Ricci

Nah not selling all that. Just reached a point where I realized Id like to get some space back.

Still 2 18" XXX's left. Somebody grab these! Right now my garage is a train wreck with multiple projects going on and crap everywhere. I was looking around in it yesterday and realized I REALLY need to liquidate more stuff. This is what is currently sitting in my garage. 6 XXX 18's 7 TD15M Apollo's 2 BMS 18n862 1 LMS 5400 1 Alpine SWR-1522 4 21Ipal 1 Aura NS18 A couple other random drivers That is just what is mine. There's also 1 SI 24 2 SI HST-18's 2 other 21's to be tested for a Mfg 1 Other 18 to be tested for a Mfg There are drivers, subs and boxes everywhere.

Werd...

Just added up the driver specs for a few new drivers I have on hand. Aura NS18 Alpine SWR-1522D SI HST-18d2 rev 2

Bass-less. Hardly!

Looks like there are only 2 XXX's left if anyone is on the fence...

Looks similar to the Armonia GUI. I assume you are measuring the rms voltage during your tests Luke. Note that the voltages shown in the GUI and LG literature will be peak numbers. 98 volts peak would equate to roughly 69.4 volts rms.

It's a long shot but it there any chance that the signal being sent into it or the inputs are clipping?

I agree with SME this has nothing to do with bus pumping. It is already a fully bridged design. Also bus pumping can damage the amplifier in short order so fast acting protection circuits would normally be used to recognize the issue and stabilize the amplifier. Typically this would involve muting the outputs completely among other things. This sounds like the amp is hitting a long term limitation in the power supply, an internal limiter, or severe clipping. Are you sure it does not have some type of current or voltage limiter engaged in the dsp or somewhere else? It may just be that it has a low rail voltage and once the caps are drained it just doesn't have much voltage to work with.

I think I know what I'm going to do next but I have a feeling it's going to take quite a while to sell these if they sell at all. I need to do that prior to moving forward. Who knows my current plan may change by that time.

It's time for a change Scott. Now seems like a good time. I barely ever use the HT and I figure it's going to take a long time to sell these.

RE Audio XXX 18d2 Drivers (8 Available) All are dual 2 ohm voice coils. All work just fine. 6 are the older split coil version. 2 of them are the newer REV 2 version with an overhung coil. $550 shipped each. To the lower 48 only. $500 each local pickup greatly preferred. Louisville, KY area. I will drive to meet some one half way. Possible price break and willingness to travel further if someone wants multiple drivers.

The average resistance will go up with more heat in the coil but whether the magnitude at any one frequency goes up or down is not as simple. Once the coil really heats ups or the driver is under a lot of pressure or excursion demands are high the impedance can shift dramatically. You can see this in the power compression tests for a number of systems.

Can't tell much if anything about power compression with this data. The tests being at 2 frequencies nearly 1/3rd octave apart can easily account for 2.5dB itself. Not to mention one has a much lower impedance than the other. Not really apples / apples at all. Luke even as strong as those drivers are Id be careful with doing this type of stuff. You may cook one. Use as many drivers as possible so they don't get heated as much.

Guys I don't care about cussing or a bit of heated arguing but keep it from getting too ugly.

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

I'll just drive down and bring it back with me.

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.

Thanks Brian. I always try to be unbiased and fair. It is not easy sometimes I will admit. Anyway I think both amplifiers performed extremely well. Each has particular strengths and features. The fact that the 12K fans do not run most of the time is a huge plus for home theater installs. I'm thinking about building a hush box or remote locating my K20's now. Their fan noise is less than most amps I've used but compared to silence it's no contest. I can see why the SP plate amps have become so popular. It is such a big step up in power from the other choices available. The typical "1000w" plate amps are toys in comparison.

We may not know the measured current and voltage limits for either amp over certain frequency ranges but I don't know of that type of data from other amps to compare to anyway.All of those tests cut off at 20Hz if they even go that low. I can get that data from the K20. It tracks the output voltage and current, the impedance of the load, average power, temperature in the amp, rail voltage, AC line voltage, blah, blah. Likewise it also shows when limiting occurs whether current or voltage and clipping in real time. The SP-12K doesn't have all of that so you would need a test rig to gather the data and of course we don't know whether the clip lights occur well before or well after actual clipping but I'd say it is fairly accurate at indicating that the amp is out of "more" since the output would plateau. No idea what the distortion is at that point. We do know how these amps compare to each other at least in a limited sense. The K20 puts out more clean signal. It should based on the specs and that is what all of the tests showed. (As long as it is bridged for the sub 20Hz range of course.) The SP-12K might possibly put out more into very low impedance loads with sustained signals, which is also what the results showed. It seems to be allowed to pass a bit more current for longer. The K series is limited to 32A long term and claims like 125A peak short term ( I believe the indefinite limit is capped at around 4Kw). Both could probably pass more for a longer time but there has to be a limit to avoid tripping breakers which is a bad day all around at the gig. There's a limit to how much heat can be dissipated as well even with 90% or better efficiency. After bridging the K20 it did not protect during any of the tests. Perhaps bridging it into a lower impedance like 2ohms mono would cause it. I'll probably end up trying it. The SP-12K did mute with <10Hz if slammed into clipping. I don't mean approaching clipping I mean get to the point the clip lights are flashing and then give the volume knob another spin. Other than that it was fine with everything else too. Would be interesting to see the behavior at 1ohm minimums.

