Speakers "ohms" HELP

[shell_shooter]

My question is can you miss match speakers in a 412 cab I asume that the ohms have to be the same but what about wattage is there a web site to get some speakers and cab knowledge

[lonewolf]

Mixing 2 pairs of speakers with different power ratings is not a problem.

In a 4x12 mono cabinet, the cabinet power is equal to 4 times the power rating of the lowest rated speaker.

I don't recommend mixing more than 2 types of speakers in a 4x12 cab because...

When you mix 2 + 2, put one type across the bottom and one type across the top. This is so like speakers are in the same plane. When like speakers are in the same plane + parallel to the floor, acoustic coupling is maximized and they will produce more bass--theoretically twice as much.

The other thing you want to look out for is speaker sensitivity. That measures how loud a speaker gets for a given power. The sensitivity of most 12" guitar speakers is rated between 95db - 102db @ 1watt, 1meter. A difference of only 3db between speaker models means that one model is twice as loud as the other. I wouldn't match up speakers that are more than 2db apart in sensitivity in a closed-back cabinet.

[The Shadow]

I agree with lonewolf on everything but the 2 similar on top and 2 similar on the bottom. If you do two different speakers like lets say 2 Vintage 30's and two G-12H 30's put them in an X pattern.


V-30 G12H30


G12H30 V-30

[lonewolf]

I agree with lonewolf on everything but the 2 similar on top and 2 similar on the bottom. If you do two different speakers like lets say 2 Vintage 30's and two G-12H 30's put them in an X pattern.


V-30 G12H30


G12H30 V-30

It won't make much difference with a straight cab. but you will lose a lot of potential bass response on an angled cab with that config.

The final factor, though: if it sounds good, do it.

[shell_shooter]

Thanks for your help "the ohms do need to be the same then right"

[JackANSI]

Speakers with lower ohms will be 'louder' or at least get more of the available power, take that into consideration.

Other resources:

The best load calulator out there, IMO:

http://www.colomar.com/Shavano/impedance_proc.php

http://www.colomar.com/Shavano/spkr_wiring.html

[lonewolf]

Thanks for your help "the ohms do need to be the same then right"

Yep--in 99.99% of cabs, the speakers should all be the same impedance. You want to check your amp's power output to find out the "minimum load impedance" in ohms. If you have a tube amp, there is usually a switch or a choice of output jacks marked to match the power amp output to the speaker cabinet ohms.

I have found that 8 ohms is usually the best guitar cabinet impedance because it matches up with the most different amps. Its also a good bet when bridging a solid state power amp. Many will bridge to 4 ohms, but the amp will run cooler at 8ohms and you usually don't need the extra power for guitar.

16 ohm cabinets are good with certain amps like old Marshalls and also when you are using two cabinets. Two 16 ohm cabinets makes an 8 ohm load.

In a 4x12 cabinet wired series/parallel, the cabinet impedance will be the same as the individual speaker impedances in ohms. So, for an 8 ohm cabinet, you need four 8 ohm speakers.

[hicksjd9]

You can get away with different impedances of speakers if you have no other choice, but I wouldn't have more than two different impedences in one cab.

Series and parallel wiring work like this:

Parallel divides the impedence in half, meaning if you wire two 8 ohm speakers in parallel, they show a 4 ohm load.

Series wiring doubles the impedence or ohm load. For instance, those same two 8 ohm speakers wired in series would show a 16 ohm load.

Most speaker cabs have 4 16 ohm speakers. The two 16 ohm speakers on each side are wired in parallel, which means each side (set of two speakers) shows an 8 ohm load. On marshall cabs, you can have a stereo connection that is set up this way. You can also select 4 ohms on the cab because the selector switch connects the two sets of two speakers (each set shows 8 ohms) in parallel again. This will show a 4 ohm load to your amp. The 16 ohm switch changes the connection to a series wiring. This takes each 8 ohm load showing set of two speakers and wires them in series doubling the impedance to 16 ohms.

If you have a pair of 8 ohm speakers and a pair of 16 ohm speakers and you want to combine them you can. Try wiring each set in parallel. Your 8 ohm set will now show 4 ohms and your 16 set will show 8 ohms. Take your 4 and 8 ohm pairs of speakers and wire them in series which will double your impedance which will basically give you a 12 ohm load and run into your amp at the 8 ohm connection and you will be fine. Weird impedances (anything other than 4, 8, and 16) aren't the best, but they won't likely hurt something as robust as a tube amp.

Please note:
You are fine to run you amp at a lower impedance than your speakers, but NEVER run your speakers at a lower impedance than your amp can handle. For example, a 16 ohm set of speakers is safe to run through the 4 ohm jack on your amp; however, a 4 ohm set of speakers will set fire to you amplifier if you plug them into the 16 ohm jack. Remember MORE resistance (higher number of ohms) is easier on your amp, but not as loud. LESS resistance (ohms) is louder, but is MUCH harder on your amplifier (causes it to get overheat, etc.) Just make sure your amp can handle a 4 ohm load and you should be fine, but NEVER run a load less than 4 ohms through a guitar amp. You will fry it eventually.

[shell_shooter]

I am running a Crate blue VooDoo 120 ..I have a 2x12 cab at 16 ohms and a 4x12 at 16 ohms is it safe to run both of them as a 3/4 stack

[hicksjd9]

Yes. Depending on how they are wired, you will either have 32 or 8 ohms. Either way, you are good. My guess is that it will be 8 ohms if one of your cabs has two jacks on it (one in, one out). Your amp may also have dual output jacks (many ampeg bass amps are this way, so I see this as a possibility on a guitar amp) in that case, the cabs would definitely run at 8 ohms. It's hard to explain all the things it could be without writing a book. Suffice to say that if your amp has an 8 ohm output jack you would go out from that, into cab 1, out of cab 1 (if it has an output) and into the input of cab 2. This would show the amp an 8 ohm load as long as you are SURE both cabs are rated at 16 ohms. It's a little odd for a cab to be rated at 16 ohms as its only option, but if there is a switch, definitely make sure that it is set to 16 ohms for each cab. This is essential.

[lonewolf]

If you have a pair of 8 ohm speakers and a pair of 16 ohm speakers and you want to combine them you can. Try wiring each set in parallel. Your 8 ohm set will now show 4 ohms and your 16 set will show 8 ohms. Take your 4 and 8 ohm pairs of speakers and wire them in series which will double your impedance which will basically give you a 12 ohm load and run into your amp at the 8 ohm connection and you will be fine. Weird impedances (anything other than 4, 8, and 16) aren't the best, but they won't likely hurt something as robust as a tube amp.

When you do this, each 8 ohm speaker will use 1/3 of the power and each 16 ohm speaker will use 1/6 of the power. If all the speakers have roughly the same characteristics, the 8 ohm speakers will be twice as loud as the 16 ohm speakers.

The only way I would do something like this is if the 16 ohm speakers are at least 3db higher in sensitivity (louder per watt) than the 8 ohm speakers. That would even up the speaker loudness. That is an example of the other 0.001% of cabinets that I was talking about in the earlier post.

[shell_shooter]

yes my amp has duel output and its 8 ohm or 16 ohms the 412 cab has 4 ohms on mono,8 ohms stereo,16 ohms mono the 212 is a project i have not wired it yet i have 2 16 ohm speakers. thats what i thinking

Thanks again for all your help i am just ring to see how this works and what will work