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Polk Monitor 40 Series II Review (Speaker)

richard12511

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If so many of the sub $700 speakers have such thin wiring from the crossover to the speakers, why do some people still spend so much money on speaker cables? If you got a pair of $200 cables running to $700 speakers that have $.96 worth of wire on the inside what's the gain from the cables? I think more consumers need to see what's inside their speakers before purchase or the front falls off.

That's because internal wiring is not visible. Similar story for the wiring in the walls. As long as wire is hidden, it doesn't affect sound quality. This is known ;).
 

MrPeabody

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ON THE ONE HAND ...

From the standpoint of distortion this speaker is better than most speakers that cost a lot more. If you can overlook the directivity issue (I could), the elevated treble response can be easily corrected using a pair of resistors, one shunting the tweeter and the other in series with the parallel arrangement of tweeter+resistor, with the two resistor values chosen to simultaneously satisfy two needs (a) the impedance of the padder tweeter network to be the same at the crossover point as the impedance of the tweeter alone (b) nominal tweeter sensitivity to be lowered by about 3 dB. This will fix the biggest problem with this inexpensive speaker, at very little cost and very little effort. There will still be the directivity issue, and there is also comb filtering from 1 kHz to the crossover point, but the on-axis response and the distortion will be better than what we see with most speakers costing several times more.

ON THE OTHER HAND...

The designers of this speakers used the MTM configuration for reasons that are likely only for showroom appeal, unless they did it to get away with 1st-order acoustic crossover slopes and the accompanying tilt of the main lobe in the vertical polar plane. I have pointed this out on this forum so many times that I'm blue in the face from it, but so far as I know, no one has noticed. The thing is this: In order not to end up with an undesirable comb-filtering affect in the upper octave of the woofer range in a 2-way MTM speak, for vertically off-axis listening positions that aren't especially far from the horizontal, it is necessary to use very small mid-woofers so that their centers will be vertically separated by not much more than half of a wavelength at the crossover frequency. The only case where there is any compelling reason to use MTM is when trying to correct the tilting of the main lobe, and even in this case the technique is little more than a kludge. The MTM configuration can have an advantage, but it is never a great advantage, and in order to achieve the small advantage that it offers, the two drivers have to be very small midranges with their centers close to each other. The comb filtering is a consequence of destructive interference between the two small woofers, at wavelengths (with this speaker) for the frequency band from about 1 kHz on up to the crossover point. At this short wavelength, starting from a little more than 1 foot and shortening from there (or about 1.3 meter), the difference in the two distances, from the listening position (above or below the horizontal) to one of the woofers and from the listening position to the other woofer, will be a sufficiently great fraction of the wavelength for destructive interference to produce the comb filtering effect. I absolutely would not design or build a two-way MTM speaker. For a three way speaker where the crossover point from the woofer to the midrange will be high enough to permit use of a smaller-than-typical midrange, I might consider using MTM for the midrange and tweeter, but I wouldn't be strongly inclined to do it even then. The downsides to this arrangement are perfectly real, and the advantages are minimal except for when the crossover isn't phase coherent (acoustically) and the main lobe is consequently tilted up or down. And even if, for whatever inexplicable reason, I wanted to use a simple asymmetric crossover that resulted in a tilted main lobe, I would still prefer to use some other method to correct the tilting of the lobe, rather than try to cover it up with MTM.

I expect this would have been a better speaker if both woofers were located under the tweeter. Certainly it would be if the crossover took the so-called 2.5-way approach where the lower woofer rolls off at low frequency a couple of octaves or so below the crossover point.

