and slow" version.  Most of the tracks on that whole album are similar to this.  I'm not sure if there would be any difference between playing my 6 second loop of this track or a 27.5hz sine wave from REW.

 

For the voltage, do you want me to capture the voltage at the binding posts while playing that track loop at a level where the amp begins to clip?  The Fluke 117 is called a "True-RMS" meter, so I'm not sure if simply getting the AC voltage is all you're after. 

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 I'm down to host something anytime really. I have been eyeing a weekend in November. Anyone have interest in that?

 

Open to it and ready to head your way, bro. It's always a pleasure and I've been wanting to meet Josh for years. LMK the date and I'm there. B)

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If everything about low frequency reproduction could be assumed, this forum would obviously not exist.

 

The question is why would anyone design a subwoofer system to operate at 1 ohm nominal. I see no advantages, only disadvantages. How much transient burst current a breaker can allow before tripping is not predictable and not relevant.

Power is I^2 * R.  Delivering that power with high Voltage or high current is just a matter of design choices.  If you want more power than you get from rail Voltages easily created from a 120V line, low impedance capability works out pretty well as you just need to add current capability rather than design a new power supply.  Into an 8 Ohm load or 2 Ohm load, power is power.

 

 

The SP-2-8000 muted when operating on a dedicated 120V-30A line at Brandon's GTG, both channels driving a 1.7 resting Re reactive load. Since Paul and I weren't there to test a SP amplifier (didn't even know one was there until Dave Gage pulled it out of his car and brought it in half way through the GTG), there was little more time and equipment available to do more than measure resting Re and speclab cap the scenes being played.

 

I know this; the A14-K amp bridged, driving the series-wired VCs at a resting Re of 3.4 ohms with the same 120V-30A line would have been easily able to damage the HST-24 driver without going into protect.

 

There was speculation by Seaton after the fact that it was "line sag", but there was no indication that line sag or brown out was apparent during the rest of the GTG. Still, no measurements were taken. I still don't know if there is overcurrent protection in the SP line of amps or how one would know what is going on with the amplifier since there are no indicator LEDs on the front panel besides a power on LED and the rear panel only has single signal LED and a clip and a protect LED. Protect can mean several things.

 

I'd have to look it up, but Brian has posted the VLF frequency response more than a few times, and even pushed the corner a little lower not too long after introducing the Torpedo series.

 

While there is just 1 "PROT" protection indicator LED, when ever the amp goes into an error state, it does signal the fault with a short-long flash code.  I believe David's amp had firmware with only 6 different indications, where the current version has 17 combinations and indications.

 

While most brushed past and focused on 1 of my 2 suggestions for the fault/cut-out, I also suggested this could have been the result of an overly sensitive DC protection circuit.  I know David's amp had a looser setting than the first release as I was responsible for the first adjustment, but it has been pushed to a lower/longer time constant over time, and I've been talking with Brian about eliminating it entirely as the other diagnostics in the amp would detect the issue upstream in the circuit, making it a belt & suspenders situation.  I suspect the brief cut-out Josh noted was also a DC protection circuit, but can't be certain without Brian bypassing the circuit and letting Josh run that sweep again. 

 

 

Couple of things.

 

1.) The SP-12K I have on loan does have front panel clip, signal and protect indicators. Putting them on the back was completely nonsensical to me. Glad that change was made. 

 

2.) I could not get the SP-12K or the K20 to protect with any content above 20Hz in any of the particular scenarios I used. Protect was much more likely below 10Hz with lower impedances. IOW higher current demands. A lower impedance load may be different as may a smaller 120v line, but it is clear that the sub bass stuff is a much greater drain on the amps either way. YMMV

 

3.) I've read a lot about that SI-24 / SP-8K deal and I don't know what happened there. Not enough info. Perhaps the content used really wasn't as demanding on the driver as what is thought or maybe Mark is right and there was severe line sag on the 120v line. I'm confident that the 12K I have would not be able to be let loose on the 24 in the exact box used at that GTG with the GP DB type testing or the 24 driver would need re-coned.

 

4.) I'm going to take the SP-12K and use it to GP test a sealed IPAL-21 which is a much rougher load than when loaded in a horn with a HPF. It will be on 240v. We'll see how that goes. I'll capture the applied voltage and already have the impedance measurement for that enclosure+driver so we will be able to do a rough calculation of the current and power.

