How Much Difference does sensitisity make to volume?

[gilmour]

Ok, this should be a quickee

I read in the "What I learned in 2008" thread someones commment that the sensitivty of a cab can make a big difference to volume.

I'm looking at 2 cabs ATM one is 103DB sensitive and the other 106DB. WIll this make a really significant difference, or is 3DB to little to really notice?

I remember someone once telling me that each decibel was twice as loud as the previous, ie 100DB is twice as loud as 99DB. But I might have dreamt that, and it may have no bearing when talking about sensitivity.

Thanks

Edited January 4, 2008 by gilmour

[Hamster]

[quote name='gilmour' post='113312' date='Jan 4 2008, 12:37 AM']Ok, this should be a quickee

I read in the "What I learned in 2008" thread someones commment that the sensitivity of a cab can make a big difference to volume.

I'm looking at 2 cabs ATM one is 103DB sensitive and the other 106DB. WIll this make a really significant difference, or is 3DB to little to really notice?

I remember someone once telling me that each decibel was twice as loud as the previous, ie 100DB is twice as loud as 99DB. But I might have dreamt that, and it may have no bearing when talking about sensitivity.

Thanks[/quote]

IIRC, with an input of one watt a speaker with a sensitivity of 103db/Wm will produce 103db of sound at a distance of one meter. To increase the volume by 3 db, you must [u]double[/u] the power, so 3db is about twice as loud. Therefore, if you put 100watts into a speaker of 106db sensitivity, you make the same noise as putting 200watts into a speaker of 103db sensitivity.

It think that's right

Hamster

[gilmour]

so 106db is significantly louder then

[Hamster]

[quote name='gilmour' post='113324' date='Jan 4 2008, 01:15 AM']so 106db is significantly louder then[/quote]

IIRC, it's twice as loud as a speaker of 103db sensitivity if using the same input level. I may be wrong, but I think I'm right. No doubt Bill F or Alex C will be along soon to put me right

Hamster

[Bill Fitzmaurice]

[quote name='Hamster' post='113329' date='Jan 3 2008, 08:51 PM']IIRC, it's twice as loud as a speaker of 103db sensitivity if using the same input level. I may be wrong, but I think I'm right. No doubt Bill F or Alex C will be along soon to put me right

Hamster[/quote]Close. A 3dB difference is equal to twice/half the power, but not twice/half the perceived volume. Hearing response is logarithmic, so it takes a 10dB difference to sound twice/half as loud.
As for manufacturers SPL ratings, they're next to useless, because they aren't referenced to frequency. Some, like Ampeg, quote a legitimate average figure. Some, like Eden, quote a peak figure. Some quote figures that defy all known laws of physics. None save Phil Jones provide the all important SPL charts that allow one to know the facts.

[jammie17]

[quote name='Bill Fitzmaurice' post='113339' date='Jan 4 2008, 03:24 AM']Close. A 3dB difference is equal to twice/half the power, but not twice/half the perceived volume. Hearing response is logarithmic, so it takes a 10dB difference to sound twice/half as loud.
[i][b]As for manufacturers SPL ratings, they're next to useless, because they aren't referenced to frequency. [/b][/i]Some, like Ampeg, quote a legitimate average figure. Some, like Eden, quote a peak figure. Some quote figures that defy all known laws of physics. None save Phil Jones provide the all important SPL charts that allow one to know the facts.[/quote]


Please explain. Does this mean that an AVERAGED SPL rating is useless? Referenced to frequency? Wouldn't that mean, in a speaker with a frequency rating of 20-20k, there would be literally 20k different SPL ratings if the manufactures referenced their speakers SPL output to each frequency that speaker could reproduce?

[warwickhunt]

I think I can offer some real world insight...

