Same internal volume, different shaped cab. Will it sound the same?

[Delberthot]

I really like the sound of my Ashdown ABM410 but like most people on here I would like something a bit lighter.

I know that 4 10" speakers arranged vertically will have better dispertion or something like that and that traditional square 4x10"s are a compromise so if I were to take the 4 10" drivers out of my Ashdown cab and build a cab that has them arranged vertically and retains the same internal volume, would it sound better, louder or does the shape of the cab matter?

Just curious cos I can't find anything that I would like to replace it with currently

[Mr. Foxen]

If both all lined correctly it should sound the same. If the original cab isn't, then the internal reflections and such are part of the sound, so a different shaped inside won't sound the same.

[Delberthot]

I hadn't thought about that. Its Ashdown so I doubt its lined.

[Phil Starr]

You'd probably be better off with the speakers in two 2x10's as a vertical 4x10 is just as awkward as a 'normal' 4x10. (PA speakers used to be this shape) Make each one half the original volume.

Keeping them the same volume overall will mean that they will 'load' the speakers in the same way so the bass performance will be similar. If they are ported you will need to recalculate the port sizes but someone here will do that for you.

what will change will be the mids and top. As Mr Foxen has pointed out any change in internal dimensions will change any resonances which will sound a little different, maybe better maybe worse.

What will also change will be dispersion which will change from a narrow cone of upper frequencies to a wide flat fan. this means everyone will hear you a bit more clearly not just the people in line with the speaker. With the current arrangement the radiation from the four speakers are interfering with each other rolling off the upper/mid frequencies so you cab will sound a bit more open and less bass heavy, though there will actually be just as much bass. Finally by having speakers at nearly ear level you will hear yourself more clearly which will sound strange at first but is much better as a musician.

Edited March 10, 2013 by Phil Starr

[Delberthot]

Thanks for that Phil

I've removed one of the drivers to check it and its an Ashdown branded one which is rated 150w @ 8 ohms.

I now have two options:

build a 2x10" cab running at 4 ohms and sit it vertically on a cab stand at ear level

build 2 2x10" cabs running at either 16 or 4 ohms each wired so that when connected together give me 8 ohms.They would be situated on the floor and stacked vertically


Which gives me more questions which may be difficult to answer as I can't find any specs on the drivers:

Should each 2x10" be half the size of the 4x10" or the same size as the 2x10" cab that Ashdown makes given that that cab must either have 4 or 16 ohm drivers fitted which may or may be different?

Will I notice much difference in volume between running a single cab or both together?

Will the ports be the same size and length as in the 4x10" ?

Thanks in advance

[Phil Starr]

if you like the bass tone of the current cab then make two cabs each half the size of the 4x10. The 4x10 may be technically undersized for the speakers (most cheap/mid priced commercial cabs are) so it is possible you could increase the size of the 2x10's. This would in all probability give you a deeper bass response but reduce the hump around 100Hz you probably have now. given that your intention was to have easier to carry cabs and you like the sound I'd go for two half sized cabs.

Yes, you will have to change the ports. If you can get Ashdown to cough them up the Thiele/Small parameters of their drivers would really help us calculate the best size for you.

Just a thought though, If you sell the ABM you could spend that money on some new drivers.

[Musky]

One 210 running at 4 ohms will give you about the same volume as two 210's at 8 ohms combined.

[Delberthot]

I've emailed Ashdown to see if they're willing to give up the speaker specs

I'm giving serious thought to building a vertical 2x10" airhead cab to give me a combo with a view to maybe purchasing an amp that will do 2 ohms and building a second cab using the other two drivers just for the hell of it. Maybe even get one of those Peavey IPR power amps and a preamp

Edited March 12, 2013 by Delberthot

[Phil Starr]

Looks like you are considering spending quite a lot of money and effort on this. I don't know what speakers Ashdown use in the ABM's but the ones in the Mags wouldn't justify this much effort if you are spending £4-500 on an amp and pre-amp. You might want to consider buying better drive units. However if you stick to a fairly normal cab and are prepared to change the ports then you could try out with the Ashdowns and upgrade later.

One of the best lightweight bass drive units around at the moment is the 15" Eminence Kappalite 3015, £200, as used in the barefaced compact (I think) I helped another basschat member with a cab based on this and went to hear him. It sounded fabulous. Don't get hung up on 10's the sound you get is much more dependent upon the actual driver than it's diameter which is only one factor of many.

