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Thread: optimal load vs higher load with SS amp ?

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    Old Timer daz's Avatar
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    optimal load vs higher load with SS amp ?

    I asked a related question about this before but this one is a bit difference. I have a SS fender amp that uses a 4 ohm load and because the stock speaker blew i put a 8 ohm speaker i had in it. Now when i turn it up to band volume it's right at a point where i think the power amp starts crapping out due to low end. I'm not using a lot of lows either, just what i typically use with any amp and use regularly at high volume with my other SS amp. The question is, will the amp tend to crap out like that a lot easier due to the higher load ? In other words, if i bought the same speaker that i put in it in a 4 ohm version would i be able to turn it up louder then where it now craps out w/o that issue? I have another amp thats actually my main amp i use with the band but i would like to use this other one at times, but if a 4 ohm speaker doesn't help at all or much i want to know before i toss away 100 bucks. I'll just keep it as a home amp otherwise but i;d be happy to spend the money if it gets me say another 10-15% more volume before it craps out.

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    Senior Member nevetslab's Avatar
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    If you had installed another speaker identical to the original that blew, you'd be back to where you wanted to be, I think. The information that's missing thru all this is...we have no idea what the sensitivity of the speakers are, and you've now introduced a new unknown...an 8 ohm speaker of a different mfgr, so the amp won't put out as much power, for one, and, no doubt it's sensitivity to a given power is the other. On speaker spec sheets, you'll usually find a sensitivity spec, that's made with 1 W applied, maybe on a large infinite baffle (large panel) or in a specified cabinet, measured 1 meter from the speaker, given as x-dB @ 1W/1M. Trying to find that info from our original speaker may be unavailable.

    So, no real way to say what you'll end up with, deviating from the original. Is the original speaker still available? If not, you might check about getting it re-coned, if a like-original cone kit is available for it.

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    Logic is an organized way of going wrong with confidence

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    A SS amp is essentially a voltage source and its max. output voltage is limited by its internal supply voltage(s). If Vmax is the max. RMS output voltage and R the speaker impedance, the output power is given by Vmax˛/R. It follows that doubling the speaker impedance halves the output power.

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    Old Timer J M Fahey's Avatar
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    Doubling load impedance about halves RMS output power, period, so it will sound weaker and easier to overdrive ... which in an SS amp is not a good thing.

    If, besides that,new speaker is less efficient or muddier, it complicates things further.

    We can imagine what the original Fender was, most certainly a "Jensen type" (simply because bthat´s whatbthey always use) or a similar one made by Utah, Oxford, Pyle, CTS or Eminence, all much alike to each other.

    Now "a speaker I had" means nothing, so far.

    If still available, post a picture of the old one, any codes it has, and same about the "new" one, for a somewhat accurate answer, otherwise just roll some dice, same hit or miss probability without data.

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    Old Timer daz's Avatar
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    The stock is a celestion specially made for the fender GT modeling amnp that according to a celestion rep is supposed to be a slightly higher power handling version of the 70/80 speaker which has a 98 SPL and is 80 watts. The G12T100 i put in it's place is a 97 SPL 100 watt speaker. I just want to know whether with all else being equal, (regardless of the fact it's not) if you took 2 of the same model speaker one at 4 and one 8 and in this amp the 8 had the low end doing what i described, what would the likelihood be that the 4 would get noticeably louder w/o that issue? Sorry about the word noticeably, but obviously theres no way to explain in text how much louder i need and the fact is i don't expect a definite answer, just your best guess. I have an EV too and it does this with that at about the same volume.

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    Old Timer J M Fahey's Avatar
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    Ok, I thought you were talking about an older and standard Fender amplifier, most probably having some Fender labelled generic Eminence.

    The GT is a "higher class" product, so they put a (more expensive than generic Eminence) Celestion.
    The G12T100 is a good speaker, no doubt, but it´s somewhat muddy (they call it "warmer ) compared to others and you are losing 50% power because of the impedance mismatch.

    Best way to sell your cake and eat it would be to put a Celestion 70/80 **8 ohm** inside the amp so it will never burn but you´ll get the original sound back (in my book "special versions" tend to be same speaker with a different label ) PLUS an extension cabinet with another 70/80 , again 8 ohm.

    You have exact same timbre as before, twice the power handling, you will move more air, all for the price of carrying an extension cabinet.

    Extension cabinet can be quite light (make it out of 12mm / 0.5" plywood), you can (should) put your current amp on it (make it same width) and worst case make it semi open backed, cover speaker back with chicken wire stapled all around so nothing can touch the cone back and use it to carry cables, your tuxedo, and anything else which needs carrying around.

    Sadly there are not many 4 ohm guitar speakers around, of those not many sound like the original one and even less have higher power handling, so.... choices are very limited.

    Pity the original one didn´t stand it.

    The EV is a VERY good speaker but being 8 ohm you are still losing 50% power.

    And it´s loud and efficient ... but the Celestions are also, so no big improvement compared to them, as you noticed.

    What I suggested is somewhat inconvenient but definitely an improvement over then original setup (single 4 ohm speaker), and to boot it will sound "bigger".

    Edit: found *one* guitar speaker about matching your requirements: 12" 100W , efficient/loud, and available in 4 ohm, so it would straight drop-in your amp, recovering original power ... and being somewhat higher efficiency to boot.
    https://www.jensentone.com/vintage-ceramic/c12k
    And not a "mystery speaker" but a product from a serious traditional manufacturer.

    FWIW Fender is using two of these in some RI Twins instead of the "proper" C12N they "should" use, there must be a reason for that.
    People seem to like it very much.

