# Headunit and amp eq tuning.



## Kol12 (Nov 20, 2015)

Hi, I've almost got my system up and running, gear is:

CDT CL-62 Components
Eclipse XA2000 Amp
JVC KD-R736BT HU

My headunit has eq settings for frequency, level and Q for Bass, Mid, and Treble. 

I'm unsure whether these eq settings have any effect if your running an external amp? If they do I'm guessing the HU eq's need to match the amp crossovers for the amp's crossovers to be effective? Seems confusing..

The CDT's play down to 50hz so I have set the amps hpf to 50. 
Where do I start with setting up the HU eq's?

My available HU eq settings are found here: Brightness Adjustments; Sound Adjustments - Jvc KD-R736BT Instructions Manual [Page 19]

Thanks.


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## Alextaastrup (Apr 12, 2014)

The best way is to switch off the crossovers on the amp and use them only on HU. I will recommend 63Hz instead of 50Hz for 6,5' midbass.


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## Kol12 (Nov 20, 2015)

Is it better to use the Headunit crossovers rather than the amps? For some reason the Bass boost on my amp isn't having any effect either..


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## Weigel21 (Sep 8, 2014)

Bass boost is typically shunned, as it's VERY easy to induce distortion or even clipping. See, for every 3dB of boost, an amp is asked to double it's power output. 

Frequency response specs are always iffy, unless there's a response chart with it. See, the CT's may play down to 50Hz (looks like 55Hz to me on their website), but how well is unknown. Typically, the frequency response specs assume a +/-3dB variance in the output throughout the response range. I'll go ahead and stop here on frequency response, as it can get quite confusing, and I'm horrible at explaining things. 

Still, I'd not cross the speakers over as low as you are asking, in fact, I'd probably not go lower than 80Hz, unless you are relying solely upon the CDR's for your lows. Still, chances are they won't have a lot of oomph below 80Hz or so. 

Now, using two crossovers together is another thing typically shunned. So use the crossover of the amp or HU, but not both together. 

Your HU's EQ will definitely affect the output, even with an external amp. The frequency is obviously the frequency greatest affected by the boost/cut. Level is the boost/cut. And Q is how wide the effect of the boost or cut is in terms of affecting frequencies near the selected frequency. 

The EQ is typically used to compensate for anomalies (peaks or dips) in the speakers response curve. However, many can't properly EQ by ear (myself included).


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## Kol12 (Nov 20, 2015)

Yes sorry, it's 55Hz the CDT's play down to. What's the reason they wouldn't have any oomph below 80Hz? At this stage they're providing the lows..

To be honest I think the HU's crossover/eq settings are constantly set to the factory set values. I'm not sure you can actually disable them? 

Actually I may be confusing the HU eq settings as a HPF. The HU does actually have a HPF setting that can be turned on or off but it's lowest cutoff is 100Hz so in this case I think my amps HPF will work better. 

So what is the difference between a HPF and the EQ settings on my HU for frequency? 
In my case my Bass frequency available settings are 60/80/[100]/200 100 being the factory setting. These are the EQ settings I think are permanently active?

What do the Q numbers available mean in terms of how wide the effect of boost/cut is? For example my Bass Q options are [Q1.0],Q1.25,Q1.5,Q2.0


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## Kol12 (Nov 20, 2015)

This question is a little off topic but how do I splice my thin tweeter wires to my 12 gauge speaker wire? I'm guessing using a 12 gauge butt connector would be far to big for the tweeter wires? The Tweeter wires are about as thin as amp turn on lead. Actually here's a pic:


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## Kol12 (Nov 20, 2015)

Sorry I think I see how the HU EQ works now. It basically allows available frequency's to be boosted or cut right?

But how does that interact with the HPF on my amp? For example if I set the HPF on my amp to 55Hz and I want to boost the bass with the EQ on my HU the lowest frequency available is 60Hz, is that close enough anyway or should I leave the HU bass level at zero and boost it with the amp instead?

So if the the HU EQ levels are set to zero does that mean the EQ is set as flat?

It's strange, the HU factory flat setting has the Bass at +5 and Treble at +5. Hardy call that a flat setting..


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## gijoe (Mar 25, 2008)

Alright, it sounds like you need some help.

The EQ, as you discovered, boosts or cuts at a particular frequency. The Q is how wide or narrow of a range that is affected. Think of the particular frequency as the top of the hill, or a flagpole. I high Q would represent the flag pole, and a low Q would be a hill. Does that make sense?

