Would you wire your 16 ohm series 2x12 8 ohm parallel to match your 8 ohm 4x12?

[eeddings]

I have a 2x12 combo amp that is 16 ohm -- two 8 ohm speakers wired in series for 16 ohm. The stock speakers don't sound all that great to me.. The combo amp has an option to do 4 ohm, 8 ohm, or 16 ohm via a switch on the back.

 

I have a 4x12 cabinet that is 8 ohm. The combo amp sounds amazing through it. I flip the switch on the back of the combo to 8 ohm, disconnect the internal 2x12 speakers, and run the loudspeaker out to the 4x12. Beautiful.

 

I'm considering swapping the two 8 ohm speakers in the 2x12 combo with two 16 ohm speakers and running the 2x12 combo 8 ohms so I can run both the combo and the 4x12 in stereo.

 

I should also mention that I already have a Celestion GT12T-75 16 ohm sitting here from an old 90's JCM cabinet. It is one of the Made in Ipswitch speakers, 16 ohm, and well broken in. I'm considering pairing it with a 16 ohm V30 or other speaker and running the 2x12 8 ohm.

 

Any thoughts, considerations, pitfalls, warnings, or general feedback greatly appreciated!

 

Thanks in advance!

[t_e_l_e]

first running two speakers with the same signal of the same output of an amp is not stereo, its just more speakers playing the same mono signal.

 

disconnecting the internal speaker while an external cab is connected, is on purpose, as it seems, the amp circuit is not supposed the run on two speakers at the same time.

one reason could be that if both speakers run parallel, internally it would be a wired like parallel and of two 8ohm speakers it would make one 4ohm speaker from the amp output point of view, which it might not be able to handle. vice versa it could treat them as in series, it would make a 16ohm speaker (or 32ohm depending what you add) which the amp might not like either....

 

what options you really have, and if internal rewiring of the switch is needed or even possible depends fairly on the amp what it is.

so telling us the make and modell would be really of much help

 

if you having a link to the schematics would be the greatest thing ever

[WRGKMC]

If the amp has a 4 ohm setting, you might want to try the speakers wired in Parallel for 4 ohms. Be sure the positive and negative terminals are linked together Tip> both (+) terminals, Sleeve> Both (-) terminals.

 

In series like you have them now, the wires should run Tip>(+)>(-)>(+)>(-)>Sleeve

 

If you do get some more speakers and want to match it to your 4X12" then you would need to use a pair of 16 ohm in parallel or 4 ohm in series to come up with 8 ohms.

 

You may want to see what kind of speakers you have in your 4X12 cab and match them. This way the combo speakers wont be louder then the 4X12" or vice versa. If you cant get an exact match you may be able to match the SPL level of the speakers and then just get whatever you want. The SPL rating in decibels is the key to having loudness matching. The higher the number the louder the speaker for a given wattage.

 

Frequency response chart will tell you what kind of frequencies they produce. You can use it as a guide to help you find the right speakers you want. A 4X12 cab will have more bass then say a 2X12 open backed cab even if the speakers are identical. The right speakers in the 2X12 can add to what the 4X12 produces. Just be sure they sound good as a combo only so you can use the amp solo and still sound good.

 

Just try and figure out what the amp lacks as is and you can compare frequency charts and match the SPL levels between the two cabs and you should be good.

[DeepEnd]

. . . You may want to see what kind of speakers you have in your 4X12 cab and match them. . . .

 

. . . Just try and figure out what the amp lacks as is and you can compare frequency charts and match the SPL levels between the two cabs and you should be good.

^ This would be my advice too. Apparently there's something about the speakers in the external cab that you like. Try to find the same or similar speakers (i.e., Celestion model XXX, Eminence model YYY, Jensen model ZZZ, what-have-you) and put them in your amp. You may find you don't need to run the external cab. As for running the Celestion GT12T-75 with a Vintage 30, the Vintage 30 will have a tad more bass and be about 3dB louder, and nominally handle 15 fewer Watts. Not saying you won't like the result but be advised. The Seventy 80 is a closer match if you don't want to get another GT12T-75 for whatever reason: http://celestion.com/product/22/seventy_80/. Check the specs and try to match the speakers as well as you can.

