How to position your speakers perfectly

[bob_m_54]

My mrs just uses the vacuum cleaner as an alignment aid...

[almikel]

On 02/11/2019 at 10:39 AM, bob_m_54 said:

My mrs just uses the vacuum cleaner as an alignment aid...

mis-alignment aid?

[almikel]

On 01/11/2019 at 6:18 AM, Nigel said:

Yannakout, you left out an important item, the listening position. Just as the diagram above shows one particular freq or wavelength cancelling by the reflection from the wall behind the speaker, the same happens for many more freqs, especially the 3 wavelengths corresponding to the room W,L & Height. Various places in the room have primary and secondary cancellation points ("room modes") coinciding in clusters and you don't want to have your head there else you will be judging the overall sound falsely.

this diagram...

...is describing Speaker Boundary Interference Response (SBIR), which creates peaks and nulls in the response.

The issue Nigel describes above is room modal response, which is different to SBIR, but also creates peaks and nulls in the response.

 

As @Nigel points out, the listening position is just as important as the speaker position for both SBIR and Room Modes.

Changing speaker position and/or listening position can have a significant impact on both.

 

Room modes result from the room size - the room will have resonant behaviour based on its dimensions dominated by primary modes for length/width/height where each dimension of the room = wavelength/2, and then each multiple above ie wavelength/4 etc.

There are plenty of "room mode" calculators available on the interweb

Room modes in "normal" domestic rooms (ie small) have an impact below 250Hz or so, and create large peaks and dips in the room response below 250Hz or so depending on room size.

If your listening position is in a modal "null" you will hear reduced volume at that modal frequency.

Modal frequencies are set by your room size (with some qualification for lightly constructed rooms).

Changing the listening position will move you into/out of modal nulls (most rooms experience a significant change in bass response as you move around the room).

Changing the speaker position has a different effect on room modes - place them at a null and that room mode won't be energised - this is a technique Toole recommends.

 

As frequency increases, room modes and their multiples "bunch up" - large auditoriums don't have modal issues - their primary axial length/width/depth modes are well below 20Hz, and the modes are so bunched up by 20Hz it doesn't matter any more - very different to "domestic" listening rooms where modal behaviour with their peaks and troughs are smack in the middle of the room's bass response.

 

Room  modes can be treated with absorption etc, but below 150Hz or so the treatment gets too large and deep to be practical.

1 or more subs can help a lot to achieve a smooth bass response <100Hz or so.  

Below 150Hz or so I've also found EQ cut effective for room mode issues when the room response is "minimum phase" - the concept of minimum phase is a topic beyond the scope of this thread - suffice to say that IME EQ cut works well below 150Hz or so.

 

SBIR is a different beast than room modal behaviour - IMHO SBIR is a topic that doesn't receive the attention it deserves.

SBIR is based on path length differences between direct and reflected sounds creating peaks/troughs in the response.

An SBIR calculator is on Ken Tripp's site - an SNA member I haven't seen on SNA for ages...

http://tripp.com.au/sbir.htm

 

"Floor Bounce" is a term used to describe a specific type of SBIR, where the reflected sound from a woofer bouncing off the floor combines with the direct sound from the woofer to create a "null" at the listening position.

By mounting the woofer close to the floor you can ameliorate this SBIR effect.

 

The further a speaker or the listening position is from a boundary, the lower the dip/cancellation from SBIR is...

...unfortunately you need a truly massive room and speakers/listening position a long way from boundaries to push the SBIR dip below say 20Hz - muck with the calculators to see for yourself...

 

A bit contrary to the normal practise of having speakers as far from boundaries as possible, if you want to avoid SBIR dips/cancellations smack in the middle of the bass region you can push speakers closer to boundaries and raise the SBIR dip to a higher frequency where absorption may work effectively.

 

IME it's never a good idea to use EQ on SBIR issues - SBIR is never "minimum phase", and you will get sub optimal results by applying EQ - speaker/listening position adjustment and treatment are the best solutions for SBIR.

