doing room measurements before bass trapping?

[DanDan]

Strange room indeed. However, plenty of length.
The other issues you mention pretty much point the way IMHO.
I would cover the whole front of the room with a big thick fluffy. Some cheap frame, mesh etc. Go as thick as you can. Let's say 50cm on top of the existing alcoves. This should get at quite a few modes, eliminate front wall SBIR and eliminate all those alcove issues.
You don't have much room for a cloud, so the minimum. 10cm plus 10cm gap, FRK on top. If the floor is hard, do plenty of cloud. Or do a checkerboard pattern, absorbing opposite hard, including rugs on the floor.
The sides, same 10+10 minimum, or go for something much better, e.g. perf or slatted tuned broadly over the first two width modes, HF absorbent on front. Or angled, a la johnlsayers.com and others.
The Back:- Big wall of broadly tuned perf or why not go very thick again and kill the lot. Slats or some nice diffusors if you can afford them.
You could consider a quiet room for computers or even an iso booth. With light lath walls this could double as a very low genuine bass trap.

DD

[btroberts]

thanks Dan

I'm not sure I follow, but I will mull it all over, and hope to do some measurements as well in the morning.

[Max Dread]

btroberts - hope you don't mind if I chime in with a couple of questions while you are mulling things over....

Originally Posted by DanDan

You don't have much room for a cloud, so the minimum. 10cm plus 10cm gap, FRK on top.

I was in a similar position and therefore made two clouds 100mm thick each with 140mm air gap. But I did not use FRK faced mineral wool. Is it possible to add something to them now which would be just as effective and if so what would you suggest?

Alternatively, would it be worth adding more mineral wool into the cavity so that they were 200mm with a 40mm air gap? Or do you think the difference would be negligible. It is something I could measure in REW, but thought I'd ask first.

Originally Posted by DanDan

Or angled, a la johnlsayers.com and others.

Any further details please? Angled outward so that they reflect sound away from the LP? Or in ward so that they are more absorptive?

Cheers

Max

[btroberts]

Thanks again dan, I'll come back to the suggestions you made...

Gonna try and get these measurements done today, that right wall is currently filled with square foam pices the previsou person left up, about 3 inch thick from bass to tips (the gray egg type panels)..I guess I should take these down first right?

I guess they need to come down anyway, I'll take them down lol

[DanDan]

Do they need to come down. Maybe they are useful. Foam gets bad press here but it works quite well when used as intended.

I was in a similar position and therefore made two clouds 100mm thick each with 140mm air gap. But I did not use FRK faced mineral wool. Is it possible to add something to them now which would be just as effective and if so what would you suggest?

I wouldn't bother, the gain is small enough.

Alternatively, would it be worth adding more mineral wool into the cavity so that they were 200mm with a 40mm air gap? Or do you think the difference would be negligible. It is something I could measure in REW, but thought I'd ask first.

A thicker layer of lighter material will generally outperform thinner denser layers. 200mm is nice and thick would what density are you considering?
The john sayers site explains his ideas much better than I could!

DD

[btroberts]

Ive taken them down dan, I couldnt see the point in the right wall full of foam and the left with something else...Sadly as I have took them down portions of plasterboard have come off, give me strength

ah well, there off now!

incidentally what is the intention of foam? From reading on here I got the impression that its intention is the same as GIK stuff etc the only difference being it doesn't really work lol ?

[Max Dread]

Originally Posted by DanDan

A thicker layer of lighter material will generally outperform thinner denser layers. 200mm is nice and thick would what density are you considering?DD

I've already made the clouds with Knauf Rocksilk RS60. Density = 60kg/m3. So I'd be looking to add more of the same to make them 200mm instead of the current 100mm.

Cheers.

[DanDan]

At 60KG I would guess go 200mm. Instead of guessing though, perhaps some GS out there has a Gas Flow Resistivity for Rocksilk 60, or a decent guess. Then we could run the numbers in Whealy (my nbf...LOL) or Jens might do a Soundflow. When an airgap is replaced with fibre in this situation the gain may be relatively little. Airgaps are amazingly good value!
Good foam, used as intended, is, well, good...
DD

[btroberts]

Hi Dan

When you say big thick fluffy, what precisely do you mean? I know you mean insulation but which one. When I was planning the wall I was looking at RW3/RWA45 slabs, whats the actual name of what you mean?

