Dynaudio BM15A hum - active monitor hum due to cheap TC Elec amplifier inside?

Mitch Manger · 27th October 2007

I just upgraded my monitors from used Event ASP8’s to used Dynaudio BM15A’s, and spent today A/Bing them before making a final decision. Although the Dynaudios sound a little better (slightly clearer soundstage, easier to locate instruments and their nuances), they have a very slight low (60Hz or somethin) hum. Both the monitors are set to +4 and have similar response curves, seem to produce similar volume levels, etc.

Eganmedia · 27th October 2007

I have 5 BM15as in my control room and they don't have a hum issue. The amps in them are actually pretty nice amps. Much better than the new II series junk.

Do the speakers hum all by themselves (nothing but AC connected)?

What kind of environment did they come from? Were they abused?

Mitch Manger · 27th October 2007

I'm glad to hear the ones in your studio don't have the hum issue.

Although I bought them off ebay, I bought them from a record label whose music I respect and enjoy, so I figured that they probably took decent care of their equipment. The speakers looked excellent upon arrival, and playback sounds great.

The record label owner told me they were used in the label's second studio, which they are now closing down, and that they have BM15As as well in the one studio they are keeping. So it was the "duplicate item"/downsizing reason for sale.

tcause · 27th October 2007

Sounds like you got yourself some ground loop...

Now I think that the design on active monitors should take care of this... (subs are usually the most susceptible... I have one sub out of 4 in our lounge/demo room that is susceptible)... but given that it don't you can do all the reading about curing ground loops and why they occur etc and good luck with that... they are mongrel things to track down and fix.

The other approach is to remove the gound pin from your IEC cables... this will probably cure it... it is technically not too good an idea and I hope that you only do this if you know your power is up to scratch and you have a tested earth leakage detector etc...

I don't know how you've gone about connecting power in your studio but if your monitor controller/desk and monitors are connected to a single outlet via a power board or conditioner this can also help...

Mitch Manger · 28th October 2007

At first, I thought that maybe the Dynaudio could be amplifying a 60Hz ground loop more strongly because it has a larger woofer and supposedly a tighter low end than the Events, which were not humming. However, besides the lack of a ground loop in another testing, I think that the fact that the hum comes more loudly from the back of the monitor cabinet is also a sign that a ground loop is not at fault, and that the problem is just very slight self-noise.

Fleaman · 28th October 2007

He's not gonna have a ground loop with nothing connected but AC. It's impossible.

Put your finger on the woofer, can you feel it vibrating? This will tell you if the hum is coming through the speaker or it's the transformer in the amp humming. If from the speaker, try playing with the amp gain....try turning the amp gain down and turning your output gain up (from what ever you are feeding them from), or vice-versa. If this doesn't help, I would think you have something wrong with your monitors or you have dirty AC that the dyna's can't clean up as well as the Events, etc.

If it's the actual amps humming (transformer hum...the back amp plate might vibrate a little too), then again I can only think of either returning/checking out another pair of the same monitors (maybe go to GC or some other showroom), or trying a AC power conditioner of some sort to clean up your AC (again, not saying that's the issue here). You could also take 'em to another house, studio, etc. to see if they hum there (maybe cleaner AC). Pluging them into another outlet in the same building will probably still give you the same AC.

asalater · 1 Week Ago

Sorry for resurrecting such an old thread.

I have that same buzzing in my BM15As. It is coming from the amp/back plate.
Dynaudio say to send them to them and they'll charge me for looking at them but that's just too expensive.

I know someone recently bought a pair and sent them back straight away.

I love these speakers but the hum/buzz ruins everything when I want to monitor at low level.

If anybody out there has the same problem, please get in touch as it seems rare and a solution would be fantastic!

Apologies for the Lazarus-like resurrection of this thread.

Cheers,
Ronan

27th October 2007	#1
Mitch Manger Gear nut Join Date: Jan 2005 Posts: 134 Thread Starter	Dynaudio BM15A hum - active monitor hum due to cheap TC Elec amplifier inside? I just upgraded my monitors from used Event ASP8’s to used Dynaudio BM15A’s, and spent today A/Bing them before making a final decision. Although the Dynaudios sound a little better (slightly clearer soundstage, easier to locate instruments and their nuances), they have a very slight low (60Hz or somethin) hum. Both the monitors are set to +4 and have similar response curves, seem to produce similar volume levels, etc.

27th October 2007	#2
Eganmedia Lives for gear Join Date: Jan 2005 Location: Burlington, Vermont USA Posts: 942	I have 5 BM15as in my control room and they don't have a hum issue. The amps in them are actually pretty nice amps. Much better than the new II series junk. Do the speakers hum all by themselves (nothing but AC connected)? What kind of environment did they come from? Were they abused? __________________ Joe Egan EMP Colchester, VT USA www.eganmedia.com "I feel more like I did when I first got here than I do now."

28th October 2007	#6
Fleaman Lives for gear Join Date: Jun 2002 Location: Los Angeles, Silverlake Posts: 3,967	He's not gonna have a ground loop with nothing connected but AC. It's impossible. Put your finger on the woofer, can you feel it vibrating? This will tell you if the hum is coming through the speaker or it's the transformer in the amp humming. If from the speaker, try playing with the amp gain....try turning the amp gain down and turning your output gain up (from what ever you are feeding them from), or vice-versa. If this doesn't help, I would think you have something wrong with your monitors or you have dirty AC that the dyna's can't clean up as well as the Events, etc. If it's the actual amps humming (transformer hum...the back amp plate might vibrate a little too), then again I can only think of either returning/checking out another pair of the same monitors (maybe go to GC or some other showroom), or trying a AC power conditioner of some sort to clean up your AC (again, not saying that's the issue here). You could also take 'em to another house, studio, etc. to see if they hum there (maybe cleaner AC). Pluging them into another outlet in the same building will probably still give you the same AC. __________________ Fleaman "The best sounding sluttiest gear of all time... is a great song" --Greg Wells "Life is too important to be taken Seriously." --Oscar Wilde

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27th October 2007	#4
tcause Gear maniac Join Date: Sep 2006 Location: Melbourne, Australia Posts: 228	Sounds like you got yourself some ground loop... Now I think that the design on active monitors should take care of this... (subs are usually the most susceptible... I have one sub out of 4 in our lounge/demo room that is susceptible)... but given that it don't you can do all the reading about curing ground loops and why they occur etc and good luck with that... they are mongrel things to track down and fix. The other approach is to remove the gound pin from your IEC cables... this will probably cure it... it is technically not too good an idea and I hope that you only do this if you know your power is up to scratch and you have a tested earth leakage detector etc... I don't know how you've gone about connecting power in your studio but if your monitor controller/desk and monitors are connected to a single outlet via a power board or conditioner this can also help...

1 Week Ago	#7
asalater Gear interested Join Date: Jan 2012 Posts: 1	Sorry for resurrecting such an old thread. I have that same buzzing in my BM15As. It is coming from the amp/back plate. Dynaudio say to send them to them and they'll charge me for looking at them but that's just too expensive. I know someone recently bought a pair and sent them back straight away. I love these speakers but the hum/buzz ruins everything when I want to monitor at low level. If anybody out there has the same problem, please get in touch as it seems rare and a solution would be fantastic! Apologies for the Lazarus-like resurrection of this thread. Cheers, Ronan