JBL L100t3 - Mod Question - Re Boomy Bass

[dkalsi]

Just picked up a pair of JBL L100t3 over the weekend. While the speakers mids/highs sound nice, I'm not sure I'm a fan of the bass.

To be clear, they are not lacking in bass; in fact, there is insane amount of bass.

Unfortunately, its not the punchy musical bass I was hoping for - its the really pronounced deep base. I understand it could be room dependent / placement dependent - however, even if I walk around there room, there is too much low bass and not enough mid-bass.

I could take measurements to show whats going on, but its really hard to take meaningful in-room response below 200hz.

I took a look inside the cabinet (through the port) and noticed it had no bracing. Perhaps that could help?

Any thoughts?

[RMC]

You walked the room, but did you try moving the speakers themselves? Are they located in the corners of the room or on floor with their back to the wall?

Yes, boundary placement does amplify the low frequencies (floor, back wall, corner). Just to hear it for yourself, try placing them in the middle of the room...

Richard

[RMC]

Walking the room is basically a listener placement or location initiative, not really a speaker placement step. It can be useful to hear speaker power response/dispersion pattern (finding the best spot for listener) or where you have more standing waves in the room for example.

But the real remedy in your case may be to move the boxes out of corners and/or back wall if located there, in addition to being on the floor.

Not seeing bracing through the vent isn't a guarantee there is none. It could be higher up in the cabinet as this is a "tower" type model. Opening the box (i.e. removing a driver) is the only way to know for sure.

"its the really pronounced deep base" Its unlikely cabinet resonances due to lack or insufficient bracing would generate that amount of excessive very low frequencies, unless using LOTS of input power and/or your bass tone control is defective or stuck at max. level. Touch the cabinet panels with your hand to feel if they are resonating that much.

Richard

[rdgrimes]

Any thoughts?

Placement will cure most of this, but if that's not possible then this is what EQ was invented for.

[BMWCCA]

An L7 will fix that! ;)

[dkalsi]

Placement will cure most of this, but if that's not possible then this is what EQ was invented for.


Rdgrimes,

It might come to using EQ. Sorry, I didn't mention this, but I did play around with placement as well. At the moment, the speakers are placed 44" away from the back wall and about 36" away from the side walls. I, unfortunately, don't have the ability to move them any closer in than that.

I also took a quick measurement of the speaker, with the speaker placed in the middle of the living room. The mic was place on tweeter axis, approximately 52" away from the tweeter.

Attached please find the measured response (no gating - 1/6th smoothing). I'll also try to take measurements of the speakers in their current (aforementioned) placement at the listening position.

[DavidF]

Just picked up a pair of JBL L100t3 over the weekend. While the speakers mids/highs sound nice, I'm not sure I'm a fan of the bass.

To be clear, they are not lacking in bass; in fact, there is insane amount of bass.

Unfortunately, its not the punchy musical bass I was hoping for - its the really pronounced deep base. I understand it could be room dependent / placement dependent - however, even if I walk around there room, there is too much low bass and not enough mid-bass.

I could take measurements to show whats going on, but its really hard to take meaningful in-room response below 200hz.

I took a look inside the cabinet (through the port) and noticed it had no bracing. Perhaps that could help?

Any thoughts?

Appears to be all about placement and room nodes. Bracing, port size etc. are not going to solve the issue. Equalization can help but only at one position.

What model system were you listening to before in comparison?

[dkalsi]

Appears to be all about placement and room nodes. Bracing, port size etc. are not going to solve the issue. Equalization can help but only at one position.

What model system were you listening to before in comparison?


David,

I've had a bunch of different systems in the same space, including my JBL 4345 studio monitors. Maybe I try taking outside measurements for them. See if removing the room helps any.

Thanks,
D

[RMC]

I'll also try to take measurements of the speakers in their current (aforementioned) placement at the listening position.

It would be interesting to compare response curves but with same distance from tweeter axis 52" away as the other measurement, instead of listening position. Some room gain should be seen in the lower bass range compared to middle of room where there's peak at 85 hz followed by a sag (and falling lower freq response)? That peak MAY end-up being lower with more output downwards. Plus another try with box to back wall (even more room gain)? Then from listening position. To compare curves from different placement scenarios and listener position.

Richard

[RMC]

In my last post # 9, I forgot to mention the why of my alternative speaker placement suggestions. In chapter "Aspects of the Home Listening Environment", section "Listening Room Boundary Conditions", John Eargle of JBL (see note # 1 below) explains with graphs some of the 1974 work of Roy Allison, the "Bible" on this Room Boundary matter (see note # 2 below):

"The picture is a complex one, and Allison has worked out several examples ..."

"In general, the closer a LF driver can be brought to a boundary, or set of boundaries, the smoother the response will be."

This may sound contradictory at first sight since each boundary increases LF output. However, the LF output may be increased, on the falling response below the huge 85 hz peak you measured, but should also generate less ripple higher-up such as the 85 hz peak followed by a sag in response you had on your graph...

If still unsatisfied with the result, though its a "tower" type of enclosure, you may even try to lift the boxes off the floor on a stand, but with their back to the back wall. I'd try numerous single or double boundary options, measure and decide which suits you best. Three boundaries (corner) may well be too much.

Then, If lower bass output still sounds offensive to you, you may EQ it, as rdgrimes mentioned, negatively to remove the excess from room gain, which will give you increased woofer LF input capability and more amp headroom as a bonus...

Richard

(1) John M. Eargle, Loudspeaker Handbook, Chapman & Hall, 1997, P. 291-293.

(2) Roy Allison, The Influence of Room Boundaries on Loudspeaker Power Output, JAES, Vol. 22, No. 5, (June 1974).

[DavidF]

David,

I've had a bunch of different systems in the same space, including my JBL 4345 studio monitors. Maybe I try taking outside measurements for them. See if removing the room helps any.

Thanks,
D

Sounds like the other models haven't been as much a problem for you, then, in that same position. I can understand why you are looking at the L100t with a bit of a frown. Short of the siders on the woofers being shot I can't think why such a difference. Still, I have LE14H-1 drivers that can set up all kinds of bass issues in the room where a pair of Klipsch Forte's in the exact same position actually work well.

[rusty jefferson]

Dhar,

Have you tried lifting them off the floor? 12"-18" to start.

[dkalsi]

......Short of the siders on the woofers being shot I can't think why such a difference......

David,

Do you have any suggestions oh how I can test them? The seem to sound fine. I even took near field measurements and they have a shockingly smooth response from 40hz-800hz, with THD between .14% - .25%, which I believe is pretty clean for this part of the frequency response.


Rusty - no, I have not tired lifting them off the group just yet. Its a good ideal - I'll try it and get back to you.

[dkalsi]

Dhar,

Have you tried lifting them off the floor? 12"-18" to start.


Jim,

Lifting the speakers off the ground made a huge difference. Much cleaner and less boomy bass.

All that being said, I sold the speakers cheap on local CL. Shared my experience with the new buyer and suggested he too lifts them off the ground 12" - 18".

Thanks everyone.

D

[grumpy]

IIRC, an optional stand was available for the L100t(3 also?) that raises them up by 6-8” (guessing... it has been a long time)... seems like someone here was thinking about fabbing a reproduction of same not long ago.

Glad they found a new home. They still beat a lot of what’s available new at a similar price point.

[DavidF]

Goes to show that one thing is constant- every one's listening configuration is going to be different no matter how they were originally voiced by the maker.

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