lukeamdman

Dang...two months ago I would have picked up all 8!!

Lab Gruppen IPD 2400 - 4ohm stereo: I was really expecting this to do better at 4ohm, but I still couldn't get this amp to output more than 500w RMS one channel driven or over 250w RMS with both driven. Perhaps LGs power ratings are a pure burst/peak ratings and it simply can't sustain that kind of power for over a second? Lab Gruppen IPD 2400 - 5.5ohm stereo: Due to results at 2ohm and 4ohm stereo with the horn subs, I thought I would change it up a little and this time I used my ported AE TD18H+ drivers. Even at 5.5ohm and 80hz, trying to increase even 0.5db above these levels resulted in the strange pulsating tones after ~2 seconds into the sine wave. Still no clip/limiter lights for any test.

I was more interested in how the resistance changes as the voltage/amperage/excursion also increases. Sure the starting load may be 1.989ohms at a single volt, but will that go up or down once you're at 80v, and by how much?

Yeah, it's powering a pair of BMS 4594ND (8ohm) that are 118db sensitive....no issues to report for this application

Lab Gruppen IPD 2400 - 2ohm stereo: At the voltages listed above, it was fine for ~2 seconds and then it seemed like the frequency all of the sudden doubled and was pulsing? Clip lights never came on for any of this, but trying to go any higher in volume made this behavior happen even faster. I expect the 4ohm test to have much better results.

After looking at the specs, it appears to only be accurate down to 45hz. Dang.

Would this work well/accurately to measure amperage draw? It's compatible with my Fluke 117. http://www.amazon.com/gp/product/B000EA1ETC?keywords=fluke%20amp&qid=1444928046&ref_=sr_1_3&sr=8-3 I plan to re-run some of these tests at lower frequencies AND while dividing the load between (8) sealed FTW-21 drivers. If that Fluke clamp works, I'd be able document the resistance of the load while at the threshold of clipping. That'd definitely give more accurate numbers for power output.

My guess is that it would have to be an inadequate power supply. If I understand the Crest/Peavey 7.5/7500 amps correctly, similar to the SP amps each channel is already a "bridged" amp, which is why they can't be bridged again into a single channel. If rail voltage were the issue, one channel driven would also be limited to ~57v into a ~2ohm load as well which obviously isn't the case. The Crest CC series will also output more at 2ohm with 1 channel driven vs. 2 channels, but it's not nearly as dramatic of a difference and it's more forgiving (it'll actually show clip lights instead of simply power cycling without warning).

Based on your experiences with the 7.5 and 7500 I knew how the 2ohm stereo test was going to turn out I bought mine for the sole intention of 4ohm stereo and it's awesome for that.

Agreed. The SP amp tests were definitely hard on the drivers. Any other testing with the SP amp will have to be with all eight FTW-21s or a pair of IPALs on a single channel.

Crest Pro-Lite 7.5 When driving a 2ohm load, it was either completely fine or power cycling. Even with one channel driven, 81v for 2-3 seconds was no problem. Trying to go up even .5db resulted in an immediate power cycle. Same behavior with 2 channels driven. It may reach its specs at 2ohm stereo at 1khz, but definitely not in in the bass region.

The (8) FTW will be in 4 large dual-opposed boxes, and they'll be placed exactly where the Ghorns are today with the Othorns sitting on top of them. The plan is to wire the two drivers in each cabinet in parallel (FTW/UXL are not DVC), and then wire two cabinets in a series for something around a ~4ohm load. The pair of CC5500 I'll have sitting around that are currently powering the Ghorns should be perfect for the job. If the CC5500's don't work out for whatever reason (not sure what their sub 10hz performance is like), there's always the SP2-12000 to try as well.

LOL! The only way I can afford those FTW is by selling the Ghorns...and also because of the group buy price they have going on right now! I already have a solid buyer for the Ghorns, and if he had his way, they would have been in his basement well over a month ago

Every fiber of my being wants to keep the GH and just add the FTWs to the four horns, but doing so would require me to move the TV and L/C/R speakers forward 2ft and they're already way to close to the front row as it is. My room is just too small for that. The other issue is the funds... To keep the GH I'd need to buy even more amps!

