Ports are used to tune the volume [internal volume of air] in the cab. It allows you to use smaller cabs than you would be able to without them.

If it’s your first time building speakers, I’d steer away from doing bandpass boxes and stick with ported radiators (bandpass are a pain to get right, and you’ll need well developed woodworking skills to even have a hope of getting it right – as a quick note, I’ve never heard of bandpass mid/tops – they’re generally used for bass and sub unless I’ve missed something?).

With a ported cab you at least have the ability to tune the box to take account of the build innacuracies (basically the port allows you to either tighten or loosen the bass by lengthening/shortening the vent – this causes the tuning frequency of the cab to either go up (by lengthening), or down (by shortening) to get it right. Not having them turn out perfectly box shape is actually more of a benefit in most cases too (if the sides aren’t perfectly paralell you cut down on a lot of the internal reflections and standing waves that mess up the sound).

What I have to say about scoop bins is probably best left unprinted… I may be unnecessarily biased about this, but I have yet to find a scoop design that has any audible benefit in low/sub reproduction over a simple radiator – a horn at least has the benefit of extra throw (much like cupping your hands over your mouth to focus the sound further away), but the basic idea behind these designs is flawed (because it relies on the transistor effect which requires a logarithmic flare opening – possible with 2″ top drivers – and very effective, but ends up impossible to achieve with an 18″ driver in any meaningful way). I’ll get plenty of argument over this likely, but you pays your money, you takes your choice really – the scoop and horn designs are markedly more complex, and easy to get wrong for a benefit thats nebulous at best….. Put your long throws (in this case relating to the cab design – you get drivers that are labelled as long throw, but this relates to the Xmax zero to peak linear displacement, not the focus distance) in after you’ve sorted the near field, and when you start doing stadium gigs…

If you can handle waiting a month or two, the next part of the sound system building how to I’m doing is on the theory of cabinet design (I’m going to cover closed, ported, bandpass and horns to begin with (although I may try and blag elretardo into doing the horn section for me as my opinion of bass horns is pretty low – he likes them far more than I do and will likely do a better job :weee: ), and maybe do some of the more esoteric ones like 1/4 wave tubes and whatnot as an afterthought). That all presupposes I get a bit of time though (I’ve been promising Dr B it’s coming since last september, but people keep finding jobs for me). The part after that is going to be on overall rig design and how to best plan for any particular purpose which you may also find helpful – again, no guarantees as to when it will be done by though…

If you cannae wait, I’ll put a few links below that are worth a look – take most of the claims for any design with a pinch of salt obviously (response curves are a general indication only – much will depend on your building ability, and the materials you use). There are some excellent designs among them though, and lots of info on the whys and wherefores…

Speaker designs (mostly from the Fane big rig cookbook, and fairly old now – still good though.) Most of the bass designs are horns – so expect to be annoying peeps in the town 4 miles away if you build them :wink:.

Dancetech’s site – speaker designs about 1/2 way down, but lots of good info on sound dispersal etc (apart from the bit about bass not having directionality which is nonsense).

Another bunch of designs – all sorts here. Some good, some hysterically funny. Many are in Czech or Polish (I think), but the measurements are in maths language and so usable.

Another link site with designs. I particularly like the EV pro facts #7 which has a bunch of ported designs (64) and measurement info that allows you to get the box right for pretty much any speaker you have the Thielle/Small specs for with a little work :weee:. Some of the links don’t work any more, but most of the really useful ones do.

The JPO linklist – a huge list of links relating to audio design. Some are brilliant, and some are… not:wink: Like anything, dinnae believe everything you read on the web….

Speakerbuilding.com – well worth a read – not all PA, many are hi-fi designs, but some seriously inventive ideas (always wanted to try the Ammonit, just to see if all the effort is worth while…)

Speakerplans.com – some good designs if you really want to go for the deep end and see if you can swim… If you go to the “sub plans” section, the “C sub” and the “184 sub” are both 4th order bandpass designs – primarily for PD drivers, but the 184 sub has a list of other drivers and mods to make for them (and includes the fane 18XB which is IMO the best bass driver on the planet :wink:). Not designs for the faint hearted though, and if you’re new to cab building expect to consign the first try or two to the “firewood” pile.

