So just what is a JBL Watt?

Hi,

OK; I'm an eletrickle enjunear so I know a little about the mathematical magic numbers like 1.4142 in doing power calculations.

For my 4344 project the JBL 2235H datasheet specifies its maximum power capacity as:
- 300W Continuous program (typical program material)
- 150W Continuous sine wave

I have heard people in the industry say that JBL power specifications are understated. So what magic number do JBL use to convert this specification into actual true real-life maximum power the unit can handle before meltdown? 1.25, 1.5, 2.0 ???

This weekend at my brothers friend’s place they did some power amp tests on his 4435’s. I am just stunned that the 2234’s in them did not catch fire (and even more so that I still have hearing!). The 4435 is rated at continuous program of 375W and looking at the graphs for bi-amp the maximum wattage at LF is 300W (with an absolute maximum hinted at of 350W) continuous sine wave. Now one of the amps tested on the LF was an Australian Monitor AM1600 ratings per channel; 525W-8ohm, 800W-4ohm, 1200W-2ohm. For those outside OZ this is considered a ‘BEAST’ of an amplifier by people in professional sound rig circles. A wall-shaking series of tests with the amp peaked right out left the JBL’s asking; “excuse me; is that all the power you have?”

I guess this is a multi-faceted question: 1) how underrated generally are JBL bass drivers?; 2) what are people’s feeling on the true max CSW rating of a 2235H? and finally (and more contentious????) what amp power rating would be recommended for the LF of a 4344 (a single 2235H)?

jarrod

If you have access to Bassbox or another speaker simlator it will give you a good 3 D picture of the 2234/2235 ratings.

There is thermal power, and cone displacement acoustic output, then you have music signals which hardly repesent a sine wave, although it should be noted at least 1/2 the power of a music signal is in the bass.

The measure of real acoustic output is often more meaningful when we are talking about woofers output as opposed to tweeters...they oftern burnout, particularly when an amp if clipped beyond its rated output.

Ina

This is the 2235 graph,

Note the simulation here shows the woofer tuned to 28 hertz, rather than the 22 hertz as per the 4435 system.

This tuning frequency can be any number to get a the desired response, however the lower the tuning frequency, the lower the acoustic output is in the bassband, the tradeoff being low end extension versus output.

But , as you can see , either way they do go loud. I recall in the JBL diy subwoofer article they tested the 2235/2245 systems with amps as high as 2Kw without damage.

Regards your question of amp power for the LF 4344, I would use at least 200 watts rated at ohms, 300-400 would be better.

Ian

JBL vs power....

Well it's been my experience ( also being an engenear ) that if you follow these simple rules, the jbls will keep on thumping:

(1) NEVER NEVER clip the amp ( remember the piston motion is directly related to the signal waveform ) and a squarewave is STRAIGHT up+down...:) Any speaker that tries to follow a squarewave will be destroyed. If you read the "danger: low power" jbl article that will explain it in laymans terms.

Bigger IS better....BUT:

(2) Do not exceed the maximum travel or things tend to bend, rip, deform and **move out of the gap at precarious angles**

You should see all the JBL vented gap cones that have been overpowered by sound company guys using crown 5002's - the cone actually will LEAVE the gap and when it comes back down, it shorts the coil and leaves a trail of arc welding spots on the pole piece. Of course the crown keeps on producing power SO a small fire starts.....:)

(3) Use an amp that has TESTICLES and can store energy in the power supply. The "carver" method and some switcheroo's will SAG at the slightest high current drain ( but of course look real nice on the spec sheet ). This power supply intermodulation REALLY kills the punch. And unless your "tweako" tube amp has 48 paralled outputs, it will have no punch either...( apologies to the tube guys out these )

Think of it this way: You are sitting at the traffic light looking to race the guy next to you. You have a 1970 big block chevy with sticky tires and the kid next to you has a riceburner with a turbo tweaked 4cyl and all seasons...

Assuming that the "published" horsepower specs are the same, the light changes and who wins?....right.

The larger rotational inertia is analogous to capacitance in the supply. And of course he then becomes a muscle car enthusiast and wants to buy yours...:)

(4) HIGH PASS FILTER... keep the really low stuff out of the mix and the speaker won't misbehave and unload in the cabinet...flop...flop...flop...

(5) Dynamic range.....if your program material is heavily compresssed ( IE: FM radio ) or Distorted ( remember the sum of all harmonics when a signal is clipped! ) The voice coil can't get rid of the heat fast enough.

In general, the JBL's are indeed underrated BUT using NEW recones means you get NEW glue, NEW formers, NEW adhesives and therefore all the advantages - look at the 2230 vs the 2235H specs....same speaker but BIG difference in power...!

sub

its very easy...

too low :( .....too loud:D ,....too late:banghead:

HP:cool:

I wholeheartedly agree with you, Subwoof, especially about amplifiers! Switcheroo power supplys, 27lbs, and a two rack space package that can produce kilowatts per channel but lack the most important facet of music playback, especially with bass! BALLS! High power, lightweight amps, power supplies that defy the laws of physics, but no BALLS and no punch! And these high tech marvels of the audio industry also have another downside. They get tired after a few hours of playing and being used under demanding conditions!

