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Discussion Starter #1 (Edited)
Hey All, I'm hoping to get a few tips on treating a room for mixing (mainly dance music). Unfortunately, I am stuck with near-cubic room dimensions of 97" x 100" x 95" (wxdxh) and from what I gather from reading through a few threads, cubic room dimensions are far from favorable when trying to achieve a suitable acoustic environment, not to mention the fact that small rooms are also problematic and are a poor starting point. However, I simply have to work with what I've got and fortunately, I have a decent budget to help achieve a suitable working environment. My budget is approximately €750, and considering the size of the room, I find it hard to imagine exceeding it, however it's good to know that it's there if the need arises.

So, I've gathered this much: that it makes sense to first discover any problems with the room's acoustics before treating them accordingly. . . It's logical really! I'm at the point now where (considering my needs) I'm wondering if it's worth while to buy a suitable mic (like the behringer ecm 8000) to measure the vital aspects of the room acoustics using REW or whether calculating the various acoustic properties the old fashioned way will suffice? Bearing in mind that the room dimensions are very straight forward with very few interferences such as the window & cabinet covering pipework. I don't know whether I should be working towards a very dead room by minimizing reflections and absorbing as much sound as possible or if I should be trying to achieve a space that is perceived to be larger that it actually is using diffusors? I've researched a lot on the site and have acquired a huge amount of information regarding the topic but with so much information, it's hard to know where to begin. Any recommended approaches, surplus information, what I can expect to have to build/install etc. would really be a great help as I'm ready to begin building asap. If I can provide any more information which will aid your input, don't hesitate to ask! Thanks in advance for your replies.
 

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Just use a Radio Shack SPL meter for the mic along with the available correction file. What you're looking to do is get the seating and speakers and sub dialed in to the best possible locations. No need for +/-1 db accuracy - just looking for general problems and relative change when moving things.

Pretty well known what will need to be addressed - more a matter of finding the best starting point.

Bryan
 

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Discussion Starter #3
Cheers for your input Bryan! Great to have a clear idea of where to get going from. I've priced the Audio Shack SPL Meter and it's pretty hard to find any distributors this side of the atlantic. I could buy one from the US but it actually works out cheaper for me to go with the ECM8000 from Thomann in Germany at just €48.

So, today I cleared out the space and assembeled my new desk from ikea. I'm forced to order a pair of IsoAcoustics ISO-L8R155's because the room's so small that it wouldn't be possible to fit floor-rising monitor stands - there simply isn't enough room for the base plates! Due to spatial restrictions, I'm only really left with two options for which way the table can be orientated, considering it will need to be distanced a certain amount from the wall it faces. Those two options are: (a) the way it's positioned in the pictures with the table positioned against the rear wall or (b) with it positioned against the wall to the right. REW will reveal all but until then, I'll uplaod a few pictures to give you a clearer idea of what I'm working with.

 

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Discussion Starter #4 (Edited)
So, my new equipment arrived over the week and I've taken two sets of measurements for the two possible table orientations. I've read as much as I could find with regards to taking measurements and posting graphs, so hopefully I got it right the first time around but if I need to supply any additional information, please don't hesitate to ask.

Position 1: Table facing the window (as seen in pictures above). The speakers were positioned 35cm from the rear wall and were equidistant at 55cm from the two sidewalls (all measurements taken from centre of backplate). However, on the right hand side, there sits a fixed timber cabinet (11cm depth) which covers pipe-work, meaning that the right speaker is 44cm from the cabinet face. This table orientation fits the room snugly leaving amples floor space and also leaves plenty of leeway with regards to moving the table back further from the wall if necessary.

Position 2: Table facing the side wall on the right hand side. The speakers were at a distance of 42cm from the rear wall and were again, equidistant at 63cm from the side walls. Again the wooden cabinet comes into play here however, this time it rests to the left of the table and does not inhibit the straight line measurements from the centre of the speaker's backplate. This orientation is far less suitable with regards to use of floor space leaving verry little room to maneuver around the desk and equipment.

So, I guess my next question is: where to go from here? The problems associated with both table orientations seem to be quite similar, with only the centre frequency of the major low end dips and peaks shifting slightly and some variation between the two orientations from 5kHz up. So does that justify using the first position for it's added space. Also, I'm presuming that the timber cabinet might act like the resinator would on a guitar so, be that the case, I'm guessing that the next step would be to treat it before proceeding to dealing with reflections? Room dimensions are 240cm x 255cm x 245cm or 95"x100"x97". Thanks in advance for your input!


