[buns]

The more i read on various websites, the more i get the feeling that before too long everyone in the amp/processor market is going to be having a pop at some room equalisation features, be they good or bad.

I was just wondering what brystons stance on this is? Is this a feature which is being considered?

thanks!  

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[James Tanner]

Hi AD,

No plans - equalization has serious negative issues in my opinion.

james

[buns]

Ah right, that is interesting! So are you in disagreement with an equalised sub sounding better than a non equalised one? There just seems such an enormous number of people doing this and so many people claiming it is the bees knees!

So in the absence of a properly acoustically treated room, do you suggest forgetting about any equalisation?

You might be saving me more money!

Thanks!

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[James Tanner]

Hi Ad,

The problem with equalization of any kind is that it only works in a specfic part of the room. So that is OK in some circumstances where the listening window is very narrow. In the sub area it is less objectionable because the ear is much less sensitive to these issues but in the uppper bass and mids it can cause serious problems I find.
The main issue is that speakers should have a good Power response throughout the room and equalization I find reduces that goal. I have always found the the dynamic range also suffers when you use equalization.
I am a big believer in positioning the woofer properly in the room to provide maximum flat power response without the use of equalization.
I have a number of Newsletters I have written on the Bryston Webste on speaker placement which you might find interesting.

[buns]

Thanks James, I will check that out

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[nicolasb]

I agree that Room EQ is something that should be applied only after you've explored positioning and room acoustics options. I also agree that correction in the frequency domain is usually better restricted to the subwoofer range - above that level the room modes are usually going to be close enough together that there won't be any huge holes.

But I think that parametric EQ on the subwoofer channel has a lot to be said for it, and I think it's a shame that you've ruled out the idea. I'm sure a future SP1.7 model would do a far better job of it than the Behringer Feedback Destroyer I'm probably going to end up using....

And once you go a generation or two farther, and start thinking about room correction in the time domain rather than just the frequency domain, things really get interesting. I've never had the chance to listen to a TACT setup, but the reports I've heard is that is absolutely stunning - really does make the sound independent of the listening room.

[James Tanner]

Hi nicolasb,

I have heard the tact and it has the same issue of either being set up for a specific location or a wider listening window but less correction.
The real problem with all this is that the ear/brain hears the 'totality' of the energy in the room - the direct as well as reflected sound - this is called the power response.
All these correction systems screw with that because they are forcing a flat response at the specific location of the measuring microphone at the expense of the rest of the room.  
I agree that doing it in the low frequencies is less objectionable but I find the bass does not sound correct. It has a dynamic restriction to it in the experiments that I have run.
Maybe as the techology improves it will get better but so far I am not impressed.

james

[buns]

Well having played just with positioning in my room..... i have to say that im finding that the whole things is very position specific even without having equalised in any way.

Oh and those articles are a great starting point Thanks.

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[thomaspf]

Hi,

I assume there will be no objection if I ask a couple more question about the SP1.7 future.

1. Firewire with support for DVD-A and SACD
I assume this is just to early since the standards are just now being implemented in receivers. However, when further investing in this component I would like to know what the general direction is. Is Bryston tracking the market development on this or is this out of the question?

2. Dejitter circuit
I am pretty happy with my unit as it is. However, I have bought an external dejitter box to interface it to my PC in order to deal with the bad digital signal coming out my sound card. It seems that the clock for the SP1.7 DACs is slaved off from the clock of the incoming signal. This is even true for encoded streams. On the recent BP25DA and the integrated amp Bryston uses an asynchronous sample rate converter to decouple this but this does not work on encoded signals since it does not preserve all bits. Are there any plans to upgrade the SP1.7 with a buffer based dejittering scheme (like Meridian)? I understand this introduces new issues with lip sync but I assume this is not worse with what I have now where I loop in a dejitter box in the digital path anyway.

Cheers

     Thomas

[James Tanner]

Hi Thomas,

Yes we are monitoring what is going on in digital connections and interfaces and as soon as it settles out we will certainly provide a retro fit for the SP1.7.
I will pass on your 2nd question to Shane our digital engineer for comment. He just left on a 3 week holiday so it will be a while before he gets back to you.

james

[thomaspf]

Great, this is good news. So I can basicaly wait and buy a cheaper universal player with firewire out for DVD-A/DSD and still get great sound when you guys come out with an upgrade.

Since the CS43122 does not support DSD I assume that will mean completely new DACs and controller as well?