I have a cab with a sens of 105db (Tech Soundsystems) and I was expecting it to mop the floor against less sensitive cabs but TBH it is almost impossible to make a true comparison! Aside from the spurious stats put out by the different manufacturers, the actual design of the cab/drivers used/height/etc etc makes comparisons in a gigging situation a joke. A mid biased cab (Schroeder) will 'sound' louder though in fact it may be less sensitive. Conversely a cab with a bit of mid scoop can 'appear' to be less sensitive, when in fact the published stats say it isn't.

I also expected to not have to turn my amp up quite as high for a cab that is very sensitive and to some degree that is true but we are talking a midge's kn*cker!

Final comment - It is worth some consideration but unless you are comparing 2 cabs from the same manufacturer your probably better judging purely on the tone of the cab.

[Kiwi]

It was me who made the original comment and I was going by my experiences of comparing my Acme B2's to my EBS 212 with a sensitivity difference of about 10dB.

There was definitely a difference in volume and a marked improvement in performance at band rehearsal volumes. When I used the B2's with my 140w Burman heads the amp sounded like it was putting out about a quarter of the power. I have learned that sensitive cabs are more versatile in allowing me to satisfactorily use them with amps with a wider range of power ratings.

[alexclaber]

[quote name='jammie17' post='113340' date='Jan 4 2008, 03:33 AM']Wouldn't that mean, in a speaker with a frequency rating of 20-20k, there would be literally 20k different SPL ratings if the manufactures referenced their speakers SPL output to each frequency that speaker could reproduce?[/quote]

Yes.

If you want to see real world speaker ratings, then looking at Aguilar's newly updated sensitivity specs (ignore the frequency response ones, they're too vague to be useful), Ampeg, Phil Jones Bass and Acme. Bearing in mind that none of the Aguilar line are designed to go particularly low you can use them as a reference for how much sensitivity is possible from a bass cab. If a manufacturer quotes a higher figure than this then it is based on a peak in the response and possibly even the peak sensitivity from the tweeter!

So expect no better than 95dB per 10" woofer, and add 3dB every time you double the number of woofers.

Alex

[alexclaber]

[quote name='Crazykiwi' post='113395' date='Jan 4 2008, 10:16 AM']It was me who made the original comment and I was going by my experiences of comparing my Acme B2's to my EBS 212 with a sensitivity difference of about 10dB.

There was definitely a difference in volume.[/quote]

A pair of Low-B2s are ~96dB. A typical 2x12" is ~98dB. However, based on the EBS cabs I've heard I'd expect a sensitivity peak in the high midrange plus a very high sensitivity tweeter which would make it sound more than 2dB louder.

Lowpass the two rigs at 500Hz and you'd hear little difference in output. Lowpass the two rigs at 200Hz and the Acmes would probably be louder. Lowpass the rigs at 100Hz and the Acmes would be significantly louder.

Alex

[gilmour]

my head hurts!

[Hamster]

Hey - I was almost right! That's a vast improvement!

Hamster

[Kiwi]

[quote name='alexclaber' post='113403' date='Jan 4 2008, 10:24 AM']A pair of Low-B2s are ~96dB. A typical 2x12" is ~98dB. However, based on the EBS cabs I've heard I'd expect a sensitivity peak in the high midrange plus a very high sensitivity tweeter which would make it sound more than 2dB louder.

Lowpass the two rigs at 500Hz and you'd hear little difference in output. Lowpass the two rigs at 200Hz and the Acmes would probably be louder. Lowpass the rigs at 100Hz and the Acmes would be significantly louder.

Alex[/quote]
I haven't measured the B2's myself but the blurb on the Acme site says a B2 is about 93dB. EBS rate their 212 at 103dB. I was content to go with those figures for the sake of a purchasing decision. When I ran the Acme's with the amp, the lows were considerably more distorted to my ears but I don't have the inclination to lowpass the cabs, thats not how I use them. Still liked the sound the Acme's made a lot and in other circumstances I would have kept them but didn't want to tailor my setup around the speakers. I wanted speakers to match the amp.

[Bill Fitzmaurice]

[quote name='Crazykiwi' post='113533' date='Jan 4 2008, 08:57 AM']EBS rate their 212 at 103dB.[/quote]That would have to be a peak reading. There are no twelve inch drivers capable of that level broadband averaged. Twelves do exist that have 100dB sensitivity (making a pair 103dB), even a bit more, but they only achieve that sensitivity above 200 Hz or so. Below 100Hz, where it counts, 98dB is the practical limit in a direct radiator cabinet.

[Kiwi]

[quote name='Bill Fitzmaurice' post='113543' date='Jan 4 2008, 02:21 PM']That would have to be a peak reading. There are no twelve inch drivers capable of that level broadband averaged. Twelves do exist that have 100dB sensitivity (making a pair 103dB), even a bit more, but they only achieve that sensitivity above 200 Hz or so. Below 100Hz, where it counts, 98dB is the practical limit in a direct radiator cabinet.[/quote]
In terms of my experience of listening to the two, I would agree that the Neo212 has a distinctive response. Its certainly less even sounding than one Acme (which was quite happy being powered by 400w and sounded very good). There's definitely a mid hump with the Neo 212 (somewhere around 400-600Hz) and a touch of boominess, but that was at 'home' levels of volume. I couldn't say whether that character was due to the neo magnets, the cabinet design, the speaker sensitivity through the frequency range or ambient acoustics though. Probably a combination of them all I expect.

I'll see how the neo 212 shapes up at rehearsal this weekend, 3dB here or there probably means very little on stage.

[Jack]

In response to the OP, its about as important as "should i buy the 300W or 600W amp?" Because your amp would need twice the power with the 103db cab to sound as loud as using the 106db cab. As with anything, this only happens in the hypothetical magical pixie-world that sadly eludes us mere mortals.

As has been discussed previously a lot of manufacturers inflate or downright lie about their sensitivity ratings. And even then, the standard (when its used fairly) is to measure cabs at 1kHz which is so utterly pointless for the majority of bass players that the sensitivity wouldnt make much difference even if it was truthfull.

Props to people like Bill Fitzmaurice for actually publishing response graphs.

[jammie17]

[quote name='alexclaber' post='113399' date='Jan 4 2008, 10:20 AM']Yes.

If you want to see real world speaker ratings, then looking at Aguilar's newly updated sensitivity specs (ignore the frequency response ones, they're too vague to be useful), Ampeg, Phil Jones Bass and Acme. Bearing in mind that none of the Aguilar line are designed to go particularly low you can use them as a reference for how much sensitivity is possible from a bass cab. If a manufacturer quotes a higher figure than this then it is based on a peak in the response and possibly even the peak sensitivity from the tweeter!

So expect no better than 95dB per 10" woofer, and add 3dB every time you double the number of woofers.

Alex[/quote]

Ahhhh...thank you.

[Perry]

Glimour, I'd give you some headache tablets but I need them all

[gilmour]

[quote name='Perry' post='116791' date='Jan 9 2008, 09:23 AM']Glimour, I'd give you some headache tablets but I need them all [/quote]
I'm off down the chemists then !

I think I'm getting there, slowly but surely, I've only just found out that for the last 10 years I've been using a 4ohm and 8ohm cab together (apparently a big no no), what can I say I was young and foolish back then

Interestingly it was this that was one of the things that made me think about this thread in the first place. I've been runnign a Trace 4x10 and And Peavey BW 1x15. The Peavey is 4 ohms and the Trace 8 but the Peavey Isn't significantly louder, I thought it might be down to the sensitivity of the Trace, but perhaps it's just the number of cones, or the fact that it's at ear height.

For the last year or so I've only used the Peavey on it's own. I'd like to pretend that this was down to the Ohm issue, or a preference for the 15 (which I do like) but in truth it's lighter and fine for most gigs, the two cabs was just overkill, when I do a bigger gig there's usually a backline anyway.

Edited January 9, 2008 by gilmour

[bremen]

[quote name='gilmour' post='116999' date='Jan 9 2008, 02:10 PM']I'm off down the chemists then !

