Help!!! Need advice on cabs and ohms

[AndrewJordan]

[quote name='CamdenRob' timestamp='1463728071' post='3053605']
Don't worry about that... if I thought everything through before posting I'd never post anything...

I notice I've recently passed 4000 posts and at least half of that is nonsense.
[/quote]

LoL! I noticed after making my incorrect post that I am now classed as a "Fully fledged member". Doesn't that translate as "A feathered prick"?

[TimR]

[quote name='BassTractor' timestamp='1463695178' post='3053508']


Aye, you did. But then I didn't state you hadn't done so. I just stated I hadn't seen it.
Sorry for having overlooked it.
[/quote]

I think it's quite an important point really.

Once you double up on cabs you get an increase in bottom end, not necessarily loudness per se.

But how the cabs actually behave can be quite interesting. I put a 15" with 2x10s and it was quieter than the 15" and the 2x10 individually.

I still recommend bin the 4x10 they're heavy and inefficient. Get a 2x10" or a 2x12" and look at postponing.

[Dad3353]

[quote name='TimR' timestamp='1463774484' post='3054049']... I put a 15" with 2x10s and it was quieter than the 15" and the 2x10 individually...
[/quote]

Is that not the typical symptom of the cabs being out of phase..? Was there another explanation, or none at all..?

[Musashimonkey]

[quote name='Dad3353' timestamp='1463780298' post='3054102']


Is that not the typical symptom of the cabs being out of phase..? Was there another explanation, or none at all..?
[/quote]

Amp restrictions with a reduced output at 4 ohm as opposed to 8 maybe?... Or series as opposed to parallel wiring of the drivers?

Edited May 21, 2016 by Musashimonkey

[chris_b]

I've had both Ampeg and Mesa Boogie 115 and 210 rigs and they were very loud.

[Thestonekid]

Picked up the 210 on Thursday and rocked it at rehearsals on Friday.. Certainly a fatter/warrmer overall sound. I'm very pleased with it. And, I didn't have to run the amp as hard either. So, it's a thumbs up. Thanks for advice fellow bassists!!!
Now, I just need to sort out the amp buzz/him but that's another discussion on here. Managed to find a fella who is local so I'm going to call him tomorrow and arrange a service.. I initially thought I had a ground loop issue but it turns out that it could be something else.. We'll see!!!
Ta!

[govons]

Hi Guys,

I need an help to understandi if it is possible to use two cabs with different impedance without problem in head amp.
I summarise situation.

I have one cabinet 2x12 with 4ohm impedance
and
one cabinet 1x12 with 8 ohm impedance.

I have used one by one so far but in case I would like to have a rig with both how to do?
I mean is there any device suggested to put in between cabs or amp that allow to connect both at the same time without any risk to damage head?

[TimR]

You can get dummy speaker loads. A 4ohm one I series with th 4ohm cab.

It's not an ideal situation or solution.

Can you change the speaker in one of the cabs.

[chris_b]

Govons, A 212 at 4 ohm and a 112 at 8 ohm makes a 2.67 ohms load on the amp. This is good as all speakers, each of the 12's, will get the same power from the amp.

If your amp is 4 ohm max then you can't run these 2 cabs. If you like the cabs I'd get a new amp, the Magellan or Mesa D800 will handle 2.67 ohms, then you can run either or both cabs. A good and flexible modular set up. If you like the amp then you need to replace the 212 with an 8 ohm cab.

The suggestion to change a speaker, means you'll have to change the 212 because it will have to become 8 ohm in order to match the 112. That's expensive, might sound bad anyway and will totally change your sound.

One last suggestion. Buy another amp like the one you already have. Run each amp into each cab and daisy chain the amps.

[TimR]

Missed it was a 212.

Run the cabs in series. That'll give you a 12ohm load.

Edited August 1, 2016 by TimR

[govons]

mmmm actually I am satisfied of my rigs... so, I think that best could be use just 212 and in some other case 112.
Thanks

[BassTractor]

This is extremely dependant on which amplifier you use, and that is the info we need from you.
Please tell us exactly which model the amp is, so we know what system it is (tubes or solid state, output transformers or not).

At any rate, the amplifier does NOT "see" two different cabs.
It "sees" three identical elements, with a total impedance of 2.67 Ohm, as Chris says. Experimenting with dummy speaker loads without knowing what you're doing is not what you should do right now. Stay away from those for the time being.

If your amp was built for that 2.67 Ohm impedance, then you're OK:
- Some or many tube amps built for 4 Ohm would accept this lower impedance, but you would have to ask the amp factory first.
- All regular solid state amps without output transformers [b]that are in fact built for 2 Ohm[/b] (and they tell you so on the back of the amp) would accept this higher impedance with gratitude. However, most solid state amps are not built for 2 Ohm.

