posted
I thought you just put a multimeter on the output side of the amp along with the clamp??
-------------------- The debate between Christians and athiest's has never been an intelectual one, but a moral one. When presented with evidence that they have no answer for they just sling mud and call us stupid! Posts: 694 | From: Michigan | Registered: Jul 2008
| IP: Logged |
posted
almost splferrell. it's voltage divided by amperage Ohm's Law states that E=I*R R is Resistance(Ohms) E is Voltage(Volts) I is Amperage(Amperes) P is Power(Watts)
R=E/I R=E^2/P R=P/I^2
Ok David. Measure you nominal resistance with power off. Now put the clamp on the + output wires from the amp to the speaker. Put the voltometer on the + and - outputs of the amp. Power everything thing up. BURP!!!! Quickly write down the voltage and amperage. If you have a termlab, THEN write down the SPL. Calculate power by multiplying Volts*Amps. Then divide Volts by Amps for reactive impedance. Subtract the nominal impedance, and you have your impedance rise for that frequency, power, and enclosure. Change one of those factors, and the rise and final impedances will change. Every few burps, get another nominal impedance measurement, since hot coils may read different
If you have a second clamp and voltometer, you can measure amplifier efficiency at the same time.
Posts: 5494 | From: Columbus, OH - formerly FL | Registered: Oct 2003
| IP: Logged |
posted
an example...on 10kW of power, you may find that you get 155.0dB on 10,540W at 58Hz. You might find that at 55Hz, you get 154.8dB on only 8kW. 20%less power should make more than a 0.2dB loss. Obviously, your output design is more efficient 3Hz lower. Find a way to bring down the note without major volume and port change, and try again. If done right, you're peak spl should be at a lower freq, but your power demands lower. Meaning the system is more efficient. If measuring amp power input as well, you can find the point where lowering coil impedance for more power, versus amplifier efficiency reaches a neutral point. at some point of lower impedance, the amp will start sacrificing efficiency quickly. Not actual measurements, but a low impedance survivor... an Ia20.1 may do 900@2ohm, 1800@1ohm. half impedance, double power. half that impedance, maybe only 30% more power. half impedance again, maybe only 16% more power. Run the amp at 0.17ohms, maybe only 3100W. Now you're at 1/6 the impedance, but only 70% more power. drop the impedance by half one more time, and only gain 4% power. no longer is the efficiency loss worth the 6 extra batteries.
Posts: 5494 | From: Columbus, OH - formerly FL | Registered: Oct 2003
| IP: Logged |
posted
But whatever your reactive load is, is the load that your amplifier sees and puts out power at. For example if you have a .25 ohm nominal load and when you calculate your rise you have a 1.08 ohms reactive load, the 1.08 ohms is what load your amp is seeing and putting out power at.
-------------------- TEAM SUNDOWN AUDIO 2009 NSPL Car 1801-3600 Watt Record Holder: 151.2db 2009 NSPL Car 3601-Up Watt Record Holder: 152.6db 2009 NSPL Car Hardcore Record Holder: 155.2db 2009 NSPL Car 3601-UP, Car Hardcore, and Car Points World Champion Posts: 1847 | From: The Triad | Registered: Jan 2008
| IP: Logged |
quote:Originally posted by D-Bass: an example...on 10kW of power, you may find that you get 155.0dB on 10,540W at 58Hz. You might find that at 55Hz, you get 154.8dB on only 8kW. 20%less power should make more than a 0.2dB loss. Obviously, your output design is more efficient 3Hz lower. Find a way to bring down the note without major volume and port change, and try again. If done right, you're peak spl should be at a lower freq, but your power demands lower. Meaning the system is more efficient. If measuring amp power input as well, you can find the point where lowering coil impedance for more power, versus amplifier efficiency reaches a neutral point. at some point of lower impedance, the amp will start sacrificing efficiency quickly. Not actual measurements, but a low impedance survivor... an Ia20.1 may do 900@2ohm, 1800@1ohm. half impedance, double power. half that impedance, maybe only 30% more power. half impedance again, maybe only 16% more power. Run the amp at 0.17ohms, maybe only 3100W. Now you're at 1/6 the impedance, but only 70% more power. drop the impedance by half one more time, and only gain 4% power. no longer is the efficiency loss worth the 6 extra batteries.
