Phil Starr

Hi Rob, You don't need cross bracing for the cab to work and many commercial cabs don't trouble themselves with it. The point of cross bracing is that linking opposite panels stiffens them both. as pressure changes in the cabs it pushes or pulls the panels and at certain frequencies (dependant upon the size of the panels, stiffness and their mass) they will resonate. Since the panels push out at the same time the forces cancel so the movement is damped. Putting the brace dead central risks creating a node and simply doubling the frequency of the panel's resonance so dead centre isn't great. Even slightlyoff centre though and you are good. The biggest panels are the most resonant, as smaller is also stiffer. Usually bracing front to back is difficult in a small cab as the speaker is in the way. If you are limited to a single brace then side to side is a good compromise. The two braces in my photo were my best guess for damping. I dropped the top to bottom brace later as it wasn't achieving anything. I don't spend hours on bracing. My simple method is to feel for resonances with my finger tips whilst feeding sine waves from a signal generator., sweeping up and down the frequencies. Putting the brace(s) where they do most good. a single side to side brace worked well and the cab is really quite well behaved. I'm pretty much agnostic on wadding. It's a really complex issue with lot's of theories but little proof. It definitely changes things in the cab and resonances are reduced but it's really hard to say that there is a working predictive model. I'd say cover the rear panel with some decently heavy felt stuck to the back panel with contact adhesive. Staples alone always work loose IME. If you want to go further then you can treat opposite panels or even cover them all. If you go for the white polyester wadding then make sure it can't move around in the cab and keep it well away from the ports.

The dimensions at the start would work but I'd tune slightly lower for this driver Two drainpipe ports of 18cm each would be a better tuning and what I was using in the computer model above. You can get a slighly better response with bigger ports but the port is then longer than the cab is deep and would need to be removed, probably bottom venting. At anything below 200W you wouldn't have problems anyway. In the end I used this cab for quite a while with one of my bands and had no problems with wind noise from the ports at gigs despite playing with one of my loudest drummers (David you know who you are ). Like any ported cab using a highpass filter helps power handling and chuffing a lot as well as cleaning up your sound. It might be worth having a quick look at this thread. Although this is designed as a 10" cab with a tweeter/horn the basic cab is the same except for the front panel and a bit of extra bracing. There are proper drawings in the first post

As it happens I had the details with the Faital saved from a previous project. With 130W which is the typical mini-amp output into 8 ohms it looks like this. Ideally the Faital would be better in a bigger cab (better in terms of more bass and a flatter response) There's a 2db peak at 120Hz which is typical of many commercial cabs, but that's not awful; it will sound quite warm and bass heavy without eq . My original driver did much the same and so did the Beyma 12CMV2 It's really quite a good match. The biggest problem is that you need quite a big port for a small box to avoid turbulence in the port but if you limit it to 150W that shouldn't be a big issue

Just thought other people might like watching this. The auto translation is hilariously out in places but you can easily follow so I guess it is functional. The opinions may be surprising but evidence is given so it is genuine food for thought and for UK purchasers might point you in new directions. Who would feature in your top 12?

Those drivers you've used are pretty formidable Bill. Proper professional drivers and good ones at that. Stimulated by your designs I've been browsing the Celestion catalogue and they seem to have rationalised their cheaper offerings a little and to be moving upmarket, apart from their guitar speakers which has long been a speciality. I guess moving upmarket makes a lot of sense when you are manufacturing in a high cost environment like the UK or US.

I think the LFSys convention is that smaller dia speakers have shorter names. Spa is still free but once that is used there is nowhere to go

