TOPIC:

i am planning a complete diy speaker build, stereo subwoofers and two main speakers, MTM 2 way design, thinking 3 channels per side for the mains speakers since i dont like to parallel my two 7ohm woofers(could not get 16ohm drivers). 
my problem is figuring out how to do the digital crossover and dsp, i own the SHD Studio, but it only has 2 channels, currently use it for volume and general peq and crossover between main speakers and subwoofer.  as i think i will be using it in the new diy system. 

Is there a problem with the shd studio peq and a nanodigi doing dsp at the same time?  the studio will then be only doing peq as room correction and the nanodigi as 2 way crossover.

Or i could use the studio digital outputs to a 3 way plate amp like the hypex fusionamp 123. any conflict or degradations from all the dsp in the chain?

Lets me know if got this all wrong and there is a better solution.

 

I got SHD and I use it to split between power amps + main speakers and subwoofer. I'm right now building new speakers with Hypex plate amps and I'm going to use SHD digital out to let the signal be digital as far as possible. That way there is going to be less noise compared to additional analog steps.

You can do DSP to signal in SHD (Studio) and even volume control before additional DSP in plate amp. The digital signal has so high dynamic range that it should be able to handle this kind of signal chain with ease

I've ordered my hardware, but I had track them down from 4 different suppliers, so completing my project is still going to take 2-3 weeks. I'll report here when it's complete to confirm pros or cons of this connection.

thanks Jukka and keep us updated when you know more.
I am a bit over my head here, i am trying to avoid plate amp for reliability and flexibility. but sometimes i just want a simple solution instead of 3 dac's and 3 power amps.
If i got with plate amps then i do not want to build them into my speakers, but then there is a mess of wires i have to find a solution for.  
I already got 2 power amps and 2 dac's, do not know if it makes for some issues since they are all different types. 
Not to mention what quality is the built in dac's in the plate amps.

I've read from other forums that Hypex FusionAmp plates are very good performance wise and their reliability is good. One local reseller said they haven't had any returns in years.

One good alternative is to make separated box for each plate amp, which you can place next to/under/on top of/screw on the outside back of speaker. Here is one that is built to separated aluminium cases.

If you put a grand on the plates and find them good, you should consider keeping them in case you change speakers and then it helps if they are easily detachable. But selling active speakers without the plate can be difficult, unless others do the same 🙂

reliability seems to be good, especially if you have separate chamber for them on the back of speaker, but then there are some designs i make that do not have room for that. 
building a wood frame for them to stand on separate from the speaker is another option that increases reliability.  or a nice metal box like then one you linked. 
i am still worried about hiss noise from plate amps, never heard a silent speaker yet. and all the active subwoofers i had over the years have failed or had issues. 

selling these things seems like a problem, and who would trust me to do great crossover design.....  maybe just sell them as drivers with box, no crossover. 

FusionAmps are not air tight, they got ventilation holes, that is mentioned in the manual. So if they shared air space with say woofers, the small holes would act as ports or resistance holes, which would cause noise, ruin the speaker tuning and directivity to a certain degree. The effect is small, but I've read experiences where it is clearly audible. So definitely separated box or sealed compartment inside speaker box. You can also add larger air vents so good air flow is ensured.

One reason for hiss in active speakers can be that tweeter is directly connected to amplifier without passive attenuation. Tweeters are usually much more sensitive than woofers and sensitivity of a woofer is usually traded for bass extension, so in passive speakers there is much attenuation to tweeters, which brings hiss down. Things to try, 1. twist your speaker leads from amps to drivers and 2. add resistors to attenuate the tweeter. Both methods are known to reduce hiss. I'll try without any attenuation first and report back if I decide to go for passive resistors.

my designs are sealed, and filled with stuffing, so definitely no place for a plate amp. i was also thinking as you said, making a separate compartment on the back with extra openings for airflow.  the more cooling the longer they last and possibly more power you can use before issues.  

i hear your thoughts on the tweeter attenuation, hope this is not the only solution because its a step back from my goals.
that will also mean that the same hiss issue will show up in my power amp setup and not only a plate amp issue.
luckily this is easily testable, i can hook up my tweeter to my power amps and listen. just a few weeks delivery time.....

