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  1. #1

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    Default Bi-Amping Monitor 70 Series II Speakers - Internal Crossover Question

    Hello, all! I have what I hope is an interesting question regarding the subject of bi-amping my new Monitor 70 II speakers. I am curious what the internal crossover specs are since I might be experimenting with external crossover components as I integrate these speakers with the subwoofer in my system. My thought is that I might experiment with applying a low-pass filter before sending the signal on to the amps for the woofers. I might even do the same, except in reverse with a high-pass filter, to the mid-range/tweeters. I wonder if doing so might take some unnecessary load off of the equipment or will this make any difference at all? That aside, I'm sure the crossover information might come in handy for any other adventurous audiophiles out there who might consider doing something similar.

    Other than that, any information concerning bi-amping would be helpful and appreciated. I am planning on using two Carver TFM-15cb amps (rated at 100w/ch) in conjunction with a Velodyne SMS-1 sub management unit. Also, I would like to attempt to not cut off the M70s from the low frequencies as much as possible. I don't know; should I feel bad cutting them off at 80Hz or should I try to just remove the frequencies below something nearer to their -3 db point or even not at all?

    Thanks in advance fellow Polk-a-philes!

    (Been recommending Polk for over 20 years ever since I sold them as a spry young stary eyed lad.)
    Last edited by Cybershaman; 10-10-2012 at 10:48 PM. Reason: Added Prefix

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    Welcome aboard- great first post.

    What caught my eye was that you have Monitor 70 II's because the M 70's were my first speaker, so I have a soft spot for them. I never tried bi-amping them so I can't offer any first hand experience with that part. I would take full advantage of that Velo sms-1 to help get things dialed in. I always thought it made good sense to have a low pass filter because it takes the load off the monitors and puts it on the sub. Try using the built in 80 hz one in the sms-1 and see how you like it. If this is done correctly it should make the M70's sound better. But you'll only know for sure by trying it. What kind of sub are you using?

  3. #3

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    Quote Originally Posted by Cybershaman View Post
    My thought is that I might experiment with applying a low-pass filter before sending the signal on to the amps for the woofers. I might even do the same, except in reverse with a high-pass filter, to the mid-range/tweeters.
    The top set of binding posts provides the signal to the tweeter. The second (lower) set of binding posts provides signal to all the other drivers. The two top drivers are the mid range drivers and the bottom two are the bass drivers.


    The speakers are relatively efficient, but a high current amp providing 200 watts or more will drive the mid range and bass quite well. Currently for HT in my setup I like to have the crossover for the sub set at 60 hz. For two channel through a separate tube Pre I do not use a sub. YMMV.

  4. #4

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    Well, hello, Ern Dog! Yes, I am enjoying the 70's! They are replacing a pair of 50's which have served me well for 4 years in conjunction with a PSW 110. The 50's got to retire to a nice comfy spot in the side surround position in my 7.1 system. They in turn replaced a pair of 20's (see a trend here?) which I have toyed around with somehow combining with their brethren in the surround rear. Maybe pointing in a direction other than directly back at the main listening position for a diffusion effect. As you can see, I like to experiment! For completeness' sake, I am running a CS2 center channel. Now on to the task at hand...

    I am now running a BCI PL-200 sub and the preliminary verdict is good. As I have just started upgrading my system and haven't yet received my Carver amps from 2 seperate eBay sellers there is plenty of time yet for tweaking and experimentation! I just want to point out before I go on that I am wheelchair bound and to stay busy I will often do things just for the sake of doing them; sometimes without even a clear goal in mind. Thus the bi-amp portion of the program. Actually, the desire to bi-amp arose from the simple desire to provide more power to the 70's; power which, at 50w/ch, was fairly OK for the 50's but is noticeably leaving the 70's wanting. I should also point out that my system leans heavily toward Home Theater use rather than critical music listening so I'm not as strict about keeping the signal path as short and free of any sort of processing as possible. Case in point, part of my recent upgrade was the (re) acquisition of an Audio Control Phase Coupled Activator which I always regretted letting go of years ago. For those not in the know, the PCA was a component designed for use back in the day when some recordings rolled off the extreme low end frequencies, for example in many cassette tapes or vinyl records. Rather than just boosting the bass, it actually attempts to digitally "restores" "missing" bass information. Nostalgia aside, I was actually concerned that it wouldn't have much use in the digital age of Blu-Ray. I have to say that I was pleasantly relieved and pleased when I applied it to several media recordings, even Blu-Ray, and found that it gave a certain subtle but very effective je ne sais quoi of bass that is just short of magical. That's the long way of saying that I don't mind straying from the realm of "purity", although I respect and even consider myself a lapsed member of that group, for the sake of sheer auditory enjoyment...

