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JBL L110 enclosure design

cool9

cool9

Super Member
Inside of cabinet is lined with thin fiberglass insulation. Speaker is ported. Fiberglass insulation does not do anything because it does not absorb sound. (Open-cell foam, mineral wool does absorb sound.) I don't know what the designer's original intention was when designing the port, enclosure, fill, etc. I'd like to find out and replace insulation with whatever material needs to be inside the cabinet for proper/optimum performance. (ie I don't know if sound inside was meant to be absorbed or diffused, etc.) Ideas?

This Wikipedia page gives some details about resonance inside a bass reflex system - http://en.wikipedia.org/wiki/Bass_reflex

fyi: The L110 bass could use improvement. It can easily get out of control on some CDs and maybe changing out the fill could change the sound. I'm just experimenting and gathering information at this point. I can live with the bass as it is, I really love these speakers.
 
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Role of insulation is to cut down on high frequencey reflections. Ideally bass reflex enclosures should have no insulation. Normal practice is to have thin layer at cabinet boundaries. (The frequencies of importance to bass reflex cabinet are longer than the cabinet dimensions, and volumes are the primary concerns.)
 
So if the bass gets too boomy (and overpowering other drivers) what options do I have? Is it a speaker issue or room issue? I ask because the bass can sound this way when I'm standing close to it (ie trying to avoid first reflecting waves). I am also going to make some acoustic panels to improve room.
 
I think those speakers should have a smooth bass response, not boomy. They are well-regarded for their accuracy.

I would look at getting them away from the floors and corners, checking your loudness and bass controls, checking any feedback or isolation issues on any turntable you're using, checking the surrounds on the woofers (if they're dying the woofers may not be properly damped), and remember that you should be looking for good sound from your preferred listening position, not up close.

... I dunno what else. But others may have some ideas.
 
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They've been using fiberglass for decades & it works very well..very cost effective. Also Poly-fill is good. FOR the right amount, trial error is the onlyway to tune to your taste. The idea was to absorb any midrange from coming out the ports.
 
I have a very low ceiling (7'6") which is why I listened closer (after hearing boomy bass) to try and get a better idea of how the enclosure and bass reflex were actually performing/responding. (I refoamed both 10" woofers last Summer myself and voice coils are centered in the magnet.) On some CDs the bass response is very smooth and on high level CDs it can be boomy so I'll decrease the amp bass control and bass becomes smooth again. Going to add ceiling acoustic panels soon. Guitars scream with this speaker and drums get very realistic at high volume.

(Midrange and tweeter are both self-enclosed. And I have wall behind speakers and the opposing wall insulated with R30 6" fiberglass because old house is not insulated. I added inside insulation because I burn too much oil. Room is 13x15x7.5.)

Thanks very much for your knowledge/info.
 
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You might consider a few things:

1. Use a low pass filter, something along the lines of 40 hz or less. With some material, there is some very low frequency signal that ported speakers just don't like handling - those speakers will be playing in the unloaded below resonance area where the woofer will be flapping but not giving you much output. This can muddy the system a lot.

2. Placement as mentioned above is key and you might have to put some bass traps in the corners if your room somehow has a lot of positive reinforcement nodes.

3. As an experiment, you might also try plugging the port with a large rolled up sock or towel (or Zilch plug, google it or search for it on AK), essentially turning the speaker in to an acoustic suspension unit. Some like the bass output of JBL's better like this.

4. Finally, some feel recapping may improve the overall sound more.

fiberglass is useful and efficient for its intended purpose in a speaker, and that's how it was designed. You can do a lot of DIY experimentation with other material or more materials too.
 
If you have a loudness control on your preamp or receiver turn it off. The loudness switch in the on position can cause boomy bass at moderate to high volume levels. The L110 is not a boomy bass speaker system. Check out the system information link:

http://www.audioheritage.org/vbulletin/showthread.php?4552-L110

The sock or Zilch plug in the port works for the L100 not for the L110. The L110 Le111A woofer is quite well behaved and the L110A LE111H woofer is better behaved than the LE111A.

I suggest moving the speakers away from the walls and the corners and also get them up off the floor so that the tweeter and midranger are near ear level.

Larry
 
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The L110's were never know for out of control bass. There must be some other factors to you hearing this. Maybe source or room boundary issues? Also, the L110 10" driver had an extremely potent magnet structure, controlled quite nicely.
 
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