Big Challenge ( Picture now attached)

invisibl · Post by **invisibl** » Thu May 05, 2005 6:05 pm

I have a small room in a house in which to mix in NOT track in.

The Dimensions are 9 foot high, 14 foot 2 inches long and 8 foot 4 inches wide.

I will be orienting myself facing the short wall, sitting roughly centrally.

The room is a timber framed, Gibbed ( drywallerd?) bedroom that has carpet and a window on one of the long walls.

I dont have excel on my computer so I am unable to decode the various spreadsheets here add to this a total and utter lack of ability using drawing programs ( I blame my aspergers)

Also i live in NEW ZEALAND which is a wonderful place to live, but a terrible place in which to look successfully for products I see touted here and else where on the internet.

If anyone here has the time and inclination can you make suggestions that may help me in this brave new room??

Mainly I will be mixing music....But i will also be using the room for Post work .

Sword9 · Post by **Sword9** » Thu May 05, 2005 9:59 pm

You can download an excel viewer here

invisibl · Post by **invisibl** » Wed May 11, 2005 4:04 pm

Cheers Sam

I am on a mAc ...I will look around and see if I can find a similar substance for mac

(edit) Ugh. Apparently not..Ho hum

I shall persevere.........

lunatic · Post by **lunatic** » Sun May 15, 2005 11:59 pm

A search on Google for 'mac excel viewer' turned up this link at the top: http://www.panergy-software.com/product ... index.html

I use PC so I know *nothing* about the company or how well the product works but it appears as though they have a demo you can try.

Just tryin' to help out...

-Brad

invisibl · Post by **invisibl** » Wed May 18, 2005 6:23 pm

lunatic wrote:A search on Google for 'mac excel viewer' turned up this link at the top: http://www.panergy-software.com/product ... index.html

I use PC so I know *nothing* about the company or how well the product works but it appears as though they have a demo you can try.

Just tryin' to help out...

-Brad

Cheers Brad..I did a search myself and turned up nada...Go figger.

Anyway thank you for your help (again)

All the best

j

invisibl · Post by **invisibl** » Wed May 18, 2005 7:32 pm

I found this link ( amongst others)

Any good??

http://www.marktaw.com/recording/Acoust ... Calcu.html

MichaelM · Post by **MichaelM** » Thu May 19, 2005 10:47 pm

Have you tried Open Office? It is an alternative to Micro$oft Office and can open Office files including Excel spreadsheets. It is open source and can run on Mac OS 10.2+:

http://porting.openoffice.org/mac/ooo-o ... loads.html

invisibl · Post by **invisibl** » Wed May 25, 2005 5:44 pm

Cheers Michael M

I am on a work computer so I shant try that

But I will try the link from a friends mac

Cheers.

invisibl · Post by **invisibl** » Mon May 30, 2005 7:22 pm

Hey all.

Been off doing research...and a thought comes to mind..

Do bassTraps need to be cylindrical??

Could they be say square or triangular?

Prolly a reaaally dumb question...But I had to ask.

cheers

I

invisibl · Post by **invisibl** » Tue May 31, 2005 9:26 am

Another link...any good??

http://www.mhsoft.nl/Helmholtzabsorber. ... elAbsorber

invisibl · Post by **invisibl** » Thu Jun 09, 2005 3:59 pm

I have drawn up a to scale pic of my floor plan. I hope this may spur some interest in helping me ascertain the best way forward to treating my room.

I am currently trying to finish some mixes for an album and I am DYING!

Those kludgy little boxes wth hard to read print are windows.

Here are some extra dimensions

ROOM
Height 2..71
width 2.75
Length 4.40

note wardrobe reduces room to effective 3.85
Height of wardrobe 1.92
width of wardrobe 1.70

Woofer Height 1.24
Dist from rear wall .52
Dist from side wall .36

Floor is carpeted
Walls are gibbed
Ceiling is plaster
2 External walls are stucco cement.
Metal Filing cabinet height 1.01

invisibl · Post by **invisibl** » Tue Jun 14, 2005 7:01 pm

So I have followed Ethan Winers advice and am now sitting in the 38% Zone from the front wall.

