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how do i correctly tune my amp


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sethbuckner 
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Member spacespace
Joined: March 06, 2008
Location: Texas, United States
Posted: March 06, 2008 at 9:08 PM / IP Logged  

ok we'll i feel as if i've gotten the installation aspects of car stereo down.. and now i'm interested in the tuning aspects.. i would like to know how to correctly tune my memphis 1000.1D amp to my 2 Kicker Comp CVX 12"s in their currently sealed enclosure.. and also if i were to put them back into their origional bandpass enclosure.. i'm interested in the settings of teh filter, bass boost, Hz setting, etc..

any advice would be appreciated.

thanks, seth

sethbuckner 
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Member spacespace
Joined: March 06, 2008
Location: Texas, United States
Posted: March 06, 2008 at 9:27 PM / IP Logged  

also.. the specs to the subs are-

Impedance- Dual 2 ohm

RMS-750-(1500 peak)

Frequency response(Hz)-20-500

Db sensitivity(1w/1m)-87.1

just thought this would help one of you give me more accurate advice

sethbuckner 
Member - Posts: 22
Member spacespace
Joined: March 06, 2008
Location: Texas, United States
Posted: March 06, 2008 at 9:33 PM / IP Logged  

my subs are in the trunk of my small car-(protege) by the way.. i often fold one of my seats down in order to merge the cab and the trunk together.. more airspace?

stevdart 
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Posted: March 06, 2008 at 11:10 PM / IP Logged  

You don't actually "tune" an amplifier to match subs, although you may have heard it phrased like that.  The matching of sub to amp is sub's impedance vs. power output of the amp.  You should have each sub wired in series so that each sub is 4 ohms, then parallel the subs for a final 2 ohm impedance.  The amplifier will perform according to the 2 ohm impedance it is given.

You will use the low pass crossover and set it according to the ability of the front mid bass drivers.  If they are well installed 6.5's you should try a setting of about 80 Hz.  If they are smaller speakers you should try the setting a bit higher at 100 Hz.  Experimentation over a period of time is relevant here.  The front bass mids will have to pick up effortlessly where the sub is filtered, and the sub should be filtered at a low enough frequency that you can't localize the sound coming from it.

The amplifier is actually tuned to the deck (source).  That is where gain setting is all important and that is the first step that is successfully finished before tweaking the sound of the subs.  Search here.

Bass boost is for dummies.  No, that is not the name of a paperback self-help book you would find in your local bookstore.  If bass boost is used it is invariably because the user didn't choose the right gear for his expectations and is trying to put a bandaid on it.  If an SPL competitor uses the boost, that's another story and he will know what I am talking about anyway.  But leave it off and leave it alone.  It doesn't have to be used just because it's there.

Subsonic filter is used only if you are using a vented box, and that's your decision to make as well as determined by box tuning frequency and other considerations.  It isn't used for a sealed or bandpass box because its use wouldn't be needed.

Sealed boxes, when properly designed and constructed for the subs they house, will exhibit the best sound quality over the sub's frequency spectrum.  The lowest freqs will roll off smoothly and sound very natural, and very little peaking in the higher freqs.  There is no comparison with the sealed and the bandpass, as the latter shouldn't be in the hands of the daily user.  But there are thousands of guys who want loudness more than they want something to listen to, so they buy prefab bandpass boxes and go around thumping.  Burn your bandpass box or give it to someone you don't like. 

Ask the forum for insider knowledge on whether sealed or vented works best for this sub, but from what I've seen they can be used either way (note that bandpass isn't included).  Check your owner's manual for box sizes and construction.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
sethbuckner 
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Joined: March 06, 2008
Location: Texas, United States
Posted: March 07, 2008 at 4:12 PM / IP Logged  

i appreciate the advice... so i went out and followed the instructions  that the link in your reply withheld and also with your personal advice... my bass boost off, my subsonic filter off, my lpf is at about 50hz.. i turned my gain all the way down, and turned my music up rougly 75%-80% and then turned my gain up roughly 5/8 the way up.. i can honestly say it sounds very noticibly better... it could bang a little harder like before but the quality is definitely better..my subs are rated at 750 RMS each and my amp is pushing 1000 RMS-(1150 RMS said the birth sheet) at 1ohm.. but my impedance is at 2 ohms so my AMP is delivering about 650 RMS if gain is turned all the way up.. which it is not... could this cause underpowering and clipping issues? can 100 RMS less than the speaker's rating cause potentially serious problems?

any mor advice?

stevdart 
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Posted: March 07, 2008 at 5:00 PM / IP Logged  

seth wrote:
so my AMP is delivering about 650 RMS if gain is turned all the way up.

