Suhr Reactive Load Vs Fractal Audio X-Load

[James Freeman]

Disabling the resonance limiting resistors in the X-Load brings us closer to the Suhr and an actual Cab, BUT, the resonance is still 90Hz which is not a very accurate tuning for a 4x12.
I remind that Suhr does not have limiting resistors either.

I don't know how safe it is yet with high wattage but I will torture test it with my Valveking, but Suhr doesn't seem to fry amps left and right, so my guess it will be alright.

 

[JiveTurkey]

Disabling the resonance limiting resistors in the X-Load brings us closer to the Suhr and an actual Cab, BUT, the resonance is still 90Hz which is not a very accurate tuning for a 4x12.
I remind that Suhr does not have limiting resistors either.

I don't know how safe it is yet with high wattage but I will torture test it with my Valveking.

View attachment 17346

View attachment 17347

Can you swap components out to adjust the resonance value to something more to your 412 liking?

 

[James Freeman]

Can you swap components out to adjust the resonance value to something more to your 412 liking?

Yes, easily, but out of respect to Fractal I am not going to post my traced schematic.
What I am going to do it un-wind the inductor until it resonates at 115Hz.

edit:
Hmm it's potted quite heavily.
I just can't get over the fact that the X-Load it tuned that way, 90Hz... WHY?

 

[JiveTurkey]

Yes, easily, but out of respect to Fractal I am not going to post my traced schematic.
What I am going to do it un-wind the inductor until it resonates at 115Hz.

That's Our James FreemanTM

 

[James Freeman]

Probably easier to buy a lower inductor on Ali.

 

[James Freeman]

Okay I'm just going to leave it alone but keep the resonance limiter mod.
Lift this leg to remove the resonance limiter.

 

[James Freeman]

Here's the sine sweep response through the Marshall 1987x FX Return at low volume (undistorted).
The amp is set to 16 and 8 ohm depending on the load, and the signal is tapped from the second speaker output jack into a DI.

Both are within 1dB of each other, I am pretty happy about that.
Though the resonance doesn't respond quite like a 4x12, the high frequency slope is very good.

In Axe Edit, if I overlay the 4x12 Brit AX with the X-Load UK, I get this (image below), pretty much exactly what I see with the real measurement.
I think 1x12 cabs are more resonant (higher peak) than 4x12, though I'm not sure about that, I really need a 4x12.

 

[2dor]

Got my hands on a Mesa Oversized 4x12 Straight cab and did a frequency response measurement, then stacked it alongside all the other loads and my other 2 cabs.

Frequency response plots of the following loads & cabs through the Ceriatone King Kong 100w FX Return:

- ORANGE ========> Red Seven Amp Central
- PURPLE ========> St. Rock React:IR
- BRIGHT-GREEN ========> Suhr Reactive Load
- RED ========> ENGL 1x12 cab
- DARK-GREEN ========> Mesa 2x12 Rectifier cab
- BLUE ========> Mesa Oversized Straight 4x12 cab

Pic updated with the legend.

 

[chicken]

what colour is what?

 

[2dor]

what colour is what?

Sorry for that; forgot to snip the legend as well.
I'll edit the post in a few to include them

 

[chicken]

so react ir is more aggressively filtering top end, but closer to real thing at the bottom compared to suhr. intereting.

actually suhr follows 4x12 low slope better? just point is different

I mean I use cab switcher to switch different loads. sometimes useful as a workaround for fake 4 channel amps lile savage.

 

[2dor]

@chicken All done! Thanks for the heads-up; really appreciate it!

 

[2dor]

so react ir is more aggressively filtering top end, but closer to real thing at the bottom compared to suhr. intereting.

actually suhr follows 4x12 low slope better? just point is different

I mean I use cab switcher to switch different loads. sometimes useful as a workaround for fake 4 channel amps lile savage.

Yeah, connected to this power-amp, it does filter out more of the higher end content.
The Suhr, overall, does a pretty good job landing in between them. The Red Seven also has a good looking (lol - just reading what I had typed) curve.

 

[laxu]

so react ir is more aggressively filtering top end, but closer to real thing at the bottom compared to suhr. intereting.

actually suhr follows 4x12 low slope better? just point is different

I mean I use cab switcher to switch different loads. sometimes useful as a workaround for fake 4 channel amps lile savage.

I'd say the Red Seven ends up being a good compromise that should work for most cabs.

