Monoprice MP-65RT Bookshelf Speaker Review

Monoprice MP-65RT Introduction

People often ask us, “How inexpensive can a bookshelf speaker get while still producing a reasonably good sound?” Monoprice astounded the audio community with their MP-65TW bookshelf speaker at $30 a pair. Monoprice was pleased with the design and decided to offer an upgraded version that swaps the dome tweeter with a higher-end ribbon tweeter. The MP-65RT has to be one of the lowest priced bookshelf speakers to sport a ribbon tweeter, and it is the subject of this review. It does have a significant price increase over the MP-65TW, but at $50 a pair, it hardly breaks the bank. Monoprice claims that it offers greater dynamic range, lower distortion, and more extension than the dome-tweeter model. However, our objective here is not to judge it against the MP-65TW but simply as a bookshelf speaker in the $50/pair price range. So, with that objective clearly stated, let’s see what kind of bookshelf speaker Monoprice delivers at this very modest price point…

Unpacking and Appearance

    

The MP-65RT pair arrived well-packed with cardboard corner pieces lining the box along with thick foam inserts. The speakers were wrapped in plastic bags to protect them from moisture and scuffing. These speakers are relatively light, so this packing should be more than adequate. Out of the box, the MP-65RT look plain: not bad, but not exactly eye-catching either. With the grilles on, they are pretty much just flat, black boxes. They look more interesting without the grilles, where the ribbon tweeter adds a dash of distinction and color. The fact that a $50/pair speaker set does not look flashy does not bother me in the slightest, they are a handsome pair of speakers, all  things considered.

Design Overview

The chief point of distinction on the MP-65RT bookshelf speakers is the ribbon tweeter. One does not normally see ribbon tweeters on speakers of this price class. They have mostly been a feature on far more expensive speakers - until now. What makes a ribbon tweeter so special? The answer is the low mass of the diaphragm. Ribbon tweeters work by placing very thin, conductive ribbon that is usually either conductive tracings on a material like Kapton or simply a very thin aluminum strip in a tightly controlled magnetic field between two permanent magnets. When alternating current is run through the ribbon, it vibrates as its magnetic charge rapidly oscillates between positive and negative (here is a short YouTube video that explains the basics with a simple model). The strip, or ribbon (hence its name), is folded in a zig-zag pattern like an accordion, so that the points where it bends are confined to a small area, and the ribbon moves as a whole in unison.

Proponents of ribbons claim they are better as high-frequency reproducers than domes because their moving mass is much lighter than domes and therefore can accelerate and decelerate much more quickly, and this quicker movement makes for a more realistic sound. However, ribbons have historically had a few disadvantages: they are more expensive to manufacture, they typically have had lower impedance loads and were thus a harder load on amplifiers, and they were fragile so they were not as capable in midrange frequencies as in treble. Monoprice seems to have found a tweeter that gets around these traditional shortcomings (we will look at how they managed to do this in the Measurements and Analysis section). A ribbon design like the one implemented in the MP-65RT that has a small width-to-height ratio suggests it should have wide horizontal dispersion and narrower vertical dispersion, and the waveguide that the MP-65RT tweeter uses should help control that dispersion pattern.

    

The cabinet of the MP-65RT is pretty basic, as one would expect at this price point. It is made from ½” thick MDF all around and there is no bracing. There is some stuffing lining the cabinet. The removable grille is held in by plastic pegs and is constructed out of a ¼” thick sheet of MDF with shaped cutouts for the drivers and is overlayed by a black acoustically-transparent fabric. The raised edges of the grille cutout around the tweeter is likely to cause some diffraction, so for the best sound, leave the grille off. The terminal cup uses spring-loaded clips to connect to the speaker wire. Some people have complaints that spring-loaded clips feel flimsy, but I don’t mind them; they provide a quick way to get a firm grip on the speaker wire. The disadvantages of spring-loaded clips is they will not fit large diameter banana plugs or large gauge wire, but other than that, they are convenient and do provide a tight connection. The woofer is pretty standard for low-cost speakers, but that is not to say it is bad.