[eeddings]

Hi Guys, thanks for the comments and responses. I very much appreciate your expert tutelage!

 

I've been referencing this image:

 

 

Currently the combo is wired as the top, in series. I'm considering putting the 16 ohm Celestion G12T-75 I currently own and possibly a 16 ohm V30 in the cabinet and wiring it parallel, which looks easy enough to do. Then, I could leave the switch on the back of my combo amp in the 8 ohm setting and run both the combo amp's 2x12 speakers and the 4x12 8 ohm, if I understand these things correctly.

 

The 4x12 is a Marshall 8412 with four factory Celestion G12L-35 speakers.

 

My combo amp model I'm reluctant to post as I expect I'll get ridiculed.

 

So, would there be any reason not to wire the combo 2x12 amp parallel with two 16 ohm speakers, given that the amp has a switch on the back to go from 4 to 8 to 16 ohms?

 

Thanks for your keen insight!

[eeddings]

^ This would be my advice too. Apparently there's something about the speakers in the external cab that you like. Try to find the same or similar speakers (i.e., Celestion model XXX, Eminence model YYY, Jensen model ZZZ, what-have-you) and put them in your amp. You may find you don't need to run the external cab. As for running the Celestion GT12T-75 with a Vintage 30, the Vintage 30 will have a tad more bass and be about 3dB louder, and nominally handle 15 fewer Watts. Not saying you won't like the result but be advised. The Seventy 80 is a closer match if you don't want to get another GT12T-75 for whatever reason: http://celestion.com/product/22/seventy_80/. Check the specs and try to match the speakers as well as you can.

 

 

Thanks for this advice. I can't put the exact same 35 watt speakers that are in the 4x12 in my 2x12 combo because the combo amp is rated 120 watts. So, I really need to put in 65-75 watt or higher speakers. Currently the amp has 75-watt speakers.

 

I could be liking the 4x12 so much also because the speakers are well broken in compared to the combo amp which is new.

 

Your Seventy 80 suggestion sounds interesting -- thanks for this! I'll do some research. Or maybe the answer is just to get another G12T-75. I've just read over and over how much people like combininb the G12T-75 with the V30, but maybe that's just in a 4x12 and not so much in a 2x12. I've read some opinions about the match in a 2x12 and results are mixed.

 

 

[t_e_l_e]

My combo amp model I'm reluctant to post as I expect I'll get ridiculed.

 

without telling which amp it is, we can only be limited helpfull. so my advice here is, replace the iternal speakers only with ones with the exact same ohm rating and minimum the same wattage or more. and do not change the wiring, cause obviously you don't know what you are doing and that's dangerous

 

if an amp can handle a higher resistance speaker or lower or two "cabs" in parallel/series what ever, is depending on a lot of things. is it a tube or solid state amp? if tube, which output ohm does the output transformer support, and these have to match otherwise you damage the amp. if solid state, the resistance never should be lower as stated, otherwise it will draw too much current and it also can cause serious damage. how is the mysterious switch on the back wired? does it only support internal or external speaker choice, or are there positions which support both? the wiring and the schematic of the power amplifier section is here important.

 

without knowing any of these things, doing any changes to the existing amp can seriously harm the amp and yourself and can set your house on fire.

 

PS: everyone of us had at least one ridiculous amp in our history, but at the time it was mostly the only thing we could get and/or afford. my first amp, which was a birthday present and so i still have it for sentimental reasons, was a Park (son of Marshall ) G10... man, chainsaw massacre describes the annoying sound of it in the most friendliest way

[eeddings]

That makes sense, tele. This is the kind of information I was seeking. Thanks for taking the time to respond. At the risk of ridicule and/or you guys ceasing to share your knowledge with me, I'll let the cat out of the bag. It's a Bugera 333XL-Infinium 212. It's tube. It really amazes me just how much I like it. My 100-watt Marshall hasn't been turned on since I got this Bugera.

[t_e_l_e]

hm not much info around this amp, the manual is very limited, it does not say if the internal speaker are turned off if an extension cab is connected.

