What’s Wrong with the NAD M66 Streamer / Preamp? Perhaps M33 V2 is Better

[Hear Here]

I was excited when I first heard about this streamer preamp from NAD’s Master Series. As a Master Series user for the last few years (M12 preamp, M32 all-in-one and currently the excellent M33 all-in-one), there seemed to be an opportunity to upgrade my electronics at reasonably modest cost, as I already have a pair of Atma-Sphere Class D mono power amps waiting in the wings.

The spec looked attractive, even for a digital-only user such as myself. One big new feature is its 4 subwoofer outputs, available from both XLR and single-ended sockets. Also included are Dirac Live DSP and Dirac Live Bass Control – the latter a feature I know very little about, apart from its claimed ability to maintain timing accuracy when subs are present.

All good stuff – at least on paper, particularly as I recently bought a pair of REL S812 subs with their twin 12” drivers. My Avantgarde Duo XD speakers also feature twin 12” bass drivers so they really don’t need more bass drivers to deliver furniture-rattling and neighbour-disturbing bass, but the subs are perhaps best thought of as fillers-in of room modes that may require attention via subs.

However, when looking more closely at how the M66 works, a few very disturbing facts emerge. Look at the back panel and you’ll see that the Sub Outs are labelled simply 1, 2 ,3 and 4. THEY ARE ALL MONO - not stereo - even if you tell the M66 that there is more than a single sub present! Why not keep 2 or 4 subs as stereo?

OK, here’s the even more disturbing discovery – Tell the M66 that there are subs present (any number of them) and you have to specify a crossover. That would be good in many systems where subs are added to provide bass for a stand-mount speaker system that may be suffering overload distortion from their small bass drivers. However, a disaster for anyone with full-range main speakers such as my Duos. Why should I spend a ton of dosh on genuinely full-range speakers, only for the M66 to cripple them by applying the same XO as the subs? I don’t want to deprive my main speakers of bass, particularly the mono bass that the M66 insists on sending to the subs!

This came as a bit of a shock as my earlier NAD M12 preamp (and for that matter the M32) allowed the Main Outputs optionally to remain full-range, while the Sub Outs could have any XO between 40 and 200 Hz applied. Not so with the M66, or as I’ve recently discovered, my own M33. Why cannot the Main Outs remain full-range with these newer NAD units?

This bizarre and undisclosed dirty little secret feature of the M66 has ruled it out as an upgrade for me. Sadly so, as it offers many other benefits over my M33.

OK, here’s the better news – the recently announced M33 Version 2 seems to offer an interesting solution for owners of full-range main speakers. It offers Preamp Outputs in both XLR and single-ended, as well as a pair of Sub Outs in single-ended only. These Preamp Outs are of course STEREO, whereas the Sub Outs are still MONO.

So perhaps owners of full-range speakers should be looking towards the M33 V2, rather than the M66 plus power amp. Connect the subs to the Preamp Outs (and use their own built-in XOs to specify the frequency cut-off) and tell Settings that there are No Subs present. Now we’ve possibly cracked it – full-range into the Main speakers and Stereo into the Subs. Leave the mono Sub Outs for those with limited-range main speakers!

The M33 V2 features the identical ES9039PRO DAC as the M66 (an improvement over the older M33) and I guess the BluOS streamer and preamp modules are also near-identical to those in the M66. The V2 also features DL and DLBC so my current opinion is that the M33 V2 is likely the better bet for owners of grown-up main speakers!

But this raises a question – will Dirac Live or DLBC still be available if set up in the way I’ve described? Frankly, I’m not a “room correction DSP” fan, as my experience with DL (and RoomPerfect and MARS for that matter), is that the top end loses a little of its sparkle if it has to endure the signal processing that DSPs present to the entire frequency range, even if they can only adjust the bass spectrum.

So, can anyone with DL and DLBC experience offer any insight that may answer this question?

