2.1 system with miniDSP digital to DAC and analog to SUB

[gabrielb]

Hi,
I'm trying to find an easy way to integrate powered subwoofer into a stereo system.
My system is using a single source: foobar2000->Benchmark DAC3(USB)->Benchmark AHB2 Power AMP -> Gamut Phi5 floorstanding speakers.

I want to keep the Benchmark setup (DAC + AMP) while adding a powered subwoofer to help the Gamut speakers.
I want a transparent box which can control the volume digitally and crossover the frequencies between the SUB and the main system.
I assume this could be done on the computer in SW (maybe even inside foobar2000?), but I rather use an external physical box with a knob and remote.

I am thinking of inserting miniDSP Flex (or any other product) between the computer and the DAC and let it control the volume and send the high frequencies in *digital* format to the benchmark DAC3 and the low frequencies in *analog* format to the SUB.
Can it be done?
Can miniDSP output one stream in digital format while running DAC function on the second stream before sending to the SUB?

This is a simple scheme of the end result:
foobar -> miniDSP -> (digital) Benchmark DAC3 -> Benchmark AHB2 Power AMP -> Gamut Phi5 floorstanding speakers
||
(miniDSP DAC function) ==> powered subwoofer

 

[staticV3]

I am thinking of inserting miniDSP Flex (or any other product) between the computer and the DAC and let it control the volume and send the high frequencies in *digital* format to the benchmark DAC3 and the low frequencies in *analog* format to the SUB.
Can it be done?
Can miniDSP output one stream in digital format while running DAC function on the second stream before sending to the SUB?

No. The only Flex with Digital out is the Flex Digital, which has no analog outputs.

You could buy a second DAC for the Flex Digital, exclusively for the subwoofer.

However, you'd have to make sure that neither DAC does any sort of reclocking when using SPDIF, to ensure consistent phase response between DACs.

 

[gabrielb]

Thanks!
I can probably live with the Flex-Digital and chain another DAC between the miniDSP and the SUB (or simply move the DSP to the computer and connect both DAC to the computer).
IIRC Benchmark DAC3 does reclock (probably happens on every ASYNC DAC) can that be mitigated by adding delays between the 2 channels on the miniDSP (or on the computer)?

 

[staticV3]

can that be mitigated by adding delays between the 2 channels on the miniDSP (or on the computer)?

The issue is clock drift. Adding a delay has no effect on that.

 

[JustJones]

You could set the crossovers and DSP in a regular Flex or SHD and get rid of the DAC which would be the easiest solution.

 

[staticV3]

You could set the crossovers and DSP in a regular Flex or SHD and get rid of the DAC which would be the easiest solution.

OP wants to keep the Benchmarks:

I want to keep the Benchmark setup (DAC + AMP)

 

[gabrielb]

I wish to keep the the original setup with Benchmark DAC and AMP working together.
The Benchmark DAC outputs an extra unbalance analog left/right stream (in addition to the balanced stream).
In theory I could route the second stream to a powered sub using the sub's low-pass-filter to accept only frequencies below 50-60Hz
(The frequency response on my main speaker is reported as +/- 3dB 42-40.000 Hz)

The volume could be set in unison in the digital domain (with some adjustment on the SUB) and maybe I could also use the SUB phase control to adjust the timing.

Will that work or that having an overlap between the SUB and the main speakers (42 - 60 HZ) will cause a problem?
Also, since the main speakers frequency range is so wide I suspect it is under performing in its lowest frequencies so filtering them should be an improvement (pure speculation as I don't know how to measure this).
Should I try and add a passive high-pass-filter before the AMP or the main speakers or that will distort the signal?

 

[Ron Texas]

The simple solution is sell the Benchmark DAC and get a MiniDSP Flex with analog outputs. Chaining DAC's doesn't improve anything and just increases the chance for bad connections or hum.

 

[gabrielb]

I spoke with Benchmark customer service and got an interesting suggestion:
Connect the XLR output from the DAC3 to the AHB2 Power-Amplifier and the RCA output from the DAC3 to a self-powered SUB/s.

DAC3 == (XLR) ==> AHB2 ==> passive main speaker
||
(RCA) ==> powered subwoofer

Boost the volume on the self-powered SUB/s to a higher level than the volume on the main-speakers -> this will cause imbalance in the low frequencies of course.
Add a DSP upstream before the DAC3 to lower the volume (amplitude??? gain???) *only* on the low frequencies to rebalance the system.
In theory that could be done manually, but in reality will probably run DIRAC or something similar to automatically correct the imbalance created by me setting the SUB volume too high.

This way the low frequencies will still reach the AHB2 power-amplifier and the main speakers, but at a much lower volume (I'm missing the correct term here).
The end results will be that the main speaker will act as a secondary on the LF and whatever distortion they are causing when pushed to their limits will be greatly reduced.

I *think* that by lowering the LF required power on the speakers they won't struggle that much and might even cause less of a distortion when outputting the LF.
I also *speculate* that the AHB2 power amplifier will be less stressed for power since the LF will arrive at lower volume (amplitude ??? gain ??) allowing it to operate at a higher overall power.

Using the same DAC to control both the main-speakers and SUB/s will guarantee that they will operate in sync and that a phase correction on the SUB/s or DIRAC can correct any latency problem since it will be constant.

(Please forgive my ignorance and feel free to correct me with the right term for lowering the volume on the low frequencies in DSP)