 

i suspect the internal speaker is completely independent from the impedance selector, so with internal wire you need 16ohm you could put one 16ohm speaker in or two 8hm in series, no matter what

 

or you could get two of these:

http://www.tubeampdoctor.com/en/shop_Cables_Jacks_amp_Plugs_finished_cables/TAD_Amp_Speaker_cable_0_6m_with_right_angle_phon_1771

 

and use the external cab jacks (as you have two) to hook your new speakers with them up. remove the stock speaker from internal and unplugg their connection.

if you do it this way you cannot use an extension cab anymore, and cause the internal speaker is not connected anymore you need to make sure, that you never turn the amp on, with the speaker cables unplugged otherwise it could damage your amp (especially the output tranny)

 

and as the manual says if you use 16ohm speaker with the two extension cab jacks, the impedance selector needs to be on 8ohm

[WRGKMC]

That amp does have a manual which does tell you the basics. It does have an impedance switch so the amp can be set for 4, 8, or 16 ohms.

http://www.bugera-amps.com/PDF/Downloads/333_P0406_M_EN.pdf

 

Matching cab impedances shouldn't be too difficult, especially if you have two 8 ohm setups. A 4X12 cab at 8 ohms and a pair of 16 ohms in the combo will give you 4 ohms when the external can is plugged in.

 

The impedance switch switches between three different output transformer coil taps and so long as the total load matches one of the three settings it will be safe to run. Its always good to get in the habit of checking that switch at every gig to avoid having the wrong setting.

 

I'm surprised the Bugera doesn't sound good stock. My buddy has one and it sounds killer live. It may not bet the best match for your instrument or effects pedals but I've played through them a few times live and they sound decent to me. I didn't get much time to fiddle with it at those open mic gigs but it sounded good with the settings dialed up.

[t_e_l_e]

^he does want to replace the internal speakers, cause the 4x12 does sound better then the stock speakers. fair enough. he has already one spare 16ohm celestion speaker, adding a second one would load the cab of the amp.

but the internal speakers are 2x8ohm in series = 16ohm, so he can't wire the two 16 ohm speakers to the output where the internal speakers are now.

the impedance switch does only effect the external speaker jacks, not the wiring of the internal speakers.

 

so yes he can remove the internal speakers, the internal wire must not be connected to anything, and the two new 16ohm speaker are plugged into the external speaker jacks with the impedance switch set to 8ohm.

 

-> internal speakers are replaced, the already existing 16ohm speaker can be reused, no extension cab can be plugged in additionally anymore

[DeepEnd]

Okay, the Bugera web site just says "2 original 12" BUGERA guitar speakers" http://www.bugera-amps.com/EN/products/333XL-212-INFINIUM.aspx. I'm going to go out on a limb and say they're probably rebranded Eminences. This will give you a starting point as far as what to avoid. Find out what's in your cab that you like, then go with the same brand and series if possible. Most Celestions sound more alike than different. Any two Jensen Jets or Mods will sound similar. Unfortunately, as t_e_l_e has pointed out, you won't be able to use that stray Celestion you have lying around so you'll have to save it for another project. You'll need two 8 Ohm speakers in series.

[WRGKMC]

 

^he does want to replace the internal speakers, cause the 4x12 does sound better then the stock speakers. fair enough. he has already one spare 16ohm celestion speaker, adding a second one would load the cab of the amp.

but the internal speakers are 2x8ohm in series = 16ohm, so he can't wire the two 16 ohm speakers to the output where the internal speakers are now.

the impedance switch does only effect the external speaker jacks, not the wiring of the internal speakers.

 

so yes he can remove the internal speakers, the internal wire must not be connected to anything, and the two new 16ohm speaker are plugged into the external speaker jacks with the impedance switch set to 8ohm.

 

-> internal speakers are replaced, the already existing 16ohm speaker can be reused, no extension cab can be plugged in additionally anymore

 

 

 

I'm not quite understanding you here. The combo has a pair of 8 ohm speakers that are wired in series for 16 ohms. He cant run the 8 ohm extension cab at the same time because he will get an oddball impedance.

 

He has one 16 ohms Celestion and wants to get another so he can run the combo at 8 ohms solo. He can then set the impedance selector switch for 4 ohms and run both the internal speakers and extension cab in parallel at the same time. This wont be a problem so long as he remembers to switch the impedance selector switch back to 8 ohms when he runs the combo solo.

 

My other comments were about getting a good match between the combo speakers and the 4X12 cab. If he knew what kind of speakers were in the 4X12 he could choose 2X16 ohm speakers for the combo that would have similar SPL and frequency responses.

