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Old 29th August 2008, 02:08 PM   #1
babagau is offline babagau  Greece
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Cool bass guitar cabinet

Hello! This is my first speaker cabinet project and ideas and advice on it are welcome! It is a 2 speaker system (in parallel, R=4Ω) for my bass guitar. The cones are a Visaton BGS 40 woofer 300W max http://www.visaton.com/en/chassis_zu...n/bgs40_8.html
and a Beyma 8MI100E mid-range 250W max.
http://profesional.beyma.com/pdf/8MI100E.pdf
I lean towards making it with bass reflex.
I'll try tune it using the formula for the Helmholtz frequency.
I intent not to use crossover.
I am aware of the dimension ratio of 1 : 1.618 : 0.618.
But
a) I guess I should tune the port a low as possible right? And surely lower than the resonance frequencies of the cones.
b) I hope my choice of cones is suitable for the application, right?
c) I don't know if I should place the tube somewhere low or in the middle.
d) Also what if I separate the two cones, one in its own cabinet with its own bass reflex, but all in one enclosure?
e) In what way shall I take into consideration the Thiele/Small parameters? Do these in litres or cubic metres indicate the suggested volume of the enclosure? They seem chaotic! Any on-line calculator suitable for this enclosure?

I thank you beforehand. diy.
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Old 29th August 2008, 06:04 PM   #2
HK26147 is offline HK26147  United States
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Quote:
(a)I guess I should tune the port a low as possible right?
Not necessarily: It involves a decision on how you want it to behave on the low end ( response curves - ie B4,QB3,C4,BB4 or a variant )
Quote:
(e) In what way shall I take into consideration the Thiele/Small parameters?
That's the basis of your decision ( with question a in mind ). It does help determine the volume of the cab.

* Looking at the speaker link, I see they recommended 50 - 100L.
( I did not run these particular T/s specs )

This software is free & gets good reviews
http://www.linearteam.dk/default.aspx?download=winisd
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Old 30th August 2008, 04:36 AM   #3
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Its normally good to tune the box optimally for the drivers, power handling and power handling in relationship to XMAX.

Perhaps you should download something like Win ISD or buy a copy of HT Bass Box Pro?
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Old 30th August 2008, 01:58 PM   #4
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the ideas you suggest in the first post may be appropriate for Hi Fi speakers, but Guitar/Bass speakers are a different ball game...

For bass, your 15" speaker seems to be a good choice, just put it in a sealed, unlined cabinet that's not too big to carry around, then decide if you need more top end and another driver later...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 31st August 2008, 02:46 PM   #5
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One of the best options we have found for bass guitar is a single wideband 15" driver like our TD15M. This extends cleanly out to 4KHz and is only about 10-12dB down at 10KHz. This single wideband driver has none of the phase issues of using 2way systems. The 15" also has better high end extension than most 8" drivers on the market. They can play the slap of strings, etc very well right on axis. Their high frequency dispersion is also more controlled making it easier to mic them and not have issues with feedback at other mics.

Click the image to open in full size.

These drivers are being used this way in some very high end bass guitar cabinets. You can see them in a slightly modified version in the DS-115B's here:

http://www.doronzosound.com/artist.htm

You're going to want to keep excursion to a minimum so this will typically mean a vented cabinet. The lowest note you need to cover is typically 32hz, so tuning right around there is usually best.

You could do similar with your drivers in a similar cabinet just as a 2way, but don't expect to get a lot of low end out of a driver with so little xmax.

John
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Old 2nd September 2008, 08:43 AM   #6
babagau is offline babagau  Greece
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There are 2 things I can't figure out about the Beyma 8MI100 speaker.
1) According to http://profesional.beyma.com/pdf/8MI100E.pdf,
it has a power capacity of 250W AES and program power (is it same as max power?) 500W.
But the thielesmall.com database lists it with 100W AES max power.
I can't understand from these, what the RMS is. Maybe this speaker after all is not suitable for bass guitar cab.
2) Also, according to the winISD graph, the group delay goes extremely high (46ms)
in a narrow peak around the tuning frequency (35hz), but the speaker below 150hz starts
its down curve and at 35hz its about 20db less than the "linear" response between 150-7000.
I don't think the speaker is audible enough at 35hz to take into consideration this 46ms delay, should I?
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Old 2nd September 2008, 11:16 AM   #7
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Quote:
Originally posted by babagau
There are 2 things I can't figure out about the Beyma 8MI100 speaker.
1) According to http://profesional.beyma.com/pdf/8MI100E.pdf,
it has a power capacity of 250W AES and program power (is it same as max power?) 500W.
But the thielesmall.com database lists it with 100W AES max power.
I can't understand from these, what the RMS is. Maybe this speaker after all is not suitable for bass guitar cab.
For the power, I would definitely trust Beyma over the t/s site as I've found other errors there too. Probably just typos.
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