Boring Neutral Speakers

How does having woofers facing in more than one direction help to reduce room interaction? I would have thought that having multiple bass sources would introduce even more cancellations and peaks.

 

Hi,

Yes, usually a meter or two behind the directors stand and around 4m up.

The Mikes on a Decca tree are three large diaphragm omnidirectional (that is they pick up sound equally from all directions) mikes which with rising frequency become acually rather more directional and roll of the treble slowly and gently quite early.

Ciao T

 

Such as the Neumann M150

 

Hi,

It's complex. If the distance between the various woofers is large enough they may excite different room modes differently.

Let us take an example. We place two subwoofers, one in the left front corner and one in the right front corner, driven MONO!.

We have just killed one main room mode and odd multiles, namely tose where the pressure in the two corners would be opposite. We can now add two more subs (which can be quite small as we have so many) in the other two room corners and voila, some more room modes killed.

The next step is of course to add for more subs in ceiling corners, now the only room modes that can be excited are those that require the two opposite walls to be at the same polarity of pressure. We can no start seeking a listening position that places the listener just halveway between the nearest wall and a point where the remaining room modes of concern have co-inciding null points.

We will now have generated a very even, room-mode unaffected LF reproduction without requiring EQ, heavy duty room treatment or any such trickery, in theory anyway, reality usually throws some spanners into the works.

Still, I would suspect that swapping one single monster sub for cormer 8 sub cubes using an 8" Sub driver (ApexJr Super Sub?) with one suitable big amp will give a major improvement in bass quality, if only it was not such an absolute drag to implement in a normal house....

Ciao T

 

I was gonna say ... and there was you suggesting that room treatment was obtrusive, whilst in the next breath suggesting surround sound bass

 

Hi,

Yup. My point is perhaps best descrined as:

There are several possible and achievable solutions to achieve a given goal. Which one is preferable depends usually on the context.

If you can dedicate a complete room to nothing but audio, no wives, pets, rugrats etc allowed and accept looks as completely secondary to a given sonic result, then you can add as much acoustic treatment as you like, 8 pcs of 24" Subwoofers, one in each corner, you name it.

My problem is that to me such a room and the system in it would be in essence a pure obsession with minimal use. I prefer my system to be in the room that I am usually in, which means I need a good bedroom system and an excellent living room system that can still be heard loud and clean in the Kitchen.

I observe similar thing with other friends who have serious rooms and system dedicated, they end up listening most to the secondary (or tertiary - if they have two "main" systems in the dedicated room) system in the living room.

Don't get me wrong, the dedicated systems in the dedicated rooms are usually utterly stunning sounding and notably better than what I have at home, but the secondary systems tend to be often much worse... ;-)

Ciao T

 

Thorsten,

The problem with your idea seems to be crossover frequency. In order for the subwoofers to be sonically invisible and to not damage the imaging, assuming the use of digital media, you are goingto have to cross over to the main speakers below 80hz and eventhen you have made no attempt at time alignment (essential for transient response IME). If crossing over this low down, your satellites will still be exciting the 2nd harmonic of the main room node along with the vertical axial node.

Without care the results will be disappointing in a number of ways. The implementation of digital delays is the only way currently to get around the issues highlighted above.

 

Hi,

Snap back to reality.

First, virtually all CD's are still mixed "mono compatible", meaning the stereo separation at low frequencies is really low. So, the bass is in essence STILL mono. So, you can make the bass still stereo, while keeping most of the advantages pointed out.

As for time alignment, a whole cycle of an 80Hz wave is > 4m Long. Depending on the room size this can indeed be an issue, HOWEVER, you can expand my idea by placing subs in suitable nodes. Finally, using a Behringer DCX2496 and 6 channels of amplification would alolow you to drive your subwoofer array time coherent, although this then again monkeys around with the room mode cancellation.

At any extent, there are many ways to audio. For anyone wishing to know what a really serious home HiFi system looks like, I recommend Dick Burwen's (he was/is Mark Levinsons mentor and responsible for quite a few of the ideas Mark has in his mind) very modest audio system.

Try to check that for time alignment at LF... ;-)

Without care ANY implementations results can be deeply dissapointing...

BUT (and here it comes), once you have added the delay, the room modes you had suppressed are BACK!

Hence (again) my point about directional speakers, they simply do not have the problems which we are here agonising to solve in ever which way.

Ciao T

 

They do, but they are reduced.

Directional speakers would be better again with room treatment.

 

Thorsten,

you will notice my comment contained the phrase IME , not IMO, therefore I am qualified to point out that not time aligning the signal below 100hz will have a noticeable impact on the perceived sound quality. This was discussed on the forum some years ago before you were here, but a search might be useful.

You also failed to address the issues of the second harmonic and vertical axial mode. Any reasons for that?

Your directional loudspeakers are not directional at the frequencies we are discussing.

 

Hi,

I have a good deal of experience on that too, including very large PA Systems with delay towers etc. I am not arguing against "time alignment" per se, I am merely pointing out something about the nature of multiple dispersed bass radiators to Simon and a good way of illustration is to go the extremes.

Would I fit a seperate subwoofer into every corner (time-delay or not), nope.