Edited March 13, 2013 by Phil Starr

[Delberthot]

I enjoy the planning of things like this and don't expect to spend any more than about £40. I've already sourced enough ply to do me for £20 and I plan on using as much of the hardware off the cab as possible.

I'm only going to need more wood glue, t-nuts to mount the speakers, a speakon socket, some dowel to brace it and speaker grill material. I'm not sure whether to tolex it or use some kind of textured paint

[bigjohn]

[quote name='Musky' timestamp='1363041400' post='2007603']
One 210 running at 4 ohms will give you about the same volume as two 210's at 8 ohms combined.
[/quote]

How does that work?

[Musky]

[quote name='bigjohn' timestamp='1363193728' post='2009568']
How does that work?
[/quote]
Doubling the number of speakers (like for like) will give a 3dB increase in volume. Likewise, doubling the power will also give a 3dB increase.

So with an amplifier producing 300w into a 4 ohm load, the single 4 ohm cab will receive the full 300w. With two cabs giving a combined load of 8 ohms the same amp will typically produce about 200w (theoretically amps double their output power when you halve the impedance, but in reality that never happens), so that's a decrease in volume of about 1.7dB - BUT... using twice the number of speakers gives a 3dB increase in volume, so you're left with an overall increase of 1.3dB. Unfortunately 1.3dB is absolutely negligible, so overall you're left with about the same volume.

Edited March 13, 2013 by Musky

[Delberthot]

I've just had a thought:

If I were to recreate a cab of the exact same internal dimensions as the Ashdown ABM210 then I'd expect it to sound pretty close but as I will be bracing the cab should I take the area that the bracing will take up into consideration and make the cab slightly larger based on this?

Bugger, I've just noticed that the ABM210 had a front shelf port - one of them did but there are another two versions that didn't

Edited March 13, 2013 by Delberthot

[Delberthot]

Another thing - if the 4x10" as it is now has 2 ports then should the 2x10 only have one?

[bigjohn]

[quote name='Musky' timestamp='1363199995' post='2009736']
Doubling the number of speakers (like for like) will give a 3dB increase in volume. Likewise, doubling the power will also give a 3dB increase.

So with an amplifier producing 300w into a 4 ohm load, the single 4 ohm cab will receive the full 300w. With two cabs giving a combined load of 8 ohms the same amp will typically produce about 200w (theoretically amps double their output power when you halve the impedance, but in reality that never happens), so that's a decrease in volume of about 1.7dB - BUT... using twice the number of speakers gives a 3dB increase in volume, so you're left with an overall increase of 1.3dB. Unfortunately 1.3dB is absolutely negligible, so overall you're left with about the same volume.
[/quote]

Ah right. To be honest though - when I had 2 2x10s, I rewired them to be 16Ohm, not 4Ohm. I couldn't tell the difference when used separately, despite them drawing only 1/4 of the power (~150W not 600W) - my amp ran A LOT cooler... When both were used together (8Ohm and ~300W) they always sounded much louder regardless...

Edited March 13, 2013 by bigjohn

[Phil Starr]

[quote name='Delberthot' timestamp='1363208450' post='2009942']
Another thing - if the 4x10" as it is now has 2 ports then should the 2x10 only have one?
[/quote]

The short answer is that it doesn't matter. Basically for a given port area the port just balances the mass of air in the port against the air in the cab. At the resonant frequency this mass of air will vibrate and create a note. Tune this to the frequency where the speaker resonates and the extra output from the port makes up for the loss of output from the speaker. (I've simplified this for clarity, some will say over-simplified)

The reason for two ports is that sometimes if you have a big bass output so much air rushes through the port it starts to make a noise you don't want, so you need a bigger port. If that won't fit then two little ports of the same area or a shelf will do the same job.

Any change in the speakers or the volume of the cab will mean you need to completely recalculate the ports. If you can get the Thiele/Small data on your drivers it's a 5min job to do this and you can decide what ports you want within reason.

The bracing will reduce your internal volume but if you are using dowel not by much. I wouldn't worry excessively about this unless you are going to use a lot of material for bracing. A litre of bracing material in a 50l cab isn't going to throw your port tuning out by too much but 10l of bracing would. It would also make each cab nearly as heavy as a 4x10

[Delberthot]

Thanks again Phil.

I did contact Ashdown but they're not responded and really don't expect them to give that sort of data away. Probably get hundreds of emails from crackpots like me every day

I've readvertised the cab for sale to see if someone takes it before I do this. Its such a great, loud cab that I don't want to risk making an ar$e of it.