I can't help but think that you must be too loud. You don't need a sound level meter you can get free apps for your phone which will do a simple measurement. All you need to be able to do is to match the output of your drummer. Who may be too loud of course. At rehearsal you should be way below gig levels It's a problem with a lot of inexperienced bands, rehearsal is as often about getting out and making as much noise as possible rather than working on learning or improving new material. Bands playing flat out will damage your hearing. Measurements at Glastonbury showed Drummers experiencing 103db and most of the band 100db average levels. That's way above the safe levels where you would be wearing protective gear in an industrial site. You'll suffer permanent hearing damage in less than 15 mins at this level. Think about wearing in ears as soon as possible. They cut external noise by maybe 20db depending upon fit and when you get the mix right you'll hear everything better. It may be that your problem hearing yourself is that your hearing has been damaged at rehearsal. Hearing your self isn't just about volume, it is also about direction and frequency. Firsly make sure none of the guitar amps are pointing at you. They are very directional and should be pointing at the guitarists ears, usually they are pointed at the back of their legs or at some other band member who doesn't need that much guitar. Secondly point your own amp at your own ears. Speakers are very directional, like a torch beam so standing off axis is standing out of the beam. Secondly the frequencies you need most are the mids boost these. Most amps have artificial boost of the bass and treble to make them sound better at low volumes in the showroom. Cutting the bass also lets you use more volume as the bass is soaking up the power and moving the speakers into distortion. Cut the bass and treble. Mainly though get the others to turn down and the drummer to back off too if they are too loud. My guess is that none of you can hear yourselves well and each of you is edging your volume up to emerge from the overwhelming noise level. Basically you are all fighting a volume war. Our ears aren't designed to work at the volume of a Rumble at full volume and they don't hear well. Keep going and that will become permanent.

Have you considered insert leads which can split the signal at the stage mixer. Not possible with a lot of digital mixers but most large analogue stage mixers have an insert in every channel. How many channels do you need to split? Will it actually be 16 or is that just future proofing for something you'll use again? There are plenty of DI boxes that can split a signal and if you have multifx for instruments they may give you a stereo out. Depending upon impedences and signal levels you might even be able to split with Y leads. It's probably only worth chasing these options if you have some of this stuff anyway, I know I have all sorts of of s**t tucked away so I know I have three DI boxes that can split a signal plus a couplke of fx boxes for instrument splitting and you may have more than you think for use in an emergency. Have you talked to the PA people? They may be able to provide you with pre-fade signals from each channel or even (probably unlikely though) give you access to the monitor mixes if they are using X-series mixers. Since everybody just saves mixes nowadays it is less of a hazard for them than it used to be. I can imagine any sound engineer shuddering at the thought though Can you use Ultranet to connect two X series mixers? It can send 16 channels to a laptop but can it send it to another mixer? Behringer do the Behringer ULTRALINK MS8000 here which is £66 for 8 channels Amazon are listing a splitter box with wo snake tails for £250 but the Behringer looks a cheaper and tidier option to me.

Congratulations upon getting this commision Bill I'm sure it will be a useful resource for many people

It'll take me a while to model the response of some of the drivers available today but this looks very do-able. The thickness of the ply isn't going to add a lot to the weight, just remember it's the internal dimensions you need to worry about so you'll need to allow for that when you cut the panels. For example going from 12mm ply to 18mm would make the cab wider by 6mm each side and it would need to be 12mm wider overall. Thicher panels means less pracing so you can shave a bit there. Think about the 4ohm driver a little more. You will gain at best 2db which is just noticeable and for acoustic gigs you won't need that much, I use a BC110T for open mics and it is really overkill. I do a lot now with my 6" design and we've recently put up a design for an 8 which works well, all this with a Warwick Gnome 130W into 8ohm. This cab is around the size of your Monza and roughly the same weight you could go smaller IMO. The 8" cab uses the same 'easy build' construction so is effectively the same cab with smaller panels.

I'll be coming along to repeat the blind cab shootout from the South West Bass Bash, and to meet up with quite a few of you who I've chatted with over the years. I see a few faces from the SW will be there too, no giving the game away #1 - Paul @NancyJohnson #2 - Paul #2 @prowla #3 - Martin @Merton #4 - Matt @Wombat #5 - Andy @Wolverinebass #6 - Stevie @stevie #7 - Lozz @Lozz196 #8 - Matt @neepheid #9 - @bassace97 #10 - Robert @bass_dinger #11 - Christopher @chyc #12 - jaco @Geek99 ** #13 - Alan @WalMan #14 - Trevor @TrevorR #15 - John @jonno1981 #16 - Gary @cetera #17 - @MacDaddy #18 - Steve @Stingray5 #19 - Russ @Russ #20 - Happy Jack @Happy Jack #21 - Silvia Bluejay @Silvia Bluejay #22 - Mike @mikelawrencecalleja #23 - @admiralchew #24 - Martin @police squad #25 - @Sean #26 - @silverfoxnik #27 - @SimonK #28 - @hen barn #29 - Andy W @basexperience #30 - @stevie #31 - @Mudpup #32 - @BillyBass #33 - Kebabkid #34 - Phil Starr +potentially @Shockwave, @Wombat & @Mike Brooks

