)
Thank you. I understand the purpose of a capacitor much better now but I feel as if it is not going to make that much difference.
I'm wondering whether a big 2 farad capacitor could compensate for a thinner wire such as 4 or even 8 guage. From reading that article it sounds like this is not the case.
I've talked to a lot of people who purchased capacitors and virtually all were dissapointed because they could hear no difference. I've never seen an installation where the capacitor made a difference. Richard Clark did a thorough, controlled test that showed that a capacitor actually reduced the alternator's ability to recover after a large drain. There was absolutely no benefit to having the capacitor.
If a capacitor actually did something for an audio system playing music, manufacturers would demo a system with an A/B comparison. To my knowledge, none have.
The only time that a capacitor 'may' be of use is in a competition system where all you need is a 'burp'.
Instead of spending money on a capacitor, people should spend their money on a new alternator.
If a capacitor actually did something for an audio system playing music, manufacturers would demo a system with an A/B comparison. To my knowledge, none have.
The only time that a capacitor 'may' be of use is in a competition system where all you need is a 'burp'.
Instead of spending money on a capacitor, people should spend their money on a new alternator.
Perry Babin said:
I partially agree. The most significant benefit I have seen a capacitor provide is to reduce the headlights dimming every time the bass hits. Keep in mind that an alternator is a rotating machine that relies on magnetic induction to produce its output; there is an inherent time delay in all alternators, even the high performance ones. The capacitor is intended to support the instantaneous pulse until the alternator has time to catch up. In addition, having the power source 10 feet or more from the load is always a bad design tradeoff that is not easily resolved in a car. Multiple batteries is just as unfortunate of a tradeoff.
Adding the capacitor is essentially a band aid, IMO. Fundamentally, the amplifier runs out of joules internally, and requires excessive current input to recharge them. The capacitors on the +/- regulated rails are undersized (all too common nowadays). The manufacturer relies on the speed of the switching power supply to recharge the rails when necessary. In theory, this will work fine; however, in a 12V system, the current requirements are too fast and too high. Hence the 'band aid' is to add extra capacitance at the input of the SMPS. The correct approach is to build a real amplifier; one that has adequate internal capacity to drive the load.
This is all exacerbated with the advent of electronic music, where bass notes are no longer from a kick drum, but a computer, where the notes are not only loud but long.
I agree on zigzagflux's comment.
indeed a cap is just a band aid but it may be enough rather than spending hundreds on a HO alt.
valterdaw,
as I said in my first comment, I wouldn't say it was useless so I think it is money well spent. in local currency, my two caps cost me less than php3000. a brand new 150A HO alternator would set me back ten times the cost, other brands would cost even more.
I rarely listen at high volumes. I only play loud at about 10% of the time when I feel like it or such. so in my case, a HO alt costs too much. the stock alternator does fine recharging the batt during the 90% of the time that I'm not cranking it up to max.
going back to the caps, I originally installed it to reduce headlight dimming. now that I'm using HID, headlight dimming is not a problem anymore but the caps do keep my amp from tripping its low voltage protection. (it does have 10000+uF rail caps at the SMPS outputs, 41Hz amp8) the voltage for the other in car electronics is more stable and fluctuates less. as for sound, percussive bass hits harder.
I would also disagree on caps helping on SPL systems more than everyday music systems. they may help on everyday systems since the peaks last lest than a sec when the amp is driven just under clipping. SPL contests drive the amps into full clipping at about 3-5secs which is just too long for a cap to provide enough current that's why competitors use more alternators and a lot of batteries for that.
indeed a cap is just a band aid but it may be enough rather than spending hundreds on a HO alt.
valterdaw,
as I said in my first comment, I wouldn't say it was useless so I think it is money well spent. in local currency, my two caps cost me less than php3000. a brand new 150A HO alternator would set me back ten times the cost, other brands would cost even more.
I rarely listen at high volumes. I only play loud at about 10% of the time when I feel like it or such. so in my case, a HO alt costs too much. the stock alternator does fine recharging the batt during the 90% of the time that I'm not cranking it up to max.
going back to the caps, I originally installed it to reduce headlight dimming. now that I'm using HID, headlight dimming is not a problem anymore but the caps do keep my amp from tripping its low voltage protection. (it does have 10000+uF rail caps at the SMPS outputs, 41Hz amp8) the voltage for the other in car electronics is more stable and fluctuates less. as for sound, percussive bass hits harder.