So, exactly which amp do you use?

[govons]

it is Thunderfunk TFB750A

[chris_b]

The TF750 is a fantastic amp and will run at 2.67 ohms.

I used to run mine with a 212 and 112 when I needed a big sound for my loud bands.

[govons]

yes I know that is great amp, that's why I want to keep it. It would be nice to use both cab but I do not want to risk, so I prefer to be safe if there is nothing to insert as a protection

[BassTractor]

[quote name='govons' timestamp='1470054832' post='3102918']
yes I know that is great amp, that's why I want to keep it. It would be nice to use both cab but I do not want to risk, so I prefer to be safe if there is nothing to insert as a protection
[/quote]

Chris just told you that it WILL run at a 2.67 Ohm load (unlike the TFB550).
You do not need any protection. In fact, adding what you think is protection will probably be adding a risk because you do not know what you're doing.
If your cabs have the same drivers, then connecting both cabs is one of the best things you can do. As I wrote: the amp "sees" three identical drivers, which is good.

The official specification of the TFB750-A - - - and this is written in its user manual, which you should have downloaded - - - is that it delivers 750W into a 2 Ohm load, 630W into a 4 Ohm load and 305W into an 8 Ohm load.
As this amp has output transistors (not an output transformer) and can deliver into a 2 Ohm load, it will happily relax with a 2.67 Ohm load.
User manual: [url="http://www.thunderfunk.com/Downloads/Thunderfunk_OwnersManual.pdf"]http://www.thunderfu...wnersManual.pdf[/url]

[govons]

[quote name='BassTractor' timestamp='1470137697' post='3103476']
Chris just told you that it WILL run at a 2.67 Ohm load (unlike the TFB550).
You do not need any protection. In fact, adding what you think is protection will probably be adding a risk because you do not know what you're doing.
If your cabs have the same drivers, then connecting both cabs is one of the best things you can do. As I wrote: the amp "sees" three identical drivers, which is good.

The official specification of the TFB750-A - - - and this is written in its user manual, which you should have downloaded - - - is that it delivers 750W into a 2 Ohm load, 630W into a 4 Ohm load and 305W into an 8 Ohm load.
As this amp has output transistors (not an output transformer) and can deliver into a 2 Ohm load, it will happily relax with a 2.67 Ohm load.
User manual: [url="http://www.thunderfunk.com/Downloads/Thunderfunk_OwnersManual.pdf"]http://www.thunderfu...wnersManual.pdf[/url]
[/quote]

thanks for the advise, I will follow it. Cabs are bergantino cn212 and cn112

[Froggy]

Sorry to hijack the thread a bit, but I've j7st bought a couple of cabs and a head from a mate who lost his senses and has decided after many years of bass, that he's enjoying playing guitar more! Foolish boy!

Anyway, I just wanted to check that I had it set up right.

Head is a Hartke HA3500 and cabs are a Hartke TP410 and Hartke TP115

The head has 2 x 8 ohm outputs, each of which is plugged into the 8ohm input on the cabs. I'm guessing that's correct?

I really should get on the Hartke website and download the manuals.

[BassTractor]

[quote name='Froggy' timestamp='1470162307' post='3103767']
Head is a Hartke HA3500 and cabs are a Hartke TP410 and Hartke TP115

The head has 2 x 8 ohm outputs, each of which is plugged into the 8ohm input on the cabs. I'm guessing that's correct?
[/quote]

Yes.
Both 115TP and 410TP are 8 Ohm cabs, and the HA3500 will deliver to the 4 Ohm result load of connecting two 8 Ohm cabs.

Though: I'd bet a considerably substantial amount plus huge parts of my life on the outputs being wired in parallel, as in coming from one source only (as opposed to bi-amping).
In case you can just connect the first cab to the amp and the second cab to the first cab, which seems a little neater to me. I believe this is what you English lot call "daisy chaining".
Happy to be corrected on this, after which all bets are off.

[tauzero]

There are a couple of teeny-tiny advantages to wiring separately to the cabs rather than daisy-chaining.

1) If one speaker lead fails (unlikely) then it's a 50-50 chance whether both speakers will fall silent if you're daisy-chaining

2) The signal to the second cab will pass through two sets of connectors unnecessarily, which could add a little extra resistance to the signal path

Certainly not enough to put me off daisy-chaining when I need to (like with my amp, which has a single output which is daisy-chained to two cabs) but if I was running an amp with two outputs, I'd run one to each cab. It's also one fewer Speakon to furtle around with behind the cabs and one more in the more accessible area behind the amp.