Dual impedance handling on cabinets?

tbassist4 · #1 07-27-2010, 01:25 PM

Hey everyone,
I'm starting to look for a new cab to augment my current setup, and I'm finding a lot that say that the impedance is either 4 or 8 Ohms; is there a switch or something? How exactly does this work?

Thanks,
Tyler

mikezimmerman · #2 07-27-2010, 01:27 PM

No, it means that both 8 ohm and 4 ohm versions of the cabinet are available.

Selta · #3 07-27-2010, 01:29 PM

No switch. You'll order a cab and it'll be either 4 or 8 ohms. It's based on the impedance of each speaker and how they are all wired to the jack.

tbassist4 · #4 07-27-2010, 01:30 PM

Ah, I see. Thanks for clearing that up for me - I'm slightly disappointed, haha.

allenhf · #5 07-27-2010, 01:34 PM

Quote:

Originally Posted by Ray Salamon

No switch. You'll order a cab and it'll be either 4 or 8 ohms. It's based on the impedance of each speaker and how they are all wired to the jack.

This is correct, although you can wire a cab to have switchable impedance.

tbassist4 · #6 07-27-2010, 01:49 PM

Quote:

Originally Posted by allenhf

This is correct, although you can wire a cab to have switchable impedance.

How does this work? Isn't the impedance based on the resistance of the physical speakers?

i_got_a_mohawk · #7 07-27-2010, 01:52 PM

Quote:

Originally Posted by tbassist4

How does this work? Isn't the impedance based on the resistance of the physical speakers?

It is.

But, say you have 2x8 ohm speakers.

If you wire them in series, you get a 16 ohm load, if you wire them in parallel you get 4 ohms.

When using 4 speakers in a cabinet, they are usually wired in series/parallel. So, again, say 8 ohm speakers. They'll be wired in pairs that are in series, giving two 16 ohm loads, which is then wired in parallel, giving 8 ohms.

However, you can't get speaker cabinets which will switch from 4 to 8 ohms. There has been one amp manufacturer who claimed to do this, but it was infact nothing more than BS.

BurningSkies · #8 07-27-2010, 01:54 PM

Quote:

Originally Posted by tbassist4

How does this work? Isn't the impedance based on the resistance of the physical speakers?

It is true, but the impedance options may not be the ones you want. ie...you won't have a 4/8 ohm option, but you might have a 16ohm option, etc.

There's one manufacturer who has made a 4/8 ohm switch. Feel free to use the search function to search on Accugroove and Switch and see how that came out.

Derk_Falsco · #9 07-27-2010, 02:26 PM

If you're looking for a 1x12 cabinet, I believe Hartke has or is close to releasing a 1x12 cabinet switchable between 4 and 8 ohms because it uses dual voice coils.

BurningSkies · #10 07-27-2010, 02:28 PM

Quote:

Originally Posted by Derk_Falsco

If you're looking for a 1x12 cabinet, I believe Hartke has or is close to releasing a 1x12 cabinet switchable between 4 and 8 ohms because it uses dual voice coils.

That sounds legit.

tbassist4 · #11 07-27-2010, 05:22 PM

Interesting - that's a bummer that its not really possible. Well, I guess that means I'll be looking for 4 Ohm cabs then. I'm looking for a 4x12" or 1x15", so unfortunately I can't look into that dual voice coil 1x12".

Thanks for all of the information guys,

Tyler

BurningSkies · #12 07-27-2010, 09:13 PM

Quote:

Originally Posted by tbassist4

Interesting - that's a bummer that its not really possible. Well, I guess that means I'll be looking for 4 Ohm cabs then. I'm looking for a 4x12" or 1x15", so unfortunately I can't look into that dual voice coil 1x12".

Thanks for all of the information guys,

Tyler

Why 4ohm cabs only? Its like a straight jacket for future options and the extra wattage you get at 4 isn't really noticeable.

billfitzmaurice · #13 07-28-2010, 06:30 AM

Quote:

Originally Posted by BurningSkies

Feel free to use the search function to search on Accugroove and Switch and see how that came out.

Quote:

Why 4ohm cabs only? Its like a straight jacket for future options and the extra wattage you get at 4 isn't really noticeable.

+1. Bassplayers need to become aware as to what really matters and what doesn't. What really matters is frequency response and driver displacement; what doesn't is watts. The problem lies in that the bass amp industry won't reveal the former, only providing the latter, but they'll only continue to get away with that as long as consumers allow them to.

BurningSkies · #14 07-28-2010, 06:40 AM

Quote:

Originally Posted by billfitzmaurice

+1. Bassplayers need to become aware as to what really matters and what doesn't. What really matters is frequency response and driver displacement; what doesn't is watts. The problem lies in that the bass amp industry won't reveal the former, only providing the latter, but they'll only continue to get away with that as long as consumers allow them to.

I feel like we're sort of 'turning the corner' on this myth on TB...I'm seeing more people recognizing that 4ohm cabs are not the best idea unless you've got a 2ohm capable amp.

12bass · #15 07-28-2010, 07:44 AM

4 ohm cabinets also work well for those with with stereo power amplifiers, like the ShuttleMAX 12.0, SWR SM 900, and Eden WT series heads. Before buying, it is a good idea to know the capabilities of your amplifier.

Bob C · #16 07-28-2010, 07:58 AM

Quote:

Originally Posted by Derk_Falsco

If you're looking for a 1x12 cabinet, I believe Hartke has or is close to releasing a 1x12 cabinet switchable between 4 and 8 ohms because it uses dual voice coils.

Are you serious? One speaker and two voice coils??

ehque · #17 07-28-2010, 08:17 AM

Quote:

Originally Posted by Bob C

Are you serious? One speaker and two voice coils??

It's quite common among car subwoofers, isn't it?

You'll probably have the 4ohm option only using half of the available voice coil, or something like that. Kinda like a coil-tap on a pick up.

Bob C · #18 07-28-2010, 08:20 AM

Okay. I guess I'm ignorant. This will be interesting to follow.

billfitzmaurice · #19 07-28-2010, 09:42 AM

Quote:

Originally Posted by ehque

It's quite common among car subwoofers, isn't it?

It's been common in many woofer/subwoofer drivers for 30 years. JBL Differential Drive pro-sound woofers are one example.

BigOldHarry · #20 07-28-2010, 09:53 AM

Quote:

Originally Posted by BurningSkies

I feel like we're sort of 'turning the corner' on this myth on TB...I'm seeing more people recognizing that 4ohm cabs are not the best idea unless you've got a 2ohm capable amp.

I learned that the hard way years ago.

When I first started out, 30+ years ago, ALL cabs were 8 ohms -- it was just assumed, so most didn't even have it written on the cab... Then Peavey came out with their line of 2ohm rigs...

All I buy is 8 ohm now... Options are good!