Home > Consumer Reviews > JBL L8400P 12-Inch Powered Subwoofer with 600 watt Digital Amplifier (Black)

Got mine yesterday and out of curiosity after reading another review I put a kill-a-watt on it and tested it out.

Yes there is a "chirp" sound when it turns itself on from sleep mode. It doesn't border me however since it is not that loud and it only does once. In sleep mode, it draws about 20w. Awaked but not playing any big sound, it draws about 25w. Basically the sleep mode is really pointless.

I have other JBL Studio L series speakers and I can tell the big difference over those home theater speakers. But this sub I really don't hear or feel any difference. A boom is just a boom.

I purchased 2 of the L8400Ps as upgrade to my existing AV system and I am very pleased with the results as also reviewed by others. I enjoyed the upgraded sound system for the evening watching a dvd movie. The next morning I was curious and reached behing the subs to feel the rear panel and it felt unusually warm. It takes power to heat that much metal. I measured the current drawn by the subs and it came to be .3 ampere each which translates to 36 watts of power. Two subs would add up to 72 watts and that is too much power to be wasted continously.

The other negative comment I have with the subs is the "chirp" sound they make when they automatically turn on upon receiving a low note from the AV receiver. I find the "chirp" annoying while I am watching a tv program or movie when the "chirp" suddenly come on.

I contacted JBL and they replied:

1)The standby power drawn by the subwoofer is the way it is. The solution if I do not want to wast electricity would be to manually turn on and off the main power switch at the rear panel. Because of the way my subs are situated, I had to move the subs everytime in order to operate the switch.

2)The "chirp" sound is caused by a resistor in the electronics module which have to be replaced. JBL customer service said I should go to JBL.com and locate the nearest service station to have it done. I did that and the nearest station is over 100 miles away. Considering the size and weight of the subs in the box, that would be next to impossible. The box would not fit into my car.

AND SO I am giving Zero Star (one being the minimum) rating for the power wasting and the chirp. I still must give a full 5 stars for the quality of the audio to be honest. I am so much disappointed that such a good sub would be spoiled by poor design on 2 points.

May 17, 2009. After re-thinking I believe a 3 star rating would be more appropriate, but I can not change it by clicking the stars, so this have to do

We got two of these to go with our new surround sound system. All of the others are bookshelf speakers so we needed more bass for both music and movies. For me these speakers do an excellent job covering the low end. After some adjustments and fine-tuning they are working perfectly with the rest of the system. The bass is clean and crisp without overwhelming the rest of the system. I think you will find the bass from these more refined like at a movie theatre then some of the weaker subs out there that strain to keep up with the rest of the system. It does drop down to 22hz so you can feel it as well as hear it but it's not going to shake your pictures off the wall. I'm sure we didn't need two but....

They have a lot of power with the built in 600-watt amp. Be careful when comparing powered subs. Most manufacturers list the peak power for their subs so when you see 400 watts you may think it's comparable but if you look close that is peak with maybe 200 watts nominal. The L8400 shows 600 watts and that is nominal with 1200 watts peak. It is hard to find another sub with this power for the price from a company that is known for quality speakers. Kudos to JBL for giving us honest numbers and not trying to mislead us.

The sub is always plugged in and will turn on when it receives a signal from the AV receiver. At this point a blue light comes on, on the top of the sub. This lets you know that it is up and running. One quirk that I have noticed is that one of our subs will chirp when this happens and the other does not. They both work and sound the same except for the power on chirp. The chirp is a good audio reminder that it is activated.

Like the entire JBL Studio L series this is a beautiful piece of furniture and will look good in any room. Though the speaker itself is an impressive 12" the actual housing is not much bigger at about a 15" cube so it will fit very well in a limited space. The Studio L series speakers come in 3 color options of black, cherry and beach. Though all of the other speakers we have are cherry I went with black for the subs. It was a little cheaper and the general rule is subs are OK black even if the rest of the system is not.

I purchased this sub along with four new Def Tech Pro 1000 monitors and a Pro2000 center. I did not like the sound, and weak aesthetics of the Def Tech 1000 sub, thus I turned to JBL. Have owned many of their products over the years and have been quite please, though they have gone a little mainstream, and would support only their high end offering.

Customer Service: Couldn't believe it, but my first one that came was dead on arrival. Nothing, cables, receiver setting, just one big heavy dead black box. Contacted JBL, they had me try an analog run through the DVD output to be sure, but again nothing. They told me to return it as it was obviously defective. They even offered to replace itself themselves if I had any trouble through the retailer! I'll take that kind of service and caring any day!

Customer service, part 2: Called Amazon and explained the situation, they sent a new one at no charge, overnight and sending a call tag to return the bad one. I could not ask for better customer service, my hat's off to you, and empowering your customer service rep's to rectify the situation. No haggling, complaining, or needing to talk your way up the ladder to get something done. This is the makings of a customer for life.

Performance: Sounds wonderful. Sealed sub's like this are very musical, and very very tight. I love this type of sound. Ported subs are a cheap way to get the specs better, IMO, and requires alot less power. This sub has power to spare. It might not get all the way down like some people like, but this baby is low and super tight, not woofy just to vibrate the walls. Try some DTS or DD 5.1 concert videos, and you will know exactly what I mean. At +/- $400 bucks or so, unbelievable value, and as bonus, has a nice small footprint to easily position.

This subwoofer is made to produce QUALITY sound. Some reviews here and elsewhere complain that it does not pump out high amounts of booming base.
This is not a car sub. It is a home theater sub. It produces very clean and tight base, at respectable levels, even when playing action movies.
I much rather have realistic base than simply a big box that pumps out low frequency vibration.
I've tested many subs, and for this price point, you cannot get better quality.
That said, if you have a very large room, you may have to turn the volume up high to get the same level that cheaper subs put out.
Also, placement within the room is everything when it comes to subs.
Don't hesitate: If you can get this for 350-450, buy it.