Building Floor Standing Speakers into a wall

[lovinthehd]

What's wrong with an IB Sub?

IB subs can be great, if there's a room behind it you can sacrifice for the necessary volume (and the sound that will be transmitted in that room)....and figure out location and all that good stuff.

(OP--IB subs are infinite baffle subs)

 

[snakeeyes]

RBH has a in wall sub. Not sure what it’s price is.

 

[AcuDefTechGuy]

RBH has a in wall sub. Not sure what it’s price is.

The RBH SI-1010 is the in-ceiling sub. The in-wall sub is the SI-10.

I think Gene has a couple of RBH SI-10 in-wall subs.

@ParadigmDawg has the SI-1010P in-ceiling sub.

 

[snakeeyes]

The RBH SI-1010 is the in-ceiling sub. The in-wall sub is the SI-10.

Isn’t there also a in-wall wife option too? LOL

 

[ryanosaur]

Isn’t there also a in-wall wife option too? LOL

I was gonna post an image of a Glory Hole.

DO NOT (do) google "glory hole."

 

[AcuDefTechGuy]

Speakers designed to be free-standing on the floor have baffle-step compensation (BSC) built into their crossover network. It's a type of equalization. If they are placed close to a wall, or flush with a wall as the OP proposes, they will sound too bass heavy.

So if the OP installs the freestanding speakers into the wall, the bass level will be too boosted, like 6dB or more?

Will the midrange and treble also be boosted?

What other adverse effects can we expect?

 

[TLS Guy]

So if the OP installs the freestanding speakers into the wall, the bass level will be too boosted, like 6dB or more?

Will the midrange and treble also be boosted?

What other adverse effects can we expect?

No what will be boosted by about 6 db will be frequencies below the transition frequency which depend on the width of the baffle. So for most speakers the transition frequency falls in the 400 to 600 Hz range. The boost in the wall reflections was much lower, below 80 Hz, and the fact that the sub was in wall contributed to that. Anyhow crossing at 40 Hz turned out to be a good solution. These in wall systems get scant attention in terms of study. Manufacturers produce scant or no specs, and certainly not the measurements I did.

I think there is potentially a lot of need for these systems as they can solve a lot of domestic and practical problems. My wife loves the system that I made for her. If I ever had to do another, I would definitely make it an active system. If I were to design an all out, no holes barred reference in wall system, it would definitely be active.

 

[AcuDefTechGuy]

No what will be boosted by about 6 db will be frequencies below the transition frequency which depend on the width of the baffle. So for most speakers the transition frequency falls in the 400 to 600 Hz range. The boost in the wall reflections was much lower, below 80 Hz, and the fact that the sub was in wall contributed to that. Anyhow crossing at 40 Hz turned out to be a good solution. These in wall systems get scant attention in terms of study. Manufacturers produce scant or no specs, and certainly not the measurements I did.

So if the OP installs freestanding speakers (Q960) flushed into his walls, the frequencies below 80Hz will be boosted by about 6dB. But the higher frequencies above 80Hz will sound pretty much more or less like usual?

 

[TLS Guy]

So if the OP installs freestanding speakers (Q960) flushed into his walls, the frequencies below 80Hz will be boosted by about 6dB. But the higher frequencies above 80Hz will sound pretty much more or less like usual?

No you still have it wrong. The frequencies that will be boosted will be those below the transition frequency. That is determined by the width of the front baffle. If it is a narrow cabinet that will be those frequencies below 600 Hz, if it is a bit wider, those below 400 Hz or so. However most likely the frequencies below about 100 Hz will be boosted more. Obviously when I designed my in wall speakers I did not add BSC to the crossover. However I found reinforcement of the lower bass, below 150 Hz or so was an issue, because the wall is a large front baffle.

Here is the FR of one of my left/right in wall speakers, measured flush with the wall. The sub is silent. Now bear in mind, there is no BSC in the crossover, because it is in wall, so that solves the lower/mid bass problem, until we get to 150 Hz and then the wall starts to cause cancellations a reinforcements. Now these a small sealed cabinets with a couple of 6" drivers. Out of the wall the bass roll off starts at 80 Hz, their -3db point free standing is 83 Hz. But this is what the wall does to the low end response.

