extension cabinet advice please

[Ian D.Pocket]

Howdy all, great forum! Hope I'm not too long winded here.

I'm looking to get a little more volume from my amps for practice and gigs. I can't fathom this ohm/series/parallel business. Any suggestions, from knowledgable folks on a 2x10 extension cabinet would be appreciated.

Gigs are at small venues (bar/restaurants) and volume is never at ear shattering levels. Music styles are classic blues and r&b, 50's & 60's r&r, RaB, jump blues, honky tonk... (nothing current).

My axes are a '62 RI Precision w/flatwounds and a plywood double bass w/pre amp & pick up.

My amps are a Hartke 2115 (200w, 8 ohm ((I think)), 15" combo)and a SWR Workingmans 12 (100w, 8 ohm ((I think)),12" combo).

I've read that these amps will pump out a little more juice with extension cabs but this ohm matching stuff has me bewildered. Pardon my ignorance. Thanks in advance.

[_Sweet Willie_]

Hi Ian,

 

Based on the info at the Hartke website, it looks like the 2115 combo doesn't have an output jack for an extension speaker, so you couldn't run one anyway with that combo. It also looks like the speaker in there is a 4-ohm 15" speaker and the amp puts 200W into a 4-ohm minimum load -- therefore you couldn't lower the impedance by adding another cab in parallel.

 

With the WM12, it's an 8-ohm 12" speaker in your combo, getting 120W. You can add another 8-ohm speaker cabinet by plugging into the extension speaker jack on the amp. This will connect the extension cab in parallel, lowering your overall load to 4-ohms (the minimum for this combo). You will then be up to 160W from your amp.

 

The increase of 40W won't do a whole lot to increase your volume, but increasing the number of speakers will have you pushing some more air and contribute to increased volume.

 

Most of the time we end up adding/connecting multiple speaker cabs in parallel, which reduces the overall impedance of our rigs (fewer ohms). There have been a couple of accounts on this board about connecting speaker cabs in series, increasing the impedance (more ohms), which is more uncommon since increasing the impedance reduces the amount of power you would get from your amp.

 

There are others who post here regularly who can probably give more precise tech info and clarify/refine what I've written. Hopefully this will help get you started.

 

Peace.

[coyote]

OK, a couple things.

 

First off, two speakers definitely move more air than one. So all other things being equal, adding speakers will increase your volume.

 

Ohms measure resistance. When you put resistant devices in series, the resistance increases. When you put those devices next to each other in parallel, the resistance decreases. So....

 

a pair of 8 ohm cabinets in series will provide a total resistance of 16 ohms. The same pair of cabinets in parallel will provide a total resistance of 4 ohms. Some amps automatically compensate for this; others have switches which need to be set.

[_Sweet Willie_]

Ian,

 

Also try using the forum's "search" feature (upper right corner of your screen). There has been prior discussion of extension cabs and the relationships between amplifiers, speakers, watts, and ohms.

 

--sweets

[alexclaber]

I know this is really obvious, but have you tried using the two combos simultaneously? You could stack the SWR on the Harkte and the combination of 12" and 15" speakers should give you a pretty fat clear tone, plus as a stack they'll project more across the stage.

 

Alex

[Ian D.Pocket]

Many thanks on your input regarding my output!

 

I have not been able to determine, from the Hartke and SWR web sites, exactly what my combos contain.

 

Sweets: on the back panel of the Hartke, alongside

the jack labeled "8 ohms" that the amp is plugged into, is another jack also labeled "8 ohms". Might this be an output? The only thing I see in it's manual is "speaker specs should be at least 250 watts @ 4 ohms".

 

No regrets Coyote (pardon me), but how do I know if hooking up a cabinet will result in a series or parallel connection?

 

C.Alex: Your suggestion did not occur to me (DUH!). Would I plug the instrument into the SWR and go from it's speaker ext. output to the "active" input on the front of the Hartke,... or what?

 

Thank you all.

[_Sweet Willie_]

If you run the two combos together, run a speaker cable (not an instrument cable!) from the extension jack on the SWR to an input jack for the speaker cab portion of your Hartke combo -- probably on the back of the cabinet. You don't want to run the cable to where you'd normally plug in your instrument, but rather where the amp is connected to the speaker ('cause that's what you'd be doing, connecting the SWR's amplifier to the Hartke's speaker). I don't know what the Hartke is set up like in the back in terms of jacks, and the Hartke website is less than helpful. You may want to call or e-mail them, however, because you would need to verify whether you have a 4-ohm or 8-ohm speaker in that combo. If it's an 8-ohm speaker, you're in good shape; if it's a 4-ohm speaker you won't be able to run both combos linked together.

 

The SWR WM12 is definitely an 8-ohm speaker, and the combo is rated at 120W RMS. For an extension, you need a speaker cab rated at 8-ohms. Connecting the extension cab with a speaker cable to the extension out jack on your WM12 will result in the speakers being hooked up in parallel, resulting in a 4-ohm load, and an increased wattage rating of 160W RMS.

