Bass Cabinet Frequency Response (long-ish)

bobalu · #1 07-26-2010, 12:45 PM

We're all familiar with the advertised "frequency range" that sometimes forms part of the cabinet specs. provided by the manufacturers. A typical example would be "55Hz - 22KHz" or something like that depending on the driver.

I'm pretty sure that this information isn't really that useful in isolation unless you know what db level it relates to(? I may be wrong here as well). But that's where I have no idea what they're talking about.

For those electronics experts here (and thank god you are here!), what exactly does the following mean? (as an example only).

A 500 watt 8 ohm 410 sealed cab with a stated frequency range of:

42Hz-18kHz, at -10db points; and 55Hz-14kHz at -3db points. no charts or graphs.

The negative "db points" is really perplexing to me as is the db point itself. Is that good, fair, poor? What exactly does that mean? Do you need to compare these exact specs with another cab to draw any conclusion, or are you able to evaluate the performance of a cabinet on its own based on this information?

I'm hoping that its not too complicated to explain in semi-layman terms.

rpsands · #2 07-26-2010, 01:09 PM

Sensitivity is down 10db (e.g. a 100db cab is 90db sensitivity) @ 42hz. Sensitivity is down 3 db (100 db cab is 97db) at 55hz.

Mr. Foxen · #3 07-26-2010, 02:51 PM

If you had a perfect speaker, to simulate the response of that speaker, you would pull down your graphic eq by 10db on the 42hz slider and the 18khz slider, and 3db on the 55hz and 14khz sliders, roughly. Alternatively, you'd do the opposite to eq the speaker flat.

bobalu · #4 07-26-2010, 07:34 PM

O.k., thanks guy's. I still don't understand the significance of this specification though. Anyone else?

MIJ-VI · #5 07-26-2010, 08:25 PM

I'm not an expert but I believe that spec. describes the cab's frequency response both: in terms of its maximum bandwidth (42Hz-18kHz, at -10db points); and that portion of the bandwidth which makes a difference that one can actually hear and use (55Hz-14kHz at -3db points).

billfitzmaurice · #6 07-26-2010, 08:28 PM

Quote:

Originally Posted by bobalu

O.k., thanks guy's. I still don't understand the significance of this specification though. Anyone else?

-3dB is the half power point. -10dB is the half volume point. Without charts one can't compare specs, as manufacturer's published specs are as honest as a politician's campaign promises.

bobalu · #7 07-27-2010, 10:45 AM

O.k., so my conclusion would be that this cabinet specification (in the form most manufacturers publish them at the end of a user manual or advertising spec. sheet) is virtually useless and meaningless. Why am I not surprised.

rpsands · #8 07-27-2010, 10:57 AM

Pretty much correct. You can use it as a guideline to see which manufacturers are lying and which aren't though (and most of them are lying).

BassmanPaul · #9 07-27-2010, 01:27 PM

Acme is one of the few whose frequency response figures are accurate. They are about as HiFi as bass cabinets get.

Paul

Mike Dimin · #10 07-27-2010, 01:35 PM

Manufacturers do not necessarily lie about the response curve, some just measure it differently. There are "industry norms" that not all follow. Also these specs are really NOT a good indicator of how a cab will sound.

check this out

http://eaamps.com/index.php?p=kevlar&m=tech

billfitzmaurice · #11 07-27-2010, 01:39 PM

Quote:

Originally Posted by Mike Dimin

some just measure it differently. There are "industry norms" that not all follow.

Certainly it when it's in their interests not to follow them.

bobalu · #12 07-27-2010, 01:45 PM

Quote:

Originally Posted by rpsands

Pretty much correct. You can use it as a guideline to see which manufacturers are lying and which aren't though (and most of them are lying).

But I don't see how you could even use it for that. It just has no significance on its own.

"Manufacturers do not necessarily lie about the response curve, some just measure it differently. There are "industry norms" that not all follow. Also these specs are really NOT a good indicator of how a cab will sound".

I can understand that. But I really have only seen response curves for drivers/speakers (On Ted Webers site, for example). Once installed in a sealed cab with other speakers, won't that change things? I assume there are response curves and charts for "cabinets" as well(?). You never seem to see these. (maybe I live under a rock, I don't know?

