couple quick questions regarding Alpine CDA-7894 & more
03-20-2003, 06:38 AM
#1
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i recently installed everything this weekend past... and have noticed two things about this deck that i just hope to verify...
1st: when listening to the deck, at what volume level (ie, displayed number) are yall first hearing distortion in the pre-amp signal? i am using my Adcom amp and regardless of the gain setting, i'm finding that i start to hear what i'm figuring is pre-amp signal distortion at around the 24 - 25 figure. does that sound about right? it matches the general 2/3 rule of thumb, but i'd like verification. i have my internal amp disabled.
2nd: i installed all my wiring and such for my sub and amp, but haven't purchased my actual sub as yet. to test the wiring and whatall, i borrowed a sub and box from a friend, wired up the amp, and fired up the system. everything was good regarding noise, except the sub didn't seem to oomph as much as it did in my previous install. i'm using a Kicker ZR-240 for the sub amp.
the speaker i used for my test is more efficient than my previous sub, and presents the same load (4ohms). i used to have to dial the gain way back to keep the volume in check (around 10 o'clock), and this time it seemed that even after properly setting the gain for distortion (gain ended up at around 3 o'clock), volume levels were way low. this is also compared to the volume levels of my friend's setup, which uses a Punch 160 to drive the sub.
due to circumstances, i only had use of the sub for about 30 minutes, so i didn't have time to do any excessive troubleshooting, but i checked and as far as i can tell, i'm getting good signal through both RCA leads, the amp is functioning properly, and i had the subwoofer output on, the lpf set for 120hz, and the headunit sub level at around +10 to + 15.
i'm going to try to borrow my old sub from the friend i sold it to and run some more checks soon to keep variables down to a minimum.
is there anything that i might be missing about the headunit and it's subwoofer output signal?
any suggestions/information/experiences would be appreciated. my primary concern is to verify the pre-amp distortion... the sub issue i'll probably figure out anyway given enough time to work on it...
does the S have any limitations on the amount of power can provide to amps?
1st: when listening to the deck, at what volume level (ie, displayed number) are yall first hearing distortion in the pre-amp signal? i am using my Adcom amp and regardless of the gain setting, i'm finding that i start to hear what i'm figuring is pre-amp signal distortion at around the 24 - 25 figure. does that sound about right? it matches the general 2/3 rule of thumb, but i'd like verification. i have my internal amp disabled.
2nd: i installed all my wiring and such for my sub and amp, but haven't purchased my actual sub as yet. to test the wiring and whatall, i borrowed a sub and box from a friend, wired up the amp, and fired up the system. everything was good regarding noise, except the sub didn't seem to oomph as much as it did in my previous install. i'm using a Kicker ZR-240 for the sub amp.
the speaker i used for my test is more efficient than my previous sub, and presents the same load (4ohms). i used to have to dial the gain way back to keep the volume in check (around 10 o'clock), and this time it seemed that even after properly setting the gain for distortion (gain ended up at around 3 o'clock), volume levels were way low. this is also compared to the volume levels of my friend's setup, which uses a Punch 160 to drive the sub.
due to circumstances, i only had use of the sub for about 30 minutes, so i didn't have time to do any excessive troubleshooting, but i checked and as far as i can tell, i'm getting good signal through both RCA leads, the amp is functioning properly, and i had the subwoofer output on, the lpf set for 120hz, and the headunit sub level at around +10 to + 15.
i'm going to try to borrow my old sub from the friend i sold it to and run some more checks soon to keep variables down to a minimum.
is there anything that i might be missing about the headunit and it's subwoofer output signal?
any suggestions/information/experiences would be appreciated. my primary concern is to verify the pre-amp distortion... the sub issue i'll probably figure out anyway given enough time to work on it...
does the S have any limitations on the amount of power can provide to amps?
03-21-2003, 07:45 PM
#2
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hey i was looking through the manual and it looks like you can adjust the phase for the sub channel (though the instructions aren't clear on how to set phase...) maybe that was the issue?
03-22-2003, 04:49 AM
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Was your other car a convertible? If not do, do not expect the same SPL with this car. A roof really helps keep the sound concentrated inside the car.
The alternator will be the limiting factor in how much current you can provide to any system.
The alternator will be the limiting factor in how much current you can provide to any system.
03-22-2003, 06:48 AM
#4
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Originally posted by mgiang7
hey i was looking through the manual and it looks like you can adjust the phase for the sub channel (though the instructions aren't clear on how to set phase...) maybe that was the issue?
hey i was looking through the manual and it looks like you can adjust the phase for the sub channel (though the instructions aren't clear on how to set phase...) maybe that was the issue?
[QUOTE]Originally posted by matrix
[B]Was your other car a convertible?
