If you have difficulty registering for an account on the forum please email In the question regarding the composer use just the surname, not including forenames Charles-Marie.

Main Menu

Show posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Show posts Menu

Topics - pwhodges


"Anyone who wanted a first-rate organ to replace something inferior should look at this instrument very seriously. Worryingly, the IBO page notes that it must be removed very soon."

Organs in danger / Too late...
October 29, 2010, 08:41:33 PM
This topic was being discussed in a couple of threads on the Hauptwerk forum until David was banned there.  At that point I had just made a long post as the result of some careful thought going back to first principles; I am copying that post here (essentially unedited) because I would be interested in David's reaction to it, and to give him the opportunity to continue the discussion a little.  In summary, for those who don't want to read it all, I believe that David's criticism of the use of many types of speaker in organ installations is justified, but that he gives the wrong reasons for it, and this both colours people's reactions to his criticism and fails to direct him towards a clear explanation of his solutions.

Quote from: pwhodges on the Hauptwerk forumFirst, a story. When I was a student, in the 1960s, some friends of mine who are now famous (as far as specialists in arcane areas of audio can be) for their work in (among other things) psychoacoustics, did some investigations into the realism attained using different stereo miking techniques. They played differently miked test recordings of the same performance to various people. The interesting result was that people who knew little about sound reproduction said that they thought one performance was better than the other - because they could hear a difference, and couldn't think of another way to express it.

I think that David is falling into the same trap, and as a result he ends up describing things wrongly even though he starts from the right point. This mismatch of perception is what has been annoying me, and I'd like to put it right.

I work (in my audio hobby, that is) generally in the areas of recording and reproduction - in 3D as it happens, using ambisonics. My aim in reproducing a recording is to play it back in such a way as to reconstruct the original sound field that the microphone has captured in such a way as to encompass the listener's head. This (though more exacting) is pretty much what most people playing back stereo recordings are aiming for as well. In particular, it leads to a requirement for minimal additional contribution from the listening room, and so, as well as making this rather dead, we design speakers so that the direct radiation in the direction of the listener has a flat response; other directions can go hang, so long as they do not have such prominent peaks or troughs that the (minimal) reverberation in the listening room becomes coloured. This leads to the typical design of a hi-fi speaker or near-field monitor (they are not fundamentally different) - and is not anything to do with being designed for pop music or anything like that, which is what David has been saying that irritated me so much!

PA systems have to deal with trying to get clarity across in places which inevitably have more reverberation than a typical domestic setting. They do this by going for directionality as far as possible, to minimise the excitation of the reverberation, and to gain the greatest signal to reverberation ratio at the listener's head that they can manage. The requirements are in fact similar to those above, but the space available allows the use of more extreme techniques, such as line sources, to increase directionality beyond what can be managed from a single box.

Now, if we consider the case of playing the sound of a pipe, recorded dry, in an auditorium, the requirements are quite different - we want to excite the acoustic, and we want to do it similarly to how a pipe would do it, that is, by radiating sound somewhat uniformly in all directions in order to get a similar build-up of reverberation. (The output of a pipe, or any other instrument, is decidedly not uniform in all directions - but attempting to model that non-uniformity is a lost cause with currently conceivable technology, even if a speaker per pipe was provided.) So we are looking, ideally, for speakers that radiate omnidirectionally, which is clearly a requirement deliberately not aimed for by hi-fi speakers, monitors, or PA systems - so David has good reason for saying that those are unsuitable, though the reason is not that which he gives (see story above). The response of a pseudo-omnidirectional speaker may also not be flat in any specific direction (as I suspect David has also observed), because what we would like to be flat is actually the power response integrated over all directions (parallel compromises can be seen in omnidirectional microphones designed for use in the diffuse field). Omnidirectional speakers are extremely difficult to make, because any sensibly sized speaker is large enough to act as a baffle at the higher frequencies (at 10kHz, an obstacle of only an inch or two's width is already significant); but there are techniques which enable one to get a bit closer to the ideal, and I have no doubt that David is using some of them.

I just think it would make life easier if he would (a) recognise what he is aiming for in engineering terms, so that he can use language that actually addresses the issues, and (b) tell us what he is doing, because once the issues are recognised, it will be seen that there is nothing magic about it - just solutions to a defined engineering problem.