Impedance curves ?

Joe88 said:
Does anyone have a list of the impedance curves. Like what models they actually represent? Any help would be appreciated. I clearly understand a few but others I have no idea.
Click to expand...
Speaker Z curves11/21/2021
11 x 8 Champlifier241 x 15 Vibrato Verb474 x 12 Brit 800
21 x 10 Princetone252 x 10 Super484 x 12 Brit AX
31 x 10 Princetone Rev262 x 10 Vibrato Lux494 x 12 Brit Greenback
41 x 10 Princetone SF272 x 10 Band Commander SRO504 x 12 Brit TV
51 x 12 AC-20 DLX282 x 12 Bassbuster514 x 12 Citrus
61 x 12 Ast BV25292 x 12 Bassguy524 x 12 Euro
71 x 12 Brit G12H55302 x 12 Class-A 30W534 x 12 Friedman
81 x 12 Brit G12H75312 x 12 Double Verb544 x 12 Hipower
91 x 12 Brit G12M322 x 12 Double Verb SF554 x 12 PVH 6160
101 x 12 Brit G12T332 x 12 Godzilla564 x 12 Recto Large
111 x 12 Class-A 15W342 x 12 Guy Tron Alnico Blue574 x 12 Recto Slant
121 x 12 Deluxe Verb352 x 12 Hot Kitty584 x 12 Recto Small
131 x 12 Deluxe Verb RI362 x 12 Jazz 120594 x 12 Recto Straight
141 x 12 Dirty Shirley EV12L372 x 12 Lead 80604 x 12 Rumble
151 x 12 Eminent382 x 12 Match Chief614 x 12 Solo 100
161 x 12 Jr Blues392 x 12 Recto624 x 12 USA Lead
171 x 12 Tweed Alnico Blue402 x 12 TX Star63Load Box LB-2 UK
181 x 12 Tweed C12Q414 x 10 Bassguy64Load Box LB-2 US
191 x 12 Tweed Emmi424 x 10 Britt JM4565Resistive Load
201 x 12 USA Ext EV12L434 x 10 Super Verb
211 x 12 V30444 x 10 SV Bass
221 x 12 Vibrato Lux454 x 12 5153
231 x 15 Portabass464 x 12 Basketweave
 
mr_fender said:
Most likely the 4x12 Brit 800. JCM 800 1960 cabs were typically loaded with G12T75's.
Click to expand...
Yeah that is prob the best one to use according to that info

Only thing bothering me is,

By checking the factory preset that have the 4x12 Brit 800 as the default speaker imp curve they use another IR that has different speakers , Factory Bank 1 Preset 10 Brit 800 , uses Factory 2 Cab #757 + #758 which are G12-50GL according to the wiki


But I get the whole use your ears and not the name thing
 
Anyone know the difference between Recto Small and USA Lead?
I would think the USA Lead is the small traditional sized Mesa cab?
 
ApocalypticKatana said:
Yeah that is prob the best one to use according to that info

Only thing bothering me is,

By checking the factory preset that have the 4x12 Brit 800 as the default speaker imp curve they use another IR that has different speakers , Factory Bank 1 Preset 10 Brit 800 , uses Factory 2 Cab #757 + #758 which are G12-50GL according to the wiki


But I get the whole use your ears and not the name thing
Click to expand...

I use the 800s a bunch, and have grown to dig both the Ownhammer Lynchback 57/121 IRs together (757, 759),
or the Leon Todd LT TV Mix 7 IR.
 
I thought this might be helpful and appreciated in this thread.
https://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1427734
FractalAudio said:
A little trick you can do to get the "bounce" of high MV without the muddy bass is to reduce the LF Res value on the Spkr tab. This will reduce the amount of bass clipping in the virtual power amp allowing you to turn the MV up. You can also reduce the HF Res to reduce the amount of treble clipping.
Click to expand...
I have made the mistake of using the impedance curve as an EQ.
I would cut some treble and feel like some of the "sparkle" had disappeared at the same time.
It is best to look at the impedance curve for the distortion/saturation frequencies of the power amp.
it is better to cut frequencies with an EQ -- perhaps the output EQ.
This is especially true for the resonant frequencies.

Likewise, if you want more or less distortion at the resonant frequencies
-- more high treble distortion, more bass distortion,
you may want to adjust the impedance curve.

