I have a set of Polk S20 speakers that were dropped and now sound like crap. I'm in the process of replacing the drivers in them.
The specs from Polk's website state that these are 8 ohm speakers, yet when I measure the voice coil of the woofer with my meter I get a reading of 3.56 ohms, which is typical of a 4 ohm woofer.
Why is this?? I understand that an 8 ohm speaker will read less than 8 ohms DC resistance but it shouldn't be this low. So now I am wondering if I need 4 ohm drivers. Confusion!!
The specs from Polk's website state that these are 8 ohm speakers, yet when I measure the voice coil of the woofer with my meter I get a reading of 3.56 ohms, which is typical of a 4 ohm woofer.
Why is this?? I understand that an 8 ohm speaker will read less than 8 ohms DC resistance but it shouldn't be this low. So now I am wondering if I need 4 ohm drivers. Confusion!!
Impedance is the average for the whole speaker across the entire audio range. You won't get that from just measuring the DCR.
The 3.56 reading points to a possible impedance target of 6 ohms for the woofer, and a slightly higher DCR coil will get you there. Even so, It is not deemed necessary for a 8 ohms speaker to exhibit a specific value at DC. It's not a valid measurement.
The 3.56 reading points to a possible impedance target of 6 ohms for the woofer, and a slightly higher DCR coil will get you there. Even so, It is not deemed necessary for a 8 ohms speaker to exhibit a specific value at DC. It's not a valid measurement.
In fact, Polk just say "compatible with 8 ohm outputs".
In practice, most bass drivers these days are 4 ohm units to increase sensitivity.
P_Signature-Series_Product-Info-Sheet_EU.pdf
In practice, most bass drivers these days are 4 ohm units to increase sensitivity.
P_Signature-Series_Product-Info-Sheet_EU.pdf
I'd suspect impedance is the least of your troubles here. Albeit I agree that it is likely a 4 ohm midbass driver:
W 170 S - 4 Ohm | Visaton
You can also buy 8 ohm versions:
W 170 S - 8 Ohm | Visaton
If you dropped the speaker, it is likely the pressed steel bass chassis has bent under the mass of the big magnet and is now rubbing voicecoil:
Polk Audio Signature S20 allvanyos hangfal teszt | av-online.hu
A typical 6" speaker with a 4 ohm bass might look like this:
CT 142 mod – Boxsim Projektdatenbank
Seems to me that step one is to measure the midbass cutout and see what might fit as a replacement. It seems these are plastic coned 6" basses. Usually come in 170 and 180mm chassis. But it's all a bit erratic. So get that measuring tape out! Everything else is adjustable. 🙂
W 170 S - 4 Ohm | Visaton
You can also buy 8 ohm versions:
W 170 S - 8 Ohm | Visaton
If you dropped the speaker, it is likely the pressed steel bass chassis has bent under the mass of the big magnet and is now rubbing voicecoil:
Polk Audio Signature S20 allvanyos hangfal teszt | av-online.hu
A typical 6" speaker with a 4 ohm bass might look like this:
CT 142 mod – Boxsim Projektdatenbank
Seems to me that step one is to measure the midbass cutout and see what might fit as a replacement. It seems these are plastic coned 6" basses. Usually come in 170 and 180mm chassis. But it's all a bit erratic. So get that measuring tape out! Everything else is adjustable. 🙂
I have the bass driver completely removed from the cabinet and sitting on my bench. The rubber surround and cone was damaged so I completely cut it away from the voice coil just check out the inner workings of a speaker. I can clearly see the voice coil and I'm just measuring the DC resistance across the terminals. That's why I was so surprised to see the DCR of 3.5 ohms when Polk specs say it's an 8 ohm speaker.
I've found several drivers on Parts Express that will work. Just want to get one with the correct impedance.
I've found several drivers on Parts Express that will work. Just want to get one with the correct impedance.
It's a 4 ohm NOMINAL midbass.
If Polk call it an 8 ohm NOMINAL speaker, that is just an average value.
Incorporating highs and lows.
Simple as. The DC measurement of a driver tells you what it is. Usually about 3 ohms for a 4 ohm nominal driver.
If Polk call it an 8 ohm NOMINAL speaker, that is just an average value.
Incorporating highs and lows.
Simple as. The DC measurement of a driver tells you what it is. Usually about 3 ohms for a 4 ohm nominal driver.