Internal schematic and crossover data for Monitor 70 Series II?

jviss

I originally posted this on AudioKarma, and it was suggested I try here.


Sincerest apologies if this has been answered, or is posted elsewhere, but I searched and couldn't find the answer.

I just last week received my new Polk Monitor 70 Series II's which I'm using as fronts for my home theater, driven by a Yamaha RX-A700 receiver.

I've removed the jumpers on the speakers, run two cables, and configured the receiver bi-amped.

It occurs to me I don't know exactly what's going on inside the cabinet. The speaker docs are poor, and illustrates bi-wiring with the jumpers out, but doesn't mention bi-amping.

The docs and other literature refer to a "cascade tapered array" crossover configuration, but gives no details.

I'd really like to know what's going on here. Does anyone have a schematic, and frequency response plots for the crossover network?

Any information is appreciated.

Thanks,

jv

Drenis

You can read up on the cascade array here: http://www.polkaudio.com/education/tech_article.php?id=23

More details about your speakers here: http://www.polkaudio.com/homeaudio/products/recent/monitor70/

Can;t help with the schematic though

tonyb

jviss wrote: »

I've removed the jumpers on the speakers, run two cables, and configured the receiver bi-amped.

It occurs to me I don't know exactly what's going on inside the cabinet. The speaker docs are poor, and illustrates bi-wiring with the jumpers out, but doesn't mention bi-amping.

jv

Why do you need to know whats going on inside the cabinet, has nothing to do with bi-amping from a receiver. You remove the jumpers on the speakers, one set of cables goes from the receivers front left and right to one set of speaker posts, the other channel you use to bi-amp on the receiver goes to the other set of posts....your done. Though straight up, your receiver is more than enough to drive M70's. Does something not sound right ?

Hopefully someone will chime in with the info you require.

jviss

Thanks very much, I've seen those already (by the way, there's something weird about the Polk page encoding such that I get lots of garbage characters on my screen. I'm using a Mac. I almost never see this, but I have it in spades on the Polk website. What character encoding are they using???)

As I said, I really want technical details, without having to tear my speakers apart to find out. It seems odd to me that it's so difficult to get basic technical info on these. I've scoured the web and come up with nothing.

Drenis

You could always take yours apart to find that information out on your own? Manufacturers hardly if ever post those kinds of details.

heiney9

A request to customer service might get you a schematic. I just contacted someone for a schematic for a pair of RTi38's and they sent it right away.

H9

jviss

tonyb wrote: »

Why do you need to know whats going on inside the cabinet, has nothing to do with bi-amping from a receiver. You remove the jumpers on the speakers, one set of cables goes from the receivers front left and right to one set of speaker posts, the other channel you use to bi-amp on the receiver goes to the other set of posts....your done. Though straight up, your receiver is more than enough to drive M70's. Does something not sound right ?

Hopefully someone will chime in with the info you require.

Well, I want to know, because I want to know! I posit that regardless of all of the subjective comments about the sound of these speakers in standard config, bi-wired, or bi-amped, no one really knows what the topology is for any of these configs, unless they work for Polk or have taken the speakers apart.

I would like to know so that I can make a rational decision regarding the trade-offs involved in the decision to bi-amp. I should say now that I do not think bi-wiring is ever worth it, it doesn't make any sense from an engineering perspective. However, bi-amping does make theoretical sense, in my opinion.

I just got off the phone with Polk support. I was told the top set of terminals goes to the tweeter; there is an intervening high-pass filter. The bottom pair of terminals goes to the drivers. For these there is a crossover network that sends the low frequencies to the bottom three speakers, and the mid frequencies to the topmost driver.

I asked for frequency response curves for these and he said he'd look for them, and email them if he can find any.

So, that's progress, I guess.

Likewise, there's little information available from Yamaha about what they are actually doing when you select bi-amping.

jviss

Drenis wrote: »

You could always take yours apart to find that information out on your own?

Would void the 5 year warranty.

Drenis wrote: »

Manufacturers hardly if ever post those kinds of details.