The "ideal" impedance curve might be different at different V/MV settings.

I think this may have been one of several factors for the "sweet spot"
in volume levels for the old analog amps.

I hope this helps.
I have been trying to gain some understanding concerning amp parameter adjustments.
I am always curious about exceptions -- and things I missed.
So, please feel free to add any other insights.
 
Last edited:
Postretro said:
A thought this might be helpful and appreciated in this thread.
https://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1427734

I have made the mistake of using the impedance curve as an EQ.
I would cut some treble and feel like some of the "sparkle" had disappeared at the same time.
It is best to look at the impedance curve for the distortion/saturation frequencies of the power amp.
it is better to cut frequencies with an EQ -- perhaps the output EQ.
This is especially true for the resonant frequencies.

Likewise, if you want more or less distortion at the resonant frequencies
-- more high treble distortion, more bass distortion,
you may want to adjust the impedance curve.

The "ideal" impedance curve might be different at different V/MV settings.

I think this may have been one of several factors for the "sweet spot"
in volume levels for the old analog amps.

I hope this helps.
I have been trying to gain some understanding concerning amp parameter adjustments.
I am always curious about exceptions -- and things I missed.
So, please feel free to add any other insights.
Click to expand...
Good one, thanks for sharing.
 
Robben Ford uses a 2x12 cab with Celestion G12-65's. I don't think there is a 2x12 Celestion G12-65 Impedance Curve. I would get the correct speakers -- that also sound right to you. Then try all of the 2x12 Impedance Curves. Pick the one that sounds closest to you. Then see if slightly sweeping the Low Frequency peak to each side gets you closer to what you want. Then adjust the LF peak up and down. See if that gets you closer. After that, work on your preset sound for a while. And then, revisit that LF peak and see if it is still good for you. If not, see if some more small adjustments up/down and sideways wiil make it sound more like Robben Ford. That's what I do, anyway. Someone else might have better advice.
 
Mariano said:
This is interesting, what would be a match for a mesa 1x12 mini recto with Celestion Vintage 30?
Click to expand...
Well, there is a "1x12 V30" Impedance Curve. I don't know that any IC's are exact or perfect matches. A lot of players and studio engineers have a favorite cab due to the cab's unique resonances -- even though the size and design is similar to many other cabs. Robben Ford has a favorite 2x12 cab. A black one. It is not the matching cab for his Dumble. He still prefers it for the sound. Mikko has a favorite Mesa 4x12 cab. It is all torn up but he prefers the sound of that cab -- to the point of searching for it and repurchasing it after he sold it. I don't have their ears. But, I still have my preferences.

The main reason for matching an IC by speaker type, speaker count, cab size -- and maybe even brand -- is to have a good starting point for capturing a certain artist's sound. It is always a good idea to try adjusting the LF resonant peak's frequency and gain, anyway. It can help to get closer to an Artist's sound or to find your own sound. The LF peak makes a very noticeable difference in the IC and the sound. A LF resonance can also cause flubbiness if the peak is too pronounced and the power amp is driven hard. I have no problem with trying out a 2x12 IC, or 1x12, with a 4x12 IR -- for my own needs. If you don't like the sound of a particular IC, and you can't adjust it, then it isn't the IC to use, as far as I am concerned.

I am still learning here. There is more to all this. I am sure.
 
I think the speaker impedance curves should have their own wiki page like this one

https://wiki.fractalaudio.com/wiki/index.php?title=Cabinet_models_list

Yes, I know some of them are obvious but it should help , if we’re trying to accurately digitally represent a certain rig , we should know what the impedance curves speakers really represent so we can match it to an IR using those speaker configuration
 
Is there any more information on what cabs and speakers the impedance curves represent? For instance, I'd love to know if there is a curve similar to a Marshall oversized with K100's (Mode 4).

ApocalypticKatana said:
I think the speaker impedance curves should have their own wiki page like this one

https://wiki.fractalaudio.com/wiki/index.php?title=Cabinet_models_list

Yes, I know some of them are obvious but it should help , if we’re trying to accurately digitally represent a certain rig , we should know what the impedance curves speakers really represent so we can match it to an IR using those speaker configuration
Click to expand...

This would be immensely helpful - yes there's the argument of "use your ears", but if we know what the load is based on, it helps to use the IR's with predictably realistic results.
 
You must log in or register to reply here.
Back
Top Bottom