How does speaker ohm effect sound, if at all?

[rjgtr]

I believe most everyone agrees starving your amp of wall power is very hard on it. I always use huge gauge (detachable) wire for the AC.

Not to argue, but I used to think a super heavy-duty power cord would be an improvement. Then I started building amps. The leads that come off a power transformer are not any heavier duty than regular zip cord, nor are any of the internal wires, really. Any system is only as strong as its weakest point, so an extra heavy-duty wire feeding a medium gauge wire is a waste of money, IMO. Besides, some people deliberately starve the power on their amps. In the hi-fi world, the better the quality, the better the sound, but not so much in guitar amps, in my experience.

The real decision to use a heavier cable should be based on length. The run from the EIN socket to the transformer is very short. The longer the run the heavier the cable should be to reduce loading. However, any computer EIN style cable should be fine for a guitar amp. If you have to use an extension cable you need to make sure it has enough capacity.

[KHStudio]

How many ohms were the speakers in the ORIGINAL 18 WATT AMPs???

Parallel or series???

What was the load - 8 or 16 ohms???


Kevin

Nobody knows?

Very strange

[bonanza2252003]

All Marshalls are designed for 8 ohms .I suspect the 18 watt was the same.

[rjgtr]

All Marshalls are designed for 8 ohms .I suspect the 18 watt was the same.

Then why were the early JTM-45s paired with 16 ohm cabinets? Marshall didn't start selling dual cabinet setups until the 100 watt amps.

[spunky]

Both my Marshall 4 x 12 cabs are 16 ohm and so are all the ones I have seen.
Do you set the inpedence to 8 ohm when connecting 2 of the 16 ohm cabinets?
Or do you leave it at 16 ohm when connecting 2, 16 ohm cabinets?

I never could figure what to do when connecting 2 cabinets...
One is a no-brainer

[KHStudio]

Both my Marshall 4 x 12 cabs are 16 ohm and so are all the ones I have seen.
Do you set the inpedence to 8 ohm when connecting 2 of the 16 ohm cabinets?
Or do you leave it at 16 ohm when connecting 2, 16 ohm cabinets?

I never could figure what to do when connecting 2 cabinets...
One is a no-brainer

2x 16 ohm cabs = 8 ohm load (amp)

Kevin

[KHStudio]

I'm starting to wonder if I'm in the right place

Does anyone know what ohm speakers the ORIGINAL MARSHALL 18W used?

Kevin

[Breogan]

Which original 18W?

The 2x10, 1x12 or 2x12?

It's not like I know the answer... But I think you don't know exactly what you are asking...

[rjgtr]

Ok,

I'll take a logical guess guess here. Marshall used 16 ohm speakers in the 4x12 cabinets (wired series/parallel). They also apparently used 16 speakers in the 1962 Bluesbreaker combo wired for 8 ohms.

So, I would deduce they also used 16 ohm speakers in the variations of the 18 watt. So the 1x12 version would be running at 16 ohms and the 2x12 would be running at 8 ohms (16/2 = 8 ).

I suppose someone could look at the galleries of the original 18 watts and see if they can see a marking.

[KHStudio]

Which original 18W?

The 2x10, 1x12 or 2x12?

It's not like I know the answer... But I think you don't know exactly what you are asking...

Good point... my fault.

I'm reffering to the 2x12 Model

I totally forgot about the single 12 & 2x10 models.

Sorry,
Kevin

[theDogger]

Let me ask this and I may be way off base with this question as I am a newbie and most experienced with 12v Car audio.

So my questions are this.

1-Wire gauge...the smaller the gauge of wire the less resistance correct? I have always opened up my 2x12 or 4x12 cabs no matter who made them and stripped out the crappy factory wires and replaced it with either twised 14g or16g wire and got rid of the skinny 18-20g OEM stuff and no clips, connected direct to the out puts by soldering them.

2-Not sure if this applies to 120v guitar amps but I assume it would...In general going from a 4ohm load at 80watts to a 2 Ohm load would allow for 160 watts. Does this apply to guitar amps? I realize that in car audio the amps are d-class. I have always tried to get to a 2 Ohm load for full power of the amp.

3-So having a 100watt head @ 16Ohms if you go to an hm load does this up the watts to 200Watts.


So sorry if I am way off base just trying to figure out how this applies to 120v which I am pretty sure it is the same?

thanks

theDogger

[CurtissRobin]

Smaller AWG (American Wire Gauge) numbers = larger gauge (thicker wire) = lower resistance per unit length. Odd numbered wire gauges are not used so AWG14 to AWG16 is a change of one size while AWG14 to AWG18 is two sizes. A rule of thumb (i.e. not a rigorous physical law) is that changing two standard sizes will halve or double the ampacity (current carrying capability) of a conductor. For example, AWG18 is rated to carry about half the current of AWG14. AWG10 carries about twice the current of AWG14. I won't go into detail but it's related to the fact that larger wire has lower resistance. (There's more to the story and that's why engineers go to universities.)

