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Old 18th April 2007, 06:24 AM   #1
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Default BG20 as small PA bass driver (?)

How would it perform?

It's a small 8' driver, but is it capable of delivering that PA 'punch on tha chest' ?

Anyone who has tried out this speaker, please comment.
Also everyone else's opinions are greatly appreciated

Here's the datasheets :

German, pdf http://www.stoffelshome.de/download/...bg20_8_ohm.pdf
English, web page http://www.visaton.com/en/chassis_zu...er/bg20_8.html

Rated power 40 W
Maximum power 70 W
Nominal impedance Z 8 Ohm
Mean sound pressure level 92 dB (1 W/1 m)
Maximum cone displacement 8 mm
Resonance frequency fs 38 Hz
Height of front pole-plate 4 mm
Voice coil diameter 25 mm
Net weight 1,3 kg
D.C. resistance Rdc 6,2 Ohm
Mechanical Q factor Qms 3,47
Electrical Q factor Qes 0,51
Total Q factor Qts 0,44
Equivalent volume Vas 110 l
Effective piston area Sd 214 cm²
Dynamically moved mass Mms 10 g
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Old 18th April 2007, 09:47 AM   #2
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I have 2 mid/tops with them, two drivers in a 60 L vented cabs plus a supertweeter. For a smaller event (eg house party) they're quite enough and kick like mules (the amp is 60 w/ch @4 ohms lm3875 (planning to upgrade)). I suggest to use subsonic filter set at 40...50 Hz. However, for a larger event they should only be used for midrange, crossed over at 150...200 Hz, proper bassbins below that (in the spirit of cheap, 230 L reflex cab with two Visaton W300 in a push-pull configuration show some good simulations).

Sounwise, these little fellows are very good for the price (got them for ~22€/pc), the top end may need some help, though. Also the rising response at 1 kHz or so may need equalizing. I got rid of it quite simply - using 2 drivers with ~850 Hz first order low pass (simple 1,5 mH inductor, if memory serves) on one.
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Old 18th April 2007, 10:56 AM   #3
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Quote:
Originally posted by technofreak
I have 2 mid/tops with them, two drivers in a 60 L vented cabs plus a supertweeter. For a smaller event (eg house party) they're quite enough and kick like mules (the amp is 60 w/ch @4 ohms lm3875 (planning to upgrade)). I suggest to use subsonic filter set at 40...50 Hz. However, for a larger event they should only be used for midrange, crossed over at 150...200 Hz, proper bassbins below that (in the spirit of cheap, 230 L reflex cab with two Visaton W300 in a push-pull configuration show some good simulations).

Holly s*** pal im planing virtually indentical setup! 60L vented tuned to a healthy 45 Hz. + a piezo for top end and a TDA7294 amp. Put to use in some PA monitors.

The thing that concerns me is very high compliance of these drivers.
It's not published in the specs. but from fs/Mms i calculated it to be 1.1 mm/N whereas PA speakers rarely go above 0.3.

This also confirms in practice - the cone moves fairly easy when unloaded. I don't know how that actually affects that 'hard' PA sound. If you can repp how they perform against some HiFi foam surround units i'd be very gratefull. .

You'll just have to tell me more about them
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Old 18th April 2007, 01:25 PM   #4
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Yep. a good example of convergence 60 L tuned to 45 Hz with piezo over ~10kHz it is here too.

Compared to some 3-way old hi-fi boxes they sound much smoother on the top end, midrange is just sweet and bass is nice'n'punchy. They go to about 45 Hz in room, some output down in the 30s too, but yes, they tend to run out of excursion at the very low freq-s and high power, hence the suggestion for subsonic filter (though I dont use it for home listening/small parties - go loud enough with minimal excursion for that). Sensitivity is good, about 95 dB/W, so you don't need much over 10 watts for dance music in a small (~50sq. metres or so) room.

Attached a pic of an early stage of the speakers (no supertweeter and grill).
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File Type: jpg picture 010sm.jpg (46.3 KB, 352 views)
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Old 15th October 2007, 12:28 PM   #5
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I am totally new to loudspeaker building however i have a pair of these drivers and need a single high output PA speaker for a guitar amp project. Basiclly your design sounds perfect however i have no idea how to design a 60 litre box tuned to 45hz or know how to build the crossover.

I would not need to go very low, and i think i need to tame the treble somehow since when i used these in very rough boxes and open baffle i found them very shouty. This is the main reason they have been stored for over a year.


Any advice greatfully recieved

Fil
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Old 15th October 2007, 01:18 PM   #6
sreten is online now sreten  United Kingdom
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Quote:
Originally posted by filholder
I am totally new to loudspeaker building however i have a pair of these drivers and need a single high output PA speaker for a guitar amp project. Basiclly your design sounds perfect however i have no idea how to design a 60 litre box tuned to 45hz or know how to build the crossover.

I would not need to go very low, and i think i need to tame the treble somehow since when i used these in very rough boxes and open baffle i found them very shouty. This is the main reason they have been stored for over a year.


Fil

hi,

Generally speaking a 60L box is very big for a 2 x 8" driver used
for a guitar amplifier. TBH you may be better off with 8" or 10"
guitar speakers chosen for sealed or open back use.

Venting guitar speakers is pretty much a waste of time.

/sreten.

Graphs are for 2 drivers in a box.
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Old 15th October 2007, 07:02 PM   #7
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True but this is not a typical guitar amp, it more like a mobile PA, since it also has a cd input for playing backing tracks. It will also feature a mic input when finished
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Old 16th October 2007, 04:09 PM   #8
sreten is online now sreten  United Kingdom
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http://www.visaton.com/en/bauvorschl...576/index.html

Hi, according to the above closed 23L (presumably well stuffed) is possible, /sreten.
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