)

billfitzmaurice · #13 07-27-2010, 01:55 PM

Quote:

Originally Posted by bobalu

But I don't see how you could even use it for that. It just has no significance on its own.

"Manufacturers do not necessarily lie about the response curve, some just measure it differently. There are "industry norms" that not all follow. Also these specs are really NOT a good indicator of how a cab will sound".

I can understand that. But I really have only seen response curves for drivers/speakers (On Ted Webers site, for example). Once installed in a sealed cab with other speakers, won't that change things? I assume there are response curves and charts for "cabinets" as well(?). You never seem to see these. (maybe I live under a rock, I don't know?

)

Above roughly 200 Hz the cabinet has no effect, so what's seen on the driver data sheet will be seen in the cab, if it's a single driver box. If it's a multiple driver box with drivers horizontally placed the works gets totally mucked up, if vertically placed the response stays uniform. Of course, most multiple driver cabs don't have them vertical...

Below 200 Hz the cabinet is as important as the driver. Accurate measured charts are commonplace in the PA genre, non-existent for electric bass.

bobalu · #14 07-27-2010, 02:02 PM

Quote:

Originally Posted by billfitzmaurice

Above roughly 200 Hz the cabinet has no effect, so what's seen on the driver data sheet will be seen in the cab, if it's a single driver box. If it's a multiple driver box with drivers horizontally placed the works gets totally mucked up, if vertically placed the response stays uniform. Of course, most multiple driver cabs don't have them vertical...

Below 200 Hz the cabinet is as important as the driver. Accurate measured charts are commonplace in the PA genre, non-existent for electric bass.

I knew I would learn something here.............

rpsands · #15 07-27-2010, 02:43 PM

Quote:

Originally Posted by bobalu

But I don't see how you could even use it for that. It just has no significance on its own.

The limitations of cabinets based on their volume and the technological limitations based on driver size can give you a good idea of whether or not a manufacturer is lying.

For instance, in a standard 2x10 cabinet with <1 cubic foot per driver, a claimed sensitivity above 96-97db is purely a fiction unless the low end response is seriously sacrificed. You can be pretty sure that if a company claims 100db sensitivity AND a -3db point of 45hz for a 2x10, they are lying.

If you take the best drivers available and model them in cabinets of various sizes you can easily get a ballpark of the low end rolloff that goes along with what cabinet sizes and sensitivities.

Mike Dimin · #16 07-27-2010, 03:14 PM

Then there are different cab designs, like EA's Transmission Line which can provide up to a half octave below the fundamental resonance of the driver. It is more than just the driver in a sealed cab. If that were so, all cabs would sound the same. It is knowing how to tune a cab and how to design a cab that makes all the difference

okcrum · #17 07-27-2010, 03:43 PM

Quote:

Originally Posted by billfitzmaurice

-3dB is the half power point. -10dB is the half volume point. Without charts one can't compare specs, as manufacturer's published specs are as honest as a politician's campaign promises.

The -10 dB is using the 10 X log(base 2) "psychoacoustic" formula, yes? Not SIL(-3) or SPL(-6)?

Too many formulas...

1n3 · #18 07-27-2010, 10:50 PM

If you missed it, I recommend this recent thread: sensitivity or frequency response for cabs?

bobalu · #19 07-28-2010, 09:19 AM

Quote:

Originally Posted by 1n3

If you missed it, I recommend this recent thread: sensitivity or frequency response for cabs?

Thanks 1n3. I saw that thread but I had some very pointed and specific questions not really covered in it, so I posted separately. Good thread discussion though.

naturalkinds · #20 07-28-2010, 10:24 AM

This is somewhat on topic...

Why, in general, would a four-string bass player -- with no need to play below E -- care about getting a cabinet with very low frequency response? I certainly see the prima facie appeal for someone who plays notes with lower frequencies, like a five-string player. What is gained by, say, me plugging into a speaker with very low frequency response, like an Acme? (Leaving out of consideration the other reasons I might be drawn to Acme in the first place, e.g., the three-way, relatively flat performance.)