Anemic bass from L300's

[colorbars]

HI there. I have looked through the forums for a thread addressing my particular problem and did not find one so I am posting this here.

I have 4 sets of JBL speakers - 2 pairs of 4208's, 1 pair 4311B, and 1 pair L300 Summits.

The problem I am having is with the L300's. I am running these speakers on an SAE 2900 preamp and a SAE 2400L power amp (200W pc). I am not getting nearly the bass output from the speakers with all tone controls at flat that I think I should be hearing.

I have tested with another known good (NAD) power amp as a friend suggested the caps may be drying out in the SAE power amp. He runs his L300's on either an SAE 2400 or an SAE A501 and his sound great.

My room is insulated and sheetrocked. The floor is solid cement covered by underlayment and your standard fake wood flooring.

I have the L300's sitting on their built in stands (rectangle box of particle wood with small feet on the corners).

Anyone have any idea what I might look for or try? Do I need to use floor spikes? I saw a thread about spikes with differing opinions about their actual value in improving sound.

When I goose the low frequencies at the preamp, I start to hear decent bass that I think should be present with the tone controls flat. I know the woofs can put it out and they are the correct drivers in both speakers (I bought them used so I checked first.)

Could it be components in the crossovers? Both of them?

I checked speaer cables for in-phase wiring and its all good. I have not tried to reverse the phase yet.

Its just a mystery to me why this isn't putting out more low end with tone all at flat.

Thanks for any and all info! I hope to get my speakers and system posted here at some point now that I have a new listening room.

Best regards,

Jim K.

[toddalin]

Are the foam surrounds still good without cracks or holes?

[pioneer]

A few things I found with my L300's that helped the bass.
1: I have them three feet from the walls, how far are yours?
2: I raised mine up about three inches off the ground seemed minor but it worked.
those I would try first and are easy to do if you have the space.
The 3rd and more difficult is to bi-amp them, I have and now run 500 watts into the woofers that was the biggest improvement.

[tarior]

Push in the "Loudness" button.:D

[Zilch]

Swap speakers with your friend.... :yes:

[BMWCCA]

Swap speakers with your friend.... :yes:

Good suggestion. Seriously. I was gonna say go out and buy some $200 L7s to compare them. If the 12" L7s give you much deeper bass, your L300s have a problem.

Too bad you're so far away. I have a spare pair of L7s and I'd be willing to swap you, for the sake of comparison, science, and the spirit of investigation. :applaud:

[colorbars]

Are the foam surrounds still good without cracks or holes?


Yes, the surrounds are fine.

[colorbars]

A few things I found with my L300's that helped the bass.
1: I have them three feet from the walls, how far are yours?
2: I raised mine up about three inches off the ground seemed minor but it worked.
those I would try first and are easy to do if you have the space.
The 3rd and more difficult is to bi-amp them, I have and now run 500 watts into the woofers that was the biggest improvement.

Mine are not three feet from the walls. When you raised them, what did you use to do this?

Bi-amping has been a consideration, but finances dictate I wait on that.

[colorbars]

Push in the "Loudness" button.:D

While you may have been joking, its definitely a factor to consider. In my case I have the loudness button on.

Thanks though!:)

[colorbars]

Good suggestion. Seriously. I was gonna say go out and buy some $200 L7s to compare them. If the 12" L7s give you much deeper bass, your L300s have a problem.

Too bad you're so far away. I have a spare pair of L7s and I'd be willing to swap you, for the sake of comparison, science, and the spirit of investigation. :applaud:

I won't ever part with my Summits. Thanks for the offer though. :)

My friend is 400 miles away so trying his is not an option. However, I have a near mint pair of 4311b's and I will try them. They have always kicked ass.

Thanks!

[colorbars]

HI there. I have looked through the forums for a thread addressing my particular problem and did not find one so I am posting this here.

I have 4 sets of JBL speakers - 2 pairs of 4208's, 1 pair 4311B, and 1 pair L300 Summits.

The problem I am having is with the L300's.

