Can someone breakdown bass cab specs? What's important to know when reading the #'s

[orphan wells]

I was just looking at some specs on some swr stuff and i was just wondering the exact meaning of all the the sensitivity and SPL readings. someone told that the sensitivity is the most important thing in deciding the loudness of a cab but others tell me to look and the SPL. SWR Goliath III's SPL specs are 105 db @ 1watt 1meter they don't give a sensitivity reading, but it's frequency response is -3 db @40hz and 15khz. What is the -3 db? Could some one break down sinsitivity of a cab also?

[ClarkW]

"it's frequency response is -3 db @40hz and 15khz. What is the -3 db? "

 

I think this comes from the fact that it's a ported cab, which if you look in the last two days or so of this forum there was a good discussion on ported vs sealed cabs. Basically, there are air passageways built into the cab which make it particularly responsive (ie boomy or loud) for certain frequencies. The shape and size of those air passageways determines the "tuning" of the cab. A side effect is that it tends to lose a lot of luster (specifically, there is a marked ~3 decibel dropoff) below or above certain frequencies. That -3dB at 40 Hz is pretty nice and low; I'd assume that it's got a 15" or 18" cone?

[Si]

Hiya,

Right 3dB is the amount that the frequency response may drift from flat between the named frequencies. So at 50Hz it may be dead on the line but at 100Hz it may be -3db and at 1KHz it may be +3dB. As 3dB equates to twice as loud thats an awful lot of leeway.

 

Si

[getz out]

Originally posted by ClarkW:

That -3dB at 40 Hz is pretty nice and low; I'd assume that it's got a 15" or 18" cone?

Don't assume speaker size from 40 Hz; especially with ported cabs, cabinet volume (size) and port size and length have as much to do with this as a speaker. That's what makes 30 Hz possible with 10" speakers (check out Acme's specs, or the old Peavey cabs).

[rumpelstiltskin.]

firstly, the 105dB SPL spec that you listed is the sensitivity of the SWR Goliath III. i'll expand on that a little bit later, but i had to get that down to describe the following.

 

-3dB is sort of a standard way to describe frequency response of loudspeakers, whether they be for car audio, home audio, touring PAs, or instrument rigs.

 

what it means is that the speaker loses its ability to reproduce extremely low and high frequencies. the -3dB frequency gives you an idea of how low and how high the loudspeaker can reproduce musical signals before it starts to lose its effectiveness.

 

mathematically speaking, -3dB works out like the following. the sensitivity of the SWR Goliath III is 105dB at 1W signal (of unspecified frequency assumed to be 1kHz) provided to the cabinet and measured from 1 meter away (105dB @ 1W @ 1m). from that same 1 meter away with the same 1W power, a 40Hz tone is -3dB from that, or 105dB - 3dB = 102dB. this is also true for a 15kHz tone.

 

what that means is that the loudspeaker starts to get slightly quieter at 40Hz, and only gets quiter still as you lower the frequency from there. it also gets slightly quieter at 15kHz, and only gets quieter still as you increase the frequency from there.

 

-3dB is usually pretty useable -- 3dB of bass or treble boost to compensate is pretty easy to achieve from any 3-band shelving, semi-parametric, or parametric EQ. it's also not ridiculously quiet compared to the 0dB signal. -3dB is about 70% of the 0dB signal. going back to the Goliath III, its 102dB response at 1W at 1m @40Hz is about 70% of its 105dB specified response.

 

but, in the words of jack skellington , "what does it mean?! what does it mean?!"

 

if you only care about how loud you will get, especially at the expense of what you sound like, then certainly the sensitivity of a loudspeaker is the only spec that matters. however, frustratingly, most manufacturers, my employer included, rarely specify their sensitivity and max SPL ratings at useful frequencies, like 60Hz for bass, 30Hz for a subwoofer.

 

this means that the speaker may be very uneven in its response and very lacking in bass, but as long as it's loud at 1kHz, it can be said to have high sensitivity. this is not to say that we, the unsuspecting bass players, are being fleeced by the greedy and unscrupulous manufacturers -- we play these cabinets and can tell if they sound good and get loud. however, there's very little real information in a sensitivity spec, so it's not much more than a general guideline.

 

of course, sensitivity is all based on the same amount of power, so it's good for something. in other words, with the same 1W at 1m, the 105dB sensitive Goliath III is louder by 9dB than the 96dB sensitive Acme Low B-4. since neither lists their maximum SPL, who knows which will get louder if you have the watts to feed them, but we can certainly say that the Goliath III will be much louder than the Low B-4 with the same amplifier.

 

hopefully this is the sort of information you're looking for. i'm not as much into speakers as i am into amps and electronics, but i can wax knowledgeable to a certain degree. feel free to ask any other questions you have about it, or for clarification. i try to explain things clearly, but sometimes i still go a bit over people's heads. so if i need debrainify something, please let me know.

 

robb.

[_Sweet Willie_]

The website for Eminence speakers has some good resources about some of this. One of the things that Eminence does is give you the loudness of their drivers at a whole range of frequencies. Here's the link to their info about sensitivity:

 

Eminence sensitivity resource

 

Generally, it's more useful to us to see how a driver or, even better, a driver-loaded speaker cab performs at a variety of frequencies -- i.e., how loud is it at 50 Hz, 150 Hz, 250 Hz, 500 Hz, 800 Hz, etc. Unfortunately, as robb. pointed out, most manufacturers just give us info a 1 kHz. (Interestingly enough for me personally, 1 kHz is one of the frequencies I like to cut in my EQing practices!)

[Lawnmower8]

What about things like voice coil size, magnet weight, cone materials, etc? As well as general construction, materials, weight, etc.