The woofer uses a stamped frame and a reasonably large, but not huge, motor for the task of bass and mids. The permanent magnet is a 7 cm diameter, 1.5 cm thick slug. There doesn’t look to be any venting for the voice-coil, but this isn’t a high power-handling driver, so that might not be a significant omission. The cabinet is sealed, so this woofer doesn’t get any port assistance in reproducing bass. That should make for a higher rolloff frequency but a more gradual roll-off slope, so this is a speaker that might benefit more from being placed near room surfaces for more natural-sounding boundary gain than is had with ported bookshelf speakers.

There isn’t much in the way of a crossover circuit, merely a capacitor that is soldered onto the tweeter, so the woofer is running full-range. While it is always preferable to filter out high-frequencies to the woofer to some extent, woofers can be made to handle high-frequency playback gracefully so that their contributions will be less offensive when tasked to play that high. That is very likely the case with this woofer.

Listening to the MP-65RT Bookshelf Speakers

In my approximately 24’ by 13’ listening room, I set up the speakers with stand-off distances between the backwall and sidewall, and equal distance between speakers and listening position, with speakers toed-in toward the listening position. Distance from the speakers was about 6 feet. Amplification and processing was handled by a Pioneer Elite SC-55. No room correction equalization was used. At times, subwoofers were used to supplement the bass, mostly using a 100 Hz crossover frequency.

Music Listening

I decided to start off my critical listening of the MP65RTs with something that placed emphasis on vocals, since the human voice is the instrument to which human hearing is most finely tuned for, i.e., it’s easy to catch problems when paying attention to voices. One artist who has always had pristine recordings of vocals is Sarah McLachlan,so I demoed her “Wintersong,” Christmas album. The first thing I noticed was very strong imaging, with a precise center image of Sarah’s voice and nice peripheral instrumental imaging. It also occurred to me a few tracks into the album that this was a bright speaker and a bit sibilant. The ‘S’ sounds in lyrics were over-emphasized. It wasn’t the worst I have heard, but it was certainly present. To take the edge off the brightness I tried various inward toe-in angles that placed me off direct axis of the speaker, and this did alleviate the brightness, although not entirely. With the reduced brightness, McLachlan’s voice sounded rich and sonorous, and the brightness did impart a sense of heightened detail. I did not employ subwoofers for the playback of this album in order to get sense of the MP-65RT’s bass capability, which I found  to be present without being overbearing. 

For music of a greater complexity, I turned to a grand performance of J.S. Bach’s St. Matthew Passion, performed in 1994 in the chapel of King’s College by The Choir of King’s College, Cambridge and conducted by Stephen Cleobury. Although this epic oratorio runs three hours in length, every minute is a pleasure to hear, and so much the better with a good sound system. So how did the MP-65RT speakers fare for the playback of this sublime recording? With the speakers toed-in for an intersecting angle of about three to four feet in front of me, their brightness had already been tamed significantly. Again, their imaging was superb (perhaps assisted by this hard toe-in) in both depth and breadth of the soundstage. I had a much more expensive speaker on the AVR’s speaker B output, and, switching between the Monoprice MP-65RT and the more expensive speaker (6x the MP-65RT’s cost), the difference is not nearly as great as the price. The more expensive speaker had smoother treble and more authoritative bass, but in terms of imaging, it seemed to hold no advantage over the MP-65RTs. This is not to say the expensive speakers under-performed, it is just that the MP-65RTs over-performed in this instance. The instrumentation sounded good all-around as did vocals, but perhaps a tad lean versus a setup with deeper bass extension. In such a spectrally-dense recording, the addition of subwoofers would help the MP-65RTs but are not absolutely necessary for a recording like this. I had the speakers positioned relatively far from walls, so they were not getting the acoustic boost in bass that they would normally get in most setups. The performance sounded good, and I could not readily identify any serious shortcomings of the MP-65RTs when listening to this recording of St. Matthew Passion—difficult to believe from a $50 per pair speaker set!

To push the speakers harder at a more constant level like would be seen in rock or pop music recordings, I threw in an oldie but goodie (for me, at least), “21rst Century Jesus” by Messiah, a techno/rock act by the British duo Mark Davies and Ali Ghani. This music is much more consistently loud than Sarah McLachlan or The Choir of King’s College performance of St. Matthew Passion. It has a lot more bass and a lot more treble than McLachlan’s ballads or an orchestral choir, and here is where the shortcomings of the MP65RT became more apparent.

