Big Challenge ( Picture now attached)

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 .

You can download an excel viewer here

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.........

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

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

I found this link ( amongst others) Any good?? http://www.marktaw.com/recording/Acoust ... Calcu.html

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

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.

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

Another link...any good?? http://www.mhsoft.nl/Helmholtzabsorber.asp#HelmholtzPanelAbsorber

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

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

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??

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

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

Hi Steve and all... Quick question... Should I be measuring my room from the front of the wardrobe where the doors are? 4.4 mtrs Or the Wall that is at its back? 3.85 mtrs I am getting the hang of this but Until I understand which dimension is to be adhered to...All my calculations are for nada. Thank you Jeremy

I think you got dimensions reversed; anyway, you would use the ENTIRE room dimension for calculation, keeping in mind that if the doors of the wardrobe are closed that they will ALSO cause fairly pronounced modes - IOW, some of each :? As to location for fiberglass, a membrane/panel absorber should NOT have the fiberglass touching the front panel. A Slat/Slot/Helmholtz absorber SHOULD have the insulation touching the front panel; otherwise the front panel may ring and actually ADD sounds back into the room... Steve

Sorry, missed a point or two - Bass traps do NOT have to be cylindrical, in fact they're more effective when NOT - there are so many kinds of traps, and people tend to call them ALL "bass traps" - most cylindrical traps other than Helmholtz types don't do much for bass anyway; more for low mids. Better if you think of traps as three distinct types - absorptive (soft outside) panel (hard outside) and perforated (Helmholtz, also hard outside) - Absorptive are generally quite broadband, and don't do a lot for bass until the air space between them and boundaries are fairly large (couple feet or so) - they work on the 1/4 wavelength principle, meaning that they peak at the frequency where the distance from their front surface to the wall = 1/4 wavelength of the sound to be absorbed. They have useful absorption at LOWER frequencies than that, maybe an octave or so; and will absorb all frequencies HIGHER than the 1/4 wavelength pretty completely. Panel traps are tuned resonant traps; they work by absorbing(turning into low grade heat) the energy that they are resonant to; this causes flexing of the panel, which converts the sound energy into heat; then, INSIDE the trap, the moving air caused by panel flex gets restricted in movement thru the insulation, causing MORE sound-into-heat losses. If the front panel is allowed to touch the insulation, it dampens the vibrations and lowers absorption; it also widens the "Q" of the trap, making it more broadband. Perforated panel traps is just another name for a perforated Helmholtz absorber - all these should have the insulation up against the surface where the holes or slats are located; this minimises ringing of the slats or front panel, broadens the absorption frequency, and acts as part of the "acoustic resistance" by increasing the inertia of the air within the holes or slots - the Helmholtz formula in the Acoustics forum here (NOT on the REST of the net, INCLUDING the original SAE site) takes this into account. Resonant traps (panel, Helmholtz) need to be located at points of high sound PRESSURE to work well, but Absorbent traps (rigid fiberglass, rockwool, whether cloth covered or not) need to be at places of higher sound VELOCITY to work best. When in doubt, using broadband absorption is nearly ALWAYS the first thing to do when treating a room - then, if there is still uneven response, and you've done everything possible to locate things away from peaks/nulls, it may be time for tuned traps (generic name for panel traps, Helmholtz, slat/slot absorbers... HTH... Steve

Cheers for the reply Steve.I know that your time must be very scarce. So your answer is most appreciated by me ( and no doubt by anyone who reads this that is in a similar predicament. Another coupla questions for you.... Based on my room dimensions ( which are for now and for ever based on the length of 4.4 metres, again cheers!) I drew up a series of to scale boxes eg 4.4 x 2.71 then made up a same sized box with division lines representing halves quarters thirds fifths etc and overlayed them. I did this for length width and height. Basically creating what I imagineis a map of the standing waves and their positions in my space. Essentially this was a variation of the info in the post "are my speakers in a null" I was thinking of using this as a starting point to find optimum positioning for both myself and my monitors. A is this a mathematically correct thing to put my faith in. and B are the above fractional divisions sufficient?? Coz if so then this seems to be a real nice way to find a starting position using fractions of the room size rather than frequency based divisions. And finally ( for tonight) Is there any sort of way i can exploit the wardrobe at the rear of the room to my advantage. Again cheers Jeremy

First part; divide your room into 2,4,6, and 8ths in all three axes; don't put anything there. This will cover both peaks and nulls of the first 4 harmonics for each axis, axial modes ONLY. (at each of those divisions, there will be either a peak or a null or both.) The smaller the division, the less you'll need to move the speaker (or your head) to effect a change. (Note that 3/8 = 37.5%, very close to the "38% rule" - hence my warnings about being careful on this one) Second part - Sure; just leave the stuff in it, leave the doors open, and voila - nice, deep broadband trap your wife can't object to (other than the doors being open, but that's only necessary when you're using the room) 8) (Just make sure nothing in there rattles; you can use any sort of sweep tone thru your speakers at mix levels to check this) Steve

Biggest thanks Steve. I have done as you instructed/suggested. Now I have only one issue ( I believe) Where/How I sit means my ears are at 125cm. Which corresponds to a Mode of 259Hz on the vertical axis. How much higher do i need to raise the tweeters/myself to avoid this?? Just above this point? Halfway tween this and the next modal point?? BTW amidst all of this...I have discovered my mixes beginning to translate a little better. Again. Cheers.

Your original post mentioned 9 foot ceiling; if so, your ear height is approx. 49 inches, which is exactly halfway BETWEEN null points by my calculations; doesn't seem to be a problem??!? BTW, it's the WOOFERS that need to be kept out of modal points (either peak or null) for flatter response - usually 6-8 inches (15-20 cm) off center, measured from the center of the woofer cone. Tweets are so far above modal considerations that they may as well not even exist for this purpose. They should, however, be aimed directly at (or slightly behind) your head. Keep in mind that these are only AXIAL calculations, and that Tangential modes can be nearly as troublesome; so these are only guidelines, which will almost ALWAYS need some "real world" tweaking for best results... Steve

Steve.. Bro first up. I have been uber busy the last few weeks and as I have no internet at home I havent had the chance to thank you for your help in helping me understand the benefits and the reality of the benefits in treating my room. So Thanks. HUUUUUUUUUUGE thanks. I havent finished just yet but when I do I will post a wee chronicle of what i did right and wrong so That others may laugh and maybe even benefit from your help. Again Thanks jeremy

No prob, Jeremy; been a bit busy lately myself - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=3967 Glad you're getting there, keep us posted... Steve