I would also disagree on caps helping on SPL systems more than everyday music systems. they may help on everyday systems since the peaks last lest than a sec when the amp is driven just under clipping. SPL contests drive the amps into full clipping at about 3-5secs which is just too long for a cap to provide enough current that's why competitors use more alternators and a lot of batteries for that.
Let me start this post with ---
I certainly don't want to argue.... With anyone.
"If a capacitor actually did something for an audio system playing music, manufacturers would demo a system with an A/B comparison. To my knowledge, none have. "
15 yrs ago we were putting caps on "legs" of multi fuse holders so we could remove the fuse at the battery and to the cap to "safely" work on the amps in the car. More than once we would "forget" to put the cap fuse back in and we all knew instantly. We would shut down the car, check the voltage on the cap, re-charge through the resistor if required (never really was since the cap only sat idle for 30 minutes or so) then drop in the fuse. Presto, better bass, and somehow "cleaner" highs again.
There is no better a/b comparison than cap in circuit, cap out of circuit in YOUR vehicle over a period of time.
This is DIYAudio... Try for yourself. I won't be upset if you don't agree. Everyone and every system is different. In the end it's all about what YOU like.
I certainly don't want to argue.... With anyone.
"If a capacitor actually did something for an audio system playing music, manufacturers would demo a system with an A/B comparison. To my knowledge, none have. "
15 yrs ago we were putting caps on "legs" of multi fuse holders so we could remove the fuse at the battery and to the cap to "safely" work on the amps in the car. More than once we would "forget" to put the cap fuse back in and we all knew instantly. We would shut down the car, check the voltage on the cap, re-charge through the resistor if required (never really was since the cap only sat idle for 30 minutes or so) then drop in the fuse. Presto, better bass, and somehow "cleaner" highs again.
There is no better a/b comparison than cap in circuit, cap out of circuit in YOUR vehicle over a period of time.
This is DIYAudio... Try for yourself. I won't be upset if you don't agree. Everyone and every system is different. In the end it's all about what YOU like.
troystg said:
as for the comments that say caps don't help much or are useless, I can't blame you guys. today, there are so much cheap knock off caps that I made a capacitance meter for measuring these really huge capacitances. and guess what, I measured most (if not all) cheap brands are below spec at 0.85F rather than 1F, some are less. and that is not limited to cheap ones. even some expensive ones aren't immune to this.
FWIW, I studied the amplifier output voltage across my subs with an oscilliscope using a test tone CD and other source material.
I found that high power output in the bass region caused a sagging waveform after signal peak. Similar to a soft clip of the waveform, this observation was determined to be caused by insufficient supply current to the amp.
Solution 1 - Larger guage supply cable
Solution 2 - Large Capacitor at Amp
My Solution - Second battery in trunk
I found it easier to add a battery, but I suppose the Farad cap would have solved the issue as well
- Rob
I found that high power output in the bass region caused a sagging waveform after signal peak. Similar to a soft clip of the waveform, this observation was determined to be caused by insufficient supply current to the amp.
Solution 1 - Larger guage supply cable
Solution 2 - Large Capacitor at Amp
My Solution - Second battery in trunk
I found it easier to add a battery, but I suppose the Farad cap would have solved the issue as well
- Rob
rob3262 said:
Those are some good tests you made, and prove the issue came down to power supply joules.
Not that I need to be right, but I think it's important that we all realize these solutions are still band aids. The root cause is insufficient capacitance post-powersupply. Being that adding more capacitance internally is difficult, we pursue other avenues to help out a poor design.
My a/d/s amps suffer from this same problem. Cheap cheap.
Zigzagflux, it sounds like you need a higher power amplifier and/or one with a stiffly regulated power supply. The internal caps are recharged ~50,000 times a second. More secondary power supply capacitance will do very little. Even if you added more capacitance on the secondary, it would only help at the onset of clipping. If you're driving your amp to clipping on a regular basis, you need an amp with more rail voltage.
As with all discussions, there's likely a bit of truth from all sides. There's no way to nail down all of the many variables. Even if we did, changing only one variable would re-open this can of worms.
As with all discussions, there's likely a bit of truth from all sides. There's no way to nail down all of the many variables. Even if we did, changing only one variable would re-open this can of worms.
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