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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 September 15, 2021 14:04
tparm, post: 1504579, member: 71264
I know this isn't likely to happen anytime soon, but I'd love to see Audioholics measurements AND subjective user/listening experiences with the updated X8500HA and AV8805A compared to the SR8015.

If you do the comparison based on ASR, Gene's and Marantz's own, the SR8015 pre out did measure a few dB better in THD+N and DR than the 8805A. The 8805's THD+N was about the same as the 8805A but better in DR, again by just a few dB.
tparm posts on September 15, 2021 11:28
I know this isn't likely to happen anytime soon, but I'd love to see Audioholics measurements AND subjective user/listening experiences with the updated X8500HA and AV8805A compared to the SR8015. While my RMC-1L sounds better (to me) than my previous Denons (X4700H, A110) I do miss how user friendly they were and well, the fact they just worked, compared to the Emotiva. The only other piece that has me intrigued, especially since I am not in any hurry to spend more money, is a new Yamaha processor. Any @gene intel there?

Everything I have runs via XLR connections that were custom made to make my rack tidy so I am hesitant to go back to all RCA interconnects and I prefer balanced inputs for an analog source. I do like Dirac but there is so much intellectual knowledge out there now for Audyssey (especially here, thank you) I think with some careful pre and post calibration tuning that is nearly a moot point. I probably shouldn't have sold my A110 but that is what drinking on the beach and looking at classifieds will do for ya…..

Lastly, the email from Marantz telling their Shirakawa Audio Works story was very cool. I guess the X8500HA and A110 are built there too but Denon only touts that on the Anniversary editions.
PENG posts on September 07, 2021 10:01
Matthew J Poes, post: 1503123, member: 85392
Hi Peng,

I am actually the better person to answer this as I was the one who measured the Monolith.

First let me say the simple answer to your question is that we don’t all work in an office together. At the time of this review I was in Chicago area. As is James. I was in the process of moving. I have the Quantum Asylum and Gene has the AP. He was in Florida. As such, it wasn’t possible for us to measure the Monolith on the AP without delaying the review. Gene had packed his AP as he was getting ready to move into his new house.

now in terms of accuracy. The answer is yes the QA is as accurate as the AP as long as the user doesn’t do something ham fisted. It’s a factory calibrated device with very good native specs. However, like all devices, it has a limit. It can only measure distortion (THD+N) down to around .0015% or so. That is the limit of the AD converter in its best mode and using an external pure source.

The AP would also have a similar limit if not for some tricks. AP has a notch filter. This notch filter is extremely precise and adjustable to any frequency. The addition of the notch filter allows you to dewarp the incoming signal and leave only the distortion of the DUT, canceling all distortion of the testing device hardware. I have that ability too. I also have a notch filter. But I have a problem. Fully adjustable notch filters are very expensive to make. Instead, mine is limited to just 1khz. I also have a 1khz pure sine wave oscillator. That means I too can measure extremely low levels of distortion.

this is where the ham fisted issue comes in. When I measured this device I accidentally forgot to account for the gain adjustment of the oscillator and notch filter. Further, I had been trying to ensure it was calibrated right because I was getting odd results and once I found the problem, forgot to undo the calibration value. None of this has any impact on distortion or noise measurements. It only threw off the voltage measurement at the output. We corrected it (or at least I submitted a correction once I found the problem).

so to answer your question. It is absolutely accurate. It’s capable of measuring noise and distortion down to -120dB and with software updates and new hardware boxes, it’s getting better. It is simply limited to 1khz for such measurements. All other measurements would be limited to more like -98dB or so. However I need to make a checklist for myself when I do this to be sure I don’t do something goofy. There are so many sources of error with modern processors and measurement gear that if you aren’t careful you can produce totally erroneous results.

as a case in point, it’s been noted that you can be too fancy for your own good. The same tech that allows you to measure these crazy low numbers can also cancel a portion of the DUT noise and cause an artificially low number. This often happens when the FFT is very high and a very long accumulation period is used. As such, a reviewer for a trade oriented publication measured a Purifi module and came up with results that are in fact lower than factory spec. I had asked Bruno if this implied the amp bring lower noise than the AP he uses. He said no, then sent me a graph that showed a good 20dB of additional margin. He told me that in reviewing the other measurements in question he found the results unlikely. How they were obtained? Who knows, but Bruno was confident they weren’t right. One guess was that the use of the oscillator, notch filter, and a large accumulation period might have combined with improper signal processing to lead to a bogus result.

as for the Marantz. My fault. I have it sitting here in a box. I was supposed to move into my new place 2 months ago. But long construction delays put us at October. I had assumed I could setup a good measurement space here, but it turns out that 1000 sq ft is not enough for two young kids, a dog, cat, wife, two crabs, and lots of life crap. Gene is 90+ minutes from me and it’s been hard to find a good time for both of us to focus just in measuring the preamp at his house.

if all you want is a THD+N spec and voltage max, it should be close or the same as the 7705. That didn’t change the audio hardware. We will get to this eventually. I should reach out to Gene again to get that going.

Thank you very much for the quick response. I am very keen on knowing how the 7706 compared to the AV7015/SR8015 because the 8015 has the different HDAM version and measured so much better, while the SR8012 measured about the same as the two AV7705s Amir has measured so far(in SINAD, SNR, DR etc..).