Sorry for the wait, I just today finished building one of the speakers, but the other one is missing the plate amp. The AKM component crisis is taking its toll. Nevertheless I had simulated responses and dsp filters while waiting, so I just loaded up what I had and it went as expected. I got nice output, but I still need to do fine tuning with a microphone.

I listened to a few songs and tried some settings with SHD up front as preamp (digital volume control) --> coax spdif to Hypex FusionAmp. I used 16 Ohm tweeter (inherently quieter than less-Ohm versions) and it's as clean as anything I've listened to this day and I experienced no audible hiss, noise or other digital anomaly from low volume or high volume in the preamp. I still need to get my final bass EQ right before I can definitively say, because the tweeter line has about -22 dB digital gain compared to woofer due to sensitivity missmatch and EQing. I doubt that there is going to any problems, because 24 dB is just 4 bits, and spdif has 24 bit capability, that's 144 dB of dynamic range and even the best dacs struggle to resolve 20 bits before noise and distortion takes over. I don't need 122 dB in my living room, probably not even a hundred  Power on/off pop is the just a very faint *click*, nothing to worry about, I did not install tweeter protection cap (yet).

Once I get the dsp curves right and apply Dirac from SHD I expect it to work wonders as it did with my previous speakers! I know MiniDSP has similar products, but these Hypex plates just have the performance and all the supplementary features one would ever need for an active speaker system as such. I highly recommend Hypex plates with an SHD or SHD Studio up front!

thanks for commenting on the progress and testing  
interesting speaker you made, is horn loaded tweeters more prone to hiss?
and i have more hiss lately, since its a rats nest of wires here while i build speakers and get new parts. maybe that is a good reason to get a plate amps like the fusion amps, so i can have less wires and things that might pick up hiss along the way.  
i checked on someone that sells DIY icepower amps complete in chassis, about 900 dollar for 6 channels, and i still need more dac's and a minidsp nanodigi...... maybe my first step into active speaker design should be a plate amp after all. 
Question: can i store my crossover settings and stuff  on the fusionamp or somewhere else, so i can use the amp on many speakers and have many presets?
Picture is my progress on my little MTM's hanging to dry.
 

@Jukka

Superb setup here with your Hypex plate amp + SHD! 
Keep sharing pics and your progress.  

DevTeam

Continued

I updated some filters and run a test to measure hiss. The measured setup was SHD digitally FusionAmp (as was previously), no analog components between NC100HF (high frequence amp of the plate) and NSD1095N (tweeter) other than wire, mounted on XT1086 horn (damped to fight ringing), UMIK-1 microphone (using calibration file) placed inside horns mouth, half way up to tweeter. 


Take a look at the attachments. First measurement was the background noise of my room with the Hypex powered off by the hard switch. That noise consists of some home AC, computer fans and a ticking clock, otherwise it was very quiet both indoors and outside. Second measurement was Hypex powered on and playing silence. Playing silence and just idling made no difference to the measurement, that was simply to ensure it wasn't self-muted. I played some music in between to ensure that the speaker is operational. Finally a graph with both overlaid. The spikes are the same, only the noise floor changes. Actually the background noise might have more spikes due to random computer fan rev up.

You can easily see that there is some hiss in the tweeter. When I'm in front of the speaker ear in the mouth of the horn, I can easily hear the hiss (when it wasn't raining). It remains to be seen if this hiss will need analog attenuation, I'm doubtful that I need any at this point. Some people are more sensitive to it and using speakers nearfield may require analog resistors to rid of it.

The further I get with tweaking the DSP, the better the result is getting!

eiv wrote:

thanks for commenting on the progress and testing  
interesting speaker you made, is horn loaded tweeters more prone to hiss?
and i have more hiss lately, since its a rats nest of wires here while i build speakers and get new parts. maybe that is a good reason to get a plate amps like the fusion amps, so i can have less wires and things that might pick up hiss along the way.  
i checked on someone that sells DIY icepower amps complete in chassis, about 900 dollar for 6 channels, and i still need more dac's and a minidsp nanodigi...... maybe my first step into active speaker design should be a plate amp after all. 
Question: can i store my crossover settings and stuff  on the fusionamp or somewhere else, so i can use the amp on many speakers and have many presets?
Picture is my progress on my little MTM's hanging to dry.

