L-250...

[lpd]

I have a pair of JBL L-250's and am wondering if anyone can advise me on how to optimise bass from these cabinets. Right now I have them 17" from the back wall to the back of the cabinet and about 30 " from the side wall. Distance between them is 8 feet. Am I doing something wrong with my placement ....the bass is really weak in presence and no matter where I place them it doesn't seem to improve.

Any input is appreciated.

[Ken Andrew]

Have you confirmed both speakers are wired in phase. Its easy for someone to stuff around with your connecting wires and put it on reversed. Check by playing a CD with obvious bass loud and reverse the red and black speaker leads on one speaker. If the bass improves then this reversal is the correct wiring. If the bass gets even worse, then phase cancellation is not your problem.

[Jakob]

My 250 ti's are positioned like this: 8" from back wall and about the same from side wall with a little toe in. Distance between speakers: 9 feet. By moving the speaker closer to the walls You should get more, but less accurate bass, I think. The bass response is also very depending on Your listening room (for example if the floor is made out of wood or concrete).

You don't mention for how long You've had them, and what kind of speakers You had before. I too thought my 250 ti's had little bass when I just had bought them. In my case, that was because I was used to my L150's and they didn't have that balance between the lows and highs that the 250's have. Less bass but better bass.

If nothing is wrong with Your setup, You can always build a pair of 18" subs, thats what I did!

[jblnut]

When I first got my L250's I thought the same - "where's the bass" ? It just didn't seem like what I was expecting. The first thing I did was to use the bars on the back to bring the level of the other drivers down - effectively bringing up the level of the bass (le14). The 14" driver is the only one not affected by the bars. Having done that I went back through my recordings and found out that the L250 does indeed have great bass. But it's accurate bass and not 100hz boom that many people equate with bass (not you in particular, just in general). It goes *very* low with the right recording and with enough power it'll shake the house. Move them closer to the back wall and closer to the side wall too (corners) to increase the bass, or just get an EQ. You'll lose some of the voicing/imaging if you "corner" them and it might be better to just compensate electronically.

I've also noticed that where you are in the room plays a pretty big part in how the bass is perceived. If you are in the middle of the room away from the back wall, the bass will be less. Walk around the room and see what I mean while you play a song with lots of bass.

Let us know how the experiments work out...

jblnut

[lpd]

I have done some experimenting with my speakers and here's what I discovered. The room is wood suspended, and not insulated very well (which is a problem). The speakers are on a long wall 16 feet in length and 12 feet in width. The room has a jog at the 16 foot mark and is also another 8 feet in length. So in total 24 feet in length and 12 feet wide (horrible shape and some major peeks and dips). I had the speakers on granite slabs on bricks about 5 inches off of the ground. Granite is huge 3 by 3 foot 4 inch thick slabs (looks nice, but when I put the cabs back on the ground the bass appears smoother). I then checked all wiring and reversed the black with red on both cabs and the bass seems smoother and less boomy. I put them 17" from the back wall and one speaker is about 27" from side wall the other has about 6 feet to side wall (they are far enough out to avoid reflections). Bass is now improved now that I lowered them from the slabs and reversed my wiring (I was under the impression that JBL drivers are negative polarity and when I hook red with red they go in on a battery test, but in the reverse they sound better? Not sure why. I will experiment a little more, I know the problem is in the room, and I do find the bass very accurate in detail.

Thanks for the tips...

Peter

[Ken Andrew]

For the benefit of other readers, you only reverse ONE speaker lead, not both. Only 'golden ear audiophiles' check for ABSOLUTE PHASE, when you reverse both wires. I can't hear any difference when changing the absolute phase.

In general, all speakers have less bass on a solid concrete floor. The 'heave' with wooden floors is part of the experience.

L250 were clearly intended to be floor standing. Unless on carpet, the veneer, particularly on the sloping edge, is really delicate. I have mine on little trolleys to roll them out to vacuum behind. In general, with any speaker, raising tends to reduce bass, but raising does improve clarity.

Are you playing them too loud ? At high volumes, room feedback of the higher frequencies tends to overwhelm the bass and the speakers sound unbalanced. As sugested earlier, turn down the treble or install heavy furnishings, curtains, and carpet. This is less of a problem with the 250 TI. If you are exceeding 100W RMS continuously, then the speakers are too small for your needs.

I have also found some amps are a little 'bass shy', not in volume but oomph. This is never a problem until you own speakers with bottom performance like L250. Try other brands of amplifiers with which use different circuit topologies. In general, US amps have more 'grunt' than Japanese amps, but this is something which can only established by auditioning.

[lpd]

Right now I'm using a Michaelson Audio Oddyseus Integrated (rated 45 watts per channel class A and 90 AB). It is an integrated tube amp with 4 EL34's per channel. I might return to my Theshold S-150 SS amp to see what difference it makes. I'm not a huge volume fanatic, but at really low volumes the music appears "diffused" for lack of better words. I'll keep you posted.

[250timan]

Face them straight forward or very slightly toed in and listen again. Don't know why but there is a lot less bass when toed in to angle directly at the listener. Straight forward the bass is hugh.

They should be at least 3' from the back wall to help with imaging and to sound holographic.