The Darbari: new speaker project

[kapvin]

Re: MiniDSP next steps

A thought just occurred -- why would an upsampling done in my computer in software be better than upsampling done by the digital input of the MiniDSP?

No emperical reason. essentially a choice exists. I have read gripes about the SRC on minidsp and possibly something like Jriver might be a better. important thing, is that the choice exists. My experience on the DCX is that native resolution works much better (but that might be confirmation bias)


re: your point about volume control; the minidsp has a digital volume control. If you are anal about "losing bits" then you'd not use the volume control and use something downstream. I use the MSB 8 channel control (which is what SL also uses)- but I use it more from a gain structure mitigation perspective.

if you are okay to use the digital volume control, i'm guessing it's applied to the i2s signal as well. you could ask in the minidsp support forum

edit : by full potential I meant beyond the biquads that you can generate with ACD or REW.(you'll remember we talked about the ACD spreadsheet before.) i am in an uncharted zone here, but apparently there is a lot more you can do with the DSP. bit don;t ask me exactly what.

 

[trittya]

Re: Another known DSP owner's perspective

Hi there, Tarun Bhai and other FMs

Allow me to share the relevant extract of a post that I commenced on our (800+ strong) DIY (Facebook) Group that a handful of very dear friends and I started less than two years ago. IIRC, this was posted before I posted that2channelaudio link on this thread for your notice.
The parts in bold are there, courtesy - facebook user-interface.
"The DIY and Custom-Builders' Guild" lives here
https://www.facebook.com/groups/diy.custom.hifi/

Quote:
Trittya Tunn
Shivaprashanth S Hiremath and other owners of miniDSP,
Do share your tweaking and listening experience by commenting on this article.
2channelaudio: MiniDSP 2x4 (Analog to Analog) Crossover Implementation Experience
2channelaudio: MiniDSP 2x4 (Analog to Analog) Crossover Implementation Experience
2channelaudio.blogspot.com
Like Share Unfollow Post November 23 at 2:32am

Shivaprashanth S Hiremath i have never been happy with miniDSP in analog-to-analog mode. digital input and a good DAC at the other end makes this product truely hifi. thats why i think miniDSP engineers came up with nanoDIGI board!
2 hours ago Edited Unlike 1

Shivaprashanth S Hiremath i would say (with few ifs)
if you don't plan to use DSP for room EQ etc.
if you can afford
if you have finalized the xover points,
then...then...then
sticking to analog xovers (atleast opamp based) will give better results
all the so mentioned issues in the article will not be there. and you can expect to have same audio quality from the CDP/DAC
37 minutes ago Like
:Unquote


Regards

 

[tcpip]

Re: MiniDSP next steps

No emperical reason. essentially a choice exists. I have read gripes about the SRC on minidsp and possibly something like Jriver might be a better.

re: your point about volume control; the minidsp has a digital volume control. If you are anal about "losing bits" then you'd not use the volume control and use something downstream.

Is there a loss of bits in the volume control of the miniDSP? I am under the impression that this volume control is implemented by changing the reference voltage of the DAC at the very edge where the digital value gets converted to an analog voltage or current. If I am right, then the volume control is actually in the analog domain. But I need to confirm this, I'm not 100% certain.

edit : by full potential I meant beyond the biquads that you can generate with ACD or REW.(you'll remember we talked about the ACD spreadsheet before.) i am in an uncharted zone here, but apparently there is a lot more you can do with the DSP. bit don;t ask me exactly what.

Oh... in that case I guess I myself have not grown enough in my use of filters to want anything beyond the stuff which standard biquads give me. As I said earlier, I'll be very happy to use the MiniDSP as just a "programmable analog active xo", therefore all the usual second-order and first-order filters, the notches and peaks, the shelving filters, the LT, are the building blocks I hope to use. Don't know enough yet to want anything more.

 

[tcpip]

Re: MiniDSP next steps

1. Analog to digital conversion to native DSP sampling rate (potential source of degradation)
or
(For a digital source) Sample rate conversion from the input rate to the Native DSP rate (another potential source)

2. the processing - Minidsp uses IIR filters which are pretty efficient. (I do not want to get into an FIR versus IIR debate, since I have no experience of FIR filters)
3. the analog conversion - the DACs and their implementation defines the final output and in a DSP board that packs 8 within a price of 299USD, it probably is just not the latest cutting edge.

I was trying to see what options a DIY chap has for the input part (the A/D conversion). We all know there are lots of options for the DAC part, because DIY DACs are common.

For DIY ADC, I could find only one: the AD24QS from a DIYer in Germany who also sells kits. His ADC can do upto 24/192, appears to be of high quality, and is quite inexpensive (compared to a Buffalo DAC, let us say). I like the designer's perspective about subjective quality issues: "Would I hear the difference between a naked piece of wire and my converters I'd bet, there is something wrong with them. Or with the wire.". Quite Doug-Self-ish, I thought.

Are there affordable ESS 9018 DACs available? Even Chinese kits seem to be upward of USD 150 for a two-channel thing in most cases. Will a Buffalo 8-channel DAC be a good idea for my kind of application? The price per channel goes down with that kit.