I disagree with that.

tonyb

A little research can yield some results if you want to know about trade offs. In audio though, keep in mind that most things are subjective and an engineering standpoint only goes so far.
Alot is dependant on the gear used, the quality of said gear, and the intented purpose of use. Bi-amping from a receiver is still using the same power supply divided up by x amount of channels. In most case, not all, the more channels used, the less power each channel has. Power supplies in receivers are not of the best quality to begin with, which is why when bi-amping most use external amplifiers, and even external crossovers. Also one must be hip to ones speakers ability to portray small details/changes in sound. The better the speaker, the more those smaller subleties from different gear,cables, become audible. The M70's while good speakers are on the entry level side, so personally I wouldn't expect to hear things I would from say a B&W 802, or a Martin logan Prodigy,as just an example. When all is said and done though, in this hobby, your ears tell you more than any schematic can. Unless your the type to mod everything, a schematic tells you little on how a speaker will/should sound. I've heard plenty that sounde better than they had a right to considering cheap parts used and poor designs. The ears are the best judge because thats all that matters. If it sounds good to you, who cares if there's mega bucks worth of parts in there or 2 squirrels.

You can maybe look up some old reviews from HT magazine, they usually run response curves in speaker reviews though I don't know if they have done the M70's.

Also, when you select bi-amp on a receiver, your not changing anything in the speaker, it has to do with what the receiver is doing. Which I explained above, but again, your just using 2 more channels of power from the receiver to throw at the speaker which is also somewhat deceptive. Also consider the fact that the top portion of the M70's uses very little power, as for most other speakers in general. Hopefully Polk will come threw for ya on the response curves, but just out of curiousity, say you get them, how does that info change anything ? Still fuzzy on what your trying to accomplish. Anyway, good luck to you.

jviss

Thanks, Tony. I appreciate your thoughtful response. Just to make sure I hear you correctly, allow me to comment on this part of your response:

tonyb wrote: »

Also, when you select bi-amp on a receiver, your not changing anything in the speaker, it has to do with what the receiver is doing.

In order to enable bi-amping, I'm not only selecting a configuration on the receiver, I'm also electrically separating the top and bottom of the speaker cabinet, by removing the jumpers; don't you agree?

I had been under the impression that to derive the full benefit of bi-amping, one would have to remove the passive crossover networks completely, and drive the speakers with separate power amps, or power amp channels, and apply any filtering in the pre-amp stage, i.e., an active crossover. So one might wonder what follows the terminals on a speaker cabinet when the jumpers are removed; and, whether crossover adjustments, per se, are available on the receiver. On Yamaha receivers does YPAO adjust crossover frequency when bi-amped is selected? I sort of doubt it, but who knows?

TNHNDYMAN

Maybe you should read your Yamaha manual again and see if it gives you an answer to what YPAO does or does not do when in various surround modes, 2ch, 2ch direct, pure,ect.... If not in the manual then probably find a good forum over at AVS for Yamaha AVR's in general and I'm sure someone has had the same ? before probably been answered already and you could search there. Hoping Polk Customer Service comes thru and finds you a schematic. They have been great to deal with in the past for myself and many others on here. If not then I really don't see the problem w/ removing a driver and looking inside the cabinet. No one is suggesting you remove cross braces, cut thru wiring and desolder anything. I'm not sure how you would void a warranty by removing 4 screws and shining a flashlight inside or trying to take a few pics on macro mode w/ a decent camera. If that gives you great concern and trouble then give me a couple days and I'll pull the drivers out of my Monitor 70's and try to find some values on the crossover board and or take a few pics. I've already had my tweeters out and replaced from Polk and since I bought them used I have no warranty to lose sleep over. Good luck.

tonyb

jviss wrote: »

In order to enable bi-amping, I'm not only selecting a configuration on the receiver, I'm also electrically separating the top and bottom of the speaker cabinet, by removing the jumpers; don't you agree?

I had been under the impression that to derive the full benefit of bi-amping, one would have to remove the passive crossover networks completely, and drive the speakers with separate power amps, or power amp channels, and apply any filtering in the pre-amp stage, i.e., an active crossover. So one might wonder what follows the terminals on a speaker cabinet when the jumpers are removed; and, whether crossover adjustments, per se, are available on the receiver. On Yamaha receivers does YPAO adjust crossover frequency when bi-amped is selected? I sort of doubt it, but who knows?

