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In-wall speakers: staging? listening experiences? optimization targets?

Shefffield

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Hello forum,

I'm working on a concept for my next digital DIY speaker. Based on recommendations and listening experience from a friend I am leaning towards an in-wall design.

I aim for highest acoustic quality and don't care much about looks or practical issues. For crossovers, filtering and time alignment I use a gidital suite: www.acourate.com by Dr Uli Brüggemann. This software is already driving my current DIY system (see avatar), so I can just reuse the DAC and amps setup. The main question right now is the general concept and the driver selection.

In trying to avoid early reflections there are only two realistic options: get away from rear and side walls, or merge into the rear wall. The latter makes a system inflexible, but it has inherent benefits.

A major question that I would like to have answered by a more numerous jury is how an in-wall system reproduces the 'staging' or 'room' of a recording. A German DIY hifi magazine developped two speakers some 15 years ago with identical drivers (a fullrange and a woofer), crossed over at the same frequency, one built into a very small tower, the other into a 45 cm wide one. Both got specific passive XOs for flat responses on axis. Measurements looked rather similar for both. However, the listening review stated that the narrow speakers had a narrower, but more precise and deeper 'stage', while the wide speakers had a wider, more opulent, but also flatter and less precise 'stage'.

Can anybody chime in with first-hand listening experience of properly done in-wall speakers?

Cheers,
Axel
 

thewas

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However, the listening review stated that the narrow speakers had a narrower, but more precise and deeper 'stage', while the wide speakers had a wider, more opulent, but also flatter and less precise 'stage'.
That matches also to my past experiences with loudspeakers without chamfered edges or waveguides, guess the reason is the distance of secondary radiation sources which smear the imaging, see https://heissmann-acoustics.de/en/kantendiffraktion-sekundaerschallquellen-treiberanordnun/
 
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Shefffield

Shefffield

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Thanks for your quick reply!

However, I have the feeling it adds to my confusion. Well, to the confusion that the initial comparison by the German magazine started.

Heißmann's claim that edges are smearing the imaging is what I understood as well. That is why I plan to avoid ANY edges. That's my main argument pro in-wall setup - move as close to an infinite baffle as practical.

My setup revolves around a 60" TV mounted to my living room wall. I plan to double up the wall around this TV with a large, flat area, so the result will be a "front baffle" of roughly 2,8 m width and 1,6 m height. Flush mounted into this baffle would be relatively small 3 way speakers. Additional support by an independent subwoofer array is also planned.

Depending on how well I can execute the transition from loudspeaker baffle to TV frame there shouldn't be much that can act as secondary radiation source.

Making a floor standing speaker with minimized edges (rounded contours around the high/mid section with very large radius) seems a lot more demanding.

By the way, in the interest of good beamwidth the planned driver sizes are 20 mm tweeter, 60 mm dome high mid and 16-20 cm cone low mid.
 

thewas

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I think very large (like infinite) baffle reduces the problem of the secondary sound sources as they are later and lower in level.

By the way, in the interest of good beamwidth the planned driver sizes are 20 mm tweeter, 60 mm dome high mid and 16-20 cm cone low mid.
Funnily I engineered 3 years ago wide a radiating loudspeaker with 19 mm & 50 mm domes and 170 mm midwoofer.
 

Dal1as

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Baffle speakers take a lot of planning and room prefab. I'm planning a 7.4.4 system with all in wall baffled/angled speakers but am building the room from scratch.

I will say. I went to a coworker's theater who had the Monolith THX in walls for the front stage in a THX angle style and it was the best front imaging and stage I've heard. He had not setup the rest of the theater though. It was basically 3.4.x then. Sounded amazing with the 3.4 though.

Hence why I'll be traveling that rabbit hole soon. Just a lot of work planning.
 

Inner Space

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Can anybody chime in with first-hand listening experience of properly done in-wall speakers?
Hey Axel - there are two basic categories here, and you need to decide which you're in. Generically, "in-wall" speakers are unobtrusive and concealed, designed for visual appeal first, and sound second. Then there are "soffit mount" speakers, which are super-serious installations capable of much better performance than freestanding speakers, in all the areas you're seeking.