I had already done the math for the amperage, so I knew it was more of pretty much everything with the SP amp The only caveat is the frequency difference between the tests. I could re-run the SP test at 32.9hz to find out? In a few months I'll have (8) sealed FTW-21 in addition to the Othorns, so that will open the door to some lower frequency testing as well.

It's a little hard to tell since the frequency wasn't the same. The bridged amps were tested at 32.9hz, and the SP was tested at 27.5hz. The excursion minimum on the Othorn is 30hz, so both were close to that. The SP amp was definitely harder on them thermally, since it was ~6kw per driver compared to ~5500w shared between the two, but even so, excursion was surprisingly high with the bridged CC5500. I was really impressed with the Crest, and I let the sine wave continue at 1db into clipping to see how long it would go. It maintained a steady 154v until it tripped its magnetic circuit breaker (the power switch) at ~4-5 seconds in.

This made wiring both Othorn cabinets in series a breeze:

Reserved

Reserved.

Here's a comparison between the Rigol scope and my fluke meters:

EDIT: The testing methodology was updated to use a non-reactive load (water heater elements). I purchased 10 of these (Camco 6000w 240v low watt density): https://www.amazon.com/Camco-Screw--Foldback-Heater-Element/dp/B000PSB3B2/ref=sr_1_1?ie=UTF8&qid=1468811988&sr=8-1&keywords=camco+6000w+240v Each was measured and the resistance was either 9.9 or 10ohms, so with 5 wired in parallel for each channel the resistance came to almost exactly 2.0ohm. 2ohm stereo or a single 4ohm load utilizing all 10 can easily be wired. Utilizing just four of these elements per channel I can wire two 4ohm loads ((2) in parallel + (2) in a series). http://i.imgur.com/3r0i5nK.jpg http://i.imgur.com/iRR7pS6.jpg Testing Summary 1. For the CEA-2010 burst tests I use REW as the signal generator and a Rigol DS1054Z oscilloscope with a 10x probe to measure Vpp. The amps are pushed as far as possible while still being able to produce a clean CEA-2010 wave form. 2. The second test is 12 seconds in duration at 20hz at maximum clean output. ** What these tests do not reveal! ** - Efficiency (I'm not measuring current draw from the wall) - Distortion/THD ___________________________________________________________________________________________ Crest CC4000 - Bridged Crest CC4000 - Stereo Crown XLS 2500 - Bridged SpeakerPower SP2-12000 Lab Gruppen IPD 2400 Behringer iNuke NU4-6000 - Bridged Behringer iNuke NU4-6000 - Stereo - 4ohm Behringer iNuke NU4-6000 - Stereo - 2ohm "Cube Amp" - Stereo - 4ohm ____________________ ** These tests below were performed with my (8) sealed 21" drivers as the load. I no longer have these amps so I can't re-test with the latest method ** ____________________ Crest CC5500 Peavey CS 4080HZ

Ok guys, just did the same test with both channels driven. I was able to hit the same 86.5v without clipping and registered 139.0db. I then bumped the volume by .5db and registered 91.3v and 139.3db...? Also, no clipping with this? I then bumped the volume by another .5db and registered 91.3v briefly and it then went back down to 86.5v. The SPL briefly hit 139.6db but went back down to 139db. I assume there were clip lights but I only ran the test at this volume once since after this I could smell a little bit of voice coil from the subs if I got right up next to them.

That definitely wasn't easy on the driver. I'd say excursion was around 2" peak-to-peak, which is slightly beyond the xmax rating but well within the 80mm xmech. It was also one of the few times I've put my hand on the motor housing and it was warm. It would take the meter around a second to show the voltage reading, and I let it go another second or so to make sure the voltage didn't drop. Even so, ~2 seconds of that is a lot of any single driver to take.

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:

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!