03-26-2003, 07:18 PM
#6
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Thread Starter
update and resolution:
still no clue as to #1 - i'm accepting that this is the point where pre-amp distortion begins.
re #2:
it appears that Alpine has misleadingly labeled the subwoofer level in the headunit. it is labeled as a 0 to +15 level. this is incorrect, as the control actually adjusts the subwoofer out from -15db to 0db. this can be verified on Alpine's website in their tech section under product feature and specification sheets.
direct link for the CDA-7894, for those who have signed up with Alpine to access the information.
[QUOTE]
Bass Engine
still no clue as to #1 - i'm accepting that this is the point where pre-amp distortion begins.
re #2:
it appears that Alpine has misleadingly labeled the subwoofer level in the headunit. it is labeled as a 0 to +15 level. this is incorrect, as the control actually adjusts the subwoofer out from -15db to 0db. this can be verified on Alpine's website in their tech section under product feature and specification sheets.
direct link for the CDA-7894, for those who have signed up with Alpine to access the information.
[QUOTE]
Bass Engine
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03-27-2003, 09:02 AM
#8
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ahh... but they are not the same...
the 0db is the reference source input... that is the input level where the signal is un-altered from the source material. however, the way Alpine has it labeled, it implies that the -15db (which shows as +0 on our heads) is the reference for the source material.
however, you are correct that either way you do still retain 15 db of adjustment...
the 0db is the reference source input... that is the input level where the signal is un-altered from the source material. however, the way Alpine has it labeled, it implies that the -15db (which shows as +0 on our heads) is the reference for the source material.
however, you are correct that either way you do still retain 15 db of adjustment...
03-27-2003, 04:25 PM
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Okay what level is a reference source input? A reference point is usually indicated via a unit of measure, for example...dBm = 1 milliwatt, dBW = 1 watt. A value expressed in dB only indicates an increase or decrease of X amount but no reference is given. So unless you know what the reference point value is -15dB->0dB is the same as 0dB ->15dB...it is a change of 15 dB.
03-27-2003, 07:46 PM
#10
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sigh.
i ask you, is there a need to compare it to some unit of measurement? i didn't take any readings w/ a meter or a scope, so i have no measured voltage, power, or current baseline as a reference point.
however, i do have an output level for the front and rear channels with which to compare the sub level. the sub levels were clearly far below the front and rear channel output levels. especially when i considered my previous experience with the same amplifier and identical source material (ie - CD).
thus, i do have a reference point with which to compare. with both crossovers turned off, if i switch between my sub and front RCAs, i should get the same (or very close to the same) volume level from my speakers if the amplifier gain isn't adjusted. when i made this comparison, it was clear that the sub output was far below the fronts. thus, the front RCA's are my baseline and reference point. a baseline and relative change doesn't have to be a measured quantity if a proportional consideration is being made... an absolute reference point or unit is unnecessary.
so, to restate what i said previously - there is a big difference between a -15 to 0 (db or whatever units Alpine chooses to use) adjustment (which is the actual adjustment made) and a 0 to +15 adjustment (which is Alpine's implied adjustment).
i don't know what the actual voltage or current reduction that a 15db (according to Alpine's ambiguous instructions) change reflects, but at the same time i don't need to know the voltage reduction.
and finally, since i was thinking in terms of input into the amp vs output from the headunit, i called it a reference source input. i probably should have been clearer - but since i WAS answering my own question in the slight chance that someone else might have a similar problem and drag this post up in a search, i wasn't taking a long amount of time to formulate a detailed post.
i ask you, is there a need to compare it to some unit of measurement? i didn't take any readings w/ a meter or a scope, so i have no measured voltage, power, or current baseline as a reference point.
however, i do have an output level for the front and rear channels with which to compare the sub level. the sub levels were clearly far below the front and rear channel output levels. especially when i considered my previous experience with the same amplifier and identical source material (ie - CD).
thus, i do have a reference point with which to compare. with both crossovers turned off, if i switch between my sub and front RCAs, i should get the same (or very close to the same) volume level from my speakers if the amplifier gain isn't adjusted. when i made this comparison, it was clear that the sub output was far below the fronts. thus, the front RCA's are my baseline and reference point. a baseline and relative change doesn't have to be a measured quantity if a proportional consideration is being made... an absolute reference point or unit is unnecessary.
so, to restate what i said previously - there is a big difference between a -15 to 0 (db or whatever units Alpine chooses to use) adjustment (which is the actual adjustment made) and a 0 to +15 adjustment (which is Alpine's implied adjustment).
i don't know what the actual voltage or current reduction that a 15db (according to Alpine's ambiguous instructions) change reflects, but at the same time i don't need to know the voltage reduction.
and finally, since i was thinking in terms of input into the amp vs output from the headunit, i called it a reference source input. i probably should have been clearer - but since i WAS answering my own question in the slight chance that someone else might have a similar problem and drag this post up in a search, i wasn't taking a long amount of time to formulate a detailed post.