We are still playing around with measuring amp power output and a procedure was not ready in time for the review so I don't have figures for you.
I can tell you that I was not able to drive it to audible clipping at any listening level which would not be a hazard to my hearing. This was with the nominally 8ohm Paradigm Reference Studio speakers, all bass sent to mains. When adding the sub and high passing all channels, like all amps, this one showed relief in the form of extra head room.
I'm trying to get my hands on some 4ohm THX Select speakers to see if it performs any different and will post back...
As we speak I've got the Onkyo driving the surrounds by itself and my Rotel THX Ultra amp drivng the fronts. It is sweet!
With regards to your specific question, I would not use the word "advantage". Rather, I would say "peace of mind".
A THX Select Speaker will have a certain minimum of efficiency and an impedance curve which stays above a certain threshold such that a THX Select receiver will have no inherent problem driving them to ref level in the size of room THX Select was intended for.
I recall John Dahl telling me about a dealer who called them up all angry saying that THX receiver such-and-such was shutting down (protection circuit) when the volume was turned up near reference. "Woa!" John said, "What speakers are you using? Are they THX speakers?". "Er...no" the dealer replied, "they are (brand/model name omitted)".
THX looked into into it and found that the speaker in question had a terrible drop in impedance, can't recall the frequency, but the drop was down to something around 1ohm. The dealer connected a set of THX speakers and the receiver was fine.
This does not mean that the non-THX speaker was "bad", nor does it prove that the THX ones "sounded" better, nor does it mean that only THX speakers can be used with THX amps (I've used my Rotel THX Ultra amp with every single speaker I've had through here). What it does mean is that when you have THX connected to THX, you dont have to worry about it.
The other "peace of mind" item when using THX speakers with a THX front end is that you know the crossover will be "correct". ALL THX speakers, both Ultra and Select, have their own natural 2nd order rolloff at 80Hz which compounds with the processors' 2nd order high pass to form a perfect 4th order high pass which perfectly complements the 4th order low pass to the sub. My Paradigm Studio 40 speakers are basically flat to 40Hz which mean that technically, I have too much upper bass in the 50-70Hz range. My mains should be down 24dB at 40Hz for a correct splice with the sub but they are not. They are only down 12dB.
You can "cheat" a little here because there are non-THX speakers on the market which have close to the right rolloff. At least with THX you can actually get speakers that "fit" the crossover. Consider Yamaha: they traditionally have used a 2nd order high pass and 3rd order low pass. Letter of the law says your speakers should have a 1st order rolloff at 90Hz. And if by chance you can actually find such a speaker, the phase response of the sum would be less than perfect.
I'm going to get a hold of a set of M&K's THX Select speakers for a couple reasons. One is to prove that the TX-SR800 can deal with the lower impedance (4ohm nominal), the other is to see how my bass will improve.
Brian: Saw this remote issue raised in your review, and I have a solution for this issue (the same problem exists on the remote for the Onkyo TX-SR700 -- which I own):
"The Onkyo remote makes one cardinal remote control sin: When in TV mode, the volume buttons control the TV's volume and not the Onkyo's. Imagine changing channels, changing the remote mode to "Receiver", adjusting volume, changing the mode back to "TV", changing channels again, and so on, all evening long. There needs to be a choice on the remote for whether A) the volume buttons are devoted to the Onkyo fulltime or B) the way it works now."
The way I fixed this was to take my Onkyo remote into the store (making sure I had my receipt with me in case someone raised questions) and then use one of the Onkyo remotes that were out with a display model (any recent Onkyo receiver remote will do -- doesn't have to be your exact model). So then while in "TV Mode" on my remote, I had my Onkyo remote "learn" the volume control (both up/down) from the display model's remote.
Now, when I'm in TV mode (and switching channels on my TV), I can control the volume on my Onkyo receiver.
You could also fix this by using any other learning remote that you may own. You could have the learning remote learn your Onkyo's volume control, then while in TV mode, have the Onkyo remote "learn" the volume controls that you just input into your own learning remote.
Good thing you raised this issue (I agree that it an odd thing that Onkyo does this with its remotes) -- but the workarounds I provide will get around that issue.
No, there would not be. 99% of speakers are designed to be as "full range" as they possibly can. Yet even if we know the low frequency extension of your speakers, that would not represent a magic value to set the Onkyo's crossover at.
If you were in the market for speakers, and assuming a subwoofer, you would be looking for models which are specifically designed to be high passed satellites such as all the models from M&K or Atlantic Technology (I beleive every single one of their speakers appoximate the 2nd rolloff at 80Hz I was talking about.
As you already have speakers, don't loose any sleep over this. Leave the crossover at 80Hz, balance all channels with a Radio Shack SPL meter, and just enjoy it.
I still hope companies take note and do better in the future. The remote that comes with the AVM-20 actually gives you the choice of those buttons being the TV volume in TV mode or "push through" where they are always the AVM-20 volume no matter what.
My own workaround was to just get my hands on a ProntoNeo which I wanted anyway.
Brian, the '800 looks really good, I wanted to clarify something in your review...
w.r.t. the Dolby 2.0 issue, I would like to leave my DTH receiver (Starchoice 401 navigo, Motorola...) on Dolby digital, and have 2.0 default to DPLII, (I understand the HK-525 will do this.) will the '800 only allow Dolby 2.0 to be outputed as 2 channel unless I intervene via remote everytime?
I'm so far quite sold on the H-K 525 due to it's flexible crossover (even though my Paradigm mini-monitors, CC-350 and Titans are pretty close as far as low-end response goes.)
For each input, you can set a default mode for each of the following signal types:
Digital Format 2ch (ie: 2 channel Dolby Digital)
Digital Format Mono (ie: 1 channel Dolby Digital)
So in your case, on the DSS input, you would set Dolby Digital to "Dolby Digital" (in other words, normal 5.1) and Digital Format 2ch to "Pro Logic II". Done!
FYI, I have mine set to THX for both which does the same thing only adds the THX post processes.
What I was talking about in the review is the Surr.Enc flag which so far only one SSP I know of reads (the AVM-20). The way Dolby originally envisioned the playback of 2 channel streems was for the authors to set the surr.enc flag if the content was to be Pro Logic decoded. In that way, a decoder would automatically chose Stereo or Pro Logic playback based on the flag. Its just one of those things that never really got used, both by hardware manufacturers and content creators. Its kind of cool to put in the Dolby Digital demo DVD and see the AVM-20 switch from Stereo to Pro Logic by itself when playing the two different 2 channel music demo tracks.
Good question though. Thanks for giving me a chance to clarify. I've just now revised that paragraph in the review to be more clear.
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