The Eminence Beta’s you’ve got are designed to be put in a ported radiator (think it says this somewhere in the advertising bumpf). Good drivers – we use a pair in monitor wedges, and they’re solid drivers. Sound isn’t as good as the gamma’s or kappa’s, but well recommended for use as mids and fairly tough – I’ve driven the wedges at well over the 225W RMS (accidentally obviously :wink:) and they’re none the worse for it… Dinnae expect them to do the rumbly jungle sub you’re looking for though, cos you likely will break them if you do. You need bigger cones for that….

As a final thought, please for the love of god (or gaia, buddha, whatever) when you build your cabs, DON’T FORGET to put some acoustic wadding inside (this is usually marked in the plans, but if it isn’t make sure you cover at least 3 of the internal panels). Loft insulation does this well, or you can buy purpose made wadding (which will be essentially the same but 3 times the price). Come across a few rigs that haven’t done this, and it will make your whole rig sound like a bag o nails…:wink:

Turned into another long rant :crazy:…. Hope it helps raaaraaaraaa

The idea behind horns (originally) was more to try and achieve the kind of amplification that is possible with an instrument (like a trumpet), where the sound is amplified by the bell shape at the exit. Basically, what happens is the flare causes the air pressure countering the exiting sound pressure waves to match impedance. The result of this matching is something called the transistor effect – where a small input results in an exponentially increased output of the same sound. A great idea, but in practice not easy to achieve 😉

fair enough, was reading the list at the first bit of the post where you mentioned a old Realistic amp (I remember these from the early 90s!) I’d use that for the monitor speakers only TBH….

The pics look wierd because the tuning frequency is wrong – you should tune your boxes to a value slightly higher than the Free air resonance frequency (Fs) given in the driver specs. You do this so the unnatural peak in response at resonance is damped by the air mass of the box and ports (your box response will have a steep rolloff below the tuning frequency, essentially damping the tendency to resonate inherent in the driver).

The response curves show a box tuned way above the right frequency for the driver, resulting in a large peak in response at the tuning frequency – this is very bad (the main reason for a box in the first place is to make the response as flat as possible – your speakers and amps should be as linear as possible, meaning they should introduce as little alteration in the character of the sound reproduced as possible.)

You wire it:

//////////////////////////////////////////// |—3–Amp—4—Bass Speakers
\\\\\\\\\\\\\\\\\\\\\\ |
Decks—>—-Mixer–1–EQ—2–Xover|—3–Amp—4—Mid Speakers
\\\\\\\\\\\\\\\\\\\\\\ |
//////////////////////////////////////////// |—3–Amp—4—Top speakers

The Actual wires needed will need you posting the makes and models of each piece of kit – what I would generally expect to find on the equipment is:

1) Mixer to Eq – 2 cables, one for left and one for right channel would likely be female XLR to either male XLR, or 1/4″ TRS jack (the XLR cables are wired with pins: 1=Earth, 2=Hot signal, 3=Cold signal… If wired to a TRS jack, it will be wired: T=Hot signal, R=Cold signal, S=Earth. If one end is not balanced line – likely the mixer if any, then just short the cold signal to the earth one at the non-balanced line end)
2) Eq to X-over, again one for each channel likely female XLR to male XLR, wired as above.
3) X-Over to amps – one stereo pair per frequency band (ie lo, mid and hi). Should be Female XLR to male XLR, but may be female XLR to 1/4″ jack – see the wiring for 1 for wiring info. You will have 3 pairs (ie 6 cables)
4) Amps to speakers – could be various combinations depending on the amps and speakers. Basically each is a 2 core cable, with a +ve and -ve. Hopefully it’ll be speakons both ends in which case 1+ and 1- need to be connected at each speakon – ie 1+ to 1+, 1- to 1-. If you have Jacks, then the tip will be +ve, and the sleeve -ve. If XLR, pin 1 will be the -ve, and pin 2 the +ve….

Hope that helps – if you need more help, post the makes and model numbers of each piece of kit for me and I will go and check the connectors etc…raaaraaaraaa

Thats pretty much it – the phono to XLR’s will only be wired pin 1 and pin 2 on the XLR end (they will likely short pin 3 to pin 1, but not always). That way they are wiring the signal of the phono plug (ie the center pin) to pin 2 of the XLR (which would be the “hot” of a balanced line cable), and the sleeve of the phono to pin 1 (which is the signal ground of a balanced line). Pin 3 (which is the “cold”, or inverted signal in a balanced line) is not used, and is normally shorted straight to ground (pin 1)…

Always happy to help though (you can PM me when you do a party if you want though – I live a ways from sheffield, but if I’m around the area I could handle a Jungle night out :wink:…. raaaraaaraaa)