My ''TB3'' mini bipole plans

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diyAudio Chief Moderator
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Guessing...

My 4'' (pure cone area, 5 inch driver) bipole plan ended as the 'CB5'. And its here in this forum for you to see:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=58299

You have a great, and not overpriced, quad of drivers to make a very good speaker.

But I would advise towards a notch, because I am roughly guessing a hump between 500 Hz and 3 kHz when in bipole.

Like this one I sketched over a single driver of yours FR plot:
 

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diyAudio Chief Moderator
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great enclosure

That enclosure mentioned in the above link is a great plan to build. I would build it if I had those RS (Fostex drivers).

In case you feel like trying a notch, and you dont have a calibratd measuring kit (which is to just put you fast in the ball park anyway, nothing like a final judge), you should equip yourself with 0,1 0,15 0,2 0,25 mH coils, 10uf, 15 uf, 5,6uf caps and 2,7, 3,3 and 4,7 Ohm 10W resistors. Start making combinations. Be patient, listen when calm, and take notes. In a week's time and after a dozen trials since the drivers are slack you would probably end up with a better than raw feed sounding notched bipole.

I cant recommend a simpler method. Effective though.
 
frugal-phile™
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Re: great enclosure

salas said:
That enclosure mentioned in the above link is a great plan to build. I would build it if I had those RS (Fostex drivers).

I was probably one of those reviewers... these are tiny, and in Tim's implementation with Pine board seem almost weightless. Quite excellent results.

Here are some clearer plans...

I still have some of those drivers.

dave
 

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diyAudio Chief Moderator
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Angle?

Did you ever try some angle towards the listener? Maybe 10 degrees upwards. The drivers seem to be situated at a rather lowish off floor plane. I dont know about this design's dispersion, maybe its better off centre vertically and needs no angle.
 
diyAudio Chief Moderator
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TB3 Revisited

I always felt bad about losing sensitivity when fighting TB3's natural presence dip with a notch filter (read higher in the thread).
I decided to experiment with a super tweeter. I also wanted to be innovative so to avoid the typical non seamless feeling that super tweeters impart to full range speakers. I chose Audax TW010F1 that keeps well with the very low cost concept of TB3 and it can be found on http://www.madisound.com/cgi-bin/index.cgi?cart_id=8077904.3234&pid=122 on nice price.
I checked many positions over a front to back arc and I concluded that when used on top, at a specific position, it blends very well, boosting the presence range without messing coherency.
Just a cap as a tweeter filter proved inadequate distortionwise because of the Audax's high Fs. I ended up with the filter shown below.
Nothing exists between the bipole Tangband 871s and the amp now. Bingo! More sensitive, more dynamic, more open, more power intake, a brand new TB3!
The super tweeter can be easily fitted to any original TB3. It can be tested by being just attached on top with some Blu Tac. Its centre must be 6.5cm from the front top edge & 8cm to the left and right edges. You can play with R in the super tweeter filter if you feel increasing or decreasing its contribution. In my filter the parallel resistors total 0.77R and it sounds right in my room with my equipment. The TB3 revisited works best when you can see its top from the listening position at a low angle.
 

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salas, nice work!

I plan to build your revisited TB3 too, and i have some questions:

Do you fill the inside off the cabinet with any (damping) materia or anything like that?
Do you make a seperate little enclosure for the tweeter?

Can the both resistors in your schematic replaced by one resistor (+/- 0,77 Ohm)? Wat power rate must the resistor(s) have, and must it be low induction types?

Is polyprpolene good for the cap?

What is the resulting impedance of 1 cabinet?
 
Audax tweeter

A Dutch dealer told me that Audax is not online anymore for at least 3 years, and that makes it not easy to get them.

He had a few ones in stock of the TW010F1, and het ask $62 for 1 of these !!!!!

Is there a good (or better) alternative for this tweeter. A bit more expensive is not a major problem.
 
Re: conditions

planet10 said:
Neat little design... that is quite a low bass response for the 871! How did you measure it?

The FR plot is with the filter i assume. Do you have one without for comparison?

dave

Those little 3" drivers really go that low. It's necessary to have more Xmax to get some punch out of it and avoid trembling music when there are lots of low frequency content in the music. For low listening levels, it's great though.

salas said:
Speaker was facing 5m to front wall, open balcony to the world at the back, side walls were at 1,5m and 2,5m.
Mic @ 1.5m. MLS window 180ms. Checked the bass extention with 3 calibrated mics.
Yes it can be heard also. No big pressure but the 50hz region can be followed quite easily by ear when playing music. It did not detract much from same closed box power handling.

What smoothing on the data did you use?
 
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sorry for late replies

Guys, sorry for I missed following the thread.
Here are the answers:

Wim - I used felt pads inside, no separate box for the tweeter, 5W low induction is cool, yes one resistor is ok, you will determine its final value for your system and space, try from .33 up to 1 Ohm. Any 90 dB 8 Ohm 3/4 '' Tweeter will do. See image for IMP mag.

Soonqc - 1/3 oct smoothing. Are you connected with TB?

Regards

Salas
 
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