orderd a quad of G12H-75 Creambacks

[peterdenny]

Hey Bandit just so happens I took pictures during the process to make sure I didnt mix up wiring etc. These are 2 new 8ohm CB75 speakers I purchased specifically for the cab. The 16ohm are sitting in the garage after I pulled em from combo until I decide if they will go into the 2x12 which they probably will. See below. I took a close up of the original wiring to avoid fat fingering the wiring. To me I think its ok. Peter

Original Speakers in cab:

Closeup of wiring of two being replaced. Top L\R:

Speakers post replacement:

 

[afu]

8 and 16 makes each side 5.33 ohms. That isn't too far off the 4, but it runs slightly cool and can make the middle freqs more prominent. It also reduces power, which may affect lows. Just be careful not to run a single head in stereo, because it would reduce to nearly 2 ohms.

A single amp going in mono is 10.6 ohms. Using the 16 tap cuts mids. Using 8 ohm taps in the stereo rigs does the same as this.

http://blog.hughes-and-kettner.com/ohm-cooking-101-understanding-amps-speakers-and-impedance/

 

[bandit2013]

Wire hook up of the speakers looks correct. It is hard to say what is up with the change when using the 412 as a stereo cab.

If you had luck doing this before with the Road King Combo and the Marshall, perhaps it is something in the hook up that is defeating the signal. Does this happen with the dry signal using both amps connected in stereo? or is it related to an effect that may be causing the problem.

 

[peterdenny]

8 and 16 makes each side 5.33 ohms. That isn't too far off the 4, but it runs slightly cool and can make the middle freqs more prominent. It also reduces power, which may affect lows. Just be careful not to run a single head in stereo, because it would reduce to nearly 2 ohms.

A single amp going in mono is 10.6 ohms. Using the 16 tap cuts mids. Using 8 ohm taps in the stereo rigs does the same as this.

http://blog.hughes-and-kettner.com/ohm-cooking-101-understanding-amps-speakers-and-impedance/

Afu, all the speakers are 8 ohm. I bought two new ones for this cab. I didnt install the 16ohm.

 

[afu]

LOL. OK. I missed that.

 

[bandit2013]

I would check to see if your effects has a phase shift on one output. If not, I wonder if there is a buffer than can shift phase to prevent signal cancellation.

If you speakers were out of phase, you would notice that running the cab in mono mode. You probably would not notice the phase variant if you were using two separate cabs that can be placed apart from each other.

Let us know how you made out with this as I am sure others may have encountered this. Perhaps this weekend I will move my 412 back into the room, pop the jack plugs out and see what happens between the Mark V and JP. I know for a fact the Mark V will be out of phase when using the FXloop active mode as it was indicated in the manual. Out of phase relevant to what? so I can try with FX loop on and off. I have a few stereo pedals I can use as a buffer for the front end so may be worth trying. My other 412 cab was modified, so there is only two jacks, input and output and no longer has the stereo mode as I had assumed that the switch was not making contact when using mono mode due to age of the plastic button on the end of the switch arm.

I was planning on A/B comparing the Mark V to the JP so it was part of my plan anyway.

 

[peterdenny]

Ill try to run a lot of tests this weekend. Each sounds fine separate and ill need to plug each head in to the 8 ohm 4 speaker and compare everything. Ill reply back once I have tested more.

 

[peterdenny]

Spent a bit of time doing a tad of tracking today but not enough bc was running too many errands. What I can tell you is that with my new MA-200 mic the differences over the Fathead ribbons are quite noticeable. I will say that running the cab in 8ohm all speakers sounds fine. Running them split independently sounds just fine. Combining the two and it goes to hell. So no biggie, i just track independently and I run the heads autonomously. I find it a strange thing though bc I had hoped to take advantage of the two amp voices in a single tracking take. But seriously that is small **** for me. I tracked with the Mojave mic today with the creamback. I flubbed a lot of parts since I am out of practice on that one song but I need to do some comparison with the V30 to that. Wish I had the cash for two Mojave but they are pricey. I did however do two fatheads each on a different speaker and the CB75 is definitely brighter but not massively so. These have yet to break in and I think the two speaker mix is a nice compromise. love the cherry head. its the tits! I need to spend some time dialing in pres and stuff to find the sweet spot but so far so good. Anyone have a preference which speaker to mic if you are only doing one?

