high level subwoofer connection vs. rca

[A Surfer]

hmm, you are most fortunate to have the luxury of a NAD M3! truly convenient platform with nicely implemented bass management. i am on the look out for something similar in the used market locally.

Thanks, and I totally agree. The M3 seems to have been both a design and execution gem. I adore it, but I do believe it is slightly mellow in character. That only matters if you pair it with speakers with the same characteristic which in certain situations could amount to being too much of a good thing. If you can find it used really do so, it is a pretty fabulous item.

I think in about 2014 I found it used, complete with absolutely everything as new retail, low hours and well cared for, all for less than half of the new retail so an absolute steal. I think this is an example of when NAD really nailed the design goals as articulated by a genuinely competent and talented designer.

 

[richard12511]

Most likely because you only have to go back 10 years on audio forums to find most audiophiles acting like using a subwoofer in a stereo setup was as desirable as giving yourself an STD. lol

I'm about 10 years into this hobby and this is exactly the environment I joined 10 years ago. If you were building a 2 channel music system you didn't need a sub. If you were building a multi-purpose HT/Music system you needed a sub, but you were supposed to turn it off for music listening

I'm so glad the majority seem to have come to their senses about this, though there's still a size-able chunk of holdouts(go read the 2-channel forum on AVS ). Can't wait for all of these dumb voodoo practices to fade. I'll probably die first, though.

 

[raistlin65]

I'm about 10 years into this hobby and this is exactly the environment I joined 10 years ago. If you were building a 2 channel music system you didn't need a sub. If you were building a multi-purpose HT/Music system you needed a sub, but you were supposed to turn it off for music listening

I'm so glad the majority seem to have come to their senses about this, though there's still a size-able chunk of holdouts(go read the 2-channel forum on AVS ). Can't wait for all of these dumb voodoo practices to fade. I'll probably die first, though.

Yep. I remember 10-12 years ago on AVS in the 2 channel forum. Subs were not what real audiophiles used. And hip hop and rap? EDM? That's not music. lol

I think (hope) we now have enough people going, "Yes, you need a sub," that people new to the hobby rarely get taught that any more.

 

[hawk01]

i can never downplay the importance of having a subwoofer (especially duals) in a two channel set up. hence my nitty search for something acceptable in the market of integrateds. case in point: i have revel m16s in a 1931cuft room. these things are capable of delivering decent quantities of bass for their size. you could say they could stand their ground by themselves well enough for the most part. however, i have material when played on them excites the room like hell and in the absence of EQ resources you are must better off avoiding those that altogether. this is where my dual subs hooked into the trusty avr shines! they breeze through anything thrown at them with a high level of acceptable bass performance compared to the revel m16s alone which can be picky in exciting room modes.. my duals are placed in opposing diagonal corners of the room, one on floor level, the other one on a 2ft high stand. the assymetrical positions do serve a very good purpose! funny for the time being my decent integrated amp is no match against the humble avr if only for this merit.

 

[witwald]

So back to the M3. It offers two preouts, one preout provides analog 2nd order filters configured around the low impedance differential Class A output stage of the preamp at the typical 40, 60, 80, 100 or full range. This preout is used for my mains which are pretty bass competent Monitor Audio PL200. I highpass at 40Hz and use the other preout to send the full range signal to my dual SB2000 Pro subs allowing the subs to do the crossover there.

This seems to do a good job to my ears and from a technical standpoint it should be fundamentally sound enough not to be introducing any spurious, audible nastiness into the sound. Is this not an example of at least an adequate way that an integrated amp can provide the most basic of bass management into a 2.2 system?

Yes, I think that the NAD M3 integrated amplifier has done a quite good job of bass management. The use of the 2nd-order high-pass filters is predicated on them piggy-backing onto the natural rolled-off response of the main loudspeakers. For smaller bookshelf loudspeakers, the use of the 60 Hz or 80 Hz cut-offs will produce an approximate 4th-order acoustic high-pass response. These can then generally be well blended with the 4th-order low-pass filtered acoustic response of the subwoofer(s). The NAD M3 is a nice unit as it provides .2 two-channel outputs that support independent left and right subwoofers. That's a big plus and a major step up from simpler approaches.

