indus

Adding a subwoofer to 2ch system

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The merging Nadac 8 channel would seem a nice way of doing it for computer sources (x-over / DSP on the PC), can't imagine it's cheap , but reassuring to know if you like the sub you have enough channels to add another 5...

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47 minutes ago, indus said:

You're probably right about the DSpeaker. However there is another problem, it won't actually allow me to divert the selected frequencies to the sub, I know this can be done via the speaker inputs on subs but I really don't think that would be a good solution.

So what I think I actually need is a crossover of some kind. However I don't want multiple AD/DA conversions so I think what I need is a DAC/pre that also has bass management. Rather than a DAC and a separate external crossover

I'm looking for a new DAC right now, so I suppose I should find one that does bass management. I've just bought an ex dem Moon CD Transport and was hoping to keep it all Moon and buy a Moon dac. But I'm pretty sure it doesn't have this facility so will have to look elsewhere.

Are all your sources digital ? If they are then you can do the frequency shaping in the digital domain and feed the two separate digital streams (the 'high-frequency' one and the 'bass' one) to two separate DACs (strictly four DACs of course, assuming your set-up is stereo). That will give you complete control of all the shaping parameters. The basic miniDSP box has that capability https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd.

If one or more of your sources is analog and if you won't allow the signal from it (them) to be digitised than you'll have to have an analog crossover and settle for more limited frequency shaping. The crossover can be fed via a switch to select the pure analog source(s) or the output from your DAC.

You also seem to be sensitive about where the various building blocks of your system live. For example you want a filter to select frequencies for the sub and you're happy for that filter to be in a DAC/Pre box but not happy for it to be in the sub box. I'm not sure what the reasoning is there. The filter will either be at one end of the interconnect or the other. If the interconnect is just a transparent piece of wire then why would it matter which end the filter is ? The same applies for "... a DAC/Pre that also has bass management. Rather than a DAC and a separate external crossover". Those two differ only in how many boxes there are around the filters.

VB

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3 hours ago, SergeAuckland said:

I really don't understand the reluctance for one more ADC/DAC in the chain. Maybe this is what Graeme was referring to above about engineers not caring, whilst hobbyists do. 

I have all my sources going through an ADC/DAC, pretty much every recording has multiple passes through ADCs, DACs, and SRCs to boot. It's just a non-issue as far as I'm concerned. But then I'm an engineer, I would say that wouldn't I?

S. 

The only reason I'm reluctant is because I thought it was accepted wisdom that multiple conversion steps were a bad idea. At present I do have multiple conversion steps but as I'm looking to shake up my system I thought it might be better to simplify it.

The other way I look at it is whats the point of buying an expensive dac if further down the chain you have a cheaper/lower quality dac? Won't the end result be dependent on the weakest link in the chain?

2 hours ago, Valvebloke said:

Are all your sources digital ? If they are then you can do the frequency shaping in the digital domain and feed the two separate digital streams (the 'high-frequency' one and the 'bass' one) to two separate DACs (strictly four DACs of course, assuming your set-up is stereo). That will give you complete control of all the shaping parameters. The basic miniDSP box has that capability https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd.

If one or more of your sources is analog and if you won't allow the signal from it (them) to be digitised than you'll have to have an analog crossover and settle for more limited frequency shaping. The crossover can be fed via a switch to select the pure analog source(s) or the output from your DAC.

You also seem to be sensitive about where the various building blocks of your system live. For example you want a filter to select frequencies for the sub and you're happy for that filter to be in a DAC/Pre box but not happy for it to be in the sub box. I'm not sure what the reasoning is there. The filter will either be at one end of the interconnect or the other. If the interconnect is just a transparent piece of wire then why would it matter which end the filter is ? The same applies for "... a DAC/Pre that also has bass management. Rather than a DAC and a separate external crossover". Those two differ only in how many boxes there are around the filters.

VB

VB, all my sources are digital but I'm going to have to scratch my head over your post as some of it has gone over my head. I have no idea how I would create these two digital streams you talk of.... and are you talking about using the minidsp to act as my primary DAC?? I don't think that little box of tricks is going to give me the sound quality I'm after.

The reason I was reluctant to have the filter in the sub maybe due to my misunderstanding of the subject. I was led to believe that doing it in the sub was more hit and miss and it also meant that every time you changed the volume at source you would then have to change the sub volume to match.

And the reason for preferring DAC/pre with bass management to DAC with separate cross over was again due to the number of DA/AD steps. With a dac/pre with BM I'm assuming there is one DA step. With a DAC + separate crossover I'm assuming the crossover performs another AD and then DA step?

I'm probably talking complete nonsense, this whole subject has confused me to be honest!