If you look at the multicolored directivity plots for this speaker, especially the vertical one, you can easily see the comb filtering from about 1 kHz on up to about 3 kHz and even slightly higher. In theory this is expected to be evident if the listening position is vertically off-axis, away from the horizontal, in the vertical plot. What we actually see, however, is that this effect is evident even for listening position located 0 degrees vertically off axis. I would have assumed that 0 degrees would be equidistant from both woofers, i.e., on the horizontal plane equidistant from both woofers. If the 0-degree point is equidistant from both woofers, there should be no comb filtering effect, but I see it there very plainly, and I recall seeing it in another speaker that I think was measured by Amir. This is weird and difficult to explain. I would have guessed that the 0-degree plane was not equidistant from both woofers, however if this were the explanation, there would still be some vertical angle equidistant from both drivers such that the comb filtering effect wouldn't be evident. I refrained from pointing this out the previous time, but now that I've seen it twice, I couldn't help but mention it. The only thing that comes to mind, that might explain this, is that there is a strong reflection coming from somewhere, presumably close to the mic. And the comb filtering effect shouldn't be evident at all in the horizontal directivity graph unless the mic is closer to one of the woofers than to the other one. But the effect is clearly evident in this graph, and I'm only able to think of two reasons why it would be. Either the mic is a lot closer to one of the woofers than to the to the other one, or else there is a strong reflection influencing the measurement. In order for the reflection to have this much effect, it would have to be coming from a surface very close to the mic, and yet far enough above or below the mic such that this surface is quite a bit closer to one woofer than the other one. I wouldn't completely exclude the possibility that it is reflection from the floor or ceiling, notwithstanding that Klippel is supposed to mathematically remove the floor and ceiling reflections from the measurements. Regardless, the signature of comb filtering between the two woofers is very definitely evident in the those two plots, at every horizontal off-axis angle and at every vertical off-axis angle.
 

TeeMann

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expect this would have been a better speaker if both woofers were located under the tweeter. Certainly it would be if the crossover took the so-called 2.5-way approach where the lower woofer rolls off at low frequency a couple of octaves or so below the crossover point.

Actually, Polk did revise this model to TWW in the 45B. Also, keep in mind that the Monitor line is well over 15 years old at this point.

Link to Monitor 45B: https://www.newegg.com/polk-audio-monitor-series-new-monitor-45b/p/N82E16882290269
 

Francis Vaughan

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This speaker is really odd.
On one hand, building it to this price is little short of miraculous.
But on the other, for no additional effort or cost it could have been so much better.

As noted above by others.
Built it as a 2.5, not an MTM. (OK this does add crossover complexity.)
Add a waveguide to fix the top end. That just involves redesigning the existing plate.
Fix the FR tilt.

Do this and the speaker could be a giant killer.

It starts to get to the point where speakers should have a switch on the back that engages showroom mode - just like TVs do.
 

beagleman

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This speaker is really odd.
On one hand, building it to this price is little short of miraculous.
But on the other, for no additional effort or cost it could have been so much better.

As noted above by others.
Built it as a 2.5, not an MTM. (OK this does add crossover complexity.)
Add a waveguide to fix the top end. That just involves redesigning the existing plate.
Fix the FR tilt.

Do this and the speaker could be a giant killer.

It starts to get to the point where speakers should have a switch on the back that engages showroom mode - just like TVs do.


I seriously wonder if they make anything at all on these.

What truly amazes me, is the woofers.

Distortion is fairly low, AND the response up to the crossover region is quite flat.
I mean it beats quite a few much higher priced speakers seen on this site!!

Now a better tweeter and crossover, and wow!
 
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Maiky76

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This is a review and detailed measurements of the Polk Monitor 40 Series II bookshelf "MTM" speaker. It is on kind loan from a member and costs US $200 on Amazon for a pair including Prime shipping.

The Monitor 40 looks pretty decent for such a budget speaker:

View attachment 135102

After decades of surviving in brutal consumer market for speakers, Polk knows what it is doing here. And that involves super lightweight design and shoddy construction that allowed the front baffle completely separate itself from the enclosure in shipping!

View attachment 135103

They have a rabbet all around which provides for large surface area for the glue and air tight construction. Why did they resort to these wedges that gave out due to weak fibers in the MDF? A couple of screws would have helped keep it there as well.

At least there is some foam inside:
View attachment 135104

They put money toward bi-wiring terminals that no one uses but likely checks a box for marketing:

View attachment 135105

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 1000 measurement which resulted in error rate of less than 1% or so.

Temperature was 68 degrees F.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the tweeter center.

Polk Monitor 40 Series II Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

View attachment 135106

Lots of issues here starting with tweeter frequency not being flat and elevated. The woofers are getting more directional before tweeter takes over and presents a wider dispersion. Near-field measurement shows the many flaws:

View attachment 135107

We clearly see the issues with the tweeter but also the port letting out a resonance right at the crossover. The woofers are allowed to play up to 5 kHz making me wonder if the filter for it has too little slope.

