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Posted by: Ajmurrell Sep 14 2008, 01:52 AM

Thanks to people's advise and agreement on the Hughes and Kettner Switchblade, I'm shortly about to make an ebay purchase on a 50W Switchblade Combo

Now my rather simple question which I'm sure has been answered THOUSANDS of times, and ranks fairly basic in amp questions... But, if I connect this amp to a 2x12 or 4x12 cab at some point in the future, the output will always be maximum 50Watts correct? Or if I'm looking at 2/4 x 75W speakers, does that increase the volume significantly?

I kinda understand the theory that an amp can only power the speakers to the amp's wattage, but I get slightly confused when 4 speakers or more are run of the same amp...

Thanks for your help!

EDIT: Just to also note it has output options of 4, 1 x 8, 2 x 16, 16 Ohm's.

Posted by: skennington Sep 14 2008, 02:03 AM

Hi AJ,

Regardless of what you connect it to, it's still only going to produce 75w max output. You could have it connected to a cab the could handle a 1000w and still only reap what the amp produces. Assuming that this is a tube amp, and if you are going to be using it at low levels, I would suggest an attenuator as well. An attenuator is an electronic device that reduces the amplitude or power of a signal without appreciably distorting its waveform. ...

Posted by: Emir Hot Sep 14 2008, 02:05 AM

I would also like to know how this works. I have 4 years of school about these electronical things but I don't know much about any of that:) The only thing I know is if you connect more cabinets they all sound the same volume so the obvious thing would be more cabs = more volume. I hope somebody will help with this question as I am also interested and thanks for asking about this.

Posted by: Ajmurrell Sep 14 2008, 02:10 AM

Thanks for your response, I thought that would be the answer, but just wanted to check in regards to multiple speakers!

So just to recap - If I have a 50Watt amp powering 4 speaker's within a cabinet, they're combined output would be 50 Watts maximum? Or would each produce a 50Watt signal output?? Sorry if thats the same question, just want to make sure I understand!

Yeah it is an all tube amp, so 50Watts is significantly more than I'd need at home. But at least this way if I choose to gig it, I have the option although to be honest, I'll more likely drag my Marshall DFX

I probably will invest in an attenuator, which raises another question heh... Is it possible to put an attenuator in the combo circuit for the built in speaker? I'm not sure if the cables are accessible.

Am I right in presuming you'd recommend an attenuator with or without a cab?

Thanks again for your speedy response!

Currently listening to lots of shouting coming from outside, where two very drunk thug like beings have come back from a night on the town... Woo!

Posted by: skennington Sep 14 2008, 02:29 AM

Yes, just place the unit between the amp's speaker out and the speaker itself. Most combos of decent quality connect the speaker to the amp via a 1/4" trs.

As far as Emir's question, think of it like this. You have 4 12" sub's in the back of your car with only the stereo pushing them....Not going to get much punch. Then, you put an amp in line that let's say is 500 watts. It could be 500w X 4 which means you have 125w going to 4 seperate channels. If the amp is bridged, then you get 250w going to 2 channels. It all depends on the wireing in the setup.

Now, with a guitar amp, the speakers/cabs have nothing to do with the output, it's all in the amp. If you were to connect a 1000w amp to a set of speakers that is rated for 100w max....guess what's going to happen...boom, you will blow them.


Hope this helps you guys a bit.

Posted by: Ajmurrell Sep 14 2008, 02:37 AM

Excellent, understand now thanks

I guess now I just need to find out if the amp does have an external 1/4" connector to the speaker. With a price of £1000+ I'd hope so!!

Thanks again for your help.

Posted by: Emir Hot Sep 14 2008, 02:38 AM

I know that I would burn speakers like that but what if the amp is 50W and my 4 cabinets 100w each conected in serial?

Posted by: skennington Sep 14 2008, 03:00 AM

Your welcome AJ




Emir,

With the 4 cabs connected in serial, your still only going to get 50w to them. The amp is the power source so thats all that's being sent. You will have a broader sound range, but no more power. IMO, you would be better off mic'n one cab to a PA system with powered monitors. The monitors will have internal amplification. There's quite a few options and can get pricy...JBL offers some quality powered pa's.

Posted by: Emir Hot Sep 14 2008, 03:24 AM

I understand that I won't have more than 50W in each speaker. But will all cabinets get 50W? If yes, this means that the sound should be louder with 4 speakers than just 1 regardles of 50W. Is this correct?

I know I can hear my self in monitor but never liked that on stage. Monitor completely changes my sound. I always prefered my original sound from my speakers behind me. So if I have 4 of them I should hear myself better than with 1. Please correct me if this is wrong. I am just reading some articles about this on wikipedia.

