After hearing so much about MiniDSP projects and having gotten my appetite wet by the iDSP from OSD I bought one.
I had a rocky road with the iDSP app initially regarding to to the auto room correct function to generate FIR filters I got it ironed out.
I didn't use the iDSP for subs but instead used it in an expanded implementation with an XO at 300hz to the woofers in my speakers which were already designed as an active system to get better baffle step and LF room correction.
The IDSP is the same board as the Parts Express DSP unit but with 2v out in mono and nice RCA's vs 1/8" jacks. Same software as well.
I decided to try the Mini in my next active XO project and as a first step I substituted it for the iDSP in an already well sorted system.
The result using the panel to configure the Mini was terrible!! The filters had terrible ringing and a huge loss of transparency.
How could this be I asked myself. The iDSP is dirt cheap vs the Mini and the Mini has far fewer features relating to dsp built in to go wrong.
We all know the Mini panel is very basic but allows the more complex FIR filter import through either plugin (Dirac) or 3rd party FIR filter generators
It turns out that the Mini built ins are IIR filters for simplicity vs the FIR based iDSP and it is clearly audibly better with FIR based filters.
Unfortunately to access the much better sounding FIR based adjustments for the Mini we need to spend a bunch more, a WHOLE BUNCH MORE!!
As a baseline the iDSP has dynamics, phase, delay, limiters, Sub harmionic synthesizer, Dynamic bass control, parametric eq plus the XO up to 48db. The iDSP is doing all that via FIR based filters, which makes sense as IIR filters would fall apart with so many complex filters, and does it via the iPhone app and it's only $5 to buy the app vs hundreds for DIRAC or Eclipse Audio's program.
Granted in the grand view of what I have invested into my system several hundred bucks is cheap but having such great sound from a $50 unit has me pissed that it's going to cost and be far more complex of a process.
I had a rocky road with the iDSP app initially regarding to to the auto room correct function to generate FIR filters I got it ironed out.
I didn't use the iDSP for subs but instead used it in an expanded implementation with an XO at 300hz to the woofers in my speakers which were already designed as an active system to get better baffle step and LF room correction.
The IDSP is the same board as the Parts Express DSP unit but with 2v out in mono and nice RCA's vs 1/8" jacks. Same software as well.
I decided to try the Mini in my next active XO project and as a first step I substituted it for the iDSP in an already well sorted system.
The result using the panel to configure the Mini was terrible!! The filters had terrible ringing and a huge loss of transparency.
How could this be I asked myself. The iDSP is dirt cheap vs the Mini and the Mini has far fewer features relating to dsp built in to go wrong.
We all know the Mini panel is very basic but allows the more complex FIR filter import through either plugin (Dirac) or 3rd party FIR filter generators
It turns out that the Mini built ins are IIR filters for simplicity vs the FIR based iDSP and it is clearly audibly better with FIR based filters.
Unfortunately to access the much better sounding FIR based adjustments for the Mini we need to spend a bunch more, a WHOLE BUNCH MORE!!
As a baseline the iDSP has dynamics, phase, delay, limiters, Sub harmionic synthesizer, Dynamic bass control, parametric eq plus the XO up to 48db. The iDSP is doing all that via FIR based filters, which makes sense as IIR filters would fall apart with so many complex filters, and does it via the iPhone app and it's only $5 to buy the app vs hundreds for DIRAC or Eclipse Audio's program.
Granted in the grand view of what I have invested into my system several hundred bucks is cheap but having such great sound from a $50 unit has me pissed that it's going to cost and be far more complex of a process.
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The room correction, phase and crossover are FIR And are part of the paid app but The dynamics could be biquads - IIr and those are free. With the 48bd LR XO which can be done with both there is a clear difference between the 2. There is significant ringing beyond the passband that is easily heard with built in IIR’s. I have been playing with micro modeler to generate some filters and I will say it’s just as easy to screw up a filter as it is to make a good one. I have also discovered that the built-in IIR filters are generated from a chip programer that analog devices makes (soundscape)and they can be made more complex however it seems that the default is for easy processing and not optimal sound quality. this whole experiment is leading me down a path which may ultimately lead to having to DIY my own unit or make a big step towards some heavy duty pro studio grade gear. A local audio file Friend has the RME multi channel set up and it is really a big upgrade from the mini with regards to processing power and all of the hardware. It may be a more sane path for me.
