how bad is a 4 way active miniDSP with 4 different amplifer

I'm just wondering for the case of my build as stated on the title and posted here : Ultimate Open Baffle Gallery

my inventory right now :
Behringer nu3000dsp (class d) : might be good for subwoofer
aragon2004 (class AB), mauro penasa GC : might be good for woofer
3 class a amplifier : might be good for midrange
Tripath : might be good for tweeter


my question would be : theoretically or based on consensus, is it good idea to mix these 4 different type amplifier?

or maybe i should use same type amplifier for all of them, just vary supply voltage? like this one : 2 PeeCeeBee V4H 56Vdc for Sub&Woofer and 2 V4 35Vdc for Mid/High. but this will require new budget and time to build
 

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I suspect that you are about to drown in a sea of opinion...

From a technical perspective there is no issue with mixing the amplifiers. You just need to set the levels (gains) correctly. But that is natural for and active crossover, and the varying efficiencies of the drivers mean the amplifiers will all be at different levels.

Then you can wrap in the second level of opinion. Class A, Class D and AB.

My take would be to use the most powerful amplifier for sub, next for mass-mid, mid and twt respectively. I do kind of prefer linear amplifiers, but have used CLASS D and have not suffered actual physical harm from the sound. :). Unless one is really crud, you should be OK.

If you don't like the sound then I am sure you can change later.
 

billshurv

Member
Paid Member
2014-03-01 11:53 pm
Why would it be bad? When going active the power requirements of different drivers means that a standard model for all 4 ways is not likely to be optimal anyway. MiniDSP allows you to adjust all the gains to match so I would press on and just do it. You can always replace amplifiers down the line.
 
I suspect that you are about to drown in a sea of opinion...

From a technical perspective there is no issue with mixing the amplifiers. You just need to set the levels (gains) correctly. But that is natural for and active crossover, and the varying efficiencies of the drivers mean the amplifiers will all be at different levels.

Then you can wrap in the second level of opinion. Class A, Class D and AB.

My take would be to use the most powerful amplifier for sub, next for mass-mid, mid and twt respectively. I do kind of prefer linear amplifiers, but have used CLASS D and have not suffered actual physical harm from the sound. :). Unless one is really crud, you should be OK.

If you don't like the sound then I am sure you can change later.
Why would it be bad? When going active the power requirements of different drivers means that a standard model for all 4 ways is not likely to be optimal anyway. MiniDSP allows you to adjust all the gains to match so I would press on and just do it. You can always replace amplifiers down the line.

most of 3/4ways active build that i find use Ncore or Sure which is not cheap. currently my product choice is to match amplifier & drivers based on power rating, i will clear up my thoughts not to worry so much now, i will just try and mix them all


with good amps, wouldn’t the performance be limited at the end by the DAC’s in the miniDSP ?
Even with mediocre amps you’ll be limited by the miniDSP ADCs.

The only way to make the miniDSP work properly for multiway speakers is to move the volume control to after the DSP, so for an active 4-way you’ll need an eight-way pot.

Otherwise you run out of bits in the ADCs really fast at normal listening levels.
there is another worry that i might downgrade the output from my AD1865 dac to minidsp ADC but for a while i skip this, just focus on amplifier first. but the options are available to use this active toslink splitter or split usb output from laptop, plus quad volume attenuator

Neoteck 3 Port Toslink Digital Audio Splitter 1 In 3 Out
AliExpress

YS HIFI 4-Channel Relay Volume Control Board Potentiometer ALPS AC12V-18V
AliExpress
 
I disagree, but been round this argument so many times about miniDSP on this forum that I really cannot be bothered to do it again....

Bill - I'd be interested to learn more, many of the DSP threads are long or over my head - if you can point me to some relevant posts I'd be grateful as I'm considering going miniDSP myself.

Also - I see some comments (like mine) about the DACs but also there are comments about the ADC. It fully makes sense to scale the analogue input signal to gain the full dynamic range of the ADC but that doesn't mean the internal digital volume control needs to be 'replaced' by an external 4-way pot ?
 
@Bigun

if you're concerning about Quality over minidsp, Nothing good comes in Cheap. but this kit might tease you a bit better instead of 2x4HD.

Hi-end DSP based multi-channel integrated Preamp/Crossover/DAC project

but for $200, i don't think there is any kit out there can beat 2x4HD.

if you want to make better dac and analog stage, get Minisharc kit and build/buy 8 channel dac, spdif or i2s. you can go crazy with 4 stereo dac of R2R or AD1865/TDA154x or use Sabre9038pro multichannel dac

I don't like digital volume control, it can go kabooom to full volume accidentally just by misplacing volume button or your child abuse. it happened on me for TV and car audio. I always put analog potentiometer on my audio stage to ensure 0 volume at start and better slow tracking
 

billshurv

Member
Paid Member
2014-03-01 11:53 pm
Bigun: have a read here Review: MiniDSP 4x10HD– Neurochrome which are the measurements of a 4x10HD, which should be the same as the 2x4HD. That's the whole chain using analog in. Nothing to me leaps out as 'OMG think of the children'.



I go digital into my miniDSP so only the DACs to worry about. I have I2S pins on the board so should i get advanced audiophilia nervosa I can change the DACs at a later date.


In terms of digital volume control I accept that the lack of a front panel readout is a pain, esp when little darlings can reach and twiddle. But for most of us 20dB of volume adjustment is the most we use, and that can be handled digitally with no resolution loss as long as you get the gain balance right. A fixed attenuator on each channel will do that and you are good to go. At least that is my approach. Yes I'd love an analog volume control downstream but I run balanced to the power amps so more work and cost .


