Product Review - Onkyo TX-DS989 A/V Receiver with THX Surround EX Processing - August, 2000

Colin Miller


TX-DS989 A/V Digital Receiver

Rated Power: 130 watts/ch @ 8 ohms, 2 channels driven, 20 Hz - 20 kHz; 130 watts/ch at 8 ohms, all channels driven, 1 kHz

THD:  0.05% at rated power

IM Distortion:  0.05% at rated Power

Damping Factor:  60 @ 8 ohms

Pre-out Voltage/Impedance:  1 Volt, 470 ohms

Frequency Response:  20 Hz - 30 kHz (DSP engaged),  5 Hz - 100 kHz (analog input, direct mode)

Size:  7 11/16" H x 17 1/2" W  x 17 3/4" D

Weight:  48.5 Pounds

MSRP:  $3,200  USA

Onkyo Electronics, web 


On the Newsgroups, one of our writing staff, Aaron Hodges, described his extreme enthusiasm when watching "Fight Club" with an Onkyo receiver. Although Aaron has had some difficulty getting a review sample of this new 6.1 product, I must admit that he's a continuous source for interesting commentary.  That moment of insight originated during a discussion of the Onkyo TX-DS989 receiver, equipped with not only Dolby Digital and DTS decoding, but THX Surround EX decoding as well, which derives an additional center surround channel from the discrete surround channels of encoded 5.1 Dolby Digital material and DTS "ES" material, DTS's "EX" equivalent.

What exactly is THX Surround EX, and how does the TX-DS989 benefit?

A processor that incorporates THX Surround EX (a 6.1 format instead of 5.1), aside from offering the standard THX features, also allows playback of 5.1 channel recordings with 7 channels in addition to the subwoofer, compared to the 5 channels inherent to standard 5.1 recordings.  The two extra channels, as mentioned before, are not discrete, but rather are derived from matrix decoding the discrete surround channels, just as Pro Logic derives a center channel from the Left and Right front channels. EX derives a center surround channel, and then sends that information to a pair of speakers after bass management and time alignment.

The correct terminology is THX Surround EX, rather than Dolby Digital EX. DTS also has its version of this, and it is called DTS-ES.

The TX-DS989 addresses the decision to implement EX either on a manual or automatic basis.  The Auto setting looks for a flag in the DVD's data stream, but as of the writing of this article, no DVD has such a flag, so during the audition, I had to set it to Manual.  EX decoding itself does not absolutely require EX-encoded material to work.  Like Pro Logic with non-encoded material, the results will vary depending on the original mix.  All there needs to be is stereo information in the surround channels, with some info common to both channels.

Why two channels with identical material?

THX mandates two rear surround channels (in the THX paradigm, the two surround channels are actually to the sides) for two reasons.  One is that some processors will send the discrete surround information to the rear channels when not operating in EX mode, so that two rear channels are required for standard playback of what we used to call the rear surround channels.  Sending the discrete surround information to the rear EX channels as opposed to the side channels in a full THX system where dipolar surround speakers are supposed to be placed to the side seems rather contradictory.  However, in this regard, the Onkyo TX-DS989 is somewhat flexible, in that the user can set up the surround information to route to either the "side" surround channels, the "rear" surround channels, or both.  If one wanted to, one could route regular surround information to the original "side" surround channels, and leave the "rear" surround channels exclusively to EX duty, so that a single EX channel is plausible.  This method isn't quite as preferable as the one used by some processors, such as those made by Meridian and Lexicon, that default to generating a 7.1 mix by deriving side channels by matrix decoding the surround and front channels, but getting into such products will cost about twice as much, and they require the additional expense of outboard amplifiers as a necessity rather than a luxury.

The second reason for THX's mandate of two EX channels is based on THX's goal of relatively diffuse surround information.  While the extra EX channels do allow more directionality compared to the original THX surround array of two dipolar speakers to the side, which allowed NO directionality from the rear, the two EX channels do not create precise steering, particularly if implemented with the dipolar surround speakers as specified by the current THX Ultra standard.  That is not to say that a person must use dipolar surround speakers to take advantage of EX decoding, or even that either dipolar or direct-radiating speakers are more correct. 