    I'm sorry for the long post. I tend to ramble. I will try and fill in more of my "back story extended edition directors cut" in chunks spread over future posts and try and clearly delineate the meat of my questions in "theatrical cut" sections. Heh, heh...

    So! Back to specifics: Should I invest in a sound pressure meter in order to adjust my bi-amped levels? I hear that they aren't that expensive. Should I even concern myself with crossovers and not attempt to defeat/circumvent the internal crossovers of the 70's? Should I feel bad at cutting off the bass response of the 70's at, say, 80Hz? Have I missed anything? Are there any other tricks, tips or neat little experimental setups I could try?

    Last random thought concerning my setup: I am thinking of attaching the Left speaker leads to the "A" speaker posts and the Right leads to the "B" posts. This way I can easily check/measure each speaker on it's own to, say, see if one or the other is producing a standing wave? I already suspect the Left is a nasty dip at 50Hz based on the graph from the SMS-1. Since my room space is limited (reminds me. I have to get my room dimensions...) placement is restricted. Has anyone had any good results using "tube traps"? So many questions and ideas in my mind. It's good to be heavily in to audio again. Thanks for the warm welcome! :)

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    Thanks for the information, Outfitter03! :) I had a feeling that was the case (high range was the top set of posts) but it's always nice to know for sure!

    In other news, it came to me in a dream last night... I don't think I will be messing around with trying to second guess the internal crossover on the M70's. I imagine that Polk has gone to great lengths to insure that the crossover frequencies and slope are as perfectly matched as possible for the drivers in question. However, I am still curious if investing in a modest sound pressure meter would be helpful. I'm think that using the white noise test signal on my receiver (for testing levels on each channel) would be helpful in my endeavor. Again, any and all information (still even information about the internal crossovers) would be helpful and appreciated!

    Thanks again for the replies! :)

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    Firstly Welcome to Club Polk!

    SPL meter can be helpful, but honestly tweaking the SMS-1 manually for your Monitor 70's with the sub you have should be better than using the SPL meter since the SMS-1 takes measurements at your listening position and is much more accurate. In addition you can see the Frequency response graphed out and tweak peaks and valleys using the PEQ in the SMS-1. Its a pretty nifty tool IMHO.

    Can I ask what your pre-amp or your reciever is your planning on using?

    P.S. Love Carver gear - I run a AV-705x 5 channel and am getting a M1.0t refurbished for my LSi 15's
    P.P.S. Love the Monitors but dont get stuck on them, there are better vintage speakers out there if you know what to look for. I started with a set of Monitor 60's, CS1 and Monitor 40's about 2 years ago.
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    Hey, there End! Yeah, my plan with the meter was to gauge the output level of the high range compared to the low range drivers when bi-amping or would just eyeballing the levels controls on the amps be close enough?

    I actually saw your post right away because I came back to ask yet another question! That is, I know the 70's are rated for up to 250w/ch but what would the rating be for each range (the tweeter/mids vs. the woofers/low range) when bi-amping? I also might bridge the amps and then see how things sound without bi-amping.

    I'm using a Harman Kardon AVR-254 receiver. Let's see if we can find a linky-poo... Ah, here we go: http://www.harmankardon.com/EN-US/Pr...?PID=AVR%20254 It's rated at around 50w/ch or there abouts and I can really tell that the M70's are hungry for more. Like I said before, the receiver amp worked fine with my M50's but now, although I can get the system pretty close to "demo loud", it sounds strained. I especially noted it after I saw how a bridged AudioSource AMP-100 really opened up the center channel (CS2).

    And I think I'll be stuck on the 70's for a while since I just bought them! :P Heh, heh. Yeah, in the years to come I'm going to be always moving upward in quality so I'll be keeping an eye on prices for what may be new now but vintage later. :)

    Thanks again!