One of my favorite amps for sub bass use is the BGW GTA! Huge power supply, and can do loads like two ohms all day and all night, and produces a gargantuan, clean, and musical sounding bass! 80lbs of class AB output design!

My feeling has always been, " If it dont weigh enough, It cant play enough " !

:cool:

Sub and Scott:

I agree, except on the inertia deal, the more inertia, the less capacity to change, applies to power supplies and engines, You want to change (accelerate) quick, look at the flywheel/clutch on F1, almost non-existing.

I have a Crown K2 driving 4 2245H´s, the think kicks!, it is a very digitalized power supply, but I guess they got it right.

I invite slander, libel, personal attacks, etc., We need another funny thread.

Alex

Ive heard the K2 and it does sound nice, but would be more for my 15,s rather than subs. I like the way big power supply amps drive subwoofers. Especially running low impedance loads, that I have.

The Macro, and Micro Tech line as well as the K series of Crown amps DO have speed and snap, which for me is good in the 15,s audible range. But for the earth shaking, gut thumping low end I like I havent found a better combination on all my subs than 1 BGW GTA and 3 Crown PSA-2,s!

BTW, I am a crown fan, I also run Crown on my mid horns and tweeters.

:cool:

Quote:

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Originally posted by subwoof
NEVER NEVER clip the amp

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Bingo...

Nice posts Subwoof and Dang Aussie...

Maybe off-topic, but on the clipping - if there is ANY clipping ANYWHERE in the signal path you're at heightened risk of transducer damage. Gigging last night, we had hella time stopping the bass input from clipping - we had inline comp/limiters and could not tame the beast. Before I figured a workaround, I jumped onstage to play some harp and heard the monitors go into apoplectic shock whenever the bass was really driving (clipping) - i.e., the effects of a single input stage clipping ripples through the ENTIRE system.

So, jarrods, I guess the message is, if you're going to play those kind of games - which can be plenty fun - you'd best:

1) bypass any emphasis EQ and run flat
2) make-sure you've got a high-pass filter rolling things off at 30Hz, or maybe even slightly higher.
3) don't dare clip.
4) :dancin:

Well if I have'nt sold my Clair Bros 700B you can borrow it for a try out when you get your system up.

Its an oldy but a goodie, no dynamic limiting or compression on that fella, threshold of clipping @450 watts a side. Never been there.

Actually I recall a Pro comparison with a 400 watt/channel Mackie driving JBL system 700's, the mackie was sweeter but was distinctly less punchy.

Mosfet amps can be like that, particularly when they heat up. But in your "domestic situatation" if they get hot" you are offically DEAF...LOL...game over Man, game over.

One thing about the JBL's is as you turn up the wick, they sound bigger & bigger, not necessarily louder and remain clean. But the damage can still be happening and prolonged exposure can lead to permanent hearing loss.

I have often clipped my hears in front of the stage at my Local"The Espy" When Phil Para plays Hendricks. Unfortunately the new owner trashed the JBL rig for an EV Deltamax.

Ian :rockon1: :shock: :cheers:

hey bob....make up a "H" pad using a male+female XLR barrel for that bass rig board input - and use a NEW battery for each gig....

I see this channel clipping issue all the time - it's usually caused by ( sorry in advance ) a cheap mic preamp that trims the input by changing the feedback loop gain *NOT* by using actual pads before the head amp stage.

ALL the generic music store types ( mackies / behringers / samson / etc ) are guilty of this...

On +/+ 15v supply boards all you need is a few volts peak ( easily accomplished with preamped bass guitars ) to clip it and NO adjustment of the trim will get rid of it...these "one pot wonders" do not work.

Ever wonder why the big boards have +/- 18 volt massive outboard supplies??? And extra pad switches? And hp filters?

This also happens with consumer CD players that drive line inputs on cheapo DJ mixers. I use a simple pad ( 2 resistors ) inside the 1/4 jack that knocks it down 10-20db.

Ian - I ressurected a handful of the old clair 700a's for a client - he will go to the grave with them...:)

Alex - the K2's a nice amp but since the steep onboard bandpass filters ( required to keep powersupply noise out of the signal ) interferes with other parts of a complex system, they are best used ( as your case ) as stand-alone amps. And why crown didn't allow use of the "pip" cards is a mystery...for that reason this amp is ignored by the SR industry...

Scott - wanna beef up your PSA2's to the showco mod? If they are the late model I can guide you thru it assuming you can solder and chew gum at the same time...:)

sub

Quote:

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Originally posted by subwoof
make up a "H" pad using a male+female XLR barrel for that bass rig board input - and use a NEW battery for each gig....

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Hey, Subwoof...

Great idea. I'd like to carry one of these around for situations where the bass player doen't. Give me an idea how you constructed one - a schematic would be cool... :yes: What were your R values, and in/output impedances?

We are now sufficiently off topic that maybe we should take this to pm's / emails...