Now that you confirmed the 7706 measured about the same as the 7705, then I guess the better HDAM version used in the SR8015 has not been filtered down to the 7706 yet. To me THD+N at the level of those AVP/AVRs for the preamp/DAC is more about indicators of how well the thing is put together, in addition to using better quality parts/components, much less to do with audible difference in the end.

Regardless, I still love to see the measurements as I do value those indicators. Thanks again for fast tracking the THD+N part of the 7706 you measured. Hopefully you or Gene will soon measure a Denon AVR such as the mid range AVR-X4700H in preamp mode.
Matthew J Poes posts on September 07, 2021 09:17
PENG, post: 1503118, member: 6097
Hello @shadyJ , I just noticed you mentioned the SR8015's measurements and that was measured by the AP so am wondering why for the HTTP-1 you didn't use the AP. Is the QA401's accuracy comparable to Gene's AP?

Also, you mentioned measurement the 7706, is the results going to be published? Since AH has measured 3 recent Marantz models albeit all AVPs, it would be nice to measure a Denon AVR in preamp mode too, any plan for that? I would love to see AH do a little more bench tests of the popular AVR/AVPs, so we don't have to rely on ASR all the time. I know its a lot of work but I have to ask.

Almost forgot, do you know if Monolith has recently put a limit (via FW update) on the maximum output to 4 V XLR? I got that from someone on ASR, hope that is not true.

Thank you
Hi Peng,

I am actually the better person to answer this as I was the one who measured the Monolith.

First let me say the simple answer to your question is that we don’t all work in an office together. At the time of this review I was in Chicago area. As is James. I was in the process of moving. I have the Quantum Asylum and Gene has the AP. He was in Florida. As such, it wasn’t possible for us to measure the Monolith on the AP without delaying the review. Gene had packed his AP as he was getting ready to move into his new house.

now in terms of accuracy. The answer is yes the QA is as accurate as the AP as long as the user doesn’t do something ham fisted. It’s a factory calibrated device with very good native specs. However, like all devices, it has a limit. It can only measure distortion (THD+N) down to around .0015% or so. That is the limit of the AD converter in its best mode and using an external pure source.

The AP would also have a similar limit if not for some tricks. AP has a notch filter. This notch filter is extremely precise and adjustable to any frequency. The addition of the notch filter allows you to dewarp the incoming signal and leave only the distortion of the DUT, canceling all distortion of the testing device hardware. I have that ability too. I also have a notch filter. But I have a problem. Fully adjustable notch filters are very expensive to make. Instead, mine is limited to just 1khz. I also have a 1khz pure sine wave oscillator. That means I too can measure extremely low levels of distortion.

this is where the ham fisted issue comes in. When I measured this device I accidentally forgot to account for the gain adjustment of the oscillator and notch filter. Further, I had been trying to ensure it was calibrated right because I was getting odd results and once I found the problem, forgot to undo the calibration value. None of this has any impact on distortion or noise measurements. It only threw off the voltage measurement at the output. We corrected it (or at least I submitted a correction once I found the problem).

so to answer your question. It is absolutely accurate. It’s capable of measuring noise and distortion down to -120dB and with software updates and new hardware boxes, it’s getting better. It is simply limited to 1khz for such measurements. All other measurements would be limited to more like -98dB or so. However I need to make a checklist for myself when I do this to be sure I don’t do something goofy. There are so many sources of error with modern processors and measurement gear that if you aren’t careful you can produce totally erroneous results.

as a case in point, it’s been noted that you can be too fancy for your own good. The same tech that allows you to measure these crazy low numbers can also cancel a portion of the DUT noise and cause an artificially low number. This often happens when the FFT is very high and a very long accumulation period is used. As such, a reviewer for a trade oriented publication measured a Purifi module and came up with results that are in fact lower than factory spec. I had asked Bruno if this implied the amp bring lower noise than the AP he uses. He said no, then sent me a graph that showed a good 20dB of additional margin. He told me that in reviewing the other measurements in question he found the results unlikely. How they were obtained? Who knows, but Bruno was confident they weren’t right. One guess was that the use of the oscillator, notch filter, and a large accumulation period might have combined with improper signal processing to lead to a bogus result.

as for the Marantz. My fault. I have it sitting here in a box. I was supposed to move into my new place 2 months ago. But long construction delays put us at October. I had assumed I could setup a good measurement space here, but it turns out that 1000 sq ft is not enough for two young kids, a dog, cat, wife, two crabs, and lots of life crap. Gene is 90+ minutes from me and it’s been hard to find a good time for both of us to focus just in measuring the preamp at his house.

if all you want is a THD+N spec and voltage max, it should be close or the same as the 7705. That didn’t change the audio hardware. We will get to this eventually. I should reach out to Gene again to get that going.
PENG posts on September 07, 2021 08:08
Hello @shadyJ , I just noticed you mentioned the SR8015's measurements and that was measured by the AP so am wondering why for the HTTP-1 you didn't use the AP. Is the QA401's accuracy comparable to Gene's AP?

Also, you mentioned measurement the 7706, is the results going to be published? Since AH has measured 3 recent Marantz models albeit all AVPs, it would be nice to measure a Denon AVR in preamp mode too, any plan for that? I would love to see AH do a little more bench tests of the popular AVR/AVPs, so we don't have to rely on ASR all the time. I know its a lot of work but I have to ask.

Almost forgot, do you know if Monolith has recently put a limit (via FW update) on the maximum output to 4 V XLR? I got that from someone on ASR, hope that is not true.

Thank you
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