Posted by: skennington Sep 14 2008, 04:18 AM

Yes Emir, you will have a broader sound field with the cab's arranged behind you,the output will be the same but you should hear yourself better. When performing, do you have someone controlling a board?

I feel like a child here trying to answer his father's question... You rock man! Anything you play through will be lit up!

Posted by: Emir Hot Sep 14 2008, 12:06 PM

Yes I always have someone who is controling board but I don't hear those speakers because I am standing behind them on stage.

Thank you for the answer .

Posted by: Bogdan Radovic Sep 14 2008, 02:43 PM

I like to hear about this..What I heard before , if you increase the Ohm value (load) with additional speakers you will loose some power from the amp (if its rated to put out I don't know 50watts at 4ohm)..So if its serial connection you are increasing the ohm value and if its parallel you are kinda a splitting it (I don't know the exact count just that two 8ohm cabs together give 4ohms load if in parallel).Also every time you add additional speakers you gain actual volume in dB because of added speaker surface (and more air being moved) ! That gain in volume allows even for slightly higher load on amp (when it actually looses some power) because when you do the math you get the same volume, maybe few dB's higher.So its all about matching the cabs to get the right load on the amp..

Posted by: Noangels Sep 14 2008, 03:45 PM

50 watts is easily loud enough for gigging with a tube amp,sticking another cab on it(2x12)will fatten up the tone a lot
I have the Blade 100 watt head with a 4x12 cab and it sounds great

Adding another cab wont increase the volume,but it might make it sound that way as the stereo spread is now wider or deeper.Each powertube handles 25 watts,so your two glowing tubes with be belting out 50 watts spread over the speaker range

stick another 2x12 under it and have fun:)

btw congrats on the Blade,after my tone search on tube amps in shops and with other musicians rigs I came to the conclusion the blade with its onboard digital FX was the right rig to go for in that price range(there are so many great tube amp heads out there,but they need seperate FX units and its realy cool to have all that tone choice in one amp with a great pedal for it too)

Posted by: Andrew Cockburn Sep 14 2008, 04:30 PM

Look at it this way -

The wattage of the speakers is nothing to do with power output, its just the maximum they can stand. No matter how many speakers you have, their output is shared between the power the amp outputs.

Crank your amp to full output and put it through one speaker - that speaker is getting all of the 50W. Now, hook up 10 speakers, and each speaker only gets 5W, so they will each be quieter but will add up to rouhgly the same volume.

Now, to be more complicated about it, different speaker respond to amps with greater or lesser loundness depending on their sensitivity, and this is just as important as the power. The comments I made above would be true if all 10 speakers were the same. If you introduce different speakers it changes - you could have a 30W amp into a very sensitive speaker be louder than a 50W amp into a less sensitive speaker.

A final point about impedances - the relationship between amp and speaker is not one way. Hooking in different speakers in different ways can also influence the amount of power an amp puts out, so it is all interconnected!

Posted by: Ajmurrell Sep 14 2008, 04:34 PM

Yeah the switchblade does excite me, after a lot of research (or as much as I could bare considering as soon as you get relatively up to date with models, another make props up with good reception and then it all gets complicated again! There really are so so so many different amps to choose from it gets really rather confusing).

The midi preset pedal is also a huge reason for getting this amp for me, besides that the amp gets raved about for good quality sound. Being able to fully record all the tweak pots in a preset is such a good feature. It even stores presets for the effects loop! Amazing. Can't wait to play around with it.

Posted by: skennington Sep 14 2008, 04:36 PM

Here's a great article on keeping the impedence within the amp's range....



Many people need to wire 2 or 4 sets of cabinets in a combination of series and parallel to keep the impedance within the range needed the Power amplifiers specified range. This article deals with 2 different ways you might want to consider.

See http://www.colomar.com/Shavano/spkr_wiring.html for loading considerations.

• 1) 2 or 4 Standard Speaker Cabinets - 1 or 2 Serial Patch Boxes
  Use this if you already have production speaker cabinets with a jack on the back, or you plan to build speaker cabinets in this configuration.
• 2) 2 or 4 Cabinets - Extra Jacks built into the Speaker Cabinets
  Consider this if you are building your own speaker cabinets, and want to build serial/parallel patch boxes into them.

1) 2 or 4 Standard Speaker Cabinets - 1 or 2 Serial Patch Boxes

If you power amplifier already has 2 speaker cabinet jacks on the back of it, creating a parallel circuit, you can build 2 series Patch Boxes (see http://www.colomar.com/Shavano/patchbox.html) and use one with each of the power amplifier output jacks.

