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Old 24th August 2009, 17:33   #1
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Default Home Audio - Finally I measured what I am hearing

I always wanted to get a flat frequency response, and my home system's subwoofer was not tight and before venturing to treatment and other areas I wanted to know which frequencies I was not hearing right.

So got myself a sound meter to measure the frequency, and before doing the home I tested the car system, please see attached files for the graph.

Have a Kenwood 5XXX system, stock fiesta speakers, 12" jbl subwoofer, 4 channel jbl amp driving the sub and fronts.

Now that I know where I stand I want to improve it.

First things I want to do is get a tweeter, and eq the curve.

Need reccomendation for a 1/3 octave eq and nice pairing tweeter.
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Old 24th August 2009, 18:57   #2
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Interesting graphs reddream,

Can someone tell me :

1) Why those total dead spots at around 300-500Hz ?

2) Why are the high frequencies 4Khz+ so irregular on the graph (ie up and down frequently between 60-90dB)

3) Whats the difference between the green graph and the blue graph?

cya
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Old 24th August 2009, 19:25   #3
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@reddream, were these taken with a sweep generator or with regular music? This is too densely crowded to be from a sweep. If regular music, Rehaan, the holes are simply not enough content detected at those frequencies (not even harmonics) - just a coincidence. Not sure under what conditions were the green and blue graphs captured.
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Old 24th August 2009, 20:43   #4
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well IMHO you shouldnt even be using a sweep - you should use pink noise at 0 dbfs to actually measure - cos then you are sure of equal energy output from the sound source - and the differences in the actual graph would be due to the equipment and its deficiencies

so yes more information on how this graph was measured would indicate a bit more on what could be the cause of what you see there
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Old 24th August 2009, 20:45   #5
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Simple question how it is measured ?
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Old 25th August 2009, 09:26   #6
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The difference between the two graphs is one without the subwoofer.

This was from a sweep of frequencies. Just got a spl meter and installed the Room EQ Wizard. Room EQ Wizard Home Page

I just spent 15 mins on the car system to get this graph. Waiting for the weekend to get my hands on my brothers laptop to tweak the graph as much as possible.

I was more concerned on the 70 - 100 HZ drop, the huge fluctuations in highs could be because of reflections, need to see if I can get a simpler graph (averaged ) from the software.

Also, I think I found the reason for 70-100 hz drop, in my kenwood I had set the option as subwoofer from the rear pre outs, so I think it is adding a LPF in it. I tried setting it to rear speakers and felt the bass was boomy, need to measure and tune the cross over of the amp.
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Old 25th August 2009, 11:16   #7
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@reddream, your objective is understood, but it will help understand better if you described the process steps in detail. Speculative interpretation would be incorrect.
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Old 25th August 2009, 13:01   #8
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I have a sound meter, which will measure the db of what is playing.
So, if a particular frequency is played it will measure the db.

Now when a sweep is performed, it will talk to the software which is a generator and capture the db for that frequency.

The sound meter will be held at the listening point at the level of the ear to capture what the listener is listening.

With pink noise, all the frequency will play and my sound meter does not know the individual db, hence the sweep.

All the speakers are playing (front + rear) hence there might be reasons for cancellation in some frequency also.
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Old 8th October 2009, 07:10   #9
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Having negotiated my way through the maze of high end 2 channel home audio - tube amps, exotic cd players, turntables, electrostatics and all - and having come out of it, I can't help but think that listening would be the best way to find out what works!
I have simplified my system vastly, and find that it gives me the time/space to now just enjoy the music. I have all my CDs ripped with zero compression to an ipod with 60gbs memory. I play that plugged into a preamp coupled to a poweramp, connected to two high end standmounted speakers, and get brilliant music. For a few months, I had a tubed buffer with its own PSU between the ipod and the preamp, but I dumped that when I couldn't tell the difference.
It is probably not as good as what I heard in my earlier set ups, but I can't quite tell! I guess the fact that my tastes run to jazz, close miked vocals, and indian classical music helps here too. And as one grows older, the ears are not quite as good as before too, one more benefit of aging!
I also think that for audio, subs can be destabilizing, unless one spends a heck of a lot of money on the equipment and room treatment.
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