Celestion G12M Greenback Speakers with GM36

I'm thinking of buying a pair of Celestion G12M Greenbacks for use with my GM36. I see a post where bordonbert uses a 4x12 cabinet with a partition and a switching arrangement to switch between a pair of G12M Greenback or a pair of G12H speakers. My concern is the G12M Greenback is only rated at 25 Watts so a pair would be 50 Watts which is close to the amps output.

Anyone using a pair of these speakers with their GM36 cranked up and finding them okay?

The Celestion G12H-75 Creamback is a more modern take on the original Greenback but with a higher 75 Watt rating, is it the same sound, is anyone using these?

Seems strange that H&K use the Celestion Vintage 30 in their 1X12 and 2x12 cabinets where most people find them far too harsh for use with the GM36.

After buying my GM36 around 3 years ago I have been using a pair of Marshall 1912 cabinets from my previous setup. For some strange reason the speakers in this cab are bass speakers! They are Celestion G12B-150 (150 Watt), I find them very "boomy" and have converted one cab to open back by making a new back panel with the middle third of the panel open which has improved things slightly. The Frequency Response for these speakers is 60 - 4,000 Hz which is nowhere as good as most guitar speakers which are in the 70 - 5,000 Hz range.
There will be a pair of these for sale soon (not that anyone will want them) when I make my choice from the "minefield of options" and buy some replacements.

Any thoughts anyone?

Hi GD.  That's a good question and it was one I was aware of when I set up my 4x12" that way.  The GM36 is just that, a 36W amp.  It won't pose any problem to a pair of Greenbacks.  The speakers are pretty generously rated too.  I have had my GM36 pretty much flat out and I heard no signs of distress at all.  I don't know whether you have seen the post but I also run my setup with a Marshall JVM205H 50W.  I can also confirm that I have that amp pretty much cranked and get no problems with it either.

The only time I would foresee that there may be an issue is if you are using a bass or baritone or maybe heavily dropped tuning and you are increasing the very low bass content which contributes more to the overall output power level.  The GMs are set up to not give too much out of that area anyway.

For what it is worth I tested the heating effect of running the amps cranked into a load.  I sometimes use a trick for smaller venues where I have a 25W 8R power resistor mounted on a small square of aluminium with a flying lead to a jack plug.  I put it in parallel with the 8R speaker pair with the two of them into the 4ohm sockets of my Marshall.  That way the speakers are only getting 25W, the resistor is wasting 25W, the amp is cranked to get tone and the overall impedance matches at 4R.  I have done the same trick with a 16R power resistor and the full 4 speakers at 16R into the 8R sockets as well.  The 25W resistors being fed what you would think is 25W don't even get warm!

The thing is that music is so dynamic the huge majority of the time is spent at lower than max power levels anyway.  The overall electrical power output when you play is always much less than the full power of the amp which represents the maximum peak power it can give.  Testing on these issues is done with sine waves where the output power can be made constant maximum and continuous.  That isn't representative of real life playing, (unless your musical taste is pretty weird).  Your playing may peak at the max but it isn't continuous sine or square wave power.  And guess what, the speaker coils, the part most vulnerable to overdriving, are heated by the overall power they take in not the peaks which they will cope with easily, (as long as they don't peak way too much over their limit).

If you were to play with maximum clipping, (pretty much a square wave), with a style where there is absolutely no silence at all at points in your sound, (a few genres come to mind   ), then you may be building up a problem but I would think it is very unlikely.

Maybe others would come in here and confirm this or put it straight?  Your experiences may be different to mine.

I have a TM Deluxe 20 that I'm using with a Marshall slant 2x12 cab. It has the Celestion Seventy 80s in it. Although I've heard reviews that those speakers are harsh, I'm getting a nice mellow tone with this combination and the speakers aren't being taxed at all. With regard to a 50W speaker combo against the 36W GM, I'm thinking you should be fine! Rock on!

Took the plunge and bought a pair of Celestion G12M Greenbacks for my Marshall 1912 cabinets.....what a different in the sound! Much"crisper" sounding, more "classic rock". You know what they say......when it sounds good it makes you play better. Best £170 I've spent!