DSP from scratch, Android tablet + Edifier MR4's first?

[Jolly Joker]

Hi!

I've recently rearranged some furniture and now have my living room without computer and sound system. I've been planning to build a cheap-ish system with DSP, using REW to get measurements, add some acoustic treatment, fiddle with placement of speakers, subwoofers etc.

This would be for music only, AFAIK nothing lower than 40 hz. I want a separate source for running Tidal, normally/constantly plugged in so I don't have to worry about if it's charged, my wifi is saturated by torrents, down for whatever reason, Bluetooth audio codec degrading quality etc etc. My inexperience may show in these; not sure everything really is relevant.

My "end game" system would possibly be a pair of Genelec 8030's plus two or more subwoofers. My thought for getting started is buying a cheap Android tablet with a 3.5mm output plus a pair of Edifier MR4's and a cheap used subwoofer, fiddling with measurements and REW to learn more before spending much. What can I do with a DSP Android app and how can I handle getting the signal to the subwoofer?

Is this even a reasonable plan? Am I overlooking something?

 

[somebodyelse]

For the sub you should probably look at cheaper studio-style subs. They take the full range signal from your source and provide a high pass filtered output to go to your monitor speakers, often with an adjustable crossover frequency.
https://www.thomann.de/gb/subwoofer.html?oa=pra&gk=STMOSW&cme=false&filter=true

UAPP seems a popular option for Android, but see the EQ software thread for other options. It might be worth looking through some of the CamillaDSP threads to see what can be done with a Pi or old PC too. https://www.audiosciencereview.com/forum/index.php?threads/rpi4-camilladsp-tutorial.29656/ is a good one.

 

[Jolly Joker]

Follow-up: Should I use an external USB DAC? Will a cheap tablet give horrible sound from the headphone output?

 

[somebodyelse]

Can't say without testing. As the Apple dongle shows, they don't need to be expensive to be good.

 

[ozzy9832001]

I think there is some merit to this approach from a learning standpoint, but there are some obvious issues you may run into later on when you decide to move on from the edifiers.

The treatments you place may work for one set of speakers, but not for another, as their dispersion patterns are likely be different.

If you're going to use more than 1 sub, I'd recommend going with that option from the beginning. Configuring multiple subs is more difficult than just where to place it and it can easily go south and cause more harm than good.

What you will learn is how the room responds to sound and how to read and understand the data.

 

[Jolly Joker]

I suspect I'll have to deal with upgrading my speakers at some point no matter what. I'll have to keep in mind I may have to (at least) move any acoustic plates.

Thanks for the tip with multiple subs. Getting more than one shouldn't be much of an issue.

 

[Keith_W]

If I understand you correctly, you want to use a wired output from your Android tablet into your amp, and you want your Android tablet to perform DSP. You want to avoid wi-fi output because of wi-fi issues where you live.

This is what you need to make your plan work:

1. Software for filter generation. You want the output to be in standard .WAV format. You can take your pick among the many free or paid options: REW/RePhase, Audiolense, Acourate, Focus Fidelity, Dirac Live. You will need a PC running Windows to generate the filters. You can also use a Mac, but software options are more limited (e.g. no Audiolense or Acourate). I assume you already own a computer of some kind.

2. Software on your Android tablet with a convolver. What this does is to convolve (i.e. mix) the .WAV filter with the audio stream. This is a bit of a rarity, I did a google search and found this app. I can not vouch for whether it works because I have not tried it. I note that several essential features seem to be missing from the webpage - e.g. I don't know if it has the ability to capture output from the Tidal app. I don't know if it has multichannel support (essential if you want to add a sub, see below). Having an app similar to this is an absolute necessity, without it there is no way to use your Android tablet to perform DRC, and you would be stuck using PEQ's instead. In comparison, PEQ's can "sort of" be used to correct some room issues, but they are far from precision instruments and are very limited. The UAPP app mentioned above does not have a built-in convolver. You can use it to capture streaming from Tidal, but the output needs to be sent to a convolver.

3. If you want to add a subwoofer, it needs to have its own DAC channel. It is difficult to control the subwoofer independently without this, and you won't be able to cross it over to the main speakers using your DSP software. This means purchase of a multichannel DAC or interface. I recommend RME or Motu. You may be able to use something cheaper like a Focusrite, but again - can't vouch for it, haven't tried it. The limitation is whether your Android tablet will recognize the DAC as a multichannel device, and whether the DAC has USB inputs.

My suggestion is to forget doing this on an Android tablet, unless you like pain. There are too many unknowns and there may be hidden software "gotchas" that we haven't anticipated. Just because hardware exists, does not mean that software will support it. Striking out into the unknown is for people with a lot of money to waste on potential dead ends and knowledge of what they are doing. It is not for budget limited people who have never DSP'ed before.

I think it makes more sense using your Android tablet for playback only, and sending the output to a MiniDSP or a purpose built computer or a Raspberry Pi. I don't like MiniDSP either, it has its own limitations and questionable design choices, but it is the cheapest and simplest solution to your problem. If you choose to use a purpose built computer, or repurpose an old PC, there are software issues to be aware of - the main one is audio routing and getting it to accept an external digital audio input. It is possible (I got it to work), but it isn't easy.

 

[Jolly Joker]

Thanks for the warning. Tablet + MiniDSP seems like an easy solution but I guess I'll have to look through how a Hifiberry works. Just getting a used laptop would probably be easiest but I kinda just want a touchscreen without anything that looks like a computer if that makes sense.