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PostPosted: Tue Apr 06, 2004 6:41 am 
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Here is a basic way to do hangers, I'd vary thickness within a trap area for wider range.

Soffits, stands - what is it you're not clear on, maybe I can help...

And you're welcome, your thread has undoubtedly helped LOTS of people, judging from the view count... Steve


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PostPosted: Wed Apr 07, 2004 2:27 am 
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Hey Steve,

OK, I'm posting a drawing now of how do I or how should hang the acoustic hanger


BTW, I agree. I realize this topic originally started out as the "Floating Floor" thread, but it has also begun to really take on the shape of a complete section, covering all aspects of the entire construction process. At some point, I may go back to the first page and edit a post (if possible) and create links that will jump through the entire thread in relation to the different topics that we have covered here. Especially since we are at the end of page 13 now, just about to go to page 14 in the next post or two. What do you think?

Aaron


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PostPosted: Wed Apr 07, 2004 4:06 am 
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Also, here's another drawing in reference to what I was asking about the inner frame of the soffit stand. Also, looking at the Barefoots design, it doesn't show a completely sealed box. Is the opening of the speaker soffit just open all around? I was originally under the impression that you were to build a "Box" that the speaker was to fit into. But looking at barefoots design, that's not the case.

Now, another question in reference to the front soffit design. Should the entire front wall/soffit wall be solid from floor to ceiling? Or, should there be an air gap, port, or 703 scenario to be used either on top or bottom of the soffit wall?

Looking at John's drawing on SAE: http://www.saecollege.de/reference_material/index.html (under construction/speakers...3rd drawing down), and this almost contradicts what Barefoot has drawn up, or maybe there just isn't as much detail on John's drawing or vise versa. But it does show utilizing the space for bass trapping.

So I'm a little bit at a loss in direction here...

Thanks,

Aaron


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PostPosted: Thu Apr 08, 2004 8:58 am 
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OK, you're getting into places that might be better handled by Barefoot or John - I'll give you my opinions, and try to "rate" each one as to how sure I am and why, but if either John or Thomas argues a point, odds are they're right... Now that we have some "ground rules", and since this also encompasses Construction, here goes -

First, NEVER hang anything with any degree of mass from a resiliently mounted ceiling - its purpose is to isolate, and as such it can only do that if it is properly "sprung" - in other words, a spring (the RC in this case) is ONLY a spring if it is NOT near the ends of its travel. We need to choose things like spacing of RC, gauge (thickness) of the RC, and amount of weight of drywall hung on the RC, in order to optimise this spring function. Hanging heavy MDF from such a ceiling will only screw up those parameters. It would ALSO cause any vibrations induced into the hanger to travel through the suspension device (chain, wire, whatever) and weaken the isolation factor at that point.

That being said, I would tend to build a separate free-standing frame (it could be anchored to the floor, but NOT any sprung wall panels) kind of like a large drum gong stand, and hang the hangers from that using either multi-strand vinyl-coated cable and cable clamps, or chain. You might build something like a miniature "gazebo" frame, with 4 posts and a pair of "ceiling joists" left to right, then put 2x4's spaced at right angles to the long joists, lined up to support two points on each hanger. If you offset each hanger in a herringbone pattern within their cavity, the framing for this "hanger hanger" could get kind of tricky.

If you can't envision this from my description, I'll try to do a sketch - it may take a while (what's new :? )

"looking at the Barefoots design, it doesn't show a completely sealed box." - This one, I'm about 98% sure of -
Using normal (not "naked" drivers) speakers in their own box, if those speakers are NOT soffit, or flush, mounted here's what happens -

for higher than about 300 hZ, sound tends to be directional but it will diffract at the edge of the baffle (the front plane of the speaker box) and "wrap around" somewhat. This can contribute to early reflection problems depending on positioning of the speakers relative to things like consoles, meter bridges and close walls. Some nearfields have their front baffles radiused (rounded edges) to minimise this. Also, setting this type of speaker right on the bridge often worsens early reflections off the console due to the fairly steep angle between speaker and console surface, which often ends up "aiming" these early reflections right at the ears of the mix person. Placing nearfields on stands behind the bridge changes this angle to a shallower one, and may "re-aim" these reflections UNDER your ears and to the rear wall. (a good thing)

For lower than around 300 hZ, sound becomes more omnidirectional so for a free-standing speaker, it will now radiate "full circle", otherwise known as "4 pi space" - Since about half of the lower frequencies are "getting away" (not coming directly to the listener), manufacturers of free-standing speakers build in a 6 dB boost in low frequencies to compensate for this problem. Some better nearfields have a "space selector" switch that lets you decide on the response based on positioning of the speaker relative to boundaries, others don't.

