Multi-channel input option on Orelo

[briefremarks]

All,

Wondering if anyone has tried/used the multi-channel option on the Orelos. Want to clarify a few points.
- With the input selected for "multi-channel" are the inputs expecting line level signals for bass, mid, and high?  Or are inputs speaker-level inputs that bypass the amps in the Orelo?
- Is the internal DSP bypassed?
- Is the internal passive cross-over for the BMS driver also bypassed?

Thanks,

Ramesh

[PeterSt]

Hi Ramesh - Good questions.

With multi channel input, what's expected is "speaker" level.
(btw, as far as I remember, you already used similar via "External Amp" for your Home Theater setup ?)

With the External Amp setting, all filtering remains active, but it is set up differently;
The filter "between" (as you call it) mid and tweeter normally is an active filter (controlled by two internal power amplifiers). When you use your own external amplifiers, that filter (the filter towards the mid and the filter towards the tweeter) are fully passive.

With "External Amp" the DSP remains active, however, the bass amps also remain active.

Now :
With Multi Channel, all filters are bypassed. The DSP for the bass also is bypassed, so you must provide your own DSP as well.
What this comes down to, is that with the Multi-Channel usage, you must provide your own filtering all externally. Regarding this, please notice that the design took the explicit standpoint that "ever" there would emerge a DSP with sufficient power (meaning : resolution) to also take care of the mid and high ... which back at the time I "forbid" with the too low sampling rate ADCs in order.

In order to understand the latter a but better, think of the situation that you could also take passive filters for mid and high (read : for the Orphean top horn) which would theoretically available from BD-Design in the form of an external box. This would be similar to the internal filtering and the "External Amp" setting, but surely not the same (the internal filtering was merely developed *) by me and my listening to the very Orelo MKII, while the externally available filter was developed by Bert and his listening on different type(s) of speakers).

*) : This is a large word, because the original base has been a development by Bert (I wouldn't have known where to start ;-), as how this was done for the Orphean Horn, when Bert created that. However, right from that start I myself further developed that filter (over a time span of many years) while Bert at some stage went his own route with it (and this own route already appeared in the first commercial speaker - the Swing). So I kept on developing the original filter and this continued with the Orphean.
This summarized : Obtaining the external pair of boxes from BD-Design would give you a head start, but it would not be to my liking at all. OTOH to be honest, while Bert never worked on his filter for the Orelo MKII (original Orelo MKI yes !!), I never listening to his filter (MKV IIRC) on the Orelo MKII. Why not ? .. it requires external amplifiers (haha).

To be continued in a next post ...

[PeterSt]

Many times I have been deliberating with Bert to replace the Hypex DSP with something like from MiniDSP.  And let's say that it never happened because of a lack of time or inspiration. Btw regarding the latter, like I think most people owning the Orelo MKII, I don't feel the slightest need to improve something. However, there's this awkward Hypex DSP in there (failing quite often for I think by now everybody) ...

Now please notice : The MiniDSP does not fit in there. So this holds back too. Other brands exist as well, but in all events it won't "just fit". So ... have it external ?

And this is exactly how I may start to be enthusiastic about the idea of the external amps and an "upgrade" to an external DSP. And please keep in mind : this upgrade has always been an explicit plan. But nobody really started about it, including myself ...

Assumed that the DSP of choice (could be any, when outboard) is of sufficient high quality (superb quality, actually), I think that the net result could surpass the current result vastly. I mean :

All of you use the NOS1a/G3 DAC in front of the Orelo MKII. But with a DSP like (possibly) proposed, this means
A/D
and back to D/A via the DSP itself.
This should lose the "quality" of the NOS1 ...
But what you'll get back is the bypassing of a mile of internal speaker wiring. Of course this has been set up carefully, but still there is all these wires. They will all be avoided.

So see ? it is not easy to get motivated for this, because you kind of know what you will lose (the NOS1's quality). And what you will get back can not really be estimated ...

...

A strict reason not to dive into this earlier, is the sheer fact that the DSP should be done in software. Thus, in the PC. Now there's no A/D in order and you can just use your NOS1's. Yes, indeed "1'ssss". Because you will need 3 of them. Or actually 6 channels of it.
This is how the NOS2 came into play, ever back. But that project was too large and failed.
Anyway, when the DSP is done in software, no additional A/D stage is in order and theoretically it is the best. But what comes from that is again an other DAC (6 channels all together). And still it would be difficult, because when we'd like to use that with 16x upsampling like we do today, there's no USB interface being capable (I think the fastest would allow for 4 channels, unless there's a USB3 audio interface available).

