Phil Starr

Phase is a moderately complex idea, so for anyone not familiar. Speakers (anything making a noise actually) move backwards and forwards travelling fastest in the central position then slowing at the ends of travel before turning round and going back the the other extreme where they slow and return. That creates pressure waves in the air that radiate out into the room. At the back of the speaker the pressure wave is reversed and the air is pushed in the opposite direction. It is 180 degrees out and if you let it mix with the air at the front you get cancellation and no sound. Many other things can delay the sound including distance and the air can be any amount 'out of phase' or not at all so you can get anything from double the sound from an in-phase sound to complete cancellation (which is what sound cancelling headphones do) Any time delay in the sound leads to phase cancellation but the 'phase' is dependent upon the frequency of the sound. Higher frequencies go through more phase change than low frequency ones in the same time. In a ported speaker the mass of air in the port is bouncing on the air in the cab; it is resonating if it is in action and like a bass string it only does this at one frequency (sort of) The trick of the designer is to set this up so it does this just as the speaker is dropping off in its frequency response. Once the port starts vibrating it pushes back at the air inside and if you get it right the cone of the speaker stops moving and all the sound output is coming from the port. So at the tuning frequency you aren't going to get cancellation/phase issues. The speaker isn't making much sound at that frequency. Above that frequency the port output falls really rapidly so phase cancellation ceases to be an issue. Finally all this is happening at the very lowest frequencies the cab can realistically reproduce so the phase shift isn't great and frankly our ability to discriminate sound at those frequencies is really poor. Any issues would be swamped by room acoustics as the bass bounces off every hard surface (floors, ceilings and walls) and takes many differing routes to your ears, each far greater than the distance from rear port to the front of the speaker. That's why I don't think you can hear a difference and I'm completely with Bill on this one; if you want to sell a speaker put the port where people like to see it. People buy with their eyes. That's the simple picture (I'm sure the experts are wincing here at some of the generalisations but I'm trying to be clear)

I hope people building their first cabs at home aren't being put off having a go at building by this It's great to see a range of opinions though. You'll see different designers have differing opinions and the truth is many of us have 'go to' ideas we tend to repeat. The reality is that all speaker cab design is a matter of balancing differing concerns. In the case of port designs it is pretty much impossible to design a really compact high power cab with deep bass that won't have higher port velocities than you'd like. For high power, high excursion speakers you need a wider port to allow it to 'breathe'. Increasing port area for a particular tuning means the port needs to be longer and that both increases the volume of the port and takes it closer to the back of the cab. If you are aiming to have a compact cab then a port of several litres is obviously something to avoid. so you have to compromise. Equally if you have a small cab then the places to put a large port are limited, more compromise. Just look at the RCF PA cabs; generally recognised to be one of the best sounding units available at the moment. Every spare bit of space at the front is either port or speaker. This is just the port of course, there are other tweaks and compromises to be made: weight, portability, target response and so on. then there are practical considerations like the cost of production for commercial designs and the availability of parts for the home builder. If you buy a cab then you are stuck with the compromises chosen for you, if you self build you can add your own tweaks or accept the tried and tested designs so you have a bit more choice. You can see the difference in approach even in this cab. I designed the original box which had a 12" speaker and two smaller ports. That design choice was based upon having a lot of 68mm pipe to hand and the availability of a 68mm hole saw at a price home builders could afford. I check them but I'm not particularly concerned about port velocities as I rarely if ever find they are a problem with bass guitar. My design does chuff with test signals but has never made unpleasant noises with me at gigs (apart from my playing of course) even though it has a 12" driver with greater excursion and power handling. Stevie chose the most widely available and affordable ready made port and that won't exceed unacceptable port velocities under any conditions within the pass band. It's on the big side for a single 10 but it fits and it works. The tuning isn't an issue as that was done by measuring after the cab was built.

That's one of the reasons we use tube ports. It's a lot easier in the prototyping phase. Otherwise it's probably better to make the shelf undersized and add on rather than have to cut bits off. I prefer round ports anyway. The walls of any port are where there is resistance to air flow and where non-linear air flow starts to cut in. The way to have the least air in contact with the walls is to have a circular cross section. We also found that multiple small ports demonstrated earlier chuffing than a single large one. Not very scientific as it was a sample size of one but it was a very obvious effect. Having said that other considerations come in to play. I often use whatever port material I have to hand, either plastic plumbing pipes or cardboard tunes from carpet warehouses.. Some designers have used triangular ports in corners. They'll experience more turbulence but it's a really convenient place to put them and the triangular bracing of the panels will be significant. Stevie really doesn't like chuffing so uses large ports for preference. I don't mind high port velocities on the basis of the absence of much fundamental coming from the pickups. It's hard to say any particular design choice is the 'one' as all speaker design is a matter of weighing gains in one area against compromises elsewhere. We are really happy to go off topic, lots of people read the answers and learn stuff and it keeps us on our toes for the next design.