Without subwoofer assistance, the MP-65RTs did sound somewhat thin, although there was some bass. There was also some midrange congestion that slightly obscured some of the percussion. I also noted that, switching between the expensive bookshelf speakers on the AVR’s speaker B output, that the MP-65RTs did not quite have the treble resolution that the more expensive bookshelf speakers did. It wasn’t a stark difference, but it was notable. When I kicked in the subwoofers, the overall sound of the MP-65RTs did seem to get ‘fuller.’ It should also be said that the flaws of the MP-65RT are more manifest at louder volumes. At modest loudness levels, these shortcomings are not so easy to detect. With a 30-watt RMS power handling rating, these are not party speakers and aren’t meant to be blasted hard.

I also used the MP-65RTs in the near-field as desktop speakers, since some bookshelf speakers do not maintain their far-field sound in the near-field and so do not sound good at this close distance. The MP-65RTs sounded similar on my desktop to how they sounded in my home theater, so they get a pass for near-field applications. I did have them elevated off the top of my desk by using some makeshift desktop speaker stands, since direct desktop placement can make for some very audible acoustic reflections off the desktop surface that degrades the sound. For placement of any bookshelf speakers on a desktop, I recommend elevating them off the desk as high as possible while keeping the tweeter near listening-position ear-height (unless the speaker has been shown to have a better response at a higher or lower angle than direct axis).

Movie and Television Listening

Continuing my viewing of the second season of “True Detective” from my last affordable bookshelf speaker review I watched episodes three and four. I do enjoy a bleak crime drama! As I said in the Dayton Audio MK402 review, I think “True Detective” is a good trial for dialogue intelligibility because of how abridged and elliptical the dialogue can be at times even though it is all well-recorded. Music is also beautifully recorded; it is generally foreboding and atmospheric but has some folk music performances in a grim and sad style that compliments the show. I did use subwoofers for this show, since I knew there would be low-frequency effects beyond the capability of the MP-65RT speakers. Regarding the MP-65RT’s performance, dialogue, effects, and music were all nicely reproduced for the most part. However, at the end of episode four, there is a major action scene in which the MP-65RT wasn’t able to muster the punch that I am used to with heavier-duty loudspeakers. I didnt’t expect THX Reference level ability from a speaker of such modest price and power handling capability though, so it's not surprising they weren't able to pull off the dynamic range of more expensive speakers. All in all, I think they did very well, especially considering their cost. For those looking for a simple bookshelf speaker setup that is better than built-in TV sound, the MP-65RTs are incomparably better. I enjoyed continuing my journey with Season 2 of “True Detective” with the Monoprice MP-65RT speakers. I kept pondering how hard tit was o imagine this mix sounding better on any other speaker at this price point.

One movie that I watched with the MP-65RTs that has a very dynamic sound mix is Sam Raimi’s 2009 horror-comedy “Drag Me To Hell.” This is a horror movie that uses sound to tremendous effect and nicely demonstrates just how important sound is in a movie, especially a horror movie. One reason for this is because the movie’s ‘monster’ is largely invisible, so sound is used to compensate for lack of sight. This is a great movie to play loud, and that is what I did using the MP-65RTs which did an admirable job of keeping up with this soundtrack, especially when factoring in the cost. I may well have been pushing the speakers into distortion, but I didn’t get a sense of that occurring, since I didn’t play “Drag Me To Hell” quite at reference level loudness. A more powerful speaker would certainly be capable of higher SPL, but I think most buyers would be very satisfied at the loudness levels it can achieve without hitting obvious distortion. Something else that deserves mention here is Christopher Young’s outstanding music score, which magnificently matches the action and tension of the on-screen drama. It is a mix of traditional claustrophobic horror cues, large scale orchestral power, and a deft mix of a dread ambience and bracing terror. It sounded great on the MP-65RTs for whatever their limitations might be.

MP-65RT Bookshelf Speaker Measurements & Conclusion

 

The Monoprice MP-65RT speakers were measured in free-air at a height of 7.5 feet at a 1-meter distance from the microphone, and the measurements were gated at a 8.5 millisecond delay. In this time window, some resolution is lost below 250 Hz and accuracy is completely lost below 110 Hz. Measurements have been smoothed at a 1/24 octave resolution.

