Here is another company in Australia that you can find decorative acoustic panels. The guys there are very nice to work with.
http://www.acousticartpanels.com.au
Sorry I don't mean to interrupt this wonderful thread, but since room treatment is parbably part of the OB system and because somebody has asked so I thought I should list all the companies I found that sells Acoustic Panels in Australia.
http://www.acousticartpanels.com.au
Sorry I don't mean to interrupt this wonderful thread, but since room treatment is parbably part of the OB system and because somebody has asked so I thought I should list all the companies I found that sells Acoustic Panels in Australia.
One of the big drawbacks of Isobarik or mounting OB drivers adjacent to a wall is a strong short-delay reflection. The timing of the first reflection is quite critical, whether it arrives from a rear Isobarik driver (cones are acoustically transparent), a reflection from a nearby wall, or in more attenuated form, reflections from a cabinet or baffle edge.
A little story ... in my first (horrible) job, I worked retail in a stereo store, and we sold B*** 901's along with Advents, JBL100's and 200's, Cerwin-Vega, Infinity, Acoustic Research, and some pretty terrible Japanese and house-brand speakers. The B*** rep installed the 901's by hanging them from chains coming from the ceiling, which made sure the sales staff couldn't screw up the critical speaker-to-wall distance. Whether you like ol' Amar or not, he was no dummy, and he made sure the 901's sounded the way he wanted.
This distance was something like 20~24 inches from the back of the 901's to the wall. Just out of mad curiousity, we also tried a rumored "underground" technique for auditioning the Advents (the best speakers we had), by pointing them right at each other, and using that same critical driver-to-wall distance. As you might expect, it had the same huge sound as the 901's, just not as overblown and way out of scale. By the way, the soundstage was gigantic on the facing-each-other Advents and the 901's, and it didn't matter if the source was rock, classical, or funky-sounding Los Angeles Top 40 FM radio.
It was the driver-to-wall distance that was absolutely critical. Any closer, and the sound became a jumbled mess, resonant, shrill, and no depth at all. Further out was OK-sounding, just a bit more of the same. The critical parameters was the ratio of direct to reflected sound (just as ol' Amar said) and the delay time, which had a minimum value probably around 3 mSec.
Where you might differ with Amar was the ratio of direct to reflected, which as far as I could see was pretty much a made-up number of 11% direct to 89% reflected, and the cheapo implementation with EQ'ed drivers and an overstressed 200-watt amplifier (they were real power hogs). In other words, the plain old stacked Advents facing each other sounded better. In terms of image champs, though, the Ohm Walsh speakers were hands down the best, but were even more power hungry than the 901's, and had fairly squashed dynamics even with a huge amplifiers. (This was the day of the Crown DC300 and the Phase Linear 400 as standard demo amplifiers.)
I'm not saying any of this sounded good. It was pretty terrible compared to the quite mundane AR-6's I had at home, but the whole business of critical distance left an impression: Reflections shorter than 3 mSec are not your friend, whether they come from an internal cabinet reflection, multiple closely-spaced drivers in a cabinet sharing a common volume, diffraction at the edge of the cabinet, Isobarik driver mounting, or putting the drivers right next to the wall. The result is jumbled, phasey, very fatiguing sound, with lots of coloration in the vocal range.
Get past the critical distance, though, and everything changes. The ambient impression detaches from the speaker, and if the things are arranged right, fills the room with a 120-degree wide arc of spatial impression, with crisply localized instruments in the sonic space. Where the pseudo-omni's fail is having drivers on all sides of the cabinet, so the sound from the rear drivers diffracts around the cabinet edge and arrives much quicker than the reflection off the wall, thus blurring the direct-arrival sound.
This is why I agree with the previous discussion that the backwave needs to be managed in several ways: a soft transition at the baffle edge, felt damping around the rear of the drivers (but spaced away several inches so it doesn't mass-couple to the driver cone), and adjusting the crossover and response of the rear tweeter so the rear wave has a reasonably smooth frequency response.
A little story ... in my first (horrible) job, I worked retail in a stereo store, and we sold B*** 901's along with Advents, JBL100's and 200's, Cerwin-Vega, Infinity, Acoustic Research, and some pretty terrible Japanese and house-brand speakers. The B*** rep installed the 901's by hanging them from chains coming from the ceiling, which made sure the sales staff couldn't screw up the critical speaker-to-wall distance. Whether you like ol' Amar or not, he was no dummy, and he made sure the 901's sounded the way he wanted.