When I wrote that it was just clean , plugged straight into a high impedance input in the mixer with no EQ. The mixer is an RCF M18 so it has amp emulation built in but I wasn't using it. Today i was playing with my Zoom B1ON in the line and that sounded great too. I hope you love the C2

Well done, nice to see it is coming along.

where did you source the grille?

that looks great, I should have gone for the silver corners.

Hmm bathrooms are a good place for stinky poo

What we are trying to do is to introduce people to all sorts of ways of building cabs and encouraging them to experiment. At the same time we want to offer designs that will be satisfying to own and will work first time. We're also trying to give enough information that people can do their own adaptations. If somebody wanted to there is no reason not to build the 50l MK3 cab with the drivers and crossover Stevie designed but using the 'easy build' technique. Or you could build the cab we are discussing here with a circumference brace borrowed from the MK3, or indeed a rear port. If you keep the overall volume and the port dimensions the same you preserve the tuning so if you wanted a taller cab or one that matched your amp dimensions that's all possible. Everything we do on here is creative commons, we're happy for people to build the cabs for their own use or to build one for a friend so long as it is done on a not for profit basis. If anyone wants to put together a small run of CNC flat pack kits for BassChatters on a not for profit basis that's good too from my point of view. I'm not sure what the next project will be, I've got all sorts of plans but I need to clear some of my stinky poo out of the house to make some space. I'm also being reminded I have to fit a new bathroom

I've just spent the day playing through my RCF ART310s on poles they do just what you want, they sound like huge headphones. Nothing in the chain other than the mixer.

Back on track, thanks for this John, it's really useful to have an independent personal opinion. I have to say that this pretty much matches my own experience. I also rolled off the bass a tad and found the cab perfectly adequate for rehearsals. the basic sound is just a lovely open honest sound of the bass but I also added a little compression (and grit also). The band loved it. I'd also pretty much agree with the assessment of it's capabilities, 100+ would be beyond it as would anything outdoors. You'll find when you have two for PA it will sound a lot better than the single speaker. I do a lot of critical listening when testing speakers and listening in mono often shows up things you don't notice with a stereo pair and of course the imaging will do so much to the experience. This little speaker has given me a little doubt as to what I'm doing next. I've got the parts to build the 12" BC Mark3. I've been using bits and bobs of prototypes I've been taking to gigs for years and I wanted to have a go-to set up for important gigs. I've been using a couple of Beyma 12 based BC Mark1's for years. This BC 110T is so much better than it has a right to be and is so portable I'm now thinking of just having a second. Then I'll have two speakers I just won't touch for gigs and I can experiment freely with whatever else I have. For £125 and less than a days work it's tempting. Just a question of which one to build next.

Honestly I doubt that they do sound better, I can think of at least one good reason why they ought to sound worse but none which would make them sound better. There is no theoretical reason i know of that would suggest a difference and i doubt you'd measure any difference at a decent distance from the cab. You are then down to subjectivity/listening tests. The problem is proving a difference one way or the other. You'd need to build identical cabs with identical drivers and then carry out multiple double blind tests where neither the listener nor the operator knew which cab was which. The big problem is that our ears are connected to a big organic computer which processes the input from our ears and often functions to make us hear what we expect to hear. I've spent many hours doing listening tests when designing and building speakers and you'd be amazed how often you can fool yourself that you can hear something that isn't there or fail to spot something that is obvious. My wife assures me that i often fail to hear things which are important to her but rarely miss something important to me It isn't just our sight that is subject to illusions. To me ports on the back look wrong and I tend to avoid them even though I know there is no good reason to do this. The reality is that I've never actually listened to the same driver in a box identical except for the port placement. Maybe you just prefer some speakers to others and as not many have ports on the back it's just coincidence that you didn't like those as much as your favourite cabs So what could make it sound different but objectively worse? Firstly cutting a hole in the baffle weakens the part of the cab you have already weakened with the speaker cut out and the bit you need to be most rigid, you end up with a big heavy magnet fixed to a wobbly board. A weak baffle isn't good secondly the port itself has a series of resonances where the wavelength is a multiple of the port length. These are going to be more directional and could be audible.

