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Harman Kardon SB 16 Subwoofer Low Volume

MrMorgan

Apr 18, 2020
2
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Apr 18, 2020
Messages
2
Hi all,

I am having low volume issues with my hand-me-down Harman Kardon SB 16 subwoofer. It doesn't produce an acceptable volume level as compared to the soundbar.

I have to turn the volume knob all the way up to get nearly an acceptable volume. The quality of the sound is good, it doesn't sound weird at all, but I know it should sound a lot louder (especially for its monster size).

I'm using the optical cable from my Xbox One S straight to the soundbar.

What I've tried so far:

  • Moving it close to the soundbar
  • Moving it in the corner of the room
  • Trying all the wireless channels
  • Plugging it in straight to the wall
  • Smacking it and shaking it around (to see if something might be loose)
But nothing has worked.

Can anybody help? Thank you.
 

Charles Steinmetz Jr.

Jan 8, 2021
4
Joined
Jan 8, 2021
Messages
4
Mr. Morgan, I have had an experience with the SB16. Let me describe the way my sub is acting and tell me if this sounds familiar or similar to your problem.
The soundbar itself works and sounds great. The sub operates in standby and powers up when the bar powers up. But the volume from the sub is so low that one must lean close to be sure it is working. It used to shake the sofa. It has been like that for quite a while, but I recently located a manual with diagrams so am attempting to fix it. I currently have my sub disassembled and have been testing today. Looks like the power amp, I think the chip has the actual output transistors on it and it is probably cooked.
I want to find a replacement power amp if I can because to replace the entire sub means paying shipping on the heavy bits that are just fine. The H-K number of the power amp is 051-A05264B-E.
 

WHONOES

May 20, 2017
1,217
Joined
May 20, 2017
Messages
1,217
Have you got the Trim Switch in the correct position? See page 4 of the manual.
 

Charles Steinmetz Jr.

Jan 8, 2021
4
Joined
Jan 8, 2021
Messages
4
Thanks for the suggestion, WHONOES. I checked, and the trim was set to 3. Tried moving it, and the soundbar volume changed. Seemed like the sub volume changed along with the bar, but hard to tell. I had to move away from the sub to changed the switch. Sub was still working but hard to say if it changed. It was never very loud. At no time, even with the soundbar at a very loud setting, was there any visible movement of the subwoofer cone. One must place an ear close to the sub to confirm it is working. That is not how it was when new. I plan to test the speaker itself today by hooking it up to the output of my 100w Yamaha stereo amp. I will post results of that later, after I get dressed and go out into the cold to retrieve my test leads from the barn. I will also take some measurements of the speaker lead signal. I don't know what to look for on the DVOM, but can compare performance.
 

Charles Steinmetz Jr.

Jan 8, 2021
4
Joined
Jan 8, 2021
Messages
4
Speaker test was puzzling. No sound from H-K speaker connected to stereo amp (not sure why), but good bass from stereo speaker connected to H-K sub power amp. Sub volume definitely rises and falls with soundbar trim selection. Then I connected the H-K speaker to the sub amp and discovered that the H-K speaker cone moves visibly and volume is louder with speaker oriented facing sideways, but buzzy sounding. Still no visible motion of cone with speaker oriented vertically. I am beginning to suspect the speaker itself. Cost of cheap replacement $40, good one $80 and up. With uncertainty of my diagnosis, the cost is enough to make me think of replacing the whole sub rather than trying to fix it. I wonder if other models or brands of wireless subs use the same 4 channel frequencies. Maybe a bigger sub would connect with my soundbar? Or perhaps Mrs. is right, I am deaf.
 

WHONOES

May 20, 2017
1,217
Joined
May 20, 2017
Messages
1,217
Sounds as if the speaker coil could be off centre which would make it sound a bit scratchy. If so, then that's the end of that. You can check by taking the speaker grille of and gently push on the voice coil. It will be apparent if it is off centre.
 

Charles Steinmetz Jr.

Jan 8, 2021
4
Joined
Jan 8, 2021
Messages
4
As the last step in the diagnostic chart sometimes says, "substitute a known good part...". I currently have the H-K sub electronics powering a 15" PA speaker w/2" voice coil borrowed from a musician friend. Sounds good on regular TV channels, impressive bass on movie and music channels. Had a worrisome hum any time the unit was on, but it went away when I routed the LED lead away from the preamp. It looks like a new speaker will fix it, but I need to let Mrs. spend an evening listening to the test setup to get her verdict.
 
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