Daisy chaining cabs with different ohms & cones

[Al Krow]

Bit of a newbie question but...

My amp has just got a single output, which can be set to a minimum load of either 4ohms or 2ohms.

I've currently got a 4ohm 2x10 cab but am thinking of adding a 115+6 cab to it; the one that has come up for sale is rated 8ohm.

If I daisy chain the two cabs am I going to end up with a 12ohm load (i.e. the cabs in series) or will they automatically be in parallel and I'll end up with 2.67ohms (applying the formula 1/R_T = 1/R₁ + 1/R₂)?

Edited November 1, 2018 by Al Krow

[obbm]

When you daisy chain cabinets you are actually putting the two sets of speakers in parallel, not in series.  Daisy chaining an 8-ohm cab with your existing 4-ohm cab will give a combined impedance of 2.67-ohms.  It is possible to make a special cable to put the two cabs in series which would give you an impedance of 12-ohms.

[Al Krow]

1 minute ago, obbm said:

When you daisy chain cabinets you are actually putting the two sets of speakers in parallel, not in series.  Daisy chaining an 8-ohm cab with your existing 4-ohm cab will give a combined impedance of 2.67-ohms.  It is possible to make a special cable to put the two cabs in series which would give you an impedance of 12-ohms.

Perfect, thank you! That's what I was hoping you were going to say (although it does mean you've taken away any last semblance of an excuse for not going ahead with the purchase 😀)

Increasing the load to 12ohms in series would have been pants, but at 2.67ohm I can simply set my amp to "min 2ohm" mode and let it rip.

[obbm]

Depending on the sensitivities of each cab and the internal configurations you may find that one cab is louder than the other.

 

[Steve Browning]

28 minutes ago, obbm said:

Depending on the sensitivities of each cab and the internal configurations you may find that one cab is louder than the other.

 

So, to paraphrase Father Ted, put the louder one further away. 🙂

[Al Krow]

20 minutes ago, Steve Browning said:

So, to paraphrase Father Ted, put the louder one further away. 🙂

Well if I set them up as a stack, I'm planning on the 15+6 (8ohm) going on the bottom with the 210 (4ohm) on top, just 'cos that makes sense from speaker cone size I would have thought?

I presume that the 210 with the lower resistance is going to be louder and and also closer to my ear level, but that's fine as it will be the more "articulate / tighter" bass sound; whereas the audience are going to get a bit more from the 15" given that larger amplitude sound waves tend to travel further / attenuate less quickly; so from an audience perspective it should all balance out nicely?

[chris_b]

As OBBM says, if you are running an 8 ohm cab and a 4 ohm cab together you will want an amp that can deliver 2.67 ohms. The 4 ohm cab will receive 66% of the volume and the 8 ohm cab will receive 33% of the volume from the amp.

[Japhet]

I've never liked the idea of running cabs with different Ohms together. Everything (power consumption, output, volume) would seem to be out of balance. Just doesn't seem right to me.

[Al Krow]

9 minutes ago, chris_b said:

As OBBM says, if you are running an 8 ohm cab and a 4 ohm cab together you will want an amp that can deliver 2.67 ohms. 

Chris I should be ok in terms of the amp as my amp can cope with a minimum 2 ohm load.

11 minutes ago, chris_b said:

The 4 ohm cab will receive 66% of the volume and the 8 ohm cab will receive 33% of the volume from the amp.

1 minute ago, Japhet said:

I've never liked the idea of running cabs with different Ohms together. Everything (power consumption, output, volume) would seem to be out of balance. Just doesn't seem right to me.

Hmmm, that's actually quite a big differential if the 210 is getting twice the power of the 115+6;

And actually that's the wrong way around - as the low frequencies which the 115 should be better at pumping out** require more power than the mid / higher frequencies.

Has definitely got me rethinking; I'd definitely be better placed getting a 4ohm VK156 so both cabs have the same ohms, but in terms of used cabs they're a bit like hen's teeth! Maybe a case of getting what's available now and "make do and mend" and then swapping out the 156 8ohm for a 4 ohm as / when one eventually becomes available?...I'd certainly like to keep hold of my 4ohm 210 (rather than swap that out for an 8ohm) as that is great as a stand-alone cab and allows me to access the full headroom from the amp.

Or maybe best to just bite the bullet and realise I'm going to have buy a new VK156 4ohm if I want this particular set up to work to its full potential.

**I know some folk argue that speaker size does not impact frequency handling. Well if that were true then a 5" speaker should be able to match an 18" speaker no problem. But we all know that's rubbish, so clearly there is a gradation here, right?

