Stupid monitor question

splitrmx

There are no stupid questions, just stupid people.

I've a pair of Genelec 8040s in a room. I recently noticed that if I turn one monitor off, the level of the bass on the other monitor is a lot higher, ie the room is shaking more when I play a boomy 808 kick.

When I've got the two monitors on at the same time the bass isn't as boomy. Is this some destructive interference thing with the sound from the two speakers? (there's no subwoofer in the room)

frobisher

Sounds like a could be a phase issue. Are the speakers definitely receiving the negative and positive inputs correctly?

splitrmx

The speakers are connected to a Motu 828 mk2 via a 1/4" jack to XLR cable, so I can only assume they are receiving the negative and positive inputs correctly. Any way I could test this?

madtheory

splitrmx wrote: »

Is this some destructive interference thing with the sound from the two speakers?

That seems the most likely reason to me. It's not an electrical "phase cancellation" issue, but an acoustical one. I would verify that the same thing does not occur when you do the same thing with the speakers outdoors (i.e. as far away from any reflective surfaces as you can get) just in case it is an electronic problem.

Get a multimeter and test that the tip/ pin of the plug/ socket is connected at both ends, etc.

If all that checks out, then you need to go and build/ buy bass traps.

frobisher

splitrmx wrote: »

The speakers are connected to a Motu 828 mk2 via a 1/4" jack to XLR cable, so I can only assume they are receiving the negative and positive inputs correctly. Any way I could test this?

It could as simple as one of the internals of the cables you're using being wired pin/collar differently than the other.

i57dwun4yb1pt8

if you room is untreated then you are defo experiencing bass cancellations and peaks in it .

PaulBrewer

splitrmx wrote: »

There are no stupid questions, just stupid people.

I've a pair of Genelec 8040s in a room. I recently noticed that if I turn one monitor off, the level of the bass on the other monitor is a lot higher, ie the room is shaking more when I play a boomy 808 kick.

When I've got the two monitors on at the same time the bass isn't as boomy. Is this some destructive interference thing with the sound from the two speakers? (there's no subwoofer in the room)

Split - could you describe how the room is set up?
The 8040s do seem to produce a lower reaching bass than it's cabinet size would suggest so may be more susceptible to room, or more likely corner coupling.

Is the 'boomy' speaker in a corner and the other one not?

splitrmx

The room is treated with a Primacoustic fibreglass room kit. Maybe I didn't explain myself properly. Normally when I have the music going through both speakers everything sounds fine.

I just noticed, by accident when I turned off one speaker a while ago that when I have some really low bass being played, as in barely audible but shaking the entire room (stuff you'd probably want to trim back in a track to give everything else space), that the really low end bass got a lot more prominent.

This happens equally with both the speakers, not just one of them. I since took the speakers to different parts of the room and got different results with both of them pointing different ways etc.

I just wanted to see if this was a normal occurrence, or maybe if there was something up with my set-up.

Maybe as a test, some other people out there could play one really low end extended kick (nothing beats a TR808!) and see if the bass seems to shake the room more when just one speaker is playing it.

PaulBrewer

splitrmx wrote: »

The room is treated with a Primacoustic fibreglass room kit. Maybe I didn't explain myself properly. Normally when I have the music going through both speakers everything sounds fine.

I just noticed, by accident when I turned off one speaker a while ago that when I have some really low bass being played, as in barely audible but shaking the entire room (stuff you'd probably want to trim back in a track to give everything else space), that the really low end bass got a lot more prominent.

This happens equally with both the speakers, not just one of them. I since took the speakers to different parts of the room and got different results with both of them pointing different ways etc.

I just wanted to see if this was a normal occurrence, or maybe if there was something up with my set-up.

Maybe as a test, some other people out there could play one really low end extended kick (nothing beats a TR808!) and see if the bass seems to shake the room more when just one speaker is playing it.

Well it obviously shouldn't be doing that.

If 2 speakers are in opposite polarity (one 'pushing' and the other 'pulling') it will cancel the bass somewhat (i.e. one speakers playing will be bassier than 2 playing) but in doing so will make everything sound thin.

Also if you move your head between the 2 speakers you'll get a very distinctive 'phasey' effect which is very unpleasant.

Does this describe the sound when you have both connected?

splitrmx

The sound isn't thin with both the speakers connected and I haven't noticed any phasing effects to far, but I'm currently in work so will double check when I get home.

If one speaker was in the opposite polarity would that point to a cable problem? I suppose I could reverse the polarity of the sound going to one of the speakers using some software program to check if this is the fault?

PaulBrewer

splitrmx wrote: »

The sound isn't thin with both the speakers connected and I haven't noticed any phasing effects to far, but I'm currently in work so will double check when I get home.

If one speaker was in the opposite polarity would that point to a cable problem? I suppose I could reverse the polarity of the sound going to one of the speakers using some software program to check if this is the fault?

You could - however speaker polarity problems aren't subtle - it's akin to being seasick listening to them!

It is unlikely that it's Polarity but lets remove the issues one by one.

splitrmx

So I checked the cables with a multimeter, they appear to be wired up correctly (and both in the same way).

Then I tested the bass levels with a pure sine wave at frequencies between 30 and 50 hz, when I turned off one channel I didn't notice any increase in the bass of the other channel which is expected.

It only appears to happen when really big kick drums, I've put it down to a quirk in the room, as it's a home studio built in a weird room (arched ceilings, arched spaces for windows). Hopefully it won't be too much of an issue, I'm pretty happy with the sound in the room most of the time, just something I'll have to bear in mind!

PaulBrewer

splitrmx wrote: »

S I've put it down to a quirk in the room

That was my initial hunch ok.

That's the value of symmetry, even if it's a less than ideal set up - at least both monitors will react the same.

madtheory

Run a series of tones, in steps of 5Hz, from 20Hz to 300Hz. You'll probably find a room mode or two. So you might need a bass trap with a mebrane on it.