View Full Version : JBL L8400 listening thoughts


psujohny
02-12-08, 03:54 PM
Just recieved a pair of Cherry JBL L8400's won on ebay from Harmon Audio for around 350.00 a piece ( orginal retail for this 12 inch 600 watt sealed sub is 1099.00 ).
Opening them up I was blown away by the beauty of these subs, the cherry veneer and styling is very classy ( 15 1/2 x 15 1/2 x15 1/2 ) is the dimensions and they weigh around 60 lbs each. They match perfectly to my Polk RTI 12's that are also in Cherry. Auto detech is the only mode these have aside from the main power on switch on the back. I like the little blue and red light on the top of the sub that indicated whether there awake or in sleep mode. The silver feet and silver woofer also perfectly match the Polks.

Now, I previously had a HSU vtf-ho with turbo in this room ( before that I had a couple of James Cinema subs ) Ive owned various SVS tube subs in the past. My listening preference is 70 % HT and 30 % music, and Ill just be upfront, Ive always seemed to have better luck with sealed sub designs.
My room is only 11X15X8 and rectangular. H/K 745 drives all my speakers currently and does a very nice job of eq-ing the subs ( it can eq 2 lfe subs independently ).

The HSU went very low down to 14 hz and had plenty of spls in my room, but it seems to lack the strong mid range punch that I lust after. I dont know but it seemed bottom heavy and a bit chuffy in my small room ( I do have acoustical panels and some home made bass traps set up ) I played with moving it around the room/ phase controls, running bass sine waves etc., but still wasnt entirely happy.

I set up the pair of l8400's with one just to the inside of the left and one just inside ther right tower ( all up front ). Level matched them and then set my towers on 60 hz. Ran the Auto eq of the H/K.
Listening first to stereo with the sub engaged . Frist up was Steeley Dan, The l8400's are very well controlled subs and blended perfectly with my towers, the bass seemed to hit harder then you'd think a pair of12 inch sealed sub would hit but at the same time they never called attention to themselves. Lower volume lstening was superb so I cranked the volume up and the jbls didnt seem to mind at all. I put on a bunch of other cd's like Blues travellers, zz top, bob segar, Madonna, Master and commander music track, Diana Krall, herbie hancok. What I noticed was that the bass was smoother then I had with the hsu, each bass note could easily be picked out ( no one notey bass here ) and when it hits it leaves just as quickly which is exactly what I was looking for. Very happy with a thumbs up on music but I was concerned if they could hang for HT.
So, I put on some moveis with alot of music bass first ( like the fast and furious, Gladiator ) to see how it would handle it. NO problem, hit hard and had a very punchy quality that could be felt in the chest, music track was nice and in Gladiator in the scene where the tigers are roaring it stood up , the roars of the tigers was surprisingly viseral ( favorite demo scene of mine ). Cranked it up and didnt hear any audible distortion. Ok, so it does that I thougt, now lets move to some bass heavy lower hz movies.
Put in Black Hawk down, The Haunting, U-571, Jurassic Park, Finding Nemo.
the first thing I noticed was this little subs seemed to be digging deeper then they should, the chopper blades was inpresively reproduced, Dinasaur footsteps, depth charges .. Dam.
So I cranked up the volume to insanely high levels ( -5 db of reference ) I normally would only demo at this volume and not actually watch the entire movie. I started to hear them them break up and distort somewhat and the woofers where really moving almost violently ( the hsu could handle - 5db without any audible effects ) so I backed them back down to around -8 of reference and all was well. So, Id finally found the limitation of the jbls..They cant play to extreme reference levels, I wonder what 12 inch sealed subs could..probably not many.
I was curious as to how low they actually went because it seemed in demoing that they went pretty dog gone low. I got out my radio shack meter and decided to run some bass test tones. The pair went down flat to 20 hz in my room with ZERO rolloff , I do have some room gain but none the less impressive ( same as my pair of 15 inch sealed James Cinema subs)... They dropped quickly after that, -9 db at 18 hertz. Together the response was smoother then the one HSU ( Id assume this would be the case anyway ). In the end I would rather have the two l8400's then the one hsu vtf-ho with turbo even though the hsu goes lower and has more spls, the 8400's in my room anyway, just flat out sound more to my liking . Oh, I should mention the jbl pair was hitting around 106 db overall ,whereas the hsu ( corner loaded ) could hit around 109 db in my room.

All in All, I love these subs... I wish craigsub or somebody else would have a shootout with the svs sb12 and ufw12's.. The l8400 actually weighs 18 lbs more the the svs sb12, 1 1/2 inches larger in each direction and has a 600 watt amp compared to the 425 watts of the svs, they both have very nice finishes and looks. Maybe Im crazy but I think it would be a good shootout.

I do have a dilema though, in between getting these I ran into a deal that was to good to pass up on a Fathom F112 .. It will be here Thursday. I was thinking of trying to integrate the 3 subs ? .. as I would hate to send the 8400's back to Harmon Audio ...because of the excellant performance/ looks you get for the money, and price of shipping em back..but Im afraid of trying to integrate 3 subs ( with 2 different brands )... Any suggestions would be welcome :)

Likvid
02-12-08, 04:13 PM
Thanks for the input, i was looking at this sub earlier this month and posted about it here on the forum but didn't get any much response on how good or bad it was but you clearly shown that the sub is excellent for it's value.