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    Last edited by J M Fahey; 11-06-2018 at 05:10 AM.
    Juan Manuel Fahey

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    Don't know about Fender, but some of the other modeling amps use speakers that are flatter frequency response than a typical guitar speaker, that way they have more flexibility and do the "voicing" in the digital domain.

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    Old Timer daz's Avatar
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    Thanks Juan. But just to clear. I hated the original speaker and really like the G12T100 so I';m not interested in a new stock speaker. The celestion i'm using is available in 4 tho like i said i just want to be sure i will get more usable volume with it. I figured it's losing about 1/2 power with 8 ohms but i just wasn't sure if using a 4 and getting full power back would make enough difference in volume w/o the issue. If it still does it but gets me a Db or 2 before it starts flabbing out thats not worth $100.

    Quote Originally Posted by J M Fahey View Post
    Ok, I thought you were talking about an older and standard Fender amplifier, most probably having some Fender labelled generic Eminence.

    The GT is a "higher class" product, so they put a (more expensive than generic Eminence) Celestion.
    The G12T100 is a good speaker, no doubt, but it´s somewhat muddy (they call it "warmer ) compared to others and you are losing 50% power because of the impedance mismatch.

    Best way to sell your cake and eat it would be to put a Celestion 70/80 **8 ohm** inside the amp so it will never burn but you´ll get the original sound back (in my book "special versions" tend to be same speaker with a different label ) PLUS an extension cabinet with another 70/80 , again 8 ohm.

    You have exact same timbre as before, twice the power handling, you will move more air, all for the price of carrying an extension cabinet.

    Extension cabinet can be quite light (make it out of 12mm / 0.5" plywood), you can (should) put your current amp on it (make it same width) and worst case make it semi open backed, cover speaker back with chicken wire stapled all around so nothing can touch the cone back and use it to carry cables, your tuxedo, and anything else which needs carrying around.

    Sadly there are not many 4 ohm guitar speakers around, of those not many sound like the original one and even less have higher power handling, so.... choices are very limited.

    Pity the original one didn´t stand it.

    The EV is a VERY good speaker but being 8 ohm you are still losing 50% power.

    And it´s loud and efficient ... but the Celestions are also, so no big improvement compared to them, as you noticed.

    What I suggested is somewhat inconvenient but definitely an improvement over then original setup (single 4 ohm speaker), and to boot it will sound "bigger".

    Edit: found *one* guitar speaker about matching your requirements: 12" 100W , efficient/loud, and available in 4 ohm, so it would straight drop-in your amp, recovering original power ... and being somewhat higher efficiency to boot.
    https://www.jensentone.com/vintage-ceramic/c12k
    And not a "mystery speaker" but a product from a serious traditional manufacturer.

    FWIW Fender is using two of these in some RI Twins instead of the "proper" C12N they "should" use, there must be a reason for that.
    People seem to like it very much.

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    Supporting Member Jazz P Bass's Avatar
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    What Fender amp are we talking about?

    If it's a 40 watt job, you now have a 20 watt amp.

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    Old Timer daz's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    What Fender amp are we talking about?

    If it's a 40 watt job, you now have a 20 watt amp.
    I mentioned it above. It's a GT100 and i suppose it's actually well under 100 watts. Probably about 60 with the proper load so it's likely 30 now.

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    Old Timer J M Fahey's Avatar
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    I hated the original speaker and really like the G12T100 so I';m not interested in a new stock speaker.
    You should have said so before sending us on a wild chase doing your homework.

    I figured it's losing about 1/2 power with 8 ohms but i just wasn't sure if using a 4 and getting full power back would make enough difference in volume w/o the issue. If it still does it but gets me a Db or 2 before it starts flabbing out thats not worth $100.
    Doubling power is guaranteed 3dB more .
    If the number does not mean much: yes, ity´s noticeably louder.

    30/40W SS power is not enough to play along a drummer, live or inside a garage, *specially* in a modelling amp.

    In my book you need a *real* 25 to 50W tube amp (2 x EL84 does not qualify as "25W" no matter what Mesa or Peavey claim) or 80/100W SS (think Valvestate 80, Peavey Bandit, Fender M80, Randall RG80 and better) driving a good or better 12" (Eminence , Celestion or some of the better Chinese) to comfortably play besides a drummer.

    Your original amp fit the bill, the halfpower current one does not, not much more to think about it.

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    Juan Manuel Fahey

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    Old Timer daz's Avatar
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    Quote Originally Posted by J M Fahey View Post
    You should have said so before sending us on a wild chase doing your homework.


    Doubling power is guaranteed 3dB more .
    If the number does not mean much: yes, ity´s noticeably louder.

    30/40W SS power is not enough to play along a drummer, live or inside a garage, *specially* in a modelling amp.

    In my book you need a *real* 25 to 50W tube amp (2 x EL84 does not qualify as "25W" no matter what Mesa or Peavey claim) or 80/100W SS (think Valvestate 80, Peavey Bandit, Fender M80, Randall RG80 and better) driving a good or better 12" (Eminence , Celestion or some of the better Chinese) to comfortably play besides a drummer.

    Your original amp fit the bill, the halfpower current one does not, not much more to think about it.
    Will get one then, thanks.

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    I had the opposite happen with a crappy old SS Gibson amp someone gave me.
    The 4ohm speaker got damaged.
    I replaced it with an 8 ohm Jensen from the 60's which had some fuzz to it and it tamed the typical SS tinniness, mellowed out the sound and actually made the amp sound better.

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