 

 

It remains a mystery what happened with the SP2-8000 and the HS-24.  Everyone was shocked by the outcome, although no one is denying it happened.

 

I admit I was a bit cranky when asked for all the additional information about my 1ohm claims, but I’ve learned a lot in the last week so I’m glad I dug into it deeper.  I found out my favorite dubstep demo track wasn’t anywhere near 1ohm but rather even over 2ohm in fact once measured. 

 

I also confirmed (at least to myself) that on the very next track I picked with 27hz content that a consistent ~1.2ohm load is being presented to the amp many  times throughout that track.  I’ll provide a SpecLab capture of the track and also of my several second loop of the track which I used for the voltage/amperage capture. 

 

Me merely providing a DCR of a driver and a track name wasn’t enough info for you, and I get why after the last week of impedance measurements I performed. 

 

However, this is exactly the limited information you’ve provided about the SP2-8k/HS-24 debacle.  We have a DCR of the driver, and a track name from “imagic” on AVS.  I imagine if someone stated something like “We bridged an A14K to a single driver with a DCR of 2.9ohm and got it to mute the outputs on “tracknamehere” you’d understandably want more information such as the exact things I’ve been asked for in this thread:  Speclab captures of the track, voltage and amperage draw from the amp, and a RMS voltage from the amp while at the limits.  Maybe even a voltage reading from the mains to see if there was voltage drop? 

 

That information was never gathered and can’t be provided from this GTG a few years ago, so it’s going to remain a mystery.  If it were the A14K in that scenario with the same limited information, you wouldn’t be happy it was brought up every time a A14K is mentioned because we simply don’t have enough information to know what caused it.

 

Exactly.  No one checked what was indicated on the rear to see what the fault was.  The Torpedo amps will generally deliver their rated power into a ~1.5 Ohm load.  At lower impedances the amplifier will operate just fine, but will clip due to current limiting at lower Voltages, but will very rarely cause a shutdown.  The amplifier monitors its temperature and will usually throttle back maximum power until the temperature comes back to a safe operating range.  If by some chance a signal and environmental condition kept it from cooling, the amp would eventually shut down before reaching dangerous temperatures.  To keep this in perspective, that temperature of throttling back is well past the point where the fan on the rack mount amplifier switches to high speed, and is very hard to reach with typical subwoofer loads.  Most often this really only comes into play in pro applications where the black rack and amplifiers are out in the sun, packed tight in a rack with another heat source above and below the amp.  Even so it's nice to know the amp will almost never shut down from heat, but rather just throttle back.  If it does go into this state, the red protect LED indicates this behavior with 3 long flashes followed by 3 short flashes while still running.  Thermal shutdown until temperature falls is indicated by 3 long flashes and a pause with no sound until the temp falls.

 

As an example of the low impedance tolerance/stability, the in-house burn-in step at Speaker Power uses a near short circuit heating element mounted to its own heatsink in order to get the amplifiers to heat up in a realistic time frame.  This tests thermal stability and protection.  That sort of burn in and robust protection is part of what makes for the premium cost of the amplifier vs. the cheaper amps produced in China.

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I also suggested this could have been the result of an overly sensitive DC protection circuit.  I know David's amp had a looser setting than the first release as I was responsible for the first adjustment, but it has been pushed to a lower/longer time constant over time, and I've been talking with Brian about eliminating it entirely as the other diagnostics in the amp would detect the issue upstream in the circuit, making it a belt & suspenders situation.  I suspect the brief cut-out Josh noted was also a DC protection circuit, but can't be certain without Brian bypassing the circuit and letting Josh run that sweep again.

 

I think it is more likely a current protection circuit because when Josh tested at a higher impedance there was no muting with the same burst/long term tones.

 

 

So a GTG at Beast's?  Woo hoo!  Is Dgage mailing that amp so we can get to the bottom of it finally? 

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It's a track by Bass Launch called "Earth".  This one particularly is the "low and slow" version.  Most of the tracks on that whole album are similar to this.  I'm not sure if there would be any difference between playing my 6 second loop of this track or a 27.5hz sine wave from REW.