If you don't mind building one of these would be ideal We've been looking at a lot of bass speakers and the crossovers are rarely done with a lot of care so that's probably what you are hearing. If you want to buy then it's probably best to skip bass amps most of which are 'voiced' in some way and go for a PA speaker. I use my RCF ART310's sometimes and they work well with bass up to quite a reasonable volume. Depends upon what your budget is of course.

Brilliant, I think this will be ideal for you.

Hi Bert, I would have thought it would be great for what you need. I designed it to cut the low bass and emphasize the upper bass/low mids. I think it would certainly do the Motown sounds quite well. However I'm not the words greatest tone freak or the best musician in the world (by quite a distance). I notice you are in Somerset so maybe you should come over and have a try sometime. I live just the other side of Chard

Before you start this think about what you are trying to achieve. Is this to repair a cab which seems to be damaged or a restoration of something you love? Maybe you want to upgrade it? The thing is that there is only one way of making this like new and that is replacing the original drivers. There are probably a lot of substitutes that will work perfectly well in your cab but they will all sound different from the original drivers. For some it might ba a subtle difference and for others it could be dramatically different. WinISD is about the bass response and it is quite possible to get something close to the response you currently have but the response of speakers at the top end varies a lot and the computer modelling wont help there. This cab has a tweeter and crossover and that complicates the matching process. The moment you change the speakers you don't have an Aggy you have a box with different speakers and a different sound that looks like an Aggy. It could sound better or worse of course. The first thing is to say is that speakers don't usually rattle when they are ****ed. Rattle sounds like something is loose in the cab. Maybe the speakers aren't properly tightened down any more or a joint has broken which could be re-glued. Maybe a lead has come loose and is rattling against the speaker? We can talk you through trying to fix it if you want? The original speakers might be expensive but if you only have to replace a couple might be cheaper than four new ones. Four Eminence Deltas would set you back £360 for example. You can get European made speakers cheaper but not by much if you want good quality. Generally speaking it's as cheap or cheaper to trade in a cab and buy a used cab than to do a speaker swap, changing speakers is likely to reduce the value of your cab over keeping it original so long as it is in good working order. If you just fancy a project then that is great, we can talk about what you are trying to achieve and try and find something to suit. I'd try and fix the cab first though.

Shut up and.... no I can't be so rude There are a few Beymas that are really good value, the CMV range are across the board good value. It's a shame they stopped making the SM212 though. In this case the choice of the Celestion Pulse was a good one mainly because of it's mid-range performance. Most bass/mid speakers have a pronounced peak at cone break up. At high frequencies the out part of the cone can't keep up with the centre and the cone starts to flex and this creates frequency anomalies. For a 10 the response is fairly flat and rolls off evenly and this makes adding a horn driven through a simple high pass filter relatively simple. To get a flat response from most bass/mids you need to have a 'proper' crossover and control the roll off for the bass unit. The inductors for this tend to be large and relatively expensive and beyond that you often get other frequency problems which need extra components and design work to tame. You'd be amazed at the manufacturers who don't bother doing more than a cursory job on their crossovers. It's probably why some bassists don't like horns; there's nothing wrong with the horn but the crossover leaves little frequency peaks that sound harsh/distorted/honky. So Win ISD models the bass response and you may well find better 10's but the Pulse was chosen because it gave good enough bass but a really helpful treble that enabled a good response with just three cheap components in the crossover.

Hi Al, As ever mine was just a factual post. There was a study and both in terms of economics and Live music performances Australia has done way better than us. That is still true. The rate of vaccination in Australia is poor for a wealthy country and frankly the worlds media coverage of Astra Zeneca hasn't helped, taking aspirin or paracetomol is far more dangerous and my guess is most anti-vaxers pop pills with a lot less caution than I do. Getting one bit of the equation right doesn't stop you making other mistakes. I note that the governments science advisors including SAGE members have a model that is predicting another 50,000 people killed by Covid in the next 12 months as a median figure due to the current relaxations. They clearly see this as acceptable. That's of course not including other cancelled treatments due to Covid bed blocking. The NHS is already starting to turn people away from some hospitals. I note also that the trials of opening night clubs and other indoor events have resulted in over a third of the participants contracting covid and that was the Alpha strain. Indoor events are pretty much super-spreader events. Outdoor ones much safer Further I am concerned that letting Delta rip through a population where around 1/3 of the population is unproteced is, according to DR Phillip Hammond "the prefect petri dish for breeding vaccine resistance." Of course vaccine resistance means the virus is also bypassing natural immunity. Vaccines only work by triggering our natural immune system. There are a number of coronavirus genes out there we wouldn't want to meet with Delta. Viruses swap genetic material if you have co-infection. Co infection becomes common with something as infectious as Delta. One of the genes we know is out there, as reported in New Scientist, would make Covid 100 times more infectious than Alpha. Others out there would make it more deadly than Delta. There is no predicting random comings together but when the improbable looks so bad it is better to avoid the random. I'm sure the migration of lemmings is also a glorious sight, I know how it ends!

