SEOS Recommendations for Large Home Theater - Page 2 - AVS Forum
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post #31 of 47 Old 06-05-2013, 10:46 AM
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have you ever seen a speaker measure like that with those dips at around 250 and 350hz on large baffles?

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post #32 of 47 Old 06-05-2013, 10:59 AM
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Yes all the time. Note edge has a 0.5db scale. And as directivity increases the peaks and dips are minimized. Real world performance will be a little different.
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post #33 of 47 Old 06-05-2013, 11:00 AM
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Coctostan, superb post, just killer ...

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post #34 of 47 Old 06-05-2013, 11:39 AM
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I haven't had the opportunity to measure a baffle that large in adequately free space or anechoic. In an actual room those dips aren't an issue because of the other boundaries. They are basically a function of the model assuming a flat abruptly ending baffle. The 20" baffle also doesn't act like that in most rooms unless you are quite far from other boundaries and the baffle and box have no depth. That large dip at 1300hz on the smaller baffle also doesn't look like that in a normal rectangular box with a real driver.

In reality the interactions around 150-300hz become very complex because of floor/ceiling bounce and boundary interactions beyond the baffle itself. This sim was just a baffle sim as though it was in an otherwise anechoic chamber. There are further notches from boundary interactions, especially the rear wall interference.

One step up from a baffle wall is corner mounting so that the drivers are acoustically close to the corner and the corner acts as a horn. Parham has some explanations of what happens with some nice visuals. It also shows the interactions that occur when the source is acoustically between close (<1/4 wl) and distant (>1 wl) http://audioroundtable.com/forum/index.php?t=msg&th=16684

Edit: I should have said the dips aren't a big issue or at least not big enough to warrant skipping the baffle wall IMO. They do exist, but because an actual room is more complex they become difficult to ascertain in reality. The reality is that most baffle walls will be floor to ceiling so closer to 8ft in most cases and the driver won't likely be centered like I did in the sims. The center channel baffle will likely be more like 8' x 8'. The L and R baffles, in the way I prefer it, are angled at 45deg and in the corners. I would actually suggest getting them as close to the corners as possible with a 2-way horn.
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post #35 of 47 Old 06-05-2013, 11:43 AM
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Quote:
Originally Posted by FOH View Post

Coctostan, superb post, just killer ...

Thx FOH, means much coming from you. One of these days I will have my room in a presentable form. You will get a PM. smile.gif
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post #36 of 47 Old 06-05-2013, 03:15 PM
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Quote:
Originally Posted by J_P_A View Post

recommend MDF followed by 2 more layers of 5/8" DW with something like Green Glue between each layer? That's serious, there!

That's what I did to all 5 walls, but I wasn't building baffles, I was doing soundproofing.
It pretty much blocks all sound above 200hz; and 40db or so below that.

The subwoofers still flex the walls though; but at least it doesn't sound like fracturing drywall anymore (like only single layer 5/8's does) tongue.gif

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post #37 of 47 Old 06-05-2013, 06:40 PM
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I'm one proponent of the baffle wall. If you'd like to simulate different sub locations and room surface absorption send me your email address and I'll send you a copy of the "Room Response Calculator". (Couldn't find a working copy with a quick Internet search.)

If you'd like to experiment (particularly for L-R spacing and toe-in) the oversize baffle suggestion is a good way to go.




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post #38 of 47 Old 06-06-2013, 12:51 PM
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Originally Posted by FOH View Post

If I were building, given the space, I'd employ a quasi screen-wall approach on all walls. Somewhat of a faux wall, studs only, covered in fabric and trimmed in wood, so all treatments ... be it massive absorption, or diffusion/scattering, could easily be implemented with no visual component whatsoever. Thick bass damping all around, then layer on diffusion to taste, to retain MF/HF presence and air.[/I]


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I should add, that if feasible, incorporating FOH's approach to the rest of the room is a great idea. I kind of wish I had done that but it does take away floor space. It is very common in no expense spared studios though. It would also, IMO, require professional design and a large treatment budget. It would be very easy to go overboard on absorption which I think is a critical mistake.

Yeah, but honestly, only if one isn't paying attention to the task at hand.

Coctostan, I realize you're well aware of this, but a brief recap may be helpful to some.
Unless you're in a tent wink.gif , essentially, most every room could use additional LF damping. The above example (drastic yes), once implemented, possesses two acoustic environments. The in-room, faux wall surface treatments, are invisible to the big wavelengths. The deep stuff simply diffracts around the scattering/diffusion elements, and the critical range above is retained to whatever degree one wishes to emulate. The subs encounter the entirety of the trapping, the mains encounter the surface elements that either reflect, scatter, or properly diffuse.

Most enthusiasts can't get past frequency response. However fundamental to reproduction is knowing the reproduced sound energy possesses a size component. Many AVS'ers understand this, but it seems as if sound "size", and the significance (and misunderstanding) of the time domain, is lost on many.


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Originally Posted by coctostan View Post

It would also, IMO, require professional design and a large treatment budget.

Required pro design? Not in my opinion, most all the information is readily available. The diffusive/scattering stuff could be hung with perimeter French cleats (disguised as wall trim), ... and easily movable, or removable altogether. That said, it wouldn't be weekend project, but entirely doable.

Large treatment budget? I guess it's a relative term. But the speaker system, the room's acoustic, and the skill and optimization chops of the user, are three key aspects that are inextricably linked to one another. Often we see the room merely get a cursory effort, never fully realizing the system's potential....let's build more subs ... rolleyes.gif


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Originally Posted by noah katz View Post

Nice thing about coax is .... .... has uniform radiation pattern with circular symmetry which helps when listeners are close to the surrounds, as they often are

I think an 8" coax (DIY, Seaton, JTR, etc) is a great idea for surrounds.

Noah is exactly right, and this coaxial symmetry is important. I'm not sure how much so in surrounds (I've not performed those experiments), but in LCRs it's fantastic. As mammoth as my Catalysts are, you can really sit close if need be (quite the attribute in my modest room) .. and the importance of reflected sound and integration is well documented. As Noah stated, when listeners are somewhat close, they'd be a great choice.

I intended to purchase JTR's single 8" coax for my four surrounds. But while in a friends pro audio shop, I encountered a deal on four brand new QSC K-8s, w/these wonderful mounting yokes, so I went all active, all around. 10kw, across 7 channels. Upon receiving the QSCs, I quickly modded them with horn and cabinet mass/damping. They're fine, but I'd suspect either Noah's bespoke surrounds, or another 8" coaxial would outperform them.

Clearly 5 or 7 identical channels is the theoretical ideal. But I used some really tiny (Klipsch 5" two way) surrounds in my previous 5.x system, and in my 25x13x8 room, they performed adequately for quite some time.

Quote:
Originally Posted by coctostan View Post

Thx FOH, means much coming from you. One of these days I will have my room in a presentable form. You will get a PM. smile.gif

I'd love it, ... likewise wrt my modest room when it's a little closer to finished.




PNW, I never tire at examining that image. I clicked on The Octagon, and hit a bad link.



Thanks
J P A, ... all the best

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(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
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post #39 of 47 Old 06-06-2013, 07:04 PM
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PNW, I never tire at examining that image. I clicked on The Octagon, and hit a bad link.


Sorry...changed hosting service intending to update the page, but have been busy with "stuff". It'll be a few weeks.

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post #40 of 47 Old 06-07-2013, 07:51 AM
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FOH-

I will modify my statement to say that a room of that design would require either professional design OR an enthusiast crazy enough to spend countless hours developing the knowledge to understand how to design it properly. biggrin.gif You have knowledge that is on par with many pros and that is not exactly common. I'm not sure I would have great confidence in my own ability to design it without doing lots of post build tweaking. How deep? How diffuse? 1D or 2D? It is unlikely that it would sound worse, but with an effort this big and giving up 1-2ft of floor space at each wall I would want to be very certain of the design's efficacy.

I agree that it is basically impossible to have too much bass trapping assuming the room maintains lively enough in higher frequencies. How you achieve that combination becomes less than simple and there aren't a bunch of easy to follow DIY guides like there are for simple bass traps and panel absorbers. It requires delving into the studio forums and those have slightly different requirements.

The treatment budget, for the design I have in my mind would be higher than the budget to build a full 7 channels of SEOS kit speakers. Much more work too.

I will say that your suggestion does make me want to consider something like that for my room. Of course my wife would kill me, but that's never stopped me before. It is probably the best approach if it is feasible. Hopefully we will chat in person soon. I definitely want to hear the Cat's.
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post #41 of 47 Old 06-07-2013, 10:36 AM
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since it is going behind a screen wall, styrofoam blocks or something could be used to "fill in" between the speakers to create a baffle wall while allowing for easy rearranging if placement didn't work out on the first attempt.

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post #42 of 47 Old 06-07-2013, 10:45 AM
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Quote:
Originally Posted by LTD02 View Post

since it is going behind a screen wall, styrofoam blocks or something could be used to "fill in" between the speakers to create a baffle wall while allowing for easy rearranging if placement didn't work out on the first attempt.

That's not a bad idea. Something I had not thought of and would be great for experimentation.
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post #43 of 47 Old 06-07-2013, 02:09 PM - Thread Starter
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That is an interesting thought. I suppose once you got everything pinned down, you could build a more permanent solution. Although the styrofoam might have the advantage of letting you fill the cavity behind with pink fluffy for bass trapping.

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post #44 of 47 Old 06-09-2013, 05:51 AM
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Questions for FOH or anyone else that wants to chime in!


What kind of treatments and/or EQ would you recommend for correcting things in the "Time Domain"? I have my theater room treated with absorbing panels, (4" OC703 with a 4" air gap) at the first reflection points on the side walls, as well as on the front wall behind the mains. I also have floor to ceiling bass traps, made out of regular pick fluffy insulation that is stacked in the corners. I understand that this fixes issues in the frequency response, but I have no idea on how to change or treat the room in a way that optimizes the time domain? Any suggestions? I would like to hear more discussion with regards to this. If you don't want to muck up this thread, could you guys PM me?
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post #45 of 47 Old 06-09-2013, 02:13 PM - Thread Starter
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I for one would welcome any information you guys can offer on calibrating the room as well. Time domain or otherwise smile.gif

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post #46 of 47 Old 06-10-2013, 04:28 AM
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Bump for FOH or anyone else that could possibly help explain how to treat the time domain portion of this by using either room treatments or EQ?
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post #47 of 47 Old 06-16-2013, 02:30 PM
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I was about to ask the same questions as OP and then I found this thread smile.gif

Would the Fusion-15 Sentinel's still be a good recommendation for a custom theater build that is 32x24 (30x22 inside) ?

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"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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