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Old 29th December 2008, 17:08   #76
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Originally Posted by Bass&Trouble View Post
By turning up the crossover dial to a point where the 50Hz tone is not audible any more, you have set the crossover to a frequency way higher than 50 Hz.
Well I cannot say it would be entirely not audible. When the frequency is about 32 Hz you can hear and feel the speakers vibrating but when you turn the frequency knob you can slowly feel the vibrations reducing and the hum also reducing. At some point you will feel that the hum has faded away a lot and I have left it at that point. Agreed that I might have actually set it at higher than 50 hz and not exactly at 50 or 60 hz. After setting it with the 50 hz tone, I also played few tracks and turned the knob little bit on both sides such that I get good bass from the speakers and dont get any kind of phat phat sound at about 2/3 max volume of the HU (which I would have other wise got when the frequency was set to about 40 hz or something).

@dinu - I shall take a pic and post it here. The amps are kept beneath the seats so I am not sure if I will get a clear picture but I will try.

I do not remember seeing any dots on my JBL 75.4 but I do remember seeing some dot on the JBL 3501. Are you sure that the dot on 3501 denotes 80 Hz?.


Meanwhile if some one can read my question in the following link and reply it would be of great help to me.
http://www.team-bhp.com/forum/ask-gu...ml#post1109245

Thank you.

Last edited by drvhplyevraftr : 29th December 2008 at 17:11.
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Old 29th December 2008, 19:41   #77
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Originally Posted by Bass&Trouble View Post
By turning up the crossover dial to a point where the 50Hz tone is not audible any more, you have set the crossover to a frequency way higher than 50 Hz.
I agree, you have to turn it to the point where the sound starts to fade, not completely disappear.
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Old 30th December 2008, 09:02   #78
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The dial only shows a min of 32Hz and max of 320Hz with no markings in between and I understand it is not a linear scale. As far as I know the dot (at the 10'O Clock position) in 75.4 is 50Hz
That's interesting. I wasn't aware of this. Any idea how the freq varies as we turn the knob towards 320?
Isn't the dot = 32hz? If the dot is 50hz, where would 32hz be?
For the sub, I tried with setting the am
p rear channel at a wee bit above 32hz/HPF - hopefully around 40hz. HU set to 80hz/LPF. The LF may have become a tad punchier - but can't say for sure. Could be a placebo effect too.

Last edited by shuvc : 30th December 2008 at 09:04.
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Old 30th December 2008, 11:00   #79
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That's interesting. I wasn't aware of this. Any idea how the freq varies as we turn the knob towards 320?
Isn't the dot = 32hz? If the dot is 50hz, where would 32hz be?
For the sub, I tried with setting the am
p rear channel at a wee bit above 32hz/HPF - hopefully around 40hz. HU set to 80hz/LPF. The LF may have become a tad punchier - but can't say for sure. Could be a placebo effect too.
32Hz is the min and it is at the 7 'O Clock position. The mid point is around 60Hz as I understand. I also validated it yesterday with a 60Hz test tone.
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Old 30th December 2008, 12:57   #80
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32Hz is the min and it is at the 7 'O Clock position. The mid point is around 60Hz as I understand. I also validated it yesterday with a 60Hz test tone.
Mid-point is 60hz !!!?? ie half turn?? So it goes from 60 to 320 in the other half turn?
Is the gain knob also graduated similarly?
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Old 30th December 2008, 13:24   #81
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Mid-point is 60hz !!!?? ie half turn?? So it goes from 60 to 320 in the other half turn?
Is the gain knob also graduated similarly?
Yes, it does. The problem is that the dial is not graduated accordingly and I feel that is an omission from JBL. You can look at closeup pictures of other amps where there is graduation and you will see it is a non-linear scale.

Gain knob, I'm not sure.

Last edited by dinu2506 : 30th December 2008 at 13:25.
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Old 31st December 2008, 13:30   #82
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Following is what I did on the monoblock and HU for the sub. I set the crossover to 150 Hz and set the LPF frequency on the monoblock to point to the dot. I disconnected the RCAs for the front and rear speakers and wanted to see how well my sub performed. At these settings, the sub seemed to play more tunes than when the HU crossover was set at 80 Hz. So I think by setting the crossover on the HU at 150 Hz and having the LPF frequency on the monoblock to point at the dot, I am making more use of the sub. I am however lacking the punch which seems to be a problem with the basstube that I am currently using. It sounds too boomy. I am planning to change to a sealed enclosure and see its performance. However the current settings on the HU and monoblock seems to make the sub play more. Any comments or thoughts?.
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Old 1st January 2009, 08:50   #83
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dude, just play around , settle with what sounds good to you. If you have doubts , post the settings you eventually arrived at, we'll let you know if you're doing anything wrong
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