El-cheapo active LOUDspeaker

Status
Not open for further replies.
Jump to Latest
#21
Last edited:
#22
Having found a few references to off-axis dips in FR (see prev. post) I'm not that worried about this aspect anymore.

I changed the LP a little tonight (oh, the joy of changing an active breadboard-filter compared to a huge passive monster). Moved the crossover a little higher as seen here:

An externally hosted image should be here but it was not working when we last tested it.


Maybe I just placed the mic in a sweet spot, but it looks good:

An externally hosted image should be here but it was not working when we last tested it.


The curve that dips, is the woofer with reversed phase.

Im pretty convinced that the woofer-ripple is an measurement artifact
 
#23
The large dip at 300Hz looks like floor bounce to me.

All in all starting to look pretty good considering the (less than) minimal outlay.

I still suspect that you might need a bigger PSU to go loud.
But that is just a suspicion as my electronic knowledge is nearly non-existent.
 
#24
Actually the PSU is (just) big enough to go (semi-loud). I've tested it close to clipping and it was OK. But your right, more current-capacity would be better.

The measurement setup is very far from ideal right now. To many surfaces close to mic and speaker.
 
#26
Implemented a notch-filter around 16-17K to remove the horn-peak. Not sure if its audible, but the dogs and bats will probably approve.

Heres a measurment at midpoint between horn and woofer. Approx 0,15,30 and 45 off axis.

Wondering if the "dip" around 500Hz is the baffel-step? Might have to read up on that a little.

sgmx44.png
 
#29
Problems related active filters are the same as for the passive. Filter except frequency of crossing should have the ability to change the Q factor of the filter.
If it does, then the active filter down to ordinary calculator.
The correct order should be set using the simulator target response, enter the recorded responses of individual speakers and then changing the order of frequency, and Q,,
factors indicate the speaker recorded in the target respons
Quite by chance may be that LR24 dB acoustic suits B 12 electrically
ili12dB with a Q factor of 1.14 or 12dB with Q 0.85.

PS it is wrong to alter only the frequency, should be changed as needed and Q factor
 
#30
The problem of acoustic phase and the simulator is that simulators care and counted acoustic phase and those that use simulators to every time and do not work 🙂
There is a possibility that the simulator Account acoustic phase which is not entered on and then do what you want 🙂

ARTA has the ability to measure with enough precision acoustic stage, but if the simulator or the one that works with the simulator does not see, and then the end result being usually wrong.
Theoretically electronic filter calculations perfect cut and it is well with electric hand ...... but enters the game and acoustic responses with their acoustic phase and then ARTA record that record ...... not recorded ARTA wrong, wrong is filter ...... and so in 99% of cases, filter 🙂
 
#33
First draft of a filter section. PCB is etched and drilled. Waiting for some free hours to populate the PCB.

General idea: the board is to placed on a "main-board the holds PSU and other misc stuff. Power-gnd and signal-gnd are isolated and joined somewhere near the PSU

Film-caps (ebay-kit. unknown qaulity) are mounted through hole. Resistors (leaded and SMD) are mounted on bottom side SMD-style. A lot easier to replace and tweak.

An externally hosted image should be here but it was not working when we last tested it.


50X50mm includes this:

An externally hosted image should be here but it was not working when we last tested it.
 
Last edited:
#34
Well, A few mistakes I found so far: BSC implemented wrong ( old sketch in final design), I forgot the 14KHz highpass that should compensate for the horn response and level-adjustment for both HP and LP would probably be a good idea.
 
#35
First prototype of the filterboard and the mother-board it plugs into.
Surprisingly most of it works although i forgot to consider the fact that the amplifier has input referenced to Vss and the other filterparts are referenced to Gnd.

Problems noted so far:
1)The EBAY amplifier has way to much hiss to be connected directly to the horn with the very high sensitivity around 2-5Khz. Solution: replace the active 14Khz highpass with a passive type (which will probably require a single Cap + impedance correction for the horn. - so much for going active...)
2)The EBAY voltage booster turned out to be unstable and this resulted in massive noise on the amplifier output. Luckily someone already found the cure to make the regulator stable: 10/30/50/100W LED application driver (UC3843A). #360customs

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


IMGDEAD]
 
#39
Hi,

I can't see how active makes this speaker cheaper or better.

Polishing a turd comes to mind, good active over a passive
is never cheap, cheap is just pointless overcomplication.

The effort is best expended on something far better.

rgds, sreten.
 
Last edited:
Status
Not open for further replies.
Top Bottom