Needed: Primer on Bass Frequencies

[doc540]

Does a "primer" exist on this forum outlining the basics of bass frequencies? If not, would some of you contribute a beginner's primer on this subject?

I'm dialing in a new bass rig's crossover and realized my knowledge is really limited in this area.

Since I'm playing a four string Jbass and biamping a single 210 cab and a single 15 cab, I'm interested in understanding more about the bass sound spectrum and what I should be shooting for.

Thanks!

[Sven]

OK;
The A above middle C is A=440
The A below middle C is A=220
The A at bottom space of the bass clef is A=110
The A 3 ledger lines down is A=55

Since bass guitar plays 1 octave below what is written, (like a String bass), that makes the open A string 55Hz,

[doc540]

Thanks!

How does that translate into EQ'ing an amp?

[Sven]

Originally posted by doc540
Thanks!

How does that translate into EQ'ing an amp?

Well, that's going to be a matter of personal taste.

It's also gonna depend on how your rig is voiced, the strings you use, and what kind of bass you play and how you play it. I like the bass sound to be very full and very clean, but You may disagree. Sorry, but you're probably going to have to use the same method everyone else does - trial and error.

[doc540]

My bad.

Let me be more specific:

Jbass four string

The Avatar single 15 enclosure is tuned to 51 Hz and -3dB is 64 Hz while the 210 enclosure is tuned to 63 Hz and -3dB is 76 Hz.

In light of that info, is most bass "tone" developed between 50Hz and what? I'm trying to learn what sound spectrum most bass amps operate in.

Thanks

[doc540]

Thanks, that helps my understanding of the frequencies.

However, the specific problem I'm running into is this: when I set the low channel (when biamping) between 150-200 and try to set the high channel above 350-400, I lose all my gain and get hardly any volume outta the 210 cab.

But if I set them both to 200, identical settings, I get plenty of gain out of the 210.

I'm a dumbass so what am I missing here?

[doc540]

(cowering under his desk when the teacher shouts at him)

bbbbbut.....I...I....don't know why Yamaha built it with two variable sweeps. HONEST, I DON'T!!


I think I'm just gonna set'em both to 100 and balance their volumes with the respective gain controls. Tone-wise I'll use the master tone controls and some day venture into parametric land.

I became confused when I set both to 400 and lost all the gain out of the high side.

Do I have to do any, like, detention or writing sentences?

[doc540]

I'll try to scan a better picture of the back of the unit. The front pic I posted is hugely clear.

YES! They can be overlapped!

[doc540]

I'm trying to get a clear scan of the back panel. MrsDoc found the original manual I thought had been lost years ago.

[doc540]

Ok, I'm gonna try to scan the manual page explaining the crossovers. It has superneato technical spacey graph-like thingies!

[Sven]

It seems to me that you definately want to overlap the crossovers, but that the specific amount of overlap and the frequency where you do it will be what makes the difference.

[doc540]

Here's the crossover page from the manual. If it's too big I'll repost it as a link.

[doc540]

Oh, I've read it more than once. But it didn't help me with the concept of overlapping them.

I understood not to set them too far apart. For instance, I can set the low side at 200 but if I set the high side even slightly higher at 400 I lose all gain and hardly get any sound out of the high side (even with the gain pegged).

I didn't think the difference between 200 and 400 was that great, but that shouldn't be surprising since I have little or no understanding how this dual level crossover works.
I'm just a

[doc540]

I hope you find one, get it dialed in and then explain to me how to do it!

btw: I see them once in a while for around a hundred bucks and change. They seem to still get good reviews, too.

[doc540]

I think I am, but I didn't realize I should be setting the high side so far down with the low side.

150/200 sounds good to me, but I was surprised and thought I was doing it all wrong. My ears were happy though!

[Winston]

The way my stuff is set up I have just one crossover point and I have been experimenting a lot lately with that crossover point and the actual output levels for the highs and lows.

This is probably not much help to you, but I the only thing I’ve really found is that I have to adjust the crossover point and those levels every time I move the rig. Once I spend all day getting my perfect tone in my living room, it’s totally different in the practice space with the other instruments and it needs tweaking. FWIW, the crossover point between my 4x10 and 1x15 always sounds best to my ears somewhere between 110 and 250 Hz. Right now it’s about 130 Hz.

