dave clark

using a Radio Shack dB meter and Stereophile Test CD2 - not that accurate, but gives you an idea of what is going on. Will run again and see what changes I can get with the bass/treble controls, as well as the Fade settings.
With the bass and treble to 0, measured with me in the car and the dB meter at the right shoulder, driver's seat :
20k - 54(dB)
16k - 66
12.5k - 68
10k - 74
8k - 75
6.3k - 76
5k - 75
4k - 76
3.15k - 76
2.5k - 79
2k - 77
1.6k - 79
1.25k - 78
1k - 78
800 - 75
630 - 82
500 - 80
400 - 80
315 - 74
250 - 76
200 - 80
160 - 84
125 - 89
100 - 91
80 - 92
63 - 94
50 - 95
40 - 98
31.5 - 98
25 - 90
20 - 78

meaning cut the bass a bit and boost the treble a bit and things should sound pretty good. Now this is with the car sitting still without the engine running. Naturally, road noise will come into play.

kstirman

The response is not linear below 125Hz. Use this chart to compensate:

http://www.svsubwoofers.com/faq_rscomp.htm

Kelly

selmeralto

I think the figures that Kelly refers to are interesting but I'm not quite sure what to make of them, especially if the suggestion (not made specifically by Kelly) is that the sound of the larger Bose system would be improved by returning the bass control to zero or even to the plus range. It will be interesting to see Dave's figures for the bass and treble controls. But Dave's first set of figures only confirm what I actually hear--which is my ultimate test for audio fidelity.

And the confirmation is only partial anyway, on my view. Even if the claim about the nonlinear measurement of energy in the Radio Shack equipment is true, there is no necessary connection between that and how the sound is heard, especially when we are talking about subtle disrimination such as at the lower end of the hearing spectrum. Imagine a meter that measured energy from 20,000 - 30,000, with non-linear reading from 28,000-30,000. It would hardly matter since we don't *hear* those frequencies. In the end I'd rather trust my ears.

Also--and I realize this is ad hominem--the "need" for bass compensation mentioned in the site in Kelly's link is advanced by a company whose business is make money by selling sub-woofers.

kstirman

Actually, if you correct the figures, the measurements would imply the bass is very signifigantly boosted, which is what I heard in my test drive. I would say this is true for virtually every Bose system I've listened to.

I provided the link to the SVS site because it was the first I could recall off the top of my head, and because I like the explanation. Those figures are not made up by SVS, and are very easy to measure with a more accurate (and expensive!) system. The Radio Shack meter is a great tool, and extremely cheap for those of us that believe in measurements as a tool to reproduce results under varying conditions, even if those results are not flat.

I agree that your ears are the only true measurement for yourself - as Hume said, there's no debating taste.

Kelly

selmeralto

My apologies, Kelly. You are right: I misunderstood the figures. It turns out they do support my aural sense of the bass boost.

As for Hume, that's a discussion for another time.

dave clark

Yeah the Rat Shack SPL meter has some shortcomings. But when corrected as the site suggests, then the bass is boosted even further - which is what I hear when it is set to 0. Using the Audiopilot is even worse, boosting the bass much like a "loudness" button does - not natural unless all you are after is exagerated bottom end and no sense of slam or "texture" in the bass frequencies. Okay at low volumes but not under normal listening.
I use the term "texture" not in terms of feeling the bass, but in terms of transparency and articlulation. Both of which are clearly missing when all one gets is boom da'boom. Listen to some Bill Laswell dub bass playing and one should hear the strings and individual notes - not just the deep warbling of a bass guitar.
Same with Spaceways Incorporated Nate McBride's playing on their last CD - really deep and powerful but plenty of articulation and "texture", you can visualize the strings vibrating.

mmm

Corrected figures below. I rounded up to the next decibel for fractional decibels (so for a 1.5 dB correction, I added 2 dB).

20k - 54(dB)
16k - 66
12.5k - 68
10k - 74
8k - 75
6.3k - 76
5k - 75
4k - 76
3.15k - 76
2.5k - 79
2k - 77
1.6k - 79
1.25k - 78
1k - 78
800 - 75
630 - 82
500 - 80
400 - 80
315 - 74
250 - 76
200 - 80
160 - 84
125 - 90
100 - 93
80 - 94
63 - 96
50 - 97
40 - 101
31.5 - 101
25 - 95
20 - 86

eccles

Is your system base or Bose? Someone ran a similar analysis on their Bose system some time back: https://www.rx8club.com/series-i-interior-audio-electronics-24/bose-system-frequency-response-measurements-9011/

mmm

Based on this chart, it seems that a bass setting of -6 only affects frequencies from about 31.5 Hz through 800 Hz, and peaks at about a 2 dB drop. And a treble setting of +6 (look at the chart following the one I linked to) seems to affect frequencies above about 800 Hz, and likewise peaks at about a 2 dB boost.

If that's right, a setting of -6 bass, +6 treble would bring things closer to a neutral response, but wouldn't smooth things out completely.

That said, it seems to me that some bass boost is appropriate, given that there is a fair amount of low frequency noise in a car when you are driving. The lack of sufficient treble seems to be the bigger issue to me.

Which suggests that a fix something like this one might be appropriate.

dave clark

I have the Bose system, and truth be told, there is no way I was getting 101dB at 31.5 while I sat in the car. So I am tossing the readings out for now til I can figure out what the deal is...
yeah it was loud and the fact that it has credible output down that low is very impressive.
Then again (gasp, horrors) it is car audio! I mean with all the noise of the road and the car itself should we expect REALLY good sound. I know I want it, but is it really possible? The RX8 is rather noisy (love it) compared to my Pasat, and the Morel drivers in the Pasat can't come close to the bass levels in the RX8.

MrWigggles

Actually, the Rat Shack meter is pretty good at matching the dBc curve. It is dBc curve that isn't quite flat. 3dB down at 31.5Hz isn't bad for a simple meter and is very close to the dBc curve. Compensation on the upper frequency end should also be done for the dBc curve.

Anyway, Dave what volume level did you test at? When I play music at about 30 the loudness function is basically gone so it is not that much of a problem. It sounds fairly balanced at that point with a decent amount of bass boost to compensate for road noise which is bass heavy.

It also better to use 1/3 rd octave pink noise instead of pure sinewaves. Dave, PM me your email address and I will send you some 1/3 rd octave test tones.

-Mr. Wigggles

jonalan

30!!! Holy $4it! Are you serious? I don't think I've ever gone above 18.

MrWigggles

With some newer CD's, 30 is very loud, but for most of my collection 30 isn't too bad.

I have SPL meter somewhere. I should do this test myself sometime.

-Mr. Wigggles

dave clark

the volume was set at 16 I believe, which for me is plenty loud. When running the sweep, I was actually afraid that the speakers could not handle the levels as things were starting to rattle a bit.
SPL levels on RS unit at 80dB is plenty loud enough.
Issues are that the interior is small and so one can expect lots of problems with reflections and such.
While Bose is not "high-end" the sound is acceptable in terms of tonality - especially on CDs, though FM radio with all the comrpession still sucks.
Still prefer the bass at -2 and treble at +3 with audiopilot off.

MrWigggles

Dave,

If the test tones were full amplitude sine waves (i.e. -0dbFS), then 16 was probably a good setting for testing.

-Mr. Wigggles