[rollei_list] Re: Completely OT- Loudspeaker info
- From: Akhil Lal <alal@xxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Wed, 16 Feb 2005 12:07:00 -0500 (EST)
Perhaps I did not state it clearly.Than's what happens when you post in
the early AM hours. What I meant to say is that the the
ear's thershold is higher than the group delays produced by typical
crossovers, i.e. group delay is not audible. TTBOMK, the only serious
study on this was by Blauert & Laws, published in the JASA. On music,as
opposed to pure tones, masking comes into play and makes it even harder to
detect.
There is increased interest in dipole speakers using moving coil
drivers. Several DIY dipole speaker designs can be found on the web. They
appear to be based on Linkwitz' earlier work, Frank, can you tell us a bit
more about your speakers? I know Watkinson in the UK was working on a
dipole design, is he the one who made yours?
Regards,
Akhil
On Wed, 16 Feb 2005, Frank Dernie wrote:
> It is interesting to study the audibility of phase distortion. I have
> listened to a square wave through a loudspeaker and can barely tell
> the difference caused by a level of phase distortion which makes the
> wave visibly unrecognisable as a square wave on an oscilloscope. One's
> eyes are much more phase sensitive than ones ears! In order to do this
> one must find a phase coherent loudspeaker and listen in the nearfield,
> before the room interactions have had their effect. Very few speakers
> on the market are phase coherent.
> If phase accuracy was extremely important multi miked recordings mixed
> using a conventional desk would sound even worse than they do!
> An electrostatic is fairly phase coherent in the first 3 to 4 feet in
> front of the speaker. By the time the back reflection is heard (and the
> extra stereo "depth" thus created enjoyed) there is no phase coherence
> whatever.
> A friend of mine designs dipole speakers which sound great. I have some
> of his prototype units at home just now. The biggest benefit is the
> cost savings associated with the box. Producing an effective closed box
> speaker where a considerable proportion of the sound being heard is not
> cabinet vibrations is spectacularly expensive, and rarely achieved.
> Creating an effective baffle to effectively separate front and rear
> waves needs a good understanding of the physics but then can be done
> relatively inexpensively. They have to be positioned very precisely
> within the room to achieve bass evenness and extension.
> The Celestion 6000 system was AFAIK the first to exploit this acoustic
> characteristic, the bass module was positioned and orientated
> correctly then the main speaker put on top. The position of the bass
> units was calculated for each customer by Celestion using the listening
> room plan. They are spectacularly effective when thus positioned, but
> probably had a tiny market because, as you so rightly write, most
> people have to put their speakers where they go!
> Frank
>
>
> On 16 Feb, 2005, at 06:23, A. Lal wrote:
>
> > The ear's sensitivty to group delay (or waveform integrity as you put
> > it) is well beyond what most xovers produce.
>
>
>
Other related posts:
