Speaker selection - sensitivity, frequency response

jaymenon

 I find myself wondering, since many of the descriptions on speaker manufacturer websites are perhaps not as objective/reliable as one would like.  And tone is of course, subjective...

 Are speakers with lower sensitivity (96dB greenback versus 100dB G12H for instance)  actually quieter in practice?  Or is the difference more theoretical than real?

 Secondly, mounting multiple speakers in a 2×12 or 4×12 cabinet is going to augment both the bottom and and top end right?

 Therefore when considering a 1×12 cabinet, it would appear to be intuitively logical
 (to my mind anyway) to pick a speaker that has a little more bass and treble extension...

I’d be most interested to hear your expert  and first hand opinions...

Danny1969

A less sensitive speaker is definitely quieter for a given amount of power than a more sensitive one. I have a 1 x12" cab with a very sensitive old 16 ohm fane speaker in it that is so sensitive you can drive it directly from an opamp and it's loud enough to practice with indoors, that's about 80mW

The amount of bass from any speaker driver is purely dependent on the cab .... bigger box means more bass

ICBM

Sensitivity differences are dependent on frequency/harmonic response to a degree - a Greenback actually doesn't sound any quieter than a G12H-30 really, because the Greenback has a much more midrangy, slightly fuzzy tone with a peak where your ear is most sensitive, which makes it seem louder than the G12H's cleaner, deeper tone. If you put the two of them in the same cab and listen, there's no noticeable volume offset.

But a V30 - which is also a 100db speaker, like the H30 - is much louder, because it has an even more exaggerated dirty midrange tone than the Greenback.

Also, different manufacturers weight the measurements differently - it's all a bit subjective since the frequency response is not remotely linear. For example Eminence claim some really high sensitivities compared to similar Celestions, but they're no louder in practice - eg the Red Fang vs. the Blue... the Red Fang is claimed to be 3dB more sensitive, but the Blue is slightly louder.

Bigger and closed cabs tend to emphasise bass and cut mids to a degree - top end isn't as much affected.

ecc83

If you want to work it out? SPL (at 1 mtr) is 'Log w x10 +S' Where w is the power in watts and S is the sensitivity of the speaker. So yes Danny, your old speaker* was delivering 90dB SPL for 0.08W and that is much louder than most FSTVs will go!

But, as ICBM points out, the response, especially where it peaks, has a profound effect on perceived loudness, this also applies to amplifier 'voicing' as well of course.

Multiple speakers will make the system ever more directional at upper mids and HF but if you are affront it you will hardly notice that . Go 20 ft out into a room and you should hear the 'beaming' effect. This directionality also gives a gain in sensitivity so yes again. Bigger speaker systems WILL sound louder at both bass and upper mid frequencies. (it is often said that the 'angled' 4x12 came about to give a clearer sound to peeps in cinema balconies?) They will also GO louder in the limit because they suffer Thermal Compression less with the shared power.

*I had a 12" Vitavox cine speaker . BEEUTIFUL thing in hammer grey and a polished Nickel magnet. Loud as 'k but 'shouty' and not really nice.  'king heavy as well!

Dave.

ecc83

Er? "Bigger box means more bass"? Bit more complicated than that. We perceive bass at around 60Hz so a box/woofer combination that peaks around there will seem 'bassier' than a bigger box with a resonance at say 40Hz.  Note also that bigger boxes load cones less and therefore reduce ultimate power handling.

For HIGH FIDELITY the design of speaker cabs, especially ported jobs is a complex matter employing the 'Small' driver parameters. For guitar speakers it is done with a bit of string and a stick of chalk.

Dave.

ICBM

ecc83 said:

If you want to work it out? SPL (at 1 mtr) is 'Log w x10 +S' Where w is the power in watts and S is the sensitivity of the speaker. So yes Danny, your old speaker* was delivering 90dB SPL for 0.08W and that is much louder than most FSTVs will go!

I've still got that old Goodmans cab in my workshop which has an Audiom 150 as the bass driver, in a rear-ported enclosure that uses the corner of the room as a reflex chamber - it's astonishing loud and produces real deep bass when driven from the headphone output of my computer (50mW I think), with no external amp. I don't know what the cab sensitivity is but I'd bet it's well over 100dB.

ecc83 said:

it is often said that the 'angled' 4x12 came about to give a clearer sound to peeps in cinema balconies?

No, it was because Jim Marshall thought it looked better like that with the amp head on top of it .

It does work quite well for hearing yourself when you have a single cab on stage though.

p90fool

Well they could hear my 100w Superbass on the balcony in the cinema, and I didn't even live anywhere near it. 

Dave_Mc

What ICBM said.

In fact, even the frequency response thing isn't totally cut-and-dried- the V30 combined with the G12T75 is a known good combination, and the G12T75 is both 3dB quieter *and* much more scooped in the mids than the V30, so in theory should be noticeably quieter than the V30 in both respects... and yet that combination of speakers works very well.

