Busting myths - preaching to the ignorant?
DAH
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#1
27th October 2011
Old 27th October 2011
  #1
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Busting myths - preaching to the ignorant?

I have tried to disprove some commonly spread myths at a local music board (not GS ) but got kinda attacked by local gurus who actually bring these myths to the masses and who claim I have not read P. Newell books without being able to give a quote or a page that refutes my points.
These in are (AFAIK at least) as follows :

1) 8" speakers are a horror in a small room due to standing waves - 5-6'' are preferred.
I propose 8" for rooms from 15 m2 and larger due to less constrained and deeper bass (the audeince there is a hip-hop crowd). My reasons are that 5-6'' will still excite midbass modes so one extra 40-60 Hz mode from 8" is not such a horror considering the horror that will most probably exist in the midbass range already form 5-6'' speakers.

2) some room is required for bass to develope.
My "busting myth" reasons - take any headphones - there is bass. It is a different matter that small rooms with massive rigid walls do not support enogh low modes. A local guru disputed this by:" read Newell and google Missing Fumdamental effect" for bass in headphones, which is obviously stupid since the bass fundamentals such low as 40-30 Hz can be and are measured in headphones.
3) foam pyramides\carpet\eggcraves are good to treat the room as general absorbers\ for early reflections.
My reasons - they are not good at least, and rather harmful.
They only absorb some (narrow) High\Mids ranges though leave low-mids and bass untouched - the room gets imbalanced more than it was before the "treatment" - a dull booming\nulling room will be what we will get as a result.

4) One can evaluate different speakers in different rooms or in one room in different placements.
My reason is that room\speaker in a given spot in a room is a system, and moving speakers a step in any direction in a room will yield a unique response highly affected by the room.
So one cannot say "speaker A (of a given size\design) has more bass than speaker B (of the same size\design as A) - I listened to A in a room X in the corner, and listened to B while standing in the middle of room Y.

5) rear-ported speakers cannot be placed relatively close to a wall.
My reasons - as long as some decent distance (like 4-8'') for free air travelling from the port is left between the wall and a port - it does not matter whether it is a rear-ported or a front-ported speaker in terms of time alignment\resonances\spectral balance since the wave length of the frequencies at which port works is well above 3 meters long.

Then when a "guru" posted all I was talking was bull* and can be disproved for any point, I proposed him to do so where he shut up but then his proponents chimed in with no contrarguments.
Could you guys state whether I am right on wrong?
#2
27th October 2011
Old 27th October 2011
  #2
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Glenn Kuras's Avatar
 

Read it quick but you are right. What forums are these "gurus" on that are saying this?
DAH
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#3
27th October 2011
Old 27th October 2011
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Quote:
Originally Posted by Glenn Kuras View Post
Read it quick but you are right. What forums are these "gurus" on that are saying this?
a Russian hip-hop forum.
Thank you Glenn!
Other pro-guys, please chime in. Just post 1 is right, 2 is wrong etc. So it could be pointed at as my ultima ratio)
#4
27th October 2011
Old 27th October 2011
  #4
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Quote:
Originally Posted by DAH View Post
a Russian hip-hop forum.
Russian hip-hop?? Now that is a new one on me. Kind of reminds me of the Jamaican bobsled team.
#5
27th October 2011
Old 27th October 2011
  #5
Gear maniac
 

hmmm....I am going to post logical responses to your positions although I may not completely agree with what I am going to say but just for arguments sake I will take the other side of your position.

1) 8" speakers are a horror in a small room due to standing waves - 5-6'' are preferred.
I propose 8" for rooms from 15 m2 and larger due to less constrained and deeper bass (the audeince there is a hip-hop crowd). My reasons are that 5-6'' will still excite midbass modes so one extra 40-60 Hz mode from 8" is not such a horror considering the horror that will most probably exist in the midbass range already form 5-6'' speakers.

*Speaker size does not necessarily effect frequency response, there are other factors like crossover design, and voice coil design that do. Is the room "sound proofed" that will also effect the room mode.
Larger drivers really just mean that they move more air. There are 6" speakers that can go as low as 8" ones. So is driver size really the problem?