Early window response has no choice but to be messy:

View attachment 135108

Summing these produces an estimated response in your room that is likely to be quite bright:

View attachment 135109

Bass response is low which helps keep distortion in check especially given the dual woofers:
View attachment 135111

View attachment 135113

Horizontal beam width is not pretty as we could already guess from the spin graph:

View attachment 135114

View attachment 135115

I think this is the first MTM configuration speaker we have tested so its classic dispersion is nice to see:

View attachment 135116

Edit: forgot the impedance and phase:
View attachment 135134


Polk Monitor 40 Series II Listening Tests
Oh wow, this speaker is bright! High frequency notes literally jump out of the speaker and meet you half way! I must say, I can see the appeal of that in a showroom and with casual listeners. Bad choice to throw at me though as I am super sensitive to high frequency accentuation (spent so much time training to hear distortion in them). So I had to pull out the parametric EQ tool in Roon right away:

View attachment 135117

This is a quick and dirty correction to make the sound bearable. It was still bright but likely if you add a sub, it would balance it out.

Power handling was excellent because there is essentially no sub-bass reproduction so my killer tracks of this kind did not do much to Monitor 40.

Conclusions
The Polk Monitor 40 Series II is a great example of what you have to do to bring the cost down to crazy low yet keep the showroom appeal high. is this the most broken thing Polk could design? No, that would require a lot of distortion as well which I did not find. Still, without equalization and lots of playing around with that I don't see this being a useful speaker to live with, monetary savings be damned. Eat less outdoors, save the money, and buy something better please!

I can not recommend the Polk Monitor 40 Series II.

------------
As always, questions, comments, recommendations, etc. are welcome.

Had a miserable day yesterday. Why is it that all plumbing work is hell? We spent a fortune to have a yard guy dig trenches in our orchard for sprinklers. We were not here to watch the guy and he used the thinnest PVC tubes he could to save money -- much like Polk above. Worse yet, didn't know much about plumbing and created many sources of water leaks. This is the second time I have had to dig a ditch 3 feet down in thick mud and clay. :( I could barely expose the failure point and have to dig more to make space to fix it. So more muddy miserable days are awaiting me until I get this thing fixed....

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Hi,

Here is my take on the EQ.
These EQ are anechoic EQ to get the speaker right before room integration. If you able to implement these EQs you must add EQ at LF for room integration, that usually not optional… see hints there: https://www.audiosciencereview.com/...helf-speaker-review.11144/page-26#post-800725

The raw data with corrected ER and PIR:

Score no EQ: 2.2
With Sub: 5.0


Spinorama with no EQ:
  • Subwoofer mandatory
  • Not flat
  • Ascending balance
Polk Monitor 40 No EQ Spinorama.png


Directivity:
Better stay at tweeter height with the MTM config
some issues at the cross over
Polk Monitor 40 2D surface Directivity Contour Only Data.png

Polk Monitor 40 LW better data.png

EQ design:

I have generated one EQ. The APO config file is attached.
  • The EQs are designed in the context of regular stereo use i.e. domestic environment.
  • A lot of EQ! Probably many better options out there.

Score EQ Amirm: 4.3
with sub: 7.0

Score EQ Score: 5.2
with sub: 7.9 -> add a sub!

Code:
Polk Monitor 40 APO EQ Score 96000Hz
June152021-104327

Preamp: -2 dB

Filter 1: ON HPQ Fc 72.30 Hz Gain 0.00 dB Q 1.23
Filter 2: ON PK Fc 128.00 Hz Gain -2.66 dB Q 1.46
Filter 3: ON PK Fc 259.38 Hz Gain -1.45 dB Q 12.00
Filter 4: ON PK Fc 452.00 Hz Gain 1.42 dB Q 2.31
Filter 5: ON PK Fc 770.50 Hz Gain -1.14 dB Q 2.90
Filter 6: ON PK Fc 1351.17 Hz Gain -2.81 dB Q 6.24
Filter 7: ON PK Fc 1631.00 Hz Gain 2.60 dB Q 2.43
Filter 8: ON PK Fc 2666.50 Hz Gain -1.25 dB Q 3.33
Filter 9: ON PK Fc 5796.00 Hz Gain -3.10 dB Q 1.36
Filter 10: ON PK Fc 13017.00 Hz Gain -5.24 dB Q 2.39

Polk Monitor 40 EQ Design.png

Spinorama EQ Amirm
Polk Monitor 40 Amirm EQ Spinorama.png


Spinorama EQ Score
Polk Monitor 40 Score EQ Spinorama.png


Zoom PIR-LW-ON
Polk Monitor 40 Zoom.png


Regression - Tonal
Polk Monitor 40 Regression - Tonal.png


Radar no EQ vs EQ score
Great improvements
Polk Monitor 40 Radar.png


The rest of the plots is attached.
 

Attachments

  • Polk Monitor 40 APO EQ Score 96000Hz.txt
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  • Polk Monitor 40 3D surface Vertical Directivity Data.png
    Polk Monitor 40 3D surface Vertical Directivity Data.png
    838.2 KB · Views: 22
  • Polk Monitor 40 3D surface Horizontal Directivity Data.png
    Polk Monitor 40 3D surface Horizontal Directivity Data.png
    796.8 KB · Views: 34
  • Polk Monitor 40 2D surface Directivity Contour Data.png
    Polk Monitor 40 2D surface Directivity Contour Data.png
    585.1 KB · Views: 21
  • Polk Monitor 40 Normalized Directivity data.png
    Polk Monitor 40 Normalized Directivity data.png
    320.9 KB · Views: 24
  • Polk Monitor 40 Raw Directivity data.png
    Polk Monitor 40 Raw Directivity data.png
    510.4 KB · Views: 25
  • Polk Monitor 40 Reflexion data.png
    Polk Monitor 40 Reflexion data.png
    147.9 KB · Views: 22
  • Polk Monitor 40 LW data.png
    Polk Monitor 40 LW data.png
    147.1 KB · Views: 30
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AudioTodd

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Not a surprise, sadly. Nearly 40 years of underwhelming “performance” in my experience.
 

beaRA

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Not a surprise, sadly. Nearly 40 years of underwhelming “performance” in my experience.
The Polk R200 managed the second highest preference score of any passive bookshelf with publicly available spin data (calculated by @pierre based on measurements by @napilopez). I'm not sure why so many people want to pass judgement on Polk as a whole based on one of their cheapest designs.
 

TeeMann

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The Polk R200 managed the second highest preference score of any passive bookshelf with publicly available spin data (calculated by @pierre based on measurements by @napilopez). I'm not sure why so many people want to pass judgement on Polk as a whole based on one of their cheapest designs.
Agreed...the smell of 'haterade' :)
 

Joe Smith

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I love my old late 80's Monitor 5jr+ and 4 speakers, also those little front-angled ABS housing "Polk Monitors" sound quite good in smaller rooms. I fear that Polk is not doing a good job of holding on to what made them good/great in the first place. I think I paid $300 for the 5jr+ speakers back in '87, that was a lot for me then. They have held up extremely well.
 

beagleman

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I love my old late 80's Monitor 5jr+ and 4 speakers, also those little front-angled ABS housing "Polk Monitors" sound quite good in smaller rooms. I fear that Polk is not doing a good job of holding on to what made them good/great in the first place. I think I paid $300 for the 5jr+ speakers back in '87, that was a lot for me then. They have held up extremely well.



I owned a pair of those years ago, (5jr+)and they were quite nice for what they are.
I also got a pair of Rta11t's but at $450.00 (special discount) that were quite nice.

Have owned about 5 other pairs since (different lines) and none have been less than very good.
 

AudioTodd

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I'd get more experience.
Yup
To you and @beagleman I apologize for succumbing to the all-too-common (and cursed by myself) internet tendency to pop off some non-constructive ill-informed opinion without true consideration.

I HAVE not heard Polk speakers in several years. I was never impressed with any I did hear, but that was way too far back for me to be able to make any useful contribution and certainly not my "judgement." Thank you for the correction. My comments were not properly in the spirit of this valued forum.

Obviously you guys have knowledge of this company's range of speakers. Do you have any models or model ranges you would suggest a buyer should familiarize themselves with? While I am not in the market at the moment, some here might be.

Thanks again.
 

escape2

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Do you have any models or model ranges you would suggest a buyer should familiarize themselves with? While I am not in the market at the moment, some here might be.
From the currently made ones, the Reserve line has been getting some positive feedback. Hoping Amir will test one of them soon.
 
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