I think that's all fair comment, though I only built the cab @stevie did the tuning and he did this on the basis of measurement of the final cabs response. The original design was shaped by the need to keep everything easy to build and the availability in the UK of a ready made port was an important factor. We were looking for something cheap, easy to obtain and sourced from a well established supplier so likely to be available for a few years. This one also has a decent lip to cover up any dodgy cutting of the hole. When I did the modelling on WinISD I found my 'best' response was higher than the final tuning and that the original port without the addition of extra length would give that tuning. The extra card extension was added as a result of frequency tests on a built prototype. The frequency plots are there in the text somewhere. In my original version of the cab I used plastic guttering down pipe. One of the things we discovered testing is that two narrow ports start to make port noises (chuffing) at lower power levels than a single bigger port with the same cross sectional area. We hadn't seen this in any literature. Like @agedhorse I shudder at the idea of folded ports. Like all the commercial designs we have looked at and pretty much any practical cab there are compromises in this design. Like the crossover design and choice of drivers the port was an issue of cost and availability. Actually 52Hz sounds about right, I measured 53Hz by looking at impedance on mine. I don't think it is worth re-tuning unless Steve comes along and says there is a problem, my cab sounds great given the cost of the components and pretty much as i'd have expected from the design software.

Get a couple of coats of Tuff Coat on it and it will look the business. You've done a good job with that and I really hope you get a lot of happy hours using it. I think you are right about the volume, WinISD shows a broad band output of about 118dB at 200W which is fairly typical for a 10" speaker. Adding a second would give you 123-4dB depending upon the amp which puts you well into the gigging range. It would work well with an untweetered Pulse10 in the same sized cab underneath if you wanted to save a little money. In terms of practicality I use mine as my go to for rehearsals. I like it for gigs too because I have PA support so it is just a monitor and is plenty loud enough for me to hear everything and it sounds good. The sound engineer loves it because it's not overwhelming the vocal mics and my drummer is not so keen because he likes to 'feel' the bass. I don't think building it in 12mm ply would give you any advantages other than weight saving and maybe a better quality ply would be tougher and easier to finish. Have you weighed the cab? Mine came out at dead on 10kg. Thanks for the review, it really helps anyone thinking of a build having an opinion from someone unconnected with the design. Well done Phil

Yeah 15mm helps a lot as does denser/heavier ply. My preference is for 18mm hardwood ply. Wickes in particular used to do a really nice marine ply with good facing veneers. It's a long time since I've been to Wickes due to the plague but they still sold a nice exterior ply last time I went. For my own use I do like a really tough cab which is not going to disintegrate if it gets a bit damp. It's a tough life going between van and gig. Fortunately cabs are getting smaller and ultimate light weight is not a big concern for me, and let's face it these cabs are pretty small. This cab is 12mm poplar ply because that is what Stevie preferred. My original 'Easy Build' cab was 12mm because that was what i had enough off cuts of to build the cab. Not very scientific! What I'd really like to do is build a series of cabs all the same internal volume and weight with different bracing systems and compare them for cab induced resonances. Is a 9mm cab with an extensive equal mass of bracing better than an 18mm cab with no bracing, or enough better to be worth the effort for the home builder. There is a lot of theory about panel resonances and the car industry has done a lot of work to silence panel resonances. What there isn't is a simple piece of software to design the bracing for a speaker cab so a lot of it is a combination of experience and suck it and see. A friend of mine works for Jaguar/Land Rover and one day I'm going to pump her for inside information. Most of what the auto industry do is to add mass in critical places and they use a lot of 'lossy' materials to damp resonances. My current hi-fi speakers have a lead/MDF sandwich structure with a plastic foam joining them. I'll leave the lead lined bass cab to Trace Elliott though

Blue Aran - The UK's no.1 Loudspeaker Component Stockist > Speaker Components > Crossovers & Components > Fuse Bulbs the problem is which one, like all 'fuses' they come at different values. They are just light bulbs but you need one that heats up (and increases its resistance as a result) at just the right point to protect the tweeter but not cut it out unnecessarily. The bit you are looking at is just the glass case it's the coil inside that is doing the business. However this one seems to work so it isn't needed (probably) If you just want to test it then take it out and just put a wire across the terminals keep the power reasonable and you shouldn't damage the tweeter but it it's the bulb that's causing the fault it would go away.

