Professional opinion: Can I run 4 ohm and 8 ohm speakers together?

[jay21112]

Hi, I stumbled across this site a while ago and I have been coming here more and more often. I have a "beginnerish" question here. I'll post the question first for those short on time. But for those who want to know why I'm asking, I'll post the background after.

Direct Question
I have 7.1 surround sound. Can I run 4 ohm (Polk Audio LSi) speakers on all channels except the front left and right channels which are running 8 ohm speakers (Boston Acoustics VR3)? The Receiver is an Onkyo TX-SR805 which is supposedly rated for 4 ohm performance.

Background
So, within the last two years I moved into my first house, and I really wanted to create a home theater. I didn't have a whole lot of money leftover so I did what I could. I bought a Mitsubishi 73" rear projection, the Onkyo TX-SR805, a PS3, a Boston Acoustics 5.1 surround system, and the Boston Acoustics VR3 front speakers to make it into 7.1 surround sound.

Well, I've finally recouped some savings, and my goal WAS to go big and upgrade to 11.2 surround sound with the Yamaha RX-Z11 (yeah, until HDMI upgraded to 1.4....damn you 3D, why are you so appealing....and yet so incompatible with everything in the universe made before 2010). Well, in doing so I wanted to switch over to the Polk Audio LSi line to make up the 11.2 channels. So, as I was researching all the gear, I saw some great prices on some LSi speakers....so I started buying them up. I HAD figured that as I bought them, I'd just replace the Boston Acoustics speakers one by one, which is why I started buying them before buying the 11.2 receiver. I figured I could just use them for now until Yamaha decided to upgrade their 11.2 flagship to HDMI 1.4.

Well, I emailed customer service at Polk asking them what their recommendation was for the presence speakers, and they said I should stick with 4 ohm speakers because I shouldn't mix 4 ohm and 8 ohm. Well..this killed my plan of replacing speakers one by one. SO, currently I have 9 Polk Audio LSi speakers collecting dust in my closet while I try to find a decent price on the Polk Audio LSi25s....(I mean come on, why can't someone have a sale on these and stop my misery!)

PS: the other 2 speakers I bought are the Polk subwoofers, and I was able to at least hook those up, so at least they aren't collecting dust....

If it helps at all, once or twice I've been able to set the volume on the Onkyo to zero when I watch movies. But USUALLY it's set to somewhere between -5 and -10 for movies, and all the way down to -25 for PS3 games.

So what do you think? Can I run (5) 4-ohm speakers and (2) 8-ohm speakers on the Onkyo TX-SR805 without hurting either the speakers or the Onkyo?

 

[mike c]

as long as each speaker has it's own channel (no parallel connection), yes you can.

it would help a lot if you had a subwoofer to crossover the bass from the other channels to. (sorry if you mentioned it in your post) that would lighten the load on your receiver.

 

[jamie2112]

Yes you can as Mike said if all speakers have their own output channel.Your screen name is dangerously close to mine

 

[jay21112]

Looks like I can dust off the LSI's!

Thanks.
I do have a sub (2 of them), and each speaker has it's own individual hookup in the back of the receiver, so no parallel wiring and they will all be on their own channel.

I'm really incredibly happy to hear this because it's been a downer to see these things and not hear them!!!

And Jamie: great minds think alike. Actually I think I created this name/number combo way back with AOL online when every iteration of Jay was taken. So I finally just threw a bunch of numbers in there thinking "There's NO WAY anyone else out there would have this random combination of numbers." And I was right. So the name/number combo just stuck with me every since.

 

[TLS Guy]

Hi, I stumbled across this site a while ago and I have been coming here more and more often. I have a "beginnerish" question here. I'll post the question first for those short on time. But for those who want to know why I'm asking, I'll post the background after.

Direct Question
I have 7.1 surround sound. Can I run 4 ohm (Polk Audio LSi) speakers on all channels except the front left and right channels which are running 8 ohm speakers (Boston Acoustics VR3)? The Receiver is an Onkyo TX-SR805 which is supposedly rated for 4 ohm performance.

