| jrtiger |
I decided to test the frequency response of the Bose system in the 2004 MDX Touring. The following is my measurements and view and you may agree or disagree. First let me say that if you are a designer you may wish to be very objective about audio measurements and strive for flat frequency response, good dynamic range, and low noise and distortion. If you are an end user then your goal maybe very subjective. If you have adjusted the equalization to anything but flat, it really doesn’t matter because the only thing that counts is that it sounds good to you. I mean who has perfect hearing and that for the end users is the final reference transducer!
What I did was make a test tone cd using Sound Forge. I then set all the audio controls to their center position. I placed the inexpensive Realistic sound level meter in the drivers hearing area with the pickup mic pointed at 20 degrees above horizontal and facing the front widow. The spl meter was set to C-weighing for a flat response from about 32 to 10 kHz. I set the output level of the Bose system for a reference of 80 dB spl at 1kHz. I then ran a test with both left and right channels being feed the same test tone. Here are my results:
20 Hz not measurable. (The spl meter is rated down to only 32 Hz). I did not hear or feel any wave at this frequency. 50 Hz 98 dB, 100 Hz 87 dB, 200 Hz 80 dB, 400 Hz 76 dB, 800 Hz 70 dB, 1 kHz 80 dB (Reference), 2 kHz 73 dB, 4 kHz, 75 dB, 8 kHz 71 dB, 10 kHz 67 dB, 12 kHz 68 dB, 14 kHz 65 dB, 16 kHz 60 dB, 20 kHz 52 dB.
Balance test at 1 kHz at drivers position left channel 77 dB right channel 60 dB. Balance test at 1 kHz with spl meter in the middle between the two front seats. Left channel 77 dB, right channel 80 dB.
It should be noted that this is not a laboratory spl meter and the specs indicate a plus or minus 2 dB tolerance. The meter documentation doesn’t tightly define the frequency response boundaries. However I think it does show the general trend of the audio response curve in the vehicle. I did defiantly feel that there was a bass boost from the subwoofer which is indicated by the measurements. I do have a much more sophisticated measuring system and someday I may haul it out to the SUV and make some more measurements. Just thought the group might be interested in this test. |
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| elocutionist |
jrtiger, here's an Excel plot of your data, with Excel's own smoothing applied. I used a logarithmic scale for the frequency, and started with your data at 50Hz.
It would be interesting to see what the average frequency profile looks like for the road noise inside the cabin on the MDX. Seeing that with your data might be insightful.
Christopher |
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| jrtiger |
| Thanks Christopher, I appreciate you plotting the data. I was going to do it but then got lazy and just posted the values. I am not sure I want to test the road noise because on some road surfaces I don’t like the tire noise getting into the cabin. Without making any measurements I can subjectively convince myself it isn’t that bad. I do think you are right that it would be interesting and maybe if I can get up the nerve I might make some measurements. Also as you probably noted I did most of the test at one octave steps (at least at the low end) and it would be interesting to make more measurements to get a better view of the response. Especially for me in the presences band around 1 kHz to 4 kHz. I also think I might try and see how well I can adjust the audio control to create a sweet spot at the driver’s location. Wish we had a parametric equalizer to flatten the response. Treble and bass are not really going to cut it but I think I will try and pull down the low end a bit. Again thanks for the graph although unfortunately it shows a disturbing response curve... at least for me. |
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| emoss |
Now I understand why the Bose sounds so lousy. All lows, no mid-range boost, and non-existent highs.
I recently swapped out the front speakers for the LF drivers from a new Infinity 60.5cs component set I bought for $90 bucks, and the sound was markedly improved. Can't wait til I have the time to add the crossovers, replace the tweeters, and get my Polk GNX in place.
Thank for the stats! |
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| OrinocoMDX |
jrtiger its good that you took the time to try this out but using full octave as your reference points is going to give you quite a view that is skewed. If you want more of an accurate reading start trying with 1/3 octave points. Also there are many variables that you might be forgetting about in stock systems. One is that at higher decibels you will lose out on your bottom end. You might try say 60db test then a 90-95db test. This will not only show the responce but will also make another excellent point of "is the system linear". I dont know the specs on the stock speakers so im not even going to bring in effiency. You also took measurements at the front of the vehicle so you also have to take into consideration the cabin gain for the lower frequency waves which would give a good explanation as to why you have the wave you do. Another drawback of the stock system is the tweeter locations in the 04 as they are cross firing and the left tweeter is going to have a huge problem with the hump in the dash right above the instrument panel. However the stock door speakers do have a forward design which I like and co-ax's would be benificial to sound quality(if you didnt want to change the vehicle at all)
On a side note bose systems usually have the tendency to be "no highs no lows it must be bose" which again translates to what the graph shows if you consider lower frequencies being higher because of cabin gain
All in all very good job and good information for people out there to see why changing certain things will make a difference. |
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