[chris_b]

What do you think the 15 will give you that another 210 won't?

I replaced a Mesa Boogie 210 and 115 with EV's with an Epifani 410 and got a sound with twice the amount of low end. Because that was the way those cabs were designed. I then replaced the 410 with 2 Berg 112's and reduced the low end but got a much better and balanced sound across the whole range.

So size really doesn't matter. It really doesn't. The sound of the cab is the only thing that matters and ears are much better than spreadsheets for working that one out.

[Al Krow]

3 minutes ago, chris_b said:

What do you think the 15 will give you that another 210 won't?

In short, better lows.

But is it really the case that larger speaker cone size makes no difference whatsoever, other things being equal?

It's very much my point about: "Well if that were true then a 5" speaker should be able to match an 18" speaker no problem. But we all know that's rubbish, so clearly there is a gradation here, right?"

[itu]

Although the power is split to two cabs 33/66 %, the amount of sound (SPL) is not so simple. If you know the sensitivity of the cabs, you can have a more accurate guess of the volume you get from each other.

Very, very often this SPL (the actual dBs) is put aside and people look only at power (W). Wattage may give you an idea of loudness but is not exactly telling you anything about perceived loudness.

[Bill Fitzmaurice]

26 minutes ago, Al Krow said:

It's very much my point about: "Well if that were true then a 5" speaker should be able to match an 18" speaker no problem. But we all know that's rubbish, so clearly there is a gradation here, right?"

Beware of what 'we all know', as it's as likely as not incorrect. One can find, without too much searching, a five and an eighteen that go equally low. Where the five would come up short is in maximum output. A 115 may give better lows than a 210, it may not. My advice in this respect is always the same: if you don't like the sound of your speaker get one that you do like the sound of. If one isn't loud enough get two.

[chris_b]

Yes, the SPL is the thing to balance out. People get confused when a Barefaced cab can have the same SPL as an SVT810. One's bigger with more drivers so it must be louder?! Right?!!

The sound of a cab is determined by the design of the driver and the design of the cab, not the size of the driver. There are a lot of parameters that beat driver size before you arrive at the sound of a particular cab.

[itu]

2 minutes ago, Al Krow said:

In short, better lows..."Well if that were true then a 5" speaker should be able to match an 18" speaker no problem. But we all know that's rubbish, so clearly there is a gradation here, right?"

If you take an example from hifi, you know that you can go really low with good design of the box, the cross over and the elements. But there are three things that go hand in hand. Let us start with basics.

A speaker may be efficient.

A speaker may go really low.

A speaker may be small.

After these three, the speaker may also have a flat frequency response.

 

First of all, a very efficient speaker has very limited frequency response. PA (read: bass) systems tend not to be very flat. But they are efficient!

If a speaker needs to go down low, there are these two other parameters that affect the overall performance: the volume of the box and the efficiency. So you can go really low with the same box (volume kept as is) if you just sacrifice efficiency. And vice versa, you can get good lows at high SPL but you need to make the box far bigger. This is plain physics.

Hifi guys know, that flat response equals lots of equalizing (through cross over) of the system, which means that the efficiency is sacrificed. And because of size (or design or...) issues, hifi speakers tend to be pretty small and the efficiency is even worse. PA speaker may have the efficiency at a level of 1 - 2 % whereas a hifi speaker at around 0.01 - 0.1 %, which is 10 - 200 times less.

 

One side note: If you think about this modern FRFR jargon, I have to be a bit sceptical. Full frequency AND flat response equals hifi and that is not efficient at all. It requires quite some more power than ordinary PA systems. If a basic modern bass amp has 500 W, who sells these amps with huge power reserve (kilowatts!) and who has those real FRFR speaker systems? How much would they cost and are they really needed - a magnetic pick-up bass has a limited frequency response, too.

[Al Krow]

1 hour ago, Bill Fitzmaurice said:

One can find, without too much searching, a five and an eighteen that go equally low. 

Where the five would come up short is in maximum output.

I'm really struggling to agree with the remarks that speaker cone size makes no difference regarding audible low frequency handling.

We obviously want ability to go low and provide sufficient maximum output, the two go hand in hand. There's no point a 5" speaker producing a low E and no one able to hear it, is there?

Indeed when dealing with the lower frequencies, we need greater power output for those low frequencies to be "heard at equal volumes" to the mids / treble end; it's the way our ears and hearing are attenuated. 