Cheers

   Thomas

[nicolasb]

I agree about the likely benefits of being able to buffer and re-clock an incoming digital signal. This would be particularly useful with PCM.


Other things I would like to see (but am, on the whole, not holding my breath for! Most would require major hardware upgrades).

• Dolby Headphone output (requires a DSP upgrade, I am told).
• Support for a height channel.
• 192kHz support.
• Support for more than one subwoofer, especially the ability to separate the LFE channel in x.1 sources from bass management.
• (As discussed in a previous email with James T, but I'll post it on here because I'm curious to see if anyone else finds it interesting...) The ability to output a (potentially downmixed) stereo analogue signal at the Tape/VCR inputs when using a digital input signal.
  
  
• The licensing of some interesting DSP modes. I have little time for the "church", "party", "disco" stuff, but some DSP algorithms really do make a positive difference. The "Logic 7" algorithm (as used by Lexicon) would be a very fine addition for movie use. So would the "Trifield" algorithm (as used by Meridian, although they themselves license it) for stereo sources.
• Some interesting (proprietary?) up-sampling algorithms.[/list:u]

[thomaspf]

Well, since you ask.. I would not fall for any of your features.

However, if Bryston could lower the noise floor in the SP1.7 to the same level as the BP25 or a Halcro DM10 for $1000 that would make me buy an upgrade immediately

The THD+N rating of 0.006% for the internal DACs is somewhat anachronistic even if it spans the full frequency range. That is basically 14 bit resolution! It is very puzzling that the analog bypass measures better than the internal DACs.

I am not complaining, just putting this in context to let's say an Accuphase DP-77 with a THD+N rating of 0.0008% over the full frequency range.

Cheers


Thomas

[James Tanner]

Hi All,

One point I would like to make is that the sound (not meassured)difference in digital systems we find very small compared to the analogue sections in most DVD/CD/Processors.
The unique design feature in the SP1.7 is the way the analogue signal is handled. All processors we have looked at use 'gain' in the digital circuits or IC's for amplification of the signal. Bryston does not. The dicital IC's are run at 'unity gain' and all amplification is done using fully discrete Class A  operational amplifiers. The difference in dynamic range and sound quality is not subtle.

james

[nicolasb]

Thomas,

as many loudspeakers are doing well to get below 0.5% THD (and many subwoofers struggle to achieve even 3 or 4%) I'm not entirely convinced that the difference between 0.006% and 0.0008% is actually audible in practice.

I'm not saying that there isn't an audible difference in quality between different audio products, but I would question the extent to which the quoted THD figure is a useful measure of that.

If we consider power amplifiers, for example (which I know slightly more about) I'd be much more interested in slew rate and settling time than THD (and even more interested in how it handles sudden low-swings in speaker impedance).

[thomaspf]

As I said, I am not complaining about the sound but merely pointing out that there is some room for improvement in the digital section.

If the analog bypass can produce these low noise and distortion values I have to assume that I could get better quality by buying an external DAC. That is strange given that I would run the signal through 2 more connectors and a cable.

I propose that the analog section should be the botteleneck for this since the latest generation DAC chips provide -110db THD+N at their outputs. Even the CS43122 sits at -102db THD+N. Maybe a dual differential circuit or other tricks in that direction will get you there.

Since we are talking the processor and not speakers or amplifiers I won't pick up on the other comments.

[thomaspf]

Here is another request that bugged me for the longest time. I do understand that SACD and DVD-A are the wave of the future but I would still like to see an HDCD decoding feature.

This looks like a rather simple additional detection and decoding step and the code can be directly licensed for the Motorola DSPs. It comes down to whether enough people would be willing to pay extra for this so that the development cost amortizes.

James, have you ever considered this?

Cheers

    Tomas

[James Tanner]

Hi Thomas,

Yes there seems to be a 'critical mass' when it comes to these different formats as to whether they get implimented or not in the DSP's. I can not say the request for HDCD has come up from our customers so far.

james

[jethro]

I think it might be nice to have the option of routing the SP 1.7's built-in test tone thru bass management, or not. I have a passive sub without an external crossover attached. A few times I have mistakenly run the full-range built-in test tone thru my sub and scared the crap out of me. I use the AVIA DVD now but a more flexible buit-in test tone might be nice.

--Steve

[James Tanner]

Hi Steve,

If you say 'Sub - No' in the SP1.7 menu before you run pink noise it will remove the tone from the sub for you.

james