ALFs OBs (BD-Design)

by PeterSt. , Netherlands, Sunday, August 20, 2006, 12:44 (6466 days ago) @ ALF

Hi Anthony,

Nice stories you have, containing life's wisdom. About the sprouting ... I know it !
Just yesterday I asked my 7 year old son -in order to prepare him for an audiophile happy future- that if he could hear high tones which shouldn't be there i.e. are aNoying, he should tell me instantly ... That's life ...

Again you seem to be earlier with the wines than we do, and yes, I prefer white wines with red meat. I think it's allowed for over 10 years now.

Like you, I once had a living room with speakers and a corner of the room in the middle. I couldn't psychologically stand it. I don't think it helped either. :wink:

About your findings about OB speakers and the placement in the room being just more important ... wouldn't that be logical ? I'd even say you will suffer from phase distortions earlier, having more direct reflections behind the speaker ...

But now hear this :

A few years ago I moved to a new house, and the listening room is actually too large not to have reflections and "hollow" sound at speaking etc.
For a long time I was in search for affordable solutions for bass traps and other damping material. This search took so long, that the solution came by itself. But I think you can't guess how ...
Well, I "just" improved the sound from the equipment.

That I know a few things about calibrating a room (I even bought the equipments needed) is not for nothing : it's because it was just needed, surely after I bought myself two subwoofers, which I use for listening to music. That's the standing waves all over the place story;
These standing waves are just easily measurable, so they were really there and could be visualized on the PC and on the scope. Sidenote : when you have two subwoofers, the problems from them - as well as the calibration is a 100 times more difficult, because they cancel eachother out - or add at standing waves places (which are typicle small areas in the room).

At the moment I was happy with the calibration (except for the (btw inaudible) delay and noise the parametric equalizer added, I bought the TwinDAC, as a replacement for my AudioNote DAC. Things were so much different because of that (mainly in the sub-low area), that I had to re-do the calibration, which I couldn't properly do anymore in the time I gave myself for that (a few weekends). And then ... it turned out that I could leave the equalizer out, with not any difficulty in the room anymore.

This is a very strange phenomenon, and above all unofficial. I have a few theories why this can happen though, and let's say that when the bass tones are not straight but more fuzzy, this adds GC times of more difficulty in the room. Think a bit of this : a straight, say, 24Hz tone, may create a standing wave of a surface of 10cm2 (I just guess the 10cm2, but I think someone with knowledge could calculate the "thickness" of a wave, once it creates a knot somewhere). However, when the straight 24Hz tone degrades into a wobbling 22-26 Hz tone, this is, say, 6 times the 10cm2, and is therefore much more easy to encounter (at e.g. the sweatspot).

There's much more "science" to this, like I could let you feel the straightness of bass sounds (normal music), by putting your hand on the subwoofer's driver, immediately letting you know how more straight the waves "feel" with less jitter opposed to more jitter. Jitter then, as one of the (btw very important) components of better sound (and which can be controlled by me, to a certain degree).

Sprouts (of various kinds) or not, when you attach a cheap second hand scope to your loudspeaker cables towards the bass driver(s), and feed all with a continuous sinus, you just can SEE what is better (for source equipment etc.), because you will SEE the wave. If you -as a next step- would attach the scope (at it's second input) to a microphone, catching that same wave (at various points in the room if you like), you would SEE what the driver / speaker and room make of it ...

If this is not theoretical non-sense, I don't know anymore, but this is the way I work, because this is the basis (I mean : for practice there's no one single sinus tone, but if one tone already works out wrongly ...).
Fact is : I could show you a SQUARE wave IN AIR, sent out by the PC, converted by the DAC, electrically transmitted through cables, put out by the speaker, caught by the microphone (sent back to the PC blahblahblah), a phenomenon which already fails in my old upsampling AudioNote DAC ... (read : only Sinuses come from that).

Moral : whether square waves (and variants) exist in real life or not (with my saying that a synthesizer is real life already), it's better to show them (sound them) if they are there. It needs measuring to see the differences in the first place, and it is exactly this making me buy the TwinDAC.
And this is where all changed (which comes to the Non-Oversampling theory -> Oversampling destroys the sound).

Regards,
Peter

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