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On a completely different note, I just heard from the engineers at PRV Audio and they said that the filters in their DSP2.4x and 2.8x are FIR filters and not IIR!
Probably too many adjustments to do multiple IIR filters and maintain integrity. No mention of how many taps though.
The iOSD is 512 taps but it is only for the woofer and no HP to mids so I use it with my Marchand XM9 for HP and do an assymetrical LR48 LP and LR24 HP with overlap and a slight DSP adjustment.
I tried the Mini at 24LR HP & LP and also 48LR HP & LP w 2036 taps and there is a loss of HF transparency with both however the bass range is cleaner and surprisingly more natural with 48db/48db.
Need a PS solution which is easy but the PRV is cheap enough to try so I ordered one from Amazon.
Probably too many adjustments to do multiple IIR filters and maintain integrity. No mention of how many taps though.
The iOSD is 512 taps but it is only for the woofer and no HP to mids so I use it with my Marchand XM9 for HP and do an assymetrical LR48 LP and LR24 HP with overlap and a slight DSP adjustment.
I tried the Mini at 24LR HP & LP and also 48LR HP & LP w 2036 taps and there is a loss of HF transparency with both however the bass range is cleaner and surprisingly more natural with 48db/48db.
Need a PS solution which is easy but the PRV is cheap enough to try so I ordered one from Amazon.
What Minidsp model? Using analog in/out or digital?
Try this: disable every filter in the minidsp so it should act as a straight through box. Insert it in your existing system between your preamp out and iDsp input (thus using only two outputs). If you still find the sound degraded you'll know it's not the IIR filters setup but the ADC/DAC of the mini.
Try this: disable every filter in the minidsp so it should act as a straight through box. Insert it in your existing system between your preamp out and iDsp input (thus using only two outputs). If you still find the sound degraded you'll know it's not the IIR filters setup but the ADC/DAC of the mini.
I spent most of the day learning the new PRV unit and comparing it with the mini 2 x 4 HD. I wrote down an extensive set of notes that I’m going to try to condense. The bottom line is the PRV sounds incredibly good and does not seem as muffled as the mini. I think a lot of that comes from the higher output voltage that the PRV has which is 4.5 V. I also opened both, took pictures and notes and came up with a game plan for mods. Neither unit has particularly noteworthy op amps, bottom of the barrel actually as far as opamps are concerned so there’s plenty of room for improvement and I’m sure that has a significant effect on both units. The PRV is a steal at the current price. Replaced some of the op amps with AD8599’s And I’m letting those settle in Overnight and we’ll see what that brings tomorrow.
I have the 2x4HD and using analog input. I did a comprehensive test against the PRV as well as methodical 1 mod at a time to both that I will post once I clean up my notes. Bottom line is there is room for a SIGNIFICANT upgrade in sonics to both and the most impactful mod is the simplest!!!
Like everything it comes down to cost cutting measures by the manufacturers and how to overcome them. In the end I prefer the PRV and unless you need to do full range room correction you will get better sq from the modded PRV.
My personal experience with the 2x4hd is that the ADC is very poorly implemented. Try bypassing it by switching to digital input, made a huge improvement in my system. The DACs are not as terrible as the ADC but still mediocre at best. The I2S signals for the DACs are available on the internal header so it should be possible to hook up external DACs.
I had mentioned I was also looking into the PRV unit above and after my discussion with the engineers at PRV I decided to go ahead and try one since they were available at just under $100! I received the unit and in typical DIY fashion popped the cover to look under the hood. There’s some good and bad in there.
