Help with amplifier question

[LowDownDave]

Well, there are "supposedly" no dumb questions, so here goes...

I've recently been trying to sort out bass amp information as I intend to upgrade, but I was curious about frequency response measurements. What I'm trying to figure out is are the frequencies of specific notes (eg. open E string for "E") constant and if so is there a table of values of these frequencies which corresponds to the particular notes on a bass scale? Also if a cabinet is rated for a particular low frequency rating does this mean a note below this low frequency rating would not be heard through this cabinet?

I could be way off here, because I assume the majority (if not all) bass cabinets are designed to handle the majority (all) of downtuning possibilities, but even so I'd still like to find a chart of frequencies vs. notes if such a thing exits (or as stated earlier perhaps I have the wrong idea about this completely, and if so please set me straight!)

Cheers!

 

[AnthonyD]

This might be helpful...

 

[maddog]

Well, there are "supposedly" no dumb questions, so here goes...

I've recently been trying to sort out bass amp information as I intend to upgrade, but I was curious about frequency response measurements. What I'm trying to figure out is are the frequencies of specific notes (eg. open E string for "E") constant and if so is there a table of values of these frequencies which corresponds to the particular notes on a bass scale? Also if a cabinet is rated for a particular low frequency rating does this mean a note below this low frequency rating would not be heard through this cabinet?

I could be way off here, because I assume the majority (if not all) bass cabinets are designed to handle the majority (all) of downtuning possibilities, but even so I'd still like to find a chart of frequencies vs. notes if such a thing exits (or as stated earlier perhaps I have the wrong idea about this completely, and if so please set me straight!)

Cheers!

Open E on a bass is about 41Hz. As you go up an octave, you double the frequency. Making a rough chart should be pretty easy from there. Rossing's The Science of Sound has several charts relating notes and frequency. Probably best to peruse some audio physics books in your local library or try Google.

To keep the low frequency response question simple, you can get some use below the given low frequency rating but I wouldn't count on it.

 

[Freddy-G.]

Could that be why the low B on a 5-string is a tricky note to reproduce correctly? It's that most cabs are not rated below 40hz.

 

[adouglas]

You don't need a table...all you need is the frequency of one note and a basic understanding of how the physics of sound works. Understanding how things actually operate beats having a chart and no clue how the world works any day of the week.

The low E is, IIRC (and somebody correct me here if I've got this number wrong, please) 40 Hz.

The basic physical principle is that each octave equates to doubling the frequency.

So, the E on the second fret of the D string is double the frequency, or 80 Hz. Simple, no? And the next E up, the E on the 9th fret of the G string, is 160 Hz. And the E on the 21st fret of the G string is 320 Hz....

From this you can figure out anything.

Or you can run it the other way. You know that concert A pitch is 440 Hz. Half that is 220...half that is 110...half that is 55. So your open A string is 55 Hz.

And so on. If you go through and do the math you can get exact frequencies, but for your purposes you probably only need to get close enough for government work...e.g., the low B on a 5 string isn't exactly 30 Hz, but it's within a few Hz of that.

The fundamental note is only part of the story, though....you also have to remember that there are lots of harmonics going on, all of which have specific mathematical relationships to the fundamental.

 

[adouglas]

Oops, I see somebody already posted essentially the same thing.

Here's a question for any cabinet gurus:

It stands to reason that a cabinet that's tuned to some harmonic of one of the fundamentals will resonate at that frequency, yielding a boomy note.

e.g., a cabinet tuned to 55 Hz ought to yield a boomy low A.

Is there anything in this, or am I completely out to lunch again?

 

[maddog]

Oops, I see somebody already posted essentially the same thing.

Here's a question for any cabinet gurus:

It stands to reason that a cabinet that's tuned to some harmonic of one of the fundamentals will resonate at that frequency, yielding a boomy note.

e.g., a cabinet tuned to 55 Hz ought to yield a boomy low A.

Is there anything in this, or am I completely out to lunch again?

It is either due to mis-tuning the cabinet or cabinet dimensions causing standing waves. Will elaborate more if wanted but i'm out the door for work.

PM me, I can give you a whole list of references as well as some websites that might help.

Tom

 

[adouglas]

Thanks, but I'm not interested enough to do any serious homework. Just curious.

I knew about the standing wave deal...that's also why certain rooms sound awful, right?

I've been in restaurants where the acoustics were so bad that everyone in the place would start talking just a little louder to be heard by their dinner companions...eventually leading to an incredibly loud and unpleasant experience.

 

[Golem]

Thanks, but I'm not interested enough to do any serious homework. Just curious.

I knew about the standing wave deal...that's also why certain rooms sound awful, right?

I've been in restaurants where the acoustics were so bad that everyone in the place would start talking just a little louder to be heard by their dinner companions...eventually leading to an incredibly loud and unpleasant experience.

Ohhh. I had always thought they just got louder and louder b/c they were drinking more and more as dinner progressed. Plus, some of them are married [to each other, I mean] so the conversation naturally includes more disagreements than agreements as the evening drags on......

