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Old 30th November 2006, 01:59 PM   #1
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Question Bose 301 V crossover tweak

Hi everybody...
Someone has t&s parameters of the drivers used in this speakers???

Bose don't give any information...

And... for tweak this speaker i can also modify the crossover network... i posted the schematic of the original crossover...
note that the fuse in the schematic seems to be a lamp used as a fuse...
SUGGESTIONS FOR A MOD/TWEAK OF THE CROSSOVER???
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Old 30th November 2006, 02:40 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

you sure that schematic is correct ? hardly any output from the second tweeter.......

/sreten.
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Old 1st December 2006, 10:39 PM   #3
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yes i'm sure... i have checked... the cap in parallel cut high frequencies... the second tweeter works like a midrange directing it's output to wall...
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Old 2nd December 2006, 12:44 PM   #4
Ron E is offline Ron E  United States
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Default Re: Bose 301 V crossover tweak

Quote:
Originally posted by Flavio88
i posted the schematic of the original crossover...
Now if that crossover doesn't justify the phrase "better sound through engineering", I don't know what does.

Without measuring the drivers, a modified crossover would be pretty difficult to suggest.

As a guess, small inductor in series with the woofer might make the upper midrange cleaner, or it might just muck things up. You could replace the bulb with a series resistor and a fuse, but the point where you have a large enough fuse to avoid a nuisance tripping issue is where you will blow those little tweeters.

About 18 years ago, a friend had a pair of these on either end of a long dresser pulled out into the room a bit, with his stereo system and TV between. The room was very reflective, and I remember that they sounded very nice with U2 and the Smiths, the Cure, Morrisey, etc... Some of those recordings sound pretty harsh on my current system, so the euphonic muddying character of the direct-reflect may have been a benefit...
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Old 4th December 2006, 11:05 AM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Flavio88
yes i'm sure... i have checked... the cap in parallel cut high frequencies...
the second tweeter works like a midrange directing it's output to wall...

Hi,

1.5uF for the capacitor would make sense, but 15uf rolls it off below
the frequency the 4uF allows frequencies through - hardly any output.

/sreten.
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Old 5th December 2006, 11:52 AM   #6
Salas is offline Salas  Greece
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1,5uF it must be, Sreten is right. Check again.
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Old 6th December 2006, 01:19 AM   #7
kevinkr is offline kevinkr  United States
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The lamp actually is a little more sophisticated than just a resistor and fuse combination - at reasonable levels the resistance of the bulb is quite low, as power is increased the filament starts to heat up reducing power delivered to the tweeters - can you spell compressor?


Incandescent lamps have a positive resistive coefficient - as they heat up the resistance increases. This particular lamp was chosen very carefully to complement the power handling capability of those tweeters.

Unfortunately I no longer remember the correct values for those caps..

An escaped boso
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Old 13th December 2006, 12:03 AM   #8
Ron E is offline Ron E  United States
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Quote:
Originally posted by kevinkr
The lamp actually is a little more sophisticated than just a resistor and fuse combination [...] can you spell compressor?
The resistor and fuse was to remove the "compression" effect without changing the tonal balance.....

Incandescent lamps change their resistance approx 17X from low voltage to their rated voltage.
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Old 13th December 2006, 03:43 AM   #9
kevinkr is offline kevinkr  United States
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Yes, but do you know the correct lamp cold resistance value to set the tweeter level? You'll find very few commonly available dmm that do good low ohm measurements. I think an Lpad might be a better choice... Probably is not too critical in any event. Fuses incidentally are not too linear either, if you know you are not going to abuse the speaker I would get rid of it.

Without being too blatant about it I obviously know about the positive temperature coefficient of that specific light bulb..
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Old 13th December 2006, 02:09 PM   #10
Ron E is offline Ron E  United States
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Quote:
Originally posted by kevinkr
Yes, but do you know the correct lamp cold resistance value to set the tweeter level?

Without being too blatant about...
The temp coefficient info was for the original poster and general information, not to "educate" you. If one knows the original bulb voltage and wattage, one can derive a starting value for resistance experimentation from that information. The resistance should be relatively easy to measure - but the Lpad is not a bad idea. The jist of my mentioning the fuse and nuisance tripping was to (poorly) hint at why the bulb is there and that it might not be worth replacing. Those tweeters honestly can't handle much power unprotected.
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