I have calculated my problem Freqs with the fundamentals being
Lenght 39.2 Hz
Width 62.73 Hz
Height 63.65 Hz

I am gonna make a Menbrane absorber for my rear wall

Question. Is there a way I can utilise the wardrobe that is currently in the rear wall ( well actually effectively it is a "box" built into the room.)
Perhaps if I made the internal joins airtight Then the Doors might/could act as some sort of Helmholtz trap??

I have recycled some Rigid fibeglass ppanels and will be hanging these on an angle behind my monitors in an "L' shaped config maybe 4-6 inches offa the rear and side walls.

I appreciate the time that is spent answering all of these posts here on the forum , Perhaps if someone could glance over this post and suggest if I am on the righht track or not i would be most grateful.

Thank you

Jeremy

invisibl · Post by **invisibl** » Mon Jun 20, 2005 11:59 am

So i have constructed a Panel absorber.

Dimensions are 82 cm by 101 cm by 16 cm deep.

The resonating panel is a hefty piece of marineply about 2 odd cms thick.

It is screwed glued ( and tattooed).

Any Ideas for placement?? I was thinking at the rear of the room in front of the wardrobe doors with the center of the panel being around ear height directly in line with where I sit.

good or bad??

knightfly · Post by **knightfly** » Thu Jun 23, 2005 3:01 pm

Few comments; your room appears to have a slight "hole" in modal density around 50 hZ, but otherwise fairly well balanced -

You didn't mention what frequency you built your panel trap for; since a panel trap is a pressure device, it's easy to place it in the room so it does absolutely NOTHING; so I'd need to know about it's design frequency.

Also, did you follow a particular set of plans, and if so which one? As in, what absorbent did you use inside, and where/how is it placed/fastened?

Running your panel dimensions thru the magic formula, I get about 45 hZ center frequency; is that what you were aiming for, or am I 'way off?

I re-figured your dimensions and conversions, and came up with height of 8'11", width of 9', length of 14'5" - so if you're shooting for the lowest modal frequency of your room length, it should be around 40 hZ - that panel, if done properly, would be close enough. However, placing it in FRONT of the wardrobe won't work very well; if your room length measurement is to the wall BEHIND that cabinet, then that's where the panel absorber should be in order to work best.

The reason your wardrobe seems to improve bass is because whatever clothing you have hanging in there is trying to act as a series of "bass hangers", in addition to being a generally weak (but deep) broadband absorber.

I'd be very careful about following that "38% rule" - Ethan got that advice from Wes LaChot, and while I have great respect for both of them that distance puts you REALLY close to the 4th harmonic NULL of your room length, which is at 37.5% - so if anything, try your head just a few inches further BACK from the 38% position. Too far though, and you'll be getting into SEVERAL nulls; specifically, the first and third harmonics of your length mode. Try somewhere between 38 and 42% and see what happens, that should put you between the nulls.

Speakers should ALSO NOT be in nulls; it takes more power than any reasonable speaker can put out to overcome sitting in a dead spot, this hurts amp headroom and you STILL don't get a balanced frequency response. Stay away from even fractions of room dimensions in ANY axis when choosing distance for speakers from walls, ceiling, floor (use the center of the woofer as a reference point, and don't put it at half the room height, or at 1/3 or 3/8 or any other simple fraction of the distance between any two boundaries.

In case you hadn't noticed, this can take some time...