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    Quote Originally Posted by Cybershaman View Post
    And I think I'll be stuck on the 70's for a while since I just bought them! :P Heh, heh. Yeah, in the years to come I'm going to be always moving upward in quality so I'll be keeping an eye on prices for what may be new now but vintage later. :)
    Totally understand! They are good speakers regardless!

    Quote Originally Posted by Cybershaman View Post
    Hey, there End! Yeah, my plan with the meter was to gauge the output level of the high range compared to the low range drivers when bi-amping or would just eyeballing the levels controls on the amps be close enough?

    I actually saw your post right away because I came back to ask yet another question! That is, I know the 70's are rated for up to 250w/ch but what would the rating be for each range (the tweeter/mids vs. the woofers/low range) when bi-amping? I also might bridge the amps and then see how things sound without bi-amping.
    If it was me, I wouldnt get so hung up on the bi-amping part and what channels can handle what. I once ran each one of my Monitor 60's off 2 channels of the 5 channel Carver I had, and my amp is rated at 125x5 @ 8 ohms. I just used a Y adaptor on the pre-out, and left the trim pot (THX knob) all the way up on all the channels. The speakers sounded fine like that and I honestly couldnt tell much of a difference between that and just running them off one channel each.

    Your going to get a much better idea of how everything works if you just try to keep the setup simple.

    I would bridge the amps, one for each channel. If you wanted to bi-wire each speaker to the amp you could, thats what I do with my LSi 15's. The Manual tweaking in the SMS-1 will show you realtime response for the frequencies for your speakers if you use the fixed 80hz outputs for your fronts (which I would in your case).

    You should read the SMS-1 manual if you havent yet. It honestly will help you get an idea of how to set things up.

    My suggestion, go from the pre-outs on the HK 254 (assuming it has em) to the SMS-1. From the SMS-1 use a LFE out to your sub (or subs), and connect the RCA for your Left channel to one of the bridged Carvers, and the RCA for your Right channel to the other bridged Carver. Then start tweaking things with the SMS-1 mic in the Manual mode (read up on it in the manual).

    I would suggest looking at getting some mid-grade speaker wire and rca connectors. Some brands that come to mind instantly are: Signal Cable, Blue Jeans Cable, Audioquest. There are others but these are a good starting point price wise.
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    The Shadow knows! Heh. Sorry. Feeling a little slap happy tonight for some reason...

    Yes! You have pretty much summed up how things will probably turn out! Again, due to my disability I'm home the vast majority of my time and I need little projects or experiments to perform so I probably would be doing most of these things simply to edify myself.

    And I'm currently using, oh, about 10-12 foot runs of some 14g RCA wire up front. Yep, I actually had bi-wired the 50's so I'm all ready to experiment with the 70's. And I started to order good connects for the new components but since I still haven't decided where everything is going I stopped in order to wait for my components to "settle in".

    The SMS-1 has been indispensable in this setup. I can't recommend it enough if you can afford it. The only other product that comes close to it is the old Audio Control Richter Scale which it seems you can still find from time to time on eBay for around 200-250 bucks. (except for that one crazy guy running one right now for dang near a grand!). Search as I did, I couldn't find any other home solutions for sub equalization/standing wave problems.

    Oh, here's a little side-note: during all of this, I wish I could test my old DCM Timeframe 700's with my current system. I sold them along with the rest of my stuff ages ago to help fund an adventure to Japan. I just LOVED those speakers! People always commented on the shape (they looked flat and people thought they were planars or electrostatics but they were actually 3-way transmission line) and were amazed at the bass response from an 8 inch woofer. I was lucky to have heard them since they were made right here in town. (It looks like they moved) Oh, well. I guess these stories are a dime a dozen around here. You know, "the one that got away!" Heh, heh. To quote Scotty toasting to old starships with Cpt. Picard on the holodeck: "Here's to old girlfriends!" <quafe...gulp!>

    (darn. now they know i'm a big old nerd.)

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    Update on the continuing saga of Cyber's great bi-amp quest...

