Hello guys. I know theres been a lot explained about clipping, but I have one more question. Could a HU's pre-amp output voltage lead to clipping of the subs? More specifically, if the voltage is low..such as in some ****tier HUs? I have a Sony CDX-M610 (the old motorized one, preamp: 2.1v ), which probably qualifies as ****ty. Or perhaps bad quality RCA cables? I'm also running the JBL 1200.1, and gain is properly set, but I don't feel the subs are getting loud enough before they start to clip. Thanks!
Replies (13)
swez on 03/23/2004 13:30:24
Clipping at the HU, will also pass down to the sub amp or other amps in the chain.
To minimize clipping of all amps in the chain, we need to know the voltage the HU can put out, (RCA out) is a "clean" signal signal where the internal preamps (HU) and amp inputs are not clipping either.
To minimize HU preamp clipping, we need to set our HU bass control (for subs) to a "0" boost/cut reference point. Then set the HU output volume to ~50-60% of max.
If the distortion in interior speakers is still present, back off on volume knob settings until clean (low distortion) is heard from interior speakers. Once that signal is clean and free of excess distortion, the amp gains can be set for sub amp.
The best way I know to do this w/o complex test equipment, is to open the doors, (Driver & Pass side) step back ~10 feet and listen to mid/highs. Once you get these loud, but low distortion, then adjust sub amp gain for maximum clean ouput and dial it back a tad to allow for bass tone adjustments (HU) as needed. Now, adjust your sub gain to obtain the loudest, but low distortion possible.
Use a CD you know well... as different CD's are mixed with varying degrees of bass, mids & highs. This is your reference point. Adjusting volume, tone and gain controls, will change with source of music. FM does not have the dynamic bandwidth of a CD. Different CD's are mixed in different ways. But... at least you have a reference point on the CD you know well.
With the 1200.1, you can have a huge amount of bass power at your finger tips. It will easily override your HU & full range speakers as well. If that is you goal... huge bass performance, but not balanced full range performance, there are other ways to tweak the bass. But the HU amps will distort long before the subs do, when gain is not set properly on the sub amp.
Say more about your RCA wiring, subs, enclosure and power/ground wiring lead to the 1200.1 amp. My guess, you are running out of current from the ALT/BAT and maybe BAT/GND feed line to this amp.
The JBL 1200.1 can pull >114A from the ALT/BAT part of your electricals. If the car electricals cannot support that current draw... amp will not meet full potential.
Say more please,
Swez
devastating12s on 03/23/2004 14:28:00
Well as for power wiring and such I'm using 4 guage ALL AROUND and double lines of 4ga on the bat/groundb
I do not seem to be running out of power at the batt or alt, my voltmeter reads 12.2~12v constant.
As for RCA wiring, I do not know much - they are standard RCA cables ...and I have put a female to 2 male adaptor on each for the JBL amp..
I'm using two JL 12w6v2s in a sealed enclosure to JL specs.. I've been debating whether or not to use the fiberglass filler someone suggested.... don't know why..since the box is already at Jl specs and dimensions...
The preamp on my Sony HU output is 2.1v
when you say: "To minimize HU preamp clipping, we need to set our HU bass control (for subs) to a "0" boost/cut reference point."
Does that mean put the HU bass control to the middle or to the very end. If I put it to the very end, this will totally turn off the subs. Do you mean to go one notch above the "turn off" point?
And yes swez, one of my main goals is to be able to draw as much bass as I can out of this setup. Should I change HU to one capable of 5v preamp output? Please give me your opinion. As always..thank you!br
ttocs on 03/23/2004 15:57:53
set all the eq/bass/treble to the normal setting(middle). You don't want to add or take away from the signal.
You can also try a line driver. PG makes a descent one for around $100 I think.
swez on 03/23/2004 18:16:25
As ttocs said, set bass and treble controls to "flat". No cut, no boost for your setup process.
Also, a line driver is very helpful to kick up low voltage HU RCA pre-outs. However, if you have a true 2.1 volts here, setting the amp gain at 2.0 or a tad under, should give you full potential from the amp.
