Page 1 of 16

DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 12:07
by Petebass
Warning, long post!

Last time I built a speaker cab I was told I didn’t do enough to outline the process in the thread. I’ll try to fix that in this thread, but the experimental nature of my next build might make it quite a heavy read so I’ll try to do my best to make is as “Pain-English” as possible.

I’m going to assume you haven’t followed the threads on Talkbass by zac2944 where he made his bass cabs out of materials other than wood. Here’s the link to his original 2x10 thread:-

….. It’s long but it contains all the detail of what he used to build the cab and how he built it. I was thoroughly impressed, as was practically everyone on TB. Such was his success he later built a couple of 1x12 cabs using the same process.

For those who don’t want to read the whole thread, here’s a brief summary. His 2x10 cab ended up weighing 11kg. That’s extremely light for a 2x10, lighter than anything on the market. He used a construction method known as “Composite Sandwich Construction” to build panels which are as stiff as plywood, but weigh considerably less than most plywoods. He did this because he felt that saving weight on neo drivers is definitely helpful, but with so much weight in the wood there was room for improvement.

So what is “Composite Sandwich Construction”. Flightsound cabs touched on it with their cabs, but zac2944 took it one further. “Composites” by definition are materials which are made up of components which individually are not very strong, but when combined are much stronger than the sum of their parts. Flightsound used a stiff Foam as a core, then put thin plywood on either side of that foam core. The end result was very strong and weighed considerably less than solid plywood. Zac’s method retained the stiff foam core, but replaced the thin plywood with layers of fiberglass (or Carbon Fiber for those who can afford it), all carefully engineered of course for maximum strength to weight ratio. And it worked!!!

He spent quite a bit of time in the thread addressing the issue of the tone of the cabinet given there is no wood. The wood in musical instruments is designed to resonate and will therefore always contribute to the tone of the instrument. The wood in speaker cabinets is not supposed to resonate. In theory a properly build cab should sound the same regardless of the material used provided the cabinet walls are not vibrating. If your cabinet walls are vibrating, you’ve stuffed up the cabinet basically. It’s a massive waste of acoustic power.

zac2944 managed to satisfy even the most cynical TB’ers that panel vibrations will not be an issue. He used detailed physics calculations, and I followed that up with extensive research of my own into composite sandwich construction. By all accounts his cab sounded great, and frequency response measurements compared perfectly to the predicted frequency response from the speaker design software.

However IMO zac2944 fell one step short of completely proving beyond doubt that his composite cab would have sounded exactly the same if it was made out of wood. To do that, he would have had to build an IDENTICAL cabinet out of plywood and done a series of A/B comparisons. And that my friends is exactly what I’m planning to do over the next few weeks.

I will first build a 1x12 cabinet from plywood as I have always done. This one will be different to my previous designs in that I’ll be aiming for a fuller, warmer tone (as opposed to my previous cabs which were designed more so to cut through the mix). Once I’m happy with the wooden cab, I will attempt to build an exact replica of that cab out using composite sandwich construction. And when I say exact replica, I mean it – same speaker, same tweeter, came internal volume and porting, same EVERYTHING except one will be wood and one won’t. That way any difference in tone can be attributed to one thing only – the absence of wood.

Once that’s done I’ll do some frequency response measurements to compare the two cabs, and will also probably get some of you to help do some blind listening tests as well. From that we can draw a conclusion!

I don’t expect to have any problems building the wooden cab, I’ve done it enough times now. I’ve never built a composite cab before and expect to have some dramas while on a pretty steep learning curve. I plan to document the process here, warts and all, and by the end of it I should:-

1/ Know for sure whether or not the cabinet wood contributes to the sound at all, and
2/ Have myself a killer rig which is MEGA lightweight consisting of two 1x12 cabs.

Should be fun. I hope you come along for the ride.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 12:11
by Aussie Mark
Sounds interesting, Pete! Looking forward to following this.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 12:31
by jamiesdad
interesting ... if it works i'm sure nigel will commission one from you

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 13:00
by thebman
Subscribed....can't wait to see and hear the A/B comparisons.
All the best with the learning curve. Your like the experimental test pilot for all those wanting to have a go.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 14:05
by mkat
Great stuff Pete and don't worry about the length of the content, the more info the better with this.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 15:16
by Vege-mity-mite
Wow, subscribed... ummm, how do you subscribe?

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 17:39
by Petersland
Me too Pete. Looking forward to it.
The more info and pics, the better.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 18:23
by Petebass
OK now that I’ve outlined what I plan to do, we can get started on specifics. Lets start by make some bold predictions on what I expect these cabs to weigh. I've done some detailed calculations to estimate weight but rather than go through them boring math, I'll talk you through the logic.

I first did some analysis of the final weight of zac2944 ‘s creations. His 2x10 weighs 11kg. Zac’s composite 2x10 is similar in size and uses very similar drivers to the Epifani UL210, itself a fine cabinet. The Epi weighs a claimed 17kg, 6kg more than Zac’s cab. That’s a pretty good illustration of how much weight is in the wood.

So how does this affect the planned weight of my two 1x12’s? Well I’ve already weighed the wood I plan to use for the cab and it came in at 10kg, but I’ve yet to trim it down so I’m guessing there will be 8kg of wood in the final cab. The 12” driver I’m using weighs 2.5kg. Add a couple of kg for hardware etc and I’m guessing my 1x12 will weigh 13kg. That’s in line with the Epi UL112 (another fine cab IMO) which weighs a claimed 33lbs (15kg).