I may also be totally crazy, but I really think that the cab placement can change the tone, the volume, and the crossover point and output levels. I have just been experimenting with the 4x10 set up next to the 15 rather than on top and I am really getting excited about the tone I’m getting. I’m anxious to see what this sounds like with the whole band.

Sorry, I’m a dumbass too. Great thread, tho. :)

[doc540]

We dumbasses need to stick together (but in the literal sense, ok?).

:nelson

[Winston]

:lol2 Fair enough.

I was trying to take a pic of that set up for you but my man Forest thought that the camera looked tasty and he wanted to lick it.



so I gave him a bone a took this one.



I may be a dumbass, but I swear that the cabs sound different next to each other instead of on top of each other.

[doc540]

So, you're suggesting I experiment with the 2-10 and 1-15 in different setup configs?

hmmmmmmm....something else to mess around with.

I like it!

[davey]

Originally posted by Winston


I may also be totally crazy, but I really think that the cab placement can change the tone, the volume, and the crossover point and output levels. I have just been experimenting with the 4x10 set up next to the 15 rather than on top and I am really getting excited about the tone I’m getting. I’m anxious to see what this sounds like with the whole band.

I don't know if you guys are familiar with the "coupling effect" of cabinets. It basically is that 2 cabinets are loud, and 2 cabinets either right next to each other or on top of each other is loud +1. Does that make sense?

This is a post from someone at the LPF from a while ago that explains it a bit better than I can. Everything below this point in this post is his.

As a rule, by doubling the speaker surface area (and keeping all other factors the same, such as load impedance, making sure that the speakers are in phase, etc.), you will gain 3dB of acoustic output. This is the equivalent of doubling your amplifier power driving the load.;\

At relatively low frequencies, a 6-dB increase occurs when the cones exhibit "mutual coupling." Mutual coupling occurs at frequencies whose wavelengths are longer than 1/4 of the center-to-center distance between the cones. The highest frequency at which mutual coupling occurs may be calculated using the equation:

f = 3000/dMax

where dMax is the distance between the cones, and f is the highest frequency in Hz at which mutual coupling occurs.

This effect is most pronounced with bass arrays, but it does explain why a 8x12 stack sounds alot bassier than a 2x12 combo. For most guitar applications, mutual coupling isn't as signifcant as it is for a bass, as most of the guitar's range falls above the value of f.

Practically speaking, doubling your speaker count (and keeping everything else equal) will get you +3dB every time that you do it. This means that replacing your 7-watt amp's 1x12 cabinet with a 2x12 will give you the +3dB sound of a 14-watt amp. Replacing the 1x12 with a 4x12 will give you +6dB, equivalent to a 28-watt amp. Replacing the 1x12 with a full 8x12 stack will give you +12dB, or the equivalent of a 56-watt amp driving a 12-inch speaker.

One variable that confuses the issue, though, is that by replacing a 1x12 with 2 4x12 cabs, each speaker is handling less of the amps voltage output. This means that speaker breakup occurs later, and you get an overall cleaner tone out of the speakers, which lets you drive the amp a little harder still.

Unfortunately, the solution to the problem isn't as simple as the speaker and acoustic output doubling equations described above. Getting THE TONE is a combination of making the amp work hard AND the speakers work hard, so that each one is doing its share of the work.

Taking a little amp like a Champ and making it drive a full stack can certainly get you some good sounsd, but in that scenario you'll be hearing more of the amp and less of the speakers. The speakers certainly won't be breaking up as much as they would if there were less of them handling the load.

How you make the combination work for you all depends on which part of the signal chain you really want to hear!

The moral of the story is that there is no simple, easy solution to GAS. You still may have to arm yourself with an array of different heads and cabinets to be truly happy!

HTH!



Regarding mutual coupling, it is a fact that this phenomenon occurs at the frequency limits described; if the drivers are operating in phase, the only significant variable is the center-to-center distance between the cones. For 12-inch speakers with a center-to-center distance of about 14-inches, this phenomenon will provide an additional 6dB below about 200 Hz.

Mutual coupling is a real phenomenon. Its exactly the reason that guys like David Eden are putting 4 10-inch speakers in a cabinet to provide better bass response than a 1x15. If it works for a 4x10 cabinet, it will work for a 4x12. Mutual coupling is exactly how those crazy metal deaf guys in Manowar got into the Guinness Book of World Records for playing a concert at 129.5 dB.

EDIT: I should have edited that a long time ago. My bad.