 

cheers,

Mike

 

Edited November 3, 2019 by almikel

[Pim]

On 01/11/2019 at 6:34 PM, HdB said:

If you want to really learn something about room setups, try Jim Smith's "Get Better Sound" book - it's a direct 'on-line' purchase from "getbettersound.com" - it's still US$38 + postage - also available as a series of DVDs for those people who prefer this way
 

It also has some 'no-nonsense' introductions to "acoustics 101" (beginner acoustics) plus it has a list of specific music and how to listen well (excellent directions on what to listen for, etc)

 

Knowledge is the cheapest upgrade & the benefits last your lifetime.

 

It's great to see the acoustical control panels in use

I too am a member of the 'Jim Smith Get Better Sound' fan club. 

 

There seem to be two camps that I can identify.

1.  Sound stage lovers

2. Tonal colour lovers

 

Jim Smith is in the second camp and so am I. The guy in the Youtube video who says sound stage is the most important thing for him to listen to is missing out in my opinion.

I have a window that's over 6m wide, 2.7m high with a bar at 1.1m. In the building stage of the room, when the insulation was done and before the gyprock went up, I set up a pair of KEF LS50W on the bar. So there was nothing behind them and everything in the room they were pointing towards was super damped. It wasn't hard to get the most incredible sound stage I have ever heard in my life, from any system in any room. It was so good it was spooky. The music hang it the air like nothing else and even though I could see the speakers, I couldn't identify the sound coming out of them. 

 

You would think I was thrilled.

 

I was thrilled with the accomplishment of creating this incredible sound stage but there was something much more important missing; Tone. Nothing sounded like it's supposed to sound. There was no body to voice or instruments. It didn't sound real.

I'm sure this could be fixed by having much more powerful speakers with better bass. After all, outdoor concerts don't have walls to help out the speakers. But on average I would say setting up your speakers to get the best tone is more important than sound stage in a home setup. 

 

Jim Smith mentions he keep track of the triangle he ends up with after he has set up speakers for his customers and he's come to an average of I believe an 83% (could be 87%, I don't have the book here) width to distance ratio. So if the speakers are 10m away from you ears, they would be 8.3m apart tweeter to tweeter. This is an average, not a rule.

 

I've tried Jim's method in my old room (the new room has 'special' issues) and I found there actually was a point where the tone was best and the sound stage actually became pretty good too. But nothing like that time when I set the KEFs up in the window.

 

There's a lot more in Jims book and I urge everyone to give it a go. It changed my viewpoint of what can be accomplished with a system forever. Even to the point that whenever I listen to some other systems made up of much better equipment than mine I always conclude that mine sounds better, more natural and real.

[almikel]

On 04/11/2019 at 2:00 PM, Pim said:

There seem to be two camps that I can identify.

1.  Sound stage lovers

2. Tonal colour lovers

at least one more camp   :

3. Bass nuts (which I'm one of) - those that enjoy smooth tight bass  - depending on taste from cavernous (<20Hz) up to 250Hz or so

 

IMHO if you get the room bass right, you're 80% done - not trivial to achieve - and usually requiring 1 or more subs, EQ and room treatment...

 

...I like sound stage and good tonal colour also...

IMHO both require a speaker with a smooth on and off axis frequency response - so reflections off room boundaries have the same spectral content as the direct sound.

I'm not familiar with the OP's Harbeth speakers so I can't comment on their sound stage or tonal colour...

 

Kudos to Harbeth for not overstating the low end capability of their 110mm driver in the P3ESR...but their cutoff at 75Hz would benefit from a sub or 2...even if their "in room" response reached lower...

 

I was amazed at the depth and weight a single sub added to my system - a well integrated capable sub added to the OP's system would make a big difference.

