Vintage amp and powered sub - a question about MiniDSP

[lbcgav]

I've just purchased some KEF Q100's and an SVS SD12-NSD sub. I'm planning on using a Y splitter to send the low level signals from the pre-out of my Accuphase E-202 to the sub and the other half back into the Power-in of the same amp. This would pass the full frequency range to the KEF's.

I'd like to know if getting a MiniDSP would be worthwhile or would the Y-splitter setup be just as good. I don't want to spend the money to find out that it wouldn't make any difference.

 

[Nightwisher]

It depends on how you want to tweak it. As a MiniDSP owner (I own the original 2x4 and the 2x4HD), I highly recommend them. The MiniDSP allows for equalization, crossovers (high pass and low pass filters), and delays. It can easily be used with measurements using Room EQ Wizard and a microphone, allowing for precise integration. The tweaks you can do with these are endless. Now, Dirac is available as an upgrade over the base MiniDSP software for the 2x4HD, which is the most powerful DSP software in the world (or right up there in the top handful).

In the setup you propose, the sub has its own low pass filter, however there's no high pass filter on the speakers. This can lead to muddy bass and bass cancellations as both speakers and sub output some of the same frequencies. Setting delays, I find, is crucial to subwoofer integration as well. The added bonus of being able to precisely EQ to the room is nice.

So, I find it makes every bit of difference, but that's my opinion. I used a Y-splitter before I upgraded to the MiniDSP and I would never go back to the splitter alone.

 

[lbcgav]

Nightwisher, thanks for the detailed response. I think I'll setup everything first using the splitters and see how things work out and go from there. Do you know of any step-by-step tutorials that walks you through the setup of the MiniDSP in 2.1 configuration?

 

[slobmw]

Nightwisher, thanks for the detailed response. I think I'll setup everything first using the splitters and see how things work out and go from there. Do you know of any step-by-step tutorials that walks you through the setup of the MiniDSP in 2.1 configuration?

Splitters are cheap, so starting there makes sense. But the link you want is below.

https://www.minidsp.com/applications/digital-crossovers/subwoofer-integration-with-minidsp

 

[whoaru99]

Nightwisher, thanks for the detailed response. I think I'll setup everything first using the splitters and see how things work out and go from there. Do you know of any step-by-step tutorials that walks you through the setup of the MiniDSP in 2.1 configuration?

The sub you are looking at has fixed 80Hz line level high pass filters built-in.

So, you could use the Y cables to split the signal and run the KEFs full range. Or, you could run the pre outs to the sub line inputs then the sub line outs back to the main in on the amp for high pass on the KEFs.

I suggest trying it both ways first, for starters.

 

[lbcgav]

After doing a bit of reading on the miniDSP, I've got a question concerning which version to use, the .9V or the 2V version. My Accuphase E-202's preamp output is 1V. Should I get the .9V version or the 2V version with a 1V output preamp?

 

[Nightwisher]

After doing a bit of reading on the miniDSP, I've got a question concerning which version to use, the .9V or the 2V version. My Accuphase E-202's preamp output is 1V. Should I get the .9V version or the 2V version with a 1V output preamp?

Either one will work. Obviously the .9V version limits output slightly, but unless you crank it up all the way, it's not significant.

However, I recommend the 2x4HD if you can swing the higher price. It's a better machine with better software than the original (and the ability to upgrade further to Dirac), allowing you to get the most out of it.

 

[lbcgav]

If I used it solely as a crossover with some EQ, would there be a noticeable difference between the 2X4 and the 2X4HD?

 

[whoaru99]

After doing a bit of reading on the miniDSP, I've got a question concerning which version to use, the .9V or the 2V version. My Accuphase E-202's preamp output is 1V. Should I get the .9V version or the 2V version with a 1V output preamp?

I believe the setting can be changed by opening it and moving a jumper or two. 0.9V or 2.0V options are just how you want it set up at the factory.

While it is slightly different beast, I have a miniDSP 2x4 Balanced and can attest the voltage scales are easily changed by internal jumpers.

The consideration in voltage is with analog input relative to the scaled input of the ADC. For the best operation you want the incoming signal as close as possible to the max voltage, without going over.

For example, say it is a 16-bit ADC with 0.9V input scale. That means the 0V to 0.9V range will be represented by 65536 individual values (0 to 65535). As you see, to get the full resolution capability, ideally the signal would use the full range possible. Of course, if you go over then that's not good because there no more values left to properly represent the signal.

If the input is scaled to 2V, there are still the same 65536 values but each value is a bigger chunk. So, if you input only 0.9V on the 2.0V setting you'd be using less than half the available resolution.

In most cases the signal will be less than 0.9V so I'd probably start with that setting. Again, far as I know, it can be easily changed if that doesn't work out.

Potentially a bigger concern though is the 2x4 max output of 0.9V regardless of the input setting. If you have amplifier that requires more than 0.9Vrms to achieve the level of output you want the miniDSP 2x4 itself will not be capable. Bear in mind though, 0.9V into most amps would be pretty loud so it may be OK despite that limitation.

 

[lbcgav]

I believe the setting can be changed by opening it and moving a jumper or two. 0.9V or 2.0V options are just how you want it set up at the factory.

While it is slightly different beast, I have a miniDSP 2x4 Balanced and can attest the voltage scales are easily changed by internal jumpers.

The consideration in voltage is with analog input relative to the scaled input of the ADC. For the best operation you want the incoming signal as close as possible to the max voltage, without going over.

For example, say it is a 16-bit ADC with 0.9V input scale. That means the 0V to 0.9V range will be represented by 65536 individual values (0 to 65535). As you see, to get the full resolution capability, ideally the signal would use the full range possible. Of course, if you go over then that's not good because there no more values left to properly represent the signal.

If the input is scaled to 2V, there are still the same 65536 values but each value is a bigger chunk. So, if you input only 0.9V on the 2.0V setting you'd be using less than half the available resolution.

In most cases the signal will be less than 0.9V so I'd probably start with that setting. Again, far as I know, it can be easily changed if that doesn't work out.

Potentially a bigger concern though is the 2x4 max output of 0.9V regardless of the input setting. If you have amplifier that requires more than 0.9Vrms to achieve the level of output you want the miniDSP 2x4 itself will not be capable. Bear in mind though, 0.9V into most amps would be pretty loud so it may be OK despite that limitation.

Ok, that's along the lines of what I was thinking. I think the .9 input and output will be just fine. I don't ever see using the full volume of the E-202, which would result in 1V of output from the preamp.