Spezzy
02-12-08, 09:19 PM
Great review.
Curious as to know if you are using Y-Splitters for the inputs.
For this particular sub (the only that I know of) the amp section has the two separate inputs and does not take full advantage of all amplifier power unless using both inputs.

I would try putting the F112 mid wall somewhere or next to your listening position.

psujohny
02-12-08, 09:29 PM
Great review.
Curious as to know if you are using Y-Splitters for the inputs.
For this particular sub (the only that I know of) the amp section has the two separate inputs and does not take full advantage of all amplifier power unless using both inputs

Thanks, and yes the jbl actually came packed with Y splitters and yes I am using em.

I would try putting the F112 mid wall somewhere or next to your listening position.

I was actually contemplating putting the fathom in the back of my room behind my couch with the l8400's up front ...Mid wall may be do-able as well

pdadi
02-12-08, 09:45 PM
This may be great for music since it is sealed. I doubt how it can beat comparable 12 inch
ported subs which have bigger enclosures. For four bills this might be a good deal.

kuma1
02-12-08, 10:12 PM
Nice to hear that I also made a good purchase:) I received mine yesterday from Harmon Audio. Unfortunately I was very disappointed. No matter how I tried to configure it, it was just very weak sounding. As this is my first sub it took me awhile to realize that the sub had issues. The good news is that with one phone call, which required no waiting, I was speaking to JBL support and they gave me some suggestions on setup. I tried them and the sub was still not performing correctly. I called the support person back and JBL is shipping me a new amp along with a shipping label so that I can return the old amp.

Also, prior to purchase, I was investigating the functions of this sub and realized that auto-sense was not listed on any spec sheets. Given the msrp of this sub I found it hard to believe. Again, with one phone call I spoke with a technical person who does documentation. He researched and verified that despite what the spec sheets and Owners Manual say, it does have auto-sense. He called me back and said he will write an Owner Manuals addendum about auto-sense and the "Y" cable which is now included. Lastly, this person, insolicited, sent me the final version of the addendum.

So, despite my sub not working, I feel very good about my L8400 purchase because of the posotive experiences with JBL.

psujohny
02-13-08, 05:31 AM
Good to hear that JBL is stepping up on your issues. When you say weak, can you describe exactly what was going on ? What is the size of your room, Where was the volume control set at and how low (sound wise) was it and what is your recievers crossover set at ? ...This sub ,you said is your first sub so Im wondering if you have some weird nulls going on or something
The jbl does need a few hours of pounding on before the stiff woofer starts breaking in for starters.

This may be great for music since it is sealed. I doubt how it can beat comparable 12 inch
ported subs which have bigger enclosures. For four bills this might be a good deal.

Well, if you mean Louder when you say "beat" then yes, there are other 12 inch ported subs for the same price that will make boom boom louder spls Im sure...maybe something along the lines of say a cheap cervin vega or the like. If all one is after is the Loudest spls for strictly HT for the cheapest price then the jbl aint for them imo.

kuma1
02-13-08, 10:57 AM
Good to hear that JBL is stepping up on your issues. When you say weak, can you describe exactly what was going on ? What is the size of your room, Where was the volume control set at and how low (sound wise) was it and what is your recievers crossover set at ? ...This sub ,you said is your first sub so Im wondering if you have some weird nulls going on or something
The jbl does need a few hours of pounding on before the stiff woofer starts breaking in for starters.


I have a new Denon receiver so it took sometime understanding the OSD and setup options for the sub. Hence, it took me awhile to realize it was the sub malfunctioning and not my configuration. I tried everything - fronts=small, sub=yes, xover 60,80 and 100hz, increased the db on the sub out port, LFE only, sub volume... Im now a master at sub confugration and can do it with my eyes closed! lol

By weak I mean it was not loud - my little PC sub sounded almost better - seriously. I tried differeent cables, Denon setup options... then after speaking with jbl support I attached the sub directly out of the analog ports on my CD player. Even tried analog audio ports on my TV - sub just wasnt doing much...

My room is large, 24x16x8, but the tv sitting area is more like 16x12x8 - a very open floor plan that is open to the kitchen. Im not into playing things at extremely high levels - except music from time to time:) If I do get into high volume HT, I may consider buying another 8400 per your experience.

I will let you know how the new amp turns out.

mather
02-13-08, 11:13 AM
I think you're finding that multiple subs especially of the same model definitely helps smooth things out. With the F112 on the way, I hope you can test F112 individually and also with both JBLs, like you said, integrating multiple subs, when there are different ones can be difficult. Come back and let us know how they blend/compare.

psujohny
02-15-08, 08:03 AM
Well I got the fathom F112 in and set up last and it is all that, I dont need 3 subs.
Hate to send these 2 jbl subs back to Harmon Audio but I just dont need them.

If anybody is in Northern Va. and wants to buy them Id sell them for what I paid 325.00 each, save yourself the trouble of having to win an ebay bid ( and the 70.00 fee Harman charges for shipping each one of them.) Id probably ship them to somebody if they want to pay shipping ( 40.00 each should cover it )

JasonWeaver
04-08-08, 06:48 PM
Hey John, are they still for sale? Let me know, and thanks.
Jason W.