2) some room is required for bass to develope.
My "busting myth" reasons - take any headphones - there is bass. It is a different matter that small rooms with massive rigid walls do not support enogh low modes. A local guru disputed this by:" read Newell and google Missing Fumdamental effect" for bass in headphones, which is obviously stupid since the bass fundamentals such low as 40-30 Hz can be and are measured in headphones.

*I think a 200hz tone is 2 feet long (or something like that). Obviously if you enclose your ear, the follicles that interpret sound do not need as much space to interpret it because you are taking away the factor of vibrating all the air in the room.

3) foam pyramides\carpet\eggcraves are good to treat the room as general absorbers\ for early reflections.
My reasons - they are not good at least, and rather harmful.
They only absorb some (narrow) High\Mids ranges though leave low-mids and bass untouched - the room gets imbalanced more than it was before the "treatment" - a dull booming\nulling room will be what we will get as a result.

What if the problem is in the high/mid frequencies? Wouldn't some well place absorption help in this case?

4) One can evaluate different speakers in different rooms or in one room in different placements.
My reason is that room\speaker in a given spot in a room is a system, and moving speakers a step in any direction in a room will yield a unique response highly affected by the room.
So one cannot say speaker A of a given size\design has more bass than speaker B of the same size\design - I listened to A in a room X in the corner, while I listened to B while standing in a middle of room Y.

There really is no argument against this, since the room and the room placement is a major factor in its sound you probably want to compare monitors in the same room in relatively the same positioning.

5) rear-ported speakers cannot be placed relatively close to a wall.
My reasons - as long as some decent distance (like 4-8'') for free air travelling from the port is left between the wall and a port - it does not matter whether it is a rear-ported or a front-ported speaker in terms of time alignment\resonances\spectral balance since the wave length of the frequencies at which port works is well above 3 meters long.

*Why do we put bass traps in the corners? Because there are 2 walls near to each other. and each wall is a major factor in room modes....so pumping air directly into the corner seems problematic. In speaker design rear ports are usually done to exaggerate bass response.

I find your positions interesting (and I pretty much agree with them). Why they would not be able to accept your points # 3 and 4 confuses me (there is no real argument against them). Although I actually do think that proper absorption can be handy if used sparingly and properly (which is rarely the case).
#6
27th October 2011
Old 27th October 2011
  #6
3 + infractions, forum membership suspended.
 

Quote:
Originally Posted by DAH View Post
I have tried to disprove some commonly spread myths at a local music board (not GS ) but got kinda attacked by local gurus who actually bring these myths to the masses and who claim I have not read P. Newell books without being able to give a quote or a page that refutes my points.
These in are (AFAIK at least) as follows :

1) 8" speakers are a horror in a small room due to standing waves - 5-6'' are preferred.
I propose 8" for rooms from 15 m2 and larger due to less constrained and deeper bass (the audeince there is a hip-hop crowd). My reasons are that 5-6'' will still excite midbass modes so one extra 40-60 Hz mode from 8" is not such a horror considering the horror that will most probably exist in the midbass range already form 5-6'' speakers.


size of the speaker has nothing to do with standing waves

except that larger diameters can supply lower freqs louder than small diameter speakers eg 36' subwoofer will woof more subs than a 2" speaker.


room shape and size will also affect the results
as will location of teh speakers

2) some room is required for bass to develope.

???? develop?
you can hear bass in headphones with minimal room being the space in your ear and the phone cup.

bass requires movement of air. more volume means more air needed to be moved.

My "busting myth" reasons - take any headphones - there is bass. It is a different matter that small rooms with massive rigid walls do not support enogh low modes. A local guru disputed this by:" read Newell and google Missing Fumdamental effect" for bass in headphones, which is obviously stupid since the bass fundamentals such low as 40-30 Hz can be and are measured in headphones.


3) foam pyramides\carpet\eggcraves are good to treat the room as general absorbers\ for early reflections.
My reasons - they are not good at least, and rather harmful.
They only absorb some (narrow) High\Mids ranges though leave low-mids and bass untouched - the room gets imbalanced more than it was before the "treatment" - a dull booming\nulling room will be what we will get as a result.

