SFF but not PC - REVO's DIY HiFi Projects

[REVOCCASES]

once upon a time, when SFF PCs weren't even a thing, I was quite active in the PA and HiFi communities... back in the days I designed and built some pretty monstrous PA speakers and subs with 15" to 18" woofers powered by two 2000W amps that could easily entertain a crowd of 500+ people, clearly non-SFF and off topic...

anyhow, since I wanted to get some new desktop speakers for my SFF office rig I thought I'd dive back into it... but this time taking the SFF challenge - just in terms of HiFi!

below are some projects I've been working on - maybe with more to come ...

 

[REVOCCASES]

this is my first take on a SFF speaker design and while it isn't too difficult building some simple small speakers, the real challenge is making them sound "large" or in other words getting a good sounding deep bass fundament...

one trick how to get more bass (or a deeper bass) out of a small volume speaker enclosure is the so called Transmissionline design. The idea is to have channels inside the speakers and tune them in a way to get a nice deep bass out of a relatively small enclosure.

and this is how my take on that concept looks like:



the parts are CNCd out of 12 and 18mm MDF and then glued and screwed together...



after assembly and some rough painting:





as for the drivers I chose some budget components:

High/Mids: OmnesAudio BB 2.5 AL
Sub: Omnes Audio SW 5.01

As you might notice, each speaker has two pairs of speaker terminals. One for the High/Mid drivers and one for the sub. This allows me to use a Class-D Amp with integrated DSP to tune each speaker to my liking instead of using a common passive X-over.

Some examples for suitable DSP Amps I found:

WONDOM / SURE AUDIO JAB5
AXTON A542DSP
ISUDAR DA408

all these amps can act like an active X-over, equalizer, etc and can be configured via PC or smartphone APP... this makes it super easy to iron out some design flaws and eliminates passive x-over calculations and trial&error to find the right sound...

 

[GuilleAcoustic]

Oh nice, haven't seen transmission line cabinet in ages. The fullrangers are sealed/close ?.

Can't find the picture, but that kind of design looks super nice with plexi/resin side panels.

Not really transmission line, those are back loaded hornsn but simalar idea with transparent sides :

 

[REVOCCASES]

now the first set of speakers turned out really nice in terms of sound but they're still a little bit too big for my small desk.... so here comes the second build!

this time I wanted to try a passive radiator design - something that many "boomboxes" are using to get a nice and deep bass... but one passive radiator seemed not enough for my taste, so I added another subwoofer to the concept...

drivers used:

fullrange drivers: Dayton Audio DMA80-4
passive radiator: Dayton Audio DMA80-PR
subwoofer module: Tang Band T3-2190S



for my first try I CNCd the parts out of 12mm MDF which took about 2 hours



but I also tried some other materials... the gray composite material looks really nice...!



assembling the prototype:



painting...



now the original plan was to build the WONDOM JAB5 in one of the speakers and the PSU in the other one to have some true active desktop speakers ... but unfortunately I'm too stupid to program the DSP on the JAB5 using Sigma Studio ... so for now I've decided to have them run as passive speakers and using an external DSP Amp...



assembling the speakers, damping etc...



the "maintenance hatch" was originally meant to hold the JAB5 and PSU... but as I said earlier I'm just going passive until I figure out how to use Sigma Studio...



last but not least CNCd a faceplate / nameplate (originally where the pots / buttons should have been placed)



and here they are: REVOCCASES RCC SP2



next up: sound testing with the ISUDAR DA408 DSP AMP

 

[REVOCCASES]

Oh nice, haven't seen transmission line cabinet in ages. The fullrangers are sealed/close ?.

Can't find the picture, but that kind of design looks super nice with plexi/resin side panels.

Not really transmission line, those are back loaded hornsn but simalar idea with transparent sides :

Oh wow, those speakers look fantastic. It's TangBand fullrangers in there, right?

I was also thinking about using a back loaded horn with a fullrange driver at first but then got inspired by the Boenicke W5 with the sealed mid/high driver and sub on the side.

 

[GuilleAcoustic]

It's TangBand fullrangers in there, right?

Looks like it, but can't confirm. There are a few brand using phase plugs that looks like this one.

I was also thinking about using a back loaded horn with a fullrange driver at first but then got inspired by the Boenicke W5 with the sealed mid/high driver and sub on the side.

From my understanding, the best suited cabinet design depends on your speaker Qts:

Qts value	Description	Suitable for
0.2-0.4	very strong drive	horn speakers
0.3-0.5	strong drive	bass reflex speakers, horns
0.4-0.6	medium drive	closed cabinet speakers
0.5-0.7	weak drive	transmission line speakers, dipoles
> 0.7	very weak drive	dipoles, automotive: rear parcel-shelf

 

[Phuncz]

Very nice ! I have a set of Logitech Z-5500 speakers waiting for me to put the drivers in a custom enclosure

 

[REVOCCASES]

Very nice ! I have a set of Logitech Z-5500 speakers waiting for me to put the drivers in a custom enclosure

Cool, I had the Z-680 - unfortunately the controller gave up after two or three years

 

[msystems]

Incredible stuff. Did did you use some kind of volumetric calculations when making the channels/ports for the speakers or is it just experimenting with what sounds good?

 

[REVOCCASES]

Incredible stuff. Did did you use some kind of volumetric calculations when making the channels/ports for the speakers or is it just experimenting with what sounds good?

I only did some "rule of thumb" calculations for the TML speakers and the rest was trial & error. Because of the small size I had to make some compromises and you can clearly hear that if you run the speakers off a normal AMP. With a 4-channel DSP AMP however you're able to tune everything and making them sound really great. That's basically the same what manufactures of small Boomboxes / Active Speakers are doing to get a better sound out of a small enclosure.

Speaking of the Amp/DSP, the ISUDAR DA408 arrived and since it's usually meant for Car installation I've started to mod it a little bit...

first of all I added a small power switch because obviously I have no ACC/ignition signal at home to turn it on/off...



secondly I modified the cable harness...



using some sleeves and GX12 connectors that looks much better for home use... as for the power supply I am using a second hand 12V 6A brick that I shot on ebay for 3,- EUR...



all wired up...



I also ordered a small wired remote control for the DA408... btw, the AMP supports Bluetooth, Chinch, USB and even Optical inputs



the parameters such as x-over, EQ, phase, delay, etc can be configured "on the fly" via PC (USB) or Android APP (Bluetooth)... unfortunately the Android APP does not work very well...



but the PC software does a good job and it's really fun to play around with while fine tuning the sound of the speakers... It also allows to program 6 different presets to the Amp which then can be activated using the remote control... very nice!

 

[msystems]

That's seriously impressive and looks sweet