 

Monoprice MP-65RT response curves 

The above graph shows the direct-axis frequency response and other curves that describe the speaker’s amplitude response in a number of ways. For more information about the meaning of these curves, please refer to our article Objective Loudspeaker Measurements to Predict Subjective Preferences. The feature that leaps out the most in the MP-65RT’s response is the eruption of treble that occurs above 8 kHz. That certainly explains the speaker’s brightness. We see this elevated treble in in all of the power responses but the directivity indexes are smooth in that region, and that tells us that this large treble bump happens over a wide angle around the speaker. The good news is that this rise in high-frequency response doesn’t really get significantly hot with respect to the rest of the bandwidth until 9 kHz. That means that elevated treble largely escapes most of the harmonics of human voice and musical instruments, but it will have an audible effect. The narrower spike at 3.5 kHz may have a more significant impact, since it lies in a region that is far more heavily used in recorded content, but that spike is somewhat narrow and so may look more offensive in this graph than it would be heard. What is more, we see it as a feature on the directivity index curves unlike the 8 kHz+ treble eruption, so it doesn’t occur at nearly as wide of an angle over the space around the speaker. Below that 3.5 kHz spike, the response is relatively smooth. The bottom line here, as was heard in the listening sessions, is that ribbon tweeter is working overtime!

 

Monoprice MP-65RT Horizontal Response +/- 100 degrees: 3D view

Monoprice MP-65RT Horizontal Response +/- 100 degrees: 2D view 

The above graphs depict the MP-65RT’s horizontal dispersion out to a 100-degree angle in ten-degree increments. In these graphs we get a look at how that upper-treble swell behaves at off-axis angles. While it does calm down as we move off of direct axis, it is still considerably hotter than the lower frequency band, so listening to the MP-65RT at an off-axis angle will still make for a bright sound, especially in a more reflective, reverberant environment. To truly take that treble, it would need to be equalized. In these graphs we can see how and why the 3.5 kHz peak crops up so prevalently on the directivity index; by the time it reaches a 90-degree angle off-axis, it has pretty much inverted into a dip. Ordinarily I would assume that kind of behavior to be the result of phase summation and cancellation between the woofer and tweeter, but in this case,  it may be the result of breakup behavior of the woofer. The most neutral overall response happens at the 50-degree angle; here is a graph the 50 degree angle versus the direct axis angle for a more distinct look at those two responses:

 

Monoprice MP-65RT Horizontal Response: direct-axis versus 50 degrees off-axis

At 50 degrees off-axis, the response remains very steady until 6 kHz, and the treble eruption isn’t as severe as on direct-axis.

 

 Monoprice MP-65RT Polar Map of Horizontal Response

The above graph shows the same information that the preceding horizontal dispersion graphs do but depict it in a way that offers new insight regarding this speakers behavior. Instead of using individual raised lines to illustrate amplitude, polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is they can let us see broader trends of the speaker’s behavior more easily. In the polar map of the MP-65RT that excess of treble energy really looms over the rest of the response. We do see that the midrange frequency has a very nicely controlled dispersion up to 4 kHz. Something that is interesting to see is slight lobing patterns from 4 kHz to 7 kHz, as the woofer and tweeter enter into different degrees of phase at various angles and distances. These lobing patterns are inevitable when the woofer is allowed to run full-range, but they are not severe on this model.

        

Monoprice MP-65RT Vertical Response +/- 100 degrees: 3D view

The above graph depicts the MP-65RT’s frequency response behavior on its vertical axis, where zero degrees is directly in front of the tweeter, negative degree values are below the tweeter, and positive degree values are above the tweeter. The valleys that occur above and below the zero-degree axis are very common in conventional loudspeaker design. They are the result of the tweeter and woofer playing the same frequencies but out of phase, so they are not synchronous. They are usually only fully synchronous directly ahead of the speaker. The lateral response matters far more than the vertical response, since most listeners will be on roughly the same height and also since the ear is much more sensitive to side-wall reflections than floor or ceiling reflections, so the ragged response off the direct axis shouldn’t be a cause for too much concern. The tweeter itself seems to exhibit some odd lobing patterns as the angle moves off direct-axis. It also swiftly loses amplitude off direct-axis, very much unlike its horizontal response. This is all predicted by its narrow width relative to its height. The story here, as with most two-way bookshelf speakers, is that the MP-65RTs should be listened to with your ears at speaker height, not above or below the speaker.