I think I'm getting there, slowly but surely, I've only just found out that for the last 10 years I've been using a 4ohm and 8ohm cab together (apparently a big no no), what can I say I was young and foolish back then [/quote]

Why is that a no-no? If both cabs have identical sensitivity, the 8 ohm cab is only going to be 3dB quieter than the 4, and consensus seems to be that 3dB here or there isn't worth bothering about.

[warwickhunt]

[quote name='bremen' post='117053' date='Jan 9 2008, 03:21 PM']Why is that a no-no? If both cabs have identical sensitivity, the 8 ohm cab is only going to be 3dB quieter than the 4, and consensus seems to be that 3dB here or there isn't worth bothering about.[/quote]
It isn't just the sensitivity (I assume) but the combination of 8 & 4 ohm cabs takes the load down to less than 4 ohms which is a no-no for 'most amps', though as you have obviously found, so long as you don't drive your amp/cabs to destruction and amp can run at 3.6 ohms (or what ever it may be) without a melt down!

However... sometimes combinations of ohmages, sensitivities etc do just work and no amount of charts and graphs can account for it!

[Bill Fitzmaurice]

[quote name='warwickhunt' post='117116' date='Jan 9 2008, 11:28 AM']no amount of charts and graphs can account for it![/quote]
Actually, they do. The problem is obtaining accurate data, or more to the point where the electric bass cab industry is concerned, any data.

[warwickhunt]

[quote name='Bill Fitzmaurice' post='117162' date='Jan 9 2008, 05:07 PM']Actually, they do. The problem is obtaining accurate data, or more to the point where the electric bass cab industry is concerned, any data. [/quote]

Agreed Bill and I did allude to that in my earlier posting.

Unfortunately that's why half the time it's better if you can just get the gear together in one place and try for yourself. Shame we didn't have our own UK Tom Bowlus... now that must be fun!

[Gray]

Hi,

Just my pennies worth from PA hire world.

Aside from the sensitivity ratings of speakers - which give you an average across the freq. spectrum. If you want to get really anal its worth looking at the THD (total harmonic distortion) figures for the amp being used to drive across its operational range.

As is rightly stated a 4ohm cab and 8 ohm cab in parrallel would drop the impedance (to somewhere in the region of 2.67 Ohms). This is the primary consideration - semi pro power amps are usually not happy being driven below 4Ohms. So, unless your using a decent touring class amp 2 Ohms is to be avoided. Dropping an impedance below the rated value of the amp will result in instant fried output stage of the amp - and probable damage to the cabs.

In PA world (particularly in regards to driving bins) its fairly standard practice to use amps which are twice the rated RMS output of the speakers they are driving (i.e. 1000 Watt RMS amp driving a 500 watt RMS cone).

The logic behind this being that your amp has considerable headroom whatever input source is driving it - if you are driving an amplifier hard to attain the perceived volume from speakers (a function of sensitivity and rated output) constantly then it will distort. Ultimatly distortion will write off speakers fairly efficiently. So, better to have an amp turned down (i.e. in the middle of its operational range) but with enough headroom to cope with sudden peaks in input without distorting (speakers will survive quick transient bursts far better than continious distortion).

Hope this helps

Gray

[Bill Fitzmaurice]

[quote name='Gray' post='117184' date='Jan 9 2008, 12:22 PM']In PA world (particularly in regards to driving bins) its fairly standard practice to use amps which are twice the rated RMS output of the speakers they are driving (i.e. 1000 Watt RMS amp driving a 500 watt RMS cone).


Gray[/quote]In the instrument amp world the opposite is very often the case. With PA systems one does not wish to have distortion anywhere in the signal chain. With instruments distortion, sourced both within the amps and the speakers, is part and parcel of the instrument tone. Bass in general doesn't go to the extremes that guitar does in terms of the distortion density, but when a bass player refers to 'growl' in his tone distortion is the source.