 

Chances are, its the air volume of the 4X12 cab that's giving him the bass kick he likes. an open backed combo sounds very different in comparison. Even if the speakers are the same type and SPL they wont have the same bass response in an open backed cab. Running both cabs can sound good though so long as either the combo or 4X12 doesn't over power the other.

 

He can buy another GT75 here for $25 http://www.ebay.com/itm/Celestion-Ma...item1c46ad99ba

 

I have four 75W Celestion's in my Marshall 1960 cab. I'm not sure they are the same as the GT-75. They were loaded in the cab when I bought it 10 years ago and the cab was at least 20 years older then that. They may be the same and just changed the label on them.

 

 

The speakers do produce a good sound in that cab. They have some midrange boost in the 2~5K range so I'm not sure if they will make the combo sound better. You just have to try them and see.

[eeddings]

Thanks tele, wrgkmc, and deepend for your insights. This is why I asked here on HC, guys. I understand the dilemma you're posing tele -- the switch on the back may or may not affect the impedance of the internal speakers -- and that is certainly something I had not considered. And, yes tele, you're right -- I do not know what I am doing. But, I am one hell of a researcher!

 

Wrgkmc, I also had not considered that I'd need to run the switch at 4 ohms if I hooked up two 8 ohm cabs, nor did I consider what I'd need to set that impedance switch on the back to if I were running the stock internal speakers at 16 ohm and the external 8 ohm cab. That G12T you linked on ebay -- wow, it's nto int eh best looking shape, but maybe it is fine. it does not list the impedance though, or the wattage. That scares me.

 

Deepend, eerything I've read about Behringer is that they make their own speakers and even own the land that fells the trees that make the paper in the cones. Regardless, I may need to give the stock internal speakers on this combo another shot.

[t_e_l_e]

the impedance switch is only for the external speaker jacks. the internal speakers are hooked on a separate 16ohm output from the output transformer. anything else would be not logical and "dangerous" cause there is no reference that the internal speaker ohmage affects the switch position.

it does only state if you use two cabs, they should have the same ohms e.g. 2x8ohm and than the switch needs to be at 4ohm, as the table in the manual says.

 

if the internal speaker would affect anything of the external jacks it must be explained in the manual and it would be prone the wrong use and configuration, as still complicates things again much more and doing things wrong becomes more likely...

[DeepEnd]

The manual has a reference to "Wiring the Bugera" (page 8) but it appears to apply to a separate head (the same manual covers about four amps). Your best bet is to contact Bugera and ask whether the impedance switch affects the internal speakers: http://www.bugera-amps.com/EN/Support/index.aspx. If you don't get a response, it's best to err on the side of caution, as t_e_l_e has suggested.

[eeddings]

Thanks for all the comments, guys. I've been running through the Bugera stock again for a few days and no matter what to me I just feel like my sound through the 4x12 is more to my taste vs. the stock 2x12 speakers in the Bugera. This could be the open back, the speakers, or just my ever-increasing deafness. :-D

 

I think what I have decided is best for me at this time is to keep the Bugera stock and build myself a sealed 2x12 cabinet, throw in the G12T-75 I have and another that I have yet to find, and wire it how I deem fit at that time (knowing that its impedance can easily be changed to 8 or 16 ohms with a quick rewire if necessary). I'm limited on space in my man cave so building a 2x12 to fit a specific spot across the room appeals to me greatly.

 

This gives me an extra cab, more sound in my room, and no chance of me jacking up the Bugera.

 

Now if I could just figure out how to switch channels on that Bugera with my Octa-Switch like I could my Marshall...

[DeepEnd]

. . . I think what I have decided is best for me at this time is to keep the Bugera stock and build myself a sealed 2x12 cabinet' date=' throw in the G12T-75 I have and another that I have yet to find, and wire it how I deem fit at that time (knowing that its impedance can easily be changed to 8 or 16 ohms with a quick rewire if necessary). . . .[/quote']

No, it can't. With two 16 Ohm speakers, you can wire them for 8 Ohms or 32 Ohms but not 16. A 16 and an 8 can be wired for 5 1/3 Ohms or 24 Ohms but that carries its own issues in terms of mismatched speakers. By all means go ahead with your cab build but have this stuff figured out first.