 

[2dor]

Cabs and loads tested through the Ceriatone Chupacabra 50W I got today:

- Mesa 2x12
- Mesa 4x12 OS Straight
- ENGL 1x12
- ReactIR
- ReactIR but hooked up to the THRU port on the Suhr Reactive load
- Suhr Reactive Load

What's interesting is the blue line on the plot which is the ReactIR going to the THRU port of the Suhr (this one's hooked to the Speaker port on the amp).

Looks like a lot more high-end content makes it through than if you were to run the Amp directly into the ReactIR.

 

[LeftyLoungeLizard]

After a ton of research, I jumped to the Suhr RL (non-IR, OG version) after almost 2 decades of using the ol' THD HotPlate (hi Ed!).

I now use the Hotplate only for bench work or slaving amp to amp.

IIRC, Suhr tuned his RL to mimic a typical Greenback speaker's impedance curve.

The Suhr RL (non-IR, OG version) sounds great - I'll tap the line out and either go direct into my Apollo to DAW with software iRs (York, Celestion, Ownhammer, Two Notes Wall of Sound VST w DynIR etc), or go into my Two Notes CAB M+, then Apollo then DAW.

 

[jazzarian]

None of the above.
If Suhr got it right, everyone can.
The components are off the shelf speaker crossover parts you can buy anywhere, including Aliexpress.

For example, a 8.5mH iron core inductor and a 220uF cap from Aliexpress will get you the exactly the same resonance response of the Suhr RL.
Throw in a 0.7mH air core for the main inductance, and a few power resistors, a project box, et voila.

https://www.aliexpress.com/item/32953092706.html

https://www.aliexpress.com/item/1005006163631723.html

https://www.aliexpress.com/item/32951716416.html

Suhr RL:

View attachment 16869


I built mine back in 2012, before Suhr or Fractal were offering their version.
I am no businessman, I probably could have made a fuck ton of money.

View attachment 16870

View attachment 16871

View attachment 16872

Yes you should have mass produced it. Nice and compact.

Why is the switch is the "resistor" position? Actually why even offer that option?

 

[James Freeman]

Got a Suhr Reactive Load IR, I run it passively (no power needed), I take the signal in parallel from the secondary speaker output jack through a 25k volume box into a DI box, basically what the passive RL does internally.

The Suhr RL IR is slightly more 'scooped' and has a tighter resonance peak compared to the Fractal X-Load and I think I prefer that.
I've modified my X-Load so it sounds a lot closer to the Suhr now than when it was stock, but the Suhr still sounds a tiny bit less flat (talking about 2-3dB of a difference).
Both are great but when stock the Suhr RL takes the lead.

Peavey 6505 sample.
It has a lot of negative feedback so the difference is minimal between two great load boxes.
Something like a Rectifier on the Modern channel or a Vox with no negative feedback will have more difference.

Suhr RL IR


Fractal X-Load (Modified Resonance)


Frequency response of the loads:

 

[Desertdweller]

Got a Suhr Reactive Load IR, I run it passively (no power needed), I take the signal in parallel from the secondary speaker output jack through a 25k volume box into a DI box, basically what the passive RL does internally.

The Suhr RL IR is slightly more 'scooped' and has a tighter resonance peak compared to the Fractal X-Load and I think I prefer that.
I've modified my X-Load so it sounds a lot closer to the Suhr now than when it was stock, but the Suhr still sounds a tiny bit less flat (talking about 2-3dB of a difference).
Both are great but when stock the Suhr RL takes the lead.

View attachment 28036


Peavey 6505 sample.
It has a lot of negative feedback so the difference is minimal between two great load boxes.
Something like a Rectifier on the Modern channel or a Vox with no negative feedback will have more difference.

Suhr RL IR


Fractal X-Load (Modified Resonance)


Frequency response of the loads:

View attachment 28122

How did you modify the X load?

 

[Carbia]

If I'm not wrong, he changed the value of the bass inductor and resistor.

Anyway, the Suhr RL is more scooped in the mids and brighter in the top end than any real cabinet.
The fact is that's nearly impossible to obtain a realistic curve using just two inductors.

I was working these days in a circuit that sound almost identical to the real thing.

In the graph you can see the curve of a real Marshall cab in blue and my load box in yellow.
The green line is my load box in "open box" mode.

Later I'll post sound samples if you want.

I had a Suhr RL and this one SMOKES it.