Is there a real benefit to more channels?

While I'm sure that most manufacturers in the audio/video industry wouldn't mind anything that simply prompts us to buy more stuff, the psycho-acoustical truth is that five channels are simply not adequate to maintain consistent front/side/rear directionality while also maintaining a smooth transition between all channels.  There are crafty methods, such as M&K's "Tripole" surround speakers that have essentially both dipolar and direct radiation patterns, using multiple pairs of surround speakers, or placing the surround speakers somewhere to the side and slightly behind while using the ceiling and rear wall to diffuse the sound.  

The original THX solution of de-correlation and nullifying direct sound by side-placed dipoles addressed the inability of Pro Logic's two mono surround channels to create an ambient sound field, but severely sacrificed the ability of a system to localize any surround content.  The 5.1 formats like Dolby Digital and DTS, when used in conjunction with the THX dipolar side surround array, did allow some directionality in terms of left to right in the surround field, but in terms of front to rear directionality, the original THX loudspeaker array could only portray front to everywhere else.  If the goal was to keep all surround information, regardless of source, ambient in nature, the original THX paradigm worked fine.  However, if you wanted the ability to reproduce sound from over the shoulder, you were still out of luck.

With the advent of 5.1 formats, and discrete surround information, the use of direct radiators for surround channels behind the listener COULD put sound behind the listener, and did a better job creating an ambient surround sound field than with mono surround information, but it could still not completely envelope the listener as the proponents of THX wished.  To create a solid sound field behind the listener,  the speakers behind the listener sacrificed the blend with the front speakers, and while moving the speakers to the side improved the transition from the front to rear channels, the rear channels were no longer in the rear, and a gap behind the listener reappeared.  And so, to address the short-comings of both situations, we have EX, which may benefit both dipolar and direct-radiating loudspeakers alike.  That EX decoding can provide better performance than simple 5.1 formats is not in question.  Whether the decoding will rise to dominance on the verge of possible discrete 6.1, or 7.1 formats remains a matter to be decided. 

In terms of the EX comparison . . .

Like Pro Logic, one can decode non-EX encoded 5.1 material by engaging the EX mode.  It seemed alright to me with the DTS "Antz" soundtrack, even though it was not officially "ES" encoded.  It was therefore not "correct", but really a matter of personal preference.  Though the effect was not as dramatic as when EX was engaged with "Fight Club" (an EX-encoded DVD), it still lent more of a wraparound effect.  Be warned, though, that the results of EX-decoding non-encoded material, like Pro Logic with "normal" stereo content, will be haphazard. Sometimes it will sound good, but other times it may sound terrible.

With "Fight Club", once I repositioned my surround speakers to make use of more channels, the use of EX decoding provided both a better transition to the front, and a more wrap-around effect.  Specifically, voices in the background could emanate from behind, or the side, depending on the movement of the observer.  And, during my favorite scene, the airplane collision, the disaster unfurled around us without sacrificing the realness of direction.  I LOVE IT!

About the Onkyo TX-DS989!

What's special about this unit, aside from having the latest from LucasFilm?  How about D/A converters capable of handling 192 kHz sampling rates, and 24 bit data?  There isn't much material actually recorded at 192 kHz and 24 bits, but DVD-A seems to be on the verge of lifting its little head, and the 989 is ready (even though the first players will not output 192/24 bitstreams).

The TX-DS989 also utilizes the Crystal SRC (Sample Rate Converter) chip that, although it can't increase the real resolution or bandwidth of the information feeding the DACs, may decrease the requirements of the DAC's reconstruction filter by upsampling the digital audio into a higher sampling rate.