The jumpers are sending the signal from the bottom portion of the speaker to the top, think of it as a bridge. When you remove the jumpers, you then have to get a signal to both sets of posts either by bi-wire, or bi-amp. Either way, both sets of posts have to have power going to them. The jumper enables that. All your really changing in the speaker is how it is to get the signal, by one set of posts, or by 2.

Your impressions of a true bi-amp configuration are correct, technically. Nobody wants to go around removing passive crossovers from speakers, especially those on the entry level side. Though I guess if one wanted to play Frankenstein and had a good sense of doing things themselves, you could just use the cabinet and build your speaker to your likings.
A receiver has crossover adjustments, all modern ones anyway worth their salt. Some have set adjustments so if you choose your speakers to be set to large, a full signal is sent, small....maybe have a fixed 80 hz crossover, usually thats on older receivers though. Differs a tad between stereo receivers and AVR's, but most modern receivers have a fairly good level of adjustment.

The bi-amp feature should have nothing to do with the crossover settings. I say should ......because every receiver maker does things differently and at different levels within a line of receivers. I know, can get confusing at times but it is what it is.

Whats behind the speaker post matters not, it all goes where it's suppose to go regardless if you bi-amp, or use the jumpers and a single set of cables. The only time it won't, is if you remove the jumpers and only use one set of posts. Both sets of posts have to get a signal, always, for the speaker to work properly.

Think of the speakers internal crossover, or even the one in a receiver, as a traffic cop, Telling what freq. to go where. One of my own personal points of contention is the misuse of the word "bi-amp" today. Though old school, your idea of what it should be is more so correct. You can bi-amp per say in a few different ways that aren't as old school technically correct, like using seperate amps for both top and bottom portions of the speaker, which is the way most go.....and honestly, should be more than enough for most audio nuts out there or for just about any speaker out there, but like all things in this audio hobby, there's more than one way to skin that cat.

Just some food for thought, don't get so caught up in the little stuff about this hobby. Most join because they love music, and the reproduction of that music in a way that pleases them. Some are perfectly happy with a Bose wave radio, others have to have the latest and greatest regardless, and still the majority probably fall somewhere inbetween. If you get too wrapped up in the engineering aspect, you forget about just enjoying the music. Not saying that the technicals isn't important, just don't let it get in the way is all I'm saying.

Sorry for the long post, and I want to welcome you and invite you to stick around. We only bite on every other friday and 2nd Monday of the month. We have all sorts of great members with experience at all levels of audio. Plus we have fun, so stick around, get to know a few people, enjoy the forum.

Geoff4rfc

tonyb wrote: »

Sorry for the long post, and I want to welcome you and invite you to stick around. We only bite on every other friday and 2nd Monday of the month. We have all sorts of great members with experience at all levels of audio. Plus we have fun, so stick around, get to know a few people, enjoy the forum.

That's a load of crap Tony, you bite all the time

Yeah, welcome aboard jviss, I've learned a lot from this forum. Being recently retired from roadracing, I'm really very brand new into this rabbit hole mess and only know a fraction of what I hope to learn.

See you around.

Drenis

jviss wrote: »

Would void the 5 year warranty.


I disagree with that.

No.

Show me five speaker manufacturers that have the internal schematics of their speakers posted. Pictures or diagrams will suffice.

Edit: Welcome to CP.

jviss

Thanks for the welcomes, and the info/advice.

mrviper100

Here is a schematic I put together for the Monitor 70's, but should be the same for the Series II's.

MindlessCorpse

Thanks to mrviper100 for the schematic, as I own two of the Monitor 70 series II also (used for rear channel surrounds)
To Tonyb; in regards to jviss wanting to 'know' what he is working with, I understand this, and am the same. With the thoughts on bi-amping, I also understand the questions on crossover setpoints, both inside the cabinet and at the receiver and why asked... again, I ask the same questions.
and ... wasnt meaning to bump this thread, I was in search of the same information on the TSx550t speakers and will start a thread on it.

tonyb

And to my point, that schematic changes nothing as to hooking up cables, bi-wire or bi-amp. You simply remove the jumpers if you want to bi-wire or bi-amp, single cable runs ....leave the jumpers in place or use better ones. That's about as complicated as it needs be. There's no funky stuff going on. Unless your building your own speakers, or repairing some, don't waste time on useless info otherwise this whole hobby will drive you into the Looney bin.