The good definitely outweighs the bad and some of the nice things are that the op amps are easily accessible and even though they are SMD they can be upgraded which really is going to be a boost because they are the much-maligned 4558. Like the MiniDSP it is also capacitor coupled input and out. I measured mine and there was no DC on the output before the caps so bypassing those or upgrading is definitely something easy. Another nice feature is the PRV is designed for automotive use so it has some pretty hefty filtering and regulation being that a lot of these modified auto installs have upgraded alternators and devices that can make a good bit of noise and needs to be mitigated. The PRV also has much higher output levels and drive. Even with the mediocre 4558 op amp there is significantly higher drive and dynamics. PRV mentions 4.5 V out!
Now relating to sound quality. This was in no way A fully exhaustive test however the main goal here was to see how the units performed as active crossovers. I specifically wanted to get 48 DB LR filters as some prior experience with the MiniDSP was promising. My experience was lackluster. While the PRV had more life and drive it seems like neither unit was resolving the subtle things that are typical high fidelity characteristics. Both units were used as analog input with gains at unity and the amplifier input sensitivity had to be reduced for the higher output level of the PRV. The Mini was first setup with the built in filters in the panel and the result was horrible! I later built FIR filters with rePhase and the result was far better with no heavy out of band ringing. I did not experience the heavy ringing with the PRV. Out of the box the PRV sounds better but still lacking.
Now onto the mods. I did a methodical single mod at a time procedure and only listened to 1 channel in mono and left the other set of channels as a control when applicable. I upgraded input caps, bypassed output caps , upgraded opamps, tried 3 different power supplies and did internal PS tweeks.
Cutting to the chase it looks like the chipset that is responsible for the AD conversion is extremely sensitive to noise on the 3.3v supply and the ceramic chip at the Vdd input benefits TREMENDOUSLY by adding a good size OSCON to it. 270uf@6.3v The benefit is tremendous and is a far greater bump in low level resolution than any other mod I mentioned. The other mods, opamps, input caps and boutique power supplies are just seasonings. The bypassing on the chip that does the AD conversion has a HUGE impact on the "you are there " low level realism. I also was easily able to increase the PRV +12 -12 analog supply caps easily as there are test points you can tap into. The Analog +12_-12v cap increase helped with bass solidity.
After similar mods to both units the effects were comparable with the OSCON being the biggest improvement on both units. It seems that the AD conversion is also what many say is the weak point and I look forward to hearing others impressions.
I will upload detailed pics in a few minutes.
The good definitely outweighs the bad and some of the nice things are that the op amps are easily accessible and even though they are SMD they can be upgraded which really is going to be a boost because they are the much-maligned 4558. Like the MiniDSP it is also capacitor coupled input and out. I measured mine and there was no DC on the output before the caps so bypassing those or upgrading is definitely something easy. Another nice feature is the PRV is designed for automotive use so it has some pretty hefty filtering and regulation being that a lot of these modified auto installs have upgraded alternators and devices that can make a good bit of noise and needs to be mitigated. The PRV also has much higher output levels and drive. Even with the mediocre 4558 op amp there is significantly higher drive and dynamics. PRV mentions 4.5 V out!
Now relating to sound quality. This was in no way A fully exhaustive test however the main goal here was to see how the units performed as active crossovers. I specifically wanted to get 48 DB LR filters as some prior experience with the MiniDSP was promising. My experience was lackluster. While the PRV had more life and drive it seems like neither unit was resolving the subtle things that are typical high fidelity characteristics. Both units were used as analog input with gains at unity and the amplifier input sensitivity had to be reduced for the higher output level of the PRV. The Mini was first setup with the built in filters in the panel and the result was horrible! I later built FIR filters with rePhase and the result was far better with no heavy out of band ringing. I did not experience the heavy ringing with the PRV. Out of the box the PRV sounds better but still lacking.
Now onto the mods. I did a methodical single mod at a time procedure and only listened to 1 channel in mono and left the other set of channels as a control when applicable. I upgraded input caps, bypassed output caps , upgraded opamps, tried 3 different power supplies and did internal PS tweeks.