A feature about the Onkyo's upsampling that I appreciated is that it upsamples to an integer of the original sample rate, i.e., 44.1 kHz to 88.2 kHz, and 48 kHz to 96 kHz, as opposed to some products which upsample unilaterally to 96 kHz.  Something to remember about upsampling is that it cannot put back information that was lost.  If the upsampling occurs at a direct integer, the upsampling creates new samples in between the original samples, calculating estimated values based on some form of interpolation and a low-pass filter, which in turn makes following DSP and analog filters that much easier to implement.  However, aside from the non-integer-based upsampling method requiring more DSP power to generate upsampled values, upsampling to a rate that is not a direct integer of the original sample rate requires that the interpolation algorithms create ALL of the resulting samples, which means that without infinite processing power and bit length, the upsampling process LOSES information.  Because of this, I was thrilled that Onkyo chose to adopt the simpler and superior upsampling method.

The 989 has a heap of inputs and outputs including composite, S-Video, Analog audio, digital audio, RF modulated digital audio, and three component video inputs), assignable digital inputs, a 7.1 input via DB-25 connector, preamplifier outputs for all channels, outputs for a secondary zone, rear IR ports for both zones, an RS-232 port for purposes of both control and upgrades to accommodate future formats (only through dealers for the time being), a slot for a future expansion card for possible IEEE1394 (FireWire), and a way cool motorized drawer.  In a changing digital world, the last two a very big pluses.  One should note that the DSP processing power is finite, so that the TX-DS989 is not upgradeable indefinitely.  But, at the present time, with current software, it's only running its chips at half speed, so there's some room in the toes for growth. The 989 as supplied will not decode DTS Discrete 6.1, DTS Neo:6, or Dolby Pro Logic II. Only time will tell if it is upgradeable with some sort of software downloads through the RS-232 port and flash memory (4 MB).

Aaron on line mentioned that the TX-DS989 lacked a 12 volt trigger output to turn on outboard amplifiers, but considering the presence of switched outlets, and the abundance of inexpensive AC/DC converters available in a variety of voltage outputs, that's not much of a concern.  What may be of concern is that the switched outlets, like voltage trigger outputs of many other components, turn on and off simultaneously with the receiver's power state, so that a shift into standby might cause a rather annoying pop if the amplifiers aren't otherwise muted.  I let the Onkyo switch my subwoofer amplifier by using the switched outlet as a trigger, and once the pop got through the low-pass crossover, it became merely a thud, but the other amplifiers remained switched separately via an IR-controlled relay for this very reason.  Man, am I just itching for my own AMX control system!

The configuration capabilities of the receiver through the menu are powerful.  Aside from setting different RE-EQ and subwoofer inclusion defaults for different surround formats, the TX-DS989 also allows variable delay to sync up audio with video content, sometimes delayed due to video processors.  Re-EQ may be enabled or disabled on the fly from the remote (which is of the learning variety . . .  yippee!).  Brian Florian will appreciate that bass management sends low frequency content to both large main speakers, AND the subwoofer channel.  (If you missed his article on the myths and realities of the 0.1 LFE channel, you can't afford to, so go read it, and then come back! Click HERE.)

The TX-DS989 also has a bunch of DSP modes for those who like to play.  For non 5.1 material, I thought the Enhanced 7, Orchestra, and Studio Mix modes useable, though not necessarily superior to straight stereo playback (if seated in the correct listening position).  Like many DSP packages, most of the others were a bit gimmicky.  There was one that put stereo to all channels (mono for the center) for the sake of background music that I can see using for entertaining, but not serious listening.

More is better . . .

The most telling feature of the receiver is that it's fairly heavy, listed at 48.5 lbs.  For a mass market product, that's substantial.  And, unlike some DVD players that I've run across recently, the bulk of that mass does not consist of useless filler material for enhancing the perception of build quality.  

There's not much in terms of heat sink area, but there are two fans, one on each side of a heat sink tunnel. They were audible to the extent that you might hear them turn on in a quiet room if the receiver were not in an enclosure of some sorts, but I doubt anybody would notice them in the middle of an action movie.  In my case, everything but my CD player, VCR, and television sits in an adjacent room, so it didn't bother me a bit.

