Speaker building all by yourself

Hahaha, I bet a well cross-braced pressboard box would give Harbeths run for their money.

After all, the pressed paper for woofer material is still very much relevant for woofers in 2020, a very stiff and strong material.

 

Some progress on the cardboard box speaker.

Drivers mounted prior to glue-up.


Close-up of the baffle with driver cutouts. We used threaded inserts-- I don't thin I'd do it again. The baffle and top are made of maple, Indian rosewood, bubinga, a double layer of black veneer, and one last ply of maple. The other sides, port, and braces are 3/4" baltic birch.


The scary part.


And with the clamps off.


Next up is felt, sanding/finishing (maybe a chamfer on the top?), measuring again, then a crossover.

 

Just curious- if you did not use threaded inserts next time - what would you use?

 

Wood screws!

The threaded inserts were a total pain to mount without damaging them (the brass is quite soft). It also makes chamfering the woofer cutout on a hardwood baffle a lot scarier-- if chamfer before using the inserts, you run a greater risk of splitting the wood. Do it the other way, and cross your fingers that the router bit doesn't hit one of the inserts.

I didn't have this much foresight, so ended up not chamfering the back. I don't think this will matter too much here because this particular woofer's spider is already fairly restrictive.

 

Note troels graveson always uses plywood which holds wood screws better than mdf.. so this advice is more for plywood speakers.

 

Troels has also mentioned he hates T-nuts. If you have issues with removing screws too many times, Troels says to just fill the holes in again with a mix of sawdust and glue.

Lately though he's been making a removable back board if you still need to access the inside.

 

I finally got my current drive amps running for my 2.5 speakers. Distortion and transient response plots here. Most of it can be inferred from the frequency response.




Nearfield, so only valid to maybe 600Hz, and in a very large (30L or so) sealed enclosure-- typically an enclosure of this size would be vented for these drivers. Both amps are are balanced and without global NFB. This means that the voltage amp has a non-zero output impedance, but also that it will not create distortion products from back emf interacting with a feedback network. I think it's a fairer comparison than the typical power op amp vs transconductance amp deal. The output devices are also biased to the same op point.

The important thing is that it does exactly what one would expect; the impedance response is superimposed on the frequency response under current drive.

Low frenquency normalized distortion is higher with current drive. This makes sense, because the excursion is significantly greater. In the passband, things are comparable. Voltage drive may have a slight edge. Things look better past 1k, but I would need to measure midfield to confirm that it's real. This may lend credibility to the back emf theory, but it's worth pointing out that this woofer has a fairly low inductance.

After eq, current drive wins, hands down. But it also extends nearly an octave lower.

 

I've been very interested in the SB Acoustic open baffle woofers they released. I just saw that Madisound has an OB kit based on them:

https://www.madisoundspeakerstore.c...udience-ob3-open-baffle-3-way-with-15-woofer/

compression horn + 6" mid + 15" woofer! Man I wish I could just build everything

 

Tempting as hell but the last thing I need is another set of speaker parts sitting around for years mocking me.

 

I think spwath's contribution should be mentioned here

https://www.superbestaudiofriends.org/index.php?threads/troels-gravesen-illumina-66-build-log.11071/

 

I'm rather curious about the design choices. All drivers have sensitivity in the upper 90s and yet system sensitivity is 85dB.

edit: actually there is a document explaining his design

https://www.madisoundspeakerstore.com/pdf/SB Audience OB3 Open Baffle Kit.pdf

Seems like he wanted everything to be flat to 50Hz. Increasing sensitivity would come at the expense of bass extension.

 

the crossovers cost more than the drivers.. wtf

 

I think you might have looked at the wrong thing. I see drivers for $770 and crossover for $580. Which is still a freaking ton of money for crossover components.

Schematic and values are published though so you could still try to assemble from whatever parts you want

 

May I muck up the thread with some questions? I have a kit sitting in a box waiting for me to find the time to build them. Outside of not having enough time, finishing has gotten me tied up. The boxes are MDF so I need to do something with them. What is the easiest way to make them look decent? My signficant other actually wants them black since most of the stuff in the entertainment center is black, but these are hopefully my forever speakers so I want the finish to not look like I just sprayed them with truck bed liner. She would be ok with a wood grain, but I have never veneered before. Any recommendations?

 

Yeah I would also like recommendations. My speakers are still unfinished MDF.

From my research though, there is no "easy" way to make them look good.

 

veneer seems like it takes less time than multiple painted finishes.. just need contact cement and an exacto knife

 

Veneer looks good and is more forgiving of the under surface ( relative to paint or vinyl wrap)

The key is to buy good veneer - you need to be able to smear contact on it and let it dry without warping it. Make sure you seal the MDF with thinned down wood glue or some other sealant.

After applying contact to both the veneer and the speaker - and letting it dry, then apply the veneer to the box using a hot dry iron to activate the glue to a good seal

says the expert who has done this all of once and cursed through every second of the process

end result



this was my first DIY speaker many , many moons ago

 

Easiest = Route the corners a bit, spray paint them black, brush shellac over the paint.

Veneering is not that difficult, just time consuming if you haven't done it before. An then you need to stain and \ or finish the veneer. Key to a 'forever finish' is to practice on scraps until get the look you want.

 

I know you said "no truck bed liner" but this stuff has less rubber/solids, so it's a bit less textured. plus, low VOC so you can paint the cabs indoors:

https://www.parts-express.com/ExoHy...ective-Speaker-Cabinet-Coating-Quart-260-2100

Looks pretty good based on pics on PE, imho.

 

Thanks @Cspirou for pointing me towards this thread.

Here's my first DIY Loudspeaker project, a 3 way called "Saisho".
Designed from scratch because... learning and tweaking is fun!



I can post more info / pictures if needed.