Ok, here is the current update. Hopefully we are getting pretty close now. The monitors are spaced at 6’9” per Glenn’s suggestion, which puts the focus about 19 ½” behind the listening position. I split the splay walls into two sections to allow me to keep the soffit wall 4’ wide (the best reference I could find from a post by Knightfly short of finding his formula). The top half of the 2nd left side resonator will have an opening face in the stat wall (thanks for tips from Bruce) to allow access to the breaker while still allowing it to function as a Helmholtz trap.
So, we have absorptive trapping on the lower half of the soffit walls as well as on the front and rear walls and ceiling cloud, and Helmholtz traps on the side walls and rear corners.
If we don’t see any potential revisions I’ll be ready to have the HV/AC guy out to look at the site and plans so that I can incorporate his plans into the design.
Thanks again for all of your help and comments.
BF
BF’s Studio Design
Originally posted at johnlsayers.com, topic 9096.
part of the reason is the seating of the listener related to room length as well as ensuring enough soffit space - in your case, you can compute the soffit width based on the low cutoff of the monitor - probably around 70hz. you probably need a 32"-36" wide soffit. and within this you want to place the monitor slightly off-center on a vertical line and at about 42% height of the room. that said, much depends on other factors such as monitor power, etc. and as with any calculation you can deviate from reality... :-)
here's a link to some information concerning baffle step compensation - basically things to deal with when considering soffit mounting... http://www.quarter-wave.com/General/BSC_Sizing.pdf
and of course you have limits on width etc... so 6'9" seems a good compromise in positioning things WRT soffit mounting and room depth etc.
Thanks Glenn.
The soffit wall as currently sketched is 48" wide. Will it be problematic to exceed the 32"-36" measure you have indicated, or are those intended to be minimum figures?
On the 42% height, I had to flip this figure to 42% from the ceiling rather than from the floor. Due to the limited height of the room (7'6"), 42% would put the monitor well below head level when seated. It seems that 42% from the ceiling, or 58% from the floor will reach the same solution, but please correct me if I am wrong.
The frequency response of the DM602 S3 is listed as 49Hz – 22kHz ±3dB on reference axis, a bit lower than the 70Hz you have assumed. Will this be significant enough to warrant a change in any of the figure that you have suggested?
We are looking to start work a week from today, so I’m probably going to start throwing out questions like a crazy. My intent is to keep everything contained in this thread to avoid a cluttering of posts, but they should all fit under the general idea of studio design. I’m sure there will be more to come, but a few questions are below to start. I would like to thank you all again for your help and feedback.
1) Regarding placement of insulation on exterior walls. Two of the walls outside of the sealed room are concrete block with earth on the far side save for the top foot and a half. Would it be necessary, or would there be no benefit to placing 703 on these surfaces save perhaps the top two feet?
2) Regarding building into room walls. For the resonator units on the side walls, is there any problem with building a portion of the space for these units inside the wall, where the rear of the wall would be sealed and become the rear of the enclosure, essentially building that portion of the wall as an inside out design?
3) Regarding resonator construction materials. Design sketches that I have seen for resonator enclosures seem to have a theme of using MDF as the rear surface. Is this simply structural? If a resonating enclosure were build into the wall, as in question 2 above, would a rear surface of two layers of drywall sandwiched with green glue be sufficient as the back surface, or would a layer of MDF and a layer of drywall sandwiched with green glue be preferred?
4) Regarding the placement of backer rod in wall construction. Should backer rod in a floor wall joint be placed directly below the hung sheet of drywall with the sheet set on top of the backer rod?
5) Regarding wall or sway braces. One wall of the frame for the interior room will be three inches from the exterior block wall. This room will be a self contained / supporting enclosure. Would it be necessary or beneficial to use something like the Mason Industries wall or sway braces Rod mentions in his book between the frame and block wall? Once framed will the structure eliminate the need for decoupled wall bracing?
6) Regarding isolation of monitor stand. In order to decouple the B&Ws from the floor and structure we were intending to pour an 8” concrete pillar on a 2x4 frame base sitting on neoprene pucks or partition supports. The speaker platform will be affixed to bolts placed into the pillar when poured. I’m having difficulty weeding through the Mason Industries site to find the proper product for this application. Does anyone have experience on this or could suggest which product to use in this application?
Thanks
BF
Ok, I'm not sure if I have wrapped my head around the formula in this document. f3 = 4560 / WB in Hz where WB = width of the baffle in inches. The baffle in my plan is 4', so f3 = 4560 / 48 = 95Hz. Here is the part where I think I am getting lost. This formula is for the design a circuit for baffle step compensation not for calculating baffle size, correct? f3, or 95Hz in this case is then an element used in the calculation of the required baffle step correction, but what is its function? Is this the frequency below which attenuation is required for compensation of soffit mounting? Maybe I'm confusing the purpose of this formula.here's a link to some information concerning baffle step compensation - http://www.quarter-wave.com/General/BSC_Sizing.pdf
After searching knightfly’s contributions post by post I found the elusive formula.