Also, any comments (specially from M66 owners) on my observations concerning the M66 or the M33 V2 appreciated. Thanks

 

[vddobrev]

@Hear Here I hear you loud and clear in all frequencies!

 

[Kirk wallace]

I was excited when I first heard about this streamer preamp from NAD’s Master Series. As a Master Series user for the last few years (M12 preamp, M32 all-in-one and currently the excellent M33 all-in-one), there seemed to be an opportunity to upgrade my electronics at reasonably modest cost, as I already have a pair of Atma-Sphere Class D mono power amps waiting in the wings.

The spec looked attractive, even for a digital-only user such as myself. One big new feature is its 4 subwoofer outputs, available from both XLR and single-ended sockets. Also included are Dirac Live DSP and Dirac Live Bass Control – the latter a feature I know very little about, apart from its claimed ability to maintain timing accuracy when subs are present.

All good stuff – at least on paper, particularly as I recently bought a pair of REL S812 subs with their twin 12” drivers. My Avantgarde Duo XD speakers also feature twin 12” bass drivers so they really don’t need more bass drivers to deliver furniture-rattling and neighbour-disturbing bass, but the subs are perhaps best thought of as fillers-in of room modes that may require attention via subs.

However, when looking more closely at how the M66 works, a few very disturbing facts emerge. Look at the back panel and you’ll see that the Sub Outs are labelled simply 1, 2 ,3 and 4. THEY ARE ALL MONO - not stereo - even if you tell the M66 that there is more than a single sub present! Why not keep 2 or 4 subs as stereo?

OK, here’s the even more disturbing discovery – Tell the M66 that there are subs present (any number of them) and you have to specify a crossover. That would be good in many systems where subs are added to provide bass for a stand-mount speaker system that may be suffering overload distortion from their small bass drivers. However, a disaster for anyone with full-range main speakers such as my Duos. Why should I spend a ton of dosh on genuinely full-range speakers, only for the M66 to cripple them by applying the same XO as the subs? I don’t want to deprive my main speakers of bass, particularly the mono bass that the M66 insists on sending to the subs!

This came as a bit of a shock as my earlier NAD M12 preamp (and for that matter the M32) allowed the Main Outputs optionally to remain full-range, while the Sub Outs could have any XO between 40 and 200 Hz applied. Not so with the M66, or as I’ve recently discovered, my own M33. Why cannot the Main Outs remain full-range with these newer NAD units?

This bizarre and undisclosed dirty little secret feature of the M66 has ruled it out as an upgrade for me. Sadly so, as it offers many other benefits over my M33.

OK, here’s the better news – the recently announced M33 Version 2 seems to offer an interesting solution for owners of full-range main speakers. It offers Preamp Outputs in both XLR and single-ended, as well as a pair of Sub Outs in single-ended only. These Preamp Outs are of course STEREO, whereas the Sub Outs are still MONO.

So perhaps owners of full-range speakers should be looking towards the M33 V2, rather than the M66 plus power amp. Connect the subs to the Preamp Outs (and use their own built-in XOs to specify the frequency cut-off) and tell Settings that there are No Subs present. Now we’ve possibly cracked it – full-range into the Main speakers and Stereo into the Subs. Leave the mono Sub Outs for those with limited-range main speakers!

The M33 V2 features the identical ES9039PRO DAC as the M66 (an improvement over the older M33) and I guess the BluOS streamer and preamp modules are also near-identical to those in the M66. The V2 also features DL and DLBC so my current opinion is that the M33 V2 is likely the better bet for owners of grown-up main speakers!

But this raises a question – will Dirac Live or DLBC still be available if set up in the way I’ve described? Frankly, I’m not a “room correction DSP” fan, as my experience with DL (and RoomPerfect and MARS for that matter), is that the top end loses a little of its sparkle if it has to endure the signal processing that DSPs present to the entire frequency range, even if they can only adjust the bass spectrum.