 

cheers

Mike

[yannakout]

On 01/11/2019 at 7:18 AM, Nigel said:

Yannakout, you left out an important item, the listening position. Just as the diagram above shows one particular freq or wavelength cancelling by the reflection from the wall behind the speaker, the same happens for many more freqs, especially the 3 wavelengths corresponding to the room W,L & Height. Various places in the room have primary and secondary cancellation points ("room modes") coinciding in clusters and you don't want to have your head there else you will be judging the overall sound falsely.

I did address it just not in detail before the numbers started ( avoid problem spots etc etc) I definitely could have been clearer but I thought it was damn long enough 

[Rup]

On 05/11/2019 at 9:47 PM, yannakout said:

I did address it just not in detail before the numbers started ( avoid problem spots etc etc) I definitely could have been clearer but I thought it was damn long enough 

It was, but also very much appreciated!

[Jason_Coch64]

Some great info here guys always good to reconfirm best techniques 

[vivianbl]

I too am a member of the 'Jim Smith Get Better Sound' fan club. 

 

Jim Smith mentions he keep track of the triangle he ends up with after he has set up speakers for his customers and he's come to an average of I believe an 83% (could be 87%, I don't have the book here) width to distance ratio. So if the speakers are 10m away from you ears, they would be 8.3m apart tweeter to tweeter. This is an average, not a rule.

 

What do you then do with the toe in angle?

Do you adjust them so that they continue to point them to your ears.?

[Pim]

17 hours ago, vivianbl said:

What do you then do with the toe in angle?

Do you adjust them so that they continue to point them to your ears.?

The answer to that question and probably all questions is 'it depends', because every room is different. That's what I like about Jim's set up method. It's not a magic bullet approach but more a journey.

 

This is an example of toe in in my experience; Same system, two rooms. In my previous living room we had reasonably ok damping on the walls. I had my speakers toed in to cross about half a meter behind my head. Now we're in a larger living room and we're not done yet with room treatment. There's a full glass wall on one side and a kitchen on the other and there's no way to treat those hard surfaces. So I had to deal with slap echo.

 

My solution, after trying lots of positions, was to have the speakers closer to the wall than where I started. This makes the bass a little bit bloated but because they're stand mounts I needed the extra body that the speakers just couldn't deliver on their own.   This way I didn't have to play as loud to get the same impact so less echo. That was a compromise.

 

I toed them in to point right at my head so there was less slap echo compared to the direct sound. It's not ideal but it works better than with slap echo. That is another compromise.

 

I have a timber floor and we can't have rugs so when I really want to enjoy some tunes, I put one of our two couches (the right one) in from of the speaker. The one on the left already sits in that position as it is. That way there's no reflection from the floor. The speakers are high enough to point over the couches to that works quite well. That's probably the most successful thing I've done.

 

I have a Lazy Boy XXL chair. It's quite high and soft so my head just flops into it. That way I don't get much echo from the wall behind me either.

 

So that's my setup. Yours will most likely be very different. The trick is to identify the problems and know what to do to fix them and that's where Jim Smith comes in very handy.

 

My setup is far from ideal. The old living room sounded much better and I doubt very much that I'll ever get this new one to sound great. I'm planning to turn a spare bedroom into a listening room. That way I'll have total control.

 

Hope this helps.

Cheers,

 

Pim

[almikel]

On 09/11/2019 at 3:45 PM, vivianbl said:

What do you then do with the toe in angle?

Do you adjust them so that they continue to point them to your ears.?

I choose a large toe in angle - my PSE horns are pointed so the throat of the left horn points at the right extreme of the listening couch and vice versa - the axis where they cross is about 1m in front of the listening couch.

This is an approach recommended by Geddes for his speakers, but the theory applies to speakers with a "smooth off axis" response to maintain a stereo image for the listener when they're listening off axis.

 

Anywhere on my listening couch and beyond, I can still hear a stereo image - it just shifts left or right with me...compared to say ESL57's or Martin Logan electros where the stereo image collapses very quickly to one side or the other.

 

I'm not bagging out electros - in their sweet spot, nothing else comes close - Peter Walker was a genius - and don't forget when the 57 came out they were sold as singles because stereo didn't exist...

