NAD C658 Streaming DAC Review

[NADKEF listener]

C658 + C298 is a great combo. I doubt you will hear the difference with the other suggested combinations. Choice of speakers has a bigger impact! I traded my C658 + M23 for a M33. Because the latter is soon to be replaced you can get these with 35% discount, new in the box.

 

[Alexx]

@NADKEF listener
Thank you.

 

[Greg63]

There's nothing wrong with the C658.

If I hadn’t read this thread, I would never have known there were any issues with this preamp. Sonically, I’m completely satisfied with its performance. Paired with my M23, it actually outperforms my Hegel H190 in my system—so the Hegel now sits unused in the rack.

 

[steadilyfred]

Finally! It only took 6 years, 8 months, and 28 days to get Dirac Live Bass Control for the NAD C 658 and previous generations of the M33 and M10. It was originally announced by Dirac in August 21, 2019.

https://nadelectronics.com/blogs/news/nad-electronics-brings-dirac-live-bass-control-to-select-bluos-streaming-amplifiers

 

[KarVi71]

This is great news.

Testing it now on my system

Took them long enough...

 

[sharock]

I never thought I'd see the day.

My C658 has been gathering dust in a box since I got an M66, however, I hope to use it again in another room some day with other speakers and subs.

 

[bluefuzz]

It only took 6 years, 8 months, and 28 days to get Dirac Live Bass Control for the NAD C 658

At an utterly obscene price though. $299 over and above the price of the standard Dirac license (and the price of the device itself of course)! Even though I'm a big fan of Dirac I seriously doubt DLBC will make any meaningful difference to my setup which already sounds fine to my ear. Thanks but no thanks ...

 

[KarVi71]

At an utterly obscene price though. $299 over and above the price of the standard Dirac license (and the price of the device itself of course)! Even though I'm a big fan of Dirac I seriously doubt DLBC will make any meaningful difference to my setup which already sounds fine to my ear. Thanks but no thanks ...

While I agree the price is high, I went ahead and bought the license.

And even though I believed my bass was pretty good before, there is a big difference.

It is more defined with more kick now. I even had to turn down my bass boost a few dB's.

On my system its a big improvement.

 

[caesar]

While I agree the price is high, I went ahead and bought the license.

And even though I believed my bass was pretty good before, there is a big difference.

It is more defined with more kick now. I even had to turn down my bass boost a few dB's.

On my system its a big improvement.

I would be interested in a review by you. May I ask a few questions?

• Do you have one or two subwoofers?
• Are the two subwoofers get individual signal due to individual Dirac improvement now?
• How was the process of upgrading and doing DLBC measurement?
• Is it working flawless or did you recognize any quirks?
• There were reports about low subwoofer output (volume) with the c 658 in the past. How is it with your setup?

Thank you very much.

 

[KarVi71]

I only have one sub (for now). So I can't answer if they are fed individual signals. But I hope so, as I'm planing an extra sub.
I really expect them to be individual.

The process was easy.

I upgraded the firmware on the C658. While that was running, I bought a DLBC license and added it to my Dirac account.
These steps were a bit hard, as it was long time since I last logged in to my account on their website, so had to find my password.

When I restarted Dirac Live after upgrading the NAD, and loaded my previous project, the Bass management and Bass Control menus had become available.

I enabled Bass control, and asked Dirac to calculate the target, then uploaded to a slot on the NAD, and then it worked.
I didn't redo my measurements (planing to, but I'm awaiting new furniture, so will do it when that is in place).

In the BluOS app's the slider for adjusting crossover freguency goes away when you use a DLBC calculated slot.

It was all very easy, I found.

 

[KarVi71]

A little followup.

I have found that the bass has improved quite lot, there are notes i simply didn't hear before.

I have also found that I have had to reduce the bass boost a few dB's. The bass was simply too much.

But that is a balance thing, overall bass is _much_ better.
I think many will be surprised how much the bass can improve.

That said I haven't optimized bass much before. I left it to Dirac live to adjust phase and so on.
I have done some room treatment, with carpet and acoustic back panels.
But mostly to help with the higher frequencies and the rooms effect on the sound.

So depending on how much tuning has been done before results will vary.

 

[jhaider]

At an utterly obscene price though. $299 over and above the price of the standard Dirac license (and the price of the device itself of course)!

Depends on how one values time. $300 for a competent multisub calibration strikes me as a very fair deal, considering the time commitment to get it right manually.

 

[bluefuzz]

$300 for a competent multisub calibration strikes me as a very fair deal

But it's not just $300. It's $300 plus the price of the 'full' Dirac license plus the price of the device itself. The C658 is already ~8 years old and mine is over six. How much longer will it last or be supported? I'm not sure I'd want to sink another $300 in a device that may give up the magic smoke at any moment. And AFAIK Dirac licenses are non-transferable. If I were buying new I'd have to consider that full cost compared with one of the many free or open-source solutions. Yes that may take a couple of hours more fiddling but I value my money more than that small amount of time.