    SO! I just found out that one of the two Carver amps I got is the purely 15 model and not the 15cb bridgeable. (gotta REALLY pay attention to those photos on eBay) And after a bit o' research I saw that people were saying to NOT manually bridge the amp (with an inverted RCA connection to the left input and then connecting your speaker wires to both positive speaker terminals) or else it would melt down. I still find it hard to believe since both amps are essentially identical and with the size of the circuitry components inside being super beefy as they are. But, hey, better safe than sorry, right? So, bi-amp it is...

    I am still curious what the internal (passive?) crossover specs are on the Monitor 70's (should I just call the good folks at Polk?) because I want to roll off the frequencies via an external crossover before sending the signals on to the amps/speakers. From what I can tell, it sounds to me like I'm trying to do an "active crossover" configuration but isn't that where you would basically connect the amps right to the drivers and bypass the internal crossovers all together? So I'm left with the feeling that doing what I want to do, although looking cool on paper, really wont make a heck of a difference. A nice handy wiring diagram of the M70's would be great but, again, should I just contact Polk?

    As far as trim pots go, EndersShadow, I really am hoping that I can just max out the ones on the amps. But if my experience with my center channel amp is any indication, I might have to tone down the input a bit even with the gain set to 0 db in the receiver's speaker setup section.

    I think that's it for now. Love all the banter. It's been so long since I've been heavily involved in HiFi. Much too long... ;)

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    If you truly want to bi-amp them, then your going to want to pull the crossovers regardless and use a EQ between your HK and the amps. There is something out there that connects to the computer and lets you do that, I am just totally blanking the name of it.

    You can get them in a wide assortment of flavors, such as 2 in 4 out, 2 in 6 out, etc. You use your computer to program in the crossover and curves and it takes the signal and applies those filters to the appropriately assigned channels.

    I was hoping by sleeping I would remember it but I am still blanking what the product is called.... Its gonna piss me off till I figure it out lol....

    It would be lots more fun for you since your a tweaker as well.

    P.S. It would be used totally in place of the SMS-1 I believe.
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  12. #12

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    Now we're getting somewhere! Yeah, I am having this weird feeling that to do the level of tweaking I'm thinking about would involved ripping out the crossover all together. Am I treading on dangerous ground by accidentally implying that the bi-amp/wire option on the M70's is really just bi-wire (when you get right down to it). Of course I'll know right away when I cut out the "hi amp" and loose the tweeters/mids (or not)...

    Yeah, a frequency response graph would be super cool. I would still use the SMS-1 for the sub (it really did make that much of a difference. Even when just using the LFE out on the receiver.) but knowing visually what's going on with "operation bi-amp" would make things much easier.

    I need crossover specs/diagrams! Love me some diagrams... :P

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    Welcome to Club Polk!

    According to Polk documents: The M-70s have a Cascade Tapered Array (2-1/2-way) design. Both drivers play bass frequencies but only one driver (the upper one) plays upper-midrange frequencies. This method provides maximum bass output along with precise imaging and detailed midrange response. The cascade crossover operates on a slope to 2.6 Khz--see below.

    Manufacturers Details

    Drivers
    Subwoofer 2 ? 6-1/2″ Diameter (16.51cm) Dynamic Balance Bi-laminate composite cone drivers, magnetically shielded
    Mid/Woofer 2 ? 6-1/2″ Diameter (16.51cm) Dynamic Balance Bi-laminate composite cone drivers, magnetically shielded
    Tweeter 1 ? 1″ Diameter (2.54cm) Dynamic Balance Silk/polymer composite dome, magnetically shielded

    Electrical
    Overall Frequency Response 30Hz ? 25kHz, Lower -3dB Limit 40Hz, Upper -3dB Limit 24kHz
    Nominal Impedance 8 ohms
    Recommended Amplifier Power 20 ? 275 w/channel
    Efficiency 90 dB
    Crossover 2.6kHz and 2.6kHz cascade tapered 2nd order
    Inputs Dual (bi-amp) 5 way binding posts

    I run a pair in my HT system. As far as my system the LFE crossover that works best is a 60 hz for R/C/L. Takes some strain off the amps but still allows the M-70s to put out the low end they "should". Setting the CS2 to that some cut off also allows it a slightly "fuller" sound!

    M-70s really don't need to be bi-amped if you have a nice 200 watt x 2 @ 8 ohm power amp. That will feed them fine!

    cnh
    Last edited by cnh; 10-12-2012 at 12:25 PM.
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    cnh for the win! And the verdict is: 2.6k crossover!

