Speaker sizing when using a combo with an extension cab

[Bassybert]

Hi all, I've always had a head and separate cab setup so haven't run into this before, but I have an Ashdown ABM 300w combo with built in 15" speaker and wondered if I added an extension cab at a later date are there any hard fast rules?

 

I understand that a speaker's size doesn't necessarily dictate how much bass/air it moves, but could I add something like a 2x10, a 1x12, 2x12 or 1x15 etc without any worries such as comb filtering as there's no horn/tweeter on the combo.

 

Also, the combo has a slit port across the whole width along the bottom, I presume it would still work as intended if the combo was sat on top of an extension speaker, or would I need to put the extension on top of the combo?

 

Cheers

Edited February 9, 2023 by Bassybert

[Bill Fitzmaurice]

You'll get the best result with another cab loaded with the exact same driver. Otherwise you're creating a chain with a weak link. Comb filtering has nothing to do with the driver sizes. It happens in the highs when drivers are placed side by side. Doing so also halves the horizontal dispersion in the mids compared to a single driver, or multiple drivers vertically stacked.

[chris_b]

I'd suggest the matching Ashdown extension cab.

[DGBass]

If its the front ported ABM 1x15 wide combo then its probably an older version, maybe an abm 300/300 evo or evo 300. ABM combos were rear ported from evoII on. Ideally as has been said, a matching ashdowm cab of the same vintage would be ideal as it would hopefully contain the same ( blue line sica ?) driver in it. Some of the early combos had Celestions or Eminence as well with the black cone. MAG deep cabs like the 2x10 and 115 are also a good match as they usually had the same drivers in them if its blue lines. The Mag cabs are the same width as well so stacking one under your combo wouldn't look out of place. Stacking on top of wide ABM combos is probably not a good long term propostion as that thin plank on the top is strong enough to hold a long chassis ABM but not much more. I always say if you can't stand on top of a cab/combo without any cracking or splintering sounds, you shouldn't stack on top of it 😆 Assuming a regular sized dude is doing the standing on top. A lightweight 2x10 or similar might not be so bad but if its not Ashdown then you might fall foul of different speaker efficiences where one or the other will be lost or dominate in the mix. And it will look odd. 

One situation where a mix and match might not be so crucial is if you just want an extension monitor cab at the side of the stage or in front of you. Any old tilt back cab might then be a useable proposition.

[Bassybert]

Thanks for the replies everyone much appreciated. 
 

@DGBass I think it is one of the blue line sica drivers, has an almost cloth like feel to the blue cone. I might remove to have a look at the back of it but no fuss at the moment. 
 

I would much rather have the combo on top of an extension speaker than the other way round so good to hear that, I was just wondering if the slot port needed to be near to the floor that’s all.

[Bill Fitzmaurice]

It doesn't. But the extension should be ported as well in any event.

[NancyJohnson]

I ran an Ashdown MAG combo years ago, it was a 2x10 model; I ran several different MAG cabinets as extensions.  1x15, 4x10 and 2x10.  

 

They all worked fine...I think the 1x15 was the more pleasing of the bunch; it just gave me a bit more wobble.

 

We get too hung up on what'll work with what; gear nowadays is pretty robust and in truth it's probably quite difficult to break.  40 years playing, never experienced anything major.

[BigRedX]

If the bass goes through the PA then it really doesn't matter what cabs you use, as they will make zero contribution to what the audience hears; and depending on the size of the stage and what the rest of the band have in the foldback, their effectiveness as personal monitors may not be that great either. Pick something that fits the image of the band and/or genre of the music and be done with it.

 

If you rig is 100% responsible for what the audience hears then the choice of cabs is more important. It's a fact that identical cabs should give you a more consistent sound throughout the venue. It's essential to remember that if you do mix different cabs, what sounds great to you on stage may have turned your tone into something entirely different in various parts of the venue.

[Bill Fitzmaurice]

1 hour ago, BigRedX said:

It's a fact that identical cabs should give you a more consistent sound throughout the venue.

Far more often than not that's true. You can combine just about any two cabs and they'll sound better than either one on its own. That's because the two will be louder than one at the same amp setting, and louder is subjectively better. However, the only way one can know if X+Y works better than, or even as well as, X+X or Y+Y, is to try all three combinations side by side. In some twenty-five years of seeing these discussions I can't recall a single instance where someone actually did so.