 

For the voltage, do you want me to capture the voltage at the binding posts while playing that track loop at a level where the amp begins to clip?  The Fluke 117 is called a "True-RMS" meter, so I'm not sure if simply getting the AC voltage is all you're after. 

Stick to the song track since you already know it's impedance for sure measured with your meter.  Your meter doesn't do peak so just the steady RMS reading is fine with it set to AC auto range. 

 

Last I heard Gage was going to send that amp to notnyt to test whenever he gets the free time but for all I know you might be right. 

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Stick to the song track since you already know it's impedance for sure measured with your meter.  Your meter doesn't do peak so just the steady RMS reading is fine with it set to AC auto range. 

 

Last I heard Gage was going to send that amp to notnyt to test whenever he gets the free time but for all I know you might be right. 

 

Looks he had it for sale but no mention if it actually sold:

 

http://www.avsforum.com/forum/209-audio-gear/1970642-fs-speakerpower-sp2-8000-rack-mount-sub-amp.html

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I think it is more likely a current protection circuit because when Josh tested at a higher impedance there was no muting with the same burst/long term tones.

 

 

So a GTG at Beast's?  Woo hoo!  Is Dgage mailing that amp so we can get to the bottom of it finally? 

 

The DC detection circuit on the outputs is basically a low pass filter that detects a threshold.  It ends up being current/power related so if VLF was tripping it, it would be level dependent.  While not the same circuit, the Dayton SA-1000 rack mount amplifier has the same issue but happens very easily when driving a nominal 4 Ohm load.  Many incorrectly attributed this to some sort of input clipping, including Mr. Chase who never knew why the ones he sold would occasionally go into protection when driving dual woofers.  Changing the time constant and sensitivity of this circuit was part of the many modifications Sandbagger was doing to the SA-1000 amplifier shipped with the MFW-15 Turbo kits.

 

The detail I can't remember is if the amp shutdown at beast's place required cycling the power or if it bounced back on its own?  To the best of my knowledge there isn't any current protection that would cause a cut out, but a few power line conditions could including a GFI condition or over/under Voltage.  With the severe clipping this level occurred at, it's possible there was some internal condition the monitoring circuits were over-sensitive to as well.  We should also remember the levels the amp cut out at was akin to complaining about how a driver behaves well past linear Xmax.  It's much preferred if any protection doesn't cause a shut down that requires a power cycling, but not suffering any damage is just as important.

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  That sort of burn in and robust protection is part of what makes for the premium cost of the amplifier vs. the cheaper amps produced in China.

 

 

This is the sort of post that prompts a reaction from me. :)

 

Where are the parts for this robust protection circuit sourced from, what makes an over-current circuit any more robust or more expensive, what cheaper amps produced in China are you referring to and what makes their protection circuitry my less robust?

 

In the context of the discussion, specifically regarding over-current protection, making such a circuit more "robust" simply means raising the peak current value of the circuit before it trips. Nothing superior about it. Nothing so much more costly about it.

 

Is it a good thing?

 

The output impedance of the A-14K is approximately 0.020 ohms. Say I have 15 feet of 10AWG wire from the amp terminals to the Raptor terminals. That raises the output impedance to 0.35 ohms. Into a nominal 7.4 ohms (Raptor System II), the damping factor is approximately 220. Into a nominal 0.70 ohms, the damping factor drops to 21 and the signal loss increases by at least 5%

 

Is that sort of difference in damping factor audible? Is there a quicker rise in THD with the lower impedance load? Does the spike in heat affect the longevity of an amplifier whose cooling scheme may not be considered optimum for higher heat? Is there a change in efficiency as load impedance drops? These are the more pertinent points to address rather than how some protection circuit results in a price that exceeds any amplifier made in China (which translates to virtually every other amp), IMO.

 

I'm happy to know that somewhere on the net the FR of the SP amps is posted. Maybe you'll actually follow up and post it here.  We have a thread for that if you're so inclined to add the data there. I fail to see where it is a negative thing in any way to provide the info. B)

 

To address the insanely insulting post that any mention of the GTG experience is SP-bashing; the amplifier used at the GTG belonged to a SP OEM manufacturer (or soon-to-be at the time if he wasn't already). No one else there knew much of anything about the amp, especially not a flashing prot light on the back panel. Apparently, David chose not to pursue the cause for personal reasons. So, if anything, I guess it was on you to follow up since you were the only person with tech comments after the situation was mentioned and are also a SP dealer and end-user.

