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Old 2nd July 2011, 04:43 PM   #1
Vibeguy is offline Vibeguy  United States
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Default IB power versus xmax question

A long,long time ago I played bass guitar thru a Fender open backed 4 10 Bassman amp, 50 watts tube.I see that Parts Express has their 292-412 cheep 12 on sale.
Four of these in an open back box,the Qts is 1.54, Fs is 35,xmax is 3.5 mm.
At what power level do I run out of xmax for open E, 41 Hz?
Or would this be only suitable for guitar at 82 Hz?
Trade offs for U or H frame depth, etc.
Thanks!
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Old 2nd July 2011, 05:14 PM   #2
60ndown is offline 60ndown  United States
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GRS 12PF-8 12" Paper Cone Foam Surround Woofer

that one ?

id guess you could run maybe 100 watts int 4 of them (open back) without issue.

would be loud enough for playing with a drummer (just)
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Old 2nd July 2011, 08:47 PM   #3
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by 60ndown View Post
GRS 12PF-8 12" Paper Cone Foam Surround Woofer

that one ?

id guess you could run maybe 100 watts int 4 of them (open back) without issue.

would be loud enough for playing with a drummer (just)
Hi,

Get acquainted with HR and you can reply more accurately.

b
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File Type: jpg 4xGRS-12PF-8_H-Frame.JPG (250.9 KB, 116 views)
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Old 2nd July 2011, 10:05 PM   #4
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Bjorno;

Why the two zero length, zero area segments between the front and rear chamber? I have never used HR to model OB before.
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Old 2nd July 2011, 10:11 PM   #5
60ndown is offline 60ndown  United States
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Quote:
Originally Posted by bjorno View Post
Hi,

Get acquainted with HR and you can reply more accurately.

b
looking at your graph i see 100 w max?
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Old 2nd July 2011, 11:13 PM   #6
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Quote:
Originally Posted by 60ndown View Post
looking at your graph i see 100 w max?
With a 50 Hz HP.
EG is voltage, voltage squared /impedance ends up with the speaker hitting Xmax at 9.5 watts, a whopping 100 dB at 40 Hz.

Open baffle can sound OK for musical instrument use, but they don't make low bass for squat.
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Old 2nd July 2011, 11:37 PM   #7
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by mashaffer View Post
Bjorno;

Why the two zero length, zero area segments between the front and rear chamber? I have never used HR to model OB before.
Hi,

Best way to model a H-Frame (OB) is in HR to invoke the CH(compound Horn flag) when in the main HR screen.

Result: The zero areas/segments are no longer valid. Here zero length and zero area means = labels not in use.

b
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File Type: gif H-Frame-modelled-as -a- Compound-Horn.GIF (63.6 KB, 100 views)
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Old 2nd July 2011, 11:44 PM   #8
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by 60ndown View Post
looking at your graph i see 100 w max?
No but if Eg = The input voltage is set to 28.28 V (Rms) into 8 Ohms, the applied power to the driver load is U^2/R = 28.28^2/8 = 100W.

See the picture where the SPL and cone excursion corresponds to 100W input.

b
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File Type: gif 4xGRS-12PF-8_H-Frame-at 100W.GIF (47.0 KB, 100 views)

Last edited by bjorno; 2nd July 2011 at 11:57 PM.
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Old 3rd July 2011, 12:00 AM   #9
60ndown is offline 60ndown  United States
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ok about 40 watts @ 41hz,

not 100.

optimism got the better of me again :/
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Old 3rd July 2011, 07:16 AM   #10
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Why not accept there's not going to be any low bass coming out of it, and add a high pass at ~80Hz instead?

It'd take 100w easily, and would give a lot of "tone" - harmonics instead of fundamentals.
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