...the only reason I don't run electros is they're no party proof - I crank my stereo and expect it to survive abuse when someone else grabs the remote and I'm not around...and I've experienced the aftermath next day numerous times when "normal" speakers have also experienced toasted tweeters and woofers etc, but replacing a blown driver is much cheaper than fixing a 57 panel that was pushed to arcing all night long...

 

If I only listened at low SPL then IMHO, the Quad 57 would be the best speaker of all time (adding a suitably integrated sub), and I would appropriate the central listening position and ignore their response outside the primary listening position - at the central LP, they are sublime.

 

cheers

Mike

[vivianbl]

I choose a large toe in angle - my PSE horns are pointed so the throat of the left horn points at the right extreme of the listening couch and vice versa - the axis where they cross is about 1m in front of the listening couch.

This is an approach recommended by Geddes for his speakers, but the theory applies to speakers with a "smooth off axis" response to maintain a stereo image for the listener when they're listening off axis.

 

Anywhere on my listening couch and beyond, I can still hear a stereo image - it just shifts left or right with me...compared to say ESL57's or Martin Logan electros where the stereo image collapses very quickly to one side or the other.

 

I'm not bagging out electros - in their sweet spot, nothing else comes close - Peter Walker was a genius - and don't forget when the 57 came out they were sold as singles because stereo didn't exist...

...the only reason I don't run electros is they're no party proof - I crank my stereo and expect it to survive abuse when someone else grabs the remote and I'm not around...and I've experienced the aftermath next day numerous times when "normal" speakers have also experienced toasted tweeters and woofers etc, but replacing a blown driver is much cheaper than fixing a 57 panel that was pushed to arcing all night long...

 

If I only listened at low SPL then IMHO, the Quad 57 would be the best speaker of all time (adding a suitably integrated sub), and I would appropriate the central listening position and ignore their response outside the primary listening position - at the central LP, they are sublime.

 

cheers

Mike

 

One of the advantages of the 57s I use in my listening room is that I can sit about a metre to the side of the centre listening chair and still have a stable image - because of the type of components of the treble panel construction that John Hall used. Can also use higher powered amps and play louder as well.

 

My other pair of original 57s peak at the central point.

 

Currently use a 18wpc PSE 300B mono blocks that give more than enough in my listening room that is “3/4” dedicated to that function. I’m the only one who operates the equipment in that room! In the past I used to set up different speakers and amplifiers if there was a party!

 

I am getting a very wide and deep soundstage and imaging with the front of the soundstage about a 1m behind the speakers, but currently trying to figure out how to bring the front of the soundstage forward without losing the tone and depth!

 

Have experimented with placing the speakers wide - adjacent to the side wall- brought them forward to 1.7m to centre of speaker from back( behind speakers) wall, various toe ins at those positions etc. The difficulty is there are so many variables to contend with, including where the room treatments are relative to the position of the speakers.

 

The room is 5m by 9m and 2.4m to ceiling Currently, the speakers are 1.5m (to centre of speaker) from the back wall and 0.5m from side wall to side of speaker. Centre of treble panel is about 0.75- 0.80m from sidewall.

Speakers are 2.8m apart from centre treble panels and listening chair 3m from centre treble panel.

 

Only making very small adjustments now, but they make pronounced differences to the presentation.

 

[vivianbl]

I too am a member of the 'Jim Smith Get Better Sound' fan club.   

There seem to be two camps that I can identify.

1.  Sound stage lovers

2. Tonal colour lovers

 

 

I suppose I am striving to achieve both!

When I first moved the equipment into the listening room and used portable acoustic treatments ( polyester/ Dacron) batts to experiment, I found a sweet spot that did both- it was spectacular to see, feel and hear. I wasn’t using measurement as such just moving things around and listening!

 

Unfortunately, I wasn’t doing this as systematically as I should have and did not keep a record of the position of speakers, treatments and other variables. I also read and took heed of all the advice on the net about equilateral triangles, equal symmetry and ESl positioning from Quad Gurus etc. and decided to implement that approach, thinking that should improve things even further.

