Proper setup to avoid blown tweeters in M70s

EdDinIL

I recently dove headfirst into my first home theater set-up:

Receiver: Denon AVR-890
Fronts: 2 Polk Monitor 70s
Center: Polk CS2
Surrounds: 2 Polk Monitor 40s
Subwoofer: None yet (yeah, yeah, I know)

I have it all wired together (no bi-amping yet) with 14-ga. speaker wire and banana plugs from Monoprice. The system sounds great.

I've read in Club Polk and elsewhere that M70s are inefficient speakers and there is a risk of blown tweeters with an underpowered receiver. The AVR-890's rated output is 105 W per channel at 8 ohms. Is that considered "underpowered" for the M70s?

The AVR-890 allows for bi-amping through the surround back connections. According to the manual, "When in the 'Front A Bi-Amp' and 'Front B Bi-Amp' modes, the same signals are output from the front speaker terminals and the AMP ASSIGN terminals." I assume that means there's no difference between the signals, so it doesn't matter which connection goes to the woofer and tweeter posts on the speakers.

Does this mean that I would get the power from the 105 W front channel and the 105 W surround back channel, for a total of 210 W at 8 ohms going to the front speakers? If that's the proper math, it sounds like that would solve any issues with the receiver being underpowered.

If bi-amping won't solve an "underpowered" problem, how would I connect the AVR-890 to an amplifier? There is only one pre-out connection, and it appears to be intended for the aforementioned yet-to-be-purchased subwoofer.

Thanks in advance!

Ed

cnh

WELCOME TO CLUB POLK!

The M70s are not inefficient. People blow their tweeters by clipping their AVRs....playing them to distortion levels.

The Denon should be able to handle them...no problem. Just don't clip the amp!

Also...I advise that for the break-in period DON'T PUSH the 70s....let them run at mid-power or less. If you break them in properly you'll be less likely to off your tweeters later.

I've run M70s on an Denon AVR 887 years ago...biwired at decent volumes.....never blew a tweeter...plenty loud!

Also...bi-wiring from the same Denon will NOT double your wattage...you are still pushing the M70s with 105 watts a channel....that power is NOT additive!

cnh

EdDinIL

Thanks for the info and tips. It's been 20 years since I had to do electronic circuitry math, figuring out voltages, amps, etc., and I'm not even sure if the same basic calculations apply here. So, please bear with me and feel free to correct every mistake and invalid assumption you find in the next paragraph.

If I don't bi-wire, the front speaker connection would be powering the woofer and tweeter via the jumpered posts, thus the 105 W (and its associated amps and volts) would be applied to the circuits in parallel. If I dejumper the posts and bi-wire, then I'd be applying 105 W of power from the front speaker connection to the tweeters (top posts) and 105 W of power from the surround back connection to the woofer (bottom posts). My assumption is that because the circuits are now separate, more power is being applied to each circuit, thus the receiver will be more easily able to drive the speaker without going into clipping.

Confession: I have turned the volume up past the 0 db reference point for a short time, just to demo it. There was no distortion at all. I won't do that again, though.

josephclemente

I jumped on today's Newegg Monitor 70 deal but then started reading about easily blown tweeters with regular A/V receivers which sound scary.

After further reading, I believe I have nothing to worry about since I keep my volume levels reasonable anyway.

I'm considering setting the speakers to "small" - am I right in thinking that this will provide the best sound quality from my available receiver power (I am also using a sub)? Also, would this be a good solution for other forum members reading who still want to play their Monitor 70's louder but let a sub handle most of the bass?

I'm going to use them with a Pioneer VSX-819H-K which claims to do:

Power Amplifier Design: Discrete (Advanced Direct Energy)
Surround Power: 110 x 5
Channels: 5
THD: 1 kHz w// 0.05% THD @ 8 ohm

wutadumsn23

EdDinIL wrote: »

If I don't bi-wire, the front speaker connection would be powering the woofer and tweeter via the jumpered posts, thus the 105 W (and its associated amps and volts) would be applied to the circuits in parallel. If I dejumper the posts and bi-wire, then I'd be applying 105 W of power from the front speaker connection to the tweeters (top posts) and 105 W of power from the surround back connection to the woofer (bottom posts). My assumption is that because the circuits are now separate, more power is being applied to each circuit, thus the receiver will be more easily able to drive the speaker without going into clipping.

This is a common misconception when it comes to Bi-Wiring (not Bi-Amping) which is what you are trying to do. You have to remember that the AVR only has one power source and will get it's power for all the channels from that same source. Adding a second set of speaker wire, taking off the metal jumper and connecting them to the other set of posts isn't going to give you much in the way of additional power, nevermind double it. If you have the wire, try it and see what you think, if there is a difference at all, it won't be the night and day difference you are hoping for. The best way to get more/better power to your speakers is with an external amp, which if I am correct won't be an option for you since the 890 lacks the pre outs needed to run an amp. The 890 will do a fine job of running those 70's as stated above. I run mine with an Onkyo TX-SR806, and have had no issues. Good luck and welcome to Club Polk.