Position 1: room frequency response with both loudspeakers playing back test sweep.

Position 1: overlay of room frequency response when loudspeakers play back test sweep separately (blue is left, green is right).

Position 2: room frequency response with both loudspeakers playing back test sweep.

Position 2: overlay of room frequency response when loudspeakers play back test sweep separately (turquoise is left, gold is right).

Position 1 LF waterfall graph.

Position 1 LMF waterfall graph.

Position 2 LF waterfall graph.

Position 2 LMF waterfall graph.
 

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The room is pretty square and close to a perfect cube. Not surprising that you are getting wild swings similar in both orientations. Where are YOU in relation to the front to back distance in the room? Did you try moving the mic front to back to ID what items are coming from where?

Bryan
 

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Discussion Starter #6
Cheers for the reply Bryan. My listening position is pretty much equal distance from the front and rear wall in both orientations (approx. 120cm or 42.5" from both front and rear walls in position 1 and approx. 127.5cm or 50" from both in position 2. I only took measurements at the listening position in both orientations so unfortunately I didn't move the mic front to rear. What "items" exactly does this technique help identify. I think my problem is that I don't have a clear idea of what measurements need to be taken in order to yield useful results. I had no success when searching the forum for a related topic but if anybody knows where I could find one please, do let me know. If not, would someone mind giving me a general idea of what measurements to take and where? Thanks!
 

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Just moving the mic will show us which of the problem areas are related to your seating position, what a better position may be, and which ones are not related to that.

If you just do your position and then forward or back a bit, that will help. Sitting in the middle of the length really isn't good. You'd like to avoid sitting int he 40-60% region.

Bryan
 

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Discussion Starter #8 (Edited)
Thanks again Bryan. First, I just want to establish a quick reference system. Just to recap, the room dimensions are: 240cm - front/rear walls, 255cm - left and right walls, 245cm high. Below is a labeled diagram of the room with the table facing the front wall & window. The following results were all recorded using the same table orientation while I simply moved the apparatus around the room. The listening positions were measured at 3 different distances (see red, blue and green lines in diagram measured at 80cm, 120cm and 140cm respectively) from the left wall. At each distance (along each line in diagram) the listening position was moved away from the front wall in increments of 10cm, starting from 110cm (which leaves just about enough room to fit bass traps in the front corners). The following freq. response curves are labeled according to the microphone's distance from the left and front walls respectively. (i.e. 80cm x 110cm = 80cm from left wall x 110cm from front wall).


Plan view


80cm x 110cm

80cm x 120cm

80cm x 130cm

80cm x 140cm


120cm x 110cm

120cm x 120cm

120cm x 130cm

120cm x 140cm


140cm x 110cm

140cm x 120cm

140cm x 130cm

140cm x 140cm

I read somewhere, that changing the distance of each recording by approx. 4' between each take is adequate to find acoustic problems in a room. However, due to room size restrictions my increments were a bit smaller than that. So, sorry in advance about the small increments but they were the most I could offer when taking room/table size restrictions into consideration.
 

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That's a good way to go, unfortunately, again, it's just too coarse. No real way to tell what's going on when you do a 20-20k plot. Just knock those down so it's like 30-300Hz so we can see more detail in the bottom end which is where you will benefit from this exercise.
 

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Discussion Starter #10
30Hz - 300Hz Sweep
Again, all measurements are taken from left and front walls respectively. (i.e. 80cm x 110cm = 80cm from left wall and 110cm from front wall.


80cm x 110cm

80cm x 120cm

80cm x 130cm

80cm x 140cm


120cm x 110cm

120cm x 120cm

120cm x 130cm

120cm x 140cm


140cm x 110cm

140cm x 120cm

140cm x 130cm

140cm x 140cm
 

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Overall the sub level seems very low. If no sub, then likley the speakers just don't go that low. Sitting monitors on the desk like that is going to give a lot of boundary reflections in the mid to upper bass. I would raise them up more toward ear level.

Door in the center of the rear wall is problematic. Overall, I would recommend:

2 4" min panels on the ceiling as a cloud, 4 4" panels min on the side walls, and 2-3 6" min panels centered across the rear wall. Likely have to use a stand for 2 of 2 or the center of 3.