The Wiring is quite simple, however you need to make sure that the jacks don't short each other out - I advise mounting them on something other than metal.

To connect 4 speakers together, you need 2 Serial Patch Boxes. You will need a total of 6 cables. The big advantage is that you can connect any stock pre-wired Speaker cabinet up using this process, and you can reconfigure your speaker system as needed, anytime you need to - you don't require anything special to make it work.



Some suggested cable lengths per Series Adapter are:

• 2 short (10 feet long or less) power amp audio cables - for Out 1 and Out 2.
• 1 long (30 feet long or longer) power amp audio cable - for the connection to the Series Adapter Input and the audio power amplifier speaker jack.

If your speakers will be grouped in 2's on either side of the stage:

Take the long cables, plug one end into the Input of the Series Adapter and the other end into one of the 2 power amplifier speaker cabinet jacks. Do this for both Series Adapters. Run one Series Adapter over to the cabinets on the right hand side of the stage behind the speaker cabinets, the other to the left hand side behind the speaker cabinets. The, one each side of the stage, plug a cable into the Series Adapter Out 1, and the other end into one cabinet, and then plug a cable into the Series Adapter Out 2 and the other end into the other cabinet. Do the same on the other side. All of 3 of the jacks on each of the Series Adapters must be connected in order for it to work. This completes the wiring.

If your speakers will be placed anywhere on the stage (floor monitors are a typical example):

Take the long cables, plug one end into the Input of the Series Adapter and the other end into one of the 2 power amplifier speaker cabinet jacks. Do this for both Series Adapters. Run one Series Adapter over to the middle of where you will place 2 speaker cabinets. Do the same with the other Series Adapter. Plug a short cable into each of the speaker cabinets and then connect the other end into either Out 1 or Out 2 of the Series Adapter. All of 3 of the jacks on each of the Series Adapters must be connected in order for it to work. This completes the wiring.
If you are only wiring 2 speaker cabinets in Series
Its really the same process, except you only connect one Series Patch Adapter Box using 3 cables as shown here.
Repeat for each side of the stage if using 4 speakers.

2) 2 or 4 Cabinets - Extra Jacks built into the Speaker Cabinets

If you need to be able to wire up a set of cabinets in either Series or Parallel with each other, and don't want to carry around any special cables, you can do it by wiring the cabinets with a few extra sets of jacks.

You'll have to pay attention to how you connect the cables up, and you may want to print out this Web Page to assist you in figuring out the proper way to do this when setting up for performance.

If you use a road crew, or other members of the band occasionally help in the setup and tear down, you may want to number the cabinets (on the back) and have a diagram of how to wire the system properly that they cab work from. Color coded cables (at least on the Plugs) will help during setup. PLEASE NOTE: You cannot use a metal mounting plate to hold the Jacks - the Series In/Out will short out the speaker wires if you do, which will severely damage your power amplifier. Use plastic, Masonite (compressed fiber board) or thin plywood to mount the Jacks on.

Each cabinet is wired in this fashion - This could be a 2 way or 3 way cabinet (with passive crossovers). A single driver is shown to keep the concept simpler to manage.


2 Cabinets - Parallel Wiring


The impedance decreases. The equation is
Total Load = (S1 x S2) / (S1 + S2)
Where:
S1 = the impedance of Speaker load # 1
S2 = the impedance of Speaker load # 2




2 Speakers - Serial Wiring


The impedance is additive. Add up all the
loads to figure out the total load value.
Add up all the series loads:
Total Load = S1 + S2
Where:
S1 = the impedance of Speaker load # 1
S2 = the impedance of Speaker load # 2



4 Speakers - 2 in Series, 2 in Parallel
If you want to wire of 4 cabinets, and you need to control the load in such a way that 2 sets need to be in Parallel , and those need to be in Series with each other - providing the following:



you will be doing a combination of both of the above examples. You would wire it in the following way:

• Label your cabinets 1, 2, 3 and 4 (it makes no difference which is chosen for each individual position).
  
  Connect The Parallel Segments first
• Parallel-In of Cabinet 4 goes to Parallel-Out of Cabinet 3.
• Parallel-In of Cabinet 2 goes to Parallel-Out of Cabinet 1.
  
  Connect The Serial Segments Next
• Power Amp Audio Cable output connects to Serial-In of Cabinet 4.
• Serial-Out of Cabinet 4 connects Parallel-In of Cabinet 1

Cabinet 4 will have 3 cables plugged in to it. Cabinet 1 will have 2 cables plugged into it. Cabinets 2 and 3 will have one cable plugged into them.



