Buzz in Bose 901 Series IV

[NormBiram]

I am new here, and not a techie. I have a buzz on one side of my 901's. Problem is I can't identify which of the 8 rear drivers it is. I have changed the surrounds some years ago. Buzz is at those typical low frequencies, and also when a singer hits that high C that always used to distort everything.

It is still there when I shut off the equalizer.

Any help for a dummy/newbie?

Thanks, Norm

 

[spicer]

I am new here, and not a techie. I have a buzz on one side of my 901's. Problem is I can't identify which of the 8 rear drivers it is. I have changed the surrounds some years ago. Buzz is at those typical low frequencies, and also when a singer hits that high C that always used to distort everything.

It is still there when I shut off the equalizer.

Any help for a dummy/newbie?

Thanks, Norm

Does it do it at low volume or only loud? With the grill off try pushing on each cone while the system is buzzing, that might reveal which driver buzzing.

 

[NormBiram]

Does it do it at low volume or only loud? With the grill off try pushing on each cone while the system is buzzing, that might reveal which driver buzzing.

Thanks for your reply. I can hear it at low volumes as well. I have removed the grill, and used a sponge to carefully dampen each cone, but couldn't isolate which one. I think I can hear that it comes from a set of four on one side (if you know what I mean that 901's have slanted rear sides with four speakers on each side). I wondered about something rattling inside the cabinet, altho that is unlikely. Is my next step to see an audio shop?

 

[spicer]

Thanks for your reply. I can hear it at low volumes as well. I have removed the grill, and used a sponge to carefully dampen each cone, but couldn't isolate which one. I think I can hear that it comes from a set of four on one side (if you know what I mean that 901's have slanted rear sides with four speakers on each side). I wondered about something rattling inside the cabinet, altho that is unlikely. Is my next step to see an audio shop?

I wouldn't dampen anything about the speaker or their cones. By touching the cone I meant finger pressure downward biasing towards one side or the other to see if the buzz changes or disappears, evidence of voice coil rub or other mechanical interference. Try that, almost a sure way to identify a bad driver. If it seems like, or is coming from one set of the four it might be cabinet related and not a driver. Everything about a speaker tries to rattle, one of the reasons assembly and cabinet is important. I can't remember, is the speaker board for each set of four a separate piece of wood, if so check to see it is secure, not at all loose. Something inside the cabinet is unlikely but not the cabinet itself. Low volume would suggest a driver. Audio shop, not yet, hopefully never. What series 901s are they? There are members here who have rebuilt 901s, hopefully they will give input.

 

[NormBiram]

Thanks for this advice about finger vs damping - new to me. I will try this, but on another day and report - late in the day here. They are Series V. The back appears to be plasticized, but may be wood below. They are glued together at the center.

 

[spicer]

Thanks for this advice about finger vs damping - new to me. I will try this, but on another day and report - late in the day here. They are Series V. The back appears to be plasticized, but may be wood below. They are glued together at the center.

Not sure the internal wiring, some drivers wired parallel depending on series, mention this because one speaker might be removed from the circuit at a time to check drivers, depends on internal wiring arrangement. At any rate try pressing on the panels to see if the buzz changes, it might be the cabinet but kind of doubt it. It is assumed it is not the electronics, something in the amplifier. Switching left and right wiring would eliminate this as a possibility, if it follows the wiring it is not the speaker. Another day works, only so many hours to a day.

 

[baco99]

You’ll likely have to take each one out and test individually.

 

[Macaroonie]

Download this https://www.nch.com.au/tonegen/index.html into your computer.
You want to enable the adjustable frequency sine wave and you need to make a connection to your amp.
From there at lowish volume you can progress through the frequency range step by step. You will find that the buzz will make itself apparent and from there you can use a kitchen towel tube to find the guilty driver.

 

[freQ(*)Oddio]

Sounds to me like the driver surrounds are deteriorated , or your amp is giving up, these speakers take a lot of power to sound clean, what are you pushing them with. The rattling noise is almost always deteriorated surrounds, or under performing amp. I've never heard of a blown 901 driver, or a cabinet noise. Series iii and iv were very prone. I've replaced many surrounds and tested many amps with them.