Best regards,

Jim K.


Thanks for all the tips and information. One thing I came across is a guy who had his L300's crossover caps replaced with new ones of the same valu and quality.

Maybe that is something to consider.

If anyone else has any more ideas, tips or information please post.

And thanks again for the info I have received so far.

Best regards,

Jim K.

[pioneer]

Mine are not three feet from the walls. When you raised them, what did you use to do this?

Bi-amping has been a consideration, but finances dictate I wait on that.

At first I used 2x4's to get an idea of what height worked best for both the bass and getting the 077's to a better listening position level with my ears in a seating position. Once I got that I bought movers dollies ( cheap 15 bucks)that were very close to that height, it also allows me to easily move the speakers in the room to get the best spot away from the wall ( moving these are not easy the dollies make it a breeze and there are times in my living room that I would like to move them out of the way) the dollies are not a thing of beauty but the ones I got are carpeted and can easily be made to look respectable.

Bi-amping is not cheap but it works very well it was by far the best improvement, others have disconnected the woofers from the internal network and run the woofers directly to a large amp and run the mids and highs through a separate amp keeping the original network not sure of the details but you can find them doing a search. I had an external network made and use an Ashly xr1001 as an active crossover.

[BMWCCA]

Bi-amping is not cheap but it works very well it was by far the best improvement...There really shouldn't be an obviously noticeable LF deficiency in an L300 due to amplification if the owner is using a 200wpc amp with the built-in passive crossover. When we ran the 4333 vs. L7 event here in VA, John's 4333s and my L7s were both powered by Adcom 2535 amps with only 60wpc. Now I use a Crown PS400 at home (about 200wpc) but at no time did we find the 4333 or the L7 particularly deficient on the Adcoms because of lack of power. We did identify other factors that might have improved the LF response (more power, updated woofers) but there was no glaring deficiency. I think you're only going to be able to make a valid comparison or diagnosis by bringing in another pair of speakers to try. Preferably some you are familiar with how they sound from another room in your home.

[edgewound]

Thanks for all the tips and information. One thing I came across is a guy who had his L300's crossover caps replaced with new ones of the same valu and quality.

Maybe that is something to consider.

If anyone else has any more ideas, tips or information please post.

And thanks again for the info I have received so far.

Best regards,

Jim K.

Due to the age of your L300's and it's 136A woofers with alnico magnets, there's a very good chance that the magnets have lost a good amount of magnetic charge...maybe down as much as 30%.

A recone and recharge of the magnets will basically restore them to as new condition.

As an example, I recently repaired a pair of 136A's for a forum member. The flux in the gap measured approximately .8T, when they should be 1.2T. A recharge of the magnets took care of that problem. No amount of EQ and capacitor swapping will fix the problem when the motor is weak.

Hope that info helps.

[tarior]

While you may have been joking, its definitely a factor to consider. In my case I have the loudness button on.

Thanks though!:)
I nearly always use my loudness button.
Have the woofers been out of the cabinets? Is it possible that one got hooked up backwards by mistake?

[BMWCCA]

I nearly always use my loudness button.
Have the woofers been out of the cabinets? Is it possible that one got hooked up backwards by mistake?Hopefully your system's "loudness" button is somehow keyed to the volume pot. "Loudness" is not intended to be used as a room or speaker EQ except to compensate for the Fletcher-Munson hearing characteristic which defines how we can't hear either highs or lows as well at low volume as we can at higher levels. In the early days pre-amps often had variable "loudness" controls that tracked the Fletcher-Munson curve just for that purpose. If you find the button makes a descernible difference at loud levels, it's likely not a "loudness" control in the true Fletcher-Munson sense. You might as well just turn up your bass and treble controls . . . for those of you who have those.