This distance was something like 20~24 inches from the back of the 901's to the wall. Just out of mad curiousity, we also tried a rumored "underground" technique for auditioning the Advents (the best speakers we had), by pointing them right at each other, and using that same critical driver-to-wall distance. As you might expect, it had the same huge sound as the 901's, just not as overblown and way out of scale. By the way, the soundstage was gigantic on the facing-each-other Advents and the 901's, and it didn't matter if the source was rock, classical, or funky-sounding Los Angeles Top 40 FM radio.
It was the driver-to-wall distance that was absolutely critical. Any closer, and the sound became a jumbled mess, resonant, shrill, and no depth at all. Further out was OK-sounding, just a bit more of the same. The critical parameters was the ratio of direct to reflected sound (just as ol' Amar said) and the delay time, which had a minimum value probably around 3 mSec.
Where you might differ with Amar was the ratio of direct to reflected, which as far as I could see was pretty much a made-up number of 11% direct to 89% reflected, and the cheapo implementation with EQ'ed drivers and an overstressed 200-watt amplifier (they were real power hogs). In other words, the plain old stacked Advents facing each other sounded better. In terms of image champs, though, the Ohm Walsh speakers were hands down the best, but were even more power hungry than the 901's, and had fairly squashed dynamics even with a huge amplifiers. (This was the day of the Crown DC300 and the Phase Linear 400 as standard demo amplifiers.)
I'm not saying any of this sounded good. It was pretty terrible compared to the quite mundane AR-6's I had at home, but the whole business of critical distance left an impression: Reflections shorter than 3 mSec are not your friend, whether they come from an internal cabinet reflection, multiple closely-spaced drivers in a cabinet sharing a common volume, diffraction at the edge of the cabinet, Isobarik driver mounting, or putting the drivers right next to the wall. The result is jumbled, phasey, very fatiguing sound, with lots of coloration in the vocal range.
Get past the critical distance, though, and everything changes. The ambient impression detaches from the speaker, and if the things are arranged right, fills the room with a 120-degree wide arc of spatial impression, with crisply localized instruments in the sonic space. Where the pseudo-omni's fail is having drivers on all sides of the cabinet, so the sound from the rear drivers diffracts around the cabinet edge and arrives much quicker than the reflection off the wall, thus blurring the direct-arrival sound.
This is why I agree with the previous discussion that the backwave needs to be managed in several ways: a soft transition at the baffle edge, felt damping around the rear of the drivers (but spaced away several inches so it doesn't mass-couple to the driver cone), and adjusting the crossover and response of the rear tweeter so the rear wave has a reasonably smooth frequency response.
Zene Gillette said:
No, Velvet Elvis sound absorbers are NOT a good idea for at least two reasons:
- Velvet Elvis painting are hard to come by these days. About 10 years ago the Graceland Gang cracked down on these "unauthorized images." So you can't sell without approval. (But look toward Mexico hint, hint.)
- If you had them made or painted them yourself, you would almost certainly be using acrylic paint. The acrylic paint is going to clog the pores of the velvet and create nasty reflections - especially in the mids and highs.
Result? Multiple phantom Elvis images cluttering your listening space. Not pretty. Leave the phantom Elvises at Krispy Kreme where they belong.
Live End Dead End
IIRC there was a very good series of articles in Audio magazine (USA) in the late 70's early 80's about the design of Live End Dead End rooms to optimize the performance of speakers in the room. they spend a lot of time discussing the Haas effect. Their contention was that for best imaging the first initial reflections should occur 8-9 ms after the initial signal reached the listening position. This corresponds to the speakers being > 1.3 meters from the closest wall.
Listening to electrostatics dipoles I have found this to be true. If you can diffuse the reflected sound the effect is much better.
IIRC there was a very good series of articles in Audio magazine (USA) in the late 70's early 80's about the design of Live End Dead End rooms to optimize the performance of speakers in the room. they spend a lot of time discussing the Haas effect. Their contention was that for best imaging the first initial reflections should occur 8-9 ms after the initial signal reached the listening position. This corresponds to the speakers being > 1.3 meters from the closest wall.
Listening to electrostatics dipoles I have found this to be true. If you can diffuse the reflected sound the effect is much better.
Hi Kevinh
That work was (live end, dead end or LEDE recording studio’s) pioneered by Chips Davis, a Synaudcon alumni but not related to Don Davis, the founder of Synaudcon.