Spot on

I probably didn't explain very well. I use a shelving response rather than the more usual bass tone control which rolls off the bass increasingly as the frequency drops. A shelving response acts like a volume control for bass cutting it all by a set amount. Like this but I only cut by a couple of db not 6db as in this example. I chose the 160 point as that was what was on my mixer at the end of the last gig. I ws surprised it was so high myself but it sounded good on the night. It wouldn't suit every bass or every bassist and Al makes a good point about weight. I suppose what I wanted to say ws don't be scared of equalising around a higher frequency and if you have a shelving response available on your mixer then explore using it. I find it quite a pleasing way of removing some of the boom whilst keeping a little deep bass and way better than using the conventional bass control on my active bass or the bass amp. You have to use your ears and of course we are all aiming for different sounds. Perhaps the other advice would be to make small changes and go back to a flat response from time to time whilst adjusting so you can be sure the changes are genuinley improvements. more here

Good Luck

Anybody listening to music in the 80's will remember the loudness control on their cheap hi-fi. The magic button that made our music come to life, they are still around often with exotic names like Psycho Acoustic boost. The loudness control worked because it exploited a couple of simple bits of human biology. The same bits of biology that make any bass amp or speaker with a mid scoop fly out of the sales room. It's the sound we all love practicing at home but which sounds s**t when we take it to a gig. So to understand it on the graph a couple of simple bits of physics and then some biology which will hopefully help people with their eq. So Physics first: sound pressure levels are measured in decibels and are a measure of the sound's energy, how much the air is moving, kind of. It's what is measured by a sound meter and we use it as a measure of sound volume but it isn't reall a measure of how loud something is. Loudness is measured in Phons. The Phons are only the same as the decibels at one frequency 1,000Hz which is right in the middle of the mid range, sort of. Sounds at low frequencies or very high frequencies just aren't as loud for us as at 1,000Hz but at 3,000Hz they sound even louder. If you want hou can play with this online Here To understand the graph look at the 80Phon line; at 1000Hz it is 80db. Run left to 100Hz and it is 90db. To sound the same volume you need an extra 10db which is 10x the power from your amp/speaker run up to 7kHz and it is again 90db to get the same volume. The graph kind of shows how you would have to set the graphic to get the same perceived volume at 80 phons. As a bassist though the thing to notice is that the settings at low sound levels are different to those at the highest levels. At the quietest you'd need 70db of boost to hear any 20Hz sound at all. At 100phon you'd hear it easily and only need 30db boost for it to be as loud as it is at 100hz. This is where biology comes in, our ears and brain work together to give the most useful sounds. it's a really clever and subtle system of signal enhancement with genuine survival value. There are lots of quiet bass sounds our body makes, the rumbling of our gut and the grinding of our bones as we move. Imagine moving around the savannah's with the sound of our last meal drowning out the sound of something that want's us to be it's next meal The sounds we hear best are the dip in the curve 2-5kHz which is vital for understanding speech and screams and cries. Loud bass we need, it means something exciting and dangerous is about to happen, a large animal, falling rocks or something powerful and dangerous. The reason we like a mid scoop becomes apparent. by having the mids lower it sounds like the bass and treble are louder and you get the illusion of your bass coming from a much louder amp. When you turn the amp up to gig volumes you need a lot less boost to bass and treble to get the sound you crave. Loud bass is exciting, an adrenaline rush. So finally we get to bass guitar. Average gig levels are around 100db (as measured on-stage at Glastonbury a few years ago). 80phon is more like pretty loud music in a domestic setting and for sake of argument I'll say close to practice levels. From the graph you'd need around 15db boost to get 100phon at 50Hz and at 80phon you'd need 20db of boost for the same effect. That's 5db difference in the bass between gig and practice levels compared to the mids. So to take your carefully set up tone for the gig you need to turn your bass down 5db at 50hz or the mids up by the same amount to maintain your tone. Given that the mid scoop is often around 5-6db you've pretty much always got to lose it before you play at gig levels. This isn't the only thing you have to contend with at gigs, room acoustics and the other band members come into the equation too but you have to expect to re-eq when you turn up the volume for a gig to balance your bass and midrange. You'd have to do it for the highs as well except that there is very little hf coming out of your pickups. Cymbals through a powerful PA though......definitely the wrong sort of adrenaline!