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Monolith HTP-1 Measurements and Analysis

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All measurements were conducted using my Quantum Asylum measurement rig, consisting of the QA401 audio analyzer and QA480 oscillator and notch filter. The QA401 has a THD+N of around -100dB or a bit better and with the inclusion of the notch filter, can be improved to -120dB THD+N or a bit better. The QA401 and QA480 are more than adequate to measure the Monoprice HTP-1 but is limited in distortion and noise measurements to just 1khz, the center frequency of the notch. As such, for this review, THD and noise measurements are limited to just 1khz. In addition, the QA480 is single-ended, requiring very carefully matched tight tolerance parts. As such, to measure the fully differential output of the HTP-1, I had to measure each phase or half of the output. This still provides an accurate characterization of the performance of the device, though voltages will be half of the actual voltage seen by the amplifier since the voltages are for only half the signal.

Monoprice HTP-1 Preamplifier Measurements

The Monoprice HTP-1 has a lot of settings to best match the output of the preamplifier to that of the input sensitivity of the amplifier. I played around with these settings and ultimately set it to best match the sensitivity of the intended Monolith amplifiers. I also used somewhat non-standard voltages in part because I was only measuring half the phase.

Monolith 1khz FFT Notch

Monolith HTP-1 FFT Distortion Analysis

The Monolith HTP-1 is officially the lowest noise and distortion home theater processor I have ever measured or used. If you look at the bow shape of the FFT measurement you can see that a notch filter is evident, which is due to the higher noise of the HTP-1 than the notch filter itself. This shows that the measurement is not the limiting factor. Still, no other home theater processor even comes close to this. This measurement indicates 0.72 Vrms which is 1.44 Vrms balanced. The 2nd harmonic lies at -102dB and the 3rd harmonic is around -112dB.

Editorial Correction About Measured Output Voltage

When I made these measurements, I thought I was testing at > 4Vrms balanced but later realized I forgot to enter a correction factor in my test software to account for notch filter gain to get the correct output voltage. As a result, all of my values were reported too high by a factor of 3.16. All voltage values on this page have been updated accordingly.

The FFT distortion measured on the HTP-1 produced harmonics about 10dB lower than the really excellent Marantz SR8015 receiver and almost -20dB lower than the Marantz AV7706 I recently measured. This is excellent measured performance.

Monolith 1khz FFT Notch 3.7v 

I was curious what would happen if I pushed the output, so I raised the level to 4.2 Vrms balanced output or 2.1 Vrms per phase. This was the maximum clean output I could manage before the HTP-1 seemed to fall apart. Performance decreased to a still excellent -97.5 dB THD+N. While quite a bit worse, this is still better than the best the Marantz we measured could manage and better than any other home theater processor I have measured personally. Would better be better?  Of course, but this is what we get and this reflects the state-of-the-art in home theater processors at this time. Is THD+N of -97.5dB audible? I highly doubt it is for most, if not all, people. Especially since that is completely driven by 2nd harmonic distortion.

Signal to noise ratio depends on output level. The highest clean output the HTP-1 is capable of yields a signal to noise ratio of around 112dB. This may not equal to the best that the DAC chips are capable of, but it is close and reflects very good measured performance for a product in this category. It remains as good or better than any home theater processor or receiver I have measured. This reflects about 2-3dB better than the recently measured Marantz SR8015, which is the best signal to noise ratio we had previously measured on any home theater product in the last two years. However, with one big comparison difference, I didn’t A-weight. Unfortunately, I haven’t made an A-weighting filter for my notch filter yet and so my measurement is not weighted. I plan to do that for the future and will start including A-weighting to make it comparable to Gene’s measurements. How much better would the A-weighting make it?  I’m not totally sure, maybe another 3dB or so. There is so little power supply noise that I don’t think it would benefit a lot in that regard.