 

To my chagrin I was not able to achieve that and despite attempts to retrace the original position I have not been able to replicate it. What I do remember was that one of the speakers was not symmetrically placed in relation to the other- one was about 5-10cm closer to the back wall and that one had much more toe in than the other; and distance from side wall was also not the same!

 

On a side note, I recollect an audiologist commenting that my ear canal shape in one ear was different to the other and that also affects the hearing. Not sure if this adds another variable to the positioning of speakers for the “sweet” spot!

 

 

 

[Pim]

21 hours ago, vivianbl said:

On a side note, I recollect an audiologist commenting that my ear canal shape in one ear was different to the other and that also affects the hearing. Not sure if this adds another variable to the positioning of speakers for the “sweet” spot!

 

 

 

Since you are the person who's listening to the system I can't see anything wrong with adjusting it to suit your ears. 

[Rup]

This is all very informative. Thank you all and please do keep the advice coming.

[HdB]

… back again!

 

It was mentioned awhile back about the different effects of room boundaries (SBIR) - what wasn't mentioned was the benefits of using diffusers at some of those boundaries (behind the speakers, for example) and absorbers at the first reflection points on the side walls - this has been mentioned quite a bit elsewhere but it is still worth repeating it again

 

These 2 procedures contribute much more to the 'stereo effect' than anything else - the rear diffusers, if positioned correctly, will increase the delayed indirect sound content (longer than 10mSec) and the side wall absorbers will reduce the shorter indirect sound reflections (less than 10mSec) - these contribute directly to the precision of the stereo image and it's a subject well worth looking into - Room Boundary Effects aren't mentioned much in the hifi press but are a regular discussion in all 'pro-audio' areas

 

As all things are never equal (just a phrase!) there is the reflections off the floor and from the ceiling just to add to the confusion, so just approaching the positioning of the speakers & the listening position by practical moving/turning/tilting the speakers is a lot quicker and you 'learn to listen' rather quickly - actual room test measurements are extremely useful to show how well your system is functioning and to sort out some hidden deficiencies/problems, particularly in the bass/mids area.

 

I've seen quite a few people going to incredible lengths to obtain a reasonably flat freq response (+/- 3dB) at the listening position (particularly via a dsp) but to still find it unsatisfactory for music - controversially, some people (me too!) just prefer a non-linear freq response and this changes with different types of music and also the volume - weird thing, this music reproduction, eh!

[vivianbl]

On 02/12/2019 at 12:18 AM, HdB said:

… back again!

 

It was mentioned awhile back about the different effects of room boundaries (SBIR) - what wasn't mentioned was the benefits of using diffusers at some of those boundaries (behind the speakers, for example) and absorbers at the first reflection points on the side walls - this has been mentioned quite a bit elsewhere but it is still worth repeating it again

 

These 2 procedures contribute much more to the 'stereo effect' than anything else - the rear diffusers, if positioned correctly, will increase the delayed indirect sound content (longer than 10mSec) and the side wall absorbers will reduce the shorter indirect sound reflections (less than 10mSec) - these contribute directly to the precision of the stereo image and it's a subject well worth looking into - Room Boundary Effects aren't mentioned much in the hifi press but are a regular discussion in all 'pro-audio' areas

 

As all things are never equal (just a phrase!) there is the reflections off the floor and from the ceiling just to add to the confusion, so just approaching the positioning of the speakers & the listening position by practical moving/turning/tilting the speakers is a lot quicker and you 'learn to listen' rather quickly - actual room test measurements are extremely useful to show how well your system is functioning and to sort out some hidden deficiencies/problems, particularly in the bass/mids area.

 

I've seen quite a few people going to incredible lengths to obtain a reasonably flat freq response (+/- 3dB) at the listening position (particularly via a dsp) but to still find it unsatisfactory for music - controversially, some people (me too!) just prefer a non-linear freq response and this changes with different types of music and also the volume - weird thing, this music reproduction, eh!