Horns improve on sensitivity, so any hiss that comes out of the tweeter is also louder.
FusionAmp has 3 presets, which you can select with control app or button on the plate. Not sure if the optional remote allows choosing preset. I now have DSP presets in plateamps and in SHD. For "every day" preset switching I use the SHD, because those are easier to switch, easier to modify for all channel at the same time and are tuned for different occasions, like with/out subwoofers or testing Dirac effects. The presets in plate is just a plus, because plate DSP should be used to tune the speaker and preamp DSP should be used to tune for the room etc.

There are multiple problems with all separates, which you need to think through before going that route, such as in which point is your volume control and does it affect all channel equally. You will want that with a display and remote control ability. And do you have a preamp that can take in all your sources and apply the same DSP on them. I too was looking at different (commercial and DIY) solutions until I gave up and took the easy way: bought MiniDSP SHD and a plate amp to match. One of my requirements was balanced (XLR) for analog interconnects, so not an easy thing to find. If you can manage all that and fancy 10 power switches before sound comes out, those Icepower amps are good deal for sure. I had that tech on my short list, but ease of use weighted more.

PS. Nice job with the cabinets, MTM is my favorite configuration for the looks!  I was tempted to make these 10 inchers MTM, but luckily reason won 

This is where I'm currently at: 
Measured with UMIK-1, 1 meter distance, indoors. Speaker is high-passed at 60 Hz, the peak below it is a room mode. Just ignore the large peaks and valleys as that's expected under these circumstances. Near-field measurement of the woofer is ruler-flat. I have not yet tried high SPL output from this speaker, but from what I have seen this far I can say there is no drawback in using digital volume control up-stream when DSP devices are digitally linked.

I was successfully able to time-align the speaker elements with UMIK-1 by using this miniDSP guide . The crossover in above picture is 1600 Hz Linkwitz-Riley 24 db/oct. If there was timing issues, it would display as deep V-shaped null at crossover frequency. I had those before time-aligning.
 

PS. One thing worth of a note. When I was measuring individual drivers for time-alignment, my initial setup was to measure L channel and use R for reference and as one would expect, had measuring mic in front of left speaker and right speaker was standing where it's supposed to be in normal listening conditions, 2 meters away. This resulted in wild timing inaccuracies, the results varied greatly almost on each of 6 measurements that I made for one driver. I thought that maybe this is what everyone has been warning me about when using usb-mics for measuring time-domain. But then I had an idea! 💡 I moved the the speaker-to-measure next to the timing reference speaker, so that both speakers were close to the measurement microphone. I began to immediately get consistent timing results! My guess is that measuring in a normal living room and using the other speaker for timing reference resulted in reference signal to echo too much for REW to get a clear reading. When both speakers are close to the mic, it can pick the reference signal much louder and give REW a fair chance of interpreting it. This problem would not manifest in an electrical loopback timing reference. If this is true and a major (sub)cause for usb-mic timing irregularities, it should be noted in the previously linked miniDSP article, that moving speaker-to-measure next to speaker-for-reference can give more consistent timing data.

i see you are having fun Jukka  
i just finished my speakers(should show up in attachments). and now i can do basic testing before i order fusionamps(out of stock everywhere and minidsp plate amp is not present in my country). 
my SB Acoustics SB29RDNC-C000-4 Neo Magnet Ring Dome Tweeters do have hiss and hums on all the poweramps and intergrated amps i have at home, normal speakers with internal crossovers are dead silent. this is going to be a problem i need to solve. 
also my fullrange Scan-Speak 10F/8424G00 also show  this issue.

To be clear, i keep my mindsp shd studio as volume control and room correction, fusionamp set up once for crossover, then i need the fusionamp to have some presets in storage for when i make more speakers. maybe i can export them as a file to my pc, then i can have unlimited presets.
the presets on my shd studio is great, and saved with full name on my pc, but presets cant be named so its a bit scary now when i have a tweeter on a preset.........
If i wanted a no plate amp approach, it should be as easy as adding a nanodigi as crossover unit. the shd studio does volume, then getting 3 dac's and poweramps. sound easy but it gets complicated if i dont have same types of dacs and amps. then comes the wiring and more boxes and opportunity for hiss and ground loops.     

im also dreading the time alignment, been trying to read up and learn it. nice to see someone trying things out and showing solutions to problems im certainly are going to face.

 

Thanks for the suggestion.