8 ohm speaker in 4 ohm SS amp?

[daz]

results? Volume? any danger to outputs? Anything i might not have thought of?

[Enzo]

8 ohms is half the load that 4 ohms is. This is like a truck with a one ton capacity and asking it to haul only half a ton. The amap wwill be happy.

[daz]

Hmmm....replied already but somehow my post is gone or maybe i didn't hit submit right or whatever. Anyways, thanks Enzo.

[Gingertube]

daz,
For guidance ONLY - My alternate (to my tube HiFi Amp) Solid State HIFi power Amp delivers 90 Watts into 4 Ohms and 55 Watts into 8 Ohms. That ratio is typical. I doubt if you would notice any sonic difference.
Cheers,
Ian

[Enzo]

Electrically, for a given output voltage, the 8 ohm load will DRAW half the current a 4 ohm will. Due to various circuit factors, in reality it won;t be quite 2 to 1. Thus 90/55 rather than the expected 90/45 watts.

[daz]

I DO notice the difference in volume at home volumes. The 8 ohm EV isn't as loud as the stock celestion so i gotta thing it does affect it. Then aga;sin maybe at stage volume the EV will take over as champ once at a certain level because it will stay linear as the volume goes up while the celestion will start to compress and stop making as much volume as it's pushed. So at that point maybe the 8 ohm EV with 55 watts will actually get louder and cleaner than the 4 ohm celestion with 100 watts? Just a thought, i'm sure you guys will be able to correct that theory if i'm wrong. As to the celestion model, it appears to be a model made for fender because i can';t find that model on the celestion site and they DO put the fender logo on it along with the celestion name.

[Leo_Gnardo]

I DO notice the difference in volume at home volumes. The 8 ohm EV isn't as loud as the stock celestion so i gotta thing it does affect it.

Don't neglect the fact that different speakers have different efficiency/sensitivity. To complicate matters further, even if you had 4 and 8 ohm versions of the same speaker, they would have different efficiency due mostly to different mass of voice coil. Yet even furthermore, speaker statistics are taken over an average of many units, not just a single speaker randomly picked from the production line. The speaker you have may be a couple dB more or less sensitive than the spec. It sure isn't a simple matter of more watts = sounds louder especially when comparing unlike speakers. Yes it's enough to make your head spin. Works for me!

[Enzo]

Yes^^^. There is so much more going on there than the ohms. Take ten different 8 ohm speakers or for that matter ten different 4 ohm speakers. They will all sound different, and be of different loudness. EV doesn't sound like the Celestion? I would be surprised if it did.

[daz]

well, maybe but i will tell you this. I have tried the stock 4 ohm 100 watt celestion, a 100 watt G12t-100 celestion in 8 ohms and the 8 ohm EV12L. The 2 8 ohm speakers were low enough that I had to roll the master well past it's usual stops for a given loudness. I'm liking the other celestion (not the stock one) more than the others and i want to find one in 4 ohms but they're rare. I gotta go 4 tho. i think that it'sa much safer bet a 4 ohm with all else equal is going to be louder and with a SS output section i'd rather get to a given volume with speaker efficiency than turning the power section up more.

[eschertron]

Efficiency may be a big part of the issue, I don't have the nominal specs for the speakers that you are using, so I can't say.
But I do think (per Enzo's post above) that at any given power amp volume knob position, the 8R speakers are loading the amp less, and the amp is 'loafing along' compared to the 4R load. Don't think for a minute that there's 'extra power' represented by the knob position that's somehow being thrown away as waste heat. Do you have to dime the controls to use the 8R speaker that you prefer? No? Then use that speaker and don't worry that the knob is in a different position than for the original speaker in order to get the volume you need.

[Enzo]

Electrically, reducing amp power by half - say 100 watts to 50 - only reduces loudness by 3 decibels, if all else is the same.

Likewise, putting a speaker into an amp with 3db greater efficiency is the same result as doubling the power to the original speaker, all else being the same.

[daz]

My thought is not whether it will get loud enough or where the master must be. Yes, I can get enough volume on 10. The issue isn't where the knob must be or loudness. The issue is that a SS power amp is not the same toneful device like a tube amp that sounds better as you turn it u and it begins to distort. It's the opposite with a modeler. It want's the cleanest power possible and with a mismatched load and 1/2 the power I find it hard to believe the PA's tone is going to be as clean as it would with the proper load. That said i'm leaving it for now and the next time i get together with friends for a jam in probably a couple weeks or so i'll make the decision whether to leave it as is of find a 4. If it sounds great the it's all advantage as you guys say....easier on the amp.

[Enzo]

Proper load. Tube amps want a specific impedance to match the transformer winding. But a solid state amp doesn't work that way. There is nothing less proper about an 8 ohm load on a 4 ohm rated amp. 4 ohms is simply the most current the thing can source at the given output voltage. The amp puts out the same voltage, regardless of load.

[g1]

If you need to wring every last possible watt out of the amp, then go to the 4 ohm.
I gather that is what you want when you say 'cleanest power possible'.
On the other hand, if it's that critical, why not add another 8 ohm cab in parallel which will give you even more SPL gain due to the extra speaker.

[Justin Thomas]

Yeah, that's my answer for everything... more, and efficient, speakers. Especially for bass!

Justin