 

I've been interested in the SP amps since their launch in their current iterations. The situation at the GTG is being referred to in this thread as one that supposedly should not have occurred or sent shock waves throughout the interwebs. Well, hopefully we have enough on the ball to know that that is nonsense. No one designs protection circuitry for a situation that will never occur, right? We all thought what happened at the GTG was noteworthy. If I were considering purchasing any $3,000.00 amplifier, it's certainly information I would like to be made aware of.

 

I think a lot of Brian and have followed his SP career for much longer than probably anyone here and I believe the SP line, as it has evolved to the present time, is an outstanding achievement. I'm just put off by the cheesy comparisons to alternative choices or their countries of origin to justify the price.

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This is the sort of post that prompts a reaction from me. :)

 

Where are the parts for this robust protection circuit sourced from, what makes an over-current circuit any more robust or more expensive, what cheaper amps produced in China are you referring to and what makes their protection circuitry my less robust?

 

In the context of the discussion, specifically regarding over-current protection, making such a circuit more "robust" simply means raising the peak current value of the circuit before it trips. Nothing superior about it. Nothing so much more costly about it.

 

Is it a good thing?

 

I think you put a lot of added intent behind what I wrote than was actually there.  The term "robust" was meant in terms of design, not physically superior parts.  There are more than a few amplifiers which we've seen give up the ghost driving lower impedances or have odd behavior as they are used near their maximum capabilities.  The burn-in process on every amplifier is also something few China factories perform unless stipulated by a buyer with enough of an established relationship for them to actually listen.

 

The "housekeeping circuitry" is handled by a custom programmed micro-controller.  There is different programming for each power model, rack vs. plate, and even some differences between those sold to the home vs. heavy duty pro use like those doing EDM shows.  

 

The upside is the protection makes major/catastrophic failures very rare.  Any needed repairs are usually relatively low cost vs. the cost of the amplifier, of course there's no charged cost to the customer within the warranty period.  Any misbehavior results in a shut down and usually protects the rest of the circuitry and components.  I consider that a robust, fault-resistant design.  I've dealt with more than a few amplifiers which would blow up if the amp is set to 115V and plugged into a 230V line, or would die or blow a hard to get to fuse if speaker wires were shorted somewhere.

 

The downside of the internal monitoring is that it can have a false trigger caused by an unexpected condition.  Since the early Torpedo amplifiers shipped in 2010, there has been continued polishing of the housekeeping circuits and Brian has been very receptive to making adjustments for different applications any time the issue was repeatable or otherwise identifiable.  

 

 

The output impedance of the A-14K is approximately 0.020 ohms. Say I have 15 feet of 10AWG wire from the amp terminals to the Raptor terminals. That raises the output impedance to 0.35 ohms. Into a nominal 7.4 ohms (Raptor System II), the damping factor is approximately 220. Into a nominal 0.70 ohms, the damping factor drops to 21 and the signal loss increases by at least 5%

 

Is that sort of difference in damping factor audible? Is there a quicker rise in THD with the lower impedance load? Does the spike in heat affect the longevity of an amplifier whose cooling scheme may not be considered optimum for higher heat? Is there a change in efficiency as load impedance drops? These are the more pertinent points to address rather than how some protection circuit results in a price that exceeds any amplifier made in China (which translates to virtually every other amp), IMO.

 
Wire loss is the down side of lower impedance loading.  I use 4x11 wire for my high power runs, which keeps loss in the wire to around 0.25dB even over a 50' run with a 2 Ohm load at the end.  Of course if that's 2 4 ohm loads you always have the option to make 2 runs making that loss 1/2 as much.  Very common and even less expensive 4x12 wire meets the same loss at a relative 35' vs 50'.  If the amp is internal to the box or very close, the wire loss is a non-issue.
 
We would have to ask Brian about the balance of "how low is too low?"  Brian's products are compared against many pro audio amplifiers which all are rated into 2 Ohms as many want to drive 2-4 cabinets off one amplifier channel.  It's meeting a market demand more than an ideal design.  If we're aware of the limitations, it's a highly useful gain of power output above the 4 Ohm rating. 
 
 

To address the insanely insulting post that any mention of the GTG experience is SP-bashing; the amplifier used at the GTG belonged to a SP OEM manufacturer (or soon-to-be at the time if he wasn't already). No one else there knew much of anything about the amp, especially not a flashing prot light on the back panel. Apparently, David chose not to pursue the cause for personal reasons. So, if anything, I guess it was on you to follow up since you were the only person with tech comments after the situation was mentioned and are also a SP dealer and end-user.

 

I've been interested in the SP amps since their launch in their current iterations. The situation at the GTG is being referred to in this thread as one that supposedly should not have occurred or sent shock waves throughout the interwebs. Well, hopefully we have enough on the ball to know that that is nonsense. No one designs protection circuitry for a situation that will never occur, right? We all thought what happened at the GTG was noteworthy. If I were considering purchasing any $3,000.00 amplifier, it's certainly information I would like to be made aware of.

 

I think a lot of Brian and have followed his SP career for much longer than probably anyone here and I believe the SP line, as it has evolved to the present time, is an outstanding achievement. I'm just put off by the cheesy comparisons to alternative choices or their countries of origin to justify the price.

 

At the time of the GTG in question, David was a user & enthusiast and not yet planning to take the plunge into being a manufacturer.  If David was able to reproduce the situation at home he likely would have pursued it, but from what I saw posted, there was no more info than "It cut out while we were cranking it."  The load presented by the 24" with the 2 Ohm nominal coil per channel was a moderate load, especially in such a large box.  Who knows what happened.  If someone else happens to repeat such an issue, we can figure out what was happening as it's a rather rare occurrence vs. the amplifiers out in the field.

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I'm sure of two things. 

 

1. we can count on you lording over the discussion when that happens, Subject Matter Ego.

 

2. you won't be the one who contributes the data.

 

Your response is disappointing, and you mistake my critical peer review for excessive ego.  You could have tried to explain why my reasoning was wrong or instead admitted that you made a mistake in your calculation.  Instead you ridiculed me.  Engineering is hard, and mistakes are made frequently, even by experts.  Such mistakes can cost a lot of time and money to correct unless they are caught early.  Therefore experienced engineers appreciate and welcome critical peer review that identifies mistakes they made.

 

This isn't the only time that I've brought errors to Dave's attention and received insulting responses instead of any kind of acknowledgement that he got it wrong.   As I said, I expect mistakes to be made by all of us from time to time, but I also expect people with integrity to correct those mistakes when they are realized.  Furthermore, you and Dave's ability to support the product you sell (the A-14k) depends on your knowledge of the product and knowledge of the physical principles upon which it functions.  If you cannot distinguish between current flow in the speaker wire and current flow in the mains circuit, how can you possibly understand how the amp works?  And again, I'm not harping on the particular mistake that was made.  We all goof up like this once in a while, but if this were merely a brain fart, then I surely would have seen a response like "oops, I mixed those things up when I did the calculation".  Instead, you/Dave respond like I hurt your feelings or something.  Either you're just screwing around with me, or you guys really don't have any understanding of what you are talking about and are simultaneously unaware of this fact!

 

So maybe the $3000 price tag of the SP2 reflects the fact that it's actually engineered by the company that sells it.  Whether that fact justifies the higher price tag over the A-14k is for everyone else to decide for themselves.

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Stick to the song track since you already know it's impedance for sure measured with your meter.  Your meter doesn't do peak so just the steady RMS reading is fine with it set to AC auto range. 

 

Last I heard Gage was going to send that amp to notnyt to test whenever he gets the free time but for all I know you might be right. 

 

You owe me one shreds...I did this with the wife home because I was so curious...  :D

 

I measured a steady 86.5v without clipping and registered 131.1db with one Othorn at the LP (compromise with the wife was that only one horn would be on =)  ).  

Going up one more DB in the volume resulted in 88.0v, 132.0db, and clip lights.  

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I could do the weekend of November 6th or the 20th for a potential GTG. Not sure if that works with anyone else. Obviously Halloween and Turkey day weekend are out. I have a prior commitment the 14th weekend.

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I could do the weekend of November 6th or the 20th for a potential GTG. Not sure if that works with anyone else. Obviously Halloween and Turkey day weekend are out. I have a prior commitment the 14th weekend.