So, can anyone with DL and DLBC experience offer any insight that may answer this question?

Also, any comments (specially from M66 owners) on my observations concerning the M66 or the M33 V2 appreciated. Thanks

Would using the method REL recommends, connecting the Speakon connector from the REL to the amplifier's speaker outputs, avoid this problem? That way, one could set the crossover with the pot on the REL itself and the NAD doesn’t get involved at all. (This is the way I have my M33 set up with my T/x9 (much smaller than your set up.)

 

[DVDdoug]

Bass is usually "mono" (identical in both channels). It's basically non-directional because of the long wavelengths and most people (unlike you) need both woofers working together for the best & most bass. (In vinyl days mono bass helped with tracking.)

Why cannot the Main Outs remain full-range with these newer NAD units?

That's how a crossover normally works. But a lot of powered subs have their own low-pass filter that can be used separately.

Or you can configure an AVR without using the crossover so only the LFE channel goes to the sub and the regular bass goes to the main speakers.

 

[pablolie]

However, when looking more closely at how the M66 works, a few very disturbing facts emerge. Look at the back panel and you’ll see that the Sub Outs are labelled simply 1, 2 ,3 and 4. THEY ARE ALL MONO - not stereo - even if you tell the M66 that there is more than a single sub present! Why not keep 2 or 4 subs as stereo?

Subs are supposed to be mono by definition. Unless you use them at higher frequencies than 80Hz. And they add zero to imaging if kept at under 80hz unless you have weird interactions with room modes.

If you want two of the outputs to work as "stereo" you can set them to such a frequency, but since you claim you have full range speakers, I'd have no idea why you would want to.

OK, here’s the even more disturbing discovery – Tell the M66 that there are subs present (any number of them) and you have to specify a crossover. That would be good in many systems where subs are added to provide bass for a stand-mount speaker system that may be suffering overload distortion from their small bass drivers. However, a disaster for anyone with full-range main speakers

That is absolutely not true. Setting a crossover frequency that is optimal is the whole point of fine tuning sub performance. The type of main speaker doesn't matter one iota. If you think your main speakers perform perfectly in your room going all the way down to 28Hz or so, then set the sub xover frequency to that.

such as my Duos. Why should I spend a ton of dosh on genuinely full-range speakers, only for the M66 to cripple them by applying the same XO as the subs?

It would never do that unless you misconfigured it yourself. This is not a cheap integrated amp that limits itself to one or two subs and has a set frequency at 80Hz. You *pay* for its very extensive feature set, which allows you to configure everything (including optimal crossover frequencies) optimally.

I don’t want to deprive my main speakers of bass,

Big stand mounts may go low, but sometimes that doesn't fit your room profile and all in all things can sound significantly better if you leverage the "mono" subs in optimal positions at optimal crossover frequencies. The M66 will *not* deprive your main speaker of full range unless you (or Dirac) make that choice. That's a blatant misunderstanding on your part, sorry.

particularly the mono bass that the M66 insists on sending to the subs!

Which is also your choice entirely, the M66 doesn't do that unless you configure it to do so.

I think you're just a bit confused about the huge feature set and how to best leverage it.

 

[Hear Here]

Would using the method REL recommends, connecting the Speakon connector from the REL to the amplifier's speaker outputs, avoid this problem? That way, one could set the crossover with the pot on the REL itself and the NAD doesn’t get involved at all. (This is the way I have my M33 set up with my T/x9 (much smaller than your set up.)

Thanks Erik

That is certainly one option and in fact I first wired up the subs that way - using speaker-level rather than preamp level. This allows the main speakers to receive the full frequecy range. However, the benefits of Dirac Live (and DLBC in the M66) are largely lost by going that route. Time alignment in particular cannot be applied to the sub. Nevertyheless, I may give that option a try now my M66 has arrived - yesterday!