Cheers

[Max Dread]

Hi btroberts

If DanDan doesn't mind me answering here - I believe he is referring to generic loft insulation.

I don't know where you are situated....I'm in the UK (where are you?). You'll often see it referred so as pink fluffy from people in the US as the generic low density/low gas flow resistivity insulation widely available is pink - so I've read! Good job it gets covered in fabric, eh?!?!?

The other thing I have learnt from reading other people's thread on GS..... this calculator can be very helpful in determining how effective different treatments might be, by telling you which frequencies different treatments (and different types of the same treatment) will be most effective at.

Porous Absorber Calculator V1.58


Back to your original point at the start of this thread - you can see how something like this calculator works hand in hand with room measurements and prescriptive tailored treatment. IE - once you know what problems your room has, and what is causing them, the calculator can help determine what to use.

Cheers

Max

[btroberts]

Thanks max, I am in the UK too. There seems to be many types of 'normal' insulation even so I still don't know which one would count as thick fluffy. I am still looking at REW, but I'm clueless tbh, have to come back to it again tomorrow.

I wish I could just move house into a room that's already pretty normal, if that was the case then I suspect my initial premise would be correct, certainly other peoples places Ive been round are fine with just a room kit put in as normal, and that goes for bedrooms, my room is pile of crap however. but I'm stuck for now

[Max Dread]

Well, from what I've read, any loft insulation that is made of mineral wool/fibreglass, comes in rolls and is light and fluffy, will do fine.

I must admit though, being an anal kind of guy I too keep thinking....."surely they're not all the same? Surely some are better than others?". And to complicate matters it is really tough to get the necessary stats (gas flow resistivity seems impossible to get hold of, but even density is difficult to find out about for loft insulation).

I've got some spare rolls of this:

Knauf Saver Value Triple Loft Insulation 200mm, 2436978

which I'm hoping would work well. But perhaps it would help both of us to hear from people in the UK who have used specific loft insulation with good results. BTW, I think the advice was to use thick amounts fluffy as opposed to "thick fluffy".


REW is not too difficult once you've had a go. Remember to check the REW forum at hometheatershack - both to read up on threads and to post your own if you are having trouble. Very helpful there. Work through the manual too - it's really helpful.

RE: "I wish I could just move house into a room that's already pretty normal, if that was the case then I suspect my initial premise would be correct, certainly other peoples places Ive been round are fine with just a room kit put in as normal, and that goes for bedrooms, my room is pile of crap however. but I'm stuck for now"

First up, let me tell you I'm no expert and am still very much learning. But from what I've learnt I'd have to disagree. All rooms present problems. Granted there are certain ratios that mean treating the room is easier, but the room still needs treating. You've got a good sized room there and I think you can make it sound great if you are prepared to give it some time and thought. And I wonder..... once you've learnt REW - take your measurement mic and knowledge to your friend's houses, measure their rooms, and see what you find.

[btroberts]

I agree all rooms can benefit from treating, but theres a difference between going into a room thats a good rectangle, with walls that are made of the same stuff, and a weird room with alcoves and walls made of diff stuff imho lol

Put it this way my friends rooms are fine to work in and all they have is some panels up basically, what I mean by that is, they have the equivalant of a room kit set up in the manner most often suggested ,but their rooms are sound to begin with compared to mine..I couldn't say how they would stack up in measurements, nobody I know has bothered measuring..Anyway, my rooms a nightmare either way, though I do agree, it actually has a lot of potential.

Actually I am not sure why Dan didn't address my initial plan, ie building new walls so as to bring the place to a 'normal' level ie how it should have been done in the first place, then thinking about a GIK kit for the treatment...or perhaps he did by not doing if you know what I mean lol We'll get there eh!