 

[bandit2013]

Peter,
I was wondering if this would help you with your issue trying to run two different heads into one cab using stereo hook up.

http://www.suhr.com/suhr-guitar-pedals/buffer/

I have not gotten around to running two amps though my 412 yet. I was hoping to get to it sooner or later but have been on the sofa for a bit under the weather due to recovery of minor oral surgery I had last week.

 

[peterdenny]

Im not sure that would do anything. I looked at it and that seems more for loss from long cable runs but Im using 10' instrument cables and 1.5\3' speaker cables. Its not really a big deal. I played the JVM with all 4 via 8ohm over the weekend and it sounds similar to the half stereo 4ohm. Its only when I combine both amps it seems to phase out. Its not really a big deal I can track twice. I was just confused with the scenario but I didnt hork the wiring so I am just going to move on and call it a quirk.

 

[bandit2013]

I posted the link to the buffer because it has a 180degree phase shift output (also isolated). So if one of the amps is out of phase, the signal passing through the phase shift into the input of one amp should correct for the phase issue if there is one. This in theory would correct for one amp being out of phase with the other. There may be some other buffers out there that will do the same, this was the first one I found.

I may actually get one of these things if and when I decide to run stereo.

 

[peterdenny]

Im curious what happens if and when you run stereo. Dont suppose you also have access to a Marshall? I dont know if two mesa heads would behave the same. Its an odd situation.

 

[bandit2013]

I do not have a Marshall. But I do have one amp that will be out of phase with my others when the FX loop is used. (Mark V). I will see what I can do this coming weekend with the OS Recto 412 that has stereo connections. I was planning on comparing the JP to the Mark V though the same cabinet and that would be one way to do it in order to have a common reference point. It is just a matter of when I can get to it.

The buffer will do two things. For one it has an isolated output that will decouple the two amps as it uses a transformer for isolation on one of the terminals. I have yet to figure out how to run two amps simultaneously with one signal source without noise, especially when one is placed into standby. Unfortunately I do not have the buffer as I normally just run one amp at a time. It is cool to bi-amp a signal though (through each preamp section and power section). To be honest, I have not noticed a phase issue with the Mark V as described in the manual when I ran it with the RA100 or Roadster but each using a separate cab.

 

[SamuelJ86]

Just an FYI bandit; I had pretty good results running my strymon pedal in front and sending the stereo outs to my V and my JP2C inputs. I wasn't able to play too long or crank it up too loud, but I seemed to have no issues. I don't think the amps pair up well together, or at least I haven't found good settings yet. Need to do some more tweaking. I tried slaving my JP2C into the V but couldn't get any sound out of the V. Hmmm... Need to work on that too. But the strymon pedal was a simple solution to get both amps going at the same time. 8)

 

[bandit2013]

You can slave into the Mark V. Not sure if a dummy plug needs to be inserted into the send jack. Also need to use the FXLOOP active as there is a hard bypass around the loop jacks when it is off, you will also need to turn on the FX loop on the footswitch or change the control position on the back panel.

As for blending Mark V with the JP, not sure if it would sound spectacular. I have done so with the Roadster and the Mark V, and Mark V with RA100 but not though the same cab though. I have used the Mark V as reference for Peter as I do not have a Marshall, but the Mark V should be out of phase with the loop active. Would like to see if the combined signal of the Roadster would cancel out the Mark V when the source is the same for both amps. Manual recommends that amp placement must be at a minimum of 8 feet from other amps in the same frequency range as there could be cancellation of some frequencies due to the inverted signal of the FX loop (out of phase). The Buffer suggestion would be to do a phase shift on one of the amps in question for Peter as he is attempting to combine a Marshall and Roadking using the stereo jacks on the 412 Recto cab.

Last time I had used two amps though the stereo jacks on a 412 cab was with a Mark III and Mark IV about 14 years ago. That sounded ok but preferred to use separate cabs for stereo effect using two amps.

 

[peterdenny]

BTW I am not using any fxloop here at all. I have a 4ohm out from the mesa and marshall split evenly into the 4x12. FXloop doesnt come into play at all.