[cornbread_medhotmail.com]

I used to do the amp chain thing a while back. You plug your bass into the SWR and go from either the Tuner out on the front or the Effect Send on the back into the Hartke active jack. You set the SWR eq the way you like it and the Hartke eq flat, or just a little tweaking. You'll be using the SWR like a preamp and the Hartke like a power amp.

[...]

Originally posted by Ian D.Pocket:

No regrets Coyote (pardon me)

I SO just played an Eb power chord when I read this.(OK, it was just the root and the five... and it was in my head, but it still counts, dammit!!)

[Edendude]

Assuming both your combo amps have an 'effects send' and 'effects return' jack, the best plan for you is to use both your amps at the same time, and save you money by not buying an extra cab. Simply plug your bass into the SWR as you would normally do, and run another instrument cable from the 'send' jack on the back of the SWR, to the 'return' jack of the Hartke.

 

I have a pair of amps, and this is how I run them...

 

http://herne.tripod.com/bassrig.html

[where02190]

Adding a cabinet does not guarrantee more volume. In fact, if the cabinet speaker youa re adding is low efficiency, you could actually loose volume, as the new cabinste would require more power to operate at the rated spl than your existing speaker system.

DO NOT- UNDER ANY CIRCUMSTANCES- CONNECT AN AMPLIFER OUTPUT TO ANOTHER AMPLIFIER INPUT!!!!!!!! You will immpediately smoke the input of the amp.

 

Utilize line level outputs, tuner feeds, effects sends, etc, to connect two amps together.

 

the 8 ohm connector on the back or your Hartke is for an 8 ohm extension cab.

 

Hope this is helpful.

[Ian D.Pocket]

Thanks for all the advice.

 

If I had posted my second reply BEFORE the Grey Goose martini,

on the back panel of the Hartke, alongside the jack labeled "8 ohms" that the amp is plugged into,

it would have been obvious that the amp wasn't plugged into anything. The SPEAKER is plugged into the amp! So that jack alongside it probably is another output.

 

One (last?) new question arrises. If I do purchase, say, a 2x10 cab, must I be concerned if the two speakers are 4 ohms each or 8 ohms each? Will there be some info, somewhere, stating what load will be placed on the amp?

 

Babies...you're the greatest!

[_Sweet Willie_]

If you buy a 2x10 cab, the cab should have a rating of 8-ohms. Close to the input jacks it should say that it is an 8-ohm cab. You don't need to worry about the impedance of each speaker in the cab, because the manufacturer will print the rating for the whole cab, taking into account individual speaker impedances.

[Edendude]

Actually there is no 'should' about it, when it comes to cabinet impedences. 2x10 cabs are available in both 8 and 4 ohm impedences from most manufacturers. My Eden 2x10 cab is a 4 ohm model. So check the back of the cabinet first.

 

In your situation, you will want an 8 ohm cab as an extension speaker. A 4 ohm cab may actually cause your amp to do the old 'Hey look at me I'm melting down' routine'. Don't wory about the individual driver impedences.

 

But hey, try using both your combo amps together first, because it may give you the added volume you are seeking, and all of this will be moot.

 

As suggested by myself and others above...use the effects 'send' and 'return' jacks to do this, and do not connect any speaker outputs to either of your amp's inputs.

[_Sweet Willie_]

Originally posted by Edendude:

Actually there is no 'should' about it, when it comes to cabinet impedences. 2x10 cabs are available in both 8 and 4 ohm impedences from most manufacturers. My Eden 2x10 cab is a 4 ohm model. So check the back of the cabinet first.

 

In your situation, you will want an 8 ohm cab as an extension speaker. A 4 ohm cab may actually cause your amp to do the old 'Hey look at me I'm melting down' routine'. Don't wory about the individual driver impedences.

Right -- there is no "should" about it. Your extension cab must be an 8-ohm cab.

 

If the amp in the Hartke combo is the same as the Hartke 2000 head (which I used to own), I don't think it has send/return effects jacks so that may not be an option in terms of linking your two combos together (although my memory may not be correct about that). IMHO, if you want to try to hook up the two combos, you want to try to connect your WM12 extension speaker out via speaker cable to an input jack for the speaker (NOT the amp) of your Hartke combo (if such an input jack exists!). If you are able to do this, verify with Hartke that the 15" speaker in your combo has an 8-ohm impedance.

[g.]

Doesn't anybody's amps or cabs come with a manual or specsheet these days? Don't any manufacturers have this info downloadable on their website? Haven't I answered these same questions umpty-gazillion times here and elsewhere? - And why am I muttering to myself? ; }

[_Sweet Willie_]

The SWR website is pretty good in terms of downloadable specs and manuals. I thought Hartke's was pretty weak in that regard.

 

Keep on mutterin'!