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Question about sensitivity/volume

#2
markblasco said:
I have an Acme B4, which states it has a 96dB 1W/1M sensitivity.

The Genz Benz Neo 2X10 states it has a 101dB 1W/1M sensitivity.

Does this mean that, given the same amount of power, the Genz Benz speaker cabinet will be 5dB louder, even though it is a 2X10 instead of a 4X10?
Click to expand...

There are a few issues here IMO and IME.

SPL is measured typically at 1K... upper midrange. So, assuming the SPL spec's in the manufacturer's marketing materials are correct, they are more of a measure of the mid voicing versus a more wide, extended low end. We tend to hear a mid voiced cab as 'louder' since it's those mid frequencies that really jump out in a mix.

Also, many of these publishes SPL spec's don't seem to be totally accurate and comparable across manufacturers anyway.

HOWEVER, as I've posted a number of times previously, the published SPL figures are a good proxy for the voicing of a cab. A higher published SPL cab like the Genz is going to have a more attenuated deep low end, more 'goosed' mids, and hence sound 'louder' with fewer watts than a lower published SPL cab. The Acme is the extreme example of this, having a huge low end extension (which eats up lots of power), and hence a lower 'midrange to deep bass' response, making the cab less 'punchy', and hence seem 'less loud', even though it's probably putting out more deep bass volume per watt than the higher SPL cab.

With a significant amount of wattage, any 410 is going to be louder than any 210, but with very limited power, the more mid voiced, higher SPL 210 could very well sound significantly louder than the Acme 410. With 500+ watts, the 'lower' SPL 410 will still spank any 210 IMO and IME. With 100 watts, maybe not.
 
#3
markblasco said:
Does this mean that, given the same amount of power, the Genz Benz speaker cabinet will be 5dB louder, even though it is a 2X10 instead of a 4X10?
Click to expand...

Sensitivity varies with frequency, and must be measured and charted at no less than 30 frequencies to give even a rudimentary basis for comparison between different cabs. Without SPL charts sensitivity claims are meaningless, and real world comparisons impossible.
 
#4
billfitzmaurice said:
Sensitivity varies with frequency, and must be measured and charted at no less than 30 frequencies to give even a rudimentary basis for comparison between different cabs. Without SPL charts sensitivity claims are meaningless, and real world comparisons impossible.
Click to expand...

Per my previous post, I disagree that they are meaningless, as long as you realize they typically represent the voicing of a cab versus absolute volume across all frequencies.

There is a quite high correlation between the published SPL of the vast majority of bass cabs and the relative ratio of mid punch to deep bass, and hence 'perceived volume' in bass quitar amplification in a live mix. Of course, there is a price to pay with a very high SPL cab (as measured at 1K).... typically a lack of deep, low bass response (which may or may not be 'bad' depending on the playing context and tone goal).

However, +1 in general... I sure wouldn't use SPL or any other published spec as the primary piece of information when choosing a cab. However, you can be pretty confident that a very low SPL spec cab will have quite a deep low end extension and hence need more watts to push that wider tone into a room.
 
#5
Please let me clarify...

We use an average weigted sensitivity, the bandwidth based on the useable -3dB LF points of the cabinets in question. For bass cabinets, we typically use ~5k at the top end of the averaging because many folks prefer different tweeter attenuator settings. We also use 1/2-space measurements since this generally applies to how the cabinets are actually used.
 
#6
agedhorse said:
Please let me clarify...

We use an average weigted sensitivity, the bandwidth based on the useable -3dB LF points of the cabinets in question. For bass cabinets, we typically use ~5k at the top end of the averaging because many folks prefer different tweeter attenuator settings. We also use 1/2-space measurements since this generally applies to how the cabinets are actually used.
Click to expand...

That seems a reasonable approach, but if the LF -3dB point is 100 Hz a vented cab with a seemingly respectable 100dB average SPL ;) would only be at 76dB at 50 Hz. :(
 
#7
billfitzmaurice said:
That seems a reasonable approach, but if the LF -3dB point is 100 Hz a vented cab with a seemingly respectable 100dB average SPL ;) would only be at 76dB at 50 Hz. :(
Click to expand...

Fortunately, -3dB at 100 Hz is a pretty "easy" spec to meet in all but the most compact cabinets. Many of our cabinets are -3dB at 40-60Hz which seems to have just about the right feel for bass guitar and still retain the tonality of a front loaded non-horn type speaker.

You do point out how difficult it is to describe a complex multidimensional response with one simple, easily marketable number.
 
#8
OK, so the design that allows the acme cabs to get so low is the reason for the lowered sensitivity. Assuming that these measurements were both taken the same way, if you were to take out some of the low end information going into the acme cab (say a 6dB/octave filter at 50Hz), would you get more volume at the same power? Could an Acme 4X10 get the same volume as a Genz 4X10 if that low end energy wasn't there for the acme to have to pump out?
 
#9
markblasco said:
OK, so the design that allows the acme cabs to get so low is the reason for the lowered sensitivity. Assuming that these measurements were both taken the same way, if you were to take out some of the low end information going into the acme cab (say a 6dB/octave filter at 50Hz), would you get more volume at the same power? Could an Acme 4X10 get the same volume as a Genz 4X10 if that low end energy wasn't there for the acme to have to pump out?
Click to expand...


+1... quite a few who use the Acme's do this. Of course, if you are going to do that, then why not just get a cab that is voiced to deliver a tighter low end:smug:

Seriously, you might want to PM Alexclaber... he's an Acme user and also is VERY smart about where to set the hi pass filters, etc. to get the most out of these cabs.
 