As long as the subwoofer has a continuously variable low-pass filter and a continuously variable phase response adjustment, then it is highly likely that it will be possible to relatively smoothly integrate the output of the subwoofers with the output from the mains. Although the high-passed and low-passed acoustic responses may not be strictly complementary, in the Linkwiitz-Riley 4th-order filter sense, the end result will still be quite good. There should be minimal overlap in the high-pass and low-pass acoustic responses, which will tend to minimise any undesirable interactions. Although time delay correction options might be missing, if the left and right subwoofers are placed near to the left and right main speakers, then the time-of-flight differences can be minimised by simple geometric placement of the subwoofers on the radial arc passing through the main speakers, with the radius measured from the listening position.

 

[witwald]

I can never downplay the importance of having a subwoofer (especially duals) in a two channel set up. hence my nitty search for something acceptable in the market of integrateds. Case in point: I have Revel M16s in a 1931 cuft [55.7 m^3] room. these things are capable of delivering decent quantities of bass for their size.

The Revel M16 have a Low Frequency Extension that is specified as being -3 dB at 55Hz , -6 dB at 50Hz , and -10 dB at 45Hz . From this data, it would seem that setting the high-pass filter on a NAD M3 to 60 Hz, would serve to provide a close approximation of a 4th-order Linkwitz-Riley high-pass acoustic response with a -6 dB cut-off frequency of about 57 Hz or so. Setting the low-pass cut-off frequency on the subwoofer around that value should achieve a good blending with minimal overlap, and with the main speakers having much less work to do. Subwoofer localisation wouldn't be an issue either, as the subwoofer is taking over sound reproduction duties well below 80 Hz.

 

[witwald]

...the thought of running several lengths of interconnects would make the room look like a nest of vipers! as if its not getting there already. Wife might use them interconnects to strangle me in my sleep!

You need not worry, as true audiophiles such as yourself never fall asleep while seated in the listening position!

 

[Kal Rubinson]

I'm about 10 years into this hobby and this is exactly the environment I joined 10 years ago. If you were building a 2 channel music system you didn't need a sub. If you were building a multi-purpose HT/Music system you needed a sub, but you were supposed to turn it off for music listening

One can make the same statement but substitute DSP for sub.

 

[A Surfer]

Yes, I think that the NAD M3 integrated amplifier has done a quite good job of bass management. The use of the 2nd-order high-pass filters is predicated on them piggy-backing onto the natural rolled-off response of the main loudspeakers. For smaller bookshelf loudspeakers, the use of the 60 Hz or 80 Hz cut-offs will produce an approximate 4th-order acoustic high-pass response. These can then generally be well blended with the 4th-order low-pass filtered acoustic response of the subwoofer(s). The NAD M3 is a nice unit as it provides .2 two-channel outputs that support independent left and right subwoofers. That's a big plus and a major step up from simpler approaches.

As long as the subwoofer has a continuously variable low-pass filter and a continuously variable phase response adjustment, then it is highly likely that it will be possible to relatively smoothly integrate the output of the subwoofers with the output from the mains. Although the high-passed and low-passed acoustic responses may not be strictly complementary, in the Linkwiitz-Riley 4th-order filter sense, the end result will still be quite good. There should be minimal overlap in the high-pass and low-pass acoustic responses, which will tend to minimise any undesirable interactions. Although time delay correction options might be missing, if the left and right subwoofers are placed near to the left and right main speakers, then the time-of-flight differences can be minimised by simple geometric placement of the subwoofers on the radial arc passing through the main speakers, with the radius measured from the listening position.

Thank you for the input, it makes me feel better about my placement choice. I actually sent this picture to SVS technical support and they as you have just done here suggested that such an alignment would be beneficial for getting away from time related integration issues. Here is how I currently have the subs and mains because of the room I had no other options.

 

[Chrispy]

@Kvalsvoll, @Chrispy ah my dear sirs i am once again back to the ole reliable humble AVR as you @Chrispy have highly regarded! dang this is becoming a ”told you so” moment already. at any rate, even if the SVS recommendation for line level connections are legit, the thought of running several lengths of interconnects would make the room look like a nest of vipers! as if its not getting there already. wife might use them interconnects to strangle me in my sleep!

