The Advantages of Floor Coupled Up-Firing Speakers

[graaf]

The bass of the little HX135 rather sounded like 15" than like 5" and the tonal balance was really good (not measured, just subjective impression). Two drawbacks:
1) The bass is so directional that the floor position is only OK when you stand up

perhaps a variant of a whole construction tilted a bit towards the listener would do?

 

[el`Ol]

perhaps a variant of a whole construction tilted a bit towards the listener would do?

I think if one wants the directionality (low room interaction like a dipole and the physical impact of a horn) the direction is determined by the corner, everything else would just be a normal corner horn. Turning around this construction may give a nice BL-corner-horn flooder.
eck-horn

 

[graaf]

In the early 70s Ted Jordan wrote an article describing a system which used a line of 20+ fullrange units along the wall in front of the listener. The driver at each end faced the listener, the others all faced down and they were linked by delay components. I don't know that he pursued it because he moved onto his linear array systems.

The long line was meant to address stereo imaging rather than room acoustics. The same article describes a cut down version which used a central group of drivers and reflectors left and right. 20 years ago I thought that worked quite well but I haven't tried it recently with more revealing components.

here is the article, Ted Jordan for Wireless World, February 1971:
http://www.ejjordan.co.uk/PDFs/Jordan_WW_Feb_71.pdf

best to all
graaf

 

[graaf]

another Sonab-like thing:
Newsletter March 2006

We’ve now been evaluating the prototype Omni loudspeakers for about 3 months and have tried them in the living rooms of several family members. In one case attached to a modest Sharp stereo system, in another an ME 550, and also with a T-Amp. The feedback has been consistent. Spacious, good bass, easy to listen to, no “hot spot”, very versatile as far as placement in a room is concerned, no distortion at high levels. So, they are doing exactly what they were designed to do. These are loudspeakers which won’t visually dominate a room, and produce a sound with the omnidirectional characteristics of Sonab and Bose at an affordable price.

The prototypes of the premium version of these kits arrived from Stones Sound Studios just before this newsletter was due to go out so we have had a chance to compare them. The design is exactly the same so has the same spacious characteristics, but the difference is the drivers. The Vifa drivers are more than twice the cost of the PAE drivers in the standard version, and you can hear the difference. Clearer at all levels, brilliant transients, and wonderfully clear undistorted sound at high volumes.

If you are familiar with the way a piano fills a room with sound you should hear these speakers on a piano recording. A great demonstration of the value of sound that isn’t beamed at you.

These prototypes are available for auditioning. If you are close to Brisbane you are welcome to pick them up and try them out at no charge. People further away will have to be prepared to pay the transport costs each way.

The first batch of kits has been produced and so the Decibel Omni is now ready for sale. They are in the Loud Speaker Kits category on the website.

nice to see that someone at least is trying

 

[graaf]

Later lateral reflections are all good, very early ones are not. Floyd does not make this distinction and to that I do disagree. There are many other consultants that I have talked to who agree with me on this point.

well, this is quite fundamental disagreement, with immense impact on practical speaker design principles, isn't it?

 

[graaf]

What facts ? What problem is the Beveridge placement solving ?

the problem bothering many people also here - that in a typically sized room we cannot push the delay of first reflections beyond the required 10 ms

You imply that it is eliminating early reflections, but you seem to ignore the reflection off the wall behind the speaker.
(Which conveniently doesn't have an arrow in your diagram, as if it somehow doesn't exist)
Unless the speaker is flush mounted inside the wall there will still be both diffraction from the cabinet edge and reflection from the wall behind it. Something which has already been pointed out to you in this thread.

the diagram is Beveridge's not mine

have You considered what is the direction of this reflection in case of such configuration?

I think You haven't therefore You say:

This is no different than pushing a conventionally placed speaker right up against the front-wall of the room and somehow expecting the front wall to no longer exhibit reflections.

please try to draw lines respecting the angle of incidence=angle of reflection principle

Granted that the directivity of the speaker will reduce the wall reflection somewhat at higher frequencies, but for proper function a Beveridge speaker would have to have extremely wide dispersion, thus greatly reducing this mitigating effect.

not really - it can just be toed towards the listener - no problem
plus - the speaker can be made wide enough to further lessen this alleged problem

You then introduce the serious problem that the listener is now about 70 degrees off axis from the speaker. This by necessity is going to mean an extremely wide dispersion design is required, which means narrow baffle and small drivers,

why narrow baffle? Beveridge aimed at just 2Pi or 180°, I believe it is not necessary, and that it was just by product in Beveridge speakers

why 70° off axis?? in original Beveridge more like 30° for typical equilateral stereo triangle, perhaps 45°, but 70°??? where did You find it?

anyway - we can just toe them towards the listener - no problem

which is going to provide heavy illumination of both the front wall and contralateral walls. What for ?

there are several strategies as to front wall - one is illustrated below, as to contralateral wall - ask Dr Geddes as He advocates this approach

reducing direct to reflected ratio.

You think it is bad? why? Let's assume that we have first 10 ms of clear RFZ

What practical design of Beveridge speaker can you come up with that would have the same performance level as a large 3 way system but is flat enough to hardly or not at all protrude from the side wall ?

Its easy to overlook dynamic performance of speakers when thinking only in terms of polar patterns and directivity.

there are several strategies - You want to have dynamics? then line array is an option, an example of such strategy is illustrated below

So in summary, Beveridge placement attempts to solve early wall reflections, but unless it's actually mounted in the wall it doesn't in fact solve this problem. In the process we are now forced to listen 70 degrees off axis from the speakers, and get a far lower direct to reflected ratio. No thank you.

in summary - this is not correct and signals misunderstanding of the concept

for the reasons I have given above no in-wall flush mount is required neither one is forced to listen 70 degrees off axis
as to whether lower direct to reflected ratio is bad or good - in the light of what we are told by Dr Geddes clearly it is not the ratio that matters but timeline of reflections, of reverberation build-up - must not be too quick

in the setup I propose below You can see wide baffle speakers with line arrays that help to lower the level of floor and ceiling reflections
let's assume for the moment that these are monopoles not OBs and let's forget about the center L+R tweeter array - let's assume that the L and R arrays are fullrange
let's assume also that they are closer to side walls - touching them and that they are as much toed as proves necessary

then try to draw the lines to see where early reflections go in such a setup

use Your imagination! sorry I can't draw new scheme now, maybe tomorrow

 

[Bob Richards]

If you Google "Roger Russel" you'll find a great website put together by Roger, head of acoustic research and speaker design at McIntosh from 1968 - 92. He's recently developed a wideband columb speaker that he claims sounds incredible, and works with room acoustics more effectively than any other speaker design. It has 24 - 3.25 inch drivers per side, (vertical line array), tiny footprint, uses electronic EQ to be flat from 20HZ - 15kHZ. Bass is allegedly plentiful with no boominess, imaging is said to be second to none, no audible interference pattern due to multiple drivers, and they can be placed near walls so no divorce, very wide sweet spot, etc.. Check it out. The individual drivers appear to be available at Parts Connection and Madisound (who shows full specs) at $22 each (Peerless/Vifa TG9FD-10-04). They've gotten rave reviews at Hi-Fi trade shows. I'm pretty tempted to build a pair.

 

[graaf]

If you Google "Roger Russel" you'll find a great website put together by Roger

yeah, we know Roger, searching for "Russell" You can find 288 posts on Loudspeaker section of diyaudio
for example: http://www.diyaudio.com/forums/full-range/123161-line-array-coaxial-drivers.html

yes, the website is great, but mind You that Roger is not accepted as fully kosher here

kosher diyaudio array expert is Dr Jim Griffin of the Design Guidelines for Practical Near Field Line Arrays paper fame

 

[graaf]

Stereolith (with my modification, The cardboard (TM):

An externally hosted image should be here but it was not working when we last tested it.

Beveridge:

An externally hosted image should be here but it was not working when we last tested it.

Fundamentally the same !

Stereolith creates wider stage, and importantly, all the images are outside room boundaries, the walls really disappear.


- Elias

Place the Beveridge at the point of first ipsilateral reflection from a Stereolith. Of course it is not identical, but the pattern is the same, only that Stereolith creates wider stage than Beveridge.


- Elias

I don't think it is much wider or that it is inevitable

isn't the soundstage width a function of angle of the listening triangle? it is not that different on Your schemes, furthemore the angle of the listening triangle is a function of listener's distance to the stereo base so the stage can be widened by shortening the distance to the stereo base

of course we must assume that floor reflection is taken care of as it provides distance cue for speakers as physical sound sources thus additionally limiting the soundstage size (width and depth)
so if we want the Beveridge to make an unlimited soundstage as in case of stereolit we just need a flooder or a line source or at least an appropriate line array

and the walls disappear as well

 

[Charcoal]

As I understand Beveridge way need wide horiz. dispersion. That mens either omni (graaf way) or curved narrow line source, etc.

If one want to do the same placement with fullrangers line array, directivity is high.
But we can turn them slightly in the listenig area direction/ Will Beveridge principle work in such case, or we will get some issues?

 

[graaf]

But we can turn them slightly in the listenig area direction/ Will Beveridge principle work in such case, or we will get some issues?

yes we can

we can just toe them towards the listener - no problem

Beveridge aimed at ... 180°, I believe it is not necessary, and that it was just by product in Beveridge speakers

it suffices to draw the lines for reflections for anyone to see it clearly


and (at least in case of an array of small FRs) I can't see any potential source of any audible problems with toeing them a bit

regards,
graaf

 

[Bob Richards]

yeah, we know Roger, searching for "Russell" You can find 288 posts on Loudspeaker section of diyaudio
for example: http://www.diyaudio.com/forums/full-range/123161-line-array-coaxial-drivers.html

yes, the website is great, but mind You that Roger is not accepted as fully kosher here

kosher diyaudio array expert is Dr Jim Griffin of the Design Guidelines for Practical Near Field Line Arrays paper fame

Thanks for the info on Jim Griffin.

