[rasputin6948]

Hey folks!

I am currently building a dedicated home theater in my basement. The middle of the basement against one wall is where the hvac equip and water heater is so it will be enclosed with a wall. on one end it is a rectangular finished room with the hvac wall as one side. I am recessing the rptv into it. Would it be a bad idea to recess the floor standing speakers too? They wont have their own enclosures but it will be cut out and molded around. I would possibly then use some kind of fabric to cover the opening and weatherstrip around the edge of the speakers. I am also doing this with the center channel over the tv. What do you guys think. I am trying to prevent as much of the sound from the hvac ecaping as possible.

 

[PAP]

Why are you recessing anything? TV, maybe ok. Speakers - bad idea.

 

[BasementBob]

Recessed is bad.

Big enclosures is bad.

Baffled with EQ to reduce the bass may be good.

 

[rasputin6948]

Thanks for your replies! I am recessing the rptv right now. It is just an open hole cut out in the drywall. What should I do with the center channel? I was going to cut a hole and recess that. Could you guys explain to me about the negatives of recessing speakers? Thanks.

 

[REDBULL]

I am curious about this too. There has to be a decent way to 'hide' floorstanding speakers. If not, I have some rethinking to do!

 

[Rutgar]

My instinctive response would be that recessing floor standing speakers in ANY situation would be a bad idea. However, I notice that many of the HT's on this forum "hide" the main speakers. But, I suppose those designs don't utilize large, hi-end floor standing speakers.


I'd be curious as to what the designers and acoustical engineers in this forum think, and how they deal with this issue in their own designs.

 

[PAP]

They hide them by building an acoustically transparent screen in front of them, not setting them into a wall.


You didn't answer the question - why are you recessing anything at all? Looks? Need the extra room? Thought it would be neat? Why?

 

[Rutgar]

Hi Pap, building an acoustically transparent wall in front, would definiately be better than putting the speaker in the wall. But, since most floor standing speakers benifit from being out away from the walls, wouldn't that still be a bad idea?

 

[PAP]

If you deaden the wall behind the speaker then high frequency reflection is diminished. The "wall" in front does not have any effect - yes it's ideal to have speakers a few feet out from the walls, but in many HT that is not possible due to space. Certainly better than recessing them however.

 

[Rutgar]

Quote:

Originally posted by PAP yes it's ideal to have speakers a few feet out from the walls, but in many HT that is not possible due to space.

I'll agree with that! In most HT's, if you placed the mains where conventional wisdom says they should go, then the speakers end up blocking part of the screen.

 

[nirvana_av]

First of all if these speakers are ported in the back, you should not enclose them in any kind of cabinet or box.


Unless speakers are designed to be enclosed within another enclosure or cabinet, performance will suffer. Speakers are designed with respect to the baffle or speaker face size. By enclosing them, you are changing the baffle size and the speaker will not perform as designed. Now some manufacturers offer switches that adjust the speaker crossover to accommodate placement within an enclosure. I believe Atlantic Technology is one speaker manufacturer that offers that feature in their mid and high-end speakers.

 

[Rutgar]

My Aerial Acoustic 10T's are ported in the back, and probably would suffer severly from being enclosed. However, my center channel (Aerial Acoustics CC3B) has the adjustments you're talking about, thus allowing it to be placed inside a cabinet.

 

[nirvana_av]

Quote:

Originally posted by Rutgar My Aerial Acoustic 10T's are ported in the back, and probably would suffer severly from being enclosed. However, my center channel (Aerial Acoustics CC3B) has the adjustments you're talking about, thus allowing it to be placed inside a cabinet.

Aerial makes some very well designed and crafted speakers. I'd like to get a chance to hear them some day soon. Their Theater Wall is a very clever idea.

 

[BasementBob]

PAP

Quote:

yes it's ideal to have speakers a few feet out from the walls

That might not always be true. LF tends to wrap around speakers energetically. So having the speaker out from the wall will create a LF time delayed reflection (SBIR) off the wall behind the speaker, doubling the complexity of the wave in the room relative to a room with a speaker in the wall.


On the other hand, Definitive Technology seems to think that the sound stage is better with those reflections, but at least by having tweaters aimed at the front wall (bipolar) the tembre shift should be smaller than a monopole speaker.

 

[Eric Desart]

Quote:

Originally posted by BasementBob PAP That might not always be true. LF tends to wrap around speakers energetically. So having the speaker out from the wall will create a LF time delayed reflection (SBIR) off the wall behind the speaker, doubling the complexity of the wave in the room relative to a room with a speaker in the wall. On the other hand, Definitive Technology seems to think that the sound stage is better with those reflections, but at least by having tweaters aimed at the front wall (bipolar) the tembre shift should be smaller than a monopole speaker.

I think that is and will remain an ongoing discussion.


Every early reflection will cause a time delay. If you have enough of them they will smooth one another out.

What about the floor how do you build in speakers in the floor and wall simultaniously.


The multiplicity of reflections can as well be supportive.


And flush mounting causes often need for electronic correction (limiting boosting bass).

For me there are as valid arguments for both approaches.


Kind regards

Eric

 

[PAP]

There is no time delay - standing waves occur in response to reflection points which are room and speaker placement dependent. Low frequency modes will not be affected by recessing the speaker, but high frequency smearing due to edge reflections will be awful.


The very existence of room modes is in itself due to the reflection in all directions of bass frequencies - remember they are generally omnidirectional. That is why downfiring subs sound no different than forward firing ones.

 

[Eric Desart]

Pap,


This are linguistics.

Boundary interference is related to path lenght difference. So the wave arrives later at spot x causing a phase shift which can differ from minus infinite to + 6 dB and anything in between.

What Bob and I referred to is boundary interference.


Standing waves occur not because because of reflections in all directions, but because the speakers exite room modes. The only thing that's important is the coupling between the speakers and the modes. So not directionality or lack of is important but the position of the speakers within the modal pattern.

 

[BasementBob]

Eric

Quote:

What about the floor how do you build in speakers in the floor and wall simultaniously.

That's cute! I hadn't thought of that, from a 'baffle' perspective.


For my room the floor ceiling plan is absorbtion.


I usually think of modes as they relate to subwoofers, because as far as I know that's usualy the frequencies of the modal issues. Here I've been thinking of front speakers in baffles.

 

[Eric Desart]

Quote:

Originally posted by Eric Desart .......... So the wave arrives later at spot x causing a phase shift which can differ from minus infinite to + 6 dB and anything in between.

I like to be exact.


Normally the pathlenght difference, also assumes that the amplitude of both waves will differ preventing the outer boundaries of minus infinite and + 6 dB (so will be somewhat limited).


But that's what I wanted to tell Bob. One has to take multiple paths into account, which means that excluding one of those reflections isn't necessary a good thing. It a matter of how the summation at spot x of all sources (including mirror sources is reflections) behave.


Regards

Eric

 

[BasementBob]

PAP:


in 2d this is what it looks like (but of course the room is 3d as Eric pointed out)

http://www.bobgolds.com/BafflesVsFreeStanding.jpg
Quote:

Figure 4.6(c) and (d) also show a further important point which relates very much to control room acoustics. If the loudspeaker is placed within the room, as opposed to being mounted flush within the boundary, it also sends a wave to the wall behind it, which then adds to the reflections in the room. It can further be seen from figure 4.6(c) and (d) that after the same period of time, the wave pattern is much mroe complex in the room with the free-standing loudspeakers than in the room in which they are flush mounted.