So you can see that bringing in the sub at 40 Hz helps prevent make the problem worse.

This is the FR of the 10" in wall sub with the low pass at 80 Hz. That has some wall reinforcement at 40 Hz.

Here is the family of responses of the total system all four speakers sounding, crossover set to sub at 40 Hz in the far field. This positions include, all the seated listening positions, but also in the dinning room. The green trace, is way off axis in the kitchen at the cook top where the left main speaker is totally shielded from view. The HF declines with distance as it should.

So as you might imagine, the system actually sounds very good, as in most of the room the key mid band response is very flat out into the far field.

It certainly was a better performer than I imagined it would be when my wife demanded, yes, that is the right word, the creation is such a system. This was the toughest design challenge I have had for many years.

These graphs at least show the issues you can encounter in an in wall system. The most important thing about the system is that dialog is very clear and natural.

 

[AcuDefTechGuy]

The frequencies that will be boosted will be those below the transition frequency...

...the key mid band response is very flat

If the OP were to install his KEF Q950 flushed into the wall, what will be the estimated Transition Frequency?

 

[TLS Guy]

If the OP were to install his KEF Q950 flushed into the wall, what will be the estimated Transition Frequency?

The transition frequency is the point where the speaker changes from monopole to omni pole. So above the transition frequency the speaker radiates forward, below the transition frequency it transitions to radiate in all directions equally and so is omni-directional. So this means the forward radiation has to be halved. So unless this is taken care of in the crossover the speaker will sound thin. The only way to do this with a passive design is to drop the impedance. This is why amps that can not handle 4 ohm loads are not really fit for purpose.

Now speakers are designed to be free standing, unless specifically designed for another application.

Now if you take a free standing speaker with BSC in the crossover, then the speaker will be a forward radiator only, it obviously can not transition to being an omni- directional radiator. The wall prevents that. So if the speaker with BSC is placed flush with a wall, then the BSC compensation will cause a rise in output forward below the transition frequency. That is elementary logic.

Now the KEF Q950 has a front baffle width of 9.6". So the forward radiating F3 point without baffle step compensation calculates out to be 475 Hz. So if the speaker is placed flush with a wall the response will rise by the amount BSC boosted the response below that transition point.

The dips and boosts due to reflection from the wall are a much different issue, and not easy to predict. That is where you need to measure. But there are two separate issues facing the designer of an in wall system.

The issue of BSC in speakers is a difficult problem and the principal reason why speakers can be so difficult to place and sound so different, in different rooms.

The calculation is based without reference to the room. I can confirm that BSC does ideally need to be adjustable. So that is why I made the BSC of my front three speakers continuously variable. It takes an active design to do this. Not only that, but the BSC is handed to the top 10" driver in each of the mains, and also blended with the sub/LFE signal. In the center the BSC is handled by a separate driver from its own amp. This off loads the drivers that would otherwise be burdened with the added power required for BSC.

I can confirm that the BSC setting for the speakers are very different between the old room and this new room.

The surrounds which are my old location monitors dating from 1984, are passive but have two settings for BSC. I did this because of being on location in a lot of different rooms. The rear backs, are able to have the BSC altered by virtue of the placing of the active crossover, and were designed to be in shelving but come out proud of the shelving.

The take home of all this, is that the DIY designer constructor can design for application. This in fact gives the home designer a huge advantage over the commercial designer. I really mean that advantage is a huge chasm, as speakers are designed for the space and adaptable to new ones.

 

[AcuDefTechGuy]

Now the KEF Q950 has a front baffle width of 9.6". So the forward radiating F3 point without baffle step compensation calculates out to be 475 Hz. So if the speaker is placed flush with a wall the response will rise by the amount BSC boosted the response below that transition point.

If the OP installs the KEF Q950 flushed into the wall, the Transition Frequency will be about 475Hz.

Any frequencies BELOW 475Hz (the BASS) will be boosted.

But the frequencies ABOVE 475Hz will not be affected.

Is that pretty much what will happen?

 

[Pogre]

If the OP installs the KEF Q950 flushed into the wall, the Transition Frequency will be about 475Hz.

