[-Richard-]

Hi PaulFolbrecht ~

Thanks for the information about the Supravox's low frequency and performance criteria... no wonder it works so effectively in an OB... at 50 hz with a little bit of baffle reinforcement it could almost work without the need for a low frequency "woofer".

I am very curious about your suggestion that:

"...the brain averages freq response over certain intervals"

does that mean that the brain compensates for frequency anomalies by somehow "smoothing-out" our perception of what is actually being (measurably) reproduced? If so... which frequency "intervals" does the brain perform that kind of smoothing operation in?... it might be interesting to keep that in mind when designing a baffle.

Warmest Regards ~ Richard

[PaulFolbrecht]

Yes, Richard, that's exactly what I meant.  I don't recall the numbers, unfortunately, but it's a very real phenomena with practical implications.

Using 1/3rd octave pink noise my baffles DO measure very flat.  I know XCortes measured his around +- 3dB from 45 to 12 Khz in-room which is very good for ANY speaker!  But measuring them anechoically (or theoretically with software) will show many spikes.

So, two things:

- In room they measure quite well because reflected energy diffuses the baffle effects.
- What anomalies are there are probably largely 'averaged-out' by the ear-brain.

[Rudolf]

"...the brain averages freq response over certain intervals"

does that mean that the brain compensates for frequency anomalies by somehow "smoothing-out" our perception of what is actually being (measurably) reproduced? If so... which frequency "intervals" does the brain perform that kind of smoothing operation in?... it might be interesting to keep that in mind when designing a baffle.

Richard,
this is quite complex. There is a general difference between the perception of peaks and dips. There is a relation between the width of a peak/dip and its height/depth. And everything changes along the frequency band. On top there is a VERY big difference between the perception of single tones or musical signals and the perception in a comparison or as an isolated signal.

Citing from figure 8 in http://www.acoustics.hut.fi/teaching/S-89.3480/2007/kalvot/karjalainen.pdf:

- In direct comparison, 0.5-1 dB deviations (per critical band or 1/3 octave) are just noticeable (many studies support this)
- Even 3-5 dB deviations cannot be reliably detected by experienced listeners (in normal acoustics) without comparison or well-known sound material (informal experiment)
- Response peaks easier to detect than dips. Very narrow deviations not easy to detect, unless they make long ringing. Pink noise the most critical test signal. Remarkable effects of listening room/headphones found (Toole&Olive, JAES 1988, no 3)
- Room reflections and reverberation complicate the perception: Loudspeakers with same on-axis response sound different in real rooms, due to directivity differences etc (Salmi&Weckstr?m, AES71, 1982)
- Room modes at low frequencies complicate the perception: More deviations from ideal allowed at low frequencies

[-Richard-]

Hi Rudolf ~

Extremely interesting information... thank you so much for taking the time to illuminate those very interesting insights you are kind to share with us.

I thought it very interesting that "Response peaks (are) easier to detect than dips."... also that "Even 3-5 dB deviations cannot be reliably detected by experienced listeners..."

One thing that has always struck me about live unamplified music is how transparent and easy to tolerate it is. Once the same performance is recorded it becomes "harder" sounding... more opaque, less "joined" to the air, even less intelligent... in the sense of the music sounding less connected to the underlying human emotional source. Sometimes recorded music sounds better than live music... this is particularly true for the voice... especially if the voice was miked. If the music was amplified in the performance this perception no longer applies.

Deb and I attend a series of free classical performances every summer in the Santa Barbara Museum auditorium (small intimate space designed for live performances) that gives young performers a chance to play before the public... sometimes I close my eyes during the performances and try to imagine that what I am hearing is coming from an audio system... just to see how the sound matches to my memory of my OB's.

Sometimes to my surprise the sound is very close. I have always found it interesting that when one listens to live music, the brain accepts what it is hearing with all the tonal, textural and sound-scale anomalies adjusted for "automatically".

Thanks again for your interesting information.

Warmest Regards  ~ Richard

[PaulFolbrecht]

Hi Guys

Interesting read. I may be considering these drivers in the near future and have one concern. I listen to music with friends, whilst doing chores, and don't mind gettin' my funk on (er, dancing badly, air guitar, air vibraphone ). I am wondering about their off-axis performance. I don't need sound staging or the highest highs most any time - and certainly not when off-axis and getting all funked up - but I would like music to still have that life, immediacy, and vibrancy... fun! Any thoughts?

Oh, and what is build quality like - I have read some mixed reports way back in the past, though recent reports seem to indicate pretty consistent sound quality.

Cheers
Raymond

Raymond,

Sorry for missing/ignoring this.

1) Build quality is extremely high IMO.  They look like precision instruments.  And the size of that electromagnet.

2) The fact is that all FR drivers beam treble BUT I think on an OB this is GREATLY ameliorated because of the bi-directional radiation: so much of the sound is reflected sound.  So, yes, the "sweet spot" - if there is one - is actually extremely wide.  My place is an open-concept house with the system in the great room open to the kitchen - I can listen about anywhere. with good sonics.