 

I talked to the wife and the only way I'd be able to make it is if the GTG was on 11/20.  It just so happens my in-laws in SC are driving up here on 11/21 so I'd be able to catch a cheap flight down on Friday and ride back up with them on Sunday.  

 

Don't let that get in the way of the 6th if that's better for everyone/anyone else!

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If someone else happens to repeat such an issue, we can figure out what was happening as it's a rather rare occurrence vs. the amplifiers out in the field.

 

Again, besides the vague comparisons, this is the other point of my posts regarding stupid-heavy loads presented to an amplifier, generally speaking. The scenario is not likely to be repeated because it's not an optimum system configuration. Yes, pro sound is the market for the rackmount amps and no, they never have to reproduce single digit source at max output into <2 ohms from a bridged amp. Why would anyone recommend a system that presents <2 ohms per bridged amp?

 

So, maybe you can tell me what I'm missing in the differences between a high voltage, high impedance system vs a high current, low impedance system? Our tests say <3 ohms per bridged amp results in audibly degraded reproduction. Maybe our tests are seriously flawed.

 

EDIT: I just caught Luke's post. Congrats, Luke! Great exercise and results. I'm sure Paul will follow up looking for the rest of the details like what mains, distances, one channel driven, etc., but thanks for the great effort. B)

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Your response is disappointing, and you mistake my critical peer review for excessive ego.  You could have tried to explain why my reasoning was wrong or instead admitted that you made a mistake in your calculation.  Instead you ridiculed me.  Engineering is hard, and mistakes are made frequently, even by experts.  Such mistakes can cost a lot of time and money to correct unless they are caught early.  Therefore experienced engineers appreciate and welcome critical peer review that identifies mistakes they made.

 

This isn't the only time that I've brought errors to Dave's attention and received insulting responses instead of any kind of acknowledgement that he got it wrong.   As I said, I expect mistakes to be made by all of us from time to time, but I also expect people with integrity to correct those mistakes when they are realized.  Furthermore, you and Dave's ability to support the product you sell (the A-14k) depends on your knowledge of the product and knowledge of the physical principles upon which it functions.  If you cannot distinguish between current flow in the speaker wire and current flow in the mains circuit, how can you possibly understand how the amp works?  And again, I'm not harping on the particular mistake that was made.  We all goof up like this once in a while, but if this were merely a brain fart, then I surely would have seen a response like "oops, I mixed those things up when I did the calculation".  Instead, you/Dave respond like I hurt your feelings or something.  Either you're just screwing around with me, or you guys really don't have any understanding of what you are talking about and are simultaneously unaware of this fact!

 

So maybe the $3000 price tag of the SP2 reflects the fact that it's actually engineered by the company that sells it.  Whether that fact justifies the higher price tag over the A-14k is for everyone else to decide for themselves.

 

Your argument is stupid.

 

Try to misread that as critical peer review. :rolleyes:

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You owe me one shreds...I did this with the wife home because I was so curious...  :D

 

I measured a steady 86.5v without clipping and registered 131.1db with one Othorn at the LP (compromise with the wife was that only one horn would be on =)  ).  

Going up one more DB in the volume resulted in 88.0v, 132.0db, and clip lights.  

Hahaha, awesome.  A couple questions: you have a 240V 30A line?  Is that two 15A 120V breakers?  I think I asked you that at the GTG but I forget.  Do you remember how long the wire run was and what gauge you used for the power line?  And were you running 1 channel only for the song part because the amp doesn't bridge right? 

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Hahaha, awesome.  A couple questions: you have a 240V 30A line?  Is that two 15A 120V breakers?  I think I asked you that at the GTG but I forget.  Do you remember how long the wire run was and what gauge you used for the power line?  And were you running 1 channel only for the song part because the amp doesn't bridge right? 

 

It's two 120v 30A breakers, one on each of the 120v mains coming into the house.  The voltage measures just over 122v on each.

 

The mains are 10g wire and about 35ft long.  

 

And yes, this was 1 channel of the amp since it can't be bridged.  

 

The power cable for the amp is also 10g with the L6-30P twist lock plug and the larger 32A PowerCon:

 

20141003_142644_zpskyv1jltv.jpg

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