Incidentally, NAD always used to allow one to set a different XO for Main and Sub output, or indeed no XO at all. I had the M32 and the M12 and both offered a much more comprehensive Sub settings choice. With either unit, I could set the Subs to receive say 80 Hz and below, while the Mains continued to receive the full frequency range. Why has NAD deprived us of this choice with the M33 and M66?

 

[Hear Here]

Bass is usually "mono" (identical in both channels). It's basically non-directional because of the long wavelengths and most people (unlike you) need both woofers working together for the best & most bass. (In vinyl days mono bass helped with tracking.)


That's how a crossover normally works. But a lot of powered subs have their own low-pass filter that can be used separately.

Or you can configure an AVR without using the crossover so only the LFE channel goes to the sub and the regular bass goes to the main speakers.

But at what frequency does a sound become "directional"? My main speakers' bass section needs 170 Hz and below. Could I accept this as mono?

I'm unfaminiar with AVRs so need a bit of education! How could an AVR (whatever that is) help in my system? Thanks

 

[Hear Here]

That is absolutely not true. Setting a crossover frequency that is optimal is the whole point of fine tuning sub performance. The type of main speaker doesn't matter one iota. If you think your main speakers perform perfectly in your room going all the way down to 28Hz or so, then set the sub xover frequency to that.

What you say may be the case with other brands and earlier NADs suvh as M12 and M32, but the M33 and M66 REQUIRE ax XO to be specified when you say there are subs present. b That XO is applied to the Main Out - whether you like it or not! The Sub Outs are mute until you tell the M33 or M66 that there are subs present, so there is no easy dodge! Check it iut and report back if you are an M33 or M66 user!

It would never do that unless you misconfigured it yourself. This is not a cheap integrated amp that limits itself to one or two subs and has a set frequency at 80Hz. You *pay* for its very extensive feature set, which allows you to configure everything (including optimal crossover frequencies) optimally.

As above -s Setting an XO in Subs settings means that the Main Outrs are deprived of low frequencies - no alternative!

Which is also your choice entirely, the M66 doesn't do that unless you configure it to do so.

Sorry, you are wrong again - the Sub Outs are MONO and cannot be changed to deliver stero. Look at the lavels on the back panel. They are simply numbered 1, 2, 3, 4 - not Left and Right

I've explained on another forum my options and I'll post these here, but getting the M66 or M33 to deliver the full range to Mains once they know there are subs present is IMPOSSIBLE - as confirmed by NAD's team last week. I do have options, but none are as satisfactory as selecting the IMPOSSIBLE - Mains still receive the full range while subs have a chosen XO applied.

 

[voodooless]

DLBC should give you way more freedom in crossover settings of mains and subs.

No subwoofer outputs are ever stereo. They are always mono, for the obvious reasons already mentioned by others.

 

[pablolie]

What you say may be the case with other brands and earlier NADs suvh as M12 and M32, but the M33 and M66 REQUIRE ax XO to be specified when you say there are subs present.

IMO that is the whole point of even basic management. I would never ever by an amp with a sub output that simplistically sets everything to an 80Hz crossover. I am not sure what you are expecting.

That said, I went to read the user guide of the M66 and their info on bass management is rather lean, which makes it hard to establish if you can keep the mains full range. The only thing they state is the Xover frequency can be set as low as 40Hz, which should make things pretty undetectable - not many speakers really deliver on a lot of power there anyhow. (And note that full range speakers' bass is typically quite compromised in those frequencies in normal rooms, which is why I no longer have interest in big honking tower speakers).

Sorry, you are wrong again - the Sub Outs are MONO and cannot be changed to deliver stero.

Subwoofers do not come left or right. The M66 allows you to configure optimal output for several subs, which is exactly how you should look at things.

It comes with a complete Dirac package for everything/ Trust it, it'll set up things optimally for your room.

Look at the lavels on the back panel. They are simply numbered 1, 2, 3, 4 - not Left and Right

Because -if you want to- you can set 1 as R and 2 as L. It's all up to you.

