A question for the audio gurus

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A question for the audio gurus

Post by Sonac » 14/03/19 18:03

So I have been incrementally upgrading my Rev2's audio system.

I have put a Sony MEX-GS820BT head unit in which can push 100w x 4 channels. It says 45w RMS per channel but from what i've heard about these head units they have no problem running much higher than that all day. Some guy was pulling over 70rms from his since it has an integrated class D amp which just keeps giving. Never really gets hot and doesn't seem to under power any speakers. The speakers give out before the unit.

I have two Vibe slick s5c 5.25 inch drivers in the doors and Vibe tweeters in the sail panels. The drivers can do 80w rms and 240w peak. I replaced the crossovers with some higher quality Kinetic Segrigator crossovers.

I have two 4" coaxial FLI Integrator 4's in the rear. 50w rms and 150w peak. I have them turned down a little in the headunit to balance out the sound in the cabin.

I stuck closed cell foam inside the doors and made foam rings to go around the drivers to improve midbass.

The entire system sounds really good but I decided to take it one step further and aquired a Focal Expert 10 inch subwoofer with duel 4 ohm coils. I'm running it at 2 ohms into an Alpine amplifier. The sub can so 250w rms with a 500w peak and my amplifier can do 350w rms. Its in a sealed box from MR2 Ben installed behind my seat above the cubby hole (and technically inside since it has a section which slots into where the cubby used to be).

My question is now that I have a subwoofer handling the bass, the door drivers only need to be handling the midbass. My head unit has an option for high pass filter and i'm wondering if I should be using that or not. I assume it doesn't affect the line level output to the subwoofer.

If anyone has any tips i'd be very grateful.



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Re: A question for the audio gurus

Post by MR2DI4 » 14/03/19 21:51

You can probably work it out from what it sounds like. Its been a few years since I did audio for a job, you used to be able to bridge the amp and switch a low pass filter for the Sub. The appear to have moved to dual coils instead of as bridged amp. You should be able to use that high pass from the head unit without it affecting the output to the sub.

At the end of the day the sub can end up handling very low end and you can either not hear it that much. Got a factory sub in the Subaru, certainly that cone is moving but the musical content from it is limited.

I remember higher end systems just moved to an active crossover, each of the outputs then just went to a dedicated amp channel for each speaker. The head units have go more sophisticated so maybe you can change the crossover frequency and do a few more things there. Don't know if you have any level controls. The active crossover allowed you to custom set everything.

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Re: A question for the audio gurus

Post by SonicSW20 » 15/03/19 13:43

Yes, you should be running a high pass for the front speakers. You should be running a high pass anyway, as those speakers can't produce those low frequencies anyway.

The high pass will only affect full range outputs. The low pass filter will only affect the rear preouts unless you have the head unit set in subwoofer rear speaker output mode, in which case the low pass will affect rear speakers as well.
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Re: A question for the audio gurus

Post by Sonac » 15/03/19 22:23

Yeah you can adjust the high pass filter frequency on the head unit. I turned it on and it seems to sound good.
I can't remember the exact value but I set the high pass filter up to cut out what the sub is doing. It sounds far better.
I only have my subs' amp set to about 25-30%. I see no reason to push it higher. I'm not trying to create a super bass heavy system but rather balance out the sound.

Thanks everyone

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Re: A question for the audio gurus

Post by jimi » 15/03/19 23:29

Once your happy - ish I'd advise you to take a note of all your settings especially the head unit configuration, because if you happen to disconnect your battery for any reason you will probably lose the lot.
It can be a bit of a nightmare trying to remember all the settings just to get back to where you were especially if it's been a while since you set it up ................. ask me how I know :crybaby:
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Re: A question for the audio gurus

Post by SonicSW20 » 16/03/19 0:06

Sonac wrote:
15/03/19 22:23
Yeah you can adjust the high pass filter frequency on the head unit. I turned it on and it seems to sound good.
I can't remember the exact value but I set the high pass filter up to cut out what the sub is doing. It sounds far better.
I only have my subs' amp set to about 25-30%. I see no reason to push it higher. I'm not trying to create a super bass heavy system but rather balance out the sound.

Thanks everyone

Yep, having the high pass and low pass set to the same frequency is usually about right. You then need to play with the slope setting to fine tune it. The slope setting is how "steep" the filter is, measured in dB/octave, but rather unhelpfully the Sony just has 1/2/3, and no indication in the manual as to what 1/2/3 actually are. I assume shallow / medium / steep!

Now you have it set up, run some polarity tests. https://www.audiocheck.net/audiotests_polaritycheck.php

This will let you confirm you have the front speakers wired the correct way around, and that the sub is in phase with the rest of the system. If the sub is out then chances are it's 180 degrees out to to polarity being switched. You can simply reverse the polarity in the stereos settings, or swap the wires around.
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