Yep yep. Agreed on your points Mark. That's why I posted the impedance curve. I would disagree a bit. Not with anything in general only that while the DCR is indeed a bit high-ish, I'd contend this is normal use driving speakers. Impedance fluctuates greatly with frequency and current is only high near the minimums. Unfiltered sealed systems are about the worst case. They only have one impedance peak and the amplifier is asked to produce high current into the impedance minimums in the lowest frequencies. Typical use for higher order systems means generally higher impedances, more impedance peaks and a low end that is filtered away in order to protect the drivers. Sure I could get some drivers with the DCR a bit lower down near 2.8-3 ohms for a 4ohm load but they will also typically have much higher motor force than the boat anchors used so the impedance peak will be much more severe and cover a broader plateau raising the average impedance over a large area of the bandwidth. I'd expect more current only required in the very deepest bass and perhaps at a narrow band above the resonance. I know you probably have at some point, but I doubt many others will have looked at actual average power applied to the speakers using even what is considered "intensive" content, over a significant amount of time like 30 minutes or an hour. Even 400w average applied power to a subwoofer over more than a few minutes is a lot for the reasons discussed above. There are huge peaks in the content but the duration and overall average power is actually much lower than most people would assume. I almost went with the SP amps. I didn't because of the whole GP testing thing and also because when the Euro went into the trash for a while I got a smoking deal on the K's. I needed the most amp I could get on one set of terminals and the SP can only use one side so that kind of clenched it. Kind of wish I did for the HT just because either amp has all the power needed but the SP fans are silent. Anyway this wasn't really meant to be a tediously detailed comparison but something different and fun. I still need to do some testing on the Ipal 21's so I may just go ahead and take both amps outside and let them both have a shot into 1 ohm and 2ohm minimums. I definitely want to use the 12K on the single 21 because that truly dips to 1ohm in spots and I don't think bridging the K20 into that will result in its best performance.

Sort of. There are a few innocent bystanders that came of walls or vibrated off and fell. Lost a few light bulbs. Some rattles I don't think can ever be fully taken care of. It's just too much energy for that.

Oscilloscopes and current/ voltage captures are cool but how do these behave when strapped to a bunch of speakers? That was the point of this to begin with. Let's get away from the test bench captures while driving resistors in a water tank and use a real world load with all of the complexity and possible nastiness of multiple, heavy coil, high inductance drivers driven really hard. FR traces at a volt are useful but no guarantee of maintaining their shape when the amp is asked for full output or when loaded with complex reactive loads. Now a FR at the onset of clipping with a very slow and taxing measurement would be nice, but no one provides those. I wanted to dispense with paper ratings of things like watts and see the bottom line of how each amp handled driving a set of subs when the throttle was mashed to the floor. I don't even care about how clean the amp is or at what point it gets dirty with this type of setup. With a finished system design you either have enough gear to stay out of clipping and keep it clean or not IMO. That kind of thing was not within the scope of this type of setup. No doubt about it the sub 20Hz range is way more demanding on the amps and once things get down to 10Hz and below it is even worse. The duty cycle is much higher simply because the waveforms are so long in duration and the impedance is the lowest so current is both high and demanded for longer amounts of time. I don't know how many people are really familiar with REW's signals, but a maximum length sweep set to a bandwidth of 2-120Hz or similar is vicious when dumped unfiltered from soundcard to amp to speaker. The 2-20Hz band takes what is probably the first 7 seconds or so and when the amp is being driven with an input signal that is a couple of dB beyond what would light the clip lights it is a rough test. Nothing in any movie soundtrack I've ever seen yet has the duration and sustained draw from the amp to compare. It's not as bad as just leaving a 5Hz sine wave on at clipping indefinitely, but it is worse than anything I've seen in music or movie content. The fact that both the amps produce as much juice as they did and are protected against blowing themselves up even when pushed to their limit with this type of <10Hz stuff was exactly what I want to see. I truly would worry about blowing some amplifiers if driven in this way. Try it at your own risk. Also the CEA-2010 style bursts...I'd like to note for those reading along that they are 6.5 cycles so at 50Hz it is equivalent to 0.13 seconds. Not long at all, but comparable to a kick drum thump overall. However down at 20Hz it is 0.33 seconds duration and at 10Hz it is now 0.65 seconds. Not real long but it might as well be an eternity compared to some of the 1 cycle 1kHz signals used to produce the power ratings for many amplifiers so it is more demanding than the signals used by many manufacturers for their ratings. I would like for amplifier manufacturers to adopt a standard to provide burst ratings using these standardized signals at something like 10Hz, 31.5Hz, 100Hz, 1kHz and 16kHz.

Thanks Mike. I would love to do this with some smaller, more affordable amps but the setup and all that for this was a real PITA. Not something I want to take on again any time soon.