In a previous project video, I designed and built this 3-Way loudspeaker with really high quality drivers from Punktkilde and a Fountek Ribbon tweeter. I offered build plans for it, and it has proven to be rather popular. However, I discontinued the build plans after a short while, since the Punktkilde drivers just was not that easy to get hold of anymore.
So, to not disappoint anyone any longer, I am now rebuilding this project with drivers that are much easier to obtain, and in my opinion, much better value for money.
I have BUILD PLANS available for these here: https://soundblab.net/build-plans/
Finding drivers that could essentially just drop into the existing enclosure volumes proved to be not that difficult. After some enclosure modelling, I ended up with drivers by SB Acoustics. The woofers are from their PFC range, in the form of a 4inch midrange driver, and an 8inch woofer. These drivers have a reinforced plastic frame, but be assured that they still look the part and sound fantastic for the price.The tweeter is a 29mm fabric dome with an aluminium faceplate.
From this drawing, we can see that the enclosure is exactly the same, with only the front baffle being different due to slight variations in driver diameters. This time, I opted to drop the solid wood frame around the baffle, and go for a simpler look.
We still have the midrange enclosure with the stepped inside to help counter standing waves, and the slot port at the back of the enclosure. Two internal braces stiffens the enclosure further to counter panel resonances or vibrations that can colour the sound.
Of course, with the launch of this rebuild, I will have updated build plans available on my web-shop at here.
Starting with the new baffle panel, I can mark out the positions of the drivers and drill pilot holes for the router circle cutting jig. I use a downcut spiral bit in the router, that results in a very clean cut.
I don’t cut all the way through, but leave a little bit at the bottom of the cut, which allows me to punch out the circle and clean it up with a file and sandpaper afterwards.
To allow the midrange and woofer drivers to breath a bit better inside the enclosures and help avoid reflections onto the back of the speaker cone, I use a 45 degree bevel router bit to cut a bevel on the inside of the driver openings.
The tweeter has terminals that go beyond the diameter of the cutout, and a router with straight cutting bit is used to carve these openings out carefully, after marking where they should go.
So, initially I opted again top finish the MDF baffle with a dark black Sumi Ink. However, this meant I was unable to seal the MDF edges before applying the ink, and that was just not the ideal look I was going for.
Instead, I opted to rather seal the edges with a sanding sealer, before applying a spray-can undercoat, and finishing with matt black spray-can top coat, and then a few coats of matt clear coat.
Before attaching the baffle, I ran a bevel router bit along the front edge of the enclosure to create a subtle chamfer. This small detail adds a clean visual break where the baffle meets the enclosure.
To accentuate the bevel, I darkened the edge with a black felt-tip marker. This creates a shadow line that blends the enclosure into the baffle, giving it a more refined look.
With the detail complete, the baffle can now be glued in place and clamped firmly until the adhesive fully cures.
—
So, towards the end of the project I have come across a problem.
After fitting the temporary crossover for initial testing, I noticed so very bad ringing in the SB Acoustics tweeter around the 5, 6 and 7kHz range. When looking at the CSD or waterfall plot, I could see the long decay time in this region, and it was definitely causing much distortion and ear fatigue. Looking at the Waterfall plot of the raw frequency response, I do not see the same decay. So, it is a very strange occurrence that must have something to do with the crossover and driver combination. I also could not find any issue with any of the crossover components.
This put me back a bit, and I was forced to source an alternative tweeter that would hopefully integrate without these issues. This led me to the SEAS 27TFFC. The faceplate is the same diameter and the mounting holes also the same, so it could just drop in. However, I had to re-measure the drivers and redesign the crossover, which is now luckily a bit simpler and uses a few less parts, and I am happy to say that this solved the problem and I did not experience the same issue as with the SB Acoustics tweeter.
As usual with my crossovers, I mount all the parts on a 3 or 6mm MDF board with cable ties, and then solder the leads together point to point. Some leads might be too short, and then a short length of speaker wire is used to extend the leads. I try and use the best quality and combination of parts that will also provide the best value for money in terms of performance, however any of the suggested parts can be swapped for higher quality if you chose to do so.
The final stretch of this project that has been much overdue is in site as I solder and mount the drivers in place. The crossover board is secured to the top of the port panel with some hot glue, and polyfill is stuffed into the cabinet to provide further damping.
Looking at the crossover circuit, we have a total of 10 parts, and note that the 8inch woofer is connected in reverse polarity.
The frequency response from 200 to 5kHz is looking fairly flat, but we do have a rise in the tweeter response that I decided not to tweak. Listening to the loudspeaker of-axis, pointing straight forward, I was happy that even wit this rising top-end, that it did not sound significantly harsh, but rather a bit more open and clear. The SEAS tweeter definitely does not sound harsh at all.
Also ,when looking at the directivity charts, we can see that the in-room response does flatten out the rising top-end. The mid-range on this loudspeaker is wonderful, and you could say ever so slightly forward sounding.
The directivity plot shows good off-axis response up to 45 to 60 degrees across the range.
Impedance is at 4 Ohm nominal, and dips for a brief moment below that around 1.7 or 1.8kHz. This will not be an issue for amplifiers rated for a 4 Ohm load.
The bass on this loudspeaker is powerful, and extends all the way down to 30Hz, however room loading will bring this down even further into the mid twenties.
So yeah — after all the effort and time that went into this update, I can honestly say it was 100% worth it.
These SB Acoustics drivers perform way beyond what you’d expect at their price point, and the SEAS tweeter integrates beautifully with them. The end result is a speaker that sounds big, powerful, and genuinely full-range — in my room I’m getting extension just shy of 20Hz, landing somewhere in the mid-20s depending on placement and the track.
And what really impressed me is how well they hold it together when you push them. Even at stupid loud volumes, the drivers stay controlled, and with complex tracks there’s no obvious strain or nasty distortion creeping in.
If I had to pick the standout though, it’s the midrange. Vocals come through smooth and natural, with that “effortless” quality that makes you want to keep playing one more track.
For a large baffle speaker, the staging is also surprisingly good — wide soundstage, extending beyond the cabinets, and pinpoint imaging when the recording is solid. On well-recorded tracks, they really do that thing where they just… disappear.
Now, like I mentioned earlier, the midrange can feel a touch forward, and there’s a slight rise in the tweeter response — but together it gives you this really airy, open vocal presentation. It’s not harsh, not overly bright… just clean and spacious. And overall it’s a very dynamic speaker — the kind you can listen to for long sessions without fatigue.
These are still sitting in my listening room right now… and honestly, I have a feeling they’re going to stay there for a while.
If you want to build a set, I genuinely don’t think you can go wrong if this type of speaker is your thing. Head over to soundblab.net and grab the build plans for yourself.
Drivers:
– SEAS 27TFFC Tweeters – (US) https://tinyurl.com/3r4vrzvh, (EU) https://tinyurl.com/4nxjnzv2
– SB Acoustics SB12PFCR25-08, 4” Mid-range – (US) https://tinyurl.com/yyb2snwb, (EU) https://tinyurl.com/22y5xvk7
– SB Acoustics SB20PFCR30-8, 8” Woofer – (US) https://tinyurl.com/5n8ejsnv, (EU) https://tinyurl.com/26txwera
