DIY 2x8" cabinet build

[pandathe3]

So i was walking through maplin yesterday, looking at the speakers and noticed some Eminince 8" 225watt bass/mid drivers which got me thinking! I need to build myself a 2x8" cabinet to sit ontop of my schroeder 112 cab. The reason for a 2x8 cab is because the drivers are relitivly cheap, the are small, and fairly light. Also, my Sch provides my thump and (in theory) my 2x8 can give me some attack in my sound.

While the project is in progress, i plan to purchase a LH1000. I will have the LH1000 running 500watts into each cab, i can also balance between each cab too.

So, as follows is my plan for the cabinet build:

2x eminence beta 8s OR 2x Fane Sovereign 8s. Both 225watts each.
550watts @ 4 Ohms
No tweeter.
17"w x ??"h x 12"d.


It seems pretty simple to be honest, i wont need a crossover as i have no tweeter.

This will be my first build so i am unsure about a few things which is why ive posted here.

Basically, the biggest point is tuning/porting my cabinet. Ive tried to look up guides ect on the net but i really dont understand. If someone can provide an idiots guide to tuning a cabinet thatd be great!

So, as i will just be using the 2 drivers is it as easier as wiring them into a speakon socket at 4ohms? I was also thinking about putting a passive tone control on the back allowing me to roll off treble of the cab.

Also, a few ideas ive thought about/need help with?

Which drivers? The fanes are cheaper but looking at the beta8s responce chart they will give me the sound i need (boost around 1k).

General points about porting. Is the depth of 12" going to be to much for the 8s? Shall i seperate the drivers? Tubes or 'eden style' porting or schroeder (cut corner) style porting. Id imagine this is harder to get sounding good, but much lighter

So thats pretty much it. Pointers on porting please cheers!

[umph]

download winisd for port tuning it's fairly straight forward to work out and i'd make the cab as tall as you want! Make sure you line the drivers vertically aswell to improve dispertion since they'll be driving the high end.

[Mr. Foxen]

[quote name='pandathe3' post='993533' date='Oct 19 2010, 02:04 PM']Also, my Sch provides my thump and (in theory) my 2x8 can give me some attack in my sound.[/quote]

What theory is this? I think you should search 'mixing driver sizes' and how they can implode the whole world.

[Phil Starr]

If your existing cab gives you enough bass then you have enough bass. Adding these speakers will give you more midrange although as I think you've already spotted the beta has a midrange peak and the Fane is relatively flat.

The simplest way of building this cab is to make a sealed cab. This will reduce the bass from the 8's slightly but will leave the mids unaffected and make the build a lot easier. It will also improve the transient response and so long as it is sealed will guarantee a successful build. You will also end up with a smaller cab.

If you do go for a reflex cab then tune it with tube ports as it is relatively simple to re tune if you get your calculations wrong, or more likely that the speakers don't exactly match their spec.

You need to get to grips with one of the free design programs winisd or AJDesigner [url="http://www.ajdesigner.com/speaker/index.php"]http://www.ajdesigner.com/speaker/index.php[/url] are both useful, Win is more flexible and AJ is easier to use. If you get really stuck I'm sure someone here will calculate a volume for you. When you enter Vas into the programs you need to double it because you have two speakers.

[pandathe3]

Thanks Phil for clearing up my 'in theory' reply.

As for lining them vertically.....As i still want to keep the cab compact as possible, i think i'll measure it up and see what dimensions i come up with, maybe not fully verticle but definitely diagonal.

Ive spoken to a friend who wouldnt mind making the cuts and putting it together for me. I just need to 'find' a cutlist, ha!

I shall download winisd tonight and start my desiging. I do want to keep this build relativly easy but i want to get the best possible sound while keeping it compact and as in expensive. So, tube porting sounds the best way to go or how hard would it be to design a Schroeder style porting? Cutting the corners from the speaker baffle board?


Cheers for the input guys!

[thinman]

There's no certainty that what you're doing will be wothwhile.

It may sound great or it may sound rubbish - it's an unknown.

A "proper" design would probably include a crossover and be on the basis that the 1 x 12 cab was tuned to do the very bottom and the 2 x 8 cab tuned for mids only - what you'll have is two differing designs trying to do the same job.

