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A Question on Speaker Driver Efficiency

I have been tweaking my guitar amps, by upgrading the speakers.

I installed a larger speaker (was 8" now 10") in my bass amp, but I made sure it was very efficient - net result
- not only is the bass much deeper sounding,
- but because the new driver was more efficiant I now play at a lower volume.

So I am now considering upgrading my other amp (i.e. used for my 6 string) and got to thinking about building a new cabinet that houses two speakers.

I know that connecting the speakers in ...
- series will double the impedance, i.e. 2 x 4 ohms would have an onverall impedance of 8 ohms
- parallel will halve the impedance, i.e. 2 x 16 ohms would have an onverall impedance of 8 ohms

But what I have not been able to get my head around is...
- what will each connection method (i.e. series or parallel) have on the "combined" sensitivity rating?
- e.g. if both speakers are rated at 96db sensitivity, will the overall sensitivity change due to the connection method or remain at 96db?

Since I can get 4 ohm or 16 ohm drivers - which connection method would be best? series or parallel?

in case it is a factor
- the amp is 15 watts into 8 ohm
- I am looking at employing two identical drivers each rated at 96db sensitivity
- 96 db (or higher) is the target for the combined sensitivity

Any help is appreciated - Many Thanks Steve
williewonka
kijanki's avatar
kijanki
4,432 posts
 
In theory, they move at EXACTLY the same time only when no capacitance exists in the circuit. Current through the coils is the same at any given time only when the circuit doesn’t have capacitance. We know this is not the case. All circuits have some level of capacitance and inductance. The question is whether or not the amount of capacitance in the circuit and how it interacts with the series inductance is readily detectable.
OMG, Do you really think that electric current slows down thru inductance in the circuit and accelerates after? Please simulate this before you place more of this nonsense.

cj1965
124 posts
 
:"OMG, Do you really think that electric current slows down thru inductance in the circuit and accelerates after? Please simulate this before you place more of this nonsense. " - kijanki

OMG....educate yourself before you go online and make yourself look foolish attempting to educate others.

Current through an inductor is defined by the following equation:

V=Ldi/dt

Current through a capacitor is defined by the following:

I =Cdv/dt

When the above elements are combined with resistance in a series circuit and excited by a time varying voltage, the following equation results:

R I ( t ) + L 1 d I ( t ) d t +  L 2 d I ( t ) d t + V ( 0 ) + 1 C ∫ 0 t I ( τ ) d τ = V ( t ) .
From the above, one can see that voltage - V(t) is not simply split between the two "ideal" drivers L1 and L2. The capacitor's voltage buildup and drop off over time changes the equation. While the value of C is likely very small in this particular circuit, it's STILL THERE.
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
CJ1965 4-17-2018
If you [Atmasphere] had any experience designing or building amplifiers, you’d know that every energy storing element within a circuit contributes to phase lead or lag between voltage and current. Loudspeaker coils are no different.
FYI, "Atmasphere" is the designer and owner of Atma-Sphere Music Systems, Inc., which for more than 40 years has produced some of the world’s most unique and highly regarded amplifiers and preamplifiers.

Also, my belief and my perception has been that his frequent contributions to this forum are more highly valued and more widely respected than those of any other designer or manufacturer who participates here.
A little humility goes a long way ....
+1

Regards,
-- Al

cj1965
124 posts
 
@almarg

That’s all well and good, however, the laws of physics and the mathematical descriptions of those laws haven't changed much in the past century. Every circuit has capacitance, inductance, and resistance - of that there is very little doubt. Given this salient fact, one should be careful giving blanket answers to questions raised on this forum without deferring to the underlying equations that DEFINE as accurately as currently possible, the conditions associated with the questions being asked. It’s one thing to provide blanket answers that leave out the details in response to a question raised here. It is quite another to "correct" someone with the same "blanket answers that leave out details" when the person you’re attempting to correct has provided those missing details.
kalali's avatar
kalali
1,977 posts
 
+1 Al

Thank you. People need to learn to express their opinions without the need to insult others, especially the ones whose knowledge and experience as well as their contributions are unique in this industry. 
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