Properly mounting speakers (in their own boxes) in a properly sized baffle extension, forces the lows to radiate in only the forward half of the space, boosting the LF response by about 6 dB and making that internal compensating network (used for free-standing situations) un-necessary.

In order to work well, a baffle extension (the flat area around a soffited speaker) needs to be massive so it doesn't add coloration to the sound (sympathetic vibrations) and it needs to be large enough to force the lowest frequency the speaker reproduces to only radiate FORWARD.

Barefoot put forth a comment on this size requirement some time back, and I've never been able to find it again - something to the effect of a minimum distance (in all directions, but NOT centered)from the woofer of 4 or 5 woofer diameters for a minimum baffle size. As I interpreted that statement, it would mean a baffle that extends FLAT in the EXACT same plane as the front of the speaker box for at least 4 times the woofer diameter in all 4 directions. IOW, if you had speakers with 8" woofers, the baffle should be flat for at least 32" in a radius from the woofer, but assymetrical (more flat space on successive sides, so that any artifacts from the edge of the extended baffle do NOT reinforce each other at the same frequency)

Having splayed walls encroach on this minimum baffle size has the effect of creating a "horn", which tends to directionalize the sound field from the speaker and shrink the "sweet spot" -

Increasing the height (and subsequent downward angle) of soffited speakers tends to increase the likelihood of early reflection problems from bridge and console, so should be kept to a minimum. If the situation allows, you're better off NOT tilting the monitors at all, and putting them with the HF drivers at ear height. Practical considerations (windows, nearfields, etc) tend to force mains to be mounted higher and canted. Just be aware of the problems this can bring up.

Because of the HF diffraction problem, the area where the speaker box baffle ends and the extended (soffit) baffle begins needs to be controlled. First, the speaker needs to be EXACTLY flush with the soffit - not ahead or behind. Second, the gap between the baffle extension and the speaker baffle needs to be kept to a minimum (diffraction) - Barefoot has recommended less than 3/16" if memory serves. The speaker box should NOT touch the baffle extension to avoid exciting the baffle extension un-necessarily.

Loose-fill insulation placed in the gap around the speaker finishes controlling the edge-diffraction effects - if the speaker is in a larger box, the area around the speaker box should be filled with insulation to keep cavity resonances from causing problems.

However, this "soffit box" isn't necessary to the operation of flush mounting - if you could somehow "levitate" the soffit wall so it touches NOTHING, and is hermetically sealed to the speaker box (flush) without touching the speaker box, that would meet all the necessary criteria. Unfortunately, this isn't Camelot :cry:

So, if you were to build massive baffle extensions (soffits, or flush mounts, same thing for this discussion) and then mount your speakers on isolated stands in such a way that they maintained front surfaces in one plane, with the speaker boxes having a small enough gap between them and the soffit face, that woould work.

Now, if you plan on utilizing John's integral bass trapping, things change.

There is a phenomenon of some ported speakers, when pushed near their limits, to reach a high enough air velocity through their ports to cause the air movement to become audible - the term I've seen is "port chuff" - called that because that's the sound you hear when it's happening. It comes on fairly rapidly, because the noise generated by moving air is proportional to somewhere between the 4th and 5th POWER of velocity, so a slight increase in air velocity through the ports would cause a large change in perceived sound level.

Because of possibility of the "chuff" phenomenon extending to other ported enclosures, and because of the non-hermetic seal around speaker boxes (insulation), building a bass trap into a speaker soffit would probably need to be done differently than just a soffit WITHOUT a bass trap incorporated. In this case, a sealed outer box (sealed to the soffit) might be necessary to keep the "port" around the speaker box from exhibiting this "port chuff" problem.

OTOH, if a soffit were to have integral bass trapping with HANGERS incorporated, the hangers might lessen air currents enough to negate the need for a sealed box around the speaker.

Another problem with a sealed box around the speaker is finding a good way to isolate vibration from speaker to the sealed box - remember we're trying to keep the speaker from vibrating the baffle extension, so that part needs to stay decoupled.

As to porting an integral soffit/bass trap, keep in mind that maximum sound pressure occurs at boundaries/corners, so one way to do this would be to leave an opening to the plenum at floor or ceiling level, use hangers inside, and then cover the port with 703 or rockwool in 3 to 4" - since that location would NOT be a reflection problem, you could go with higher than normal density (say 6-10 PCF instead of 3 PCF) - That would lower the effective cutoff frequency of the trap somewhat.

As to the drawing on the SAE site, I think it's mostly the difference in detail level. However, from what Barefoot says about baffle sizes, you would want to continue the plane of the speaker front further away from the woofer before changing the angle of that plane, which would shrink the available space for a trap below the speaker. This could still work if you have enough depth behind the soffit to continue its angle clear to the floor (or nearly) and still get enough volume of space behind the soffit wall for a good bass trap.