[eeddings]

Ahh yeah, thanks DeepEnd. I'm still learning but most likely I'd wire the two 16 ohms parallel to get 8 ohm impedance. I'd be following the diagram I posted on the first page of this thread. I certainly wouldn't do it anything guidance from multiple sources. I also have open questions to Bugera support about the impedance switch and whether it affects the internal speakers.

[WRGKMC]

 

the impedance switch is only for the external speaker jacks.

 

 

The impedance switch in any tube head (including this one) is for selecting the correct coil tap off the output transformer. You set it to match the total load impedance to match "all" speakers connected to the head.

 

The only way you could have the external speakers on the switch by themselves is if the internal and external speakers had a separate output transformers like they would with a stereo head.

 

There may be wording in the manual that doesn't include or describe the internal speakers load. Manuals are written for users who don't understand much about impedances and some are outright awful. They figure people don't normally go around swapping the combo speakers and when they do they would likely use the same impedance speakers.

 

This is why its important to ask a qualified tech trained on these topics to give you proper answers.

 

 

Here's the output section of the amp which clearly shows how the switch taps different output transformer coils (the transformer itself is omitted for the diagram on this page but you can find it is you download the complete schematics here. http://bmamps.com/Tech_sch.html

 

 

[eeddings]

I did get a response from Bugera Customer Care today, and I thought'd I'd share. Here it is:

 

"Thank you for your email regarding the 333XL-212 INFINIUM.

 

An external 4x12 speaker cabinet can certainly be used with this amplifier. Using it in conjunction with the internal speakers poses an odd impedance, however. With the internal speakers being 16 ohms and the cabinet being 8 ohms, this brings the overall resistance down to 5.333 ohms. This is, obviously, an unusual resistance. However, you can set the impedance switch to 4 ohms and the setup will function just fine.

 

The impedance switch of the amplifier applies to the loudspeaker outputs of the amp. As the internal speakers of the amp connect here, this switch will affect everything.

 

I hope this helps!"

[t_e_l_e]

^i stand corrected, thx to the support

 

@WRGMC: my search for the schematic was not successfull, google didn't show me

i downloaded it, but especially the section with the switch is hard to read. i'm not used to these symbols, where the lines have crosses and the small circles, is this now a connection or not? will the extension speaker jacks short anything if something is plugged in etc...

this schematic is very confusing for me.

 

some other schematics are clearer drawn, but also some are confusing (at least for me as i'm not a pro schematic guru) when it comes to how switches drawn or sometimes pots or dual pots, and it gets worse if there is only a bad scan of a hand drawn schematic

[eeddings]

Any concerns here from the gurus on this forum regarding Bugera Customer Care stating that running the internal speakers at 16 ohm and the external cab at 8 ohm with the impedance switch set to 4 ohm is acceptable?

 

Just curious to hear your thoughts. Thanks!

[t_e_l_e]

if the customer support says so...

but yes its about how tube amps work, it is save to set the impedance switch to 4 ohm and have with 16||8ohm 5.33ohm a bit more connected to it.

 

the amp it self will just be not 100% effective and can not use its full power (or last percents of it )

 

when you have time google it up and read about the details, one of the details is that solid state amps work differently regarding their speaker and in some way exact the opposite as tube amps. so what is safe for tube amps is dangerous for solid state amps and vice verse

 

i myself always mix them up, therefore when the question arises, i need to google and read it up again and again not to do the wrong thing to the wrong amp, better safe than sorry

[DeepEnd]

Any concerns here from the gurus on this forum regarding Bugera Customer Care stating that running the internal speakers at 16 ohm and the external cab at 8 ohm with the impedance switch set to 4 ohm is acceptable?

 

Just curious to hear your thoughts. Thanks!

As I mentioned previously, you can do it. Speaker impedance is kind of an average anyway with higher and lower values at different frequencies. But I believe you'll end up with roughly twice as much power going to the external cab as you will to the internal speakers because of the lower (by 1/2) impedance of the cab. As long as both sets of speakers (internal and external) can handle it, you should be fine. With any luck, someone who knows more about this stuff will either confirm or disprove this. Personally, I'd match impedances on principle but that's me.