As I understand, the HTP-1 uses the AK4493EQ DAC chip and that suggests the HTP-1 is about 10dB worse than the theoretical limits of the chip. You rarely, if ever, see a final product whose real-world performance is fully equal to the capability of the DAC chip, and that goes double for home theater processors. The primary reason is that a DAC’s THD+N and S/N limit is based on the optimal level for each. In a home theater processor, the DAC must be used as part of a larger system in which it’s optimized for a variety of output levels as set by the volume control of the device and what is coming through it. At least that is what manufacturers have shared when I have asked why we don’t see better performance. In their defense, I have seen them send me firmware changes that optimize the output for different purposes and see significant changes in the THD-N and S/N, without seeing a change in the voltage output level.

I attempted to measure channel separation at 1khz. I did this by sending a test signal to the right channel while listening on both the left and right channels. The difference in the level of the left and right channel is the channel separation. To ensure this wasn’t limited by my test equipment, I stuck with the QA401 and QA480 setup, which limited me to 1khz. At that frequency, I measured better than 100dB of difference. I am not completely confident that this is the limit, so let’s say it’s at least 100dB. It likely worsens at high frequencies (where it is of far less audible consequence).

Bass Management and Frequency Response

Monolith Bass Management 

I forgot to adjust the HDMI output to 192khz and as such, I wasn’t able to measure the upper -3dB point of the processor. Having said that, it has state-of-the-art filter behavior, evident in the measurements with no strange high-frequency noise. Furthermore, if any of the surround modes are engaged on the HTP-1 or if Dirac Live is engaged, the sample rate becomes limited to 48kHz. Since surround modes and Dirac Live are two of the chief selling points of the HTP-1, it is unlikely to be used at a sample rate other than 48kHz. The bass was flat well below 10hz. Under the circumstances that it will primarily be used, its frequency response is excellent. Bass management is also textbook. The HTP-1 is highly configurable and I didn’t bother to measure all the settings. I set this to 80hz to show a typical use case and we find a perfect crossing of the filters at 80hz and exactly -6dB at that point. We also see that at 160hz the bass is down 24dB, which is textbook performance. We see some hash in the high frequencies of the bass output, but we also see that it is so far down as to be totally inconsequential. In other words, the bass management of this system is excellent. Nothing to worry about.

Dirac Live is the first automated room EQ system that made a surprising improvement in the sound.

To conclude, the Monolith HTP-1 is a state-of-the-art home theater processor with among the very best measurements of any home theater processor on the market for any amount of money. While it does not equal the finest DAC performance, it is still excellent. I wish this kind of performance was available for less money, but unfortunately, it is not. What I can say is that spending 10 times more does not give you this level of performance. This is actually better measured performance than we have seen from some of the most expensive processors on the market. While it may be a stretch to call anything this expensive a value, the fact that it offers this level of measured performance for so much less than the most esoteric processors does lend credence to the notion.

Conclusion

HTP1 frontClearly, this review does not comprehensively cover the entirety of the HTP-1’s operation. It only covers aspects of its operation that I was equipped to deal with. The reviewer that could thoroughly explore its full potential would need nine bed speakers, six height speakers, and five subwoofers, and all with balanced inputs on the amplifiers. Few, if any, audio reviewers have a system like that. This review should be looked at as a glimpse at some of the possibilities and limitations of the HTP-1 in both a large scale 16-channel system and also its potential advantages for lower speaker count systems. We looked at the extraordinary level of control the user has over every channel, from the myriad ways there are to adjust the response to the flexibility that the HTP-1 can assign its outputs to a variety of speaker roles. We looked at the practicality of many of the features that the HTP-1 supports. We also looked at how well the user is able to control the breadth and depth of the HTP-1’s capabilities.

