You're going the wrong way. If you connect one 8ohm speaker to an amp set to 8ohm output that's what you have. If you chain another 8 ohm speaker in series to the first one you now have a 4 ohm setup.

Impedances add in series. You are thinking of parallel.

foul_owl, post: 355080 wrote: I have a simple question. I am going to build one of these for recording:
http://www.amptone.com/diyisobox.htm
I greatly prefer the sound of 16 ohm loads over 8 ohms.
I was thinking I would get a 2x12 and use two 8 ohm V30s in series. But how would the sound compare to using a 1x12 with 1x16 ohm V30?
Only micing one of the speakers here with an SM58. High gain guitar amp.
Thanks!!

What type of amp are you using and what's the nominal power output and impedance?
When you say you prefer the sound of 16ohm loads over 8, what is it about the sound you prefer?

foul_owl: mea culpa. I was momentarily confused. Too much Wagner this morning.

Jack:
Do you prefer Wagner in 16ohms or 8ohms?

LMAO!!! Tonight I just want all the right notes with dynamics and dictation perfect articulation..........In this case the orchestral reduction has us reduced from 8(horns) to 4(horns) (Walkure overt). I'll start out the night with mucho resistance and end with zero! And then we'll throw Symphony Fantastique on the end for fun.

4 horns would be 8 horns in parallel
But if you put the 4 horns in series you'll get 16 horns
And I'm pretty sure that would sound better!

Especially if it's the London Horn Sound recording.

djmukilteo, post: 355099 wrote: What type of amp are you using and what's the nominal power output and impedance?

Amp is 120 watt, high gain of the Soldano or ENGL variety.

djmukilteo, post: 355099 wrote: When you say you prefer the sound of 16ohm loads over 8, what is it about the sound you prefer?

Good question! As far as I can tell, 16 ohms sounds much thicker and more detailed. More complex. Whereas 4 ohms, by comparison, just sounds loud, and sort of dull, not as complex I guess. 4 ohms is good if you are going for LOUD. To be honest I have never done the 16 ohms vs 8 ohms comparison, but I would imagine that 8 ohms is somewhere between the two.

Are you building a DIYbox and a speaker cabinet?
if so what are the specs on the speakers your planning on using?
Does the amp have 4/8/16 ouputs?
Is the amp rated at 120W into 8ohms?

Attention!!

Do not connect a higher impedance load to a Tube amp then written in its specs.
If you do this with high volume over some time, it will kill your tubes....and never switch it on (standby =on) without speakers connected...
Whereas, shorting out a tube amp is just pushing the valves to their highest output and dose not instantly harm them. I am not saying it is healthy, better just don't.
;-)

When using a solidstate amp don't deceed the indicated impedance, or it will grill your transistors in a while... Not to short-circuit it is know, I suppose.
So, it is just reverse rule between tubes and transistor amps...

Always keep in mind, that the sound of a speaker is not really all about its impedance, but depends on its age and brand much more.
To work an amp with the specified impedance is widely considered to be the best technical solution and extends longevity of the device.
I'd rather go through the various speaker chassis to find the best sound for my purpose. AND: a speaker sounds different in a closed compartment like this...

I have the speaker cabinets blowing into a hidden large absorber which is a build-in acoustic feature of my recording room...
So, I do not have any experience with iso-boxes and, therefore, can't comment on any suitable speakers..

Have you tried using one of those Reflexion type vocal screens mic pointed at your guitar amp?

Using the isobox method is really no different than building a full vocal booth for a singer..in your case your trying to control the acoustics (the box) the source (speaker and amp design) and then the mic on top of all that.....

Another thought on your amp/speaker(s) combo is that using multiple speakers would be much more difficult to achieve a smooth sound field...multiple speakers in a guitar cabinet are great for stage where volume and large dispersion is needed but for studio recording, you would have better results with a single cone...the impedance of the speaker should closely match the specified efficient output of the amp at its rated power output...if that happens to be 50W into 8 ohms then I would use that....using the amplifier at its most efficient design is always best....the speaker is your weakest link here....tailoring speaker design and its construction to the specific guitar tone your looking for is far more important.....you don't need 120W in a box pointed directly at a sensitive microphone to achieve color and tone....

The reason I am building an isobox is due to neighbors. :( It is getting made no matter what.

I also realize that I don't need a 4x12. Just looking at a 1x12 or 2x12 at this point. Probably going to go with the 2x8 ohms in series I think.

I'm wondering why you're leaning toward the 2x12 if it's primarily for recording purposes. I think it simplifies recording life it's it's a single speaker cabinet - maybe that's just me. It seems to me, there are fewer phase issues from the single source.

And if bothering the neighbors is a concern, it would follow you don't need the extra thrust of another 12".

Pretty much the only reason is because of power handling. Recording a 120 watt amp, 2xV30s can handle 120 watts. Also not sure about geometry of the iso box too.

Most studio/recordings are made with much much smaller amps. By a factor of 10 even. For recording purposes, you can get great tone and sound from a 5 or 10 watt amp, too.

I don't know what kind of music you're specifically into, but some of the greatest rock recordings of all time were made using dinky little amps in the studio. For instance, if you saw the little Supro amp Jimmy Page used for a lot of the Zeppelin stuff at a garage sale, you'd think it was some kid's first practice amp from Sears and walk right past it.

Oh yes, I know these things. But I am only interested in capturing the sound of this particular amp that I have in my possession, rather than trying different amps. Thanks for the help so far!

I guess, phasing is not such a problem in the iso box. Although, it is not necessary to run a 120 watts amp at 120 watts full blast.
Those valve watts are incredibly loud when you want to get a decent tube sound. You will have to box it in, anyhow, I guess...
Tell us about your experience with it...

Yeah absolutely please take some photos and post some audio clips of your results...foul_owl
It always helps others who are experimenting to see and hear the results of projects like this

I would love to post my results. Can't promise anything soon, but maybe in a few months!