Strange DMM Readings

ecbmxer · 12-24-2005, 02:27 PM

OK, so I got a fuse for my multimeter and took some readings to set gains. I set my gains for the subs (500W subs wired to 2 ohms) to around 33V or so with a 50Hz 0Db test tone. and then I went to set my comps. I unplugged one of the speakers and played my 1kHz 0Db test tone and the voltage was only 7V or so. I maxed out the gains and it went up to 12V maximum. I needed it to be around 18V or so. This is for the advertised 85W typical, if I wanted it for the 100W speaker handling power, it would be 20V. Even the lowest RMS rating for the amp is 50W, which would mean 14.14V. Could the impedence of wiring and everything create lower voltages? Now for the second thing. I measured the impedence of my subs just for the heck of it. I have 2 DVC subs that are dual 4 ohm. I have the voice coils wired in series to create 4 ohms per sub, and the subs wired in paralell to create a 2 ohm total load. Now when I measured the total sub output, it was 4 ohms! I went to the terminals for each sub on the side of my box and measured them and they said 5 ohms each. Is this just due to the terminals and wire also? I understand how to wire things in parallel and series so I really don't think its my wiring. I'm really confused here, and it doesn't seem like I'm getting maximum performance out of my system.

f00dstamps · 12-24-2005, 03:08 PM

if you have dual voice coils that are 4 ohms, they may be 4 ohms EACH. in series, they would be 8 ohms. parallel that with the other sub and that will be a 4 ohm load across both subs total.

i don't know much about speakers but that's how i think you are getting the 4 ohm number.

i don't know how nice your amp is but if it is 1 ohm stable, parallel the dual voice coils and parallel the subs together. POWER!

SoundsGood · 12-24-2005, 03:28 PM

Speaker Ohm values are impedance, not pure resistance because the coil is an inductor. You can't measure impedance with a DMM. This is probably why you are getting strange readings. There are many cheap impedance meters on the market that you could use for this.

ecbmxer · 12-24-2005, 05:19 PM

OK, thats what I thought. I figured that the DMM only read resistance rather than impedence. Haha, I was questioning my ability to wire my subs in series and paralell. And they are dual 2 ohm coils, as in 2 ohms per coil. So I could have an 8 ohm, 2 ohm, or 1/2 ohm total impedence. I am using 2 ohm. My amp is only stable down to 1.33 ohms (or three 4 ohm subs wired in paralell) so I can't use anything below that. Well, still gotta figure out the component voltage thing now.