Just in case anyone is following this sorry tale this is the ending. I don't know if the call to Romford resulted in any action as predictably there was no follow up email and no action at all with the delivery. I then had a week of trying to ring Romford including 5 requests for a call back a couple of emails and a lot of posts on their social media. I made over 20 calls of varying length none of which were answered at all this time. At one point after telling me how important my call was and that they would get to my call they hung up. I wonder what you do when a business won't respond to any attempt to communicate. I also emailed the German store and after a week.... no reply. I finally resorted to ringing back each time I was cut off. After slightly more than 10 attempts someone picked up. It sounded like a very weary teenager but he was polite and so was I. It turns out according to him that all the calls are answered in the shop by whoever isn't serving. That would explain no calls back and no answering. I guess they serve people in the shop first so only answer when they are absolutely empty. Anyway in the 20 mins or so i'd spent on the phone there had been movement DV247 Music Store had actually given the courier my order. Unfortunately the courier is based in the middle of the floods in Germany, can't blame them for that and at least I then knew my order hadn't been lost. It took another few days to reach customs where my previous delivery had stumbled but this time they had the paperwork right. Three days to reach Exeter who delivered a clearly opened, and very battered parcel the next afternoon. That morning I got a generic but apologetic email from Germany, so they did reply in the end. Everything inside was fine however, the two lights work perfectly and the new ABS bass hardcase is great, for £55 it's pretty fabulous. I like a happy ending So would I do it again? Well first of all I don't think they are dishonest as some are saying on the internet, just completely disorganised and beyond that the Romford store is just not set up to deal with online trading. I think the first parcel wouldn't have arrived without chasing but the second one would have. For me the average time to arrive was 4 weeks and I spent probably the best part of a day chasing. Their own brand stuff is genuinely good value and i did probably save £100 in the end. If anything breaks I know I'm in for a world of trouble. Warranties mean nothing if people won't communicate. I wish I'd paid the extra to be honest. I'd warn people to be extremely cautious about ordering anything from DV247 for the foreseeable future as you will be buying with no acceptable after sales backup and potential long delays. Be aware that you aren't ordering from a UK company and they are probably further from sorting UK exports than their other German rivals.

Bad luck, you wouldn't want to have to sort this at a gig. I think I might check some of my gear. Hope you sort it all.

I'd personally be surprised if they did use the same drivers as the 7 series. They make and sell a wide range of bare drivers and speaker driver manufacture is where they come from. They seem to have a very active design team and a policy of constant steady product development so this doesn't come as a surprise. They don't make a dud as far as I can see and I'm quite prepared to believe these are better than the 7 series. A more rigid cab would be an improvement and that may be contributing to extra weight. They may also have increased the bass driver's excursion, their bare drivers are often not spectacular in that area. I had my 310's on poles to test and program my new mixer (also RCF) and they sound stunning on poles in a room with decent acoustics, to date I've only used them as floor monitors so getting them away from floor reinforcement really opened them up. vocals were stunning and that is just about their cheapest speaker. I'm looking at 732's as optimum for me at the moment. There's a point where cost increases give only marginal improvement and any band I play in wouldn't merit better rendition of a rubbish signal I'd take the 2000W+ with a big pinch of salt, it will be music power or peak power or some such nonsense. The heat dissipation and excursion of the drivers mean that they wouldn't handle this power and the DSP will stop it reaching the speaker anyway. Class D watts are so cheap and light a lot of manufacturers are using a standard amp to power all their speakers and throttling them down with the DSP to match the drivers. The advertising departments love it because they can claim 2100W. Everyone is at it at the moment and there is a bit of an advertising arms race. It looks like they are aiming these at the lower end of the hire and touring market. I've little doubt they sound better than the 7 series, they have a knack of introducing well worked out products and optimised designs. I can't wait to hear my first one and see what they've done this time.