As Mr Foxen stated, mixing of driver sizes to do the same job (rather than being part of a multiway design) is hit and miss.

There are lots of people out there mixing 15s and 10s and if they're happy that way then fine, but in terms of "correct" design it's a no-no.

Wiring these may also be interesting if they're 8 ohm drivers. If all three are in parallel you'll have a 2.6 ohm load - quite low for a lot of amps. If the 2 x 8s are in series and in parallel with the 12" then they may well get drowned out.

[Mr. Foxen]

Also important to note is that WinISD isn't very good at midrange, it is ok for tuning boxes for bass, but the line it gives might not very well reflect what you'll get higher that 500hz or something, there are loads of other variable, like reflections from inside the cab and suchlike that affect midrange frequencies.

[Phil Starr]

[quote name='thinman' post='1000350' date='Oct 25 2010, 07:23 PM']There's no certainty that what you're doing will be wothwhile.

It may sound great or it may sound rubbish - it's an unknown.

A "proper" design would probably include a crossover and be on the basis that the 1 x 12 cab was tuned to do the very bottom and the 2 x 8 cab tuned for mids only - what you'll have is two differing designs trying to do the same job.

As Mr Foxen stated, mixing of driver sizes to do the same job (rather than being part of a multiway design) is hit and miss.

There are lots of people out there mixing 15s and 10s and if they're happy that way then fine, but in terms of "correct" design it's a no-no.

Wiring these may also be interesting if they're 8 ohm drivers. If all three are in parallel you'll have a 2.6 ohm load - quite low for a lot of amps. If the 2 x 8s are in series and in parallel with the 12" then they may well get drowned out.[/quote]

It's true that any DIY speaker design is hit and miss but the idea that mixing speaker sizes is 'incorrect' in any way is nonsense. You are going to get cancellation/phasing problems with any two speakers spaced apart in a single speaker but that will happen equally if the speakers are the same size. If you mix two different speakers then they will have all sorts of differnt peaks and troughs in their frequency responses and mixing these will be just about impossible to predict although in my experience it does tend to subjectively smooth the sound as the peaks rarely coincide. This in the end is going to be an instrument speaker so the aim is not to have a flat response but a musical one.

You could add a crossover but it isn't necessary. It would change the sound and you might prefer it or not. I did think of adding a capacitor in series with the 8's which would roll off the bass at 6dB/octave and increase their power handling (and be cheap)

He doesn't need to worry about 2.6 ohms. It's a stereo amp.

[quote name='Mr. Foxen' post='1000505' date='Oct 25 2010, 09:16 PM']Also important to note is that WinISD isn't very good at midrange, it is ok for tuning boxes for bass, but the line it gives might not very well reflect what you'll get higher that 500hz or something, there are loads of other variable, like reflections from inside the cab and suchlike that affect midrange frequencies.[/quote]

No computer Thiele/Small modelling tells you anything about midrange it just tells you about the interaction of the box and speaker at frequencies around the resonant frequency of the speaker in question.

I still think that there is little point in you designing a ported cab however. It will increase the bass your 8's give but not by much and you aren't using them to add bass but to pep up the mids if I understand you. If this is right there are no advantages in a ported cab and several disadvantages, so why bother?

[alexclaber]

I agree with what Phil's saying! I'd put the 8"s in a small sealed cab, vertically aligned. If the dimensions of that bother you then lowpass one of the 8"s at about 1500Hz. Actually, re-reading I see that you're referring to a 1x12" cab, in which case you only need one 8" to keep up. Small sealed cab, highpass with a capacitor. Done. LH1000 is overkill to power them - they'll both reach their limits way before it does. If your current cab is a 4 ohm cab then by placing the highpass on the 8" high enough you can still present a suitable load to the amp (as the Schroeder's impedance will increase steadily though the mids and highs).

