View Full Version : Spectrum analyzer displays mostly high frequencies

2009-01-03, 20:44
Hi all,
Newbie here with my first posting to the Forums.
I've had an SB3 for a few years, and recently bought a Duet, and love them both. Revolutionary products in the consumer audio market, in my mind; I suspect nearly all of you will agree with me.
Here's the problem: Back when I first got my SB3 (with <6.5 version), I put the full-screen Spectrum Analyzer on the display to test my visual/audio frequency correlation and was disappointed to find that the display didn't seem to jibe with my perception in that lots of treble was activating the display bars, but not much in the bass was showing up. (I am not an audio professional, but have extensive experience with running live sound reinforcement systems, and lots of practice tweaking tone controls, graphic equalizers, and parametric equalizers.) I searched through the Forums for postings on the subject and found the old stuff from Vidur (gone from the Forums since summer 2005), and not much since. It looks to me as if this display has been ignored since then and it needs to be revisited.
Here's why-
I downloaded some MP3 test tones and played them through the SB3 with the Spectrum Analyzer display (and simultaneously ran the SB3 output to a Real-Time Analyzer to verify the frequency). This test verified my suspicion- most of the 32 bars in the display are for midrange and up, with just the single far right (or left) bar activating for the bass frequencies. I've got some pictures, but you can perform this test for yourself with readily available test tones from a test CD or Internet. Send a 1 kHz (midrange) signal to the SB3, and 3 bars will show-
(I used 32 . and I to show it graphically). That single . on the left is the bass and the 28 .'s to the right are the treble. This is seriously skewed, and I think someone may have coded it with 64 bins, but it is only displaying the top 32 (or some such simple coding error).
What are your thoughts on the 32 bar Spectrum Analyzer display? Is it entertainment? Eye-candy? Useless? Possibly useful if it were showing the full audio spectrum in a properly proportioned and weighted manner? (That's my position).
Thanks in advance for your kind and considerate replies.

2009-01-04, 00:13
I did notice this as well

2009-01-04, 08:00
There was some discussion of this a long time ago. Basically, the developers know it isn't accurate, it was never intended to be, it's just a "screen saver" or realtime animation if you like.

I doubt it will ever change, not now anyway.

2009-01-05, 19:06
Thanks for the support and comments.
I didn't want to embarrass anyone, but since you brought up the fact- there are animated 'visualizations' by the thousand available (in full color and high resolution) for players such as WMP and Winamp. So my point is that if the developers at a class act like Slim Devices want to enhance(?) their product with a low-resolution, monochrome clone of the classic Mike Lynch Winamp plugin from 1998 (http://www.winamp.com/plugins/details/165966), they should at least do a good job, and make it look and perform as much like the original as they can.
BTW, I think they did OK with the VU Meter display (http://www.winamp.com/plugins/details/41743), considering the limitations of the display.

2009-01-05, 20:17
The spectrum analyzer is fed by a real FFT calculation, but there's an emphasis function applied to make it visually more interesting. There's an archived thread on this somewhere with the exact details - I can't remember off the top of my head.

Similarly, the VU meters don't represent the actual voltages - dBfs would be more relevant for a digital player, but then it would have the same retro appeal as analog meters, which needed indicate the "too hot" range.

2009-01-05, 20:54
would it be possible to show the freq #s or freq range under the bars so you know whats being represented?

Mark Lanctot
2009-01-06, 11:50
Yes, it's eye candy. Nice eye candy, but eye candy.

For me, I notice that the display for FLACs seems to be slow and jerky - for MP3s much better. But for both, in my case the bass bars tend to always max out regardless of the musical content, with the other bars only moving occasionally. This may be due to ReplayGain.

At any rate, the developers have much more pressing work to do and I would really rather not see them deferring something important just to fix this (nice) eye candy, so I haven't voted in the poll.