 

Monoprice MP-65RT Impedance and Phase Response

The above graphs show the electrical behavior of the MP-65RT speaker. This should be a relatively easy load for any amplifier to drive, with a minima at 6 ohms and soft phase angles at those points. All steep phase angles occur at high impedances. It can be seen that the resonant frequency of the woofer happens just under 100 Hz due to the impedance spike and sharp phase change. There are ripples in the impedance and phase curves that are evidence of cabinet resonances, and this is not surprising given the minimal cabinet construction. Monoprice specifies the MP-65RT as a 6 ohm speaker, and this is a conservative rating. I measured the sensitivity at 86.1 dB at 1 meter for 2.83v which is respectable for a sealed bookshelf speaker of this cost. That closely matches Monoprice’s spec of 87 dB for 1 watt at 1 meter. This speaker does not need a lot of power to get loud, which is good because it wouldn’t be able to handle a lot of power anyway. A 15 to 30-watt amplifier would make this speaker sing nicely.

 

Monoprice MP-65RT Low-frequency Response

The above graph shows the MP-65RT’s amplitude response in bass frequencies. It was captured by using groundplane measurement techniques. The bass response here is overall quite good, considering the cost of the speaker. The response above the resonant frequency near 100 Hz is relatively flat and even. The bass is slightly bumped up around resonance, but it is a mild enough rise that it should not register as ‘boomy.’ It does start to roll-off at a relatively high frequency, but it does so at a more gradual 12 dB/octave slope than what would be seen were this speaker ported. The good news about this kind of gentle slope is that it will get more reinforcement below the resonant frequency than a steep slope and so is likely to get more assistance from room gain and boundary gain. However, for content with heavy bass or deep bass, a subwoofer should be used, since that budget 6.5” woofer isn’t likely to have a lot of excursion.

Conclusion

Loudspeakers have to make compromises between price and performance. The price of the MP-65RTs is particularly low, so the compromises that it must make are particularly stiff. The question is, did Mnoprice make the right compromises to achieve its pricing? I believe that they did. It is not a perfect loudspeaker, but no loudspeaker at anywhere near its price will be perfect. The compromises it makes are many: minimal enclosure construction, the absence of a real crossover circuit, a tweeter with a sensitivity that doesn’t quite match the woofer (thus the elevated treble), lack of any aesthetic flare, relatively low power-handling, and so on.

But with a speaker like this, it is more reasonable to focus on what it does right; the MP-65RTs sound creditably good. By creditably good, I mean they can make a recording sound natural and clear, and, in the end, enjoyable. Their imaging abilities are far better than I had anticipated. Their chief audible sin is bright treble, but most systems have something like a tone control with a treble level that can bring the brightness down. Furthermore, most of that treble elevation occurs above 10 kHz which is not a heavily used range in most recorded content, so while the response in that range is lifted very high, its actual audible consequence isn’t nearly as severe as it looks on a graph. After equalization, I can attest that this speaker can sound pretty smooth.

The bottom line is that the MP-65RTs can be made to sound good. The flaws of this speaker are not insurmountable: subwoofers help, toed-in listening angles help, and some EQ on the highs help.

This is a $50 per pair speaker (as low as $40/pair on sale)  that is not just passable, but actually enjoyable in a range of recordings. For anyone who is looking for a cheap upgrade over their built-in TV sound, the MP-65RTs are a terrific choice.They can be used as a simple two-channel system in a room where it isn’t going to play at blazing levels, as desktop PC speakers, or as surround speakers, to name a few other uses. The MP-65RTs would be a good starter speaker for someone who wants to get into hi-fi but is particularly cash-strapped. It would also be a good project speaker for anyone who wanted to look at DIY improvements since the speaker’s component parts and fundamental design seem to be of high enough quality that it’s worth the effort to upgrade. Some relatively simple additions like a true crossover circuit or cabinet bracing might be enough to push these to another level of performance.

I wasn’t expecting to enjoy the MP-65RTs as much as I did, and I can say that anyone on a very low budget would do well to consider a pair. I would also say any loudspeaker enthusiasts who are not limited by budgetary concerns should listen to a pair so they can see how good a speaker can sound when made from such modest, low-cost components- I think they will be surprised.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Imaging
Fit and Finish
Performance
Value