 

[Hear Here]

IMO that is the whole point of even basic management. I would never ever by an amp with a sub output that simplistically sets everything to an 80Hz crossover. I am not sure what you are expecting.

That said, I went to read the user guide of the M66 and their info on bass management is rather lean, which makes it hard to establish if you can keep the mains full range. The only thing they state is the Xover frequency can be set as low as 40Hz, which should make things pretty undetectable - not many speakers really deliver on a lot of power there anyhow. (And note that full range speakers' bass is typically quite compromised in those frequencies in normal rooms, which is why I no longer have interest in big honking tower speakers).




Subwoofers do not come left or right. The M66 allows you to configure optimal output for several subs, which is exactly how you should look at things.

It comes with a complete Dirac package for everything/ Trust it, it'll set up things optimally for your room.


Because -if you want to- you can set 1 as R and 2 as L. It's all up to you.

The NAD amps offer any XO between 40 and 200 Hz, so the user can specify the XO he thinks may suit his system. However the newer NADs (M33 and M66) offer no alternative XO for the Main Out and no option to "opt out" of an XO for the mains, so these speakers could continue to receive the full range. Odd but true!

Indeed subs don't come as left and right - but neither do main speakers! It's the different signals sent to the speakers that determine whether they reproduce the left or right channel. The M66 offers 4 mono sub outs so every sub will receive an identical mono signal. If I want my main speakers to receive the full frequency range (as I do) I must find the bass from 2 of the Sub Out and send these mono signals to the speakers' low-level input for their bass units. The AG speakers' bass units handle 170 Hz and below, so the XO in the M66 must be set at between 170 and 200 Hz. However this means that my main speakers will be delivering stereo above 170 but mono below 170. Is that likely to be detectable by the human ear?

You can't set subs to left or right as they all receive mono - left plus right

 

[voodooless]

The M66 offers 4 mono sub outs so every sub will receive an identical mono signal.

Not with DLBC. This thing doesn’t really make sense without DLBC if you have multiple subs.

 

[pablolie]

... The M66 offers 4 mono sub outs so every sub will receive an identical mono signal....

Nope they are completely. configurable individually. That is clear from the user guide.

... The AG speakers' bass units handle 170 Hz and below, so the XO in the M66 must be set at between 170 and 200 Hz. However this means that my main speakers will be delivering stereo above 170 but mono below 170. Is that likely to be detectable by the human ear?

I don't think that'll work. The subouts are for powered subs. Main speakers (unless they have a built in amp for the sub units) don't support that. You'd need maybe a separate power amp.

I really think you need to study this topic a bit more. You are clearly trashing a piece of equipment you don't quite understand how to set up in your environment.

I'd you switch to questions about how to integrate the M66 to do what you want we could help you, this way we can't.

 

[Hear Here]

Nope they are completely. configurable individually. That is clear from the user guide.



I don't think that'll work. The subouts are for powered subs. Main speakers (unless they have a built in amp for the sub units) don't support that. You'd need maybe a separate power amp.

I really think you need to study this topic a bit more. You are clearly trashing a piece of equipment you don't quite understand how to set up in your environment.

I'd you switch to questions about how to integrate the M66 to do what you want we could help you, this way we can't.

The Sub Outs can only be adjusted for XO - nothing else, though perhaps DL / DLBC (if a filter is generated and engaged) may adjust each sub to improve overal response from all bass speakers in the system. I have the User Guide, so please indicate where you think it says that Sub Outs are configurable. Thanks

My own speakers do have an internal active XO (adjustable + or - from 170 Hz) and a built-in bass amp with DSP. The speakers can accept a full-range signal from the main amp for the entire system, or it can use that signal for mid and top only and use a line-level for the bass. So what I said about my options is correct.

