• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Calling all XO gurus!

EmuMannen

EmuMannen

Member
I got a pair of BIC SoundSpan TPR-600 that I got from a friend (who bought them new in the 70s). I was considering an XO upgrade or to go active, so I took a look at the original XO. But I can't wrap my head around it! Please take a look at the attached image. Red wire to woofer, green to mid and white to tweeter. They all share the black as the negative pole.

IMG_1592.jpg

First of all, the markings on the coils; 109, 142 and 172? 109 can't be 10x10^9 so I'm a bit baffled. But what I find really puzzling is the fact that this 3-way XO only got one capacitor! The total amount of components and their values are; 1 capacitor 10uF, two resistors 2 and 4.7 Ohms, three coils marked 109, 142 and 172. I don't get it...

So I stuck the circuit with my assumptions into TINA-TI and ran a simulation. The circuit and the resulting graph are also attached. It sure didn't make me any wiser because it looks like the tweeter got a low-pass filter. What am I missing here? Has anyone ever seen a 3-way XO with only one cap? Or with a cap, two resistors and three coils in total?

confused.gif
TPR-600-XO_S.jpeg

TPR-600-XO_G.jpeg

Thanks in advance for any help. :)
 
Register to hide this ad
Ps. I have learnt that the tweeter is a piezo and that it would explain the lack of a cap but I still don't get the coil for the tweeter?
 
I'm no crossover guru, but I have to ask: how do these speakers sound? Can't imagine the tweeter does much in that setup.
 
From what little I know, I would assume the markings on the coils are their values in microhenrys (mH).
 
Most all coils I've seen in speaker crossovers are measured in miliHenries (mH), not micro Henries (µH). One miliHenry = 1000 microHenries. But those numbers on the coils, 109, 142 and 172, are puzzling because they seem too large if they really are mH.

I briefly spent time Googling for a crossover schematic diagram for your speakers, but found nothing. You've probably done the same. Maybe you could order a service manual, if you can find one – they usually don't cost much.

When all else fails, buy an inexpensive LC meter, such as this from Amazon. You will have to remove the crossover boards and cut the wires to the coils before you can read their inductance. This meter works for capacitors too. This way you can study the wiring on the board and figure out what that schematic diagram really is.
 
EmuMannen said:
I think I got it now. This thread and this page gave me what I needed to figure it out. And this thread is giving me what I need to move forward.

Ps. Still interested to know how to interpret the markings on the coils though.
Click to expand...
I do not know how to interpret the markings on the coils but as a comparison for you, here is a picture of one of my speakers board.

Also what did you end up doing/concluding about the piezo tweeter? I curious to know.
Thanks for interesting reads on both your threads of these speakers.IMG_4406.jpeg
 
You must log in or register to reply here.
Back
Top Bottom