In my opinion, the HTP-1 is a very good product. It isn’t perfect, and it has its quirks, but once I understood those quirks, it turned out to be reliable and easy to use. Among its quirks are the odd design decisions in the firmware updating process, the very insensitive touch screen, and the finicky network connection (which again, could very well have been a “me” problem). I also had occasional audio dropouts with the USB audio connection. I never had any problems with HDMI connectivity nor TOSLINK connectivity. I didn’t use any other connection types. These quirks are understandable given the scope and complexity of the product. The HTP-1 is a computer with a whole lot more audio/video inputs and outputs than your traditional PC. No modern PC is free from the occasional bug or glitch, even ones produced on a scale far beyond the production that the HTP-1 is seeing: these systems are far too complex for that. To be honest, I was surprised that the HTP-1 functioned as reliably as it did. Note that the problems I had were largely setup issues, and once the unit is set up and going, it’s trouble-free. The points at which I would have most expected technical problems, which were HDMI connectivity and Dirac calibration, went smoothly, without a hitch.

Dirac Live turned out to be a game-changer among automated room EQs for me. I was never impressed with Audyssey or MCACC (RIP Pioneer AVRs?), and while I do not have experience with Yamaha’s YPAO, I haven’t heard good things about it. Dirac Live is the first automated room EQ system that made a surprising improvement in the sound. It’s true that the speakers and setups I was running were flawed to start with, and that a much better sound system would not have seen as dramatic of an improvement. However, I wanted to see what Dirac could do with a very typical setup. The result was a major improvement. Those who are running multiple subs and don’t want to fuss with endless tweaking to get them optimized are strongly encouraged to get the Dirac Bass Control upgrade, even with its premium upcharge. I wish I could keep this HTP-1 review unit instead of having to send it back, and the main reason for that is Dirac Live.   

HTP1 front angleI didn’t ever expect Monoprice to release a processor like the HTP-1, but I am glad they did. There are other A/V processors under five-figures vying for this space from JBL Synthesis, Emotiva, and Marantz, among others, but given what I know about the field, I would pick the HTP-1 over these others. Monoprice has come a long way since launching the Monolith product line. They have made themselves into a one-stop-shop for putting together an entire high-performance home theater system. Of the Monolith subwoofers, amplifiers, and loudspeakers, we have found everything to be well-engineered. You could put together an amazing home theater system using Monolith products alone, and the HTP-1 makes for a terrific heart of the whole system.

 

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

  • StarStarStarStarStar — Excellent
  • StarStarStarStar — Very Good
  • StarStarStar — Good
  • StarStar — Fair
  • Star — Poor
MetricRating
Multi-channel Audio PerformanceStarStarStarStarStar
FeaturesStarStarStarStar
Ease of SetupStarStarStarStar
Remote ControlStarStarStar
PerformanceStarStarStarStarStar
ValueStarStarStarStarStar
About the author:

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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Recent Forum Posts:

PENG posts on March 04, 2021 08:16
If we ignore Amir's narrative part, the measurements do seem very comparable/consistent:

Within +/- 0.5 dB !!

So again, aside from the narrative part, take Amir with a grain of salt, but his measurements so far has been quite consistent to those published by others, including Denon/Marantz, Hometheaterhifi, and now Audioholics.

ASR:
Monoprice HTP-1 Home Theater Processor Review | Audio Science Review (ASR) Forum

45349

Shady's:

I was curious what would happen if I pushed the output, so I raised the level to 4.2 Vrms balanced output or 2.1 Vrms per phase. This was the maximum clean output I could manage before the HTP-1 seemed to fall apart. Performance decreased to a still excellent -97.5 dB THD+N.

Same for SNR/DR, both reviews measured around 112 dB, not A-weighted.