[tarior]

Hopefully your system's "loudness" button is somehow keyed to the volume pot. "Loudness" is not intended to be used as a room or speaker EQ except to compensate for the Fletcher-Munson hearing characteristic which defines how we can't hear either highs or lows as well at low volume as we can at higher levels. In the early days pre-amps often had variable "loudness" controls that tracked the Fletcher-Munson curve just for that purpose. If you find the button makes a descernible difference at loud levels, it's likely not a "loudness" control in the true Fletcher-Munson sense. You might as well just turn up your bass and treble controls . . . for those of you who have those.

AFAIK, just about every receiver/preamp that has a loudness button also has taps on the volume pot that roll off the loudness effect so that it is completely out of circuit by about half throttle.

[BMWCCA]

AFAIK, just about every receiver/preamp that has a loudness button also has taps on the volume pot that roll off the loudness effect so that it is completely out of circuit by about half throttle.I wouldn't count on it. But it's easy enough to test it. I have nothing with a button, only variable (McIntosh C-20) or nothing (Soundcraftsmen Pro-Control-Four and DX4200).

[tarior]

I wouldn't count on it. But it's easy enough to test it. I have nothing with a button, only variable (McIntosh C-20) or nothing (Soundcraftsmen Pro-Control-Four and DX4200).
Hmmmm....mebbee I'll have to throw my Adcom GTP 500 on the bench and measure it.. just out of curiosity.
I know for certain that G-series Sansui receivers and most Marantz receivers from BITD, do have loudness taps on the volume pots, and one can tell that loudness is out of circuit by the time the volume knob is at 12 o' clock.

[LE15-Thumper]

Pop the woofers out and check the phasing just to rule it out, even with weak magnets, having the loudness compensation on should make them thump pretty good.

And FWIW, in an audio repair career that approaches 30 years, I have yet to see a loudness circuit that is NOT tapped off the VC to give a lessening effect as volume is increased. Loudness Comp. was invented to compensate for "non-linearities" in human hearing at low volumes.

[Beowulf57]

You could also try using this xls file to check your room for problem modes. Enter your room dimensions and seating position and have a look at the problem frequencies (line 27).

[toddalin]

Pop the woofers out and check the phasing just to rule it out,

Sounds like a real effort and could more easily be accomplished just by putting a 1.5 volt battery across the input terminals and watching which way the woofer moves.

[LE15-Thumper]

Sounds like a real effort and could more easily be accomplished just by putting a 1.5 volt battery across the input terminals and watching which way the woofer moves.


Yes, a very good idea as well. They should both move the same way (in/out) using the same polartiy on each driver.

Popping the drivers out would give him a chance to peek around and see the drivers and such, maybe record some serial numbers for posterity.

[colorbars]

Thanks to everyone for all the info. I will look into the maget charging. They had the woofers just reconed professionally before selling to me. It was by an authorized JBL repair shop. The recones look very solid.

Now comes the part about speakers being out of the cabs at any time. it funny, but I got to thinking about this one as well later on. I had one of the cabs go dead not long after I got them. I finally opened up the cabinet rear panel and found one of the leads had slipped off the metal peg that goes to the post on the back of the cabinet.

Since it was only one of the leads, I reconnected it. I got to thinking maybe the previous owners had had this problem or the jbl tech just hooked them up wrong after the recone, to the posts.

Either way, I reversed the leads on one end of the speaker cable for one of the cabinets. This seemed to do the trick. I have noticed increased bass that makes more sense to my ears from what I have heard through other L300's. I have been playing discs with MP3s so the bass may not be as strong anyway, so tonight I am going to put them through their paces with full bandwidth audio CD's. So far, since the reveral of a couple of leads, I am encouraged.

Its funny how almost every time it turns out to the simplest thing.

If any thing changes I will update this thread. But again, HUGE thanks to all of you who supplied information.

Best regards,

Jim K.

[Fred Sanford]

Well, now the next thing to do is to see if the woofers are in the correct phase in relation to the mids/highs. You might have "corrected" the one that was actually correct in the first place, and now have them both out of phase in relation with the mids/highs. Check the JBL crossover diagram for your particular crossover model.

Not as dramatic a difference as the bass issues you've been hearing, but not difficult to make actually "correct".

je