Also, the SAE drawing shows no decoupling between the speaker and the soffit box, which would be necessary.

John, Thomas, any thoughts? (assuming you get a free WEEK to read this...) Steve


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PostPosted: Thu Apr 08, 2004 10:30 am 
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I think I just had an orgasm. :shock:


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PostPosted: Thu Apr 08, 2004 10:34 am 
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Thanks for all the great info Steve.. I always completely grasp everything you have to say. You RoCK!
Thanks!
Ron


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PostPosted: Thu Apr 08, 2004 10:44 am 
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"I always completely grasp everything you have to say" -

Ron, I don't see how that's possible - I only understand about 35% of my comments myself... :?


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PostPosted: Thu Apr 08, 2004 11:51 am 
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Ok - there are three ways to mount your soffits.

The first is the simplest which is as per my design at SAE and which we've further updated through drawings posted here in these forums. The idea is to make the whole soffit frame as rigid and solid as possible using double layers of MDF/plywood glued and screwed thus lowering the resonate frequency of the whole structure.

Thomas has added two other variations. His first is the one you are refering to where he has isolated the speakers from the front of the soffit by mounting the speaker onto a platform that is entirely supported by the rear frame of the system so the box vibrations do not transfer to the front of the baffle and are entirely absorbed into the rear frame. i.e as per his soffit mount thread in the speakers forum.

http://johnlsayers.com/phpBB2/viewtopic.php?t=718

The other is to build a speaker support that is attached to the floor and supports the speaker box entirely without touching any of the soffit framing. The best example of this is in Dave Blauvelt's construction here:

http://johnlsayers.com/Studio/Pages/Bluefield1.htm.

As far as the baffle extending downwards - if you look at the SAE design the baffle is set back so as to allow for an absorption front to be added to stop rear of console reflections confusing the issue.

The alternative is to continue the baffle downwards in the same plane as is illustrated here at Masterphonics.

see attached pic.

Finally there is a fourth method, Sjoko's method, where he only built the front baffles and left the rear open.

Image

cheers
john


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PostPosted: Fri Apr 09, 2004 12:19 am 
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John, Steve, Thomas, and everyone else who has helped me on this thread...

A HUGE THANK YOU!!!!!! for all the continued support on all my questions and all the great combined knowledge of everyone here on design, acoustics, techniques, construction, and theories, etc.

These last couple of posts may take a few days for me to grasp, digest, dissect, and absorb every word you just posted. Any questions I have from that, I'll post.

THANK YOU AGAIN! I CAN'T THANK YOU ENOUGH... :!: :!: :!:

:D :wink: 8) :shock: :o :mrgreen:

Aaron


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PostPosted: Sat Apr 10, 2004 2:37 am 
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OK. Let the questions begin again...I'll start off simple (yeah right :) ).

Quote:
That being said, I would tend to build a separate free-standing frame (it could be anchored to the floor, but NOT any sprung wall panels) kind of like a large drum gong stand, and hang the hangers from that using either multi-strand vinyl-coated cable and cable clamps, or chain. You might build something like a miniature "gazebo" frame, with 4 posts and a pair of "ceiling joists" left to right, then put 2x4's spaced at right angles to the long joists, lined up to support two points on each hanger. If you offset each hanger in a herringbone pattern within their cavity, the framing for this "hanger hanger" could get kind of tricky.


Now this is going to get really troublesome, unless I beef this thing up. As you probably know, but I'll refresh the topic. I have now finished (the front) the outer wall on what I call the front wall (where the soffit wall is). It is steel studs / RC1 / 2 layers 5/8" drywall (overlapped at corners, sealed/caulked each layer, etc.) Once I complete (almost done) the rest of the second layer towards the rear, I will then be putting in the ceiling hanging down on RC, inside the outer walls.

Here's the tricky part and the question: Not a problem building the frame. BUT, from what you just explained, the only part of this entire front soffit wall w/ several hundred pounds of weight doing a balancing act, is only supported by screwing it to the floor. I can't attach the framing to the walls and or ceiling. OH Boy! We need to figure this one out quick. Think of it this way, if front wall is angled towards you at the top, all the weight from the 1" ply + 3/4" mdf will make the framing top heavy, (and at some point I plan to hang a large plasma there too). Which conceivably could lean forward over time and come crashing down.

Now, in part of framing this entire front soffit wall, we need to come up with a structural bracing to keep this from happening. Not to mention, having to screw the heck out of it to the floor. Another option or really a question. Look at the 3d drawings I've posted. Between the "Right", "Center", and "Left" Sections of the soffit wall, I was or have been assuming that I would put walls internally on the framing between each section for isolating. I hope I'm on the right track here. This would allow for strengthening the framing of the soffit/front wall system. In other words, a solid wall insulated, and plywood between the 3 sections, plus the bass trap section on the left side.

This ought to get the creative wheels rolling again... :)

Thanks,

Aaron

BTW...still no email notifications on reply's...


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PostPosted: Sat Apr 10, 2004 7:07 am 
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"a solid wall insulated, and plywood between the 3 sections, plus the bass trap section on the left side. " - depends - if the wall behind the plasma "wannabe" is part of your mass-air-mass envelope, attaching anything internal to that and the floor will weaken isolation (not sure how much) - but, if you frame without touching the outer wall, and attach plywood to the frame, and fasten solid to the floor and front panel, that would help brace things. Also, since left, center and right sections meet at angles, they would be supporting each other at those joints. It's mainly at the outer edge of the speaker soffits that would be the problem of tipping over by twisting that wall section.

One possible way to keep this from happening is to build a cage inside the soffit/trap area, resting joists on top to hang your bass hangers on - if you were to build that cage as I marked up your drawing, it would brace the soffit AND support joists for hangers -

Keep in mind that I'm talking from THEORY here, with a fair amount of NON-studio building experience - John may have something much simpler that he's actually built and tested... Steve


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PostPosted: Sat Apr 10, 2004 7:35 am 
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Hi Steve,

I understood the frame portion for the hangers. But at the same time, trying to figure out structure/construction method in which the soffit wall will stay put since I will not be able to attach the floatedwalls/ceiling that's on RC according to your earlier post.

I have another question that popped up during reading the post on soffits. Would you be so kind as to distinguish the difference between: Baffle, baffle extension, soffit, soffit box, flush mount, bezel, speaker box baffle, extended soffit baffle, soffit face, etc.

Using all the different terms, I haven't a clue what you were really describing. :? :? :? :?

As far as the
Quote:
plasma "wannabe"


The company I work for...we're dealers for video too. (Although plasmas are still pricy as a dealer). We just unloaded a 50" viewsonic today for a client. What a beauty.

Aaron


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PostPosted: Sat Apr 10, 2004 8:24 am 
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"Baffle, baffle extension, soffit, soffit box, flush mount, bezel, speaker box baffle, extended soffit baffle, soffit face, etc" -

Baffle, Speaker box baffle, both refer to the front surface of a box speaker, where the holes are filled with speaker drivers.

Soffit box refers to the built-in box in a flush mount system, where you slide your speakers into.

Soffit and Flush Mount, when referring to speakers (not lights) are the same thing - normally refers to the entire construction for flush mounting of speakers.

Bezel is a term used normally in jewelry and watches, refers to a part that surrounds another part - in flush mounting, it's the piece Thomas showed in "clear" material, that you would make specifically for different speakers to fit snugly in the same wall. Kind of a "mounting ring", or a spacer.

Extended soffit baffle - the face of a soffit, held flush with the face of the speaker, that extends the effective size of the speaker's front baffle in order to force the driver into "half space" radiation. This happens when the flat surface the driver is aligned with is too big to allow the lower frequencies to "wrap around", so they must radiate only in the forward hemisphere.

Soffit face - refers to the exact plane on the face of a flush mount system, which should align exactly with the same plane of the speaker being mounted.

Did I miss any?


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PostPosted: Tue Apr 13, 2004 12:43 am 
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Hmmm. OK.

Didn't mean to sound like an idiot when I posted that question. Some I knew, some I didn't. Some sounded like the same thing. Just wanted to clarify for myself and others reading this post.

Thanks.

In the previous post you made, it would make since that because the front walls are angled, that it would help support the soffit wall. Still kind of unsure about that somewhat, especially if all the weight is on top. Looking at Johns soffit design, it appears the bottom half is only something like 703 covered in cloth. Or is there something in front of it(plywood or mdf)? I'll try and post a drawing when I have time to draw it up.

Thanks again,

Aaron


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PostPosted: Tue Apr 13, 2004 7:50 am 
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Well, just went and listened to the JBL LSR6300 series monitors in a 5.1 setup over at Oceanway Studios. The new features w/ RMC (room mode correction) is a pretty cool feature. The room had a 53 Hz spike, and w/ a small adjustment, voila...corrected. Much more variable for tuning in the monitors for you room. I have the original LSR 28's, so I was familiar w/ the sound, but the RMC, sure cleaned up the sound. May have to crossgrade over to these when my room get's finished here soon.

Hmmm...still don't know if I'm going to attempt soffit mounting my LSR's though?? I may just put them on stands, and only soffit mount for 2 mix applications a different monitor? Any affordable ideas?

Aaron


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