This part is incorrect.  The amplifier delivers full power when you have the gain set to match the deck's output.  The position of the arrow line on the dial (e.g. "5/8 the way up") means nothing at all.  If you have the gain correctly set so that when you turn the deck volume up to the maximum 3/4 level (this is where you MAY denote dial position), the amplifier will perform with the full power it was built to provide.

Often it is those clipped levels that seem to make everything louder.  When the music is deteriorated and the speaker is suffering because of the squared wave signal, the sound is harder to listen to.  That alone makes it sound louder.  But it does also increase power to clip the signal, although to ill effect.  It is not a bad idea to work again at setting the gain sometime again when you have absorbed more knowledge.  You should never again refer to gain "position" but should, if you are confident in the process you used, simply state that "the gain has been correctly set...by me".

Your low pass filter is set very low if it is at 50 Hz.  That means  that the fronts will still have to perform down to levels beyond their abilities.  The crossover doesn't just cut the sound at the specified freq but actually slopes it down at around that point.   That's why I said that a set of good components can pick up from the sub with filters set to 80 Hz.  Keep that in mind as you to continue to work on your system and in particular the front soundstage.

Underpowering can never hurt a speaker.  Much of what you listen to is powered with one or two watts.  It is only when the user tunes his gear improperly with the belief that he is getting more power (turning the amp gain past its correct setting or turning deck volume up into its distortion area) that severe clipping can occur, and damage to the speaker is the result.  You can run your sub all day with one watt or anything up to its full continuous rating of 750 watts, as long as the signal is clean.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
sethbuckner 
Member - Posts: 22
Member spacespace
Joined: March 06, 2008
Location: Texas, United States
Posted: March 07, 2008 at 5:44 PM / IP Logged  
stevdart wrote:

seth wrote:
so my AMP is delivering about 650 RMS if gain is turned all the way up.

Your low pass filter is set very low if it is at 50 Hz.  That means  that the fronts will still have to perform down to levels beyond their abilities.  The crossover doesn't just cut the sound at the specified freq but actually slopes it down at around that point.   That's why I said that a set of good components can pick up from the sub with filters set to 80 Hz.  Keep that in mind as you to continue to work on your system and in particular the front soundstage.

ok well my deck also has both Hpf's and Lpf's... and both my front and back speakers and tweeters have inline (3-way) crossovers as well.. what do you recommend that i set my High and Low pass filters on my deck to?i beleieve there are about 5 presets of OFF, 50Hz, 63Hz, 80Hz, 100Hz.... and there is also a Sub Hz setting.. anywhere from 50Hz to i believe 110Hz.....i was under the assumption that the Sub Hz setting determined what went through the RCA's and to my amp? and i don't exactly  understand how my Hz setting on my amp for my sub influences and affects my component speakers which are not connected to that amp... can you explain?

stevdart 
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Posted: March 08, 2008 at 2:29 AM / IP Logged  

The low pass filter setting on the sub amp doesn't directly affect the front speakers.  But unless you want a large hole in this very important part of the freq range you will have to compensate with the setting for the fronts to fill that gap.  So, if the sub is set to be filtered at 50 Hz lowpass, the next speaker in line has to be set at 50 Hz highpass to keep up.  That's the problem.  Your sub setiing should be in the range of 80 to 100 Hz and if that is where you set the sub lowpass at, the same setting for highpass should be used for the fronts.

You don't want to employ double crossovers (deck and amp) at around the same frequency.  Send a full range signal to an amplifier if you are going to use the filter on the amp.  If you are using the sub out jacks on the deck, use the highest lowpass setting it will allow or use "off" if that is available, then set the filter at the amp.  Conversely, if the crossover on the deck is superior to that which the amp provides, set the filter off at the amp and use the deck to set the crossover point.

Your main speakers have passive crossovers so you only have to provide one highpass setting for them.  It is the point where they blend sound with the sub, say at 80 Hz.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
sethbuckner 
Member - Posts: 22
Member spacespace
Joined: March 06, 2008
Location: Texas, United States
Posted: March 09, 2008 at 1:13 AM / IP Logged  
i greatly appreciate your advice.. my system without a doubt sounds better and now just as strong..this is one bad*** forum..  many forums have idiots that act as if they now accurate reccomendations and advise. but it has been prooven that this site actually does.. thanks, seth

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