I couldn't get at the caps to measure the rail voltage, but with a 119 AC line voltage feeding in, the secondary taps (one for each rail, and a ground) have 43 volts rms running across each tap to ground. That translates into 60 volts DC. With 44,000 F of storage capacitance, that's 79 Joules, a lot of storage for a receiver. The transformer looks big. It's covered, but the main line is fused at 12 amps. Assuming that it's fused to protect even at 120 volt line conditions (probably more), we're probably looking at something like a 1,600 VA transformer, which is pretty big for a receiver. 
Now, figuring roughly that the transformer is good for about 75 % of the VA rating in terms of power, that means that the power supply can source about 1,200 watts, total. Take a hundred off for the computer processing and preamplifier stages, and we've got 1,100 guesstimated watts to play with for the output stages.  One hundred thirty watts per channel, with seven channels, would require 910 watts at output, after the amplifier stages. So, we're still talking feasible. That leaves  roughly 28 (1200/43) useable amps on a good day, to go between all of the channels (I'm giving it the benefit of the doubt by no longer subtracting any power for the processor.) Twenty-eight divided by seven is four amperes per channel. The reason I am getting into this issue of power with the Onkyo is that the spec sheet lists the power output with all channels driven, at 1 kHz. This strays from the standard spec of listing power with all channels driven, at 20 Hz - 20 kHz.

As a matter of comparison, my Aragon 8008BB can put out 20 amps into each channel, two channels at a time, if the AC line voltage will permit. At 8 ohms, figuring ohms x (amps)2, we're looking at a maximum continuous output at all seven channels of roughly 130 watts each.  So, it is believable that this receiver could meet 130 watts/channel all channels driven, but just barely, and since below 8 ohms, the current is the limiting factor at 8 ohms, not voltage, in an all channels driven situation, full power output will decrease as impedance drops.  Under the unlikely situation that all channels are going full tilt, the receiver isn't likely to put out more than 65 watts per channel into 4 ohm loads under such circumstances.  

Now, before we get all discouraged, keep in mind that with a lot of rail voltage, a bunch of storage capacitance, and a shared power supply, that any channel, or even a couple, could take advantage of what any others aren't using. In the real world, it's unlikely that all channels would be going full blast at any given moment anyway, and if they did, it's likely that the storage capacitance could float what the transformer couldn't for a while. Two channels could make use of that power supply, and with 14 amps to their name each, could handle lower impedances with ease, assuming the output devices didn't blow up.

While this whole discussion is theoretical based on cursory observations, what the examination implies is that this receiver is optimized to drive all channels at higher impedances (specifically 8 ohms), but if the demand falls onto only a few channels at a time, as is usually the case in real world use, lower impedances should not be a problem. Matched with a good three-channel outboard power amplifier for the front channels, the output capabilities for the surround and EX channels can be absolutely sweet.  While the TX-DS989 will not necessarily surpass the performance for your favorite outboard amplifier by itself, it will prove entirely adequate for driving a wide range of loudspeakers to reasonable output levels.  Though the amplifier section is not rated for 4 ohm  loads, it did handle a full load of seven various M&K satellites simultaneously, all of which present at least a 4 ohm nominal load.

Compared to the giants . . .

During the fantasy airline collision in "Fight Club", with the 4 ohm M&K MPS-2510 monitors in front, as well as the S-85 and older S-80 satellites, the 989 could elicit a slight edginess at higher listening levels (but still within the range of sane levels), which the resident outboard power amplifiers managed a yawn to acknowledge.  I must qualify, it sounded REALLY GOOD for a stand alone receiver, possibly the best I've experienced in that regard yet!  With various musical material, specifically Sinead O'Connor's "Universal Mother" and Mars Lasar's "Eleventh Hour," compared to the outboard amplifiers used for reference, the onboard amplifiers of the TX-DS989 maintained a good level of detail , but sacrificed just a little ambient subtlety and richness with a tint added treble energy.

 For a receiver, the power supply has some meat, and the sound reflects that.  Still, it's still a far cry from a large, dedicated outboard amplifier, or two, or three for that matter.  However, matching the amplifier section in a receiver up with a collection of dedicated amps that can concentrate their entire average budget of about a grand per channel into a single task isn't really a fair comparison. The square wave response (10 kHz 10 volts) is good, and the bandwidth ( - 3 dB) is 75 kHz.

