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No bass from subwoofer. Bad pre-out?

 

New member
Username: Randyee

Post Number: 2
Registered: Jan-05
I had an Infinity BU-120 that fried. I have bought a JBL-E250P that is hooked to the sub-out jack on my HK500 receiver. I am using the LFE input on the sub and have the sub turned on at the receiver. The green light on the sub indicating a signal is on but I'm not able to get any bass from the sub. With my hand on the woofer you can barely feel any bass at all. Could the sub output on the receiver have gone bad when the old sub fried? How can I check the sub output on the receiver? Can I turn the sub off and use the speaker level inputs? Any help will be appreciated. Also, I had the front bookshelves, the center and satellites set to small. Thanks for any help.

Randy
 

Bronze Member
Username: Usa2k4

Post Number: 97
Registered: Dec-04
You can connect the front left & right speakers to the sub and the sub to the receiver via the speaker level in/out. You'll need to set the front left & right speakers to large and the subwoofer to off on the receiver.
 

New member
Username: Randyee

Post Number: 3
Registered: Jan-05
Thanks for the quick reply. I've been reading about doing just that. What will the effect on bass control be? Will I notice any difference between this and the LFE input?
 

Bronze Member
Username: Usa2k4

Post Number: 98
Registered: Dec-04
The LFE (Low Frequency Effect) signal is not the same as the subwoofer signal. The subwoofer signal is the low frequency signal that the bass management on the receiver has cut off from other channels that you set to small then redirect it to the subwoofer. The LFE signal is the .1 signal encoded on the DVD discs. Not all DVD's contain this signal but if it exists, it would add more excitement to the low bass in the movies such as explosions, dinosaurs' footsteps... The upper frequency of the subwoofer signal is limited by the cutoff frequency set in the bass management. By default, most Dolby Digital 5.1 receivers have the cutoff frequency at 80Hz by Dolby Labs' recommendations, and some even let you adjust this cutoff frequency. The LFE signal, on the other hand, by Dolby Labs' recommendations, would go up to 120Hz. So if you use the bass management on the receiver by setting any speakers to small and connect the sub to the receiver via the LFE/Subwoofer line-level input, you need to set the crossover control on the sub to max. If you use the bass management and set the front L&R speakers to large, and connect the sub to the receiver via speaker-level in/out, you'll need to set the crossover setting on the sub to the lowest frequency that your front L&R speakers can reproduce + 5Hz. For example, if your front L&R speakers have a frequency response of 70-20,000Hz (+/-3dB), preferrably you need to set the crossover setting on the sub to 75Hz.
 

Bronze Member
Username: Usa2k4

Post Number: 99
Registered: Dec-04
If you set the subwoofer to No and the front L&R speakers to Large, the LFE signal would be redirected to the front L&R speakers. With the front L&R speakers connected to the subwoofer, they would handle not only the front L/R signals but also the subwoofer+LFE signals so don't worry about losing any sound with that setup.
 

New member
Username: Randyee

Post Number: 4
Registered: Jan-05
The sub only has line in - no line out. Setting the speakers to large and hooking the fronts to the sub does't make a difference. How can I determine if the problem is with the sub or the receiver? The sub is brand new and indicates it is receiving a signal. Thanks.
 

New member
Username: Randyee

Post Number: 5
Registered: Jan-05
I've been testing using The Matrix. I get better base out of the Infinity RS3's than out of the sub.
 

Bronze Member
Username: Usa2k4

Post Number: 100
Registered: Dec-04
Try increasing the subwoofer level on the receiver and the loudness control on the subwoofer.

Maybe a silly question, did you remember to plug the subwoofer's power cord into the wall outlet and turn it on?
 

Silver Member
Username: Usa2k4

Post Number: 101
Registered: Dec-04
I reread you posts above and think maybe you've got a bad JBL sub. If it has a fuse, check to make sure the fuse is OK.
 

New member
Username: Randyee

Post Number: 6
Registered: Jan-05
The power is on and I get a green light indicating that the sub is receiving a signal from the receiver. I've had the volume all the way up and went into the OSD on the receiver and tried setting the sub up to +10 with no change. Is there any way to check the sub output jack on the receiver with a voltmeter?
 

New member
Username: Randyee

Post Number: 7
Registered: Jan-05
There is no fuse accessible on the back. Would it be inside? Would the power light be working as it is if I had a fuse blown? I guess I'll open the thing up and take a look. Thanks for all of your help.
 

New member
Username: Randyee

Post Number: 8
Registered: Jan-05
There is a 2A fuse inside the amplifier case that is fine. Everything inside looks and smells like new. If you or anyone can tell me how to check the pre-out for the sub I would appreciate it. Thanks again, Randy
 

Silver Member
Username: Usa2k4

Post Number: 102
Registered: Dec-04
At this point, I do not worry much about the sub out on your receiver because you've tried both line-level and hi-level input but couldn't get any bass. I just checked the E250P manual on JBL website. Try using the line-level input with the LFE toggle switch to Normal position. If you still can't get bass from the sub, I think the subwoofer's amp may be defective.
 

New member
Username: Randyee

Post Number: 9
Registered: Jan-05
I appreciate all of your help. I tried switching the LFE toggle while I had the sub on in both line-level and hi-level hook-ups. I guess my next option is writing or calling JBL.

Thanks again, Randy
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