I'm certainly not trashing the NAD (I wouldn't have bought it if I thought it was trash), but to point out to others who use full-range speakers of its shortcomings. Most people will be very happy that their main speakers can be relieved of bass duties, but not if they've spent a 5-figure sum on speakers designed for and able to deliver the full range.

I'd be delighted to look at any suggestions for configuring my system, but they'll need to be familiar with the features of the M66 in order to offer sugestions that would work in practice. This is likely to be from fellow M66 or M33 owners as the features I raised in the OP apply annoyingly to both - but not their predecessors, the M12 and M32. I know these units pretty well as I own M66, M33 and M12 currently, and used to own the M32. I have only one wiring option that allow my mains to receive the full range when subs are present, and it's not entirely satisfactory - the ideal being full range from the Preamp outs, but this is not possible with subs connected to Sub Outs. Is there any other work-around that you think I've overlooked?

Perhaps this sketch will clarify the situation. It's the only way that I can find that would allow my speakers to receive the full range with subs present

 

[pablolie]

The Sub Outs can only be adjusted for XO - nothing else, though perhaps DL / DLBC (if a filter is generated and engaged) may adjust each sub to improve overal response from all bass speakers in the system. I have the User Guide, so please indicate where you think it says that Sub Outs are configurable. Thanks

There is an online video showing that. As I said, the user guide leaves a lot to be desired. But there is absolutely no way Dirac would be supported if Sub xovers can't be configured individually.

My own speakers do have an internal active XO (adjustable + or - from 170 Hz) and a built-in bass amp with DSP. The speakers can accept a full-range signal from the main amp for the entire system, or it can use that signal for mid and top only and use a line-level for the bass. So what I said about my options is correct.

There you go. That means you can optimally include the bass capabilities of your mains easily. It will establish how much the woofers in your speakers and whatever many subs should be leveraged for optimal room response. Dirac and room management are about the most important innovation in audio in over 30 years, in my opinion.

I'd be delighted to look at any suggestions for configuring my system, but they'll need to be familiar with the features of the M66 in order to offer sugestions

You are unkind. I went out and checked the user guide to try to help. It is not an insignificant investment you made, and the specs read stellar. If I was interested in setting up a larger system, it would be a top choice (by far) for me.

 

[Hear Here]

There is an online video showing that. As I said, the user guide leaves a lot to be desired. But there is absolutely no way Dirac would be supported if Sub xovers can't be configured individually.


There you go. That means you can optimally include the bass capabilities of your mains easily. It will establish how much the woofers in your speakers and whatever many subs should be leveraged for optimal room response. Dirac and room management are about the most important innovation in audio in over 30 years, in my opinion.


You are unkind. I went out and checked the user guide to try to help. It is not an insignificant investment you made, and the specs read stellar. If I was interested in setting up a larger system, it would be a top choice (by far) for me.

As I say, I've no doubt that Dirac / DLBC will calibrate each sub and adjust according to the reasings, but nothing can be done without Dirac, apart from the single XO setting within Settings > Audio. If there's a video that shows otherwise, my initial search hasn't found it, but I'll continue searching.

If I had conventional speakers without hybrid self-powered bass units, it would be impossible to retain full-range for these main speakers, although perhaps if they had separate binding posts for the bass drivers and these bass drivers handled nothing above 200 Hz, one could use Sub-Outs feeding the the speakers via extra power amps.

The M66 is indeed a great unit, particularly for analogue usders (I'm not in this group) but I think it inexcusable that the M66 and M33 does not allow main speakers to receive bass frequencies just because there are subs present, particularly as older units offered the flexibility of different or no XOs for main and sub outputs.

Could you open the sketch and is it clear in showing how I've rigged my system? Can you think of an alternative that would provide the main speakers with the full frequency range?

 

[borsht]

I think Here Here would like a High Pass filter to his mains that can be turned off while still setting separately the subs low pass filter to a particular frequency. Bel Canto E1X can do this for example.