???? maybe. not an acoustic expert for treatment.
but my living room sounds great with rugs drapes furniture etc and bare walls ceiling on 3 surfaces.

4) One can evaluate different speakers in different rooms or in one room in different placements.

apples and oranges

My reason is that room\speaker in a given spot in a room is a system, and moving speakers a step in any direction in a room will yield a unique response highly affected by the room.
So one cannot say "speaker A (of a given size\design) has more bass than speaker B (of the same size\design as A) - I listened to A in a room X in the corner, and listened to B while standing in the middle of room Y.

5) rear-ported speakers cannot be placed relatively close to a wall.
My reasons - as long as some decent distance (like 4-8'') for free air travelling from the port is left between the wall and a port - it does not matter whether it is a rear-ported or a front-ported speaker in terms of time alignment\resonances\spectral balance since the wave length of the frequencies at which port works is well above 3 meters long.

???? never had a rear ported one

Then when a "guru" posted all I was talking was bull* and can be disproved for any point, I proposed him to do so where he shut up but then his proponents chimed in with no contrarguments.
Could you guys state whether I am right on wrong?
see comments inserted
i think i mostly agree with you
DAH
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#7
27th October 2011
Old 27th October 2011
  #7
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Thread Starter
Still no quotes, page numbers and section headings in a book by Newel that disproves my points, however the guru demands I post a link to this topic "so we be watching what is that all about".
Rod, Andre, DanDan, SAC (or is he off GS?), John, Jens, Glenn, Sören - please be judges and let the acoustical truth reign the minds)!
I do not mind being wrong at all - it is just called learning, right, but I hate self-confident arrogant ignorance.
#8
27th October 2011
Old 27th October 2011
  #8
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narcoman's Avatar
 

bass in headphones? Well - the really low stuff isn't there is it? But that's more to do with drivers rather than rooms.
#9
27th October 2011
Old 27th October 2011
  #9
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Rod Gervais's Avatar
 

Quote:
Originally Posted by DAH View Post
1) 8" speakers are a horror in a small room due to standing waves - 5-6'' are preferred.
I propose 8" for rooms from 15 m2 and larger due to less constrained and deeper bass (the audeince there is a hip-hop crowd). My reasons are that 5-6'' will still excite midbass modes so one extra 40-60 Hz mode from 8" is not such a horror considering the horror that will most probably exist in the midbass range already form 5-6'' speakers.
I would have to say (first) to define "small rooms"......

I don't define room size by area as much as by volume.

That being said - speaker size has less to do with frequency response (within reason) than it does with the amount of air it moves.

For (just) one example - the PMC Ltd DB1S-AII only has a 140mm (5 1/2") bass - but it's useable freq response is rated at 50Hz-25kHz Peak SPL @ 1M: 108dB, by the way - this is not to say it will not produce lower frequencies than 50Hz - simply that they will not be apparent enough to be usable. You could prove this with any speaker by simply playing sine waves through the speaker beginning at it's rated lowest usable frequency and moving down one step at a time to see what the lowest transmitted frequency really was.

However - You'll always get more of a "thump in your chest" with a larger speaker.

Quote:
2) some room is required for bass to develope.
My "busting myth" reasons - take any headphones - there is bass. It is a different matter that small rooms with massive rigid walls do not support enogh low modes. A local guru disputed this by:" read Newell and google Missing Fumdamental effect" for bass in headphones, which is obviously stupid since the bass fundamentals such low as 40-30 Hz can be and are measured in headphones.
You can't necessarily equate headphones with rooms - so we won't bother going there....... BUT - they are wrong one the face of it with their statement.

First of all - let's look at a very small room......... 13' x 12.38' with 8' ceilings.
(this equates to your 15m2 small room)

Room modes dominate from 43hz to 132hz - but, what happens below that 43Hz?

The fact that room modes aren't supported in the above room below 43Hz does not mean they are not heard.