Good on the power feed line and grounds here. Same w/ RCA's as noted. The only issue left is power getting to the amp. If you only have 12.0 volts at the amp, this amp is starving for more input watts. The full 1200 RMS is at 12.9 volts. You'd get even more output power if voltage was 13.5 or higher.
The math:
Assume current draw is fixed at 100 amperes and a 1 ohm load for subs. This amp is ~90% efficient (.90). Here are some rough guestimates of what you can expect:
12.0 volts x 100A = 1200 watts input x .90 = 1080 watts output
12.5 volts x 100A = 1250 watts input x .90 = 1125 watts output
13.0 volts x 100A = 1300 watts input x .90 = 1170 watts output
13.5 volts x 100A = 1350 watts input x .90 = 1215 watts output
Not exact, but you get the idea... as voltage goes up and current remains constant, wattage out will go up as well.
Finally, these subs are rated at 400 watts continous power each. Once X-max (full excursion) is reached, the subs will not get louder. Only stressing the mechanicals and voice coils at this point. Pending damage if you pass the yellow zone on ratings.
How do have these wired? (ohms load?) You get 2 (parallel) or 8 ohms (series) per sub. This nets a 1 or 4 ohm load to amp when each sub is wired to a terminal set on amp. If wired for 1 ohm, these puppies should slam your brains out!
Swez
devastating12s on 03/23/2004 19:44:22
I do have them in 2ohm mode and wired in parallel to net 1ohm.
yet..I dont feel they are as loud as they could be...
However, how do I boost up the voltage? I thought a standard car electrical system was 12volts...
also, how do I know when the amp gain is at 2.0volts?
and..any takers on the fiberglass filler question?
Thanks for all the help guys!
swez on 03/23/2004 20:44:07
The voltage is controlled by the ALT and the voltage regulator inside the ALT. When you start the car, the ALT first recharges the battery to full potential. The charging rate... current & voltage, are controlled by the voltage regulator, output rating of the ALT and often the Electronic Control Module computer. Most OEM ALT will charge at 13.5 volts or higher initially, then level out to the electrical load placed on the system.
Your vehicle may have a modest ALT with a rated output of 13.? volts and maybe 80-90 amperes at full output. To increase the power availalable to the sub amp, a larger CCA rated battery is always a good place to start. The stock BAT is probably 500 CCA or so. Increasing that to say... 850 CCA will help store more power (volts and amperes) to feed your entire electrical system. A larger feed wire (#4) between ALT output lug and + terminal on battery, will allow max current to flow.
If this still does not give the amp and electricals enough juice, a higher output ALT is in order. (150A will do... but not cheap)
As for gain settings on amp, this amp has a range from 4.0 volts (lowest sensitivity) to what... 250mV (1/4 volt) max. sensitivity. A 2.0 volt setting is midpoint of the gain control.
As for fiberglass in cabinate... I always use it. For a 12" sub, that's about 16 ounces of poly fill or 3.5" batting on sides, back, top and bottom of all panels. (interior of coarse) The fill slows the rear bass waves from the back of the cone and "fools the sub into thinking " it is in a slightly larger enclosure. It also blocks upper midbass resonances to minimize distortion.
Yeah, subs cannot think... but that's the layman's way of explaining this phenomena. Why give you a $20.00 answer that is hard to understand anyway??? GRIN
Got it?
Swez
ttocs on 03/23/2004 21:29:26
where did you have the gain set at? You might have mentioned it...