The premise is to absorb all the close (to the source) reflections, these harm the stereo image in the recording and to scatter the rear wall reflected energy.
That part was orchestrated by another Synaudcon fellow, Peter D’antonio who came up with funny wood diffuser panels for that use.
This (not having close reflections) is one argument for using a waveguide.
Actually you nearly can’t avoid having a waveguide as when a driver is too small to have directivity, its radiation is then defined “guided” by what is around it.
Best,
Tom Danley
That work was (live end, dead end or LEDE recording studio’s) pioneered by Chips Davis, a Synaudcon alumni but not related to Don Davis, the founder of Synaudcon.
The premise is to absorb all the close (to the source) reflections, these harm the stereo image in the recording and to scatter the rear wall reflected energy.
That part was orchestrated by another Synaudcon fellow, Peter D’antonio who came up with funny wood diffuser panels for that use.
This (not having close reflections) is one argument for using a waveguide.
Actually you nearly can’t avoid having a waveguide as when a driver is too small to have directivity, its radiation is then defined “guided” by what is around it.
Best,
Tom Danley
RPG acoustics
Thanks for the reminder, I remember that Peter D'Antonio was involved this early on. For those interested here is his company: http://www.rpginc.com/index.htm
Wave guides can be a good solution for many situations, WIth open baffle like the subject of this thread or an electrostatic diffusion behind the speaker and the listener can sound very pleasing, as long as the room decay is handled correctly. A built in bookcase/ record shelf with the books/records distributed unevenly can provide a good approximation of the diffuser panels.
The abffusors in the corners to damp low frequency modes can help also.
Room treatments applied properly can really add a lot to the enjoyment of dipole/OB speakers.
Thanks for the reminder, I remember that Peter D'Antonio was involved this early on. For those interested here is his company: http://www.rpginc.com/index.htm
Wave guides can be a good solution for many situations, WIth open baffle like the subject of this thread or an electrostatic diffusion behind the speaker and the listener can sound very pleasing, as long as the room decay is handled correctly. A built in bookcase/ record shelf with the books/records distributed unevenly can provide a good approximation of the diffuser panels.
The abffusors in the corners to damp low frequency modes can help also.
Room treatments applied properly can really add a lot to the enjoyment of dipole/OB speakers.
Hi
Yeah, I would even take it farther and say that while it helps with dipoles etc, it makes even more difference with speaker having less directivity like little domes and cones.
I had a 3 way cone/dome/dome system that had outstanding imaging outside while they were poor in the long skinny room I had to deal with.
A HUGE and spouse approved fix was to hang a pair of her weavings on the walls where the specular* reflections would be. That * is the location where if a mirror were placed flat on the wall, that you would see the tweeter from your listening position.
Later, I snuck an extra wool blanket behind each.
Just killing those wall reflections alone made a giant difference in imaging.
In that way, I think stereo imaging (preserving it when its in the recording) is something like intelligibility. That is, when the reflected sound level rises above some level relative to the direct sound, the imaging like the ability to hear words, is harmed.
The LEDE work showed that the near reflections are the most problematic while an absence of reverberant field to the rear (anechoic) produces a “hole in the room” feeling, like the rear of the room is gone.
Later work showed that having the reverberant field spectrum approximately the same as the direct field was also preferred by listeners. The result here is that far off axis, the system has the same tonal balance as on axis (nice) if you’re not in the sweet spot.
Best,
Tom Danley
Danley Sound Labs
Yeah, I would even take it farther and say that while it helps with dipoles etc, it makes even more difference with speaker having less directivity like little domes and cones.
I had a 3 way cone/dome/dome system that had outstanding imaging outside while they were poor in the long skinny room I had to deal with.
A HUGE and spouse approved fix was to hang a pair of her weavings on the walls where the specular* reflections would be. That * is the location where if a mirror were placed flat on the wall, that you would see the tweeter from your listening position.
Later, I snuck an extra wool blanket behind each.
Just killing those wall reflections alone made a giant difference in imaging.
In that way, I think stereo imaging (preserving it when its in the recording) is something like intelligibility. That is, when the reflected sound level rises above some level relative to the direct sound, the imaging like the ability to hear words, is harmed.
The LEDE work showed that the near reflections are the most problematic while an absence of reverberant field to the rear (anechoic) produces a “hole in the room” feeling, like the rear of the room is gone.