It's the wall that makes the difference. For proper soffit mounting, to get the benefit of SBIR elimination (which is huge), the speaker must "know" it's in a wall, which means the wall must be at least as dense and massive as the existing walls in the room. That probably means bricks, concrete, etc. Done well, it's wonderful. Done halfheartedly, it's really not done at all, because low frequencies simply ignore lightweight construction and act as if the speakers are freestanders set close to the front wall.

So it's a big project - worth doing well, but not worth starting unless you plan on really serious construction.
 

DanielT

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Are you also going to install bass drivers in the wall? Do you know how the inner wall is built, constructed? Wood panel? What kind of rule? Is it stable?

I was thinking of installing speakers in a small summer cottage a few years ago but I came to the conclusion it was too much work, due to simpler construction of that inner wall to get it stable.Attached photos not that summer cottage. Just a few pictures, cross-section of a wall.:)
 

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Shefffield

Shefffield

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Hey Axel - there are two basic categories here, and you need to decide which you're in. Generically, "in-wall" speakers are unobtrusive and concealed, designed for visual appeal first, and sound second. Then there are "soffit mount" speakers, which are super-serious installations capable of much better performance than freestanding speakers, in all the areas you're seeking.

It's the wall that makes the difference. For proper soffit mounting, to get the benefit of SBIR elimination (which is huge), the speaker must "know" it's in a wall, which means the wall must be at least as dense and massive as the existing walls in the room. That probably means bricks, concrete, etc. Done well, it's wonderful. Done halfheartedly, it's really not done at all, because low frequencies simply ignore lightweight construction and act as if the speakers are freestanders set close to the front wall.

So it's a big project - worth doing well, but not worth starting unless you plan on really serious construction.

Clearly aiming for "soffit mounted". But I live in a rented flat (not planning to get old in this region) and can't go crazy on the installation. No concrete then, good old "wood-like" has to do. I plan to use table plates for my prototypes, heavy, dense boards of maybe 160x120 cm².

And this is only for the "satellite" units - no bass here. Steep cutoff around 100 Hz. The table boards are very heavy compared to a rather small and lightweight 3-way setup with 20 mm tweeter, 60 mm dome mid and 1-2 midwoofers of 16 or 20 cm.

Low frequencies are a completely different beast, and I intend to address them in a completely different way. Not decided yet, some tests and measurements might be necessary to find a path. Options on my list are:

1. A bunch of impulse compensated mobile subwoofers. Moving them around in the room would give me a good chance to place all of them at ideal positions for a flat bass response without much EQ. I can still connect each unit to its own filter/DAC/amp channel and apply individual room correction to correct the last issues.

2. Wall subs. Also impulse compensated, so the cones are parallel to the wall (pointing outwards left and right). I could mount three under under the high-mid tables and another three on the wall over them. I might achieve good coupling with this "not so small any more" bass generator. In any case, each sub has its own cabinet and is mounted on the wall independently.

Yes. It's a BIG project. :-/
 

nstzya

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I have a similar interest. In-walls not only would seem to offer several advantages with regard to ultimate sound quality, but they satisfy my aesthetic requirements. I find the visual cues of free standing speakers to detract from the auditory illusion - particularly with home theater. I find speakers looming on either side of the screen to be distracting. Add to this that it has always seemed to me that the problems with room boundaries, early reflections, variable bass reinforcement, etc would all be reduced/eliminated by infinite (front) baffle in-wall speakers. Make them coaxial and you solve the horizontal/vertical orientation issues. And add a back box to reduce the effects of the wall cavity (not to mention of the wall itself) as well as define enclosure T-S parameters. Add free standing subwoofers for the reasons already stated.
 
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Shefffield

Shefffield

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90 mm coax drivers for mid-high above 400..600 Hz are my alternative plan. I'm going to compare them against the mid domes. However, given my 2,5 to 3 m listening distance, I don't expect the vertical dispersion to be that critical. Additionally, I have an attic like living room with a really high ceiling. That reflection is scattered around by two 45° roof surfaces.

T-S parameters do not bother me at all. But it is a nice bonus that cabinet volume is almost unlimited with a large enough wall area covered.
 

Dal1as

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Hey Axel - there are two basic categories here, and you need to decide which you're in. Generically, "in-wall" speakers are unobtrusive and concealed, designed for visual appeal first, and sound second. Then there are "soffit mount" speakers, which are super-serious installations capable of much better performance than freestanding speakers, in all the areas you're seeking.