[Dubs]

This is a very interesting read. Sorry to hijack - just wondering what the implications/effects of aligning the drivers diagonally (rather than vertically) would be on the dispersion? Kind of like this:

[alexclaber]

If you draw a line between the centres of the drivers, as the response shifts from omni-directional to directional it will shift towards radiating roughly in a cylindrical pattern with the the central axis of the cylinder along that line. So with a horizontal array you get lots of floor and ceiling reflections (bad) and poor output left and right, whilst with a vertical array you get minimal floor and ceiling reflections (good) and strong output left and right. The downside is that you have to make the cab a different shape to what everyone's used to! With a diagonal array you end up with the sideways output on one side going up and on the other side going down.

[Dubs]

[quote name='alexclaber' post='1001012' date='Oct 26 2010, 12:34 PM']With a diagonal array you end up with the sideways output on one side going up and on the other side going down.[/quote]

Ah ok. So would you say that a vertical array is [i]significantly[/i] better than a diagonal array?

[alexclaber]

[quote name='Dubs' post='1001044' date='Oct 26 2010, 12:52 PM']Ah ok. So would you say that a vertical array is [i]significantly[/i] better than a diagonal array?[/quote]

Well I guess a diagonal array could be a good idea if you always play on hillsides facing in the same direction.

[Dubs]

[quote name='alexclaber' post='1001057' date='Oct 26 2010, 01:00 PM']Well I guess a diagonal array could be a good idea if you always play on hillsides facing in the same direction.[/quote]

ok I get the idea...

[Phil Starr]

[quote name='alexclaber' post='1000943' date='Oct 26 2010, 11:21 AM']I agree with what Phil's saying! I'd put the 8"s in a small sealed cab, vertically aligned. If the dimensions of that bother you then lowpass one of the 8"s at about 1500Hz. Actually, re-reading I see that you're referring to a 1x12" cab, in which case you only need one 8" to keep up. Small sealed cab, highpass with a capacitor. Done. LH1000 is overkill to power them - they'll both reach their limits way before it does. If your current cab is a 4 ohm cab then by placing the highpass on the 8" high enough you can still present a suitable load to the amp (as the Schroeder's impedance will increase steadily though the mids and highs).[/quote]

This is great advice. Using a single unit would be perfect, you should also consider using a 6" unit like the Fane sovereign.

You'll need a 13.25 microfarad capacitor for a 1500Hz crossover using an 8ohm speaker, though they don't make them in this value, 12 or 15uF would be close enough. Reversible or non-polarised electrolytics are a cheap option costing a few pence. I would try lower crossover frequencies though. I'd get a bunch of 10uF capacitors and try adding 1,2,3,4 etc. in parallel and seeing what sounded best before making a final decision about the crossover frequency. doubling the capacitance will halve the frequency.

[quote name='alexclaber' post='1001057' date='Oct 26 2010, 01:00 PM']Well I guess a diagonal array could be a good idea if you always play on hillsides facing in the same direction.[/quote]

[pandathe3]

Hey guys, thanks for all the input.

Just so you guys get the idea: i chose the 2x8 build for several reasons. Most i mentioned before (weight, portability ect ect) increased midrange is another factor but maybe the biggest reason is having all the headroom in such a compact (and splittable) rig.

As it is my first build, and is being built for use with the 4ohm 112 i will be taking what seems the easiest route.

Sealed 2x8 enclosure (lined horizontally, so its as small as possible).

The box design can be easily done. Just abit stumped on the wiring. If someone could present a rough wiring diagram of the speakers wired to 4ohms, then to speakon thatd be great.

The idea of a single 8 sounds good but i need the 2 x 8 to handel the 500watts of power.

Im quite like the idea of the 12 and 2 8s. You all must understand that this project is specifically being built to be coupled with my schroeder. I have been thinking about designing a 12 + 2x8 for the floor up. If done properly i think it could sound great! The plan would basically take the crossover and tweeter and place it in the 2x8 cab, leaving the 12 by itself! Porting for both cabinets, id then use fanes, and keep them tuned to get as flat as possible frequency response. SORTED!

Ofcourse that will come after this and this first build is to give me an idea of what im working with and howthe config will sound.

[Colledge]

i'm guessing that the drivers are 8ohms each. in that case the wiring is easy peasy. just both drivers in parallel.... that means a wire going from the input socket of the cab to each cab and then a wire from each opposite end of the driver back to the opposite end of the input socket, without any wires going between the drivers.

[Phil Starr]

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']Hey guys, thanks for all the input.