Any frequencies BELOW 475Hz (the BASS) will be boosted.

But the frequencies ABOVE 475Hz will not be affected.

Is that pretty much what will happen?

I got a lot more than just that from doc's posts.

You're coming across like you would advocate stuffing a free standing floor speaker in a wall? Or am I reading you wrong? I've been known to do that, lol.

 

[AcuDefTechGuy]

I got a lot more than just that from doc's posts.

You're coming across like you would advocate stuffing a free standing floor speaker in a wall? Or am I reading you wrong? I've been known to do that, lol.

No, of course, not. I recommend using In-Wall speakers.

If he can return those speakers, then return them and get in-wall speakers.

I'm just curious to know what would happen in real life if the OP were to do that.

If he were STUCK with those speakers and couldn't spend another dime, what kind of ACTUAL SOUND would he hear?

 

[TLS Guy]

If the OP installs the KEF Q950 flushed into the wall, the Transition Frequency will be about 475Hz.

Any frequencies BELOW 475Hz (the BASS) will be boosted.

But the frequencies ABOVE 475Hz will not be affected.

Is that pretty much what will happen?

Yes, pretty much. There will definitely be a boost below 475 Hz, which will be the inverse of the curve of the BSC correction. You can see from my data that above 200 Hz the reflections don't seem to be an issue. Below 200 Hz wall reflections are causing peaks and nulls. This is a totally separate issue from the loss of the transition zone.

As I said earlier there is a paucity of data on in wall systems. So my data adds to the understanding of the problems. Really cluttering up home spaces with speakers subs and equipment is a huge barrier to domestic harmony, and rightly so. The industry has not done nearly enough to address this issue. To be honest I'm quite surprised that no one so far has waned to duplicate that in wall system to date. As anyone could install that with greater confidence than with anything else out there.

 

[snakeeyes]

Still learning, but I thought volume of room also was part of the equation for calculating Schroeder Frequency. Like could be lower than 400hz in a small room.

 

[AcuDefTechGuy]

Yes, pretty much. There will definitely be a boost below 475 Hz... You can see from my data that above 200 Hz the reflections don't seem to be an issue.

So to make it clear, we are not recommending to anyone to buy freestanding speakers and install them into the walls.

But if (for some reasons) people couldn't spend any more money and all they had were freestanding speakers, what they would actually get by doing this is a boost in the bass region (below the transition frequency is a more accurate description). But the frequencies above the transition frequency would not be affected.

So at the end of the day, will the speakers sound like CRAP?

Or will the speakers just sound like they have a lot more bass?Maybe too much bass for some people?

 

[juseasy]

After reading all of the great comments - I realized that I have no idea what I'm doing!
So I reached out to a home audio installation company. I got a quote from them, it's quite high. I'm just not sure if the sales guy understands that I really need loud music to play in the family room! I tried to get the point across by telling him that currently I have Rockit6 speakers in my bedroom and Cerwin Vega D-9s in my living room.
What do you think about his proposed in wall solution?

1 Paradigm H55-LCR
2 Paradigm H65-IW
1 Paradigm RVC-12SQ

 

[ryanosaur]

It sounds like there is some possible misunderstanding about the use of "Transition Frequency," here.

TLS will correct if I am wrong, but his usage of this is not about the Schroeder Frequency of the room (sometimes called transition frequency), rather it is the point where the soundwaves are not being reinforced by direct reflection from the baffle (as referred to in the article below as Baffle Step Response).

From his post above:

Now the KEF Q950 has a front baffle width of 9.6". So the forward radiating F3 point without baffle step compensation calculates out to be 475 Hz. So if the speaker is placed flush with a wall the response will rise by the amount BSC boosted the response below that transition point.

This is what, if I understand his usage correctly, he is calling the transition frequency.

From Elliott Sound Products:

Baffle Step Compensation

ESP - The Audio Pages. Baffle Step Compensation. How it works, and why you may need it. Includes details of how to build your own.

sound-au.com

 

[mazersteven]

I really need loud music to play in the family room!

You keep mentioning "Loud". It's not about being loud it's about being clear and undistorted with all volumes