I have never looked at the numbers on the gain of the amp. Wouldn't really know if they are there or not after 7 yrs installing.. I have always used the way swez said to tune a system. The numbers may or may not be correct. Who cares what they say, it is your ears that matter.. This is part of the fun/annoyance of car audio, you will never quit tinkering/tuning/adjusting/replacing equipment once you pull the factory equipment out... And with that in mind the polyfill for the box is just a few bucks at the local hobby shop, pillow stuffing. Put it in, if you don't like it, take it out. Whatever you think is best....
devastating12s on 03/23/2004 22:56:13
ah I forgot to say I have my subs firing backwards towards the rear of the trunk.. and swez said polyfill "slows the rear bass waves from the back of the cone "... not entirely sure what that means but could that dampen the sound if the subs are positioned as stated?
swez on 03/24/2004 02:22:25
Yes, you did get it. Poly does dampen the bass waves that come off the back side of the cones. As a result of this damping, there is less bass energy redirected back to the cone and a very modest increase in low end output.
Facing the subs to the back of the vehicle (bumper) usually works best in most installs. Can try other orientations if you wish. But most like the bass best, cones facing the rear of the car.
Have you observed the cone movement of each sub when playing some heavy bass tracks? They should move in and out at the same time. Since this is a sealed enclosure, the cone movement should be very notable. If not, double check sub wiring to make sure all voice coils are proper polarity. It is very easy to mis-wire a DVC polarity wise. The result would be a severe loss in bass output.
Finally, in a trunk mounted system, bass can get trapped inside the trunk and not sound nearly as loud at the front seat. In Hatchback designs with fold down rear seats, much more bass passes into the interior of the car.
Swez
PS Have you had the SPL checked by a shop? With this amp and those subs, low 140's dB should be the norm. If the meter confirms that number... better get a hearing test as you may have lost some hearing from high SPL. Seriously....
devastating12s on 03/24/2004 12:34:34
ah hah! I may have found the culprit....
It seems that the wiring for speakers was 16 gauge speaker wire.. perhaps that inhibited some of the current flow. It seems the wires really heated up because there are some "melt marks" on the areas were the wires rested. I'm going to go to the shop and pick up some 8 or 10 gauge wiring for the speakers..
as for the polyfill... if the rear waves are blocked by polyfill, wouldn't I be inhibiting some of the waves that travel towards the cabin (since the subs are firing towards rear bumper)? Would these waves (in the absence of polyfill) make it past the box or would they just be bounced back?
and thank you swez for your concern over my hearing loss. However, I do believe it is quite fine..perhaps not as good as it used to be... but still acceptable =)
swez on 03/24/2004 14:35:04
Very good detective work... those small gage wires are not going to carry 600 watts to each sub very well. They will heat up, resistance of the wire will climb and decrease power to the subs. Go to #10 gage min here.
About fill, yes... the fill does absorb/slow air flow to a degree, the energy off the rear cone. This is a good thing as the rear bass waves, bouncing off the walls of the enclosure, reflects back to the cone and limits over excursion which often causes undue distortions.
When the bass waves are not dampened, the return wave pressure is often well out of phase with front cone waves. That would normally lead to cancellations (less bass wave energy output) if rear & front waves meet... out of phase. The enclosure contains that energy and limits phase cancellations outside the box.. The sealed box is a bass wave trap in all practicality. That's why the SQ is so good, but less SPL as opposed to ported or BP designs. We design sealed boxes NOT TO LEAK BASS ENERGY OUT OF THE BOX !!! Leakage means lost energy and lower SPL/SQ.
In a frequency plot curve... w/ fill, the low end bass has a bit less SPL and a small degree flatter roll off characteristics then a non-filled enclosure. Not much more than a few dB difference here. But the frequency roll of does lend to a smoother sounding sub system when poly fill is used. (Better SQ than non-filled enclosures) Less peaks in bass performance is good for high SQ applications. If you want high SPL, use a box that allows the peaks to work with cabin gain transfer function... Well designed Ported or BP boxes do this well.
Have a look here:
http://www.bcae1.com/spboxad1.htm
Near bottom of page talks about poly fill VS none used. Start reading here...
QUOTE:
Using Poly-fill:
Enclosure sizes:
Poly-fill can be used to make an enclosure seem slightly larger....
Swez
devastating12s on 03/24/2004 19:02:06
thansk swez..u always got the answers!
so yea I think we beat this topic pretty dead...