#11
markblasco said:
Assuming that these measurements were both taken the same way, if you were to take out some of the low end information going into the acme cab (say a 6dB/octave filter at 50Hz), would you get more volume at the same power? Could an Acme 4X10 get the same volume as a Genz 4X10 if that low end energy wasn't there for the acme to have to pump out?
Click to expand...

Probably not. One of the tradeoffs (in general, not talking about any specific cabinet here) in achieving really extended low frequency response is that the voice coils are wound longer and this keeps more of the coil inside the gap under high excursion but a lower % in the gap at any one time under linear excursion. The wire outside the gap becomes a loss under lower excursion conditions. Also, there are other parameters, specifically the moving mass and compliance that are generally different between an extended low frequency design and a moderate design.
 
#12
markblasco said:
OK, so the design that allows the acme cabs to get so low is the reason for the lowered sensitivity. Assuming that these measurements were both taken the same way, if you were to take out some of the low end information going into the acme cab (say a 6dB/octave filter at 50Hz), would you get more volume at the same power? Could an Acme 4X10 get the same volume as a Genz 4X10 if that low end energy wasn't there for the acme to have to pump out?
Click to expand...
I don't think so. There's also the frequency response specs to consider. A reputable manufacturer will specify frequency response to within +/- 2 or 3 dB.

Therefore, there is no "extra volume" available in the midrange frequencies (except within the +/- 2 or 3 dB limits).

That said, one can gain a dB or two on the sensitivity number by raising the lower frequency limit, because of the typical rolloff there.

If there's a 5 dB difference between speakers, don't expect it to be erased by playing with the numbers. Rather, expect to take just a dB off the higher number. :D
 
#13
RockNRollAl said:
A reputable manufacturer will specify frequency response to within +/- 2 or 3 dB.
Click to expand...
In hi-fi, yes. Not with musical instruments. MI drivers with an average SPL of 95dB and a peak SPL of 105 to 109dB in the midrange aren't the exception, they're the norm. Which, unfortunately, opens the door for SPL claims that, while not exactly false, are still a long way from Kosher. :scowl:
 
#14
RockNRollAl said:
I don't think so. There's also the frequency response specs to consider. A reputable manufacturer will specify frequency response to within +/- 2 or 3 dB.

Therefore, there is no "extra volume" available in the midrange frequencies (except within the +/- 2 or 3 dB limits).

That said, one can gain a dB or two on the sensitivity number by raising the lower frequency limit, because of the typical rolloff there.

If there's a 5 dB difference between speakers, don't expect it to be erased by playing with the numbers. Rather, expect to take just a dB off the higher number. :D
Click to expand...


+1 on the 5db difference not being erased. My assumption has always been that most of those cab SPL ratings are based on that 1K test point, which maked the correlation with total volume a little loose when amplifying a bass guitar.

My point was that eliminating that deep low end, in my case, with the Acme's, allowed them to sound a lot louder in a mix with a moderate powered amp by reducing those very low freq's which tend to muck up a live tone (IMO). It also stopped those cones from pistoning so much resulting in the 'farting when slapped' to go away, seemed to reduce how hard the amp was working, and increased the relative mid-range response which made the cab 'sound' quite a bit louder in a mix.

The other 'problem' that a hi pass filter 'fixes' on the Acme's is that it seems to bring the mids into better balance with that massive bass response in an actual live setting. Those cabs can become very 'bass oriented' in a live setting. Given how our ears work, and how many rooms seem to absorb the mids and treble at a higher level than deep bass, having a cab that is 'relatively flat' down to the low 30hz level in a 'test chamber' can actually result IMO and IME in a VERY 'non flat' response in a room... bassy with a lack of even treble response and too polite upper mids.
 
#15
OK, so pulling the deep lows out of an acme won't necessarily allow it to get louder, but will allow it to sound cleaner at loud volumes?

I know at the same power the higher rated cabinet will always sound louder. I am just wondering if, at or near the max volume, pulling some of the lows out of the acme will allow it to sound louder if it is also given more power (to make up for the power pulled out with the low end)

Also, does anyone have a suggestion for a low cut filter that is rack mountable or small enough to stuff in the back of a rack? Is this a situation where I should be looking into a rack mount EQ, or is there something simpler/cheaper that will do the job?
 
#16
markblasco said:
OK, so pulling the deep lows out of an acme won't necessarily allow it to get louder, but will allow it to sound cleaner at loud volumes?

I know at the same power the higher rated cabinet will always sound louder. I am just wondering if, at or near the max volume, pulling some of the lows out of the acme will allow it to sound louder if it is also given more power (to make up for the power pulled out with the low end)

Also, does anyone have a suggestion for a low cut filter that is rack mountable or small enough to stuff in the back of a rack? Is this a situation where I should be looking into a rack mount EQ, or is there something simpler/cheaper that will do the job?
Click to expand...

It will sound louder... no one said it wouldn't:confused: Will it get a full 5db louder (which is huge, given the log nature of that scale)... probably not. Will it sound louder with a relatively low powered head if you limit that extreme low end response... absolutely. Again, most that use Acme's who know what they are doing do this exact thing.

Again, PM Alexclaber for the full deal (i.e., optimum hi pass point, etc.).

I, myself, would sell the Acme and get a higher SPL 410 if that is your main goal (or invest in a Carvin B1500 or similar amp with enough ooomph to drive the Acme appropriately). Even then, a hi pass filter will help.
 
#17
Well, I'm not at the point of selling the acme, I am just looking into options for ways to get a smaller or lighter rig that hits a similar volume. I don't need it to be super deep.

I am running it with an Eden WT800A, so I can give it 800 watts. I haven't turned it up that loud yet, but I have a feeling it would get me the volume I need.
 

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