MF 1000

Treating Room Nodes with bass traps etc

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Super Wammer

Thought I'd drag this away from the active topology thread.

According to REW I have a dip in my bass curve at around 60-65 Hz.....is this a room node .....how do I confirm this ......and can I do anything reasonable to improve it that is also wife friendly ??????

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12 minutes ago, MF 1000 said:

how do I confirm this

I'd be astonished if it wasn't a room mode issue. I guess a nearfield measurement of your sub would help exclude it being a source cause.

Have you played about with the Room Simulator in REW? I'd do this if your room is roughly cuboidal, and see what effect changing subwoofer location has, and listening position as well.

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I realise I assumed it was only your sub being a meaningful source of sound at 60 Hz but it might well not be? If there are multiple speakers at play at this frequency then phase matching across the crossover region is another thing to look at...

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35 minutes ago, MF 1000 said:

Thought I'd drag this away from the active topology thread.

According to REW I have a dip in my bass curve at around 60-65 Hz.....is this a room node .....how do I confirm this ......and can I do anything reasonable to improve it that is also wife friendly ??????

Do your ears confirm something odd happening, or is it just the measurements?

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Super Dealer
42 minutes ago, MF 1000 said:

Thought I'd drag this away from the active topology thread.

According to REW I have a dip in my bass curve at around 60-65 Hz.....is this a room node .....how do I confirm this ......and can I do anything reasonable to improve it that is also wife friendly ??????

Is the dip in both left and right channels at the same frequency?

As Martin suggested enter your room’s dimensions into REWs room simulation feature , dips in FR if they are room modes are really difficult to treat, you have to absorb bass, which means lots of passive treatment, resonators/membrane traps or subs used destructively perhaps in a sink/source configuration.

The good news is that your brain tends to fill-in dips but can’t ignore high resonant peaks,

Keith

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Super Wammer

This is the freq response curve at present .....the green line

IMG_0097.thumb.JPG.75b6bcd263fe0f26fbdaec4c0021190e.JPG

On a listening test I don't 'feel' there is an issue between 65 & 90 Hz.  I've tried adding in eq on the dcx crossover for the bass channel (the Volt drivers are running 10-120Hz) but it has little effect.

Ill have a look at nearfield analysis of one of the Volts to determine if it's a driver issue.

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Super Dealer

‘Usually’ one looks for a 10dB downhill slope between 20 and 20kHz, bass is rolling off at 35Hz, I would have thought the 150Hz peak would be more of an issue.

Keith

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Is that measurement for left and right played together? Measuring separately is what to normally look at when comparing over the full frequency range, which might look somewhat different.

Am I right in remembering you posting recently that you're really happy with the sound of your system? If so I'd be inclined to not get too caught up in this.

To focus just on the sub region, the sort of variation you have looks just like a normal domestic sized room response, which you'll find will vary with where you measure and where the sub (or is it subs?) is placed. EQ can be useful in this region to reduce peaks but don't try to 'fill-in' nulls. You won't succeed but will likely end up increasing distortion by making your sub work harder.

I could start talking about room treatments but I suspect it's not really what you want/need.

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Super Wammer

I'm very happy with the sound of my system at present.  The curve is taken from a umic mic mounted between the back cushions of my sofa at ear height to replicate my listening position.

I'll do some more analysis left & right along with nearfield testing near one of the Volts too.

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15 minutes ago, MF 1000 said:

I'm very happy with the sound of my system at present.  The curve is taken from a umic mic mounted between the back cushions of my sofa at ear height to replicate my listening position.

I'll do some more analysis left & right along with nearfield testing near one of the Volts too.

Have you measured each speaker independently or both playing simultaneously?

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Super Wammer

The curve is from all speakers driven by my 5 way fully active system 

10-120Hz Volt 18"

120-1200 Hz - bass drivers in the KEF103/4

1200-3500 Hz midrange drivers in the KEF 104/3

3500-5000 Hz tweeters in the Kefs

>5000 Fostex T90 supertweeters

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1 minute ago, MF 1000 said:

The curve is from all speakers driven by my 5 way fully active system 

10-120Hz Volt 18"

120-1200 Hz - bass drivers in the KEF103/4

1200-3500 Hz midrange drivers in the KEF 104/3

3500-5000 Hz tweeters in the Kefs

>5000 Fostex T90 supertweeters

Each speaker musu/should be measured separately.

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8 hours ago, MF 1000 said:

I'm very happy with the sound of my system at present.

This really makes me want to say just stop looking for problems then.

(What you've posted so far in this thread just raises a huge number of questions but I'm genuinely concerned that properly going into all of this will make you less happy than you are now.)

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Super Wammer

I might have chance to do some more analysis this morning and post up the curves.  I'm happy with the musicality of the system and it soundstaging so any it's more a case of developing my skills with REW and the dcx units for minor shaping of the response curve rather than step changes etc.  

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11 minutes ago, MF 1000 said:

I might have chance to do some more analysis this morning and post up the curves.  I'm happy with the musicality of the system and it soundstaging so any it's more a case of developing my skills with REW and the dcx units for minor shaping of the response curve rather than step changes etc.   

Could you reduce the amplitude of the vertical axis to 50dB-wide, say 35Hz to 85Hz or whathever is right for the curve (just click on LIMITS upper left corner)?

Also can you post a plot with psychoacoustic smoothing as well? It looks like the response below 400Hz is shelved up by some 5dB or more which could be a bit too much.

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