Written very well Donald.
-------------------- "TECMO BOWL CHAMPION" Posts: 1353 | From: The Recession | Registered: Dec 2007
| IP: Logged |
posted
Wow what information here ,good job donald ,I tested mine and i am running at .5 ohms to each amps getting 98.6 volts x 46.2 amps and imp rise of 2.1 -.5=1.6 the amp sees .I wonder does that sound about right ?
98.6x46.2=4555.32 watts 98.6 div 46.2=2.1 voltage drops from 17.6 to 14.2 on 3 second burps i only use 7 batts turbostarts on 2 xxx 6500's
someone correct me if i am wrong on the figures
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL TEAM POWERMASTER TEAM SOUNDSTREAM Posts: 2678 | From: Everywhere | Registered: Oct 2004
| IP: Logged |
quote:Originally posted by TeamSubGoPoof: Close Ron, you don't subtract the original impedence.
Your amps see 2.1 during a burp which is around a 4x impedence rise.
I bet you're running a pretty small enclosure?
17 cudes after displacement of port and subs . all for 4 15's
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL TEAM POWERMASTER TEAM SOUNDSTREAM Posts: 2678 | From: Everywhere | Registered: Oct 2004
| IP: Logged |
quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence? and what are somethings u can do to get your impedence rise lower?
I am wondering the same .
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL TEAM POWERMASTER TEAM SOUNDSTREAM Posts: 2678 | From: Everywhere | Registered: Oct 2004
| IP: Logged |
quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence? and what are somethings u can do to get your impedence rise lower?
I am wondering the same .
The bigger the box the less impedence rise is what I've always been told. Make the box bigger. Most serious drag cars have huge enclosure's for even 2 18's. I've seen 2 18's in 40 cubes before so if the bigger the box the less rise then that particular box must not have had a whole lot of rise to it.
-------------------- TEAM SUNDOWN AUDIO 2009 NSPL Car 1801-3600 Watt Record Holder: 151.2db 2009 NSPL Car 3601-Up Watt Record Holder: 152.6db 2009 NSPL Car Hardcore Record Holder: 155.2db 2009 NSPL Car 3601-UP, Car Hardcore, and Car Points World Champion Posts: 1847 | From: The Triad | Registered: Jan 2008
| IP: Logged |
But when you get too big the box wants to peak lower which hurts SPL.
In a normal ported box when you get it tuned in perfectly and you play around tuning it also decreases impedence rise because the woofers aren't moving as much
Impedence rise is a bitch lol, also any flexing in the enclosure will incrase impedence rise
--------------------
Posts: 8169 | From: Russellville AL | Registered: Nov 2002
| IP: Logged |
quote:Originally posted by TeamSubGoPoof: That is true Zach
But when you get too big the box wants to peak lower which hurts SPL.
In a normal ported box when you get it tuned in perfectly and you play around tuning it also decreases impedence rise because the woofers aren't moving as much
Impedence rise is a bitch lol, also any flexing in the enclosure will incrase impedence rise
Do you think you could help me in my case Justin? I'll give you a little info so you know what I'm dealing with. Currently my amp is a Crunch GP3000D. When I burp it at 51hz for power tests I get 88.4 volts and 22.8 amps. You can see that I'm only making 2000 watts roughly. And my impedence is a nominal 1.2, and rises to 3.88 ohms when it's burped so probably less on music. Right now I'm getting rid of the 3000D and doing two Sundown SAZ 1500D's wired one per sub at .5 ohms each. This will help to split the rise between two amps and give them more power, but what else could you reccomend that I do to help drop the rise.
Here are the box specs: Total volume after all displacement is 4.12cuft for 2 Nightshade 12's 4 4" aero's the stock length they come tuning the box to 40hz The woofers are firing up and the ports back in a Focus ZX3
I know by splitting up the load between two amps with a lower nominal load is going to help, but is there anything else you can think of that may help me get less rise? I've been told that by switching to 2 6" aeros over the 4 4" ones will help with the rise some and still keep the tuning the same with only 4 more sqin of port. I need some help with this, but it is really a daily listening box that I use for bassrace. I still am trying to get a better number out of it for my own personal best.