...

Net, the DSP solution between the two channel DAC and the power amps (6 channels of it) would be the only feasible option. Thus :

DAC -> DSP-6ch -> 6x Poweramp.

or

Turntable -> DSP-6ch -> 6x poweramp.

Regards,
Peter

[briefremarks]

Thanks Peter.  This explains many things, and also what options are possible.

Quick questions:
- I've always assumed that the filter between mid and high was passive.  This is the first time I realize that it is an active crossover.  Is this an analog circuit? I'm assuming no DSP or A/D conversion is done.
- The above makes me ask another question.  If the filter between mid and high is an active analog filter, is there an option to do something like this for use with the multi-channel option: essentially use an analog  crossover after the NOS1.  Would this cause less degradation of the NOS1 sound?

Ramesh

[PeterSt]

- I've always assumed that the filter between mid and high was passive.  This is the first time I realize that it is an active crossover.

The "Crossover" is nothing more or less than two filters, one with a roll off to the upper frequency range (for the mid) and one with a roll off to the lower frequency range (for the tweeter). Of course there is more to be filtered, like the bottom of the mid (also crossover) and the upper of the tweeter (protection). And besides and maybe merely : make the frequency response more smooth than the horn normally (acoustically) allows for without aid.
The "active" part is in this latter and it only serves 3dB of more efficiency (without this feature the efficiency of the Orphean would be 115dB - now it is 118dB). So this is why two amplifiers are in order - one is to boost the tweeter more than the mid, so the inherent dip in the tweeter is now smoothed by filtering down all but the dip. I name this an "active" application because it is an amplifier which does something additional to the tweeter. In the end it is part of the filtering, which, as said, also is for smoothening bumps. Dips can't be smoothened - they need to be amplified (which is what in net comes down to in this case).

With outboard filtering the efficiency goes down by said 3dB or else this dip is there (bad for SQ of course). In the end there is thus also a different relation between mid-high on one side and the bass on the other (bass (also) needs to be attenuated by an additional 3dB if the active filtering is not present. Not that you would notice for real with the multi channel setup, because it would be one pile of "settings" anyway.

If the filter between mid and high is an active analog filter, is there an option to do something like this for use with the multi-channel option: essentially use an analog  crossover after the NOS1.  Would this cause less degradation of the NOS1 sound?

Theoretically this would be possible (if I am not mistaking) but whether it is worthwhile ... I doubt it. You (or someone else) would need to design the whole lot which thus starts with the normal filter part itself (think years of work). Notice that this has *not* been done inside of the Orelo because that is a high level filter (Speaker Level) with different components and very different impedances (all reacting differently than how they do now). It would be true, however, that there's not the downside of the additional A/D - D/A.

So this is
DAC -> Filters (Line Level) with 6ch output -> 6x Poweramp.

Thinking this over for a bit, I think it should exist - at least from older days when DSP was not available yet, but Line Level filters were (Speaker Level filters wouldn't exist anyway, IMO). I think I recall devices costing 4K or so. And they would really be active (with OpAmps).
Maybe this is far more normal than I am currently contemplating. Hmm ...
Didn't Linkwitz carry something like that ... (don't laugh now because in that case this is how you got the idea in the first place - right ?)

Peter

[PeterSt]

- I've always assumed that the filter between mid and high was passive.  This is the first time I realize that it is an active crossover.

The "Crossover" is nothing more or less than two filters, one with a roll off to the upper frequency range (for the mid) and one with a roll off to the lower frequency range (for the tweeter). Of course there is more to be filtered, like the bottom of the mid (also crossover) and the upper of the tweeter (protection). And besides and maybe merely : make the frequency response more smooth than the horn normally (acoustically) allows for without aid.
The "active" part is in this latter and it only serves 3dB of more efficiency (without this feature the efficiency of the Orphean would be 115dB - now it is 118dB). So this is why two amplifiers are in order - one is to boost the tweeter more than the mid, so the inherent dip in the tweeter is now smoothed by filtering down all but the dip. I name this an "active" application because it is an amplifier which does something additional to the tweeter. In the end it is part of the filtering, which, as said, also is for smoothening bumps. Dips can't be smoothened - they need to be amplified (which is what in net comes down to in this case).

With outboard filtering the efficiency goes down by said 3dB or else this dip is there (bad for SQ of course). In the end there is thus also a different relation between mid-high on one side and the bass on the other (bass (also) needs to be attenuated by an additional 3dB if the active filtering is not present. Not that you would notice for real with the multi channel setup, because it would be one pile of "settings" anyway.