-Jeff

josephclemente wrote: »

I jumped on today's Newegg Monitor 70 deal but then started reading about easily blown tweeters with regular A/V receivers which sound scary.

After further reading, I believe I have nothing to worry about since I keep my volume levels reasonable anyway.

I'm considering setting the speakers to "small" - am I right in thinking that this will provide the best sound quality from my available receiver power (I am also using a sub)? Also, would this be a good solution for other forum members reading who still want to play their Monitor 70's louder but let a sub handle most of the bass?

I'm going to use them with a Pioneer VSX-819H-K which claims to do:

Power Amplifier Design: Discrete (Advanced Direct Energy)
Surround Power: 110 x 5
Channels: 5
THD: 1 kHz w// 0.05% THD @ 8 ohm

Don't sweat the 70's, they are very easy to drive and you won't blow the tweeters unless you clip the AVR by playing it too loud and cnh said above. I run mine with an Onkyo TX-SR806 and have had zero tweeter issues in the year and a half I have been running them. I would set them to "Full Band" myself and set the crossovers at 80hz, then set your sub to 120hz and you will be fine. What sub are you running? If you don't have one yet, I would take a serious look at the PSW505, it is on sale at Newegg for $229, and for that price you can't beat it with a stick. Good luck and congrats on the 70's, they are a steal at what you got them for and IMHO are the most bang for the buck out there for HT speakers. Welcome to Club Polk.

-Jeff

EdDinIL

wutadumsn23 wrote: »

This is a common misconception when it comes to Bi-Wiring (not Bi-Amping) which is what you are trying to do. You have to remember that the AVR only has one power source and will get it's power for all the channels from that same source. Adding a second set of speaker wire, taking off the metal jumper and connecting them to the other set of posts isn't going to give you much in the way of additional power, nevermind double it. If you have the wire, try it and see what you think, if there is a difference at all, it won't be the night and day difference you are hoping for. The best way to get more/better power to your speakers is with an external amp, which if I am correct won't be an option for you since the 890 lacks the pre outs needed to run an amp. The 890 will do a fine job of running those 70's as stated above. I run mine with an Onkyo TX-SR806, and have had no issues. Good luck and welcome to Club Polk.

I bi-wired it last night, and as you predicted (and I expected) I didn't get a night-and-day difference. However, I still don't understand why there wouldn't be extra power going to the speakers since it's coming from two channels, not one. I understand it's a single power source, but isn't the AVR capable of applying its rated power to each channel independently?

wutadumsn23 wrote: »

If you don't have one yet, I would take a serious look at the PSW505, it is on sale at Newegg for $229, and for that price you can't beat it with a stick.

Ok, you talked me into it, even if it was $249. Looks like I'll be getting out the Audyssey microphone one more time.

Thanks!

Ed

WilliamM2

EdDinIL wrote: »

I bi-wired it last night, and as you predicted (and I expected) I didn't get a night-and-day difference. However, I still don't understand why there wouldn't be extra power going to the speakers since it's coming from two channels, not one. I understand it's a single power source, but isn't the AVR capable of applying its rated power to each channel independently?

If you are powering each speaker from a separate channel, you are bi-amping, not bi-wiring. The thing is, even if the AVR is capable of delivering it's full rated output to all channels (most are not), when the woofers are drawing 105 watts, the high section will only draw 10-15 max. So you won't get twice the power, not even close.

josephclemente

wutadumsn23 wrote: »

I would set them to "Full Band" myself and set the crossovers at 80hz, then set your sub to 120hz and you will be fine. What sub are you running?

My sub is a PSW111, I've been really happy with it. The new speakers should arrive tomorrow - hopefully they will survive the shipping!

wutadumsn23

EdDinIL wrote: »

I bi-wired it last night, and as you predicted (and I expected) I didn't get a night-and-day difference. However, I still don't understand why there wouldn't be extra power going to the speakers since it's coming from two channels, not one. I understand it's a single power source, but isn't the AVR capable of applying its rated power to each channel independently?



Ok, you talked me into it, even if it was $249. Looks like I'll be getting out the Audyssey microphone one more time.

Thanks!

Ed

Yeah, but if you didn't try it you would always wonder what if, no matter what we told you, lol. You won't be dissapointed by that 505, it is IMHO, one of the best "entry level" subs out there for the price.

-Jeff

josephclemente wrote: »

My sub is a PSW111, I've been really happy with it. The new speakers should arrive tomorrow - hopefully they will survive the shipping!

