Small rented room

First hello to all of you in this amazing and full of knowledge forum! My name is Markus and i am from Switzerland (i apologize for my bad English) ! As states in subject of post,i am in a small rented room where i have PITA for about 6 years with room acoustics.Room is place where i spend most of the time making my own music. I have made allready tons of trials and errors triying to make this room available for mixing-i know that dimensions and relations between them are critical,but still in course of searching for some best solution to bring the listening experince on the higher level. Reading lots of Threads i have found that lot of guys have a succes with soffit mounting speakers. I still didn`t saw that somebody has share measurement results before and after,and i have decide to try and make some litlle test with some plywood panel / 0,6cm. I have cut the middle of the panel(according to dimensions of my speaker) and just put it against my speaker and measure before and after. And it was WOOOOW - huge difference in bass response---without any kind of building structure,just improvisation of the real structure. Then i have try with some more panels to try isolate the speaker even more,and it was also huge step up in the measurement. So :lol: now i think that i know what i wanna to do next to try to make the situation better.From the si I have post some picture of the room --actually i apologize for it,cause i dont know to work with sketchup,i have try to do my best to show you some preview about the dimensions-The room is 440 L x 230 W x 245 H. As stated, before somebody can post the questions;i have search threads about soffit mounting and i have found lots of great solutions to build it (Mr. Kendale,Barefoot,Sayers,Gareth,but i didn`t find any kind of formulas or ratios or something that can acctualy help me to calculate out the dimensions of the soffit structure according to dimensions of the room(or i am STUPID(it can be :D )). The budget for the construction is i think more then enough-1000 $. So i would really be thankfull if somebody can help me out to figure the dimensions,angles of the soffit structure according to dimensions of my small room. Thank you all .

I will answer two of these topics and leave the other topics to those better suited. 1. Here is a chart that shows good ratios for rooms. If your ratios are anywhere within the dotted line, the should be OK. This is from the Master Handbook of Acoustics. 2. Beware of flush mounting speakers that are not designed for it! Read and study this thread http://www.johnlsayers.com/phpBB2/viewtopic.php?f=12&t=718&start=15

Hi Eric and thanks for quick reply. As long we are spoke about the room ratios it can be critical with my room,but the reality says litlle bit different. I have tested and measured and the results are there-so much improvement with some improvisation of soffit. According to speakers,there will be no problem-those are Klein&Hummel O300D-closed cabinet,with control up to -9db for the bass. They can be soffit mountined. Thanks one more time for quick reply.

As long we are spoke about the room ratios it can be critical with my room,but the reality says litlle bit different. I have tested and measured and the results are there-so much improvement with some improvisation of soffit.

Two points about that: 1) For a rectangular room with those dimensions, the ratio is 1 : 1.06 : 1.91, and Bob Golds calculator comes up with the following conclusion: "A worst case scenario calculated by RPG" 1 : 1.075 : 1.868": The Bonello diagram is not too good either, the volume is less than half the minimum recommended by ITC and EBU, and the room fails two of the three BBC tests. The modal spread might be reasonable, but I wouldn't say that the room is good. HOWEVER:... 2) If you soffit mount (flush mount) your speakers, then your room is no longer rectangular, the dimensions you gave are no longer valid, and you can no longer use simple analysis for predicting modal behavior any more! The soffits panels themselves change the modal behavior of the room (at the very least for the 1,0,0 axis and all tangential and oblique modes that involve the front end of the room). So what you actually have is very different from what theory and simple spreadsheets predict. - Stuart -

Hi Stuart! I allready know everything what you have said,thats why i am trying to search for some help from all of you here. :cry: I have try so many things to improve the situation and now with some naive movement i have made huge improvement. Thats why i have asked if someone can help me to calculate optimal dimensions,angle for soffit construction. Thank you for the reply!

Somebody with some proposal :idea: ? Thanks

Come on guys!?! Is it possible that no one wanna colaborate??? I have try to make some model of soffit in Sketchup-now i am interested did i got it right or the size is to small or to big? Also did i got the job right with angles? Thanks and dont fell bad to reply - i need help! :?

Your basic idea for the soffit is fine, and the angles look OK ( I didn't measure them, but I guess you did?). You just need to add the support structure for the speakers. If you are going to put active speakers in there, then you need to consider cooling. You could also use John's idea of putting bass trapping behind the lower part of the soffit. Search the forum and you'll find some examples of how to do that. - Stuart -

Stuart couple of more questions if its ok : 1. To take 38% rule,as a listening position with soffit-JOhns designs doesnt look like that? 2. Is there any bad thing if i go further to the front wall of the room,acctualy making the soffit depth smaller? Thanx Markus!

1. To take 38% rule,as a listening position with soffit-JOhns designs doesnt look like that?

38% is a guideline, a starting point, a good place to begin, but it isn't written in stone. There are several ways of designing a room, and they don't all use the same principles. the 38% "rule" is just the theoretical best point for a perfectly rectangular room. If the room is not a perfect rectangle, then 38% probably isn't the best position any more. If you change the shape of the room, then you change the modal response. So john's designs often do have the mix position at another location in the room, but John's designs are almost never rectangular! John has determined the best location for the mix position in his rooms, based on the actual room layout and years of experience. I'm betting that if John ever did build a perfectly rectangular room, the mix position wouldn't be far off 38%...

2. Is there any bad thing if i go further to the front wall of the room, acctualy making the soffit depth smaller?

Don't forget that you need enough space behind the soffits to fit your speakers inside, plus ventilation space. Also, if you make the front soffit panels smaller, then you are not maximizing the effect of soffit mounting. The idea of soffit mounting is to increase the size of the front panel to be as big as possible. The concept is called "infinite baffle", which basically means that the soffit is bigger than the dimensions of the lowest frequency sound waves that the speaker emits: Of course, you can't actually make a soffit that big in any reasonable room, but the bigger you make it, the better effect you get. As always, deciding on the size of the soffits, the mix position, the speaker angle and everything else is a trade-off. - Stuart -