Your calculation of 80W into 4 ohms and 160W into 2 ohms is wrong. The OT is like a magnifying glass. If something changes on one side it affects what's on the other side. Change your speaker impedence and it changes the load the power tubes "see." EL84's like to run with a plate-to-plate load of about 8K ohms. If the OT 8 ohm tap is used you have a 1000:1 ratio. Put a 4 ohm speaker on that 8 ohm tap and your tubes "see" a 4K ohm load and they behave entirely differently. Power output nearly always falls and the sound changes unfavorably.

Solid state amps work best into low impedence loads. It's the physics of solid state electronics. The first time I played a solid state bass amp I freaked at the 2-ohm output. I was used to my Traynor YBA-1A that wants absolutely nothing less than 4 ohms or dire consequences were assured.

Some of your confusion surely stems from the shortcuts we take because most people don't want to know ALL that much about electricity and electronics. Plus, we can get away with a lot of laxity in design because despite textbook warnings, tubes work at much higher than design voltages, impedence mismatches aren't apocalyptic, speakers tolerate the incredible transients of severely distorted signals, etc., etc.

KennyO

[fisheric]

so the whole thing about lower impedance in a SS amp producing more power does not apply to tube amplifiers?

a 16ohm speaker and a 8 ohm speaker through the same amp will have the same loudness?

[Shrapnel]

so the whole thing about lower impedance in a SS amp producing more power does not apply to tube amplifiers?

a 16ohm speaker and a 8 ohm speaker through the same amp will have the same loudness?

Essentially, that is correct. With tube Amplifiers, impedance matching is more critical because that affects the load seen on the tubes. Hence, do not ever run a tube amp without a speaker or resistive load. (The resistive load is better than no load at all.) In essence, because it is better to match impedances with tube amps, power out stays the same.

Slew rates are part of what effects a SS amp's minimum load requirements. However, SS amps could care less if you provide a greater impedance, including no-load (infinate impedance). Also if you look at SS amps, you won't necessarily see a doubling of power out for a halving of the output impedance.

Also note: a doubling of the power give about 3Db signal boost, and to most, 3 Decibels louder is negligable and not even noticed.

[zaphod_phil]

One fact I recently learnt is that the highest impedance secondary winding tends to be the one most closely wound to the primary. This results in it having the most high frequency content of all the secondary windings. So, in theory at least, you can adjust the high frequency balance of your amp by your choice of speaker impedance, with 4 ohm being darkest and 16 ohm being brightest.

[wiseowl]

Also note: a doubling of the power give about 3Db signal boost, and to most, 3 Decibels louder is negligable and not even noticed.

I dont think that's quite correct. I believe a 3db increase sounds twice as loud, but to achieve that you need (all things being equal) a 10 fold increase in power.

I'm sure to be shot down in flames if I'm off the mark.

[katopan]

10 times the power is 10dB (3.16 times the voltage). It's generally accepted that 6-10dB (more often 10) is double the listening volume, 3dB is "a bit louder" and 1dB is the threshold of any perceivable difference.

[vicenzajay]

10 times the power is 10dB (3.16 times the voltage). It's generally accepted that 6-10dB (more often 10) is double the listening volume, 3dB is "a bit louder" and 1dB is the threshold of any perceivable difference.

And we have a winner....a 3db increase is certainly "noticeable" to those with normal hearing sensitivity.


Jay

[Merlinb]

Sorry if this seems like a hijack...about the Canadian Marshalls which weren't allowed to use the 16 ohm tap --

What? Sounds like a funny story to me... Unless they had a bad batch of OTs where the 16 ohm winding had been wound wrong!!

[laterider]

bringing this one back, I don't think the OP's question was really ever answered and I have a question about on wiring for 2x12's...

Using a 2x12 setup with 8ohm spkrs what's going to sound better (if there is a difference) parallel to run at 4 ohms or series to run at 16? I would be matching the impedance selector to 4 or 16 as required...
I read somewhere that parallel is the better setup since series can cause losses or loss of highs, etc.. but is that practical or just theory?

(I'm not even going to ask about using the 16 tap vs 4 because its runs the full length of the.....)

This is for a non-18watt project and I got the speakers cheap or I would have gotten 16ohm spkrs, run parallel and used the middle tap....lol... which is how my 2x12 18watt is wired!!!