There are ways to hide wire....or even wireless solutions. If you really want an integrated amp without bass management you could add a miniDSP 2x4 for example to provide such, if the integrated has pre-out/main-in or processing/tape loops.

 

[hawk01]

There are ways to hide wire....or even wireless solutions. If you really want an integrated amp without bass management you could add a miniDSP 2x4 for example to provide such, if the integrated has pre-out/main-in or processing/tape loops.

yes i realize the overall benefits of employing minidsp and how it can be inserted into my integrated amp with pre-out/main-in. it is slowly in the works as i need to upgrade my ancient laptop which has not seen action since the advent of the mighty tablet!

 

[hawk01]

@A Surfer might be worth checking link below reference into multiple subwoofer integration. although i am just using an avr so far so good with bass integration following the guidelines as the doctor ordered!

http://www.soundoctor.com/whitepapers/subs.htm

 

[A Surfer]

@A Surfer might be worth checking link below reference into multiple subwoofer integration. although i am just using an avr so far so good with bass integration following the guidelines as the doctor ordered!

http://www.soundoctor.com/whitepapers/subs.htm

Thank you, and I had read that before (I'm pretty sure) and one day I will be doing REW and DSP correction, the sub crawl etc. The results will be worth the effort, but it is a commitment for sure. Thank you for the link, this seems to be updated from when I read it about 4 years ago (pretty sure it was the same person). Cheers.

 

[escksu]

Hi level will have more noise and distortion. Its going through an additional and unnecessary amplification stage. REL are absolutely wrong on this one.

If you are using an AVR it will also filter the low frequencies (typically @80Hz) and send them to the sub. Your mains will have less distortion not having to play those lowest frequencies.

Hmm.....since this is ASR, my question will be any proof?? Is it audible in a blind listening test?

 

[March Audio]

Hmm.....since this is ASR, my question will be any proof?? Is it audible in a blind listening test?

Sure. Take a look through the power amplifier tests her on ASR and you will see generally they have much higher noise and distortion than any line level source.

Audibility is another question indeed. Maybe not, but why not use the better quality source if its practical to do so?

My recollection is that REL think you match the sound of the amp better or something like that, but its pretty specious.

My main gripe with this is that you lack bass management and proper sub integration unless you filter the main speakers

 

[A800]

Never use high level to connect a sub.

 

[Count Arthur]

Regardles of its technical merits, or demerits, I had good results with a REL subwoofer with high level input. Initially I set it up by ear, I adjusted the upper frequency cut-off on the sub to somewhere around the low frequenct roll-off of my bookshelf/monitor speakers, around 45Hz. Then adjusted the volume of the sub to the point where it's a bit too obvious, then backed it off a bit.

Later I tested it with a REW and a UMIK-1 microphone and I wasn't far off, you could see that the sub was doing what it's supposed to and filling in the low end where the speakers rolled off.

 

[A Surfer]

I also used the REL high level thing with a pair of little T-Zeros' and I found it to sound quite nice. Now could there have been better results even had I not done so? Possibly. I am not trying to suggest that high level is the way to go, I lack any technical acumen for such a claim, but I do want to publicly state that my experience using the high-level option was at least a positive one.

 

[March Audio]

I also used the REL high level thing with a pair of little T-Zeros' and I found it to sound quite nice. Now could there have been better results even had I not done so? Possibly. I am not trying to suggest that high level is the way to go, I lack any technical acumen for such a claim, but I do want to publicly state that my experience using the high-level option was at least a positive one.

Oh it certainly can work OK there is no issue there, and you can get it working quite well, but if looking for better ways to do it then some kind of bass management is probably needed.

 

[raistlin65]

Oh it certainly can work OK there is no issue there, and you can get it working quite well, but if looking for better ways to do it then some kind of bass management is probably needed.

Agreed.

Some (maybe many) setups would benefit from a higher crossover point than wherever the natural roll off of the speakers allows the sub to be integrated to achieve the listeners preferred sound.

Whether due to room acoustics. Or distortion from the speaker below the tuning point at higher volumes. The latter could particularly be a problem with base heavy music or movie bass special effects. My Sierra 2EX have an anechoic response of 38Hz - 38kHz ± 3dB, and I still cross it over at 80hz because my subs are more capable in my big space.