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Open Baffle Epiphany!

So, here's the first installment of my build. The baffles are 24" wide x 42" tall, 3/4" thick MDF. I tried to be cool dude and flush mount the woofers, but didn't get the recessed area deep enough. Not a problem to me, as I'd rather have too much material rather than not enough. The FR driver will be back mounted, so the next step is to round over their respective cutouts. Then, I'll add backside bracing, and paint them black. Maybe they'll get covered with cloth at some point...don't know. I just want to get them going.

They'll be powered by a 6-channel TPA3116 amp, actively crossed-over in 2.5 way configuration.



 
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rogerfederer said:
Looking good jhoyt!

This is a poultrygeist thread convergence: an open baffle run with a tp3116
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The $15 3116 ( think TBI Millenia ) would be an excellent choice to power OB's. I plan to try that combination if I can pry the 3116 from the grasp of the Frugal Horns.
 
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I'm excited because each driver will have its own amp. Plus, I can tweak the low end crossover and roll off points to get the most out of less-than-optimal-but-free woofers.
 
jhoyt said:
I'm excited because each driver will have its own amp. Plus, I can tweak the low end crossover and roll off points to get the most out of less-than-optimal-but-free woofers.
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Please come over and help me. You can have my first born. I'll also bake cookies.

cubdog
 
Bless me father, i have been listening to speakers without the boxes... LOL

So i was skeptical of this whole idea... but i finally decided to give it a go. The second thrift store had an old magnavox with a perforated back; i hollered the obligatory "Scroe!" and headed for the checkout.

The paperwork was dated 1970. I pulled the 12" paper cones and horn tweeters and crossovers, and popped them into a large cardboard box that i had halved, and fired it up....

After 30 seconds, the thought that ran through my mind was " Wow, thats the sound i've been looking for for years" The sound is three dimensional.
All i can say is "you got to try this!" It isnt like tennis balls under your turntable or cloths pins holding your speaker wire off the floor; where you have to listen close to hear the difference. This is a leap !

But did i mentioned that i was skeptical? for the last 18 days i have been arguing with myself on whether these are great or not... i swapped the horns for some paper tweeters and even better... The conclusion? The old box speakers just sound....flat. They are headed for storage...

Dont pass up an old console...

I havent had this much fun with stereo since high school...:thmbsp: I need a real baffle, then woofers, then a chip amp, then....
 
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Round-overs are in place. They look pretty good, but there's a little sanding to do.



 
Poultrygeist said:
The $15 3116 ( think TBI Millenia ) would be an excellent choice to power OB's. I plan to try that combination if I can pry the 3116 from the grasp of the Frugal Horns.
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I would caution tempering this statement, as far as implying the 3116 being the equivilent of the TBI Millenia.

I think it is fair to say they use the same output chip, if that can be verified. But have you gone through the process of checking to see that the input circuit is the same, and that the same Motorola op amp is used in this circuit. Also are the power supply portions of the internal board the same? Is the filter after the digital output chips of the same design and quality?

I think there are a lot of questions to be answered before anyone makes the assumption that the 3116 is the equivalent of the Millenia. There are many amplifiers that use the same output devices, whether they be MOSFET or bi-polar transistors, or CD players that use the same DAC chips....and yet these machines do not sound the same or perform at the same level. There is far more to a component than sharing a couple of parts and then making the implication they are of the same quality level. I understand that you may not be doing this, but it certainly is easy to read this perspective into the post by someone who may not be as experienced as a seasoned hobbyist.

Of course this is just the opinion of a simple pig.......

Regards
Mister Pig
 
Mister Pig said:
I would caution tempering this statement, as far as implying the 3116 being the equivilent of the TBI Millenia.

I think it is fair to say they use the same output chip, if that can be verified. But have you gone through the process of checking to see that the input circuit is the same, and that the same Motorola op amp is used in this circuit. Also are the power supply portions of the internal board the same? Is the filter after the digital output chips of the same design and quality?

I think there are a lot of questions to be answered before anyone makes the assumption that the 3116 is the equivalent of the Millenia. There are many amplifiers that use the same output devices, whether they be MOSFET or bi-polar transistors, or CD players that use the same DAC chips....and yet these machines do not sound the same or perform at the same level. There is far more to a component than sharing a couple of parts and then making the implication they are of the same quality level. I understand that you may not be doing this, but it certainly is easy to read this perspective into the post by someone who may not be as experienced as a seasoned hobbyist.

Of course this is just the opinion of a simple pig.......

Regards
Mister Pig
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Didn't say it was the equivalent of the $500 Millennia although those who have heard both say it's closer than it has any right to be. Check out the giant threads on AC regarding these T.I. chip based amps.
 
Poultrygeist said:
Didn't say it was the equivalent of the $500 Millennia although those who have heard both say it's closer than it has any right to be. Check out the giant threads on AC regarding these T.I. chip based amps.
Click to expand...