Just so you guys get the idea: i chose the 2x8 build for several reasons. Most i mentioned before (weight, portability ect ect) increased midrange is another factor but maybe the biggest reason is having all the headroom in such a compact (and splittable) rig.

As it is my first build, and is being built for use with the 4ohm 112 i will be taking what seems the easiest route.

Sealed 2x8 enclosure (lined horizontally, so its as small as possible).

The box design can be easily done. Just abit stumped on the wiring. If someone could present a rough wiring diagram of the speakers wired to 4ohms, then to speakon thatd be great.

The idea of a single 8 sounds good but i need the 2 x 8 to handel the 500watts of power.

Im quite like the idea of the 12 and 2 8s. You all must understand that this project is specifically being built to be coupled with my schroeder. I have been thinking about designing a 12 + 2x8 for the floor up. If done properly i think it could sound great! The plan would basically take the crossover and tweeter and place it in the 2x8 cab, leaving the 12 by itself! Porting for both cabinets, id then use fanes, and keep them tuned to get as flat as possible frequency response. SORTED!

Ofcourse that will come after this and this first build is to give me an idea of what im working with and howthe config will sound.[/quote]
One of us is confused, it may be me. A sealed cab is an alternative to a ported cab, are you proposing to build two cabs?

Don't get me wrong I'm all in favour of self building and trying new ideas out and I think the idea of bassists adding smaller speakers to a rig is excellent. I've also sketched out a design for a 4x8 using the Fane Sovereigns and am working on designs to add upper mid to my own rigs. I think it is possible that your lack of theoretical knowledge may let you down in achieving what you want in terms of sound.

You could use the 8's in two ways; you could build a full range speaker which would work as a stand alone/practice speaker which would have a different and more extended response to your 12 (kind of like a smaller version of a 15+4x10) or you could use it as a specific midrange speaker to take over and extend the higher frequencies, a tweeter for bass guitar. Both might work but they are alternatives and I'm not sure which you are trying to achieve.

If you are after augmenting your Schroeder with a standalone speaker then you don't need a crossover and you might consider a sealed cab or a ported cab for this purpose. Both have advantages and disadvantages. You would need a stereo amp if you use a 2x8 or an amp capable of driving into 2 ohms. You might even want to consider a 4x8.

If you are going to use the 8 as a midrange speaker taking over from the 12 at higher frequencies then you only need one speaker. Because even a simple capacitor crossover will filter out the bass (where all the watts are) your 8" speaker will handle its share of 500W with no problems. There is no point at all in using a ported cab for this purpose. It would be worse than a small sealed cab.

You need to make a choice, are you building a mid/high cab to augment your 12 or a multiple 8 to share equal duties?

If it helps you could have a look at this [url="http://www.ultimate-guitar.com/columns/gear_maintenance/cabinets_for_guitars.html"]http://www.ultimate-guitar.com/columns/gea...or_guitars.html[/url] and then start googling.

[alexclaber]

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']Sealed 2x8 enclosure (lined horizontally, so its as small as possible).[/quote]

Doing this defeats the point of using 8"s. Use one 12" instead and you'll get better off-axis performance than two horizontal 8"s.

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']The idea of a single 8 sounds good but i need the 2 x 8 to handel the 500watts of power.[/quote]

No you don't. The highpass filter massively reduces the power going to the 8".

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']Im quite like the idea of the 12 and 2 8s. You all must understand that this project is specifically being built to be coupled with my schroeder.[/quote]

Exactly. So there's little point pairing a sealed cab with a ported cab because of the phase shifts and power handling issues low down - but if the sealed cab isn't doing the bass then that isn't a problem. And then you only need one 8". Ideas are good - but they're not always right first time!

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']I have been thinking about designing a 12 + 2x8 for the floor up. If done properly i think it could sound great! The plan would basically take the crossover and tweeter and place it in the 2x8 cab, leaving the 12 by itself! Porting for both cabinets, id then use fanes, and keep them tuned to get as flat as possible frequency response. SORTED![/quote]

If only it was that simple...