Later work showed that having the reverberant field spectrum approximately the same as the direct field was also preferred by listeners. The result here is that far off axis, the system has the same tonal balance as on axis (nice) if you’re not in the sweet spot.
Best,
Tom Danley
Danley Sound Labs
Spot on Tom
The tip about the mirror to 'see' where the specular reflections can occur is a very good point. I wish the original article from Audio were available somewhere.
A room that causes problems can prevent the best amps and speakers from performing properly. I's always amused at how the boutique audiophiles look at the speaker room interactions and worry about 2nd and 3rd order distortions when 'room distortion swamps many other issues.
The tip about the mirror to 'see' where the specular reflections can occur is a very good point. I wish the original article from Audio were available somewhere.
A room that causes problems can prevent the best amps and speakers from performing properly. I's always amused at how the boutique audiophiles look at the speaker room interactions and worry about 2nd and 3rd order distortions when 'room distortion swamps many other issues.
Depends on the speaker configuration?
The combination o fthe Speaker and the room, will determine the decay time of the reverberant sound field. You want the reflected sound to be diffuse with the initial reflections arriving no sooner than 8-9ms after the initial wavefront and decay should occur before 60ms with a smooth decay in the reverberant field.
BTW with respect to the design being talked about in this thread, the delay in the initial reflections is important for the mid/high and high frequencies. The floor reflections from the LF drivers mounted by the floor won't cause imaging problems. If you look at the configuration of the RPG diffusers for example they are only about 4" deep so they are ineffective below ~ 500 HZ IIRC. Rugs can be important in damping early reflections off the floor from the Mid HF drivers. The path length difference between the direct sound and the floor reflection for a driver 1-1.5m off the floor is about .6-.8m. similar situation with reflections off the ceiling. Line sources and Wave guides have more linited vertical dispersion which can with the ceiling and floor reflections.
The Room treatments from companies like RPG do a great job but the WAF isn't very good
The combination o fthe Speaker and the room, will determine the decay time of the reverberant sound field. You want the reflected sound to be diffuse with the initial reflections arriving no sooner than 8-9ms after the initial wavefront and decay should occur before 60ms with a smooth decay in the reverberant field.
BTW with respect to the design being talked about in this thread, the delay in the initial reflections is important for the mid/high and high frequencies. The floor reflections from the LF drivers mounted by the floor won't cause imaging problems. If you look at the configuration of the RPG diffusers for example they are only about 4" deep so they are ineffective below ~ 500 HZ IIRC. Rugs can be important in damping early reflections off the floor from the Mid HF drivers. The path length difference between the direct sound and the floor reflection for a driver 1-1.5m off the floor is about .6-.8m. similar situation with reflections off the ceiling. Line sources and Wave guides have more linited vertical dispersion which can with the ceiling and floor reflections.
The Room treatments from companies like RPG do a great job but the WAF isn't very good
Hi, John,
My NaO sounded first class, as I previously reported in the forum, in the larger room in my previous house. I have moved to a new place now and have a smaller, dedicated sound room of 5.1m x 6.5m. The NaO does not sound as good as before.
Previously, I had a large, thick wool carpet hanging on the front wall behind the speakers. Now I have only two large glass windows behind the speakers. Obviously I will install timber blinds on the windows, then a large, heavy curtain. I am also planning on installing large acoustic panels on the first reflection points on both the ceiling and the side walls. I have not decided if I will hang the large carpet on the wall behind me.
My current set up is: speakers 1.6m from the front wall, 1.2m from the side wall. Listening position forms a triangle from the speakers.
I am interested in what you said:
Could you please provide a few summary points? But first, here does the rear wall refer to the "rear to the speakers" or "rear to the listeners"? I guess that rear wall is the wall behind the listeners, and front wall is the wall behind the speakers and in front of the listeners. I ask this because I think front wall treatment may be more important than rear wall treatment, though both are necessary.
Regards,
Bill
My NaO sounded first class, as I previously reported in the forum, in the larger room in my previous house. I have moved to a new place now and have a smaller, dedicated sound room of 5.1m x 6.5m. The NaO does not sound as good as before.
Previously, I had a large, thick wool carpet hanging on the front wall behind the speakers. Now I have only two large glass windows behind the speakers. Obviously I will install timber blinds on the windows, then a large, heavy curtain. I am also planning on installing large acoustic panels on the first reflection points on both the ceiling and the side walls. I have not decided if I will hang the large carpet on the wall behind me.
