amp gain w/different box, grounding kits?

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inoitall

Member - Posts: 28

Joined: March 31, 2008

Posted: April 18, 2008 at 10:12 AM / IP Logged

I have a few questions I need answered. To start, my friend has an amp which is currently powering 2 12" subs. Those subs are in a bandpass box (yes I know yuck). He has the gain set properly to 1/2 using a test tone cd. He has the low pass crossover set properly and has the bass boost at 0. He wants to replace the bandpass box with a ported box which Is already made. What he wants to know is... does he need to adjust the amps gain at all? I know a bandpass box doesnt have the output that a ported box does, and his amp isnt even stressing the subs. The amp isnt clipping it all, so he was just wondering if he could leave the gain where its currently at?

Ok now my question. I have 2 batteries, the main and 1 in my trunk. I have read about these grounding kits that allows you to make several grounding locations go to 1 point. For instance you can ground the battery, engine block, headers, and so on to 1 location which in turn would help overall performance. Also, I was thinking about getting 2 of those, 1 for each battery. The one in the trunk I would ground the battery to, along with my cap, and my 3 amps. That would give each amp and cap 2 grounding points. Would that at all help, or would the possibly creat a ground loop, or solve a ground loop problem (which I have with 1 of my amps)? Thank you.

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: April 18, 2008 at 10:29 AM / IP Logged

How do you KNOW the amp isn't clipping? One of the bad things about bandpass enclosures is the fact that nearly all of the non-linearities caused by clipping and over-excursion are filtered out... You simply don't hear them, even if they are happening. That amp could be BADLY clipping, and you might never know it unless you are viewing the waveform on a 'scope. At high enough levels, yes, you CAN hear those distortions, but it has to get quite a bit higher than a vented or sealed enclosure.

Also, if output is what he is looking for, then the bandpass IS THE WAY TO GO! The bandpass is HIGHLY efficient, significantly moreso than the vented (and especially the sealed) enclosure.

As far as your grounding question: If you can bond multiple points together, you may or may not benefit. If you are already experiencing ground loops, then I suspect a ground issue at one or both of your batteries, as you do. What steps have you already taken to bond front and rear batteries with the system, including all processors and head unit?

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: April 18, 2008 at 10:35 AM / IP Logged

IMO, any time anything in the system gets changed, gains should be re-set. This may sound like overkill is speakers are being swapped and the impedance loading is the same, but I generally don't trust what's printed on the box...

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inoitall

Member - Posts: 28

Joined: March 31, 2008

Posted: April 18, 2008 at 10:35 AM / IP Logged

Thanks for the reply. What i told my friend to do was use the test tone cd which is 60 hertz I think, have the volume where he listens to it at, have the gain all the way down and the sub output on the headunits all the way up, and then slowly turn the gain up untill the bass changes "tones". The gain was at alittle above half when the bass changed from good bass to choppy, nasty sounding bass. Then I told him to turn the gain back down a tad and leave it go.

With my grounding kit question, what do you mean by processor and headunit bond?

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: April 18, 2008 at 11:16 AM / IP Logged

What I mean is this: "Where are the amps, batteries, and additional components all grounded?"

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

inoitall

Member - Posts: 28

Joined: March 31, 2008

Posted: April 18, 2008 at 11:22 AM / IP Logged

Oh ok sorry. Ok each amp is grounded seperatly, yet grounded within 3 inches of eachother. They are grounded on the driver side of the trunk floor. The cap and battery are also grounded in that general location. DYohn, are you basically saying that a ported box has more of an output than a bandpass, thus giving me the reason to adjust the gain? I can understand doing this if going from a sealed to ported because youll need the gain higher for a sealed. I will tell him that when he changes them to the ported box, to simply re-due the gains.

aznboi3644

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Joined: May 01, 2006

Location: United States

Posted: April 18, 2008 at 2:53 PM / IP Logged

With the suboutputs on the HU all the way up you may very well be clipping the output signal from the HU...then if the amp is clipping than its clipping an already clipped signal which is even worse

DYohn

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Location: Arizona, United States

Posted: April 18, 2008 at 8:25 PM / IP Logged

inoitall wrote:

DYohn, are you basically saying that a ported box has more of an output than a bandpass, thus giving me the reason to adjust the gain?.

No, I'm not saying that at all. I'm saying that every speaker is different and if you want to be sure you have it right, you need to properly set the amplifier gain for the speakers you are using. 4-ohms is not always 4-ohms, and clipping can happen at completely different levels with different loading on the amp. It has nothing to do with the amount of output from the speaker system.

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inoitall

Member - Posts: 28

Joined: March 31, 2008

Posted: April 18, 2008 at 9:08 PM / IP Logged

id like to focus on the grounding kit area if thats ok. If my friend has questions to ask, then he can become a member. I just wanted to know if it is worth getting a grounding kit and use it for my amps, cap, and trunk battery? This would give each of those 2 grounding points instead of 1. Would this help my system (basically the equipment themselves) to perform better?

stevdart

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Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: April 18, 2008 at 10:13 PM / IP Logged

With most systems, there would be no performance enhancing whatsoever. It might just be a matter of convenience (in some cases) to use another grounding kit with the additional amp. For instance, if the former install has built-in or hard-to-get-at wiring components.

You just have to consider that the grounding wiring is a mirror image of the power wiring. If power starts at 2 ga and distributes 4 ga. to each amp, then each amp grounds out a 4 ga. to the ground block, which then supplies a 2 ga. ground to chassis. If there is no ground distro, ground each amp with either 4 ga. or 2 ga. to chassis (following the rule that the ground wire must be at least as large as the power wire).

Look at the install as it is now. If the distro block needs to be upgraded to supply more or larger gauge wiring, replace it. If there is no whine or hum (and therefore no ground loops) in the current system, stay with the same grounding point if possible, or within an inch or so from it on the same chassis panel. You don't want to spread the ground points around.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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