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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Subwoofer FUD Forum Archive => Topic started by: Josh Billings on January 27, 2008, 08:32:10 am

Title: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on January 27, 2008, 08:32:10 am
What do you guys think of the Crest Pro 8200 for an amplifier for the LAB Subwoofers. I'd prefer to not spend $2,500 on 2 amps when i can get the QSC 4050HD and whatnot for pretty cheap, but i want to make sure i get the right fit for these boxes.

I want to make sure we can run them close to clipping (Maybe occasional clipping) and not burn up drivers. Reconing and replacing LAB drivers are just a pain in the ass.

I was also considering Crest CC4000s / Peavey CS4000s, QSC RMX4050HD or Crown XTI-4000s. I am really concentrating on the fact that it's a 800 watts a 3 ohms cabinet (I believe 2.7 is the minimum).

I also thought about the I-tech 8000 running in stereo with 2 boxes per channel, but i know these things lose power when the impedence drops below 4 ohms so i was kinda shying away from those.

It's just so tough to decide because so many specs are based on 1khz and sometimes the 20hz-20khz number is substantially lower and sometimes it isn't much lower at all (Would prefer one that doesn't lose a lot of power down low). Let me know what you guys think

I know the QSC PL6 PFC (2 cabs per channel) would be great, but i only have 20 amp circuits to deal with most of the time. I

-Josh Billings
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on January 27, 2008, 08:54:39 am
Hi Josh,

Probably over budget here but you might want to check-out some of the digam powersoft amps... Anyways,...in addition to output, power requirements, and the normal specs I would consider a high damping factor for a sub duty amp...http://www.teamaai.net/kevin/2cents.gif

EDIT: My "dream" amp for sub duty would be one of the powersoft K series (damping factor >5000 20-200Hz)...Very Happy  

Kev
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Jesse Soden on January 27, 2008, 07:21:45 pm
The first two LAB's that we built were powered by two QSC RMX 1850HD's. Yes, the dampening factor is not the best for that model, but they were cheap (our subs, venue's amps). We had absolutely no problems with blown drivers for over 3 years, even with excessive clipping. When we built our current system, we opted for PLX series amps, and decided to use the 3402 per two cabs. The dampening factor is greater than 500, which, for the buck, was acceptable. Running them in parallel input mode gives at least 1100W (figuring on 4 ohms for simplicity). Again, no relative issues, except when the drivers come loose in the cab (I don't want talk about it!). We've tried the 1602's in bridge mono, but I was not comfortable with the impedance of the cab being below the 4 ohm minimum rating of the amp in bridge mono. We also tried a few Crest amps, with destructive results. I never put an Oscilloscope on the amps output to see what happens at clip, but we started chewing drivers up left and right (tearing the surround). I do remember reading on this forum a few years back that Crown (can't remember the model) amps tend to do the same thing. I also remember discussion of running 4 cabs on a Power Light 9.0 with good success (that's 2000+W/sub!). So, after replacing a few drivers (at least they're fairly cheap!), we're back to the 3402's. I guess the crucial thing is to make darn sure that the amp in use has soft clipping. I've been told that Yorkville amps would be an excellent choice (higher dampening factor), but we don't like the weight (sucks getting older Sad ). I hope this helps!
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Pascal Pincosy on January 27, 2008, 08:45:42 pm
Kevin Pippen wrote on Sun, 27 January 2008 13:54

EDIT: My "dream" amp for sub duty would be one of the powersoft K series (damping factor >5000 20-200Hz)...Very Happy

The Powersoft K series looks even better when you get it with the DSP module included. The limiting features are bar none. Between peak limiting with feedback from the amp portion, and the RMS limiting, again with feedback and clear metering (unlike the I-Tech) you can set, forget, and never blow a sub driver again.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Al Limberg on January 27, 2008, 10:21:10 pm
Looks to me like some folks should do a search on 'damping factor'.  Pay particular attention to JR's  (John Roberts) posts.

