Squeeze our impedance? Don't bother!

Sneakypete · #1 03-23-2011, 12:55 PM

Having seen so many threads posted here by bassists (guitar and keys seem to worry much less about it) determined to squeeze their total impedance down to the minimum I thought I'd try some objective experiments. In various sized rooms at home, in the dayjob and in the rehearsal room I've tried, as objectively as I can, to determine the perceived increase in loudness when halving the impedance starting at 16, then 8 then 4 which is the minimum my Trace will allow. Broadly, the answer is that halving the impedance equals a single click on my output level control. 16 ohms at 12 o'clock sounds pretty much like 4 ohms at 11 o'clock. I know, and agree with the argument that you're moving more air and these basic tests were with just the bass on it's own - not competing with other instruments but I'm totally sold now on the idea that more cabs might make you sound better but not much louder!

Selta · #2 03-23-2011, 01:23 PM

Well, a) that doesn't tell you much since who knows what that potentiometer is doing under the hood for a slope. b) we already know this, and it's been discussed over and over. If you want more volume, add speaker area. However, having that 2 ohm capable amp is nice in that you can potentially drive more cabs if you need to.

GrowlerBox · #3 03-23-2011, 02:28 PM

So, how were you halving the impedance at each step? You imply later on that it was by adding cabinets (rather than with "dummy loads"), but this is open to interpretation. If this is the case, the particular cabinets you added are of great importance -- e.g. if you started with a 410 and added a 112, then you're clearly not going to hear much difference in volume, and this difference will be different depending on where you are in the room, for example.

So, kudos for trying the experiment, but more information, and probably more precise control over the conditions would be required before any conclusions could be drawn.

Selta · #4 03-23-2011, 02:31 PM

Quote:

Originally Posted by GrowlerBox

So, how were you halving the impedance at each step? You imply later on that it was by adding cabinets (rather than with "dummy loads"), but this is open to interpretation. If this is the case, the particular cabinets you added are of great importance -- e.g. if you started with a 410 and added a 112, then you're clearly not going to hear much difference in volume, and this difference will be different depending on where you are in the room, for example.

So, kudos for trying the experiment, but more information, and probably more precise control over the conditions would be required before any conclusions could be drawn.

Honestly, adding a 1x12 to a 4x10, I'd be surprised if you could hear the 1x12 at all. You can't just randomly plug in cabs. Well, you CAN, but probably shouldn't.

GrowlerBox · #5 03-23-2011, 02:43 PM

Quote:

Originally Posted by Ray Salamon

Honestly, adding a 1x12 to a 4x10, I'd be surprised if you could hear the 1x12 at all. You can't just randomly plug in cabs. Well, you CAN, but probably shouldn't.

Right, which was kind of my point.

Sneakypete · #6 03-23-2011, 03:01 PM

I started off with a 2x10 that was originally 4 ohm but now rewired for 16. Disconnect the 2x10 try an 8 ohm 1x15 - only slightly more cone area and seems about one click louder. Now add a borrowed 4x10, down to 4 ohm now and it's louder by about a click - not by as much as some would expect. I'm not pretending that this was even remotely scientific and sound is such a complex and subjective matter. No doubt these cabs were unequal in their dB ratings and other technical specs too. Perhaps it's my irrational fear of very low impedances - my old Peavey CS800S power amp would go to 2 ohms (boy do I wish I knew how to get the omega symbol on here!) but i just couldn't bring myself to try it.

GrowlerBox · #7 03-23-2011, 03:06 PM

Fair enough -- so the outcome is that for your choice of setups in your house, there's little to be gained, at least with respect to volume by using bigger cabinets with lower impedances.

Not an invalid point, by any means, but unfortunately, in no way generalisable beyond these fairly limited circumstances. And of, course, it also says nothing about how you liked the sound from each rig.

Selta · #8 03-23-2011, 03:11 PM

Quote:

Originally Posted by Sneakypete

I started off with a 2x10 that was originally 4 ohm but now rewired for 16. Disconnect the 2x10 try an 8 ohm 1x15 - only slightly more cone area and seems about one click louder. Now add a borrowed 4x10, down to 4 ohm now and it's louder by about a click - not by as much as some would expect. I'm not pretending that this was even remotely scientific and sound is such a complex and subjective matter. No doubt these cabs were unequal in their dB ratings and other technical specs too. Perhaps it's my irrational fear of very low impedances - my old Peavey CS800S power amp would go to 2 ohms (boy do I wish I knew how to get the omega symbol on here!) but i just couldn't bring myself to try it.

Again, one "click" on a potentiometer doesn't say *anything*. Especially "about one click".

Sneakypete · #9 03-23-2011, 03:58 PM

I'll just shut up then.

Selta · #10 03-23-2011, 04:17 PM

Quote:

Originally Posted by Sneakypete

I'll just shut up then.

That wasn't my intention. What you did was probably somewhat enlightening to yourself, so I give you Kudos. It's not scientific or anything, but you've opened your own eyes to noticing that more watts won't buy you a lot of volume, and going after the min. load on your head isn't the best bet. Some people take years (or never!) realize that.
What I think you should do, if you can and want to take it farther, is take your 2x10 and play it at the same settings, but wire it between 16 and 4 ohm.
Then, I would, if possible, get an identical 2x10, and do it again with 2x16 ohm loads and 2x4ohm loads.
If you have a way to measure the output of all 4 setups, that would be best.

If you could carry out that, I think you'd find that more cabs will buy you more volume; a lot more than adding in 2x the wattage to the same cab!

JimmyM · #11 03-23-2011, 04:42 PM

Quote:

Originally Posted by Sneakypete

I'll just shut up then.

i'll agree with you...the chase to slam tiny cabs with 4 ohms of ridiculous power has gotten out of hand and is really pointless. your methods might have been flawed but your message is right on.

okcrum · #12 03-23-2011, 04:49 PM

Quote:

Originally Posted by JimmyM

i'll agree with you...the chase to slam tiny cabs with 4 ohms of ridiculous power has gotten out of hand and is really pointless. your methods might have been flawed but your message is right on.

I agree. I predict it will help sell a heckuva lot of replacement drivers, though.

Downunderwonder · #13 03-23-2011, 09:22 PM

Since we're talking unscientific results vs maths here's a data point:

Trace 250w with one cab = loud, maybe 150w max into 8 ohm
Trace 250w with two cabs = really freakin' loud, full potential employed

seamonkey · #14 03-24-2011, 12:51 AM

Quote:

Originally Posted by Sneakypete

I'll just shut up then.

Why not take some of this valuable input you've been given and go back and test again? Use a PC and mic for a meter. Science is all about repeatable accurate results. You have a hypothesis - go scientifically test it.