Effect of an Open Ended Room??

[JBLAddict]

In spending a lot of time (almost obsessive) this past year with room treatments, bass management, speaker position, EQ and so on, I've never read any recommendations on the effects of a listening room that is partially/fully opened at the backend.

Since the entertainment room in most homes does not consist of four closed walls, what generally happens to sound when say a living room (such as mine) opens to an adjacent kitchen or dining room. Is the adjacent room considered part of the room size calculation, are there general expectations of what happens to LF/HF, does this generally increase decrease a need for diffusers/absorbers within the primary listening space, etc

if anyone has liinks/literature on this subject I'd appreciate it.

[1audiohack]

I have been watching to see if anyone would or could dig anything up on this specific subject.

From Don Davis in Sound System Engineering 2006
"Pick up any book with pretensions to knowledge about recording studios and almost without exception the material on the internal acoustics exhibits an enormous void of accurate or useful information. Implied is that all you have to do is add some absorption, with the aid of some devils apprentice with information from the dark domain, and all is well."

From Doug Jones in Handbook for Sound Engineers 2008
"Few of the intelectual tools that work in large rooms can be applied to small rooms. Getting small rooms to sound right involves art and science."

If the current state of the art is incapable of dealing with purpose built small sound rooms without the aid of an experienced acoustician on site to deal with the wild cards, I don't see how one could create an exhaustive work on asymetrical rooms with big holes in them. It is said over and over in the literature that it is less expensive to build a room correctly than to correct the acoustics in a bad one. I don't think anyone is coming to our rescue, I think we are left to our own devices.

So where does that leave guys like us? Sadly knowledge on the subject in the popular press seems to follow The Gas Law of Learning... "Any amount of information no matter how small will fill any intelectual void no matter how large."

What have you done so far and how do you quantify the results?

[jcrobso]

Scientific Wild Ass Guess
I have a living room that on one side has a double wide open door way in to the dinning room.
The bass just flows in to the dining room, at the far end the bass can just shake you. It is just something I have learded to live with.

[Mannermusic]

In spending a lot of time (almost obsessive) this past year with room treatments, bass management, speaker position, EQ and so on, I've never read any recommendations on the effects of a listening room that is partially/fully opened at the backend.

Since the entertainment room in most homes does not consist of four closed walls, what generally happens to sound when say a living room (such as mine) opens to an adjacent kitchen or dining room. Is the adjacent room considered part of the room size calculation, are there general expectations of what happens to LF/HF, does this generally increase decrease a need for diffusers/absorbers within the primary listening space, etc

if anyone has liinks/literature on this subject I'd appreciate it.

Great post - been there! My rig is about where I want it to the point that the room is the limiting element. I have openings on the side (dining room) and in one corner (hallway) beside the speakers. Have stairs in the back. Have moved the speakers all over the room. Fascinating (as Mr. Spock would say)! The best way to deal with it is to sit < 6 feet ft. from the speakers. You can actually quantify how bad it is with an RTA/pink noise - just move the mic around and watch the read-out change. Makes EQ difficult at best. Also, L to R balance floats somewhat. Imagine how strange the reverb must be. I'm gonna run an experiment closing off the hallway next to the speakers. But, I suspect few realize just how goofy their rooms are. Spend hours quibbling about cap manufacturers when the room is disaster. I'd say an RTA is a good tool for starters. But, you know, there comes a point when you need to go hear the band in person. It's just an approximation, great hobby. Mike

[JBLAddict]

I have been watching to see if anyone would or could dig anything up on this specific subject.

What have you done so far and how do you quantify the results?

hard to detail, but prolly no different than the typical process of AVR EQ/bass management, bi-wiring, speaker placement, absorption panels, component changes, changing primary seating position, test DVDs/tones with SPL meter, and....repeat, but mostly SPL and subjective based, rather than any more advanced computer analysis

speaker position and EQ/bass management yielded tangible results.....the absorption panels I can't say I hear a difference or not, and don't have the analysis tools to quantify the effect if any....

[1audiohack]

Sounds like fun. It can however be a long walk in the dark!

[JBLAddict]

Sounds like fun. It can however be a long walk in the dark!

