Bravox woofer new project - diyAudio
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Old 4th March 2008, 07:21 PM   #1
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Default Bravox woofer new project

Hello all been a little bit since my last post.

I am working on a pair of two-ways using a 8 inch Poly cone stamped Bravox woofer and a Vifa D27TG-35.

I have full specs and measurements on the Vifa but all I have on the Bravox is this.


Bravox poly cone, 8", 8 ohms.

Sensitivity is 90 db,


The graph shows, this speaker is useable up to 3khz, where it falls off .


FS: 43.5

VAS .9914 cft / 28.086 L

Re 7.4 ohms

Qts 4597

Qes .5986

Qms 1.9799

Rm 31.9515

Le .8976 mhy

Bl 9.65

mm. 27.515 g






Anybody have any info(Like real world measurements hehe.) on the Bravox stamped frame poly cone woofer.I say real world because this chart came from an ebay seller eheh not too sure about that now.

Also I have heard a good crossover frequency for the Vifa is 2-2.5k ?I am planning on 2nd order Xover.
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Old 5th March 2008, 12:07 AM   #2
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Heres a pic of the bravox
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Old 5th March 2008, 12:09 AM   #3
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And another.
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Old 5th March 2008, 07:36 PM   #4
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I decided last night to try a 2.2khz Linkiwitz-Reily in the raw to get an idea how these Bravoxs do sound.(I am an impatient little bugger.)

I say raw because I have no solid measurements of the Bravox and I havent even countersunk the drivers yet.

Image below shows my basic Xover nothing special air inductors and mylar caps.

Well I do know why I missed the midrange of a larger driver.I had been listening to a pair of Vifa 5" MTMs I had done several years ago.And while they may image great they lacked presence with vocals.

Something an 8" driver seems to find hard to do.These Bravox do sound good no muddiness(I have heard many a muddy cheap 8)
and I can't detect any resonances or spikes that would say something bad about these.

I did hear the standing waves in the cabinets though I had not put anything in the boxes so they are empty lol.


I think I am going to stick with the 2.2khz over and finish the rest first.

Anybody can recommend a good method for countersinking in plywood routerless?
Hammer and chisel?

How about internal dampening materials recommendations?(I feel a bit out of touch it's been a few years since my last serious project.

I do have a sub in the works dual sealed 15" for low end but thats for another post.


I will post pics shortly as I need to get a new CF reader.
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Old 6th March 2008, 12:43 AM   #5
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Well there is one bone I'd like to pick with Vifa on this d27tg-35.

Cheap terminals I turned up the volume and heard crackling and pulled out the left tweeter to find the terminal had cracked off on the negative side nice.

The connector seems too thin and wispy for a quality product.They do sound good though oh well.
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Old 6th March 2008, 12:54 AM   #6
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Your's seems to be a nice project.
I just finished a xover for a Vifa. Also with an 8".

Quote:
Originally posted by bickeler
I decided last night to try a 2.2khz Linkiwitz-Reily in the raw to get an idea how these Bravoxs do sound.(I am an impatient little bugger.)
Me to (Linkwitz-Riley) on that post, for the woofer at least.

http://www.diyaudio.com/forums/showt...00#post1446700

Quote:
Originally posted by bickeler

How about internal dampening materials recommendations?(I feel a bit out of touch it's been a few years since my last serious project.

I also have a project waiting on my (mothers) dinning table for two years to grow to a final stage.

Some people say that this tweeter can be very harsh, if the x-over is not well adapted to it I think.
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Old 6th March 2008, 02:28 AM   #7
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I can't say it sounds harsh just the opposite smooth and well silky lol.

But i'm one of these people who have always preferred silk over metal domes.

I think that largely comes from listening to some bad speakers with metal domes though.

I did build a pair of 2-ways years ago from the MCM closeout bin with the 8" inverted woofer and thrifty titanium dome tweeter and that was tasty.
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Old 6th March 2008, 11:14 AM   #8
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I guess it works better with an RC damper on the woofer that your's is missing.
I think your cap on the woofer is to small. Your tweeter is missing "treble", to low. Your inductor on the tweeter should be of less value.

What size is your baffle? for cheking on other parameters, etc.

It should give 87dB trough wall the "frequency spectrum" after twicks. At least were the xover freqs. cross. And I'm pointing at 2k5.

Attenuation is missing on the tweeter (+/-) 6dB's.
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Old 6th March 2008, 01:31 PM   #9
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Woofer compensation RC damper circuits ,are needed if voice coil inductance is more than crossover inductance yes?Do you think it need s one?



The Baffle is 12x17 inches.


Why do you think the cap is too large that's what tallies at 2.2khz for a Linkwitz-Reily 2nd order at least on paper?
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Old 6th March 2008, 10:17 PM   #10
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Quote:
Originally posted by bickeler
Woofer compensation RC damper circuits ,are needed if voice coil inductance is more than crossover inductance yes?Do you think it needs one?
That's a rule of thumb. Yes.
It is needed for correction of the woofer's upper frequency impedance rise because is unacceptably high at almost 7dB.
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