guitar amp speaker wattage

Thread Starter

bunker

Joined Nov 25, 2019
6
can I use 4 25 watt speakers behind a 100 watt amp without damaging the voice coils? would they have to be wired a certain way?
 

Audioguru again

Joined Oct 21, 2019
837
Speakers are usually 8 ohms and amplifiers are usually designed to drive one 8 ohm speaker with its rated output power.
1) One 25W speaker on a 100W amplifier= The speaker blows up.
2) Two 25W speakers in series on a 100W amplifier= Both speakers blow up.
3) Four 25W speakers in series on a 100W amplifier= The speakers survive but sound "boomy and muddy" since resonance damping from the amplifier is poor.

If two or more speakers are connected in parallel then the amplifier might blow up.
 

Papabravo

Joined Feb 24, 2006
12,848
Speakers are usually 8 ohms and amplifiers are usually designed to drive one 8 ohm speaker with its rated output power.
1) One 25W speaker on a 100W amplifier= The speaker blows up.
2) Two 25W speakers in series on a 100W amplifier= Both speakers blow up.
3) Four 25W speakers in series on a 100W amplifier= The speakers survive but sound "boomy and muddy" since resonance damping from the amplifier is poor.

If two or more speakers are connected in parallel then the amplifier might blow up.
That might just be a metaphor for life. Mine has always been: "The positive real roots disappear, or the system does." I actually like yours better; it is closer to common reality.
 

ci139

Joined Jul 11, 2016
1,165
speaker have 2 power ratings RMS and peak -- the peak may be a way higher . . . and it only illustrates how durable it is
an illustrative example comparison /// according to below data the actual voltage p-p . . . sine can have an amplitude \( V_{RMS}=\sqrt{P_{RMS}·R}\ ,\ V_{p-p}=V_{RMS}·\sqrt2 \) thus \( V_{p-p}=\sqrt{P_{RMS}·R}·\sqrt2=\cases{\sqrt{110W·4Ω·2}=±29.66V\\ \sqrt{70W·4Ω·2}=±23.66V} \) ← this actually results in a current ramp(flow) through the speaker coil . . . as the coil has inductance and the core has a flux saturation - it actually self-limits the higher frequencies and ramp speed - but it does not self-limit absolute deviation ◄– this in turn means that it is not that sensitive to narrow voltage spikes as low frequency over-voltage , the flux saturation actually won't add to physical amplitude of the membrane but when saturated the voice coil current ramps up and may destroy the coil or connector wire
-- so the peak power basically tells the DC voltage or current beyound what the materials an construction is likely over-stressed
--- as you can see the RMS rating below is closer to the Peak power for the elliptical speaker -- this is likely because the elliptical speaker "keeps it's oscillation axes" more steady than the circular one - thus shares the force to the edges of it's membrane more even . . . there might be more to this ...
spkrs-cmpr.png
 
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Ylli

Joined Nov 13, 2015
891
Assuming all the speakers are identical, put two in series and put those in parallel with the other two in series. Impedance will be the same as one speaker, and the power handling capability will be x4 of one speaker.
 

Wolframore

Joined Jan 21, 2019
1,600
Just make sure we're checking the impedance. If you are working on a guitar amplifier, there are a number of impedance that are used and available for them. I have seen 4, 8 or 16Ω speakers. Also make sure you check the requires output impedance from the AMP. Some amps have both 4 or 8 Ω outputs. You have to wire the speakers in the correct way to match the outputs. It's not a quick and easy question and answer. You have to consider the impedance.

YOU CAN DAMAGE YOUR SPEAKERS,. AMP OR BOTH...

This from Celestion website: Most of their speakers are available in 8 or 15Ω

1577384814139.png

Make sure you check the output from the amps:
1577384871213.png


1577384914673.png


This one is selectable:

1577385096627.png
 

MisterBill2

Joined Jan 23, 2018
5,157
I have been setting up a system with a dual channel amplifier claiming 400 watts per channel. But then in the manual I see that 400 watts is into 2 ohms, while with an 8 ohm load the output is 165 watts per channel. So if you put all 4 speakers in series the output will be less than 100 watts and it will work well. Of course if you can look in the manual for the amplifier you may find some interesting information. Do you actually intend to run the amplifier at 100 watts output?
and "The special way" to connect the speakers is in series, with correct phasing , so that they all move in the same direction. As for the assertion that they will sound muddy or boomy, you do not have an audiophile system with a guitar amplifier.
 
A solid state amplifier does not use an output transformer so the power output depends on the load impedance.
A "400W" amplifier might produce 400 peak Watts at a horrible 10% clipping distortion. Then its real output power is 200W at 10% clipping distortion or 160 real watts at low distortion.