45350
shadyJ posts on February 28, 2021 18:52
The stuff that ASR dinged the HTP-1 for is stuff that is inconsequential in real-world use for 99.99% of users. There may be some exotic circumstance where the stuff he penalized the HTP-1 could become a problem in certain scenarios, but the vast majority of users will never have to worry, it will perform beautifully.
Erod posts on February 28, 2021 18:35
bombadil, post: 1464503, member: 78088
I may have missed some of this discussion, but I am confused by the fact that Amir gave this unit a headless panther (worst rating) and Audioholics gives it 5 stars. The unit cannot be poor and excellent so I'm guessing there were issues that ASR found important that Audioholics either didn't measure or don't feel are important. If someone cares to explain the different views I'd appreciate it.
Kris Deering gave the HTP-1 a stellar review in Sound & Vision. Always take Amir with a grain of salt.
ryanosaur posts on February 28, 2021 12:04
bombadil, post: 1464512, member: 78088
Thanks. I did review the ASR testing and he did use a lower output and it helped but not much:
“Reducing the level to 2.7 volts which is the max that some other processors/AVRs produce before clipping gave a bit better performance: ”
He also found that the unit truncated 24 bit inputs and when a setting was changed truncation was less but the output was still clipped. Jitter was also high:

"Seems like the same shop that supplied the audio subsystem for XMC-1 is behind the same mistaken design in HTP-1. We could forgive the XMC-1 for being old but no such excuse holds for HTP-1. Folks, this is ABCs of design. You verify simple things like whether the device can process 24-bit data. After all, almost all video soundtracks are 24 bits.

EDIT: There is a setting in the menu to override the low level muting. The output clips though. See: https://www.audiosciencereview.com/…me-theater-processor-review.11416/post-326504“

Jitter was another disappointment”

So it seems that there is more to it. I don't want to start an argument, I am neutral in this thing and was hoping the Monolith was a good alternative to the Anthem processors. I was set to get one of the new Anthem processors but of course you know how screwed up that launch has been so just looking at alternatives.
I'm not an owner, have been actively following the HTP-1 owners thread over at that other site, though. I am interested strongly in this device.
With the exception of a very small group of people, almost everybody I have seen comment loves the HTP-1. While there are growing pains with the new device, the HTP-1 seems to be crushing the competition. This includes MANY users who have abandoned Emo and Anthem.
At the end of the day, I'm not a super tech-head so a lot of the stuff Amir comments on is above my pay grade. That said, for pretty much anybody that I've seen comment, there is a lot of disagreement with Amir. Again, to really see the details yourself, you would need to read both those threads in completion to get a feel for the device. Unless you just take the plunge.
bombadil posts on February 28, 2021 11:52
ryanosaur, post: 1464505, member: 86393
short version: Amir insisted that he measure at 4vrms, if I understand correctly, which creates more distortion, however this unit would not be used like that by most (if any!) users, and at 1.6-2 vrms, its distortion ratings are pretty flippin stellar.
Amir's rating is based on his ego rather than common use. Pretty much what it boils down to.

I think if you take the time to research Amir;'s review discussion thread and the HTP-1 Users thread from around that time, you'll find all the info needed!

Keep in mind, he re-measured the Denon 3600? after denon called him on some foolery. He would not devisit the review of the HTP-1, though he may have made an addendum far down in the thread.
Thanks. I did review the ASR testing and he did use a lower output and it helped but not much:
“Reducing the level to 2.7 volts which is the max that some other processors/AVRs produce before clipping gave a bit better performance: ”
He also found that the unit truncated 24 bit inputs and when a setting was changed truncation was less but the output was still clipped. Jitter was also high:

"Seems like the same shop that supplied the audio subsystem for XMC-1 is behind the same mistaken design in HTP-1. We could forgive the XMC-1 for being old but no such excuse holds for HTP-1. Folks, this is ABCs of design. You verify simple things like whether the device can process 24-bit data. After all, almost all video soundtracks are 24 bits.

EDIT: There is a setting in the menu to override the low level muting. The output clips though. See: https://www.audiosciencereview.com/…me-theater-processor-review.11416/post-326504“

Jitter was another disappointment”

So it seems that there is more to it. I don't want to start an argument, I am neutral in this thing and was hoping the Monolith was a good alternative to the Anthem processors. I was set to get one of the new Anthem processors but of course you know how screwed up that launch has been so just looking at alternatives.
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