If the filter between mid and high is an active analog filter, is there an option to do something like this for use with the multi-channel option: essentially use an analog  crossover after the NOS1.  Would this cause less degradation of the NOS1 sound?

Theoretically this would be possible (if I am not mistaking) but whether it is worthwhile ... I doubt it. You (or someone else) would need to design the whole lot which thus starts with the normal filter part itself (think years of work). Notice that this has *not* been done inside of the Orelo because that is a high level filter (Speaker Level) with different components and very different impedances (all reacting differently than how they do now). It would be true, however, that there's not the downside of the additional A/D - D/A.

So this is
DAC -> Filters (Line Level) with 6ch output -> 6x Poweramp.

Thinking this over for a bit, I think it should exist - at least from older days when DSP was not available yet, but Line Level filters were (Speaker Level filters wouldn't exist anyway, IMO). I think I recall devices costing 4K or so. And they would really be active (with OpAmps).
Maybe this is far more normal than I am currently contemplating. Hmm ...
Didn't Linkwitz carry something like that ... (don't laugh now because in that case this is how you got the idea in the first place - right ?)

Peter

PS: Plus you'd own it already unless you sold it ...

[PeterSt]

And they would really be active (with OpAmps).

Which will imply THD.

[briefremarks]

Yes, you are correct.  I got the idea from the Linkwitz analog signal processor (ASP) which I still have.  The reason I mention this is that I have listened to the Linkwitz using a DSP vs the ASP, and the ASP sounds better to me with essentially the same transfer function for DSP and ASP.  And yes, a lot of op amps!!

[briefremarks]

Peter,

One question after re-reading your note.  With "External Amp" input selected, is the external amp only driving the mid and high--in other words the horn driver.  Are the woofers still being driven by the internal amp?

Ramesh

[PeterSt]

Hi Ramesh,

Yes. As far as I know from the design ...
(but I never really tried myself ...)

Peter

[briefremarks]

Peter,

Sorry to keep at this.  But I do not fully understand the signal path.  Is there a schematic you could share.
- With the "External Amp" selector, the ONLY input coming to the Orelo is a speaker level input from the external amp. 
- I assume therefore that there is a passive crossover, with crossover below 270 Hz to woofer, and above 7K for tweeter. 
- I do not understand how either DSP or the bass amps could be used with just a speaker level input coming to the Orelo.

Maybe I am missing something.

R.

[PeterSt]

Hi Ramesh,

I do think you understand, but possibly my first post about this was not made fully clear (about the "External Amp" input).

With External Amp :

- You'd feed Speaker Level signal from that amp to the Mid/High section;
- The Filter setup now will be different, but there surely still is a filter on the Mid and on the High plus an XOver obviously;
- The bottom part of the Mid is also filtered, to form the XOver towards the Bass units;
- The bass amps plus DSP remain active as they do with the (single) line level input.

Don't ask me how the level of the bass amps is attenuated, but or it has to be inherently (this is definitely possible), or the attenuation has to be done with the DSP (input level).

But you tell me ... contrary to me you used the External Amp, right ?
So if this is correct, what are your findings regarding this subject ?

Peter

PS:
Maybe I feel stupid not to be able to present a schematic, but this is because there are a million schematics in emails floating around, and the emails with Bert are 1000s on the Orelo alone (yes, this was all arranged for via email - believe it or not).

[briefremarks]

Peter,

What is confusing me is this.  With the External Amp input configuration I use, there is NO line level input coming to the Orelo.  Only the speaker level inputs from the external amp.

So my confusion is: what input is the DSP or bass amp getting.  It only has the speaker level input.

Ramesh

[PeterSt]

So my confusion is: what input is the DSP or bass amp getting.  It only has the speaker level input.

I suppose this "explanation" was not clear :

Don't ask me how the level of the bass amps is attenuated, but or it has to be inherently (this is definitely possible), or the attenuation has to be done with the DSP (input level).

Notice that "Speaker Level" is nothing else than a higher voltage level than Line Level. The Speaker Level is amplified Line Level and it can just be attenuated (brought back to Line Level). This happens internally (my mentioned "inherently") or it has to be done with the DSP Input Level (and attenuate that). If you don't recognize that you have been doing the latter, it will be the former.

Peter

[briefremarks]

Peter,

All clear now, sorry for being so slow on this.  I have been using the External Amp setting extensively for 5.1 with the Orelo as front L and R.  Really stunning sound.  I've been experimenting a bit with horns for the surround.  A friend of mine coincidentally also happened to have two of Bert's BD-15 bass bins built originally for the Oris horn I think.

Ramesh