Thanks to everyone who helped! I'll post some pics of my new setup when done!
swez on 03/24/2004 19:45:28
Good luck... hope this all turns out better than planned.
Swez
PS Not always the best answers. That's why we use a team approach here.
Replies (13)
swez on 03/23/2004 13:30:24
Clipping at the HU, will also pass down to the sub amp or other amps in the chain.
To minimize clipping of all amps in the chain, we need to know the voltage the HU can put out, (RCA out) is a "clean" signal signal where the internal preamps (HU) and amp inputs are not clipping either.
To minimize HU preamp clipping, we need to set our HU bass control (for subs) to a "0" boost/cut reference point. Then set the HU output volume to ~50-60% of max.
If the distortion in interior speakers is still present, back off on volume knob settings until clean (low distortion) is heard from interior speakers. Once that signal is clean and free of excess distortion, the amp gains can be set for sub amp.
The best way I know to do this w/o complex test equipment, is to open the doors, (Driver & Pass side) step back ~10 feet and listen to mid/highs. Once you get these loud, but low distortion, then adjust sub amp gain for maximum clean ouput and dial it back a tad to allow for bass tone adjustments (HU) as needed. Now, adjust your sub gain to obtain the loudest, but low distortion possible.
Use a CD you know well... as different CD's are mixed with varying degrees of bass, mids & highs. This is your reference point. Adjusting volume, tone and gain controls, will change with source of music. FM does not have the dynamic bandwidth of a CD. Different CD's are mixed in different ways. But... at least you have a reference point on the CD you know well.
With the 1200.1, you can have a huge amount of bass power at your finger tips. It will easily override your HU & full range speakers as well. If that is you goal... huge bass performance, but not balanced full range performance, there are other ways to tweak the bass. But the HU amps will distort long before the subs do, when gain is not set properly on the sub amp.
Say more about your RCA wiring, subs, enclosure and power/ground wiring lead to the 1200.1 amp. My guess, you are running out of current from the ALT/BAT and maybe BAT/GND feed line to this amp.
The JBL 1200.1 can pull >114A from the ALT/BAT part of your electricals. If the car electricals cannot support that current draw... amp will not meet full potential.
Say more please,
Swez
devastating12s on 03/23/2004 14:28:00
Well as for power wiring and such I'm using 4 guage ALL AROUND and double lines of 4ga on the bat/groundb
I do not seem to be running out of power at the batt or alt, my voltmeter reads 12.2~12v constant.
As for RCA wiring, I do not know much - they are standard RCA cables ...and I have put a female to 2 male adaptor on each for the JBL amp..
I'm using two JL 12w6v2s in a sealed enclosure to JL specs.. I've been debating whether or not to use the fiberglass filler someone suggested.... don't know why..since the box is already at Jl specs and dimensions...
The preamp on my Sony HU output is 2.1v
when you say: "To minimize HU preamp clipping, we need to set our HU bass control (for subs) to a "0" boost/cut reference point."
Does that mean put the HU bass control to the middle or to the very end. If I put it to the very end, this will totally turn off the subs. Do you mean to go one notch above the "turn off" point?
And yes swez, one of my main goals is to be able to draw as much bass as I can out of this setup. Should I change HU to one capable of 5v preamp output? Please give me your opinion. As always..thank you!br
ttocs on 03/23/2004 15:57:53
set all the eq/bass/treble to the normal setting(middle). You don't want to add or take away from the signal.
You can also try a line driver. PG makes a descent one for around $100 I think.
swez on 03/23/2004 18:16:25
As ttocs said, set bass and treble controls to "flat". No cut, no boost for your setup process.
Also, a line driver is very helpful to kick up low voltage HU RCA pre-outs. However, if you have a true 2.1 volts here, setting the amp gain at 2.0 or a tad under, should give you full potential from the amp.
Good on the power feed line and grounds here. Same w/ RCA's as noted. The only issue left is power getting to the amp. If you only have 12.0 volts at the amp, this amp is starving for more input watts. The full 1200 RMS is at 12.9 volts. You'd get even more output power if voltage was 13.5 or higher.