 

[bandit2013]

Peter,
I understand that. However, I suspect the Marshall may be out of phase to the Road King when running the two amps in tandem. The only way I can confirm is to use my Mark V with the FX loop Active as it becomes out of phase with other Mesa products do to the method how the FX loop is fed inside the amp as it causes signal inversion or phase shift. I will mix the Mark V with another Mesa amp, perhaps the Roadster which is closer to the Road King. I will probably have to try it with the FX loop enabled (switch on the back) and then turned off. Not sure what the end result will be when running thought he same cab. I will also drive both amps with a common signal from a stereo pedal (Delay) either on or off as I have used this before to run two amps at the same time. I was responding to Samuel's comments on the Mark V.

I do not have any other means to get an amp out of phase to the other. If the cabinet sounds weak or lacking when using two amps though the same cabinet but sounds normal with only one in use, that would be a phase issue between the two amps. If both amps are receiving the same signal and if one is out of phase, the end result will be cancelled waves or frequencies that are opposite to each other, and frequencies that are not or are different due to the difference of tone or character of each amp will be heard. This is not a bad thing about either amp, and may be more common than one would think. If both amps were in phase with each other, the end result would be the desired effect without tone loss or cancellation of sound of competing frequencies.

The exact same thing would happen with a single speaker. Once in the cabinet, the sound does not get mixed with the back side of the speaker so it sounds full and loud. Remove the speaker from the cabinet and send the same identical signal to its terminals and the stronger frequencies (generally the low end) will be lost due to sound waves canceling each other that are radiated from both sides of the speaker. Sound from the back will be 180 degrees out of phase with that from the front of the cone.

If this is the case, all you need to do is introduce a phase shift of the signal feeding into the input of one amp only in order to minimize the cancellation of the main body of the signal after it has been amplified and sent to the cabinet. The buffer is one item that can invert the signal or shift its phase.

 

[bandit2013]

Since I had my stitches removed today, Dr. said I had no lifting restrictions so I was able to move the 412 cab and Mark V back into the other room.
Hooked up both amps and balanced the volume between them. I did not notice much of a reduction when the Mark V was in phase or out of phase. It just seemed a little quieter when the amps were out of phase (Mark V effects loop active and turned on with nothing in the loop = hard bypass). I used a Line6 DL4 to run the two amps with the same signal. Even tried the Delay. Mark V does not seem to produce as much bass as the Roadster so perhaps there conflict was not competing at the bottom end of the spectrum. Midrange was notably softer when out of phase vs in phase, tremble was where I noticed more of a difference. Perhaps the Mark V is not that much of an influence for the cancellation effect but there was something to write about anyway.

Not much help if any.... sorry I do not have a Marshall.

 

[peterdenny]

Looks like Lightning just struck twice. GC online has a red RK2 half stack. I just purchased the 4x12 to match my cherry head. Ive still got the 16ohm CB75 speakers and so if this cab checks out I will sell the recto cab after replacing the V30s and switch to this. I like the idea of the dual CB75 vs C90 that i really dig. So looks like my rig just changed again and shortly I hope to have a new pic. I will definately pull the v30s on that cab. Probably sell the 2 8ohm 75w ones that are basically new. Peter

 

[bandit2013]

That works... I am happy you made something happen. If you have room for two cabs, why not use one with the Marshal and the other with the Roadking ?

I finally experienced a mix of MC90 and V30. Recently got a horizontal 212 cab and replaced the non-stock speaker in my Mark V with a new MC90. Had to hear what that sounded like combined. WOW, that was awesome. Those two speakers blended quite well and much better than I expected. I hope I get more mileage out of the MC90 as I had issues with those in the past but no longer have the amp that kills speakers. I am debating on moving the Creambacks to a traditional sized 412 cab and stuff the EVs back into the old recto cab. I think I killed the resonance of the cabinet with the extra bracing that was needed to kill the baffle vibrations. EV would probably work better with that mod. I also put a pair of the Creambacks in my RA100 combo. This is where it all started from. I like having options as each speaker has a different character to it. Cream back is more vintage in character than the V30. Now I have to figure out what to do with the Cream 90W Alnico speaker (may stuff that in a 1x12 cab)