Bryan
 

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Discussion Starter #12
Hey Bryan, thank you for the advice. The monitors are a pair of krk rokit rp6's (no sub) which are only rated to deliver between 48Hz-20kHz, so that explains the lacking low-end. Also, they are suspended at ear level on a pair of isoacoustic isol8r's, so boundary reflections are minimised.

I just have a couple of questions before I proceed to building the panels.
Firstly, when you say "min", you're referring to the minimum thickness of that panel right?
Also, when you say four panels on the side walls, I'm presuming that you mean two on each? I'm just conscious of the possibility of needing corner treatment in the future and four panels on each side wall would not permit this, however 3 on each could work. I'm just clarifying this specification to prevent any hinderences in the future. Two in the rear shouldn't be a problem! Also, I read somewhere that by spacing the panel from the wall, it becomes more efficient so would this be necessary at any of the specified thicknesses? And finally, what density rockwool should I be using? It's available in both 3lb/ft^3 and 6lb/ft^3. Thanks in advance for your response!
 

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Yes - I meant 2 on each wall. Not sure how 2 on each won't work but 3 on each will?

I'm not real concerned about the rear corners so don't sweat that too much - just approx 45cm for the corner absorber and then 120 cm for the 2 wall panels. Should have plenty of space for that.

Still need the rear ones

Yes - just in a hurry and didn't type out minimum.

Stick with the 3lb/cu ft. No reason to do the 6lb and in some cases, the less dense actually works better. As good or better for less money = can't lose....

Spacing off the wall can let you 'cheat' a little bit. 4" with a 2" gap is better than 4" on the wall, but not as good as 6" on the wall. General rule of thumb is that the optimal (and max) gap you should use = the thickness of the absorber - 4" with 4" gap, 6" with 6" gap, etc. In reality, most people don't have 12" to work with except maybe on the ceiling. Don't feel bad doing 6" with a 2" gap if that's what you can swing. It's still better than 4" with a 4" gap.

Bryan
 

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Discussion Starter #14
Hey Bryan, once again, many thanks for your guidance. My apologies about the delayed reply, I've been away for the past week and haven't had a chance to sit down and update the thread. I'll be ordering the supplies this evening and will document and post the project when I have the panels built and installed! Thanks again!
 

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Discussion Starter #15
Hi All,

I finally got my absorbers built and installed last week.
The specs are as follows:
Rockwool density 3lb/ft^3.
Wall and ceiling absorber dimensions: ~ 47" x 23.5" x 4"
Door mounted absorbers: ~ 47" x 23.5" x 6" (Note: Two 6" absorbers are mounted horizontally, one over the other 6" from the door.)
All but the two absorbers on the right wall are spaced the same distance as the thickness of the absorber from the wall. See diagram below. Mainly because we ran out of wood to add spacers! :gah:
Anywho, here are the response graphs before and after the absorbers were installed.
Any feedback would be greatly appreciated. Thanks in advance! :D





30-20kHz 1/3oct. smoothing. Green = No absorbers, Purple = Absorbers.


30-300Hz no smoothing.
 

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Still need to figure out the big dip around 80Hz. Try measuring it all as is but with the mic forward a foot, and then up or down a foot and see if the center of the null moves.
 

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Discussion Starter #17
First off, some pics of the absorbers during construction and installed! Apologies about the orientation on some of em, they were right side up when I uploaded them :)
 

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Discussion Starter #18
Hey Bryan,

I moved the listening position backwards by approx. one foot but to no avail. However, while in the original listening position, I moved the microphone up by approximately 1ft. and hey presto, the centre frequency of that null moved from ~78Hz - ~92Hz. I'm intrigued to learn what this means! Thanks in advance for any assistance. See both 30-300Hz and 30-20kHz freq resp graphs below.

30-20kHz 1/3oct. smoothing. Green = Original listening position, Purple = 1ft. above original listening position.)

30-300Hz no smoothing.
 

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Well you actually got 2 nulls now. One is obviously a height problem either modal or a boundary related phase issue (SBIR).
 

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Discussion Starter #20
So moving back or forth doesn't make any major diference in this instance, vertically only introduces more problems . . . So you think it may be possible to effectively treat the problem with more absorbtion. The corners are still untreated at present and I have plenty more rockwool left over if necessary? Any input would be greatly appreciated! Thanks
 
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