My current set up is: speakers 1.6m from the front wall, 1.2m from the side wall. Listening position forms a triangle from the speakers.
I am interested in what you said:
Could you please provide a few summary points? But first, here does the rear wall refer to the "rear to the speakers" or "rear to the listeners"? I guess that rear wall is the wall behind the listeners, and front wall is the wall behind the speakers and in front of the listeners. I ask this because I think front wall treatment may be more important than rear wall treatment, though both are necessary.
Regards,
Bill
Yea, I always say that backwards. I think of the rear wall as the wall behind the speakers, to the rear of the speakers. My bad.
I favor rooms with RT60 in the 300 msec range. That is not as dead as a live end, dead end room, but it is not particularly live. It's pretty well damped. For example, if you have a number of people in the room the individual conversations are pretty distinct. One other thing I don’t care for about live end, dead end rooms is that they tend to be void of secondary reflections. Overly dead rooms start to sound a lot like ear phones in many respects, except that the image isn’t in the middle of you head.
You can see a picture of my room with the Minis set up here http://www.musicanddesign.com/NaOMinidiscus.html As you can see the floor is carpeted, there are drapes on the walls behind the speaker (front wall). Not seen is the ceiling which is irregular and not praticularly high. The corners of the front wall (behind the drapes) are cut at 45 degrees, and there is a stuffed, upholstered, sectional couch for listening. To me this yields a pretty decent image with a 10' to 12' listening distance. The room is 15 1/2' (4.7M) by 20' (6.1M) so it's very close to yours. The panels are 9' (2.75M) apart, 3.25' (1M) from the side walls and 4 1/2' (1.37M) from the front wall. This seems to give me the imaging characteristic I like with just about any speaker in the room (dipole or monopole). There is good detail with a good sense of openness.
However, I have also heard the NaO in a much liver room. Not my cup of tea as the image was some what lost but the sound was very open. There were diffusers behind the speakers in that room and the positioning was such that early reflections were still delayed at least 10 msec. In some sense this gave a sound on larger works that was much like what you might hear at a concert hall if you were sitting in the first balcony: room filling sound, but no precise sense of left, right, center. Some people seem to prefer that type of sound. It sort of masks the space of the recording in favor of the ambiance of the play back room. I prefer to recover the ambience of the original venue as captured on the recording.
I’m still a little uncertain of what Kevin is referring to as in a room with RT60 = 60 msec you would have difficulty understanding someone if he was speaking with his back to you. an RT60 = 60 msec is really pretty dead.
I favor rooms with RT60 in the 300 msec range. That is not as dead as a live end, dead end room, but it is not particularly live. It's pretty well damped. For example, if you have a number of people in the room the individual conversations are pretty distinct. One other thing I don’t care for about live end, dead end rooms is that they tend to be void of secondary reflections. Overly dead rooms start to sound a lot like ear phones in many respects, except that the image isn’t in the middle of you head.
You can see a picture of my room with the Minis set up here http://www.musicanddesign.com/NaOMinidiscus.html As you can see the floor is carpeted, there are drapes on the walls behind the speaker (front wall)
. Not seen is the ceiling which is irregular and not praticularly high. The corners of the front wall (behind the drapes) are cut at 45 degrees, and there is a stuffed, upholstered, sectional couch for listening. To me this yields a pretty decent image with a 10' to 12' listening distance. The room is 15 1/2' (4.7M) by 20' (6.1M) so it's very close to yours. The panels are 9' (2.75M) apart, 3.25' (1M) from the side walls and 4 1/2' (1.37M) from the front wall. This seems to give me the imaging characteristic I like with just about any speaker in the room (dipole or monopole). There is good detail with a good sense of openness.However, I have also heard the NaO in a much liver room. Not my cup of tea as the image was some what lost but the sound was very open. There were diffusers behind the speakers in that room and the positioning was such that early reflections were still delayed at least 10 msec. In some sense this gave a sound on larger works that was much like what you might hear at a concert hall if you were sitting in the first balcony: room filling sound, but no precise sense of left, right, center. Some people seem to prefer that type of sound. It sort of masks the space of the recording in favor of the ambiance of the play back room. I prefer to recover the ambience of the original venue as captured on the recording.
I’m still a little uncertain of what Kevin is referring to as in a room with RT60 = 60 msec you would have difficulty understanding someone if he was speaking with his back to you. an RT60 = 60 msec is really pretty dead.