[Dubs]

[quote name='alexclaber' post='1003462' date='Oct 28 2010, 10:31 AM']Exactly. So there's little point pairing a sealed cab with a ported cab because of the phase shifts and power handling issues low down - but if the sealed cab isn't doing the bass then that isn't a problem. And then you only need one 8". Ideas are good - but they're not always right first time![/quote]

What are the problems when pairing ported and sealed cabs? After reading this thread a few days ago I was half considering to make a sealed 2x8 vertical array cab with the Fane speakers to make a matching pair with my 1x10 ported cab that I made a few months ago.

[LawrenceH]

[quote name='Dubs' post='1003474' date='Oct 28 2010, 10:44 AM']What are the problems when pairing ported and sealed cabs? After reading this thread a few days ago I was half considering to make a sealed 2x8 vertical array cab with the Fane speakers to make a matching pair with my 1x10 ported cab that I made a few months ago.[/quote]

It's a problem if the sealed cab goes low enough to interfere with the bass from the ported cab to a significant degree, as they won't be aligned below the point where cabinet/driver interactions start contributing to a noticeable delay in the bass response.

[Phil Starr]

[quote name='Dubs' post='1003474' date='Oct 28 2010, 10:44 AM']What are the problems when pairing ported and sealed cabs? After reading this thread a few days ago I was half considering to make a sealed 2x8 vertical array cab with the Fane speakers to make a matching pair with my 1x10 ported cab that I made a few months ago.[/quote]
It is the problem you always get with multiple drivers. If you accidentally connect up two speakers with the connections reversed on one then as one goes forwards the other is going back and the air doesn't move the result is you get no bass. You can usually try this with your hi-fi if you want. In this case the speakers are 180 degrees out of phase. If two speakers are different distances away from your ears then the sound from one arrives a little later than the other and are out of phase by differing amounts. You also get phase delays at a reflex port. All this causes frequency irregularities and lobing of the radiation pattern of the speaker system.

I hope Alex doesn't mind me answering in what is his forum but I'm going to stick my neck out. His designs aim at a clean and predictable bass response and mainly try to get the most out of a single driver. By investing in modern, long throw and well damped, high power drivers you get rid of the problems of multiple drive units and one good driver costs no more than a bunch of cheap ones. Because you have a well engineered speaker you can then use EQ to get the tone you want.

There are loads of design considerations when you mix drivers, which are genuinely too complex for a forum like this. There are solutions, the easiest being to stop the bass going to one driver with a crossover. Some designs for an instrument speaker are messy and ill thought out but work despite this, in the sense that some people love a highly coloured sound.

It is going to cost you £100 and a couple of days fiddling to find out if your plans will give you the sound you want. What you are suggesting isn't wrong it is just that there is no way of knowing what it will sound like.

Edited October 29, 2010 by Phil Starr

[pandathe3]

Thought this is ideal for the thread:

[url="http://www.talkbass.com/forum/showthread.php?t=704484"]http://www.talkbass.com/forum/showthread.php?t=704484[/url]

Looks a very good cab!

Basically, my first build is going to be a cab to put along side my schroeder. Id prefer 2 speakers, for a few reasons. However, i understand that i only NEED 1 for the purpose of pushing the midrange. So for now i will make a small sealed cab and see how it sounds.

But, i would still like to build a 2x8 to sit above a 12. Would it be really that hard to build?

I know my knowledge isnt the best, but ive been sitting here a while struggling what to write. So bear with me if things dont make sense. So here goes.

I know the cabinets would need a crossover, but would each cab be full range on its own? I know the 8s wouldnt go as low as the 12 but id like to be able to use either/or cab by itself. I ask this because the amp is stereo, so the 12 wouldnt be able to act as a Bass Only cab unless i ran it bridged.

Cheers

[Dubs]

[quote name='Phil Starr' post='1004980' date='Oct 29 2010, 11:55 AM']It is going to cost you £100 and a couple of days fiddling to find out if your plans will give you the sound you want. What you are suggesting isn't wrong it is just that there is no way of knowing what it will sound like.[/quote]

Oh yeah definitely, I know this, I'm just after a bit more basic knowledge (thanks for that BTW). I wouldn't be doing it solely for the end result - 50% a nice looking usable mini rig, 50% just the hell of doing it

[TheGreek]

Thinking about something similar bump...