Heck - the wavelength itself (of the lowest mode) is longer than the largest dimension of the room, 43.5Hz has a wavelength of 26' - yet not only does it have plenty of room to generate - it also creates modal activity (it's an axial mode).

What does they suppose happens with the energy from lower frequencies - does it just go into a magical place and vanish into a huge void?

Tell them to stick a huge woofer in the trunk of a car and run some rap music through it - and then tell you there is not enough room in the car to generate those low frequencies.......

Quote:
3) foam pyramides\carpet\eggcraves are good to treat the room as general absorbers\ for early reflections.
My reasons - they are not good at least, and rather harmful.
They only absorb some (narrow) High\Mids ranges though leave low-mids and bass untouched - the room gets imbalanced more than it was before the "treatment" - a dull booming\nulling room will be what we will get as a result.
Eggcrates (meaning the cartons that contain eggs in stores) are useless for anything other than putting eggs in.

Eggcrate foam (on the other hand) can have some uses, the same goes for foam pyramids - carpet is great for walking on - lousy room treatment.

So, what you say they say is true (with the exception of carpet) - that, is if they are saying what you say they are saying. For general absorption/early reflections these products are fine. There are plenty of things they would not be good for - but those 2 items would not be on that list.

There are also some (very expensive) foams that have properties that can compete with rigid fiberglass or rockwool products pretty much even up.

Carpet sucks on walls unless one like the idea of the potential for runaway fires (should something bad happen).

Quote:
4) One can evaluate different speakers in different rooms or in one room in different placements.
My reason is that room\speaker in a given spot in a room is a system, and moving speakers a step in any direction in a room will yield a unique response highly affected by the room.
It would not be possible to evaluate different speakers by comparing in different rooms - however - the sweet spot in a room may well be vastly different for different speakers.

The true test for different speakers would be to find the sweet spot in the room for both pairs of speakers and (which could be the same spot - just doesn't have to be) then do "A/B" comparisons.

Quote:
5) rear-ported speakers cannot be placed relatively close to a wall.
My reasons - as long as some decent distance (like 4-8'') for free air travelling from the port is left between the wall and a port - it does not matter whether it is a rear-ported or a front-ported speaker in terms of time alignment\resonances\spectral balance since the wave length of the frequencies at which port works is well above 3 meters long.
This would be totally dependent on the speaker I would imagine - always work within the distances recommended by the manufacturer - however - the blanket statement is wrong.

Take the Genelec 8240A - which is a rear ported speaker........ the manufacturer indicates that this speaker can be placed within 2" of a wall surface - within 2" of a corner. They also indicate a maximum distance from the wall for that speaker. Understand that the closer to a surface a speaker is (regardless of the port location) raises the frequency level of SBIR - thus making it less problematic because it is much easier to treat.

I would consider 2" from a surface "relatively close".


I hope this helped,

Rod
#10
27th October 2011
Old 27th October 2011
  #10
3 + infractions, forum membership suspended.
 

Quote:
Originally Posted by DAH View Post
Still no quotes, page numbers and section headings in a book by Newel that disproves my points, however the guru demands I post a link to this topic "so we be watching what is that all about".
Rod, Andre, DanDan, SAC (or is he off GS?), John, Jens, Glenn, Sören - please be judges and let the acoustical truth reign the minds)!
I do not mind being wrong at all - it is just called learning, right, but I hate self-confident arrogant ignorance.

i hate people who read some internet whizdumb and then think they know everything about a subject
#11
28th October 2011
Old 28th October 2011
  #11
Gear Guru
 
DanDan's Avatar
Opinions

1 I have often used my old Celestions is small rooms. A 12 inch driver with a 12 inch ABR. 24 inches of cone. IMHO bigger speakers dominate a room, controlling it more than smaller ones.
2 Bass developing and modal support or lack of it are different things. See 1.
3 Fibre or Foam treatment, if thick enough, does not necessarily sound dull. In fact the opposite frequently happens.
4 Correct, you can't make such comparisons.
5 You can place rear ported speakers where you like. If the rear port becomes loaded slightly differently due to proximity to a wall or corner, this may be a good thing, or not. You can even plug the rear port to diminish LF.
DD
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