 

[LowDownDave]

Thanks everyone, very helpful. Adelucia, that's the exact chart I found when doing my initial websearch before posing this question to the forum, but as with all things "internet" I wasn't sure whether I should have accepted it as "gospel" or not, so thought I'd try to confirm things with "the experts".

But just as Freddy-G stated, I've seen most cabs (the ones I've bothered to check out the frequency response data on) have a low response of about 35-40 Hz, so are these cabs not "useable" when playing a 5-string low B? And what with the relative popularity of 5 string basses, why aren't more cabs designed to produce lower frequencies (or perhaps this is due to a difficulty with the sound physics of which you can tell I know very little)?

And I assume that even though these low frequency data ratings are listed, it must be possible to reproduce notes lower than the ratings suggest, seeing as one can loosen the E string below what the low frequency rating is on a particular bass cab and still produce a sound.

 

[adouglas]

Well, it's not as if the cabinet goes silent below a certain frequency...it just doesn't reproduce those frequencies quite as efficiently as a bigger cabinet with bigger drivers. You'll still hear sound, to be sure.

The cabinet won't be FLAT. But flat cabinets don't necessarily sound good...just accurate.

There's also this interesting phenomenon that I know very little about, which I believe is called "psychoacoustics," in which your brain fills in sounds that aren't really there.

I think it works like this: a cabinet that reproduces the harmonics of the low notes well can trick your ear into hearing a strong fundamental even if it's not all that strong in reality...once again, I'm not at all sure of the accuracy of this, and invite correction.

My rig has a small 1x15 Flite Sound cabinet driven by preamp/power amp rack, and I also run a line into a Bose PAS with one woofer unit. The Bose also carries vocals and one channel of a drum machine.

So all told, my rig has 1x15, 2x5.5 and 24x2.5 drivers, being driven by a grand total of something on the order of 1350 watts. It goes boom, quite nicely.

Neither the Bose nor the Flite are "rated" all that low (not surprising...the Flite is only about the size of a 19" TV, and the Bose woofer is the size of a bread box), but I get plenty of thump out of my low B string. Put it this way... I have no complaints. If I turn up the low EQ on my bass, everything in the room starts rattling so bad I can't play. So I leave the low EQ flat. I think that's a good indication of having enough low end.

Could I get MORE thump out of a huge, heavy box with 18 inch drivers in it? Probably. Would it sound better? Don't think so, but I might be wrong.

There's more to life than specs.

 

[Tajue17]

WOW you guys get pretty technical sometimes.

 

[adouglas]

Sorry about that...I'm a left-brain kind of guy (as I type this the background is a History Channel documentary about nuclear energy...and I listened to a Richard Feynman physics lecture on my iPod at lunch).

Doesn't stop me from having a fine old time playing bass, though....

 

[maddog]

I knew about the standing wave deal...that's also why certain rooms sound awful, right?

Yes.

I've been in restaurants where the acoustics were so bad that everyone in the place would start talking just a little louder to be heard by their dinner companions...eventually leading to an incredibly loud and unpleasant experience.

Actually, that is usually due to the sound guy not knowing what the master volume is for.

 

[maddog]

But just as Freddy-G stated, I've seen most cabs (the ones I've bothered to check out the frequency response data on) have a low response of about 35-40 Hz, so are these cabs not "useable" when playing a 5-string low B?

No, they should be useable. Depending on how they specify the cabinet, that 35-40Hz number is at the -3dB, -6dB or -10dB point below average. Because of acoustics, the -10dB point is still plenty useable. Especially with room gain (sound reinforcement due to nearby walls). Playing an outdoor gig is the true test of a cabinets low end.

And what with the relative popularity of 5 string basses, why aren't more cabs designed to produce lower frequencies (or perhaps this is due to a difficulty with the sound physics of which you can tell I know very little)?

Hit the nail on the head. The iron clad laws of physics limit the ability to reproduce the low end. Either need bigger cabinets to create the lower resonances, or more power and power handling/longer travel to EQ the deeper bass. Most bassists I know complain enough about lugging around their 100lbs cabs.

And I assume that even though these low frequency data ratings are listed, it must be possible to reproduce notes lower than the ratings suggest, seeing as one can loosen the E string below what the low frequency rating is on a particular bass cab and still produce a sound.

You still reproduce the notes below that number, it is just not as loud as above that number. Depending on room gain and the roll off characteristics (how quiet it gets as the notes go lower) you should be able to get useable low B output out of a cabinet rated to 40Hz. Rated down to 35Hz would be better. Best bet is to go listen to the cabinet and see for yourself.

 

[maddog]

Could I get MORE thump out of a huge, heavy box with 18 inch drivers in it? Probably. Would it sound better? Don't think so, but I might be wrong.

There's more to life than specs.

Nah, I think it is really that there is more to life than lugging around some 1,000 lb. coffins.

 

[Psychicpet]

some of the tightest, and most clear low end I've heard at moderate volumes came out of this cabinet:
l'il fella

but there is some very good and funky physics behind these cabinets:
l'il BIG fellas

I'm currently running this and it's killin':
bella bella!

but ya really can't argue with the grand pappy:

was running my MarkBass head through a '70s 8x10".................. no, the 'B' wasn't super tight but good lord did it rock!