penguin

what should i read out of this FuzzMeasure
« on: August 01, 2010, 01:06:40 PM »
this is my room measurement, with No Smoothing

speaker : modified custom PMC with sub. bryston 3 amp

below 100hz is my sub. without a sub, it looks similar, with less bass as expected...

i have some basic treatment. no bass trap at corners at all. as i have door, fireplace etc at corners... so its hard to place them...

how does it look, how can i improve, what is the range i should be getting in to...

EDIT: this is left ch only. right ch looks similar,
« Last Edit: August 01, 2010, 01:08:25 PM by penguin »


penguin

Re: what should i read out of this FuzzMeasure
« Reply #1 on: August 01, 2010, 01:10:57 PM »
1/12 smoothing looks like this


lolo-m

Re: what should i read out of this FuzzMeasure
« Reply #2 on: August 02, 2010, 12:09:02 PM »
I don't use FuzzMeasure as all my computers are PCs...
From what I see in the first response curve, you've got a problem at 1K and then to all the above harmonics (2k,3k,5k...).
First I thought it was a dip centered at 1Khz due to some wall reverberation but the surprising thing is that the 2k deep should be more deep than it is.

What are the crossover frequencies ? Especialy the mid/high ?
Hard to be a punk... But sometimes you have to...

penguin

Re: what should i read out of this FuzzMeasure
« Reply #3 on: August 02, 2010, 03:37:57 PM »
crossover frequency is 3khz.

edit : above 4k is mostly my work_bench first reflection... without work_bench its smoother, also taped a tissue on tweeters. , hi frequency rolls of nicely above 4k now.
 
« Last Edit: August 02, 2010, 03:41:44 PM by penguin »

lolo-m

Re: what should i read out of this FuzzMeasure
« Reply #4 on: August 03, 2010, 02:06:04 AM »
As the crossover frequency is 3k, what I can say about the curves is:
- Try to reverse the polarity of your tweeter. It can solve the dip at 3k I didn't understand. If it's worse, it's maybe because of the tweeter response.
- Find the wall that make the 1k dip and put some rockwool or a schroeder diffusor on it. 1KHz wave length is about 34cm. There's a wall somewhere that reflect the sound creating the dip at 1kHz, then 2kHz, then 4kHz, then 8kHz...

Tell if you find something.
Can you post a quick drawing of your work place with some distances ?
Hard to be a punk... But sometimes you have to...

penguin

Re: what should i read out of this FuzzMeasure
« Reply #5 on: August 03, 2010, 09:01:57 AM »
hey lolo-m , thanks so much...

i actually reversed the polarity of my tweeters, while ago, i had a really nice response, as you guessed... dip disappeared,
i then reversed back to original polarity, in_case i would damage the tweeters ???

i suppose, its fine to use tweeters in reversed polarity ?

EDIT: basic drawings on the way :)
« Last Edit: August 03, 2010, 09:04:27 AM by penguin »

penguin

Re: what should i read out of this FuzzMeasure
« Reply #6 on: August 03, 2010, 09:20:30 AM »
plan
« Last Edit: August 03, 2010, 09:27:01 AM by penguin »

penguin

Re: what should i read out of this FuzzMeasure
« Reply #7 on: August 03, 2010, 09:21:11 AM »
plan2
« Last Edit: August 03, 2010, 09:27:38 AM by penguin »

penguin

Re: what should i read out of this FuzzMeasure
« Reply #8 on: August 03, 2010, 09:21:42 AM »
plan3

i am facing the low wall side,
« Last Edit: August 03, 2010, 09:28:09 AM by penguin »

Arno

Re: what should i read out of this FuzzMeasure
« Reply #9 on: August 03, 2010, 04:43:17 PM »
Any chance to measure with other monitors?
Even cheap bookshelf speakers should reveal whether this is a crossover or tweeter polarity issue.

You could also try moving the measurement mic a few centimeters/inches to rule out any close reflections from console or desk (when the frequency of the notch changes)

If this gets sorted out, I would focus on the low end of the spectrum. There's a problem around 50Hz (length and width?) 74Hz (width) 125Hz (width and height)
You can calculate these frequency's into wavelengths and understand which walls are causing standing waves.
But there's nice little java scripts out there that do it for you, with all associated harmonic multiples.
Google: room mode calculator (or if you have an iphone/touch, I use AudioCalculator)
With an angled roof it's much harder to calculate the depth of the room, but in reality it's a great advantage.
Although, I have these 'half angled' walls in my studio too, but this side (front to back) was most problematic and needed (needs) quite some basstraps.

Since the width is almost exactly twice the size of the length, I would focus on that in the first place.
Try to record a waterfall (frequency response x time axis) This should really reveal most critical frequency's.

Btw, don't take any of this for granted ;D I'm not an acoustic expert but I had quite some good results here in my own studio, fighting the laws of physics.


penguin

Re: what should i read out of this FuzzMeasure
« Reply #10 on: August 03, 2010, 07:24:11 PM »
Thanks Arno,
i think i will deal with 3k later... i remember in my old setup PMC fb1+ had this same problem, i will call PMC UK for their new crossover for FB1i, which
i believe they have solved this issue with new crossover frequency...

i will try get waterfall and new monitor measurement tomorrow...
because of my angled roof i cant really calculate anything... i have no idea how to compensate it...
i remember reading "taking average heigh"t at once, but doesnt really work... i think i will have tons of bass trap in front and back...

or move to this room below...
but i have to knock down a wall and make door etc... also need to insulate floor from basement... seems more hassle...

EDIT : height on lower side is 160cm, same as other room
« Last Edit: August 03, 2010, 07:26:09 PM by penguin »

lolo-m

Re: what should i read out of this FuzzMeasure
« Reply #11 on: August 04, 2010, 02:55:52 AM »
hey lolo-m , thanks so much...

i actually reversed the polarity of my tweeters, while ago, i had a really nice response, as you guessed... dip disappeared,
i then reversed back to original polarity, in_case i would damage the tweeters ???

i suppose, its fine to use tweeters in reversed polarity ?

EDIT: basic drawings on the way :)
You send an AC signal into the speakers, so there's no way to damage a tweeter wiring it reversed. It is normal to have tweeters wired in "reverse polarity" if the mid/highfilter is a 3rd order filter as it is the only way to get acurate phase between the tweeter and the mid driver at the crossover frequency. Most of the good passive filters are 3rd order in that kind of frequency point and have the tweeter wired reverse.

I don't have a lot of time today, but everything Arno said is OK. (I'm not an acoustic expert too but my main work is to install large PA so I've got quite good acoustic basis).
Hard to be a punk... But sometimes you have to...

lolo-m

Re: what should i read out of this FuzzMeasure
« Reply #12 on: August 04, 2010, 03:01:31 AM »
There's a problem close to 70 Hz. As for the tweeter it could be interresting to change the sub bass driver polarity and look (hear) what changes.

In small places, phase accuracy is really important to solve a lot of problems. Then you start fighting with the accoustics which is an hard battle to win !
Hard to be a punk... But sometimes you have to...

penguin

Re: what should i read out of this FuzzMeasure
« Reply #13 on: August 04, 2010, 10:25:01 AM »
checked tweeters and they are already reversed... normal polarity is worst...
seems like its crossover frequency.... PMC changed their 3k crossover frequency to 2K while ago on their most 2_way speakers....

some measurements...

yellow: PMC,
blue : blue 2.1

ps: fuzzmeasure waterfall is strange... i will try roomEQ later.
  


 

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