The math:
Assume current draw is fixed at 100 amperes and a 1 ohm load for subs. This amp is ~90% efficient (.90). Here are some rough guestimates of what you can expect:
12.0 volts x 100A = 1200 watts input x .90 = 1080 watts output
12.5 volts x 100A = 1250 watts input x .90 = 1125 watts output
13.0 volts x 100A = 1300 watts input x .90 = 1170 watts output
13.5 volts x 100A = 1350 watts input x .90 = 1215 watts output
Not exact, but you get the idea... as voltage goes up and current remains constant, wattage out will go up as well.
Finally, these subs are rated at 400 watts continous power each. Once X-max (full excursion) is reached, the subs will not get louder. Only stressing the mechanicals and voice coils at this point. Pending damage if you pass the yellow zone on ratings.
How do have these wired? (ohms load?) You get 2 (parallel) or 8 ohms (series) per sub. This nets a 1 or 4 ohm load to amp when each sub is wired to a terminal set on amp. If wired for 1 ohm, these puppies should slam your brains out!
Swez
devastating12s on 03/23/2004 19:44:22
I do have them in 2ohm mode and wired in parallel to net 1ohm.
yet..I dont feel they are as loud as they could be...
However, how do I boost up the voltage? I thought a standard car electrical system was 12volts...
also, how do I know when the amp gain is at 2.0volts?
and..any takers on the fiberglass filler question?
Thanks for all the help guys!
swez on 03/23/2004 20:44:07
The voltage is controlled by the ALT and the voltage regulator inside the ALT. When you start the car, the ALT first recharges the battery to full potential. The charging rate... current & voltage, are controlled by the voltage regulator, output rating of the ALT and often the Electronic Control Module computer. Most OEM ALT will charge at 13.5 volts or higher initially, then level out to the electrical load placed on the system.
Your vehicle may have a modest ALT with a rated output of 13.? volts and maybe 80-90 amperes at full output. To increase the power availalable to the sub amp, a larger CCA rated battery is always a good place to start. The stock BAT is probably 500 CCA or so. Increasing that to say... 850 CCA will help store more power (volts and amperes) to feed your entire electrical system. A larger feed wire (#4) between ALT output lug and + terminal on battery, will allow max current to flow.
If this still does not give the amp and electricals enough juice, a higher output ALT is in order. (150A will do... but not cheap)
As for gain settings on amp, this amp has a range from 4.0 volts (lowest sensitivity) to what... 250mV (1/4 volt) max. sensitivity. A 2.0 volt setting is midpoint of the gain control.
As for fiberglass in cabinate... I always use it. For a 12" sub, that's about 16 ounces of poly fill or 3.5" batting on sides, back, top and bottom of all panels. (interior of coarse) The fill slows the rear bass waves from the back of the cone and "fools the sub into thinking " it is in a slightly larger enclosure. It also blocks upper midbass resonances to minimize distortion.
Yeah, subs cannot think... but that's the layman's way of explaining this phenomena. Why give you a $20.00 answer that is hard to understand anyway??? GRIN
Got it?
Swez
ttocs on 03/23/2004 21:29:26
where did you have the gain set at? You might have mentioned it...
I have never looked at the numbers on the gain of the amp. Wouldn't really know if they are there or not after 7 yrs installing.. I have always used the way swez said to tune a system. The numbers may or may not be correct. Who cares what they say, it is your ears that matter.. This is part of the fun/annoyance of car audio, you will never quit tinkering/tuning/adjusting/replacing equipment once you pull the factory equipment out... And with that in mind the polyfill for the box is just a few bucks at the local hobby shop, pillow stuffing. Put it in, if you don't like it, take it out. Whatever you think is best....
devastating12s on 03/23/2004 22:56:13
ah I forgot to say I have my subs firing backwards towards the rear of the trunk.. and swez said polyfill "slows the rear bass waves from the back of the cone "... not entirely sure what that means but could that dampen the sound if the subs are positioned as stated?
swez on 03/24/2004 02:22:25
Yes, you did get it. Poly does dampen the bass waves that come off the back side of the cones. As a result of this damping, there is less bass energy redirected back to the cone and a very modest increase in low end output.