Cutting to the chase it looks like the chipset that is responsible for the AD conversion is extremely sensitive to noise on the 3.3v supply and the ceramic chip at the Vdd input benefits TREMENDOUSLY by adding a good size OSCON to it. 270uf@6.3v The benefit is tremendous and is a far greater bump in low level resolution than any other mod I mentioned. The other mods, opamps, input caps and boutique power supplies are just seasonings. The bypassing on the chip that does the AD conversion has a HUGE impact on the "you are there " low level realism. I also was easily able to increase the PRV +12 -12 analog supply caps easily as there are test points you can tap into. The Analog +12_-12v cap increase helped with bass solidity.
After similar mods to both units the effects were comparable with the OSCON being the biggest improvement on both units. It seems that the AD conversion is also what many say is the weak point and I look forward to hearing others impressions.
I will upload detailed pics in a few minutes.
Sorry guys.
I thought thread originator was using the miniDSP 2x4, thus I posted above some ref material for this old board with ADAU 1701 processor.
But on a later post he mentioned the 2x4 HD which has the ADSP-21489, a much higher speed processor.
Now if this is a BGA package, the extra bulk decoupling capacitor he suggests, should be connected btn VDD_THD pin 112 and where the bottom side ground pad of the package is soldered to. That's a bit difficult to locate. But as high value capacitors don't need to be very close to the IC power pin, this large capacitor can be placed at a more easy to access place, e.g. at the output of the 3.3V DC/DC converter (I don't have the PCB layout).
George
I thought thread originator was using the miniDSP 2x4, thus I posted above some ref material for this old board with ADAU 1701 processor.
But on a later post he mentioned the 2x4 HD which has the ADSP-21489, a much higher speed processor.
Now if this is a BGA package, the extra bulk decoupling capacitor he suggests, should be connected btn VDD_THD pin 112 and where the bottom side ground pad of the package is soldered to. That's a bit difficult to locate. But as high value capacitors don't need to be very close to the IC power pin, this large capacitor can be placed at a more easy to access place, e.g. at the output of the 3.3V DC/DC converter (I don't have the PCB layout).
George
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I have a minidsp2x4HD that I plan to put in a box for use as an XO so I'm quite interested to learn more about what mods are worth the effort (and what aren't).
FYI - I am only using simple first order filters but don't want to go to Analogue XO because I want the time-delay capability of the DSP that I can't do in analogue (Vitavox K-horn has 6ms time difference between top and bottom horns).
FYI - I am only using simple first order filters but don't want to go to Analogue XO because I want the time-delay capability of the DSP that I can't do in analogue (Vitavox K-horn has 6ms time difference between top and bottom horns).
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Joined 2009
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That's a darn good question and I've had it in my mind too, but - no, I haven't done that yet. Maybe I'll try that this weekend.
And if there's no benefit to the time delay then why bother with the digital approach - I still like the benefits of bi-amping but I can see how an active analogue line level XO could work too.
And if there's no benefit to the time delay then why bother with the digital approach - I still like the benefits of bi-amping but I can see how an active analogue line level XO could work too.
Thanks
I ask because the content of my aged scalp can't recognise such acoustic delays, at least between the sub and the main woofers.
The old miniDSP 2x4 have paid their price to the x500 during these 10+ years I make use of them.
I've purchased N.P. x-overs from the store 1-2 years ago, I have yet to assemble them. I am still reluctant to withdraw the miniDSPs.
Oh, the ease of changing parameters!
George
I ask because the content of my aged scalp can't recognise such acoustic delays, at least between the sub and the main woofers.
The old miniDSP 2x4 have paid their price to the x500 during these 10+ years I make use of them.
I've purchased N.P. x-overs from the store 1-2 years ago, I have yet to assemble them. I am still reluctant to withdraw the miniDSPs.
Oh, the ease of changing parameters!
George
Member
Joined 2009
Paid Member
In the case of my Vitavox clone, the XO is at 450Hz and 1st order means lots of overlap so timing differences are spread out somewhat. I don’t have any idea if that’s good or bad.
The minidsp is a handy tool, I’m interested in mods regardless and so I hope this thread offers some helpful guidance 👍
The minidsp is a handy tool, I’m interested in mods regardless and so I hope this thread offers some helpful guidance 👍