Yes, agree with your suggestions and observations. I’ve been playing around with speaker positioning and have got to a reasonably balanced spot where small adjustments of speaker position are making significant difference, but find that I now have to readjust volume controls each time I change CD or Vinyl. Not sure why that is. Unfortunate, have to do this manually- no remote!. 
 

Also wish I could have a remote control mechanism to move/ minor readjust  the speakers to get the best out each recording!!

Edited December 4, 2019 by vivianbl

[almikel]

7 hours ago, vivianbl said:

but find that I now have to readjust volume controls each time I change CD or Vinyl. Not sure why that is. Unfortunate, have to do this manually- no remote!. 

Each mix on every CD/Vinyl/Flac will have a different volume - don't you change the volume on how loud you want to listen? constant volume should be left in the domain of muzak, not hi fi.

 

I do love a remote with EQ adjustment to dial treble/bass up and down.

 

mike

[HdB]

Yeah, the re-emergence of tone controls plus the 'dialup' added analogue coloration  - it's been a long time coming.  This should evolve into simple or arranged dsp settings, I think - or packages, like in Audio Weaver, for example.

[Satanica]

15 hours ago, almikel said:

Each mix on every CD/Vinyl/Flac will have a different volume - don't you change the volume on how loud you want to listen?

Nope.

 

15 hours ago, almikel said:

constant volume should be left in the domain of muzak, not hi fi.

It should be but we know how that's ended up.

Here's a solution that works well: https://wiki.jriver.com/index.php/Volume_Leveling

[vivianbl]

18 hours ago, almikel said:

Each mix on every CD/Vinyl/Flac will have a different volume - don't you change the volume on how loud you want to listen? constant volume should be left in the domain of muzak, not hi fi.

 

I do love a remote with EQ adjustment to dial treble/bass up and down.

 

mike

In the previous settled speaker position there were specific CD/ vinyl which were considerable louder or softer than the standard position of the volume control, but the majority of the sources were okay at the position- so had to adjust on a few outliers. Now having to adjust in most cases!

 

I don’t get accused of listening to Musac, by family and friends! I like to experience a musical performance

[Rup]

On 04/12/2019 at 1:37 PM, HdB said:

Yeah, the re-emergence of tone controls plus the 'dialup' added analogue coloration  - it's been a long time coming.  This should evolve into simple or arranged dsp settings, I think - or packages, like in Audio Weaver, for example.

talking about DSP how about software like; Sonar works room correction ?

[almikel]

On 08/12/2019 at 2:42 AM, Rup said:

talking about DSP how about software like; Sonar works room correction ?

I've never tried it, and from their website there's not much info on how it works - but it appears to apply EQ based on multiple mike positions, which is good, but costs around AUD$400, and is targeted at studios running a Digital Audio Workstation (DAW), which is likely fine if your source is a PC.

 

DSP (and EQ generally) can do great good when applied well, but greater evil when applied poorly

 

For room correction I prefer to maintain a high level of control over what EQ and delay I apply - using old school IIR EQ (parametric minimum phase EQ) but leveraging the convenience of DSP for implementation - delay is particularly tricky without DSP, and trivial with DSP.

 

IMHO DSP/delay capability is an essential tool for achieving great "in room bass" particularly when integrating 1 or more subs into the system...

 

...if integrating multiple subs - providing you have access to EQ/Delay (eg via a miniDSP HD), and a measurement microphone and laptop -  I'd recommend free tools such as REW and MultiSub Optimizer (MSO), before costly tools such as Sonarworks.

 

If you don't have subs, then REW and a measurement mike is still useful to measure what's going on with the bass in your room...

....and will help you make informed decisions on when and more importantly when not to apply DSP/EQ.