Some people have tried running miniDSP into 500W amps running 100dB efficient horns. No expletive of course that will have gain issues, but for most of us we can get close.


All IMO of course. :)
 
@billshurv

As far as I understand, the 4x10HD is just : 2x8 kit, DIGI-FP, VOL-FP in a box.

The DSP chip in 2x8 kit is the SigmaDSP ADAU1445 whereas 2x4HD has SHARC ADSP21489. As you already mentioned, the SHARC processors is more powerful. For example, the 4x10HD can only do 6 parametric filters per channel whereas in 2x4HD has 10. Also you cannot do any linear phase finite impulse response (FIR) filtering with the SigmaDSP because that requires a convolution engine and lots of processing power.

2x4HD can stream audio from USB (has an XMOS chip), but 4x10HD cannot.

MiniDSP : Performance of 2x4 HD vs other models (4x10, 10x10 (1/1)

but yeah i use 2pcs of 2x4HD to get 4way, which might add extra work on 2 times setup on each channel

anyway I'm not moving totally to digital domain, I'm just stepping from FullRange Assisted Subwoofer & superTweeter to real multiway. Fullrange + ClassA amplifier is still my current favorite, simple yet sounds wonderful :)
 

billshurv

Member
Paid Member
2014-03-01 11:53 pm
Yeah it's not the most powerful box on the block, but for most of us has all the EQs you will need. The 4x10 can do 5 PEQs on each input and 5 on each output.If you do need more at least you know why you need them and can make an informed choice. I'm neither at an advanced enough stage in the designs not clever enough to be let lose on FIRs, but one day maybe :).


Biggest bugbear is only 4 presets. I'd like at least 10. In that respect Behringer have them beat, but its a fugly little thing and did not pass the approvals comittee :)
 
I use the Thomann T.Racks DSP mini (a pair) for a 4 way stereo system. The mid/high are tubes and compression drivers, midbass is class D and bass an older fanless PA amp. No issues at all. I have a volume in front of the DSPs and there is not much noise to speak of.

Tube and class D? someone might be triggered :D

but that is nice combination, i assume all drivers use PA drivers which are robust to any abuse
 

Rallyfinnen

Member
2017-01-22 10:18 am
I'm not sure what source you are using, but if you use a PC as source, you can do all the filtering in the PC, and use a multi channel sound card. That way you only have one conversion, digital to analog.
I use EQ APO for windows, and a ASUS Xonar U7mk2. Not the best you can get, but ok for the price, and gives me the possibility to run active 4-way stereo.
I guess you could use sound cards line in for analog sources too, but I have not tried that.
 
I'm not sure what source you are using, but if you use a PC as source, you can do all the filtering in the PC, and use a multi channel sound card. That way you only have one conversion, digital to analog.
I use EQ APO for windows, and a ASUS Xonar U7mk2. Not the best you can get, but ok for the price, and gives me the possibility to run active 4-way stereo.
I guess you could use sound cards line in for analog sources too, but I have not tried that.
my main source is cd player or media player for movie, connection via toslink or rca. i have laptop but not interested in usb streaming.

long time ago before i seriously jump into audio, i was pc user for gaming/movie/music. once i used onkyo 200ltd or creative extreme music. now i have small interest on pc for gaming again but it will cost a new big investment so pc+soundcard is not an option for me yet.
 
MiniDSP has an optional volume knob analog pot that acts as a 0-5v voltage source read by DSP’s extra ADC - the value of which is then applied to a digital volume inside the DSP. So you get a tactile physical knob and it works pretty good. Never had a kaboom situation.

Use the powerful Class D for subs. Use Class AB or A for mid and highs. Use your best amp for mids as that is where the soundstage info is. Gains on amps need to be approximately close (within 6dB or so) or else you waste dynamic range on DSP to match them. But it may be fine depending on rest of setup.
 
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pelanj

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Paid Member
2008-07-17 8:47 am
Hořovice
Tube and class D? someone might be triggered :D

but that is nice combination, i assume all drivers use PA drivers which are robust to any abuse

Yes, Beyma CP385/Nd in BC ME-20 HF, JBL2445J in 2380A clone for MF, Peavey Black Widow 15 in JBL4560 front horns and 2 x AC Acoustic 15" in Cervin Vega SL36 clones modified for 15" speaker per side. Shaking the house with 1 Watt of total amplifier power:) The future plan is all Class A low power amps, maybe except for the bass horns. Some info and pictures here: Three way horn system - but still with just two bass horns:)

Edit: The amps and DSPs can be seen in the last picture.
 
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My 2 cents

I use 2 Minidsp 2x4hd's to do eq and crossover duty for my version of Troel Graveson's 'The Loudspeaker'. So somewhat similar to what you are contemplating. The equipment chain is like this: cd player/tuner/computer to DIY Pass B1 preamp to Minidsp to amplifier. Volume control as at the B1.

When I used a mix of amplifiers with linear and switching power supplies, I had hum or ground loop problems. After messing around with grounds, polarity and isolating transformers, I substituted linear supply class d amps to solve that problem.

The other problem I had was noise (hiss), which I presume comes from the Minidsp. I used a fixed attenuator after the Minidsp, one for each channel to solve that.

Sounds great.

I have acquired the parts for an 8 channel because I think that will be the best solution from a noise perspective.