A Question about extension speaker

Gary Meyer · Post by **Gary Meyer** » 21 Jan 2005 2:53 am

I have an empty ext. cabinet and want to put a speaker in it. My question is, Should the speaker be the same wattage as the one being used in the amp? Or will it put an uneven load on my Fender stage amp ? Thanks

jim milewski · Post by **jim milewski** » 21 Jan 2005 3:11 am

the ohms of the speaker determine the load, I would assume that an eight ohm and not a four ohm would be the recommended ohms on the extension speaker. As for wattage of the extension speaker on a Fender I wouldn't go less than 100 watts RMS, although two speakers (the internal and the external) would share the load so a lesser wattage may be suitable without danger of blowing the external speaker, also depends how loud you run the amp[This message was edited by jim milewski on 21 January 2005 at 03:14 AM.]

Roger Kelly · Post by **Roger Kelly** » 21 Jan 2005 7:03 am

Gary, it would help to know what type Amplifier and the impedence of the speaker that you are going to make this addition to.

If you have an amp with a 4 ohm speaker and you want to add an extension speaker, adding another 4 ohm speaker wired in parallel( + to + and - to -) can be VERY risky to your Amplifier, since the TOTAL impedence will then be 2 ohms. Some manufacturers don't recommend that you do this, since 2 ohms is very close to ground and may cause your speaker to blow. Most recommend using 8 ohm speakers in parallel, for a TOTAL of 4 Ohms, assuming of course, that your amplifier wants to see a 4 ohm load. By the way, most out of the box type combo Amplifiers that are rated for 200 watts will use speakers rated anywhere from 150 watts to 300 watts. It is not uncommon to find a 150 watt speaker being driven by a 200 watt amplifier. I use a 200 watt Evans Amp with a 8 ohm speaker, along with an extension cabinet with an 8 ohm speaker wired in parallel, for a TOTAL of 4 ohms and it works just fine. Even without the extension cabinet, and with an 8 ohm load instead of 4 ohms, I still have enough power for all the places that I play. Hope this helps answer your question.

Kevin Hatton · Post by **Kevin Hatton** » 21 Jan 2005 8:28 am

What about using an 8 ohm extension with a 4 ohm main. I do this with my Webb and it works just fine.

jim milewski · Post by **jim milewski** » 21 Jan 2005 9:26 am

I'm guessing that if an amp has an external out they built the output to handle it, you can always put your hand on the the heatsink of the amp to see if an external speaker makes it run to hot

Bob Metzger · Post by **Bob Metzger** » 21 Jan 2005 10:10 am

Fender tube amps are generally very tolerant of an ohmage mismatch, although they work best with the recommended load. Some harp players seem to like to run Fender tube amps with ohmage mismatches, for some tone related reason.

Solid state amps get more efficient as the impedance lowers but this is not an absolute, so check with the manufacturer (that would be Fender) of your amp. If you use an extension speaker through a jack so labeled on your amp, it will most likely be in parallel (but not in all cases). Then the amp will be pushing more watts, it will heat up more (amps aren't perfectly efficient in their power transfer, some is lost in heat) and you'll have to determine if you're in the 'safe' range or not. Most well made solid state amps have thermal overloads that, in theory, shut down before damage occurs. It's hard to say if yours does without looking at the schematic or taking it out of the wood. Check with your tech.

With two speakers of equal efficiency, a 4 ohm speaker will pull more wattage than an 8 ohm speaker and be the louder of the two, when used together. Remember, you can wire speakers in parallel (which is more commonly seen) but also in series. With a 4 speaker arrays, the world is your oyster and you can do all sorts of things with series/parallel and parallel/series as well.

The short answer is try it and monitor your amps' condition carefully and frequently, at least for the first few times. Using an extension speaker rated at, at least, one-half of your amp's output wattage and, at least, equal or greater ohmage than the existing speaker (that's already in the amp) seems to me to be prudent without really knowing anything about your rig.

Bob M.[This message was edited by Bob Metzger on 21 January 2005 at 10:28 AM.]

Roger Kelly · Post by **Roger Kelly** » 21 Jan 2005 10:35 am

Kevin, when using a 8 ohm extension speaker in parallel with a 4 ohm speaker you get a TOTAL of 2.66 ohms. There is no reason for a lot of concern doing this, it's just that if you get into a lot of distortion you can possibly take out our output transistors. In a tube type amplifier it is not as critical in my opinion.

David Spangler · Post by **David Spangler** » 24 Jan 2005 5:55 pm

According to what I have read, the Fender Stage amp is solid-state with a 4-ohm internal speaker. If there is an extension speaker jack, then the extension speaker impedance should be no lower than 4-ohms. Here's a link from Harmony Central user reviews with information about the Fender Stage amp: http://www.harmony-central.com/Guitar/Data/Fender/Stage_100_DSP_112_Combo-01.html

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David Spangler

Roger Kelly · Post by **Roger Kelly** » 25 Jan 2005 7:17 am

David, upon reading the Spec. sheet provided by Musician's Friend (pdf) on the Stage 100 and Stage 160 Fender Amps. It would seem that the Stage 100 comes with a 12" 8 ohm 100 Watt speaker and has an output of 100 Watts of music power, whereas the Stage 160 comes with 2 12" 8 ohm speakers and is wired internally for a 4 ohm load giving the amp a total of 160 Watts of music power.
So to answer the origional question raised, all Gary would need to do, since he has a stock 8 ohm speaker in his Stage 100, is to add (plug in) another speaker cabinet using a 12" 8 ohm 100 Watt Speaker, and he would have in essence a Stage 160 amp with a 4 ohm load.