ICBM

Dave_Mc said:

In fact, even the frequency response thing isn't totally cut-and-dried- the V30 combined with the G12T75 is a known good combination, and the G12T75 is both 3dB quieter *and* much more scooped in the mids than the V30, so in theory should be noticeably quieter than the V30 in both respects... and yet that combination of speakers works very well.

It is an odd one, but it really does work. Before I heard it I assumed the V30 would totally dominate, for exactly those reasons - but in fact it sounds balanced, and the 75 is by no means inaudible. It's almost as if the 75 flattens out the upper-mid spike of the V30 and 'loosens' the response of it as well as adding deep lows and highs. It does seem to work best in a 4x12" with the speakers in a x-pattern, but it's not bad in a 2x12" either.

Dave_Mc

^ Yeah, same here. I've only tried it in a 2x12 and it matched pretty well. I could understand the greenback + G12H30 working, because as you said above, although the G12H30 is louder, it's more scooped in the mids, so it sort of evens out, but like you I was kind of shocked that it still seemed to work with the G12T75 and V30 where both the sensitivity and the tone seemed to be working against the G12T75.

I wouldn't want to say that you should ignore the specs completely- you can sort of make an educated guess from the spec sheet. But you never really know for sure until you try them in real life...

ICBM

Dave_Mc said:

^ Yeah, same here. I've only tried it in a 2x12 and it matched pretty well. I could understand the greenback + G12H30 working, because as you said above, although the G12H30 is louder, it's more scooped in the mids, so it sort of evens out, but like you I was kind of shocked that it still seemed to work with the G12T75 and V30 where both the sensitivity and the tone seemed to be working against the G12T75.

I wouldn't want to say that you should ignore the specs completely- you can sort of make an educated guess from the spec sheet. But you never really know for sure until you try them in real life...

Very true - it can also go the other way round.

A friend had a Harley Benton 2x12" with two V30s - he found it too spiky in the mids, so we swapped one of the speakers for a Classic Lead, which is one of the known good combinations and did improve things... but he was still hearing too much of the V30 spike, so we swapped it for a G12M-65 Creamback. On paper this should be excellent with the Classic Lead, since that's not too far away from a Greenback and a G12H-30.

It sounded *terrible*. The pair just did not mix at all - they sounded 'separated', you could hear them as two very different and clashing tones, exaggerating the bad bits of each, which made the Creamback sound fuzzy and the CL80 sound metallic - worse than either of them did alone.

Finally on a hunch - since I hadn't tried one at that point - we swapped the 80 for a G12H-75 Creamback, and the result is as great as a Greenback/G12H-30 pair - again, they mix together perfectly and sound almost like 'one' better speaker. Why the results are so different when the CL80 and the G12H-75 are not that far away from each other, I have no idea!

jaymenon

ICBM said

jaymenon

 Unless the speakers were out of phase -  with such an unusual response, I’m sure your friend would’ve been careful with his wiring. But at the speakers been mistakenly wired at the factory, they could have been out of phase with each other. That would’ve been something to check… 

ICBM

jaymenon said:

 Unless the speakers were out of phase -  with such an unusual response, I’m sure your friend would’ve been careful with his wiring. But at the speakers been mistakenly wired at the factory, they could have been out of phase with each other. That would’ve been something to check… 

They were definitely in phase, I checked. That was the first thing I thought too...

They just didn’t sound right together for some reason.

Dave_Mc

ICBM said:

Very true - it can also go the other way round.

A friend had a Harley Benton 2x12" with two V30s - he found it too spiky in the mids, so we swapped one of the speakers for a Classic Lead, which is one of the known good combinations and did improve things... but he was still hearing too much of the V30 spike, so we swapped it for a G12M-65 Creamback. On paper this should be excellent with the Classic Lead, since that's not too far away from a Greenback and a G12H-30.

It sounded *terrible*. The pair just did not mix at all - they sounded 'separated', you could hear them as two very different and clashing tones, exaggerating the bad bits of each, which made the Creamback sound fuzzy and the CL80 sound metallic - worse than either of them did alone.

Finally on a hunch - since I hadn't tried one at that point - we swapped the 80 for a G12H-75 Creamback, and the result is as great as a Greenback/G12H-30 pair - again, they mix together perfectly and sound almost like 'one' better speaker. Why the results are so different when the CL80 and the G12H-75 are not that far away from each other, I have no idea!

Yeah definitely. I've tried some combos which just didn't really work (I can't remember offhand what they were, lol), and then some that worked great, and it's hard to guess up-front which will be which. Unless you know up-front how risky it is and know you could be out the cost of a speaker, it's probably safer to stick to the tried and tested combos which are known to work...