There are very good for me actually covering the, as indeed I did. Note that I pointed out that the "equal pressure (AT THE SAME TIME) at opposite walls/corners" will eliminate ALL odd order room eigentones (that is 1st, 3rd, 5th etc, usually after the 5th we tend to be near or above the modal range for normal rooms) and the EVEN room modes should be addressed by shifting the listening position with respect to boundaries and the pressure nulls so that for all relevant modes the listener is a the unity pressure point.

I did address the vertical mode in the suggestion to add the subs in the ceiling corners of the room, that is to kill the vertical odd modes.

BTW, as I am unaware of anyone ever having introduced and implemented such a system (for perfectly sensible reasons as I pointed out) no conclusions can yet be drawn if it would be preferable to have an LF system such as described, without time alignment and without room mode influences, or if a time aligned LF system with full room mode impact would preferable, or if the answer lies somewhere inbetween, according to taste.

My main point was to illustrate that adding more seperate subwoofers to a system must not inherently, as Simon suspected in his post, lead to a worse room mode problem.

Ou contraire mon ami, MY OWN directional loudspeakers are most definitly directional at the frequencies we are discussing, as are th MEG RL901K's I have been occasionally championing as "pretty good loudspeakers".

Your posts suggest that you neither take the time to actually read my posts carefully (or you would noticed the indirect references to even order room modes and vertical modes), nor do you make sure you actually follow the reference I give, to understand WHAT I am discussing.

This limits my part in the discussion to simply refuting your wrong statements and does not actually add anything to anything.

Ciao T

PS, just to spite people like you, a commercial product in the initial design phase right now is a fairly compact, reasonably high output subwoofer which will be unidirectional down to around 35Hz and will become progressively more omnidirectional below, in order to provide the last LF octave my current main speakers (also in essence commercial and as I pointed out directional with a DI of 4.8db or more across the ENTIRE frequency range they cover) do not, due to a concious design limitation.

 

Are you talking about your Tannoys (directional at low frequencies???) or your commercial product, the dipole? I was referring to the former, the latter I heard last week and found the bass to be eccentric.

Again, in a typically small UK living room, I would calculate that your solution will either cause time smear of mid bass transients or, as you say will result in the room nodes not being suppressed.

Are you familiar at all with the work of the Harman Group and the Bass Enhance program?

 

Hi,

The tannoys, corner loaded are actually also "directional" at LF, though the "waveguide" is formed by the rooms walls.

But the tannoys are long gone, I am listening to my commercial products at home (I know, disgusting, innit), if a rather tweaked up variant desitned to become the "SE" version.

!!!

"Eccentric bass"

Never heard that one.

The Acrylic Dipoles are an excercise in "making do", They have many compromises. I do feel that what they do, they do well. The rest is down to setup and what you are used to. Once I got sufficiently exposed to "dipole bass" with friends I found even well equalised "classic" speakers wanting, plus my then girlfriend thought the Corner Yorks a little overbearing but absloutely adores the Dipoles (and I adore her)... ;-)

BTB, no doubt you are aware that any commercial relaeses are always years behind what "Le Artiste" is cooking up at a given tyme. The dipoles really represent a late 90's stand for the "state of the art" as I understand it and are an intermediate step, trying to "get as much of what I want from what I can get".

Ciao T

 

Thorsten,

I heard these at a heathrow show a few years ago and enjoyed some things that they did very much.

I particularly liked the out-of-cabinet experience of them.

Despite being a horn lover, I found the horn tweeter to be a bit harsh and overbearing - although the room may have been a factor in that of course.

Have you made any adjustments, and did you think the treble a little overbearing in the show?

cheers
chris

 

Hi,

I don't think that was the tweeter, personally. There is a little "brightness" remaining with the Bicone Drivers, especially the Version you heard (those where off the shelf Supravox, the production ones have had their parameters adjusted to bring a little better balance in among some other things).

But equally, without the whizzer cone the speaker would cut off at 10KHz, meaning a Supertweeter becomes mandatory (this is the case for my current setup which uses a single cone fieldcoil driver). There the Supertweeters are very nice and not at all "bright". Drop in for a listen when you are in London....

Ciao T

 

3dsonic/Stereo Mic

**edited**

would you mind taking your inane oneupmanship bs elsewhere.

i tell you what would be a change from all this willy waving - what sort of music do you like - that'd assuming you actaully lisyen to any.

btw this particularly vacant thread was started as a puff for a hifi kit web site

 

If you don't understand the subject matter then kindly run along and post in the music section would you old chap.

Seems you got confused. Zerogain is a hifi forum you know. As for me being boring, well, you haven'tmade me laugh lately.

 

mic

my points is that your little obsessions are helping make this once vibrant forum tedious and elitist.

 

John,

Surely it is more interesting to have a discussion about room acoustics and hopefully expand people's knowledge than to read people making recommendations for budget cables having never heard the system into which it's going?

Are you suggesting that because I enjoy conversations on audio theory I should find an alternative forum? DO you see me compalaining when some headless chicken asks about squeezeboxes for the millionth time?

take a chill pill.

 

I think John's point is that you aren't having a discussion,you are trying to either out do each other or just show off,one or the other.