Okay, well let me say that at what I would consider sociable listening levels, the amplifier section remained stable and an easy listen, even when not driving the most efficient loudspeakers.  That's something most mass-market receivers can't lay claim to. Going full steam, the cooling fan kicked in regularly, but discretely, and the black box never shut down.  Applause!  And, if something such as a decent three-channel amp were to help make ends meet, performance could only get better, from any direction.

Compared to the common man . . .

As any product that costs more than twice as much as another should, the Onkyo TX-DS989 substantially exceeded the performance of the Yamaha RX-V995 receiver ($999).  I don't mean to imply that the more expensive Onkyo made the relatively affordable Yamaha sound bad by any means, but that the positive difference may certainly justify the extra expense to some listeners.  The onboard amplifiers had an easier time with the moderately difficult M&K speakers, and even without the EX decoding, the Onkyo managed a smoother presentation, more layered depth portrayal, and a slightly greater degree of transparency.  I stand by the Yamaha RX-V995 as an outstanding receiver for less than a grand, but must concede that spending more than double on the TX-DS989 isn't a concept that should be reserved for only the most obsessive enthusiast.

We could use it as it was intended to be used, but . . .

If only because of the fact that I've got some nice big amps and I like to use them, I spent the majority of the time using the Onkyo to power the rear EX channels exclusively, or not at all, and let my current collection of outboard power amps engage the cruise control.  Based on that experience with Dolby Digital, DTS, and conventional PCM soundtracks, while I wouldn't stick my head so far out as to say that the TX-DS989 may equal the best surround preamp/processors available, it's not too far behind.  Dare I say musical?  I dare.  I'll even volunteer super duper.  

I would voice a note that the voltage output capability of the preamplifier section listed in the manual is low, so that one should take it easy on any trim pots preceding an outboard amplifier, but under most circumstances, the voltage output should easily suffice.  With trim pots engaged down the line to keep my ears safe, I pushed the volume setting to maximum without any audible problems.

At the moment, the top of my surround preamp wish list is the Meridian 568, perhaps tied to a 562V.2 if I feel ambitious.  However, if the Onkyo TX-DS989 happened to make an extended stay until that far off day, I can't say that I'd be disappointed.   Though it's not a 568, or even a Lexicon DC-2, I would feel comfortable exposing my neck enough to state my opinion that the TX-989 will equal or out-perform many "high-end" dedicated preamp/processors at the same price or even some that are higher.  Considering the inclusion of useable on-board amplifiers to sweeten the deal, I might even qualify it as a bargain.  Were I not devoting my financial resources almost exclusively to day care, a mortgage, and the costs of a late-August  wedding, I'd buy it right now!

At least I can take consolation that it won't be go too far away.  Aaron's place is just over the bridge, and apparently he appreciates the Onkyo TX-DS989 as much as I do, because once I can bring myself to let it go, it's still not going back to the manufacturer just yet.

- Colin Miller -

For the record, components used during review:

Aragon 8008bb Stereo Power Amplifier
Aragon 8008x3 Three-Channel Power Amplifier
Sunfire Stereo Power Amplifier
Meridian 558 five-channel Power Amplifier

Yamaha RX-V995 Receiver
(3) M&K MPS-2510 Professional Monitors (Pro version of S-150THX satellites)
(2) M&K S-85 loudspeakers
(2) M&K S-80 loudspeakers
(2) NHT 1259 - based subwoofers, powered by a...

Dynaco ST-400 stereo power amplifier
JVC XL-Z1050 CD player
Toshiba 2109 DVD Player

Bybee/Curl Prototype AC Purifiers & Power Cords
M'Dor Power Cord
DH Labs Silver Sonic Interconnects, WBT RCA connectors
AudioQuest Diamond Interconnects
Liberty Emerald 14-4 Speaker cable, custom-terminated.

Copyright 2000 Secrets of Home Theater & High Fidelity
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