 

[tcpip]

The project inches along. Enclosures are almost ready.

Fitting veneer is now taking up all the time of the carpenter chaps. The shape (the bevelling and odd angles) is making this a really difficult challenge for them.

As usual, more up-to-date details (and larger images) on this page.

In the meantime, the MiniDSP box has reached India, though it has yet to reach me.

PS: Also see the section on my page titled "Bracing, bracing ... yet again"

 

[kanwar]

Fantastic build Tarun....!!!

 

[tcpip]

Minor disaster

Now that both upper enclosures have been assembled, I got a chance to keep them side by side for the first time, and I saw what a disaster had taken place.

My carpenter has built lots of speakers, so he knows that when a driver is mounted offset, its position has to be mirrored in the two boxes. Yet, he did not detect his own screw-up while he cut the baffles, while he mounted the baffles, and while he spent days fitting the veneer. I feel like banging his head against the nearest hard surface.

Luckily, I don't have to buy any veneer, there is enough spare. But I will have to buy a 8'x4' sheet of 25mm MDF, because the dealer won't sell a part of a sheet. This means that I will waste about 75% of the MDF sheet. Probably will have to buy plywood too, for the internal bracing.

A really depressing day. One channel's upper enclosure will have to be completely rebuilt.

 

[ghatgepatil]

I know it is a major screw-up, but, would it make much of a difference in the SQ?! I guess not.

 

[kanwar]

Better make 2 more cabs with mirrored offset for tweeters so in that way you will have 2 pairs of cabs..........you can sell/gift one pair to someone who could be interested.

 

[tcpip]

Impact on sound quality -- well, the only impact will be on the soundstage. But probably the bigger impact will be on the psychological irritation at seeing an asymmetric pair of speakers staring at you whenever you want to sit down for a listen.

Making two more enclosures -- that's an interesting thought. But I will minimise my financial outlay for now, I think. I will just build a replacement and keep this (rejected) enclosure somewhere safe. Maybe I will actually act on your suggestion, but later someday. Let me get this mega-project off the ground and actually singing first.

I'm actually tired of the time and expense of this project -- it's the biggest project I've done so far, and I know the entire electronics (eight channels of amplification) are pending, not to speak of chassis, transformers, etc, etc.

Wish me luck.

 

[keith_correa]

Re: Minor disaster

Now that both upper enclosures have been assembled, I got a chance to keep them side by side for the first time, and I saw what a disaster had taken place.

Uh, oh! I feel your pain :sad:

 

[magma]

the bevelling screwed all the chances you had of flipping it

 

[GeorgeO]

Ahhh that hurts sirji..Something not too dissimilar happened to me last year,, so I can share the pain!

 

[tcpip]

the bevelling screwed all the chances you had of flipping it

It's not just the bevelling. The veneer had been stuck on. You can't flip it after that -- the veneer on the sidewalls would get ripped in the process. Moreover, the round cutout for the midbass driver is chamfered -- flipping it would give me a wide hole narrowing down inwards -- unusable.

 

[tcpip]

boxes are done

My carpenter has finally built a replacement upper box for the misaligned front baffle, and the job is done.

Now the four enclosures are ready bar the PU polish.

 

[tcpip]

The MiniDSP box has arrived

In my excitement, I asked the loudest speaker in my house to hold aloft the box so that I could click.

The chassis is made of sturdy steel, and the box feels well made. The volume knob is cheap plastic, finished like faux brushed aluminium, and fits by pressing into place on the serrated spindle of the rotary encoder. Have yet to power up the beast.

 

[ghatgepatil]

Finalized on the finish as yet? Veneer polish? Shades .. cherry or walnut? Its turning out to be nothing short of a classic! :licklips:

 

[tcpip]

Finalized on the finish as yet? Veneer polish? Shades .. cherry or walnut? Its turning out to be nothing short of a classic! :licklips:

Actually, as the photos show, the veneer has already been chosen, procured, trimmed and stuck on. I am using a dark veneer for the front "plate" of the front baffles. For all the bevelled cuts, sides, rears, tops, I am using a different, pale veneer. And since I will use natural-colour PU polish without any stain, whatever is in the veneer is what I will get finally.

Only the sound will tell me whether it is a classic or not. I haven't even started work on the amps. But thanks for the appreciation.

 

[jetlag]

Great build so far, tcpip. As you put it right, only SQ will tell which way the whole project has gone.

Peace
Jetlag

 

[tcpip]

Got the power transformers for my amps

Got my power transformers.

Each transformer has an R-core and eight secondary windings, which will give me four sets of centre-tapped rails. Each will thus power four amp channels in quasi-monobloc manner. Two transformers will go into two chassis to power a total of eight amp channels, out of which I will need only six for the Darbari.

Each transformer is rated at about 600W continuous output. Each secondary winding is 28V AC, 2.7 A. Got them from Delta Transformer. They sell with pucca bill, paying Excise and CST and they shipped to me. The total price including everything and shipping came to Rs.9,000 per transformer. Expensive, but very well built. If heft is a sign of quality in transformers, then these are hefty -- about 6kg each.