http://www.johnlsayers.com/phpBB2/viewt ... c&start=15 Now if I do the math with the listed frequency response of the 602s of 49Hz – 22kHz ±3dB we reach Wb = 4560/49 = 93.061. Clearly I don’t have room for 7.75 ft baffles. In my search I also foundThe formula for finding baffle width in inches is Wb = 4560/Fo, where Wb is baffle size in inches, and Fo = the low cutoff frequency of the woofer.
http://www.johnlsayers.com/phpBB2/viewt ... mula#40728 The 602 has a 7” woofer. That makes 2’4” of soffit wall on each side of the speaker if possible. Even if I eliminate the splay walls I’m not going to reach this without the woofer being in the center of the wall… which puts us back in the best compromise situation as we have discussed and I have sketched above. The walls bend in from the soffit wall and the soffit face is about half of minimum calculation, so it seems I am going to have to live with a certain amount of ‘horn-loading’ as I don’t see a solution to meet the calculations in the confines of the space.the entire front surface of a soffited setup can be hard, and NEEDS to be exactly FLUSH with the front surface of the speaker box for typically 4 woofer diameters in every direction if possible
http://www.johnlsayers.com/phpBB2/viewt ... highlight= knightfly's 2nd post on this page has the best info I have been able to find on puck requirements and testing if anyone is in need of the same information.6) Regarding isolation of monitor stand. In order to decouple the B&Ws from the floor and structure we were intending to pour an 8” concrete pillar on a 2x4 frame base sitting on neoprene pucks or partition supports. The speaker platform will be affixed to bolts placed into the pillar when poured. I’m having difficulty weeding through the Mason Industries site to find the proper product for this application. Does anyone have experience on this or could suggest which product to use in this application?
Finding the puck that meets 10% compression for your weight requirements seems best accomplished through trial and error on small scale testing.actual range of compression can be from 5-25% - the trade-off is between longevity and isolation. You get better isolation with higher compression, but lose serious lifespan of the material. For this reason, 10% is a good compromise to calculate for.
yes, the formula is for the compensation circuit which is also assuming a "perfect" size for the baffle. realistically, cutting that in half is probably correct. so if you're finding the calculation is 7.75' then about 3.875' should work. since you're plan is 4' then you should be good... the key thing to remember is you don't have an ideal space to start with so everything is going to be more about compromise and avoiding commonly made errors rather than creating a fully optimized design...
the 42% is a guide - its 42% of room height and the intended goal is to avoid placing the speaker (fully) in a null location. so from the ceiling or floor should work - although you have to consider listener height - if the speakers are placed significantly above the listeners ears, you'd probably want to angle them down - which requires more design... :-)
as far as insulation goes, you should insulate for several reasons - conservation of energy, code requirements, and damping of resonance on wall constructs. so behind slat resonators and other trapping treatments, using something like mineral wool or 703 will be effective, or even pink insulation. on absorber treatments, you'd want the higher density material to be effective on low end and slightly less dense for trapping higher frequencies.
in wall construction, the pink insulation will be fine - i wouldn't differentiate between the types used when the wall is backed by the block or framed wall. the insulation isn't going to be the determing factor for isolation...
I would like a little clarification on corner resonator design.
The DIY wall units page here shows two vertical layers of bats placed in the interior of the enclosure, with airspace in front of, between and behind, faced with horizontal slats on the front.
Rod's book shows a single layer of bats right against the face covered by vertical slats.
And to add another option (I couldn't find it again, but swear I saw it here) someone stated that if you could afford it, to stack layers from bottom to top of cut bats to fill the entire interior of the resonator enclosure.
Are all of these options 'right'? What is the difference in performance if so?
i'll add an opinion - if the insulation is directly pressed against the front slats (or cloth) you may lose some efficiency so if your construction of the corner slats causes contact, keep it light as you want to get the air into the resonator chamber and through the insulation. as far as adding a second row of batts, or "super chunking" it, some of the effectiveness (or lack thereof) will be due to the slot widths, slat depth, and amount of space behind the slats. thinner slats or widers slots will tend to allow more bass or air flow through so more insulation is probably desirable to provide more trapping.
Construction started this morning. Started a build thread.
Thanks for all of the help so far.
BF
Ok, I'm not sure if I have wrapped my head around the formula in this document. f3 = 4560 / WB in Hz where WB = width of the baffle in inches. The baffle in my plan is 4', so f3 = 4560 / 48 = 95Hz.here's a link to some information concerning baffle step compensation - http://www.quarter-wave.com/General/BSC_Sizing.pdf
Now this information might be relevant, although I'm wondering if I should take it at face value based on your comment gullfo. I am trying to find the cut point at which to apply the shelf for baffle compensation. Based on the calculation above that would make it 95Hz. However if this formula is based on the assumption of a perfect baffle width, how would I modify the formula to work with my actual baffle width? Some adjustment to the 4560 figure perhaps? But I'm not sure where this figure comes from, nor does it seem to be explained in the linked article. I appreciate the help.yes, the formula is for the compensation circuit which is also assuming a "perfect" size for the baffle. realistically, cutting that in half is probably correct. so if you're finding the calculation is 7.75' then about 3.875' should work. since you're plan is 4' then you should be good.