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Old 20th December 2008, 13:07   #1
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Default Crossover frequency setting in HU vs Amp

Small query on setting the crossover frequency on HU versus Amp. Which is recommended?

1) Setting the Crossover frequencies at the amp and leave the HU at "Through"

2) Setting the Crossover frequency at the HU (say 120Hz) and leave the amp at "Flat".

I have a JVC AVX800 HU that has crossover at 80, 120 or 150Hz and JBL GT5 A604 four channel amp and a JBL GTO3501 monobloc.
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Old 20th December 2008, 13:19   #2
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No idea about the optimum setting in Car's

But for my Home Theater system, I ensure that both the Amp and Sub-Woofer is set at the same level.
i.e. Set the Crossover frequency at the Amp to 100Hz and also the Sub at 100Hz.

In case one wants more usage of the Sub, then set both to 120Hz
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Old 20th December 2008, 13:25   #3
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Quote:
Originally Posted by Fillmore View Post
No idea about the optimum setting in Car's

But for my Home Theater system, I ensure that both the Amp and Sub-Woofer is set at the same level.
i.e. Set the Crossover frequency at the Amp to 100Hz and also the Sub at 100Hz.

In case one wants more usage of the Sub, then set both to 120Hz
I think you did not get me. I was not asking about the optimal frequency setting. I have the option of setting it either in the HU or at the amp. Which is recommended, since setting it at one place renders the other redundant. I see a slightly better performance when the settings are done at the amps compared to setting it at the HU.
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Old 20th December 2008, 15:34   #4
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There is no rule. Whichever offers greater flexibility for the requirement would be the choice.
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Old 21st December 2008, 11:24   #5
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Not necessarily redundant you can use both in conjunction if you like. usually either one is enough. there is no such thing as optimal in it. but my guess is cutting the audio out at the source is better usage of all the facility your head offers you. also should make for a slightly cleaner final signal. probably might also make optimum use of the amp itself as it has less cleaning to do. but i'm no electronics guru.
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Old 21st December 2008, 18:45   #6
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the settings available in my amps are not as flexiable as those available in my HU. So using the HU settings makes most sense but...the HU settings need to be reset every time a car is given for servicing while the amps setting are not disturbed.

now lets take an example:
Set HU HPF to 6db/oct at 80Hz
Set amp HPF to 12db/octave at 80Hz.
using these together will give you an effective slope of 18db/octave (if both the HU's 80Hz and the amps 80Hz freq are actually the same).

Cascading the amp's filters and HU's filters requires careful planning and understanding but can prove to be very satisfying and flexible because one can produce "quasi-slopes" as shown on this link (those who dont know danish please excuse me, but I dont think there is a need to know danish to get the jist of what is being explained)
Torben's hi-fi side emne: Steen duelund's 3 vejs synkron filter
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Old 21st December 2008, 19:20   #7
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Phew, that was a bit heavy for me. Unfortunately, my HU does not have slope adjustments, just 3 freq settings. I found setting the amp filters a bit better in terms of achieving a better tonal balance. I have left the HU filter at "Through".

I guess it is all left to which offers better flexibility. Thanks for all your answers, appreciate it.
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Old 22nd December 2008, 12:35   #8
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Guys,

I have a similar setup and similar query, hence posting it here for some help.

I have the JVC AVX 44, front and rear speakers powered by JBL 75.4 and the sub GT5-12 powered by JBL 3501 monoblock.

I had a Sony MEX-R1 HU earlier and recently switched to the AVX 44. On the Sony I had set the HPF to OFF and LPF at 120. I want the same settings to be effective on the AVX 44 and am little confused to get it done.

The HPF has two options on the 44, they are Through and On. The document says, set it at through if the sub is not connected and to set it at On if the sub is connected. Since I have a sub I have set it to ON.

There seems to be no LPF on the 44, there is an option for Crossover which says the cross over frequency between front/rear and the subwoofer. The options for the crossover settings are 80, 120, 150. I have currently set it to 80.