The PSW111 will blend nicely with those 70's, keep your eyes open and you may be able to score something a little bit better off CL or Epray. The 505 is always an option too, but if you are happy with what you have, that is all that matters. I have a PSW125 and it does a very good job in my humble HT with my 70's up front. Let us know how it sounds all hooked up.

-Jeff

comfortablycurt

Bi-wiring with an AVR has little to no benefits in my experience.

Generally speaking, the power for all of the channels on an AVR comes from one common power block. Until you get into much higher end receivers(such as the Pioneer Elites), there aren't going to be individual power amps for each channel.

For starters, your Denon likely isn't even putting out it's rated 105 wpc...it's likely closer to 75 wpc with all channels driven simultaneously. That 105 wpc rating is most likely with either two, or even just one speaker being driven at a time.

Connecting your speakers to multiple pairs of speaker outputs isn't going to double your wattage. As I said, the power for all channels comes from one common power block. Now, by running two more cables between the speakers and the receiver...how exactly is that adding more power? It's not as if you're hooking it up to a second power amp. You're simply making an additional connection to the same power amp. It's not as if the power amp is going to start generating twice as much power because it has two connections going to each speaker.

A speaker is only going to draw as much power as it needs at any given time anyway.

As I said before, that 105 wpc rated output, is likely with one channel driven. Keep in mind that the AVR has just one power amp for all channels combined. If it's max rated output with one channel driven is 105 watts...how is it going to put out 210 watts with two channels being driven? It's essentially impossible.

AVR bi-amping is basically a marketing ploy. Some people have reported improvements...but most people will say that they heard absolutely no difference at all. In my experience, it made absolutely no difference. If anything...the mid-range seemed a bit more withdrawn possibly(which is NOT a good thing).

I had my RTi8's bi-wired with my Onkyo 606 for a while. I checked it's maximum volume output with an SPL meter both before and after bi-wiring. I gained absolutely no additional volume after bi-wiring.


I don't know where you got your information, but the Monitor series isn't particularly inefficient. They're actually pretty easy to drive, and don't require tons of current to sound fantastic.


The only way to really add more power, is by adding an external amp. Aside from the subwoofer pre-out you mentioned(which you can't use to add an amp for the front channels), your AVR doesn't have pre-outs. You'd need to get an AVR with preouts before adding an amp.

wutadumsn23

Well done Curt. Nail, head, hamme!! That's all she wrote.

-Jeff

josephclemente

I got my speakers today! Both Monitor 70 boxes had damage, one was pretty bad. I didn't open them yet, but from what I could see the speakers look OK peaking through the boxes where they are ripped open. Once I get home I'll take a good look at them.

wutadumsn23

I hope they weren't damaged, sounds like they had a pretty rough ride. One thing I do know is you won't be dissapointed by those 70's one bit. They are, IMHO, one of the best "entry level" speaker Polk makes, esp. for the prices they can be had for now. Good luck and let us know how it turns out.

-Jeff

EdDinIL

comfortablycurt wrote: »

For starters, your Denon likely isn't even putting out it's rated 105 wpc...it's likely closer to 75 wpc with all channels driven simultaneously. That 105 wpc rating is most likely with either two, or even just one speaker being driven at a time.

Now that makes sense to me. I was operating under the mistaken assumption that each channel would get that rated power and that the amp was capable of it.

Thanks for everyone's help.

josephclemente wrote: »

I got my speakers today! Both Monitor 70 boxes had damage, one was pretty bad. I didn't open them yet, but from what I could see the speakers look OK peaking through the boxes where they are ripped open. Once I get home I'll take a good look at them.

When my M70s, M40s and CS2 arrived, all four boxes had some significant tears, but there was no damage to the speakers themselves.

Time to go play with the PSW505 that arrived today!

josephclemente

wutadumsn23 wrote: »

I hope they weren't damaged, sounds like they had a pretty rough ride. One thing I do know is you won't be dissapointed by those 70's one bit. They are, IMHO, one of the best "entry level" speaker Polk makes, esp. for the prices they can be had for now. Good luck and let us know how it turns out.

-Jeff

I took a very good look at them and they are flawless.

I haven't listened to them much yet, but so far I like them. I still need to play around with crossover settings and see what works best.

Swede_Deep

I just signed off the UPS a few hours ago. Same here it was some holes and tears but luckily no damage to the speakers. Now the receiver and cables are due Thursday. Can't wait!

Front: Monitor 70's
Center: CS2
Rear: Monitor 40's
Sub: PSW505
Receiver: Onkyo TX-SR707
Panasonic DMP-BD65
Panasonic TC-58S1

wutadumsn23

^^ reported