The high pass filter (HPF) is the point at which the high frequencies are allowed to pass to the speaker, but the low frequencies are cut out. I wouldn't set this below around 60hz even for a great pair of 6.5" speakers, 80hz is a safer choice for most speakers that size. 

Speakers do not play the full audio spectrum by themselves, that's why we use subwoofers, mids and tweeters to cover the entire audible spectrum. The size of the speaker plays a very big role in how high or low it can play, the smaller the surface area is, the more excursion that is needed to produce the same output. Low frequencies require more output to sound as though they are at the same level as the high frequencies, so pushing a small 6.5" speaker down to 50hz is asking a lot. The 6.5" has to move a lot in order to produce frequencies that low. This much excursion can beat a speaker up quickly, the cone could be reaching it's limits mechanically, and the power required to do this could be causing thermal issues as well.

Even if you can play the speakers down to 50hz, the moment you turn up the volume, they have to work really hard. The more the cone moves, the more distortion you'll have, 50hz is subbass, not midbass. If you don't have a subwoofer to cover that area, be very careful about trying to use a small 6.5" speaker to do it. I wouldn't run even the best 6.5's that low.

Don't confuse a flat EQ setting with a flat response. Just because the EQ is set flat, doesn't mean that the acoustic response is anywhere near flat (and flat isn't the most desirable final tune anyway). Add a proper subwoofer, and stop using the bass boost. You may be tempted to get as much bass from those speakers as possible, but crossing them too low, and boosting them is only going to make them sound worse, and burn up quickly.


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## Alextaastrup (Apr 12, 2014)

I will stress out that the playing diapason for a speaker should not include its own resonance frequency, at least 1 octave away. Then it will play cleaner. 3 way system is better in this way, as it allows to choose right crossover points for a set of component speaker system.


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## Weigel21 (Sep 8, 2014)

If you can, solder. I HATE trying to mess with anything that small when it comes to crimp connectors. 

As said, the HPF is a High Pass Filter, which allows the frequencies above the said crossover point to be played unattenuated. Frequencies below the crossover point are attenuated with a roll off slope of xxDB/Octave. Your HU's HPF probably has a 12dB/Oct slope. 

A bit odd that the HU's FLAT EQ setting boosts anything, usually a FLAT EQ setting is no boosts or cuts made with the EQ. 

As said, a truly flat frequency response isn't desired (though drivers with a flat response are) funny as they may seem. Human ears are much more sensitive to frequencies within the typical vocal range (I think it's around 80Hz to upwards of 6kHz) and when frequencies get much higher or much lower than this range, our ears don't seem to find them as loud. Though most people's ears are more sensitive to higher frequencies than lower frequencies. 

Now given most peoples ears aren't terribly sensitive to frequencies below roughly 80Hz, a lot would end up really boosting such a small driver to get the output to seem as loud as other frequencies. Which as said, will push the speaker beyond it's limits.


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## Kol12 (Nov 20, 2015)

I don't have a solder but I might see if there's someone around who can do it for me. Is it normal for some tweeters to come with small wires pre-attached and to have to join them to thicker speaker cable? In my case it's 12 gauge speaker cable! 

Played around with HU today and couldn't find the HPF, will have to check manual again! [edit] checked manual and the HPF is only available when the Subwoofer output is enabled.

The flat EQ boosted is a bit odd and I will check again to see if it really is the case.

Why is a flat frequency undesirable? Does this mean you need to tweak your EQ's from a flat setting? I have to say that with my HU flat setting my speakers don't quite sound right to me but I'm not sure what it is. Have only got one tweeter temporarily hooked up at the moment as well.

Another thing I notice having the right side speaker installed now is that I feel like I don't know if I'm hearing the left speaker. (We drive right hand side in NZ) 
I guess this is time alignment? I faded slightly more to left and it seems more balanced..


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## Kol12 (Nov 20, 2015)

This is slightly off topic again I suppose but I'm also getting a battery drain. I've got a jumpstarter and it starts fine but after 1 minute with the engine off and the stereo going it drains.

I had been having trouble with the battery throughout my install but not as constant as it is now and it seems to only be since the right side speaker went in.

I disconnected the amp power wire from the battery terminal today and powered off the 
HU with no change. Does this rule out the amp and HU? Does it look more like short somewhere perhaps?


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