Background
So, within the last two years I moved into my first house, and I really wanted to create a home theater. I didn't have a whole lot of money leftover so I did what I could. I bought a Mitsubishi 73" rear projection, the Onkyo TX-SR805, a PS3, a Boston Acoustics 5.1 surround system, and the Boston Acoustics VR3 front speakers to make it into 7.1 surround sound.

Well, I've finally recouped some savings, and my goal WAS to go big and upgrade to 11.2 surround sound with the Yamaha RX-Z11 (yeah, until HDMI upgraded to 1.4....damn you 3D, why are you so appealing....and yet so incompatible with everything in the universe made before 2010). Well, in doing so I wanted to switch over to the Polk Audio LSi line to make up the 11.2 channels. So, as I was researching all the gear, I saw some great prices on some LSi speakers....so I started buying them up. I HAD figured that as I bought them, I'd just replace the Boston Acoustics speakers one by one, which is why I started buying them before buying the 11.2 receiver. I figured I could just use them for now until Yamaha decided to upgrade their 11.2 flagship to HDMI 1.4.

Well, I emailed customer service at Polk asking them what their recommendation was for the presence speakers, and they said I should stick with 4 ohm speakers because I shouldn't mix 4 ohm and 8 ohm. Well..this killed my plan of replacing speakers one by one. SO, currently I have 9 Polk Audio LSi speakers collecting dust in my closet while I try to find a decent price on the Polk Audio LSi25s....(I mean come on, why can't someone have a sale on these and stop my misery!)

PS: the other 2 speakers I bought are the Polk subwoofers, and I was able to at least hook those up, so at least they aren't collecting dust....

If it helps at all, once or twice I've been able to set the volume on the Onkyo to zero when I watch movies. But USUALLY it's set to somewhere between -5 and -10 for movies, and all the way down to -25 for PS3 games.

So what do you think? Can I run (5) 4-ohm speakers and (2) 8-ohm speakers on the Onkyo TX-SR805 without hurting either the speakers or the Onkyo?

The advice from Polk is on par with their speakers.

 

[MinusTheBear]

Yes, you can mix 4ohm and 8ohm rated speakers together. Most receivers can handle 4 ohm speakers without shutdown/overheating issues when used within their limits, selecting the impedance switch to its highest setting and keeping the unit well ventilated.

Those nominal ratings of 4 or 8 ohm really don't mean anything without looking at the impedance graph. Impedance is not constant, it varies with frequency. What you have to be careful with 4 ohm rated speakers is the impedance dips. I've seen some speakers rated at 8 ohm that have a 3 ohm dip high in the frequency range. Some speakers rated at 4 ohm might have some nasty dips down to 3 or 2 ohms below 100hz. This could possibly cause some problems with receivers and even amps to go into protect mode.

Like Mike_C mentioned if you cross the speakers off at say 80hz to the sub it will take some of the load off of the avr. What I got from Gene's article on impedance is that impedance dips happening in the lower frequencies are the ones that cause problems.

 

[jay21112]

The advice from Polk is on par with their speakers.

I'm a little new, so I'm unsure what this answer is truly saying.

Is it saying:
1.) Polk's answer is what should be used for Polk speakers. Meaning that if a person is using Polk speakers, then they absolutely should not mix impedences.

Or:

2.) Polk's answer is poor quality, just like their speakers are poor quality.

If the second answer is what you were really saying....come on man, don't burst my bubble. I haven't even plugged these things in yet!
I mean, I spent less than $500 for 5 speakers AND a subwoofer for my last theater system. Moving from that to the Polk LSi line is like moving from the basement to the penthouse for me. I mean, one day I might be able to afford those beautiful RBH sound speakers I see in the reference home here, but right now I don't even want to do the math to figure out how many paychecks it would take to pay for it. eek.