Oh yeah my best number to date in the car is a 148.6, but since moving to North Carolina the number has dropped off to a 147.5 at highest. I did upgrade the recones on the woofers when they were done to harder spiders and a longer coil so I may have lost efficiency since the woofer is now harder to move with the suspension harder. I was doing consistant 148.1's and still dropping to a 147.5 after moving seems like a lot of loss. Is it possible to lose that much just by changing location? My frequency also went up from 48 hz to 51 or 52 hz after I got to NC too.
-------------------- TEAM SUNDOWN AUDIO 2009 NSPL Car 1801-3600 Watt Record Holder: 151.2db 2009 NSPL Car 3601-Up Watt Record Holder: 152.6db 2009 NSPL Car Hardcore Record Holder: 155.2db 2009 NSPL Car 3601-UP, Car Hardcore, and Car Points World Champion Posts: 1847 | From: The Triad | Registered: Jan 2008
| IP: Logged |
quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence?
Ok.......let me break it down a little better.He's right you don't subtract the nominal impedance.I think you misunderstood the original post.Ex...nominal impedance is .25,and your measurements caculate to 2.5 ohms.Your amp is seeing 2.5 ohms,so your rise is 2.25.You are only subtracting to see your actual impedance rise,not what impedance your amps are seeing.Hope that clears things up.
-------------------- MR. SEARS (LOUD) LIL WHITE CAVY TEAM HIGH X-CURSION STEVE(TEAM CAPTAIN) TEAM DD 2009 SS-NW AND STREET C(THEY'RE HERE) 2008 TRUNK MODIFIED WORLD RECORD HOLDER (153)12v certified legal TL 2008 2007 PRO TRUNK WORLD FINALS (150.9<150.2)12v 2006 PRO TRUNK 1x WORLD RECORD HOLDER(151.2)12v 2005 NSPL TRUNK STOCK WORLD RECORD HOLDER(148.1)12v 2005 1x NSPL TRUNK STOCK WORLD CHAMPION 12v 2004 2nd PLACE TRUNK STOCK WORLD FINALIST (141.6)12v 1989 Installed my first system Posts: 1588 | From: Elizabeth City,NC | Registered: Feb 2006
| IP: Logged |
quote:Originally posted by Mr.Sears one 15 sub from hell:
quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence?
Ok.......let me break it down a little better.He's right you don't subtract the nominal impedance.I think you misunderstood the original post.Ex...nominal impedance is .25,and your measurements caculate to 2.5 ohms.Your amp is seeing 2.5 ohms,so your rise is 2.25.You are only subtracting to see your actual impedance rise,not what impedance your amps are seeing.Hope that clears things up.
Thank you i got it mine is a 1.6 rise but amps are seeing 2.1 for burps . that is not too bad . maybe if i got to .25 ohms and roll into the burps i maybe be louder with a lower imp rise .
Then again it maybe unstable for the amps ,not sure .
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL TEAM POWERMASTER TEAM SOUNDSTREAM Posts: 2678 | From: Everywhere | Registered: Oct 2004
| IP: Logged |
quote:Originally posted by SPLRON: Thank you i got it
No problem.
-------------------- MR. SEARS (LOUD) LIL WHITE CAVY TEAM HIGH X-CURSION STEVE(TEAM CAPTAIN) TEAM DD 2009 SS-NW AND STREET C(THEY'RE HERE) 2008 TRUNK MODIFIED WORLD RECORD HOLDER (153)12v certified legal TL 2008 2007 PRO TRUNK WORLD FINALS (150.9<150.2)12v 2006 PRO TRUNK 1x WORLD RECORD HOLDER(151.2)12v 2005 NSPL TRUNK STOCK WORLD RECORD HOLDER(148.1)12v 2005 1x NSPL TRUNK STOCK WORLD CHAMPION 12v 2004 2nd PLACE TRUNK STOCK WORLD FINALIST (141.6)12v 1989 Installed my first system Posts: 1588 | From: Elizabeth City,NC | Registered: Feb 2006
| IP: Logged |
![[Cool]](cool.gif)
![[Wink]](wink.gif)
![[Blob]](graemlins/blob.gif)
Printer-friendly view of this topic