Wow, that knauf stuffs nice and cheap..interesting to see what is said about specific 'fluffy'

[btroberts]

Dan> I can't figure out how to be get things even across the width of the room using fluffy from the off. What about the following:

> Superchunk each alcove with RW3/RWA45 up to the face of the columns, so I now have an even front wall to begin with (albeit the columns are still stone!)
> Then right on top of this a wall of fluffy floor to ceiling right across the room still about 40-50 cm
> then a thin acoustic blanket or something, just for a neat look and for not breathing the fibreglass in all day (I presume completely exposed fluffy isn't good for me?, again floor to ceiling and the width of the room.

[DanDan]

bto, that's pretty much what I suggested I thought. Sorry if it wasn't clear.
Sheep may be more dangerous than fibreglass.
The Comparative Safety of Rockwool, Fiberglass, and Organic Fibers (a review)

DD

[btroberts]

Not all Dan, really appreciate your help I just wasnt sure if superchunking the alcoves with slab would be ok first rathe than all fluffy.

I'll read through the link you provided re safety.

Any thoughts on what Max and I were talking about, re: what constitutes acceptable fluffy?

Cheers

[DanDan]

Practical matters will nearly always make the decisions for you.
Local availability of fibre is always an issue. Cost too, 703 is insanely expensive in Europe. I believe there it would be better to fill the alcoves with the same light material. There are thick 'blankets' designed for filling between studs in a sheetrock wall. Supporting the stuff is an issue, wire, mesh, whatever.
Ease of handling and the itch factor, all worth considering, Ecose seem good in this regard.
DD

[Max Dread]

Originally Posted by DanDan

I believe there it would be better to fill the alcoves with the same light material. DD

Based purely on what I've read here on GS, I'd agree with that. It would seem that little testing has been done - and therefore it is tough to estimate the effectiveness of - mixing different types of product in the same trap. For that reason I'd stick with the same throughout. It also seems to be accepted that light fluffy is best when making thick areas of absorption, and it's cheaper. So fluffy all the way seems by far the best choice. Of course, you can call on the Whealy calculator to check what's best, but for that you need to know:

- what frequencies are rpoblematic in your room
- what the spec (esp gas flow resistivity) of the MW is

both of which might not be certain at present.

If you do decide to use something slightly denser (like the RW3/RWA45)either here or elsewhere in the room, be sure to call around for best prices. I found they varied widely. I even called two or three different branches of Travis Perkins. My most local one ended up quoting me packs of Rocksilk RS60 (ecose) at half the price of other TP branches!

As for the fluffy, check this out:

£3 a Roll Insulation - DIY Loft Insulation - npower

I can't say for certain that it is OK to use this, but like I say, I've read that this is nothing to sweat too much over and generic loft insulation is fine. Hopefully someone can confirm whether this stuff is ok - and likewise whether the Knauf rolls I linked to a few posts ago are ok. Both are super cheap. The oofer from npower includes free delivery and even a free saftey kit. Can't be bad! Just don't tell them what you are using it for if you end up going for it..... don't know if the subsidy allowing such cheap prices would still apply if they knew the RW was to soak up low frequencies!!!!

[btroberts]

Lol, thanks guys.

I was hoping filling the alcoves with slab first would be ok, I only need 8 slabs of rwa45 to literally fill to the face of the columns, but obviously I want to do whats best.

Maybe I'm not thinking straight but heres how I see the problem..

Lets assume I can get the stuff to stay up:

I fill the alcoves with fluffy lets say the 50 cm thickness..now all the fluffy is sticking out from the alcoves 40 cm past the columns,so the columns are bare and have now become alcoves with fluffy columns next to them?I put some in the new alcoves and the situation is reversed again

To make even right across the width of the room I'd have to shave down the thickness of some of it of it? Can you do that, I didnt think you could.

Sorry If I'm getting muddled

[Max Dread]

I cannot see any problem at all in doing it - but please do wait for a more qualified opinion as I'm still learning myself!

Basically - you fill the front wall with the desired thickness of RW. Granted, the areas where there are alcoves will have more thickness by 10cm. But if you are considering going 50-60cm depth in all, I cannot see a problem. I presume in the finish you will have a nice flush straigh wall of RW which you will then face accordingly?

Strange reflections in mids and highs caused by the alcoves will be dealt with well. And the traps will be nice and deep and therefore effective to LFs too.

