pierrer
Well-known member
Hi,
My Tannoy Precision 8D dont work anymore so I opened them to check what went wrong.
I need to replace both crossover networks, plus one of the amplifiers - those parts are not available from Tannoy anymore.
They say that their design is based on two boards: "filter" board and "amplifier" board. I found both of those cards inside the speaker, plus an "extra" card mentioned nowhere in the documentation.
I did a spectrum analysis of both outputs of the "filter" board and I traced the "extra" card schematic, screenshots are below.
I'm finding it hard to understand what crossover design I need - I don't know much about speakers, and the more research and tests I do the more puzzled I am - so if anyone here was able to help it would be much appreciated...
So far, I believe that the "filter" board is active crossovers because of the energy added to the signal as you can see on spectrum screenshots:
- dark blue is the noise fed into the board,
- light blue is the output fed to the amp of the bass driver,
- light green is the output fed to the amp of the tweeter (still full band at that stage).
This tweeter signal is fed, after amplification, into the "extra" board (passive crossovers) to split it between the Tweeter and the Super Tweeter - which reproduces frequencies above 21 kHz according to documentation.
1) I don't understand if the frequency dip around 4 kHz on tweeters signal is intentional ?
2) I dont understand the values of the components on the schematic, I copied exactly what was written on them: can you help me decipher at all ?
3) usekgb said that L1 and R1 form a Zobel network, but after a bit of reading it is too complicated for my grasp - can anyone explain their function in layman's terms ?
4) There is only C1 in the tweeter signal path, which I understand to be a 1st order HighPass, hence -6 db/octave. But the crossover of the bass signal shows a much steeper filtering (about -32 db/octave or so if i'm not mistaken). Wouldn't it result in a funny overall frequency response of the speaker around cutoff ? Tannoy states that the crossover frequency is 2.2 kHz.
5) The monitors are built with Tannoy's "dual concentric" technology: the tweeter is located in the middle of the bass driver. Should the Lo-Freq and the Hi-Freq signals (post crossovers) be perfectly phase matched ? What about the Super Tweeter - which is not aligned with the other two drivers ?
6) I also see that frequencies are cut at -10 dB/octave under about 40 Hz on the bass signal. Would this be intentional on Tannoy's part? should I do it ?
Any input welcome, and thanks in advance to anyone who will look into it!
Note to moderators:
I already posted about that issue on this forum, but I think my message was too long and I received almost no answers. So I syntethysed it to make it more accessible, feel free to delete the previous thread if i am in breach with forum rules. Here is a link to it:
http://groupdiy.com/index.php?topic=57216.0
My Tannoy Precision 8D dont work anymore so I opened them to check what went wrong.
I need to replace both crossover networks, plus one of the amplifiers - those parts are not available from Tannoy anymore.
They say that their design is based on two boards: "filter" board and "amplifier" board. I found both of those cards inside the speaker, plus an "extra" card mentioned nowhere in the documentation.
I did a spectrum analysis of both outputs of the "filter" board and I traced the "extra" card schematic, screenshots are below.
I'm finding it hard to understand what crossover design I need - I don't know much about speakers, and the more research and tests I do the more puzzled I am - so if anyone here was able to help it would be much appreciated...
So far, I believe that the "filter" board is active crossovers because of the energy added to the signal as you can see on spectrum screenshots:
- dark blue is the noise fed into the board,
- light blue is the output fed to the amp of the bass driver,
- light green is the output fed to the amp of the tweeter (still full band at that stage).
This tweeter signal is fed, after amplification, into the "extra" board (passive crossovers) to split it between the Tweeter and the Super Tweeter - which reproduces frequencies above 21 kHz according to documentation.
1) I don't understand if the frequency dip around 4 kHz on tweeters signal is intentional ?
2) I dont understand the values of the components on the schematic, I copied exactly what was written on them: can you help me decipher at all ?
3) usekgb said that L1 and R1 form a Zobel network, but after a bit of reading it is too complicated for my grasp - can anyone explain their function in layman's terms ?
4) There is only C1 in the tweeter signal path, which I understand to be a 1st order HighPass, hence -6 db/octave. But the crossover of the bass signal shows a much steeper filtering (about -32 db/octave or so if i'm not mistaken). Wouldn't it result in a funny overall frequency response of the speaker around cutoff ? Tannoy states that the crossover frequency is 2.2 kHz.
5) The monitors are built with Tannoy's "dual concentric" technology: the tweeter is located in the middle of the bass driver. Should the Lo-Freq and the Hi-Freq signals (post crossovers) be perfectly phase matched ? What about the Super Tweeter - which is not aligned with the other two drivers ?
6) I also see that frequencies are cut at -10 dB/octave under about 40 Hz on the bass signal. Would this be intentional on Tannoy's part? should I do it ?
Any input welcome, and thanks in advance to anyone who will look into it!
Note to moderators:
I already posted about that issue on this forum, but I think my message was too long and I received almost no answers. So I syntethysed it to make it more accessible, feel free to delete the previous thread if i am in breach with forum rules. Here is a link to it:
http://groupdiy.com/index.php?topic=57216.0