 

Mike

[almikel]

On 01/12/2019 at 11:18 PM, HdB said:

It was mentioned awhile back about the different effects of room boundaries (SBIR) - what wasn't mentioned was the benefits of using diffusers at some of those boundaries (behind the speakers, for example) and absorbers at the first reflection points on the side walls

Absorption at 1st sidewall reflection points is contentious - Toole recommends that sidewall reflections should have the same spectral content (frequency response) as the direct sound from the speaker.

Toole's recommendation is based on the assumption that the speaker "off axis" response is consistent with the "on axis" response.

Toole's definition of a good speaker is a smooth frequency response on and off axis, with the response off axis smoothly falling the further off axis you go.

Placing absorption at 1st sidewall reflection points will always absorb the top end more than the bottom end, so the sidewall reflections won't have the same spectral content...assuming you have a speaker with good/consistent "off axis" response.

 

Typical box speakers (eg a dome tweeter crossing to a cone mid woofer) don't have a smooth off axis response, especially around the crossover where the mid woofer radiation is starting to narrow, and the tweeter has much wider coverage.

Under this scenario sidewall absorption may likely assist in masking the large variation between the direct sound and the quite different off axis sound coming from the speaker and being reflected at the sidewall.

 

On 01/12/2019 at 11:18 PM, HdB said:

the rear diffusers, if positioned correctly, will increase the delayed indirect sound content (longer than 10mSec)

A Quadratic Residue Diffuser (QRD) - as an example of a diffuser - does work by delay, but the delays are minuscule, and the effect is sound waves impacting the diffuser are scattered in different directions rather than reflecting like a mirror.  This can mean that some of the scattered sound reflected from a diffuser hits other boundaries before getting to the listener (increasing delay), but delay is not the goal - maintaining treble in the room whilst reducing comb filtering from strong specular reflections is what diffusers are meant for.

 

Diffusers have their limitations:

• just like absorption, they get big (deep) if trying to diffuse at lower frequencies
• QRD's have a recommended minimum listening distance of 3 x the longest wavelength diffused (lowest ferquency)- sit too close and you will hear "artifacts" from the diffuser as it takes distance for the "diffuse" sound field to develop - not an issue with diffusers on the front wall behind the speakers
• diffusers such as Binary Amplitude Diffusers (BAD panels), don't generate as much diffusion as QRD's, so the minimum listening distance could be relaxed

On 01/12/2019 at 11:18 PM, HdB said:

there is the reflections off the floor and from the ceiling

No contention here - reduce these via absorption or diffusion as much as possible (but if using diffusion remember the minimum listening distance constraint).

A good rug on the floor or carpet between the speakers and the listening position is always recommended.

Ceiling mounted Skyline diffusers are very popular - these are 2D QRD diffusers - the minimum seating distance applies - if sourcing commercially get the specs for the lowest frequency diffused.

 

To determine the minimum listening distance you use the formula:

V (speed of sound) = frequency x wavelength

Use 344 m/s for V

Say the lowest frequency diffused is 3kHz

344 m/s = 3000 Hz x wavelength (m)

wavelength = 0.115 m

Minimum listening distance is 3 x wavelength = 0.344m or 344mm - completely fine for a ceiling diffuser - or a diffuser placed anywhere further than 350mm from the listening position.

 

cheers

Mike

[Southerly]

Unless I missed it scrolling too fast through this thread, no one has mentioned a simple and effective means of precise speaker placement - using wheeled transport boards. I bought mine from the  German discount supermarket chain, Aldi here in France, they cost me €8.99 each, they are also excellent in their intended purpose of moving heavy furniture, each can support 250K. They make it a doddle to move heavy speakers until you have found that sweet spot. If you have a carpeted and wooden floor - see below.

 

I bought mine because the music room has a suspended wooden floor. As the house is rented I cannot use Philips screws to locate the speaker spikes into and this  anyway cannot cure only reduce the bass and detail loss with this type of floor. I intend to keep the speakers on these boards and use some freebe marbles slabs I have on top of the boards . This will definitely improve the sound but of course it also introduces Sod's law I shall now have to make a box to sit my listening armchair on so that the Toningen tweeters are level with my ears.