Well I have had a couple of Millenia amps in my house for over a year, got a decent idea of what it is capable of. But I have not heard the Chinese 3116 version...but might pick one up some day.

Regards
Mister Pig
 
I have some drivers lying around and wondered whether they would be suitable for a mock-up open baffle experiment. What I want to know is whether I can use what I have without a passive crossover, and whether I would run any risk of damaging the amp if I didn't. I have a 2 way active crossover, and could probably be bi-amping and using larger enclosed woofers with a separate amp for the very low end.

Here are the specs for what I have:

Vifa P13WH-00 5" Woofer
Polypropylene cone, cast magnesium basket, rubber surround, Power Handling: 40 watts RMS/55 watts max, Voice coil diameter: 1", Impedance: 8 ohms, Frequency Response: 60-5,000 Hz, Fs: 60 Hz, SPL: 88 dB 1W/1m, Vas: .35 cu. Ft., Xmax: 4.0 mm

Vifa D25AG-35 1" Aluminum Dome Tweeter
Aluminum Dome, Ferrofluid, Phase Shield, Double Chamber, Power Handling: 100 W RMS, Voice Coil Diameter: 1", Impedance: 6 ohms, Frequency Response: 2,000-35,000 Hz, Fs: 850 Hz, SPL: 89 dB 1W/1m.

It looks like the woofers wouldn't work as a full range, so I think I'd want to use the tweeters too if possible. (I'm realizing that neither one appears to be designed for the range between 5000 and 2000 Hz, but that's what I've got.)

Can the woofers and tweeters be wired together without a passive crossover? How much risk is there of damaging the amp or the speakers by doing so?
 
johnebravo said:
I have some drivers lying around and wondered whether they would be suitable for a mock-up open baffle experiment. What I want to know is whether I can use what I have without a passive crossover, and whether I would run any risk of damaging the amp if I didn't. I have a 2 way active crossover, and could probably be bi-amping and using larger enclosed woofers with a separate amp for the very low end.

Here are the specs for what I have:

Vifa P13WH-00 5" Woofer
Polypropylene cone, cast magnesium basket, rubber surround, Power Handling: 40 watts RMS/55 watts max, Voice coil diameter: 1", Impedance: 8 ohms, Frequency Response: 60-5,000 Hz, Fs: 60 Hz, SPL: 88 dB 1W/1m, Vas: .35 cu. Ft., Xmax: 4.0 mm

Vifa D25AG-35 1" Aluminum Dome Tweeter
Aluminum Dome, Ferrofluid, Phase Shield, Double Chamber, Power Handling: 100 W RMS, Voice Coil Diameter: 1", Impedance: 6 ohms, Frequency Response: 2,000-35,000 Hz, Fs: 850 Hz, SPL: 89 dB 1W/1m.

It looks like the woofers wouldn't work as a full range, so I think I'd want to use the tweeters too if possible. (I'm realizing that neither one appears to be designed for the range between 5000 and 2000 Hz, but that's what I've got.)

Can the woofers and tweeters be wired together without a passive crossover? How much risk is there of damaging the amp or the speakers by doing so?
Click to expand...


I would use a crossover. You can design something very simple online and put it together with $15 in parts.
 
Right. You won't damage amps or the mid/woofer, but you WILL damage the tweeter running it full-range. Even a simple capacitor in series will prevent damage, and keep the tweeter "tweeting". Since you have an active crossover, I would play around with that, between woofer and tweeter. For the subwoofer, you could use a plate amp with a built-in low-pass crossover. That would really optimize the setup, and you would get to tweak the woofer/tweeter crossover point by ear.
 
One speaker ready for testing. I'm amazed (though I shouldn't be) by the amount of flex in the baffle. It almost resonates like a spring, but in the infrasonic range. I'm going to add some strut braces running vertically up the baffle sides. This should help the flexiness, and maybe give me another 2 Hz of bass. :D And this sucker is HEAVY! The strut braces will add even more weight. At least they feel really stable standing up. The baffles are tilted back at ~7.5°, and this seems to be pretty good.



 
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jhoyt said:
One speaker ready for testing. I'm amazed (though I shouldn't be) by the amount of flex in the baffle. It almost resonates like a spring, but in the infrasonic range. I'm going to add some strut braces running vertically up the baffle sides. This should help the flexiness, and maybe give me another 2 Hz of bass. :D And this sucker is HEAVY! The strut braces will add even more weight. At least they feel really stable standing up. The baffles are tilted back at ~7.5°, and this seems to be pretty good.



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Those look awesome!! Hopefully late in the summer maybe we can have an ICT GTG and listen to them. My loft should be done and we could do it there.

Are you gonna run those with the TDA3116 amp?

- Woody
 
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