lukeamdman

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.

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 haven't looked at the exact unit and specs yet, but you should be able to get decent info for sine wave testing over shorter duration.  You would have to check if it can look at peak or some sort of sustained maximum current to measure shorter bursts.  I'm not really sure it will give you all that much more info other than being able to see how the amplifiers draw power from the wall at the same output level, which gives you insight into the real world efficiency.  Ironically a couple big pro amps dump a lot of power into cooling fans if the temp gets hot which can significantly affect efficiency of a class D design.  This shouldn't be an issue in home use though.

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?

You're only using this amp for your mid/hi section though, right? In your case, no big deal and "plenty" of power for the application at hand.

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. 

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. 

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

...

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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. 

I've noticed a recurring trend with most of these class-D type amps that they produce far greater output numbers (and more stability) with just one of two channels driven.

 

Is this behavior simply tied to a PS that can not provide good solid current enough for two channels with these kind of high output numbers?

That's my exact guess. By process of elimination, and talks with one of the peavey/crest designers, it is the only thing that you could attribute to the shutdowns basically. It ain't line sag....

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). 

Great data. Sad for my poor little 7.5

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.

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.

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. 

Okay, I see what you're up to. Honestly, I'd probably do just this. Swap out the Ghorns for massive sealed displacement. You've got the "goods" with dual Othorns doing the major lifting and with a sick sealed system you finish off the rest of the bandwidth with ease. Especially in a room like yours (mine is about as big).

 

Though... I don't want to nor feel comfortable persuading you to sell off the Ghorns. They are just too cool and I know you really love yours. Honestly surprised to see you do it but ... it's not a lateral move doing big time sealed. It's the end game.

 

I can make all sorts of suggestions but I'd rather be a fly on the wall and see what happens. Very interesting.

 

Excuse me. Master of OT here.... I'll let this get back to the tests.

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.  

 

Worries about funds, orders eight FTW21's.

 

You're lucky I'm at work or that would have been a good meme made as we've got several pics of you in varying degrees of amusement non-amusement.

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 

Wait what? You dumping the GH and just going sealed and Othorns? Or adding in the sealed to the 4 total horns? Wild son! 

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! 

again, i'm a little foggy this morning, but i think you have to check the current for heating not the watts.

 

6148 w into 1.2 r is 86.5 v.  86.5 v divided by 1.2 r is 71 amps.  one channel per driver so 71 amps through each driver.

 

5310 w into 4 r is 145.7 v.  145.7 v divided by 4 is 36 amps.  drivers in series so 36 amps through each driver.

 

with almost twice the amps, the spl at the listening position was 0.4db louder despite more than twice the watts, indicating almost total power compression past 36 amps.  at least that is what i was thinking.

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. 

neat.  if i'm interpreting the result correctly, the ipal's can't handle the current and compressed out almost all the power gains afforded by the sp amp?

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.

                                       Volts                 Amps                 RMS Power               Peak Power (approximately)

Max Clean:                   86.5V                 71.08A                6148.1W                     8693.4W

 

~1dB into clipping:      88V                    72.31A                6363.28W                   8997.7W

 

 

 

Your outlet power is 122V x 30A =3660W times two breakers is 7320W of total power (RMS) available to your amp.

 

That means that at max clean power your amp is ~84% efficient driving 1.217 ohms.  Not too sure how 2 channel testing would change things, efficiency might go up and power per channel will go down perhaps.

 

Thanks for doing that Luke, good contribution to the thread. That is impressive sustained power @27Hz.  Your driver had to be about at it's mechanical limits?

 

If Brian O. happens to read this post, correct me if I am wrong about any of this and I have a question:  Have you comparison tested your amps using high voltage/high impedance vs. high current/low impedance?  Is there a difference in efficiency or distortion numbers? 

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.

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:

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!