2 hours ago, MikeG said:

image.thumb.png.219a043043a82ff5e07aa9923ff86132.png

image.thumb.png.61edbc8ead4b7bedfd0d3272632add21.png

The merging Nadac 8 channel would seem a nice way of doing it for computer sources (x-over / DSP on the PC), can't imagine it's cheap , but reassuring to know if you like the sub you have enough channels to add another 5...

image.png

Thanks, will look into that, more reading to do!

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48 minutes ago, indus said:

The only reason I'm reluctant is because I thought it was accepted wisdom that multiple conversion steps were a bad idea. At present I do have multiple conversion steps but as I'm looking to shake up my system I thought it might be better to simplify it.

The other way I look at it is whats the point of buying an expensive dac if further down the chain you have a cheaper/lower quality dac? Won't the end result be dependent on the weakest link in the chain?

VB, all my sources are digital but I'm going to have to scratch my head over your post as some of it has gone over my head. I have no idea how I would create these two digital streams you talk of.... and are you talking about using the minidsp to act as my primary DAC?? I don't think that little box of tricks is going to give me the sound quality I'm after.

The reason I was reluctant to have the filter in the sub maybe due to my misunderstanding of the subject. I was led to believe that doing it in the sub was more hit and miss and it also meant that every time you changed the volume at source you would then have to change the sub volume to match.

And the reason for preferring DAC/pre with bass management to DAC with separate cross over was again due to the number of DA/AD steps. With a dac/pre with BM I'm assuming there is one DA step. With a DAC + separate crossover I'm assuming the crossover performs another AD and then DA step?

I'm probably talking complete nonsense, this whole subject has confused me to be honest!

Thanks, will look into that, more reading to do!

That may have been the case in 1980, but ADC&DAC processes have been transparent for a very long time, so of no issue as far as I'm concerned. 

The suggestion of two digital paths is what I did when I had my Meridian 'speakers which only had digital inputs. I had an ADC for my analogue sources, and that and the CD player and Squeezebox were switched. S-PDIF or AES-EBU are very rugged indeed, and I just used a standard passive analogue switch to select whichever stream I was interested in. Over the short distances in domestic systems, just about any switch will work fine. 

S

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4 hours ago, indus said:

VB, all my sources are digital but I'm going to have to scratch my head over your post as some of it has gone over my head. I have no idea how I would create these two digital streams you talk of.... and are you talking about using the minidsp to act as my primary DAC?? I don't think that little box of tricks is going to give me the sound quality I'm after.

Creating the two digital streams is what the miniDSP box does. You hook it temporarily to a laptop using its USB connector and program the two frequency responses that you want (one for the sub and one for the high-frequency system) using software that you buy with it. Once it's programmed you can disconnect the laptop and you get left and right bass out of one pair of RCAs and left and right high-frequency out of the other pair. If you're only using one sub then the software can cope with that too. If you judge sound quality by whether the box is 'little' or not then you might well have a problem with this (you could always put it in a bigger box though :D). But the DAC is spec'd for 0.001% distortion + noise, 24-bit resolution and 103dB dynamic range. So it's no slouch.

4 hours ago, indus said:

The reason I was reluctant to have the filter in the sub maybe due to my misunderstanding of the subject. I was led to believe that doing it in the sub was more hit and miss and it also meant that every time you changed the volume at source you would then have to change the sub volume to match.

If you don't have any measurement kit then integrating a sub with a pair of high-frequency drivers will always have to be done by ear, and I agree that can be very hit and miss. But how good a job you can do will depend both on how good your ears are and how much control you have over the frequency response filtering. Some subs will have more capable filters than others and if you're working with one which is a bit primitive then you might well find that you can do better with an external crossover than with the sub's own one. If your master volume control is at the source though then you won't have to fiddle with the sub's volume control separately each time you change the master volume*.

4 hours ago, indus said:

And the reason for preferring DAC/pre with bass management to DAC with separate cross over was again due to the number of DA/AD steps. With a dac/pre with BM I'm assuming there is one DA step. With a DAC + separate crossover I'm assuming the crossover performs another AD and then DA step?

I was thinking you'd use an analog crossover here. A DAC/pre with BM will either do the bass management before the DAC, exactly like the miniDSP box, or after it, in which case the crossover would have to be analog, like the Ashly. One thing a pre might get you though is multiple digital inputs. The basic miniDSP box only has one digital input, so with multiple digital sources you'd need a digital switch before it, or you'd need to plug and unplug the digi connectors as necessary.

VB

*Unless you're bothered by the Fletcher-Munson thing. Back in the early days of hi-fi customers were constantly told that if you wanted a recorded piano to sound like a piano then you'd have to play the record at the correct volume for a piano. If you chose to play it quieter or louder then the ear's peculiar characteristics, which were optimised for hearing predators creeping up on us on the African savannah, would make a too loud or too quiet piano sound 'wrong'. But few people seem to care about this these days.

Edited by Valvebloke

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