I just tried an interesting tone comparison, one I’ve never seen attempted. It concerns the search for loud amp sounds at low volumes.
Have any of you ever experimented with speaker attenuators — the passive load boxes that reside between your amp output and speaker input, which let you crank the amp while maintaining a low level from the speaker?
I’ve worked with one model before, a borrowed THD Hot Plate, and thought it performed well. I decided to purchase my own attenuator after several Premier Guitar reviews of large amps. As a small amp fan (not to mention an aging player with fragile ears), I wanted to minimize the aural assault of evaluating loud-ass amps.
But first, I wanted to determine whether it’s legit to evaluate amps at attenuated levels. Does attenuation inevitably alter the tone? And if so, can you compensate for via recording software?
Online opinions about attenuators range from “works like a charm!” to “totally killed my tone!” So I picked up a Swart Night Light and started recording and measuring. (I didn’t compare rival products. I just went with the Swart for its reasonable price, solid online reviews, and dual outputs for driving two cabs. I didn’t A/B it with a Hot Plate, though the results seem roughly similar.)
I direct-recorded a brief guitar phrase using my black Les Paul with Bigsby and PAFs, and then ran it through a ReAmp to my early ’60s Tremoverb, a 35-watt Fender with two 6L6 power tubes. I dimed the volume and left the EQ flat. Tt was insanely loud in my small studio. After recording that, I tracked the same clip again using the attenuator at each of its three settings. The lowest attenuation setting reduced the sound from insanely loud to very loud. Medium attenuation reduced to somewhat loud. Strong attenuation produced a sound quiet enough to speak over. I recorded the results through Royer R-121 ribbon mic. I added a touch of plate reverb, but no compression or EQ. (Though I did normalize the files so they played back at similar levels.) In other words, you hear the same clip four times through a head whose settings never vary.
So did the tone change? Have a listen:
Do you hear what I hear?
IMHO, none of the clips sound particularly great. (Most amps, including this one, don’t sound their best at 10.) But the unattenuated loud sound has some qualities the others examples lack. The attenuated clips have a little less low-mid impact, and the higher-register single notes that sound a bit thin and prickly even on the original sound even thinner and pricklier post-attenuation.
Why, since the amp settings don’t change, and the performance are identical? Mics can respond differently at different sound pressure levels, and the relatively restrained speaker movement alters the result as well. Conclusion: the timbres of the attenuated signals are fairly faithful to the original, but there are slight spectral differences and a bit less body/fatness, especially on single notes.
Then I introduced some additional wrinkles:
