jbl 2225h need box calc

[mastadon]

can someone run the bandpass calculater on these, and put specs up for a box that will help it reproduce the "B" string on a five string bass guitar. the box itll have to be tuned down pretty low, to hit 27hz.. thanx

[Ron E]

Originally Posted by mastadon

can someone run the bandpass calculater on these, and put specs up for a box that will help it reproduce the "B" string on a five string bass guitar. the box itll have to be tuned down pretty low, to hit 27hz.. thanx

I suggest you record that guitar and look at the spectrum. Its spectrum is likely dominated by harmonics with little fundamental. Another experiment - generate a test tone in audacity with 30, 60, 90, 120 Hz tones, then start reducing the level of the 30 Hz tone. The ear doesn't hear much difference because it "creates" the 30Hz tone from the harmonics. In other words, you don't need the low B as long as it does the harmonics properly. There is little need to go much below 35-40Hz with a pro rig. Doing 40Hz really loud is much more important than doing 20Hz or 30Hz...

[Brett]

I agree with Ron for a couple of reasons. First of all he is correct re our brains filling in the fundamentals. Next, go and measure some: even on a 34" scale 4 string the fundamental on most low E is much lower than the 2H. On a B it is even worse as the strings aren't long enough to support it.

Have you ever had 30Hz loud on stage (presume you want this for at least some live work)? It's very annoying and can cause all sorts of resonances and muddy the sound.

Also consider many of the popular BG rigs such as Ampeg 4 and 8x10 dive below 70Hz and yet are often described as having good fundamental tone. For recording direct with maybe some micced cab mixed usually in sounds best.

[davygrvy]

There are even some popular bass pre-amps from the eighties that did a 70 Hz high-pass for "marketing reasons" so they could sell you more speakers.. Names removed to protect the guilty, Peavey.

Have a look at this old, but popular cab and look at its response chart. Be concerned about getting enough top-end from yours.

[tomp787]

Hello,

Here is a bandpass designed by JBL for 2225.

http://www.jblpro.com/pub/obsolete/4685.pdf

Good Luck,
Tom

[djk]

Last time I checked, low B was 31hz (5-string bass).

2nd harmonic is usually 6dB~10dB higher.

[wg_ski]

Originally Posted by Ron E

There is little need to go much below 35-40Hz with a pro rig. Doing 40Hz really loud is much more important than doing 20Hz or 30Hz...

Doing 40 Hz really loud requires a box that can get down to the low 30's/high 20's, not one that unloads at 40 Hz.

[davygrvy]

Originally Posted by wg_ski

Doing 40 Hz really loud requires a box that can get down to the low 30's/high 20's, not one that unloads at 40 Hz.

Ummm, not exactly. I mean if we aren't talking 1/4 wave horns to get 40 Hz loud and say your using a tapped horn instead. 40 Hz can be the point where it unloads and is the loudest.

[mastadon]

you wouldnt know whats inside that box would you? or know where to find a pic of its guts, or schematic?? triple chamber bandpass

Originally Posted by tomp787

Hello,

Here is a bandpass designed by JBL for 2225.

http://www.jblpro.com/pub/obsolete/4685.pdf

Good Luck,
Tom

[Ron E]

Originally Posted by mastadon

you wouldnt know whats inside that box would you? or know where to find a pic of its guts, or schematic?? triple chamber bandpass

Most likely 2 x 6th order boxes , one for each woofer, except that one of the chambers is shared...just a guess, for each woofer, 100liters on one side, tuned to 24Hz, and 20 liters on the other, tuned to ~80-82Hz.