As for supporting the RW, I would be tempted to build some kind of shelves going across the width of the room. I'm sure you could somehow utilise the alcoves in the design. But this really is me thinking off the top if my head and you may find others have a more practical solution.....

[btroberts]

Ok Max got you. Makes sense I guess, I was perhaps obsessing too much about the 10cm. Gotta be an improvement thats for sure lol

Ok so it looks like I'll be going all out fluffy for the front.

Yes I was thinking maybe a couple of tall room divider shelf units the ones with all square shelfs..Or another idea could be to use some office partition and fold fluffy over each one, the only thing here is that the tallest partitions are 1.8M as opposed to the 2.4M ceiling.

Otherwise I thought I could affix some batons to the ceiling with hoops in, affix a batton the top edge of each pice, put hooks in that baton and hook it through the ceiling hoops. The only question is, would it stay up or tear under its own weight?

[btroberts]

Hello guys,

only a month later lol. Well I decided to forget it and just find a place already treated etc, but after some viewings that fell threw, so I'm back again! Just installed fuzz measure..

Just got a quick question. I have read that I should get away from the mic when measuring from the listening position. Why should I get away when I will in actual fact be sat there when working and mays as well therefore be a part of the room?

Thanks

[Jens Eklund]

http://www.gearslutz.com/board/6615386-post6.html

[Max Dread]

Because when you are doing the tests, the microphone - in a sense - IS you.

It is placed where you would be placed to emulate/represent what you would hear. So if you are right there next to it, you will cause an interference. And from the "mic is you" POV, it would be akin to you sitting next to yourself!

[ajbianco]

Originally Posted by ethan winer

not likely. Though it would have helped if you told us the room dimensions. But i'm curious how the "you must measure first" proponents will address this: Attached are four graphs showing the response measured in four different rooms. I'd love to hear what specifically should be done in each room, or at least what would be done differently based on this measurement data.

--ethan

ahahahahahahahahahahahahahahaha!!!!!!!

[DanDan]

Maybe brtroberts real name is Mic. So Mic would be there when mixing.....
DD

[ciro]

Originally Posted by btroberts

Just got a quick question. I have read that I should get away from the mic when measuring from the listening position. Why should I get away when I will in actual fact be sat there when working and mays as well therefore be a part of the room?

I always heard it (to get away from the mic) ; your question makes a lot of sense to me.I just get away because this is the way people say to do - but I did some measurements <head at mix position>, mid frequencies seems a little better with "a body"there (which basically is a kind of broadband absorber , or not?).

*no, the bones...

Ciro

[DanDan]

Bruel and Kjaer, in their Measuring Sound handbook, state that the measuring mic should be at least 1M from the body. If held close, anomalies of up to 6dB around 400Hz happen. This has also been seen in practice. It is the mid frequency reflection from the body which causes the problem.
As the ear is part of the body there is no reflection. A PZM sort of scenario.
The body may cause all sorts of anomalies in terms of interfering with how the ear receives input. Whatever about the lower body, the head surely blocks HF travel between the Left speaker and the Right ear and vice versa. Above all, the Pinna has a dramatic directional and frequency altering focussing effect.
I have long argued that a single microphone, without the head blocking effect, bears little resemblance to what the ear actually gets.
I have read a statement elsewhere which suggests that measurement is typically done, equivalent to a person lying on their side on an elevated bed, good ear up, deaf in the other.

At some stage I intend to try some binaural, Jecklin Disc measurements with both speakers driven, comparing them to single mic/single speaker.
When time domain averaging is included I wonder will there be any or much of a difference?

There is also a point to be made for inserting a pair of DPA 4060's into the actual ear.

DDDD

[avare]

Originally Posted by DanDan

Bruel and Kjaer, in their Measuring Sound handbook...

For those who have difficulties using search engines, the Bruel and Kjaer Measuring Sound Handbook is attached. It is a goldmine of information of information. The graphics are very misleadingly simple.

Andre

[localhost127]

Originally Posted by avare

For those who have difficulties using search engines, the Bruel and Kjaer Measuring Sound Handbook is attached. It is a goldmine of information of information. The graphics are very misleadingly simple.

Andre

thank you