? of Impedance for Boston Pro 60's

[napalm 10+ year member]

I need some help from all you guru's on the board.

I was checking out one my tweets because it wasn't playing, so I diagnosed the problem and resolved the issue. However, I was randomly checking the resistance, and something didn't add up. On right side of the x-over, the woofer measured 3.2 and the tweet 6.1. That seems fine. But, on the left side of the x-over, the woofer measured 31 with the system turned on, but 3.1 with the system off. So, I checked the right side with the system on it consistenly measured 3.2. Can someone please explain why the resistance is off by a factor of ten for that woofer only.

Napalm

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[walkychalky 10+ year member]

3 ohms

 

[napalm 10+ year member]

Walkychalky,

What do yo mean by 3 ohms? I measured it with my DMM, and it was reading 30 ohms with the power on. However, when I turned the system off, it was at 3.1 ohms

 

[helotaxi 5,000+ posts]

You can't measure resistance with the system powered and get a reliable reading, so unless you are having problems with the system, I wouldn't worry about it.

3.1 ohms is about right for a 4 ohm nominal driver BTW and the tweeter is probably a nominal 6 or 8 ohms, hard to say for sure.

 

[thefunkybunch 10+ year member]

the boston pro woofers should be 3 ohm, so that is right on point. i believe the SL series and down are 4 ohn drivers, but the pro and Z are 3 to pull a bit more power outta the amp //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

and measuring impedence with the system on is useless, as it will fluctuate greatly. even if you measure the impedence and move the woofer with your finger a bit, you'll notice it jump way around until it settles again at 3 ohms.

 

[helotaxi 5,000+ posts]

Depending on the age of the Bostons, they might be 4 ohm. They didn't switch to the 3 ohm mids until fairly recently. If they are supposed to be 3 ohm mids and are measuring more than around 2.6 ohms with a DMM you have a problem. However if they are wired to the rest of the system, you can't determine anything about their DCR with it powered or not as you are measuring the DCR of the entire parallel circuit. It should be lower than 3 ohms for a 3 ohm mid though, unless the caps in the crossoverare discharging into the DMM.

 

[thefunkybunch 10+ year member]

pro 60's are new bostons //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[helotaxi 5,000+ posts]

Fair enough, the rest of my post is still what matters anyway.

 

[jluv 10+ year member]

Mids are 3 ohm and the tweets are 8 ohm.