    So. In my quest to do the hardest thing possible for little or no gain, I'm going to program the crossover in one of my Audio Control components (Phase Coupled Activator or Richter Scale. Not sure. Oh, yeah. I have a Richter Scale, too, because, wanting to send as much bass to the M70's as possible, I'm going to have to take care of a nasty standing wave...) and run the split to the two amps. Then take the crossover out of the equation and see if there's a difference.

    Sound like a lot of work? Yes. Will it keep me busy? Yes. And we will learn things too, boys and girls! And knowing is half the battle... Heh...

    Any other bi-amp tips/tricks/caveats still appreciated! I'll come back with a (much too) lengthy report in a couple of weeks, probably... ;)

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    Here's what I mean about "building my own crossover":

    Name:  crossover module.png
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    Sound like fun?

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    Doesnt sound like fun to me, but to each his own. Enjoy the journey and the tunes at the end of it.

    HA!!!!! FOUND IT!!!!

    Its called a Mini DSP. Check them out they sound RIGHT up your alley.

    http://www.minidsp.com/applications/digital-crossovers

    They can be setup and paired with REW to give you some STELLAR sound for not a lot of cash......

    Only other suggestion I have is that if you pull the crossovers from the Monitor 70's do it in a way you can put them back in with little to no drama in case you ever want to sell them.

    Also contact VR3 on this forum as he should be able to get you some very nice faceplates and binding posts to replace the stock ones that should drop right in..... Like this: http://www.polkaudio.com/forums/show...=1#post1810763
    Last edited by EndersShadow; 10-12-2012 at 01:32 PM.
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    Wow, EndersShadow. You get a win too! I think that's EXACTLY the thing I'm looking for! And having a place to get new plates...ohhohohoho... That's awesome...

    I just want to thank everyone so much. You've made a bored disabled guy very happy. It was fun racking the brains with you all.

    I'm not sure when I'll get to the heavy duty portion of my project but I'll be sure to come back and post results. Very positive impression of this community. You guys rock! :)

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    Quote Originally Posted by Cybershaman View Post
    Wow, EndersShadow. You get a win too! I think that's EXACTLY the thing I'm looking for! And having a place to get new plates...ohhohohoho... That's awesome...

    I just want to thank everyone so much. You've made a bored disabled guy very happy. It was fun racking the brains with you all.

    I'm not sure when I'll get to the heavy duty portion of my project but I'll be sure to come back and post results. Very positive impression of this community. You guys rock! :)
    Glad to be of assistance. I knew that product was probably exactly what you were looking for and the plates would just cap it all off for ya . Looking forward to seeing how things progress. I have been tempted to implement them into my LSi 15's instead of replacing the crossover capacitors and resistors, but am a bit of a scaredy cat

    P.S. just cause this question is answered doesnt mean you cant stick around and BS with us or contribute your thoughts about things. . Everyone has something to offer
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    Oh, I'll be sticking around... Looks like a fun bunch! Talk to you soon! :)

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    ^spammer shed864 reported
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    Quote Originally Posted by Cybershaman View Post
    My thought is that I might experiment with applying a low-pass filter before sending the signal on to the amps for the woofers. I might even do the same, except in reverse with a high-pass filter, to the mid-range/tweeters. I wonder if doing so might take some unnecessary load off of the equipment or will this make any difference at all?
    Forgive me for intruding on Cybershaman's thread here, but I've been wondering about this as well. I have experimented with a few bi-amp setups (though I recently learned I my setups were passive, not active). I'm interested now in attempting more of an active bi-amp setup - if for no other reason than curiosity.

    What would be the difference between using an active crosssover (mini DSP or similar) and adding low/high pass filters between my preamp and power amp(s), as stated above by Cybershaman? I've read that the passive crossovers are inefficient - i.e. they substantially reduce the amount of current sent to the drivers?

    Let's say I have 2-way, bi-ampable speakers with a crossover at X Hz. Could I a split my left and right preamp outputs and add a low pass at say, (X+300)Hz and a high pass at say, (X-300)Hz to each side, while leaving the speakers' internal crossovers intact? This would significantly reduce the frequency bandwidth seen by the individual amplifier channels, correct? It seems to me this would achieve a similar effect without the need to disassemble my speakers, unless I'm underestimating the effect of the inefficient passive crossovers. Not trying to argue one way or the other, just curious.

