Integrated Amplifiers

Harman Kardon HK 990 Stereo Integrated Amplifier with Digital Room Correction and Dual Subwoofer Bass Management – Part I

ARTICLE INDEX

Conclusions About HK 990 Room EQ

With the addition of digital room-correction, the HK 990 travels into unique space for a stereo integrated amplifier. As a dual-domain device, its internal electronics are conversant with analog or digital inputs, including high resolution files. Recording from digital and analog sources is simplified. In addition, the HK 990 has no mechanical controls for improved reliability, improved gain tracking, and increased stereo separation. Unfortunately, the room EQ does not function properly in many operating modes. We can hope Harman patches the code. The engineers at Harman clearly understand what needs to be changed. It remains hazy whether these changes, if made available, will be available to products already sold, available only with a change at a service department, or something that can be done in the home. The timeline for these fixes also remains an open issue.

In Part II of the series, I examine dual-domain signal flow of the HK 990 at the block-diagram level. Those interested in AVRs may want to continue to Part 2 since the blocks are very similar. It is much easier to read a diagram in two channels instead of eight.

FEATURED COMMENTS

pics , pricing
Written by Donnie , October 22, 2011

I'd like to see interior pics , especially at this price point. Also I don't want to have to read so far down the page to find the price.

Seems like a great piece from a company with the potential to make great gear.

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Re. pics , pricing
Written by David Rich , October 24, 2011

Donnie,

Tyler Stripko published pricing, specifications, setup, use, and listening impressions in June. Refer to the link at the beginning of this review. I have two upcoming parts to be posted October 27 and November 3. The next part begins with an interior picture and examines the unit's configuration at the block diagram level. More details about the contents of my review are at the bottom of page 3.

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Thank you
Written by Vinh , October 24, 2011

I am absolutely astounded! A technical review that offers insight into the deficiencies of a product?

Simply outstanding! I haven't read a review this good in years. This is why I visit this website every month or so, in hopes of finding the rare article that contains actual substance. 

Thank you, thank you, thank you!

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    2-channel receiver with room EQ, almost complete...
    Written by Maarten , October 24, 2011

    I also use a multi-channel receiver in a stereo setup. My Audessey takes care of speaker EQ, including the subwoofer and crossover

    A stereo component with room EQ is great. What I am missing however, are HDMI inputs that accept DSD streams and the latest high def surround formats. I hope more companies will make stereo receivers with room EQ. Good informative review by the way! I look forward to the sequels.

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    Re. Thank you 
    Written by David Rich , October 25, 2011

    Vinh

    Your words are much too kind. My acoustic measurement tool (AcoustiSoft RplusD) is a primary reason I can detect problems and clearly illustrate the issues to the reader. The versatility of the low cost AcoustiSoft RplusD, written by Doug Plumb, is exemplified in the review.

    Please do not stay away for a month. There is a wealth of a material on the site similar to this review. The Secrets Blu-ray Player HDMI Benchmark series is a good example. Part 2 of this review is scheduled to appear on Thursday.

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    Software Update
    Written by Manendra , November 25, 2011

    Dr. Rich,

    It has been over a month since your review. Has there been any news from Harman engineers regarding an updated software to correct the issues you have identified in your review?

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    Software Update 
    Written by David Rich , November 30, 2011

    We are in contact with HK on a regular basis and will update our readers when new information becomes available

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    ARC Review
    Written by Johkan , April 23, 2012

    Dr. Rich,

    You referred to Anthem's Room Correction in your HK review and I was wondering if a review of that system was in the works

    John

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    ARC Review
    Written by David Rich , April 24, 2012

    Yes, a review is in preparation for the ARC system and the NHT subwoofer. The Anthem ARC is one of the room-correction systems that requires a PC. PC control which was highlighted in the SECRETS Best of 2011 Awards for Technologies on the Rise:

    www.hometheaterhifi.com/best-of-awards/1450-secrets-best-of-2011-awards.html?start=3

    ARC also won the Best Advanced Room Correction Firmware Award for 2011.

    Optimal correction to match a subwoofer's performance is one of the PC-control options in the ARC firmware. ARC proved readily compatible with the NHT subwoofer.

    David Rich

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    15" subwoofers, only?
    Written by JohnyBGood , May 13, 2012

    I just ordered this unit. I forget if I read it here, or elsewhere, but w/ 2 subwoofers connected the room correction EQ of the HK 990 uses more than one listening location for mic placement, thereby providing greater flexibility. Does that mean I have to buy 2 15" subwoofers to take advantage of this, since the HK 990 assumes I'll be using 15" subs? Or do I buy 2 subwoofers that go as low as 15" subwoofers (if so, what range am I looking for?)? Obviously I'm a bit confused. Thanks.

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    ...
    Written by David Rich , May 17, 2012

    When multiple mono subwoofers (all connected to the single subwoofer output port of a system with standard bass management) are optimally placed in a room, it is possible to minimize variations of the frequency response from seat to seat:

    www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White Papers/multsubs.pdf

    The HK 990 has a separate output for each mono subwoofer. With added signal processing, this permits greater freedom in placing the subwoofers, while retaining near-optimal performance.

    I used a 10 inch subwoofer when testing the HK 990. As outlined above, the unit did not work correctly for a woofer of this size, and I did not proceed to test the compatibility of the unit with two subwoofers.

    The test results suggest a subwoofer with bass extension to 20Hz should not exhibit these problems, but I did not verify this. In the two subwoofer mode of operation I cannot comment on the relative performance with different models of subwoofers that offer the 20Hz extension compared with matched subwoofers.

    The HK 990 requires three placements for the microphone with two subwoofers; with one or none, the microphone has a single placement.

    When opting for an expensive second subwoofer, consider purchasing an acoustic measurement system to see the frequency response at the listening seats and to ensure the subwoofers are placed so the system is minimizing variation of the frequency response from seat to seat. You will also be able to see if changing the subwoofer placements improves, degrades or has no effect on the result.

    The measurement system will also validate the crossover point, phase and amplitude of the subwoofers (figure 6 in this review). For the measurements to be accurate you must use spatial averaging of multiple microphone positions around each listener's seat (figures 20 and 21 in this review). The AcoustiSoft RplusD system used in this review has these capabilities.

    David Rich