If you weren't on a Mac, I'd refer you to a post I did sometime back, showing how to use Paint to figure out a good starting point for you and your speakers; Oh well, for others (and your own information) -

http://www.johnlsayers.com/phpBB2/viewtopic.php?p=18059

Another thing; don't use the MHsoft calculator for helmholtz traps, it's WRONG - as are nearly every one on the net; stems from a mis-copied fomula in the AE handbook. I tried twice to get the webmaster of mhsoft's site to respond, finally gave up. "internet fact" strikes again...

The one in THIS forum has been corrected -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=1363

but it's "look-alike" at the SAE site is ALSO WRONG.

Generally, what you want to do to your room should look something like the attached drawing - HTH... Steve

invisibl · Post by **invisibl** » Thu Jun 23, 2005 7:37 pm

Cheers steve

first up

Lenght 39.2 Hz
Width 62.73 Hz
Height 63.65 Hz

These calcs are based on the room being at 4,40 mtrs

at the closed wardrobe length of 3.85mtrs then I get

44.67Hz
62.54Hz
63.46Hz

In the same order of LW and H

The membrane absorber was built on the idea that iffa I got it close enough to that 39/44Hz spread the fact that i had glued fiberglass to the inside of the front panel I would spread the resonating freq by an octave.
BUT......

On ethan winers site he says that to make a panel trap successfully one shouldnt have anything attached to the front panel, whereas the S.A.E site says this is theway to go ( as do several others) Hmmmm Light to be shed here methinks...

Also how should I measure the room properly. As you can see from the floor plan i posted I have the wardrobe at the rear of the room. This wardrobe will stay put and not be removed ( else I will be killed by my wife no doubt)
So which dimension should I go with. 4.4 or 3.85??

The Panel constructiion is as listed above. The dimensions were kinda fudged around material I had already ( the plywood)
I HAVE screwed the beggar and glued the beggar ( sounds rude almost)
I have glued a 2 inch thick piece of fibeglass (703) ONTO THE front ply panel. The back is a 5 mil piece of MDF board also glued on. All joins have been subsequently sealed with a silicone sealannt. So no leaks bro.

It gives a very satisfying boom when hit that sounds great...But only when it is dry enough shall I place it and as my Dad says " suck it and see!!" Note.....The undamped side rings on a little but the dampened side seems to have a much shorter decay.

The reason your wardrobe seems to improve bass is because whatever clothing you have hanging in there is trying to act as a series of "bass hangers", in addition to being a generally weak (but deep) broadband absorber.

Yeah at the moment the wardrobe is jam packed with cushions and blankets coz my wife is a cushion making freak!!!!. But dont tell her I said that.

I have flirted with the idea of a helmholtz or slat type arrangement but All I have read seems to suggest that I best be spot on with both my calculations and my carpentry ( and I trust neither) So I went with the panel absorber idea coz oit seemed to have a little more room for error.

I have made up some panels of 2" thick fiberglass (703) to hang on the walls to the side of and at the rear of my speakers ( event 20/20 BAS).These are framed with 2x2's and are covered in a breathable fabric. They will be off the walls by about 5 or so inches.

I have mounted the speakers slightly higher than at ear to tweeter height. I am gomnna experiment with pointing em down somewhat. I have intuited that perhaps I would effectively increase the rooms length that way right? wrong? will I just make the modal behaviour more unpredictable? I cannabalized a piece of furniture, An old vertical shelf. That i have mounted the speakers on. This is made of Hollow MDF THAT IS pegged or doweled together. i cut it in half to put the speakers on. I will post a pic or two in the next week. ( please no laughing) But i wonder if this will add resonance to the speakers. I have tryed decoupling them by palcing the speakers on a Plastic pot plant holder ( boy does this sound amateurisjh) These Pot plant holders are made in a "cross" shape when viewed from above. From side on they are made of a series of pyramids. The tepory being that there is more amount of surface area at the bottom of the speaker/top of the decoupling device, But very little at the top of the "stand"

Lastly I have spectrafoo on my Mac...Is this sufficient to be able to get an accurate RTA reading of my room?>?????

Thank you so much.

Jeremy