Facing the subs to the back of the vehicle (bumper) usually works best in most installs. Can try other orientations if you wish. But most like the bass best, cones facing the rear of the car.
Have you observed the cone movement of each sub when playing some heavy bass tracks? They should move in and out at the same time. Since this is a sealed enclosure, the cone movement should be very notable. If not, double check sub wiring to make sure all voice coils are proper polarity. It is very easy to mis-wire a DVC polarity wise. The result would be a severe loss in bass output.
Finally, in a trunk mounted system, bass can get trapped inside the trunk and not sound nearly as loud at the front seat. In Hatchback designs with fold down rear seats, much more bass passes into the interior of the car.
Swez
PS Have you had the SPL checked by a shop? With this amp and those subs, low 140's dB should be the norm. If the meter confirms that number... better get a hearing test as you may have lost some hearing from high SPL. Seriously....
devastating12s on 03/24/2004 12:34:34
ah hah! I may have found the culprit....
It seems that the wiring for speakers was 16 gauge speaker wire.. perhaps that inhibited some of the current flow. It seems the wires really heated up because there are some "melt marks" on the areas were the wires rested. I'm going to go to the shop and pick up some 8 or 10 gauge wiring for the speakers..
as for the polyfill... if the rear waves are blocked by polyfill, wouldn't I be inhibiting some of the waves that travel towards the cabin (since the subs are firing towards rear bumper)? Would these waves (in the absence of polyfill) make it past the box or would they just be bounced back?
and thank you swez for your concern over my hearing loss. However, I do believe it is quite fine..perhaps not as good as it used to be... but still acceptable =)
swez on 03/24/2004 14:35:04
Very good detective work... those small gage wires are not going to carry 600 watts to each sub very well. They will heat up, resistance of the wire will climb and decrease power to the subs. Go to #10 gage min here.
About fill, yes... the fill does absorb/slow air flow to a degree, the energy off the rear cone. This is a good thing as the rear bass waves, bouncing off the walls of the enclosure, reflects back to the cone and limits over excursion which often causes undue distortions.
When the bass waves are not dampened, the return wave pressure is often well out of phase with front cone waves. That would normally lead to cancellations (less bass wave energy output) if rear & front waves meet... out of phase. The enclosure contains that energy and limits phase cancellations outside the box.. The sealed box is a bass wave trap in all practicality. That's why the SQ is so good, but less SPL as opposed to ported or BP designs. We design sealed boxes NOT TO LEAK BASS ENERGY OUT OF THE BOX !!! Leakage means lost energy and lower SPL/SQ.
In a frequency plot curve... w/ fill, the low end bass has a bit less SPL and a small degree flatter roll off characteristics then a non-filled enclosure. Not much more than a few dB difference here. But the frequency roll of does lend to a smoother sounding sub system when poly fill is used. (Better SQ than non-filled enclosures) Less peaks in bass performance is good for high SQ applications. If you want high SPL, use a box that allows the peaks to work with cabin gain transfer function... Well designed Ported or BP boxes do this well.
Have a look here:
http://www.bcae1.com/spboxad1.htm
Near bottom of page talks about poly fill VS none used. Start reading here...
QUOTE:
Using Poly-fill:
Enclosure sizes:
Poly-fill can be used to make an enclosure seem slightly larger....
Swez
devastating12s on 03/24/2004 19:02:06
thansk swez..u always got the answers!
so yea I think we beat this topic pretty dead...
Thanks to everyone who helped! I'll post some pics of my new setup when done!
swez on 03/24/2004 19:45:28
Good luck... hope this all turns out better than planned.
Swez
PS Not always the best answers. That's why we use a team approach here.
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