On the JBL 75.4, I have set it to HPF and set the frequency at about 50 for the front and rears speakers.

On the JBL 3501 connected to the sub, I have set the LPF frequency to about 80 and the HPF to 30.

There is also an amplifier gain on the HU which says can change the maximum volume level of the unit.
The options are
off - deactivates the built-in amplifier,
low power - if the maximum power of the speakers are less than 50 w
high power - maximum power of the speakers are more than 50 w

I have left it at off since I have an external amp JBL 75.4

Also there is a speaker size setting for the front/rear speakers. If the speaker size is greater than 5 and 1/4 inch, it needs to be set to large, if less than that it needs to be set to small. I however did not notice any difference when it was set to large or small.

Can some one take a look at the settings and let me know if I have set everything correctly. If anything needs to be corrected, please help me with that.

Thank you for your help.

Last edited by drvhplyevraftr : 22nd December 2008 at 12:40.
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Old 22nd December 2008, 12:58   #9
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Quote:
Originally Posted by drvhplyevraftr View Post
... I have the JVC AVX 44, ...
You know what? You beat me to this post. I have exactly the same query. I gave my car for some work and they removed battery wires and all the settings on the HU went for a toss.

I would want to know the exact same things as I also have the AVX 44. Front JBL comps (JBL GT5 500c), NO Rear speakers, + Sub: JBL CS 1204 + Amp: JBL GTO 504
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Old 22nd December 2008, 17:55   #10
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1) you need to set that particular HPF setting to ON.
2) your crossover is the LPF that is what designates the cutoff frequency.
3) Depending on the size of your speakers you could bring it lower to about 40hz it would make the sound a little warmer inside the car if it is a sedan or boomy for a hatch.
4) please turn off that HPF or atleast bring it down till 18-20 hz 30 kills all the sweet low frequencies your sub and amp are capable of.
5) AMP GAIN i believe is for when they are connected to HU directly and not through an amp.
6) SPEAKER size setting is again only for speakers plugged to HU.

@KHAN sir i would gladly set it up for you for the simple joy of listening to this setup.

Last edited by valhallen.282 : 22nd December 2008 at 17:58. Reason: added text
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Old 22nd December 2008, 18:23   #11
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Thank you valhallen for the clarifications. What should I set the LPF (Crossover) on the HU at?. Currently I have set it to 80. Is this correct?.

Like you have said, I will turn off the HPF on the sub amp and lower to about 40 hz on the JBL 75.4 that are connected to the front/rear speakers.
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Old 22nd December 2008, 18:47   #12
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Quote:
Originally Posted by valhallen.282 View Post
.. @KHAN sir i would gladly set it up for you for the simple joy of listening to this setup.
Any time mate. let me returnm back from the GQ drive and we can then meet on some weekend for this.

Believe me, this whole ICE/Hz,Khz, etc etc is all greek to me. I can't understand any of this. Even the term 'newbie' would be an insult for my ice capabilities -- it's soooo bad.

Cheers,
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Old 22nd December 2008, 18:54   #13
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I do it from the HU since its digital and the potentiometer type setting in the amp is analog.
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Old 22nd December 2008, 18:57   #14
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I would not advice running car speakers at the perilously low 40Hz considering that you have a sub. It will cause a lot of sub bass to be routed to the speakers. The most prominent negative effect of this will be noticeable in its midrange reproduction. The power handling will be greatly compromised. And, the subwoofer and component speaker will overlap over the 40-80Hz band and cause bass to sound poor. Besides, 20Hz to 40Hz is too small a band for the sub to be operating in. There will be very little to no information running to the sub with regular music.

Even if you set the HPF for speakers at 40Hz, please dont try to play the system as loud as you would with 80Hz.
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Old 22nd December 2008, 19:06   #15
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Hmm Is HPF at 125 & LPF at 80 a correct setting? This is at HU

I have tried both 80 & 125 for speakers & found that the fronts(EL 4.1) sound better at 125.
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