It's the wall that makes the difference. For proper soffit mounting, to get the benefit of SBIR elimination (which is huge), the speaker must "know" it's in a wall, which means the wall must be at least as dense and massive as the existing walls in the room. That probably means bricks, concrete, etc. Done well, it's wonderful. Done halfheartedly, it's really not done at all, because low frequencies simply ignore lightweight construction and act as if the speakers are freestanders set close to the front wall.

So it's a big project - worth doing well, but not worth starting unless you plan on really serious construction.

I agree except 3/4 MDF or double drywall is enough especially when bracing the cavity or using a backbox which makes it even more rigid. Most setups will have the crossover set around 80 hz which gives some leeway but a really good mid-bass transition.
 

dshreter

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My setup revolves around a 60" TV mounted to my living room wall. I plan to double up the wall around this TV with a large, flat area, so the result will be a "front baffle" of roughly 2,8 m width and 1,6 m height. Flush mounted into this baffle would be relatively small 3 way speakers. Additional support by an independent subwoofer array is also planned.
So will the speakers be aimed straight ahead? I believe that in a proper soffit mounted setup the walls angle in so the speakers are aimed at the listening position.

It could still work, but the speakers will present darker than on axis at a minimum. I don’t know what other issues this might cause.
 

Dal1as

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So will the speakers be aimed straight ahead? I believe that in a proper soffit mounted setup the walls angle in so the speakers are aimed at the listening position.

It could still work, but the speakers will present darker than on axis at a minimum. I don’t know what other issues this might cause.
Interesting point. Some people do angled baffles and even curved.

With a speaker that has good horizontal dispersion it may not be needed as much as the baffle wall helps even off axis.

I will be using a THX baffle wall for my front stage with angled baffles although it may not be needed. In fact I will be putting all the bed layer speakers in baffle walls. Not sure about the heights/atmos yet.

The setup I heard and am copying did this using the Monolith 365s and it was amazing. The speakers just dissapeared and the soundstage and sweet spot was huge.
 
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Shefffield

Shefffield

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I'm not going to angle the speakers.
My design is based on the widest dispersion I can achieve. That's why I use 19 or 20 mm tweeters and dome mids. That's why I plan 3 or 4 ways plus subwoofers - to be able to use each driver only in a range where it covers at least +/- 60°, preferably more. That's why I pick drivers with Nd magnets and the smallest flanges I can find, so the whole high-mid section is vertically as small as possible.

I can adjust the desired amount of treble at the listening position easily with my digital XO and EQ software. As long as the tweeters can deliver the desired output under the right angles. A 19..20 mm dome starts getting weaker under angles around 6..7 kHz.
 

tuga

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I'm not going to angle the speakers.
My design is based on the widest dispersion I can achieve. That's why I use 19 or 20 mm tweeters and dome mids. That's why I plan 3 or 4 ways plus subwoofers - to be able to use each driver only in a range where it covers at least +/- 60°, preferably more. That's why I pick drivers with Nd magnets and the smallest flanges I can find, so the whole high-mid section is vertically as small as possible.

I can adjust the desired amount of treble at the listening position easily with my digital XO and EQ software. As long as the tweeters can deliver the desired output under the right angles. A 19..20 mm dome starts getting weaker under angles around 6..7 kHz.

Dali speakers are designed to produce a flat response at the listening spot with no toe-in (see below, cursor at 45°). Given the increasing directivity of the tweeter this means that its on-axis response will be exaggerated, and also that the side walls will be getting a lot more energy than usual. Unless Dali speakers (or your designs) are used in a very long room and placed in a long-wall setup the early reflection zones will need (serious) treatment.

315DAR8fig06.jpg

DALI Rubicon 8, lateral response family at 50", from back to front: responses 90–5° off axis,
reference response, responses 5–90° off axis.
source: https://www.stereophile.com/content/dali-rubicon-8-loudspeaker-measurements
 
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nstzya

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90 mm coax drivers for mid-high above 400..600 Hz are my alternative plan... However, given my 2,5 to 3 m listening distance, I don't expect the vertical dispersion to be that critical

My comments about vertical orientation were mostly directed at the center channel. If absolute fidelity is important, keeping the LCR in the same horizontal plane is more important than being angled in my opinion. The coax arrangement would allow the center to be as high under the screen as possible - without resorting to the flawed sideways M-T-M arrangement. Also allows for physical coherence to aid your time alignment, etc.
 

sarumbear

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