If a solid state amplifier produces 400W into 2 ohms then its output into 4 ohms is probably about 225W and its output into 8 ohms is probably about 127W.

Four 8 ohms speakers in series are 32 ohms and the output power in each one will be only about 10W.
Since we don't know if the amplifier's rated 400W is peak or very distorted then the power in each speaker might be only 5.6W.
The speakers will have no resonance damping produced from the extremely low output impedance of the amplifier so they will sound like bongo drums, not electric guitars.
 
What happens if you keep paralleling the speakers? Let’s say you got it down to 0.1 ohm. It’s just a thought exercise.
Do the simple math:
400W into 2 ohms or almost 800W into 1 ohm, or almost 1600W into 0.5 ohm, or almost 3200W into 0.25 ohm, or almost 6400W into 0.125 ohm, or almost 8000W into 0.1 ohm.
If the amplifier is a cheap one then don't you think it will produce lots of smoke and maybe catch on fire with 1 ohm at almost 800W? If the amplifier is a good one then don't you think it will protect itself?
 

Wolframore

Joined Jan 21, 2019
1,600
Well it depends on how efficient the amplifier is :j. If the amplifier is 100% efficient there should be no problem as long as your power supply can support it. Like I said it’s just a thought exercise.
 

MisterBill2

Joined Jan 23, 2018
5,157
A solid state amplifier does not use an output transformer so the power output depends on the load impedance.
A "400W" amplifier might produce 400 peak Watts at a horrible 10% clipping distortion. Then its real output power is 200W at 10% clipping distortion or 160 real watts at low distortion.

If a solid state amplifier produces 400W into 2 ohms then its output into 4 ohms is probably about 225W and its output into 8 ohms is probably about 127W.

Four 8 ohms speakers in series are 32 ohms and the output power in each one will be only about 10W.
Since we don't know if the amplifier's rated 400W is peak or very distorted then the power in each speaker might be only 5.6W.
The speakers will have no resonance damping produced from the extremely low output impedance of the amplifier so they will sound like bongo drums, not electric guitars.
The amplifier in the system that I was referencing is used primarily for speech, and occasionally for singing, never at a loud level. That amplifier is part of an 8 channel mixer board and is used only because it is on hand and paid for and so could provide the number of inputs needed. I mentioned the power versus load impedance only to show that in many amplifiers power delivery depends a lot on load impedance, and so there was a way to connect the speakers that would be safe. And remember that not everybody can hear that 0.01% distortion in a 35dB violin solo.
 
Audio is not supposed to sound narrow-band and distorted just like video is not supposed to look fuzzy and with wrong colors.
An amplifier and its speakers are not supposed to fail when the volume is turned up.
An electric guitar is not supposed to sound "boomy" like a bongo drum.
 
Well it depends on how efficient the amplifier is :j. If the amplifier is 100% efficient there should be no problem as long as your power supply can support it. Like I said it’s just a thought exercise.
No audio power amplifier is 100% efficient. If it is electrically or thermally overloaded then it blows up or it protects itself by shutting down. Most IC audio power amplifiers protect themselves from abuse.
 

djsfantasi

Joined Apr 11, 2010
6,115
The principles outlined here can be easily put into practice.

As quite a few member’s here know, I ran a Haunted House fundraiser. In most of the hallways my predecessors simply put a bunch of 8Ω speakers in parallel on a cheap boom box. Volume control was limited and definitely not loud enough.

I rented a 300W amp. Eight speakers were enough for 5,000 sq.ft. I bought 8” 8Ω speakers and my Dad made custom cabinets. Special terminal blocks were also made to go along with custom cables. So each speaker could terminate the signal or be wired in series with the signal. Two sets of two serially connected speakers in parallel presented an 8Ω load to one channel of the 300W amp; a similar array connected to the other channel.

No matter what screams or other sound effects were occurring, mood music could always be heard in the hallways.

It could (and was) extended to three sets of 3 - 8Ω speakers in series (9 speakers in total). For a grand total of 18 background effect speakers.
 
Incorrect operation? The amplifier and speakers are for an electric guitar. They want the sound to be BAAAAD, really BAD.
Tons of awful distortion and maybe the boomy effect caused by speakers in series.

Most rock groups replace the vacuum tubes for each gig, because they are abused badly.
 

ci139

Joined Jul 11, 2016
1,165
I use 4 25 watt speakers
unfortunately there's no hint of impedance - there are , what i don't have - the 2Ω speakers then 4Ω , 8Ω , 16Ω , 32Ω
also no data about the output impedance for the 100W thingy

since driving high voltage through electronics is likely . . . ? more expensive by components' cost -- it's likely a 4Ω maybe a 2Ω AMP
? 25W -- newer met such wattage -- i don't make guesses here but the net shows the likely range of 2 , 3 , 6 or 8 Ω
 
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