I'm about done messing with these black arts, and getting back to just enjoying music, which can so easily get lost in this hobby....can I get a witness?

the hardest part I think for anyone with this interest, is the inability to try out different equipment in your own setting, so we fall back on endless tweaking of what we have. I would like nothing more than to audition 20 different speakers, cheap and pricey, new and old, in my own listening room, to really know where the price/performance/preference curves intersect and settle on something I can be content with. Since I'm not in the camp of collectors, this is not possible. And I also do not want to be in a parade of buy/sell/buy/sell/ebay/CL/A-gon to get there. Given all I've read e.g. about the Array1400, I could honestly say that if I could audition them at home, spending the 5-7K is a very distinct possibility, but not knowing how much additional audio nirvana I could get over my L7 for 10x the price, just can't take that chance on a limited family budget

[Titanium Dome]

I missed this thread until today.

I have a pretty specific recommendation for open ended rooms: make the open end the front of your system layout. This is by far the best acoustic solution for this situation.

Now, you want to be practical, too? Forget it; it's usually not practical. It's just the most effective.

Why isn't it practical?

1. Your signficant other does not want to see the back of your speakers and TV from the kitchen.
2. It blocks access and egress from open room to open room.
3. If your speakers are rear ported, it won't work well.
4. You have wires going across the floor.
5. You'll need both absorbers AND diffusers on the back wall.
6. If you were planning on using a projector and screen, you'll have an achitectural challenge mounting the screen.

This is an older picture, but it shows what I mean. The living room behind the Performance Series MCH system is two steps up from the family room, giving me a more natural break, but it's otherwise wide open.

[Titanium Dome]

Okay, so I gave the potential problems, but why is this such a good solution?

1. It eliminates virtually all reflections from the front wall because... there isn't any wall!
2. It reduces or removes the need to do any sound treatment at the front end.
3. It directs the sound into a controlled space rather than into an uncontrolled space.
4. It gives more symmetry to the set up, making it easier to manage.
5. It directs the sound into the room where you want it rather than into places you don't want it.
6. It gives your calibration software a chance to get a consistent measurement.
7. It can increase the apparent volume in your listening space while not increasing it in the rest of the house, except for the LF material, whose long waves are going to get out no matter what you do.

[Titanium Dome]

In the picture two posts above, there are a few things to comment on.

• I intentionall put the couch in the living room with its back to the front speakers in the family room. This provides additional absorption and virtually eliminates any secondary reflections from the back wall of the living room.
• My goal is this case is to create as open a space as possible with minimum aesthetic impact. To the right of the right front speaker is a glass patio slider. Oh no! Potentially too strong a first reflection! Fortunately, the EOS Waveguide of the PT800 virtually eliminates this, especially now that I've toed it in a bit and moved the fronts slightly closer together. A nice full-width sun shade dropped over the glass breaks up any addtional refelctions.
• There is no wall to the left, as that opens to the kitchen and dining room. No reflections there!
• I moved the HTPS400 sub from the right front corner to underneath the center table and placed a second HTPS400 under there as well. At the same time I moved the elctronics onto a table where the HTPS400 is in the picture. This really added a lot of slam. Perhaps a bit too much?
• A week or so ago, Grumpy and a couple of AVS buddies came over with a BassQ unit and we messed around with two front, two rear, and four subs. After all was said and done, we didn't really need the BassQ unit, as Grumpy's measurements confirmed that the four subs--the two in front and one in each rear corner were excellent for the space. The BassQ added virtually nothing to improve that. I was a bit surprised that four subs worked so well in a room with basically only two full walls.

[JBLAddict]

TD, thanks for all the insights, as you've stated, there are many challenges with reversing the room order, so I am in fact stuck with a near open ended room.

The room does have one partial back wall 4ft wide of the 13 ft room width, so there is some reflection back. That said, do absorbers behind the speakers become useless in creating the traditional dead end, if there's little back wall reflection?

[Titanium Dome]

do absorbers behind the speakers become useless in creating the traditional dead end, if there's little back wall reflection?

No, not at all. The general principle of eliminating front wall reflections (of everything above LF) still applies. Obviously, if your speakers are rear-vented, it's with the expectation there will be some kind of boundary reinforcement of the LF. With sealed cabs and subwoofers, this is not an issue.

As for diffusion, You can still work some diffusers into your side walls. As for the back, there's no way to convert a big hole into anything other than what it is: a big hole. At least it will allow the LF waves to run free their entire length out into the next room...

[jblsound]

I found that I liked having a hole directly behind the seating. In the case of my last house, the 8'-8" x 7'-0" archway was 7 ft behind the main seat. There were 4 hard wall corners in that room. But then the sliding doors of the archway were inside their pocket walls there was no reflected sounds off the center part of the rear wall anywhere near ear level.