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    You see, that's why I was curious about the internal crossover level because I didn't want to cut anything off. Without removing the crossover in each speaker your signal is going to go through that crossover before finally reaching the speakers. So, yeah, knowing what point that internal crossover is (2.6khz in this case) I could construct an external (active) crossover before my amps in the hopes that something good will happen.

    From what I'm hearing, the difference is slight to nothing at all, but I've got something to play with now and it's going to be my little tinker project for some time I think.

    Check out this cool bi-amp article I found: http://sound.westhost.com/bi-amp.htm

    (did I get that right guys? heh, heh...) ;)

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    Good read, thanks for sharing. One recurring theme is the fact that passive crossovers suffer from some inherent weaknesses & compromises that can be overcome by active crossovers. Which kind of answers my question - the most substantial performance gains will come by removing the passive crossovers from the speakers.

    Having said that, if I'm not ready to commit to speaker modification and/or active crossover setup, I could potentially avoid some of the effects of those weaknesses by going overkill on amplifier power rating. Or so it seems. Do you think the speaker manufacturers take that into account when they specify suitable input power ranges? i.e. if my manual says 10~250 watts, is 250 watts their estimate of what is needed to prevent clipping in extreme cases, or is it safe to assume more is still better? I mean, I could be talked into buying a couple of monster monoblocks. Just sayin'

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    I want to clear something up. Earlier, I think I alluded that the passive crossover built into the M70's simply split the high and low frequencies to each of the drivers. If that were true than you wouldn't really be bi-amping at all if you you used the separate binding posts. It would really just be bi-wiring and nothing more. However, in lieu of a wiring diagram, I physically pulled the crossover (for those not in the know, the crossover is attached directly to the wiring post plate on the back of the speaker) on one of my Monitor 20's and did a visual inspection and circuit trace.

    Let it be known that each driver or range of drivers gets their own separate crossover circuit. I knew this had to be true but when I made that earlier statement I had just read some posts by others who mentioned that sometimes, due to demand, speaker companies will simply add a second set of binding posts so as to make it appear that their speakers are bi-ampable. This is NOT the case with Polk!

    The Monitor series may be Polk's "budget" line but they are not a hacked together, cheaply made sub-par product with fake features. They are a quality made product through and through.

    I just wanted to make it clear that I had spoke in error without thinking first.

    Now...back to your regularly scheduled program... ;)

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    I just CAN NOT stay away! (stupid stream of consciousness thinking...)

    Other than the fact that I meant to say Montior 30's instead of 20's in my previous post, I have been doing further reading on crossovers and bi-amplification and found a very interesting article for anyone who is pursuing a goal similar to mine. It's located here: http://www.audiocontrol.com/t35/c5356/3436/FAQ.html Click on the "View Tech Note 104 - Crossovers and Biamplification" link to take you to the PDF file.

    I'm now VERY excited to try and mess around with the crossover on my Polks. However, it's going to be a while before I get to that level because I want to be sure all of the knowledge and equipment I need is in place. I plan on getting the DSP device that EndersShadow recommeded (http://www.minidsp.com/applications/digital-crossovers and then reformatting my old laptop to run the interface. (did I mention I'm into computers too? My screen name should have given it away...)

    I could go on and on but I just wanted to post that link in order to save others some time.

    Again, I just want to say that I am doing this to really just learn about audio theory. I don't have any pipe dreams about my system suddenly opening up and becoming more than it is. I'm just a bored disabled guy with a lot of time on his hands and surrounded by a good amount of computer and audio equipment. Just for fun, I'll post a pic of my last computer build (I pretentiously named it "The Krell") from Jan. 2009. Once my current audio upgrade project settles down a bit, I am going to start planning/building my new PC. Here's a funny parallel about my PC build compared to what I am trying to do with my speakers: the water cooling was WAY overkill and while it allowed me to overclock my processor significantly, it was a P.I.T.A. and I wouldn't recommend anybody doing it. But I learned a lot and my brain was heartily entertained...