Or, to simply have a single speaker in a cabinet, where you want to have either a prewired series or prewired parallel connection for your add on speaker cabinet:





For 1/4 inch (and 1/8 inch) phone jacks, you need to verify which solder tabs go to the + and - connections, 1/4 (and 1/8) inch phone jacks have no standard for which of the solder tabs goes to what. Open cased Jacks are easy to verify - just look at it. In an enclosed Jack, you may need to use a VOM/Digital Multimeter to check which connection goes to what. The + and - relate to how the speakers are connected. The speaker should have a colored dot on it to indicate + or it will be marked with a +.

Posted by: Ivan Milenkovic Sep 14 2008, 08:11 PM

Big thanks to Andrew and Skenny for nicely clarifying the speaker/amp relations



Q: "But, if I connect this amp to a 2x12 or 4x12 cab at some point in the future, the output will always be maximum 50Watts correct? Or if I'm looking at 2/4 x 75W speakers, does that increase the volume significantly?"

A: Your poweramp puts out 50W. Your speaker in combo is (probably) a little over 50W, like 60-70W. So you need a 2x12 with two 12" speakers rated @ ~30W each. You connect them in aither parallel (where you divide the speakers resistance), or series (where you add up the resistance).

for example:

2 speakers @ 30W (@8Ohm) - connect them in series and put the switch on the amp to 16Ohm
2 speakers @ 30W (@8Ohm) - connect them in parallel and put the switch to 4Ohm.

There are other important factors as Andrew said, like the sensitivity of the speakers. The greater seinsitivity - the louder the speaker. Also another important factor are open/closed backed cabs, and the size of the cabs, among other thing.

WHy is important to rate the cab a bit over the poweramp wattage rate? Because speakers makes the sound distorted as well by temporarily leaving the cone and making a natural distortion that adds to the sound of the amp. So if you rate the speaker to close to rated poweramp output, it will brake nicely when pushed hard. 15-30W is a good headroom to add on the speakers, depending on the power of the poweramp section.

Why is attenuator not getting a sound of a fully cranked amp? Because the part of the sound is in the speakers as well, when they are pushed hard. So if you put attenuator, or play at low volumes, you are giving the speaker less power and it will not leave the cone, and thus not give it's full potential.

So my recommendation for you is a 2x12 cab with a tight response from the speakers, rated at + (10-20) % of the wattage that power amp outputs. All other speakers or cabinets will sound good, but will miss that tightness, will not break nicely, and react a bit lazy.

Posted by: Ajmurrell Sep 14 2008, 10:50 PM

I second that, big thanks to you guys for your help

Understanding a lot more about what to look for if I ever do go for a cabinet speaker set-up.

One more question about what you suggest Ivan, I understand what you're saying about the tight response using speakers with a lower wattage, but just wanted to clarify...

If I was to say get a 2x12 cab with speakers at say 15W each (accomodating what you suggest for 10-20% of the power amp's rating. which in my example would 50W from the switchblade amp) would that not risk blowing out the speakers at max volume considering a series set-up would pump 25Watts into both speakers?

I only ask because of what Andrew stated earlier about having speakers at a lower wattage than that of the power amp can lead to blowing the speakers. Or would that really only take place with more extreme differences in wattage? Like when Andrew says plugging an 1000W amp into 100W speakers?

Thanks again you guys

Posted by: Ivan Milenkovic Sep 14 2008, 11:33 PM

No I haven't properly explained, sorry, english is not my first language. What I meant is take the power rating of the power amp, and add to it 20-30% and it will be OK.

So if you have 50W amp and 30% from 50W is 15W, that means that you get 50W+15W speaker. 50+15=65W. (which is the most often used combination for combo amps).

Also wanted to clarify that although the sound will not be as tight with higher power cabs (for example 2xGT75s or even 4xGT75s), it will still be possible to use them no problem, only on a smaller efficiency level.

Posted by: Ajmurrell Sep 14 2008, 11:35 PM

Thanks Ivan Help much appreciated!

Posted by: Emir Hot Sep 15 2008, 12:30 AM

Thanks everybody, now I have things much clearer

Posted by: kjutte Sep 15 2008, 08:20 AM

well that depends on the chosen output level aswell as the impedance.

Posted by: Ivan Milenkovic Sep 15 2008, 03:19 PM

Yeah it does, and also on on the chosen volume that is going out. If you run that amp on 10% of the power all the time, speakers will be fine. (it's not recommended tho )