The composite version of this cab will also have 4.5kg worth of driver + hardware, and I estimate 4.5kg of weight from the composite panels. So I’m guessing the 1x12 composite cab will come in at 9kg, a good 4kg lighter than the wood version and 6kg lighter than the Epi UL 112. For reference, I weighed my MTD Bass in my Hiscox hard case and it was 9kg. So we're talking about a 1x12 cab that weighs about the same as a bass in a can’t complain about that!

The math for bigger cabs is even more shockingly beautiful. In fact the bigger the cab, the more amazing the weight savings. Taking something like the Markbass 104HR at a claimed 25.4kg (Drivers 8.4kg drivers + 3kg Hardware etc + 14kg of wood). Using composites, a similar cab would be closer to 18kg (Drivers 8.4kg drivers + 3kg Hardware etc + 6.5kg). These are estimates only but it’s hard to argue with a 7.4kg saving on a 4x10 cab that’s already one of the lightest on the market! The only argument is “will it sound the same as wood?”. We’ll soon find out :)

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 19:55
by Skyblue977
With respect Pete but for a bloke whom has roadies isn't this project a bit mad scientist sort of stuff?
I guess thats what makes it so cool!

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 20:17
by Petebass
Skyblue977 wrote:With respect Pete but for a bloke whom has roadies isn't this project a bit mad scientist sort of stuff?
I guess thats what makes it so cool!
Trust me, the roadies will be going no-where near these cabs until I build something else to supersede them. As a general rule I keep the older cabs in the truck, the Number 2 rig if you will. The No 1 rig is usually newer, lighter, and is the one I use when I do gigs with bands other than JBJ, which means there's no roadies and I have to cart my own gear around.

Besides, roadies are great while you've got them but I won't have roadies forever.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 20:36
by maxgroover
Vege-mity-mite wrote:Wow, subscribed... ummm, how do you subscribe?
Scroll to the very bottom of the thread and you'll see a hyperlink 'Subscribe topic'. Click on that and you're done. You'll get emails notifying you of new posts to the thread.

Have subscribed Pete. You clever bastard. :) Looking forward to updates.

We should organise a GTG to put some pressure on Pete to finish the two cabs and show them off in person! :D

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 20:37
by dan54
this is the best thread ever!

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 20:42
by Nigel
jamiesdad wrote:interesting ... if it works i'm sure nigel will commission one from you
Oh the PM's that have already been exchanged! Yes, I'm very keen to see how Pete goes. I'm also one of the first in line to test these out. Best of luck Pete.

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 21:27
by Petebass
For the speaker design hobbyists, here’s a run down of the speaker cab design.

Each cab will be loaded with one Eminence Deltalite11 2512 which I purchased from my good friends at Bass People (thanks Joel). I actually bought 2 Eminence Basslite S2012 speakers as well – the Basslite 12” has very similar T/S specs to the Deltalite 12” and weighs 1.9kg (0.6kg lighter than the Deltalite). But it’s only 150W compared to 250W for the Deltalite, and 250w is IMO a minimum for a 1x12 cab. I plan to use the Basslites in a 300W, 2x12 cab later.

I started with SBB4 alignment as I always do because it offers the lowest tuning frequency and very rarely spits out a ridiculous cab size. It suggested for a cab of 100 liters tuned to 37Hz. That’s too big for a 1x12 IMO, and I’m not chasing flat response on this cab. So I trimmed the cab size down to 70 liters and tuned it to 55Hz. This created a nice 3dB hump at 80Hz which will go a long way towards adding that warmth and fullness I’m chasing on this cab. It’s a trick a lot of the commercial manufacturers use. We’re getting into the part of speaker design where science meets art, something the commercial manufacturers knows well but doesn’t seem to compute with many of the speaker designers on places like TB, but I digress. The -3dB point is 49Hz which is exactly what you’d expect for a pro-audio 1x12.

I’m trialing a new tweeter for this build. I’ve previously used a silk dome tweeter made by Peerless and I love that bloddy thing. It was smoother than most metal based tweeters, and therefore much less “spitty”, but it maintained a crispness unmatched by any commercial cab I’ve ever played. But they’ve discontinued it. So this time I’ll be trying my luck with a textile dome. If it’s comes in somewhere between the silk and metal tweets, I’ll be happy. This one is a Vifa BC25SC06-04. It’s not as efficient as the Peerless but like I said, this cab is not designed to cut through like the previous cabs so I’m hoping it’ll add clarity in the highs without negatively affecting the cabinet’s warmth and fullness. I’ll build a crossover at 3.5K, 4th order Bessel (24dB per octave slope).

Below is a mock up of the predicted frequency response. I made it by summing the bottom end projection from WinISD, the frequency plot from the Eminence website to show the mids, and frequency response plot for the vifa tweeter for the highs.


That hump at 2.5k is typical of neo drivers, their smaller magnets generating less inductance than speakers with traditional magnets. This is often the culprit when people say that Neo drivers don’t sound warm. I have a couple of tricks up my sleeve that should smooth that hump out, but I’ll wait till I hear the cab in action before I decide if it’s necessary to act on that. I may even use a toggle switch that lets you choose between leaving the 2.5k hump in or removing it, maybe label them “Warm” and “Warmer” :) But I’ll wait and see if it needs it.

That’s pretty much everything for the planning phase. It’s time to start building!

Re: DIY Speaker cab and experiment.

Posted: 02 Mar 2010, 21:31
by Aussie Mark
Pete, do you have a feel for the materials cost of the composite cab compared to the ply cab?