?;o)
Al
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on January 27, 2008, 11:29:12 pm
Hello Al,

I have done some research and have made my conclusions that amplifiers with a high damping factors have greater control over the movement of the speaker cone and will deliver tighter bass...http://www.teamaai.net/kevin/2cents.gif

That's just me,...and of course everyone's entitled to their opinion...Smile

Kev


Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Tim McCulloch on January 28, 2008, 12:52:43 am
Kevin-

A DF of >25 at the end of the speaker cable is probably sufficient.  The claims made famous by Crown that high DF creates some kind of sonic superiority have been largely busted... A higher number is better, but only up to a point.

If you read John Robert's writings on the subject you'll understand why.

Have fun, good luck.

Tim Mc
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: John Roberts {JR} on January 28, 2008, 10:36:12 am
Everybody's entitled to their own opinions but the facts must be shared by us all..

Damping factor was worth comparing between old tube amps but modern solid state amps are arbitrarily good. If anything in SR applications you may need to pay attention to wire gauge on longer runs, as this will be more impedance than modern amplifier output stages.  

I think this is covered in Study hall.

JR
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on January 28, 2008, 10:51:20 am
Hello John,

Roger-that and agreed!...Smile My insertion losses were less than .02 ohms on this budget install... That's #10 AWG in parrallel pairs...Very Happy

http://www.teamaai.net/kevin/Youth/BOOTH4.JPG

http://www.teamaai.net/kevin/Youth/BOOTH3.JPG

http://www.teamaai.net/kevin/Youth/BOOTH9.JPG

http://www.teamaai.net/kevin/Youth/BOOTH10.JPG

Kev
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Evan Kirkendall on January 28, 2008, 11:52:21 am
Josh Billings wrote on Sun, 27 January 2008 08:32


I know the QSC PL6 PFC (2 cabs per channel) would be great, but i only have 20 amp circuits to deal with most of the time.

-Josh Billings


You can run a PL6.0 on a single 20 amp circuit with no issues.


My favorite LAB sub amp is the PL9.0. Smile




Evan
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on January 28, 2008, 05:39:40 pm
not at 1.5 ohms per channel

-Josh
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Al Limberg on January 28, 2008, 06:11:31 pm
Due to the acoustical impedance of the LabSub in conjunction with the electrical impedance, the load the amplifier sees from a pair of cabinets per channhel is probably closer to 3-4 ohms per amp channel.

?;o)
Al

Title: Re: The Perfect Amp for LAB Subwoofer-Not just a single spec.
Post by: Ivan Beaver on January 29, 2008, 06:38:53 pm
Kevin Pippen wrote on Sun, 27 January 2008 23:29

Hello Al,

I have done some research and have made my conclusions that amplifiers with a high damping factors have greater control over the movement of the speaker cone and will deliver tighter bass...http://www.teamaai.net/kevin/2cents.gif

That's just me,...and of course everyone's entitled to their opinion...Smile

Kev




Yes that is correct, in a way.  High Damping can help, but there is  much more that contributes to the overall "sound" than damping.

I have done  picky tests with amp that have damping factors over a 10:1 range (and in between).  In one case the amp with the lower damping factor easily beat out the one that had damping 10 times higher-in terms of overall bass "tightness" with music.

Do some more reading and you may have a different opinion.  You have to look at ALL the issues involved, NOT just a single number.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: jeffhtg (Jeff Kenney) on January 29, 2008, 09:07:04 pm
What is the application?

I still swear by my vz5000's.. old as dirt and still slamming away my labs.. I'm crazy tho and have 1 per side.. and still have some 4050's running another 4.. But I'm running heavy dance music 7 nights a week with DJ's slamming into limiters.

Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on January 29, 2008, 10:32:00 pm
Kevin Pippen wrote on Sun, 27 January 2008 07:54

Anyways,...in addition to output, power requirements, and the normal specs I would consider a high damping factor for a sub duty amp...http://www.teamaai.net/kevin/2cents.gif

EDIT: My "dream" amp for sub duty would be one of the powersoft K series (damping factor >5000 20-200Hz)...Very Happy  

Kev


Ivan Beaver wrote on Tue, 29 January 2008 17:38

Do some more reading and you may have a different opinion.  You have to look at ALL the issues involved, NOT just a single number.