 

[jay21112]

Yes, you can mix 4ohm and 8ohm rated speakers together. Most receivers can handle 4 ohm speakers without shutdown/overheating issues when used within their limits, selecting the impedance switch to its highest setting and keeping the unit well ventilated.

Those nominal ratings of 4 or 8 ohm really don't mean anything without looking at the impedance graph. Impedance is not constant, it varies with frequency. What you have to be careful with 4 ohm rated speakers is the impedance dips. I've seen some speakers rated at 8 ohm that have a 3 ohm dip high in the frequency range. Some speakers rated at 4 ohm might have some nasty dips down to 3 or 2 ohms below 100hz. This could possibly cause some problems with receivers and even amps to go into protect mode.

Like Mike_C mentioned if you cross the speakers off at say 80hz to the sub it will take some of the load off of the avr. What I got from Gene's article on impedance is that impedance dips happening in the lower frequencies are the ones that cause problems.

Subs crossed over at 80hz - check.
Well ventilated receiver - check.
Impendence switch set to 8 ohm - check.

But it sounds like if the receiver does do something screwy, then I should change the impedence switch to 4 ohms. Again, the receiver says it's a high current receiver so I think I'm good.

Guess I got myself a weekend project. Time to mount some speakers.

 

[MinusTheBear]

Subs crossed over at 80hz - check.
Well ventilated receiver - check.
Impendence switch set to 8 ohm - check.

But it sounds like if the receiver does do something screwy, then I should change the impedence switch to 4 ohms. Again, the receiver says it's a high current receiver so I think I'm good.

Guess I got myself a weekend project. Time to mount some speakers.

Leave the impedance switch set to 8 ohms. For a detailed explanation of the impedance switch and why to use the 8 ohm setting rather than 4 when using 4 ohm rated speakers with receivers, read this link below.

You're good to go. Hook everything up and enjoy!

http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1

 

[yepimonfire]

Yes, you can mix 4ohm and 8ohm rated speakers together. Most receivers can handle 4 ohm speakers without shutdown/overheating issues when used within their limits, selecting the impedance switch to its highest setting and keeping the unit well ventilated.

Those nominal ratings of 4 or 8 ohm really don't mean anything without looking at the impedance graph. Impedance is not constant, it varies with frequency. What you have to be careful with 4 ohm rated speakers is the impedance dips. I've seen some speakers rated at 8 ohm that have a 3 ohm dip high in the frequency range. Some speakers rated at 4 ohm might have some nasty dips down to 3 or 2 ohms below 100hz. This could possibly cause some problems with receivers and even amps to go into protect mode.

Like Mike_C mentioned if you cross the speakers off at say 80hz to the sub it will take some of the load off of the avr. What I got from Gene's article on impedance is that impedance dips happening in the lower frequencies are the ones that cause problems.

alot of speakers dip below 100hz, anyone who has had the volume too high (guilty) on a lower powered receiver (like 60w or less) will notice it goes into protect every bass kick haha. DO NOT CHANGE THE IMPEDANCE SETTING. this is only on there because of saftey regulations and it will seriously limit your receivers voltage rails and cause lots of distortion at significant volumes. theoretically combining 4 and 8 ohm speakers is 6ohms, most amps can handle 6 ohms nominal ok. i have run two sets of 4ohm speakers on an 8 ohm rated receiver without problems, yes the receiver will get hot, but if its ventilated it won't hurt it. ive run it for hours on end at high volumes with no issues.

 

[yepimonfire]

I'm a little new, so I'm unsure what this answer is truly saying.

Is it saying:
1.) Polk's answer is what should be used for Polk speakers. Meaning that if a person is using Polk speakers, then they absolutely should not mix impedences.

Or:

2.) Polk's answer is poor quality, just like their speakers are poor quality.