So comparing apples with apples please (anyone) come up with an example from the same manufacturer where a single 5" speaker is comparable to a single 18" in delivering great low frequencies? I just don't think there is even one example which exists and so I get back to my point that there is a gradation. 

 

[Bill Fitzmaurice]

Obviously one would not expect a five to equal the output of an eighteen, but a grouping of fives would. What determines a drivers low frequency response is the Theile/Small specs. Cone area (Sd) is only one of some fourteen T/S specs, and of those specs Sd has no influence on how low a driver can go. That is primarily the result of the driver Fs, Vas and Qts.

Edited October 29, 2018 by Bill Fitzmaurice

[LukeFRC]

1 hour ago, Al Krow said:

I'm really struggling to agree with the remarks that speaker cone size makes no difference regarding audible low frequency handling.

We obviously want ability to go low and provide sufficient maximum output, the two go hand in hand. There's no point a 5" speaker producing a low E and no one able to hear it, is there?

Indeed when dealing with the lower frequencies, we need greater power output for those low frequencies to be "heard at equal volumes" to the mids / treble end; it's the way our ears and hearing are attenuated. 

So comparing apples with apples please (anyone) come up with an example from the same manufacturer where a single 5" speaker is comparable to a single 18" in delivering great low frequencies? I just don't think there is even one example which exists and so I get back to my point that there is a gradation. 

 

I have some in ear monitors - I have no idea the size of the bass driver but it would be measurable in mm not inches... but it goes plenty low enough for what it’s designed for. The point is the whole “what it’s designed for” ... 

[Al Krow]

10 minutes ago, LukeFRC said:

I have some in ear monitors - I have no idea the size of the bass driver but it would be measurable in mm not inches... but it goes plenty low enough for what it’s designed for. The point is the whole “what it’s designed for” ... 

Valid point, but on the other hand not entirely relevant to a bass player in a band mix e.g. if you played your bass through your in ear monitors I suspect your audience would struggle a tiny bit to hear you 😜

There's a reason that cab manufacturers have landed on 10" and 12" speakers as generally providing the best "platform" overall, and that woofers tend to be 15" or larger. 

[LukeFRC]

43 minutes ago, Al Krow said:

Valid point, but on the other hand not entirely relevant to a bass player in a band mix e.g. if you played your bass through your in ear monitors I suspect your audience would struggle a tiny bit to hear you 😜

There's a reason that cab manufacturers have landed on 10" and 12" speakers as generally providing the best "platform" overall, and that woofers tend to be 15" or larger. 

I often do ... and DI into the front of house - much better way of getting good sound! 😃

[jrixn1]

57 minutes ago, Al Krow said:

There's a reason that cab manufacturers have landed on 10" and 12" speakers as generally providing the best "platform" overall, and that woofers tend to be 15" or larger. 

I've never used one, but Phil Jones Piranha 8x5 exists.

https://www.thomann.de/gb/phil_jones_piranha_compact_8_cabinet.htm

Quote

Power rating: 800 Watt
Frequency range: 25 Hz - 15,000 kHz

 

[Al Krow]

17 minutes ago, jrixn1 said:

I've never used one, but Phil Jones Piranha 8x5 exists.

https://www.thomann.de/gb/phil_jones_piranha_compact_8_cabinet.htm
 

Thanks John. Yes for sure, EIGHT x 5".

I'm being told size doesn't matter. So I'm saying put a SINGLE 5" against an 18" (or 15") and see how they compare. They don't. 

I guess what folk are saying is that you can get small speakers to deal with low frequencies (agreed), but the smaller the speaker size the more you're going to need to deliver the volume, and so we're probably at slightly cross purposes.

It's the combination of volume and frequency response i.e. being able to hear those lows that the speaker is putting out.

I think this particular point has probably run it's course! 😀

Edited October 29, 2018 by Al Krow

[LukeFRC]

3 minutes ago, Al Krow said:

Yes for sure, EIGHT x 5"

I'm being told size doesn't matter. So I'm saying put a SINGLE 5" against an 18" (or 15") and see how they compare. They don't. 

You’re not being told that size doesn’t matter, you’re being told that there isn’t a link between size and frequency response. 

[Al Krow]

2 minutes ago, LukeFRC said:

You’re not being told that size doesn’t matter, you’re being told that there isn’t a link between size and frequency response. 

Cheers Luke, if that's the message then I'm fully on board with that  

[Bill Fitzmaurice]

+1, and the pertinence goes back to where the OP stated his reasoning behind wanting to add a 115 to a 210 is to get better lows. That assumption isn't supported by the facts.