Hello Ivan,

I love your advice because I'm always reading, and doing research...but some how things got out of context through the course of this thread... I'm the first to admit that I'm not a pro-sound expert but on the other hand I'm not a complete idiot either... I started out in sound as an early 70s audiophile (and usually a stoned one at that)... I definitely agree that all things should be considered when specking an amp for a specific purpose... If money were no object I "personally" would take a hard look at the Powersoft K series sub-duty and not just because of it's damping factor... It requires little power and it offers a huge output to weight ratio,...and what can I say...I just like em...Smile

Cheers!

Kev  

     
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Greg Spydell on January 31, 2008, 12:06:11 am
I have had huge success with the Digam Powersoft K10... hooking up four (4!) Adamson T21's... rocking out... and never destroying the amp. The K10 weighs around 25lbs, and is 1RU, and when hooked to a 240V you get 14kW... amazing. Sounds great for a digital amp with full DSP. The Adamson T21's are a 2ohm box... so you just build a Series/Parallel Connector and you are all set... of-course you are under-powering but there is an amazing amount of headroom. Smile

Powersoft:

http://pro-audio.powersoft.it/an_series_list.php?use_in=53&a mp;a mp;id_menu=271&obj=12


Adamson T21:

http://adamsonproaudio.com/products/yaxis/t21/t21.htm
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on January 31, 2008, 09:02:41 am
jeffhtg (Jeff Kenney) wrote on Tue, 29 January 2008 18:07

What is the application?

I still swear by my vz5000's.. old as dirt and still slamming away my labs.. I'm crazy tho and have 1 per side.. and still have some 4050's running another 4.. But I'm running heavy dance music 7 nights a week with DJ's slamming into limiters.




Looks like we are running similar setups. I have large dance music artists come through all the time and we had 4 LABs on 4050s and they sounded pretty good. Not sure how far i could of pushed them (to clip all night and survive?)

Have you blown drivers on the 4050s?

P.S. The 5000s are power hogs (same reason i didn't just hook up 4 to the PL6)

-Josh Billings
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on January 31, 2008, 09:08:11 am
Hey thanks for recommending the most expensive amplifier made Smile

C'mon guys lets be realistic.

I bought 2 4050HDs and found the 4050HD seemed like a pretty safe amp choice for LAB Subwoofers (1 per channel). This is driving them not SUPER Hard, but close to clip.

I was able to blow a pair of LABs off a RMX1850HD (In bridged mode per subwoofer).

-Josh Billings
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on January 31, 2008, 11:46:05 am
Josh Billings wrote on Thu, 31 January 2008 08:08

Hey thanks for recommending the most expensive amplifier made Smile

C'mon guys lets be realistic.

Josh Billings

I did say it's my dream amp...Smile

Kev

EDIT: Edited for stupidity...
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Pascal Pincosy on February 01, 2008, 05:04:04 am
Josh Billings wrote on Thu, 31 January 2008 14:08

Hey thanks for recommending the most expensive amplifier made Smile

C'mon guys lets be realistic.


The thread title is "The Perfect Amp for LAB Subwoofer"  Cool

FWIW, the 2 amps (out of the many I've tested) that sounded best with my Bassmaxx hornloaded subs were the QSC PL380 and the Powersoft.

And the Dynacord PowerH is a great option as well if you're trying to run off wall power.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Ivan Beaver on February 01, 2008, 06:38:06 am
Yet again the term "perfect" means different things to different people.

To some it is performance, to others-price, and to others size and weight.

There is no "perfect" anything.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: jeffhtg (Jeff Kenney) on February 02, 2008, 05:54:11 pm
I bet you wouldn't have blown them if you had 6 1850's and 6 labs Smile
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on February 02, 2008, 08:04:43 pm
I ended up going with a pair of 4050HDs. Didn't run the subs SUPER Hard, but they ran super cool and felt like they were coasting as compared to the 1850s and the PL6 even.

We run heavy dance music too so i can definitely work em out.

I'll give em a better work out this Tuesday and report back.

But no blown drivers and some powerful sound.

I just wish it had display lights like the PLX series (signal, -20, -10, clip). This is just "Signal" and then "Clip"

FYI You can get these for $940 from Guitar Center by just saying you got a quote from Sam Ash for $940. You could possibly even get them lower, but that's the lowest i could get them. I think if you say Sam Ash, Guitar center will give them away to get the sale. With the $100 rebate that bring the amps to around $1825 out the door for a pair.