 

[steadilyfred]

But it's not just $300. It's $300 plus the price of the 'full' Dirac license plus the price of the device itself.

Dirac Live Bass Control can optimize low-frequency performance in ways that standard room correction typically cannot. In my view, that's tremendous value compared to other potential $300 upgrades I could consider for my system.

Also note that DLBC only requires the LE Room Correction license – the version included with your C 658. The Full Bandwidth version is optional.

 

[DaleMurray]

I would be interested in a review by you. May I ask a few questions?

• Do you have one or two subwoofers?
• Are the two subwoofers get individual signal due to individual Dirac improvement now?
• How was the process of upgrading and doing DLBC measurement?
• Is it working flawless or did you recognize any quirks?
• There were reports about low subwoofer output (volume) with the c 658 in the past. How is it with your setup?

Thank you very much.

I do not have Bass Control yet, however, I can state the following; when using two subwoofer with the C658 and Dirac Live, each sub does receive its own unique signal and correction. With traditional Dirac Live you will set a crossover point between subs and main speakers.

Example, if you have full range speakers that deliver down to 30hz but discover a modal issue causing a null at 70hz (this is my exact issue), you can correct this by placing a sub(s) in a location that will nullify the null (this is exactly what I did). I then set my crossover to 80hz and thus have a vary smooth response. However, I just cut my full range speakers off at the knees; no more bass for you.

I have verified this by cutting power to my subs and my floor standers are not putting out the bass. Great, I have towers that could be replaced with bookshelf speakers in regard to frequency response and output.

 

[caesar]

C 658 DLBC Review
First of all, I have no experience in NAD C 658 subwoofer operation without DLBC. I purchased two subwoofers just after DLBC was released for C 658 and I used them only with DLBC.

I am very satisfied of how DLBC is utilizing the subwoofers and how simple the setup is, in contrast of integrating subwoofers manually to a system.
I am also very pleasant about the outcome, the sound. Its huge, in comparison to my system without subs and with only Dirac Live. I know this is mostly due to the subs, but how well DLBC utilizes and integrates them is great. I got rid of a very nasty mode at 39hz, which was only attenuated with Dirac Live, but not fully eliminated. Now with two subwoofers, placed on diagonal edges in the room, the mode is cancelled out completely and at 0db.

Overall my system feels like a new and better system. Wider soundstage. More punch. Less bass boom. More palpability.

But now to the interesting part for you: I identified two of the long known problems with the device are addressed now.

Low subwoofer output
My Subs are at their minimum gain -12db and its still loud enough to align with my loudspeakers. Maybe its related to my subs. I can not speak for other subs, but for me there is no problem at all.

Inter sample clipping distortion
There are tracks which lead to clipping distortion as soon as subs are connected and the digital crossover of the C 658 is utilized. This is due to less headroom in the crossover implementation. One solution to prevent this was to attenuate headroom via e.g. roon. I was actually able to reproduce the issue with my subs and without DLBC. Couldn't reproduce it before, because lack of subs.
The good news is, the problem is gone when DLBC is active. This is due to the fact that Dirac is lowering the volume to gain headroom in order to do its work without clipping.

I wouldn't have thought that NAD is delivering DLBC to the C 658 and addressing those old bugs. I am actually very pleasant with my C 658 now. For me its a great device.

 

[steadilyfred]

I wouldn't have thought that NAD is delivering DLBC to the C 658 and addressing those old bugs. I am actually very pleasant with my C 658 now. For me its a great device.

Excellent update! Thanks for sharing.

 

[DaleMurray]

I'll purchase my DLBC license this week and spend the weekend setting things up.
I have two subs and intend to try a couple different locations for at least one of them.

 

[DaleMurray]

Quick update - DLBC is flipping amazing.

I relocated one of my subs (DIY 12" in 1cuft sealed cabinet powered by Crown) to the second best spot in my living room and calibrated with DLBC - I do not have the vocabulary to truly express how pleased and shocked I am. BTW, I play A LOT of scrabble.

Similar to what was stated above, my system went from L+R speakers with well integrated subwoofers to a seemingly, singular cohesive unit.

I've always strived to have a balanced system, not a "bass heavy" one, however one that does not shy away from bass when it's present. Like horsepower, you don't always need it but nice to have when you do.

One of my goto genres for testing bass reproduction are pipe organ recordings; if things are setup correctly it should feel natural, balanced, and effortless. As of late, Grain Moon by Anna Lapwood has become a favorite and the first track I played. Its particularly impressive at roughly 2:45 into the song.

I included photos of the subs because A, I am proud of them and B, to show they are not absurd.
Not terrible for a first try.

 

[RosalieTheDog]

I see some open box C658 for €1100, so €1400 with the Bass Control update. Am I right that this is the cheapest way to add DLBC to an existing 2.1 system?