 

[graaf]

Thanks for the info on Jim Griffin.

You're welcome

 

[graaf]

this insightful post is also relevant here as various alleged Dr Toole's opinions were discussed also in this thread:

Toole's opinion on early reflections is not really that simple. I quote from a studio designer on a Dutch forum who asked Floyd himself:

"Hi Bert.

People who say I dismiss room reflections as unimportant - and there are a few, it seems - simply have not read or understood my book. It is patently obvious that room treatment is necessary, if only to establish conditions suitable for comfortable conversation. This requires reverberation times under 0.5 second. This alone, also pretty much ensures that film dialog will be clearly understood.

The most debated issue relates to first lateral reflections. Some of those arguing vociferously in favor of eliminating them seem to have a conflict of interest, being providers of acoustical materials. Others have more reasoned arguments. I say up front that there can be no universally satisfactory answer because there is no universal scheme for recording stereo or multichannel signals. Only through controlled listening tests can we get useful insights, and these are in short supply. In the meantime opinions reign supreme, and there are many of them.

In the book I show results of several double-blind evaluations, some done by me, some done by others, showing that listeners tend not to be disturbed by lateral reflections, and many even prefer them. I also point out that the professional side of the industry almost universally feels the need to eliminate them. I suggest, respectfully, that humans have a remarkable ability to learn, to adapt, and that recording engineers spending their days adding, adjusting, and removing - at will - delayed sounds from mixes undoubtedly are more highly sensitized to these sounds than are lay listeners. This probably applies to any audio professional, acoustical consultant or enthusiast who focuses enough attention on this task. We learn to hear things and, once heard, they tend not to go away. I well remember that during the resonance detection experiments, we all became extremely skilled at hearing and identifying resonances. During the tests, and for some time afterward, we were hearing little resonances in everyday life that normally would have been totally unnoticed. From such things paranoia is born, and if we had taken this to an extreme, we would have damped our wine glasses.

For stereo listening I have found that it very much depends on the program. Music with lots of decorrelated sounds, classical for example, is sometimes enhanced by reflections, although coincident-mic recordings may benefit from a lack of reflections - letting the direct sounds be more dominant (the Blumlien stereo effects work best in an almost anechoic situation). Pan-potted recordings (the majority of pop) end up delivering essentially monophonic sounds from left and right loudspeakers, and these may well benefit from a bit of spatial enhancement. Otherwise we are left with what really annoys me about stereo: a relatively spatial set of phantom images created by both loudspeakers, and two "anchor" images created by the left and right loudspeakers playing solo. In some recordings we hear a whole string section emerging from a single loudspeaker. Not realistic, and not even pleasant. In the past, I have recommended that serious stereo listeners hang absorbent drapes along each side wall, pulling them out and pushing them back to suit what they are listening to. Our listening room at the National Research Council in Canada had this feature.

In the book, I put more emphasis on multichannel audio, where much of the important sound is delivered by the center loudspeaker, farthest from the side walls. In these situations I conclude that treatment of the side wall reflections is an option. There may be situations in which their effects are audible, but when all 5 or 7 channels are operating, it is improbable that natural room reflections have much of an effect. Other things being equal, the effects of the room are most audible when only a single loudspeaker is operating, and it becomes less so as other loudspeakers (channels) contribute additional uncorrelated sounds.

Of course the degree to which reflections are activated depends on the directional properties of loudspeakers, and the extent to which the loudspeakers are well behaved in their far off-axis responses (side wall reflections can be 50 degrees and more off axis). It has become clear over the years that, with hard side walls, the more uniform the off axis frequency response, the higher the rating of the loudspeaker. So, one has to wonder whether at least some of the dissatisfaction with reflective side walls has to do the misbehaving loudspeakers. Sadly, most manufacturers don't provide us with sufficient data to judge. And that is another, and I would argue much more worthy topic, to argue about.

Best wishes,

Floyd"

 

[graaf]

interesting bare 12'' whizzer cone FR driver flooder experiments with measurements by Radugazon in the stereolith thread from page 67 - post #669 on:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-67.html

 

[graaf]

on the "gearslutz" proaudio-forum there is a very interesting discussion of Dr Toole's new concepts on loudspeaker-room as a system:
Understanding The Precedence Effect: ETC shift

 

[graaf]

nice room acoustics treatment!

 

[graaf]

looks like this different way of treating a room (an example above) is actually inspired by Stig Carlsson's ortoacoustic theories

 

[Radugazon]

Impressive "mise en scène", but I think that this room is too small for starting with these speakers whatever could be the claims and benefits of the room treatment.

I think also that the happy owner would consider a PC based server as a source.

 

[Pano]

The Swedish website is cool Gave me some great ideas for DIY diffusers.
All you need is a good assortment of 1/4 round.