-Josh Billings
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on February 07, 2008, 08:41:24 am
UPDATE

With 2 of the 4050HDs i can run them close to clipping all night long and haven't blown a sub yet (4 hour long sessions, house music DJ sets).

I may not be pushing these things to the max, but i feel pretty comfortable with them and i know they don't get too much louder (i've had them on a PL6 before).

Overall the 4050HD is a good choice for a LAB Subwoofer + you can get them super cheap & they sound great. Only drawback is weight, but it's not THAT Bad.

-Josh Billings
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Kevin Pippen on February 07, 2008, 09:28:52 am
Josh,

Sounds like your very pleased with your purchase...Very Happy That's all that really matters...Cool

Cheers!

Kev
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Clive D Milne on February 12, 2008, 08:03:56 am

  I run an IT-6000 on 4 labs, seems to run fine and shift a sizeable chunk of air.
  Had the amp serviced recently and the tech bench tested its output.  He said he was pretty impressed with what he saw.  It was happy to run all day pushing 7300W bridged mono into 10 ohms.
This would imply that bridging an IT-6000 and pushing it into 3 labs wired in series would be a pretty good combination, (assuming you are running multiples of 3)
  Incidently, when running 4 labs off 1 I-Tech, you are absolutely under no illusion when the amp starts to clip, the sound it makes is absolutely brutal.  It sounds like smacking two thin planks of wood together...  hard.
    On the whole though, the I-tec is a very sweet amp.  Highly reccomended.
   regards
Clive.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Jesse Soden on February 12, 2008, 10:03:36 am
Throughout this discussion, there have been many speculations to what the actual line impedance of a lab sub is for the various number of labs in a cluster and the cluster orientation. I have the background and test equipment to measure and calculate the impedance vector over various frequencies and cabinet configurations. I plan on using a bass test cd with clean waveforms so that I can obtain the most accurate, RMS readings.
Thoughts, ideas? Are there any specific cabinet combinations that I should concentrate on?
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Alan Star on February 12, 2008, 05:09:36 pm
Great, I would be interested to hear your results.

Configs i'm interested in ....

A~ 2 Labs, all 4 drivers in parallel. (also would there be a difference in impedence between 2 boxes alone and 2 wired like this in a cluster of 4 (next to another pair) and if so how much difference would that cause)

B~ 2 Labs, drivers wired in series in each box and then the 2 boxes paralleled. (also would there be a difference in impedence between 2 boxes alone and 2 wired like this in a cluster of 4 (as above) and if so how much difference)

C~ 3 Labs, drivers wired in series in each box and then the 3 boxes paralleled.... and same again would that result change drastically between 3 standing alone and 3 in a cluster of 6.
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Alan Star on February 13, 2008, 08:18:54 am
... altho i'm not sure how much difference to impedance it is in a big cluster, if it makes any difference at all. You may be interested to hear ... I have monitored this a few times including this afternoon when doing a system check. On the iTech, it has a monitor display for load impedance, and it sees 1 box (2 lab drivers in parallel) as 5 or 6 ohms (it flickers between). This is concurrent with what i have observed running 2 boxes, the amp sees that load as 3 ohms.

I am not sure how accurate this is but with the extra loading of the horn it could make sense that it is an accurate diagnosis ?
Title: Re: The Perfect Amp for LAB Subwoofer
Post by: Josh Billings on February 13, 2008, 08:50:11 am
That's pretty dead on with the measurements they got at the pro sound shootout thing

The RMX4050HD does sound pretty great on these though. Really strong and i haven't blown a driver yet Smile

-Josh
Title: Crown K2's and I-tech 8000's
Post by: Andy Ferguson on March 02, 2008, 09:28:04 pm
We have used Crown K2's (one per box) and also the I-tech 8000's (2 LABS per channel) and both have worked really well.
We blew a 20 amp breaker with the I-tech 8000 one show, it must have been putting out quite a bit of output power.  As the owner of twelve LABS, I have become quite a fan of the LAB subwoofer design.  In 5 years, we have only replaced 2 drivers, both in the same box and the result of a broken pole piece, Not the drivers fault.  I'd put these 12 under anyones array in any arena and am quite sure they would do just fine.