If the second answer is what you were really saying....come on man, don't burst my bubble. I haven't even plugged these things in yet!
I mean, I spent less than $500 for 5 speakers AND a subwoofer for my last theater system. Moving from that to the Polk LSi line is like moving from the basement to the penthouse for me. I mean, one day I might be able to afford those beautiful RBH sound speakers I see in the reference home here, but right now I don't even want to do the math to figure out how many paychecks it would take to pay for it. eek.

polk is not poor quality at all, they make some very good speakers at impressive prices, but i cant disagree that they do say some retarded things, like bi-wiring

 

[jay21112]

Good news and Bad news

Good News
Ok, so I hooked up the five 4 ohm speakers (surrounds, rear surround, and center channel)....and it worked! Yay! Thanks everyone!!!

Bad News
I have a bad subwoofer and a bad speaker!
The LED light on my subwoofer mysteriously goes on and off. I emailed Polk CS last week and they said they thought it was the amplifier. They said they are sending me out a new amplifier which I can easily switch out, but I'm still waiting (patiently) for the tracking numbers on that. The sub seems to work fine, but the light is the interface; it's how you tell the volume, and it's involved in the calibration. So if it doesn't work, I can't accurately change the volume or calibrate it.

Then, when I plugged in the new speakers yesterday, and ran the auto calibration, I noticed that one of the rear surrounds sounded a lot quieter than all the rest. When I ran the pink noise to fine tune the levels, it was like that speaker wasn't putting out all the pink noise; like it was missing frequencies. In fact, I couldn't even get it to reach the same noise level at the listening position as the other speakers. The receiver's max adjustment is +12DB, and the speaker was still quieter! I switched speaker cables and channels with a speaker that I knew was working, and same thing. So it's definitely the speaker. I removed the metal jumper and plugged two wires into just the top speaker posts and got noise out of both tweeters, but it seemed to be missing something. Then I plugged two wires into just the bottom speaker posts and only got noise out of 1 woofer...and it still missed something. So I think this speaker needs some b-vitamins or something. I emailed Polk CS yesterday, but I'm sure they are on holiday until tomorrow....

 

[jay21112]

Setup

I included a few pics of the new setup. Don't mind the loose wires, I haven't yet put them back in the raceways. And the 2 front and 2 rear presence speakers aren't hooked up yet (I still haven't bought the Yamaha, yet). And no making fun of the couch. I want to replace it with theater seats, but one thing at a time....

 

[MinusTheBear]

Good News
Ok, so I hooked up the five 4 ohm speakers (surrounds, rear surround, and center channel)....and it worked! Yay! Thanks everyone!!!

Bad News
I have a bad subwoofer and a bad speaker!
The LED light on my subwoofer mysteriously goes on and off. I emailed Polk CS last week and they said they thought it was the amplifier. They said they are sending me out a new amplifier which I can easily switch out, but I'm still waiting (patiently) for the tracking numbers on that. The sub seems to work fine, but the light is the interface; it's how you tell the volume, and it's involved in the calibration. So if it doesn't work, I can't accurately change the volume or calibrate it.

Then, when I plugged in the new speakers yesterday, and ran the auto calibration, I noticed that one of the rear surrounds sounded a lot quieter than all the rest. When I ran the pink noise to fine tune the levels, it was like that speaker wasn't putting out all the pink noise; like it was missing frequencies. In fact, I couldn't even get it to reach the same noise level at the listening position as the other speakers. The receiver's max adjustment is +12DB, and the speaker was still quieter! I switched speaker cables and channels with a speaker that I knew was working, and same thing. So it's definitely the speaker. I removed the metal jumper and plugged two wires into just the top speaker posts and got noise out of both tweeters, but it seemed to be missing something. Then I plugged two wires into just the bottom speaker posts and only got noise out of 1 woofer...and it still missed something. So I think this speaker needs some b-vitamins or something. I emailed Polk CS yesterday, but I'm sure they are on holiday until tomorrow....

Nice setup.

A few things you should check. Are you getting any sound out of the subwoofer. Does it have a standby/auto on feature? Is it turning on and off when the LED changes? You might want to look at the subwoofer pre-out setting in the receiver (what does this number read). The rubbish auto calibration could have set this much too low. An example is -12. In this case the sub might not be getting a strong enough signal to stay on and you would need to increase that number.