The cabinet's only as good as the speakers that go in it...

[orphan wells]

Great feed back. thanks. second question. Would a 700 watt goliath III be louder than say a Trace Elliot that is only rated at 300 or 400 watts. What effect dose power handling have on sound/volume. I guess what I'm asking is more watts = more __________. this is all assuming that the cab is supplied with its RMS power handling.

[getz out]

Originally posted by Lawnmower8:

The cabinet's only as good as the speakers that go in it...

Agreed, but the opposite is also true; put an 18" woofer in a 1 cubic foot cabinet with an open back, and it's useless. It's like having a Porsche without tires.

[rumpelstiltskin.]

Originally posted by Lawnmower8:

What about things like voice coil size, magnet weight, cone materials, etc? As well as general construction, materials, weight, etc.

these are also important to some degree. given equal power ratings, these factors help determine factors such as maximum SPL, sound, and durability. especially with something like cone material, the sound is going to change -- tighter, deeper -- but it's not something you can really qualify without listening.

 

things like voice coil diameter and magnet weight also serve as indicators, but there's never anything concrete about it. you just have to play the cabinet. for example, take the bergantino HT112 and the aguilar GS112. both 12" two-way bass cabinets. the GS112 has a 56oz. magnet, whereas the bergantino has an 80oz. magnet. what this probably means is that, while both are rated at 300WRMS, the HT112 probably can achieve a higher max SPL, or perhaps has more excursion, which translates to tighter low end. it's hard to say. of course, these are not neodymium magnets, which provide greater performance at lighter weights.

 

voice coil diameter is usually a factor in heat dissipation, which improves durability, and perhaps sound quality for various reasons, but it's hard to say without playing it first.

 

there is no magic bullet. you'll only end up frustrated trying to find a magic formula for good speakers. you just have to play through them and develop familiarity with different speakers.

 

robb.

[prophetgtree]

What I want to know is what frequency goes with what pitch. For example, a low B is what frequency? And a low E is what frequency? If someone could give me some clue as to what frequencies the open strings are, or how different notes and ocvtaves relate, that would be awesome!

[bassplayer5217]

i know for sure that the low fSharp string is 21 Hz, so an octave = double that, thus second fret on the e string is 42!

 

remember, though, that just because a frequency can't be played or even at a low volume doesnt mean the human ear cant put it all together

 

my crate bx-25 only goes down to around 40-42 at -10 dB, but our ear naturally adds the lower harmonic and little difference is heard compared to, say an epifani 21 inch woofer that plays down to 20 Hz when playing a standard four string

 

peaceOUT

[_Sweet Willie_]

Originally posted by prophetgtree:

What I want to know is what frequency goes with what pitch. For example, a low B is what frequency? And a low E is what frequency? If someone could give me some clue as to what frequencies the open strings are, or how different notes and ocvtaves relate, that would be awesome!

Here are some links I found using a Google search.

 

Pitch frequencies

 

Where math meets music

 

Have fun!

[rumpelstiltskin.]

the important ones -- to save you the trouble of following sweets' well-researched links -- is that lowB = 31Hz and lowE = 41Hz.

 

what you hear the most, however, are the 2nd harmonics, or double the frequency. so when you play an open E-string note, you're hearing mostly 82Hz. an open B-string is mostly 62Hz. this is why bass preamps often have controls in the 40Hz - 60Hz range. sometimes they have a 30Hz bass control.

 

robb.

[gilmanta]

Great links Willie, thanks

[BenLoy]

All that info is great...but none of it really beats standing in a room with a full band playing through the cabinet and thinking "this cab sounds good" or "this cab sounds like s**t."

 

I trust reviews of cabinets or judging for myself with my own ears as opposed to scrutinizing specs.

[_Sweet Willie_]

Originally posted by BenLoy:

I trust reviews of cabinets or judging for myself with my own ears as opposed to scrutinizing specs.

I agree -- the ultimate test is playing and listening to the cab.

 

However, in the mad, mad world of many shapes, sizes, and configurations of bass cabs, specs can help you do some weeding out so that you're not trying to find and listen to hosts of cabs. That said, the "specs" that usually do the most for me in the initial weeding out process have to do with cab impedance, cab power handling, and cab dimensions -- not SPL. However, I do also like to know something about the freq range the cab handles well.

 

Word of mouth and reviews also play a role in the weeding out process. And by reviews, ratings mean less to me than the actual descriptive text of the review. I love hearing from another bass player (like from this board!) that the Acme Low B4 rocked his world or that she totally cut thru the band with her Bergie 322. What folks here say definitely brings stuff to my attention.

 

When I hear live music I also pay close attention to what gear the bass player is using in the context in which he or she is playing. Sometimes this means I add something to my "check this out!" list.

 

But any final decisions come down to what my ears hear when my hands are playing!

 

Peace.

[orphan wells]

Thanks for all of your input guys. I think my reason for trying to get some of this knowledge is, i live in a place where there isn't much of a scene therefore not many stores to support it. the stores we do have stock very limited bass oriented products. Especially cabs (can't tie all their money up in inventory) I myself am a firm believer in judging things in person and actually playing through them. In my neck of the woods it can be kind of difficult. The nearest guitar center is in Atlanta (7 hours) I just wanted to know how much one can actually tell from the specs. You guy always do a great job with feed back. keep it up. By the way i did take a chance with my Epifani and it was the best blind, deaf decision I ever made

[Tom Capasso]

Orphan Wells,

 

You should consider a shorter trip to BassCentral.

 

You can usually get a high quality product by buying a high quality name. That doesn't mean it will sound the way you want it to sound.

 

Good luck with the new cab!

 

Tom