Speaker design discussion

You are deliberately playing games Rob, I thought better of you. I repeat for the third time. RA's design work with room boundaries and cabinet design were done while he was at Acoustic research, but Acoustic Research didn't use them as they wished to stick with what had become conventional, especially as they thought they had a patent on it which didn't hold up in court, which was acoustic suspension. *HE LEFT* AR and formed his own company to pursue his designs. So you can stare at you AR18 for as long as you like and they wont tell you anything about Roy Allison designs.

 

Staring at an NVA Cube wont tell me much about RA designs either.
Listening to them, even less.

You can recount papers and other people research 'till the cows come home but there is little point until you actually understand them yourself.

The basics of room interaction are perfectly well understood by most designers.
However, if you cannot grasp what is wrong with an undamped, completely empty cube in which you have an unfiltered bass/mid driver, that is something of a problem. Go do some reading.

BBC Research Department archives are a good place to start.

 

The last place I would go to understand loudspeaker design is the BBC website, it is tangential, a backwater that most speaker designers now just pay lip service to. We used to have sensible simple designs like Tannoy and Goodmans and along came someone with a white coat who had a brief to make the BBC voice reproduced. Fine but what has that got to do with music. The americans never fell into the over complicated trap and went on refining and producing good simple well built loudspeakers. If you ever manage to find a pair of Allison 6s then you will know what I am talking about, and the Allison 1s will shock you how good they are. I do the same as RA I use a two way so I use a top bass driver and a cube cabinet, if I produced a three way I would put that driver as close to the floor as possible. The designs are not copies they are sitting on the shoulders of a giant, which we all do as there is nothing unique in the world of audio, just refinement. I am adding my own refinement and part of that addition is removing the remnants of the internal wadding and filtering he minimised, because I now have a cabinet that can cope with it, nothing more. AND as I have said from the very beginning of this thread, if you haven't a problem then why try to cure it.

 

Jesus Richard you truly are clueless, planar or cone driver it makes no difference if the centre of the driver is coincident with the lines of symmetry of the front face it will propagate standing waves, if it is coincident with both the the vertical and horizontal axis of the front face then it's even worse. There is almost no worse shape than a cube, apart from a spheroid the sidewalls of which are all equidistant with the acoustic centre of the driver.

As for there being nothing inside your speakers but music, that's a nice idea, but sadly all there is inside your speakers is back waves, time smearing and more vibration than could possibly be good for them.

 

And the wadding doesn't remove it it just filters it into a waffle which more of a problem than just leaving it as music. Anyway please yourself what you think and you are welcome to produce a design yourself and put your money where you supposed expertise is, that is what I have done and it is out there for people to buy or not or to praise or not. And I will explain its design principles to any one who asks.

And thank you for the personal insults yet again and from someone who doesn't put their ideas out there. You obviously don't understand, but I am sure others do. A cube when used with a cone driver, which as you should know, propagates HF from the centre of the cone which is furthest into the speaker so the wave is not from the top plate of the cabinet but in this case about 1/3rd inside the cabinet so it is unequal length, spreading more and more to the LF as you get nearer to the surround, and deep LF drives the chassis rim as a piston (acoustic suspension) which drives the enclosure. A planar speaker would be at the top plate and all frequencies would be transmitted at that plane so you would have what you describe. I think this has become another bit of hi-fi bullshit folklaw that is propagated by ignorant people, so no one has tried it. The fact remains that used with a cone driver a cube cabinet is the only one you can guarantee not to have equal length standing wave, as I have explained now at least four times, but if you wish to continue in ignorance then continue, Roy Allison did it and I do it, so that is two who have debunked this folklaw.

 

Of course it doesn't.
It attenuates unwanted sound that isn't particularly nice to listen to.
Stick your head into a plain unstuffed box while the driver is operating and listen.

The box is an unfortunate necessity with all but open baffle or horn loaded loudspeakers and as such any contribution from it should be minimised.
Undamped cubes without any internal absorption run completely counter to this.

What you end up with are shouty, aggressive, fatiguing loudspeakers.
Cubes are very much a Richard design, not a Roy design.

 

Richard, your lack of a basic grasp of geometry is simply appalling. It makes no difference where on the cone the sound is generated or the direction of propagation from the back of the cone. Assuming that the sound launches from concentric rings from the back surface it is constrained within two axis of symmetry whichever way it goes.

Regardless of whether this is LF from near the surround, or HF from the centre of the driver, the symmetry of the cabinet they see is identical.

I'm well aware of what goes on within acoustic spaces Richard I was the product specialist responsible for the implementation of the acoustic simulation solution used to help Foster and Partners fine tune the design of the assembly room space in the GLA building. So stop embarrassing yourself. I've modelled literally thousands of different spaces for acoustic analysis including many simple and some hugely complex sound sources. I think I understand how cubes works..

 

Well then it is a wonder you don't understand something as simple as this. I shall try to put it in simple easy terms for you. "A cube" six sides of equal dimensions. A circular hole of 8" dia is cut in one side. A cone 4" deep is inserted in that hole. If measurements are taken from that cone to the side walls and base are they the same measurements as from the cube sides to each other. Well obviously not, so it is no longer a cube when referenced to the cone. If you still don't understand I will build a little coloured model out of cardboard for you to play with.

 

I have done the equivalent and put a microphone inside with wadding and without and listened on headphones. The result of that made me remove the wadding. I did it in 1992 with the original Cubes that were made from HDF.

Well what you say should result from it you should go and tell the Cube owners, who have integrated them into their acoustic, and stand back for the laughter.

 

Done that - at the computer bake-off at your place.
It was 'nice amps shame about the speakers' - universal view as well you know as you were there.

Don't let your Cube owners near a pair of 1970s Dynaco A25s.
There won't be much laughter.

 

I have found a pic of the Allison 6 and at the same time found pics of cube speakers by Monitor Audio - B&O - Yamaha and others who must be equally stupid and lacking knowledge as I am Top one is the Allison 6











There were a lot more but I cannot be bothered to link to them.

 

I don't know that at all, you are making it up. One person didn't like the omni projection, you didn't express a view, and one trade member who shouldn't have been invited used the speakers as an excuse for his stuff not coming top, the rest were complimentary.

Come on Rob you are being a silly boy just because I have upset your friend Tony L, really now this is not good behaviour for a admin / moderator, or are you hoping I will lose my temper so you have an excuse to boot. Sorry no chance, you will have to do that for no reason if it is important to you.

I even asked you to phone me so we could kiss and make up but you haven't

 

You don't seriously expect me to link several thousand examples of non cube shaped speakers to blow your theory into the weeds.... do you?
Perhaps you do.

 

Don't be silly, anyway this is mainly aimed at the comments by SQ, but I suppose double teaming means you are involved as well

My point - which should be obvious - the attempt is to isolate me and cube speaker designs as something from my strange mind or from my ignorance, well I am just showing that I am in some good company.

 

Very limited company indeed.

A couple of Allison budget designs - better ones used larger non cube cabinets - and a couple of lifestyle products.

I wouldn't go shouting about it!

 

The bigger Allisons use extended cubes or triangles as they have equal body side depth as well.

As for the others well they cannot be serious products if you don't approve of them.

 

Richard, an extended cube is by definition, not a cube.

 

Brilliant then a cube with a cone inserted in it is not a cube by definition either

 

I really wish I'd heard the cube speakers last Sunday, and the AR18s for that matter.

 

You are welcome to come and hear them jonesi.