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    OK. That's it. I'm done for a while. I PROMISE that I will attempt to post in some other threads. Any good ones going on right now? ;)

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    It looks like my crossover question has been around for quite some time. The next to the last post by MentalNomad in this thread sheds a little bit more light on the issue with and explanation of what a "2 1/2 way design" means for

    http://www.polkaudio.com/forums/show...er-frequencies

    Quote Originally Posted by MentalNomad View Post
    I've seen the crossover diagram on these (and I own them), I'll see if I can turn that up again... but basically, it's a 2 1/2 - way design because:

    The first split in the crossover has a traditional 2-way design; highs pass to the tweeter, and lows pass to the bass side.

    On the bass side, the full signal goes through two woofers (these produce all bass and mids), and the signal goes through a low-pass filter and into the last two woofers (so these two produce bass only.)

    So all four woofer produce very low bass, but only two of them produce mids.

    Hence 2 1/2 way:
    one way: tweeters doing highs
    second way: two woofers doing lows
    last bit: two more woofers doing half of the lows (the lower lows)
    Again, a diagram would be infinitely helpful but perhaps this is proprietary information that Polk would be hesitant to give out?

    Back to the bowels of the Internet...
    Last edited by Cybershaman; 10-13-2012 at 10:26 PM.

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    Who would have thunk that the forum itself would have had the answers to my questions. Then again, if I hadn't felt compelled to ask you guys, I wouldn't have met such cool people and been encouraged to hang out here! Please Note: I'm going to be posting little bits here as I find them. I've already found a handful of things from various threads and I just want to post them here so that they'll all be in one place in order to help the next person who comes along with the same or similar questions...

    First up (drum roll please) a diagram!!!

    http://www.polkaudio.com/forums/show...II#post1813813

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    I've got some other links with information and photos to post so don't feel like you have to respond as I post them. Again: I just thought it would save someone in the future some time if I culled and posted any related information here.

    It's late and I'm getting tired so I'll organize and post some more tomorrow. 'Nite all! Thanks again for the warm welcome and help. I think I'm going to like it here... :)

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    Here is an actual picture of the crossover from this thread: http://www.polkaudio.com/forums/show...-noobs-like-me There are also a couple of links from Esreuter detailing some crossover projects which I found to be very insightful and inspiring!

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    Ok, guys (and gals?)... Last night as I drifted off to sleep I had the most amazing epiphany... It woke me up enough that I almost came out, fired up the computer and posted my revelation. But I thought that a night of sleeping on it would coalesce my thoughts a bit more and hopefully help not make me sound like a raving lunatic. So...while related to what this thread is about I think that it is different enough to warrant its own. To this end, I will try and sum things up here first...

    If, for whatever reason, you are interested in employing an external active crossover when bi-amping your Monitor 70 speakers, you will need to have it set at 2600 KHz. I don't think the roll off would matter too awful much since the internal crossover will take care of it anyway but it's something to keep in mind if you are experimenting.

    As far as the amplifier power required in this setup (with or without an active crossover) since you are essentially running just the tweeter (via the top binding posts on the back of your speakers) for the highs, you aren't going to need that much power. While the speaker in its entirety is rated at 20-275 watts per channel, I'm not really sure what the "exact" rating would be for each individual driver or range of drivers. For the sake of argument, I would think that an amp rated at 50 watts per channel would be plenty more than sufficient for the tweeters. As for the mids/woofers, a fairly large amp would be good, say, oh 200 or 250 watts, guys?

    And just to super clarify how the M70's are set up, I think an easy way to look at it would be to imagine a Monitor 40 speaker sitting on top of another M40 that has had the tweeter removed. The top M40 would run full range will the bottom, tweeterless M40 would be playing fairly low frequencies. While we've determined that the tweeter crossover point is 2600 KHz, we haven't yet determined what the low frequency split point is. However, I think we should be able to figure that out from the handy diagram that mrviper100 has so kindly provided to us. If/when I find that out, I'll post the number here.

    In the mean time, I am off to create a new thread to present what I hope to be a very scintillating idea which is in part built upon everything we've discussed here. I just wanted to thank everyone one more time for all of the help. It's been greatly appreciated and has helped me to feel a level of excitement that I haven't felt in quite some time.

    Stay tuned! :)

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