JL Audio 500/1 True Output and Efficiency?

[MisplacedTexan]

I have found a JL 500/1 (not the V2) for sale locally at a good price so I decided to do some research:

Its claimed output is 500w RMS, and the manual says that a 50A fuse is required. Assuming that power measurement is at 14.4V, then its efficiency would be 500/(14.4*50)=69%. Right?

Then I found the following review of the amp, quoted below: http://www.carsound.com/review_archive/amps/jl_5001.html

“At 1/3 of its maximum output, the 500/1 measured 57 percent efficient, which is somewhat lower than the rest of the class D units that we’ve seen to date. In addition, the efficiency remains in the mid 50’s all the way to full output rather than increasing to the 80-percent-plus that we’ve seen in other units. The result is an amp with efficiency that’s about 30 percent better than a class A/B unit at 1/3 output and roughly equal at full output.”

The same review claims output of 600W RMS from the amp. If the amp is in the “mid 50’s” efficiency, there’s no way it’s making 600W or even 500W of power (It’s 425W if you assume 59%). Am I missing something here, or is someone lying/ measuring incorrectly?

Click to read more...

 

[gunz4me2 10+ year member]

Efficiency is generally the ratio of how much current the amplifier draws to output a specified amount of power.

They rated that particular amplifier into a resistive load at:

605 watts @ 14 volts for 4 ohms

AND

620 watts @ 14 volts at 2 ohms

IMHO those numbers are pretty good output figures for a 500 watt amplifier.

Think of efficiency more like this: I had a certain old school 500 watt class AB amplifier that would draw 85 amps when producing 500 watts. The simple way to think of it is

Amps X Volts X %efficiency = watts

In my case it was: 85 amps x 13 volts x 45.24% efficiency = 500 watts RMS

ETA: The efficiency for the JL Audio isn't the greatest if it is in the 50% range because class D amplifiers are generally in the 70 to 80% efficiency range. This means they don't have to draw as much current (think amperage) in order to produce their specified output. Using my previous example, your typical class D amplifier would need 48 to 50 amps of current draw to produce that same 500 watts RMS compared to the old school POS that I just sold.

 

[MisplacedTexan]

"your typical class D amplifier would need 48 to 50 amps of current draw to produce that same 500 watts RMS"

Per the review, the JL amp in question has much worse efficiency than a typical class D amp. If that's true, how could you get 500W+(more than 50 amps current draw from the battery) out of the amp without blowing the JL specified 50 amp fuse?

 

[its_bacon12 10+ year member]

"your typical class D amplifier would need 48 to 50 amps of current draw to produce that same 500 watts RMS"Per the review, the JL amp in question has much worse efficiency than a typical class D amp. If that's true, how could you get 500W+(more than 50 amps current draw from the battery) out of the amp without blowing the JL specified 50 amp fuse?

You wouldn't. Something's wrong with this math, reminds me of Obama's.

 

[dB-r 10+ year member]

You wouldn't. Something's wrong with this math, reminds me of Obama's.

LOL.

JL 500/1 is a great amp. Just get it. Screw that stupid review.

 

[its_bacon12 10+ year member]

LOL.
JL 500/1 is a great amp. Just get it. Screw that stupid review.

Lol yeah it is a good amp, the review likely was wrong.

 

[dB-r 10+ year member]

No it could have been right about the efficiency, but the design in those amps is not meant to be average efficiency, but to produce same power over a broad impedance load. So I would expect some reduction in efficiency, but I don't think that was ever a selling point on the / series.