For the speaker, put the jumper back on the binding posts and make sure it is secure and not loose. How many drivers does that speaker have, does each one work?

 

[jay21112]

Nice setup.

A few things you should check. Are you getting any sound out of the subwoofer. Does it have a standby/auto on feature? Is it turning on and off when the LED changes? You might want to look at the subwoofer pre-out setting in the receiver (what does this number read). The rubbish auto calibration could have set this much too low. An example is -12. In this case the sub might not be getting a strong enough signal to stay on and you would need to increase that number.

For the speaker, put the jumper back on the binding posts and make sure it is secure and not loose. How many drivers does that speaker have, does each one work?

The subwoofer is strange. I have 2 subs hooked up to the same preout by a Y connector. The other sub is absolutely fine. The sub in question remains on the entire time, but only the LED goes on and off. I thought it was just a faulty LED, but Polk CS said they are sending me a new amp for the sub. I'm guessing the LED is attached to the amp?

For the speaker, I did put the binding post back on, and hooked up one set of wires to the top binding posts. Still same listless sound. I'm not sure how to answer the driver question. Where would I find that info? The speaker has 2 tweeters and 2 woofers and it's able to be set to dipole or bipole. Not sure if that helps any. I got a response from Polk CS today, and they said they think it's a bad woofer, and that they are sending me out a new woofer.

I'll say this, if the new amp and new woofer fixes the problems, I'm writing a letter to Polk CS, praising them. I've never had an easier CS experience in my life. I email them saying I have a problem, and they email me back saying they are sending out a replacement. I have nothing but good things to say about them up to this point.

 

[yepimonfire]

how do the new polk subs sound? hopefully better then their old ones...

 

[jay21112]

how do the new polk subs sound? hopefully better then their old ones...

Everything in life is relative, and I can only compare them to the subwoofer I had in there before, which was the subwoofer from the Boston Acoustics MCS 5.1 surround sound kit.

It's like night and day. They are louder yes, but what amazes me is how much clearer they sound. It's almost like I feel the bass instead of hearing it. What comes to mind is "sonic clarity."

Again, I can only compare them to what I've heard. But, I can honestly say, they are, by far, the best subwoofer I have ever owned.

 

[yepimonfire]

heres the true test, polks subs original problems were port noise and bottoming out. get WOTW and go to the scene where the pod comes out of the ground, then you will truly know.

 

[jay21112]

heres the true test, polks subs original problems were port noise and bottoming out. get WOTW and go to the scene where the pod comes out of the ground, then you will truly know.

Sounds like fun. I'll have to move WOTW up on the Netflix cue.

I haven't watched too many big movies since they have been hooked up, but I did watch the new Clash of the Titans movie. While the movie itself wasn't anything to write home about, the scene when the kracken came out of the water was amazing. There was some great sub response on that.

 

[MinusTheBear]

The subwoofer is strange. I have 2 subs hooked up to the same preout by a Y connector. The other sub is absolutely fine. The sub in question remains on the entire time, but only the LED goes on and off. I thought it was just a faulty LED, but Polk CS said they are sending me a new amp for the sub. I'm guessing the LED is attached to the amp?

For the speaker, I did put the binding post back on, and hooked up one set of wires to the top binding posts. Still same listless sound. I'm not sure how to answer the driver question. Where would I find that info? The speaker has 2 tweeters and 2 woofers and it's able to be set to dipole or bipole. Not sure if that helps any. I got a response from Polk CS today, and they said they think it's a bad woofer, and that they are sending me out a new woofer.

I'll say this, if the new amp and new woofer fixes the problems, I'm writing a letter to Polk CS, praising them. I've never had an easier CS experience in my life. I email them saying I have a problem, and they email me back saying they are sending out a replacement. I have nothing but good things to say about them up to this point.

It does look like CS got it right now that you have explained the problems in more detail.