Hi
I am just completeing my MT-TL monopoles (finally).
I am going to line them with felt as per thread instructions.
I am not quite sure about the stuffing though. I have two packs of Monacor MDM2 300g/m2, but I am not sure how much to put in the cabinets. Each pack contains two 630mmx330mmx35mm sheets.
Also, I have read that only two thirds (2/3) of the transmission line should be filled. Is this 2/3 of the whole cabinet (A), or the whole of the top half and 2/3 of the bottom (B).
Please see photo for clarification. The photo shows a cross section of the cabinet. My port is built into the base.
I am just completeing my MT-TL monopoles (finally).
I am going to line them with felt as per thread instructions.
I am not quite sure about the stuffing though. I have two packs of Monacor MDM2 300g/m2, but I am not sure how much to put in the cabinets. Each pack contains two 630mmx330mmx35mm sheets.
Also, I have read that only two thirds (2/3) of the transmission line should be filled. Is this 2/3 of the whole cabinet (A), or the whole of the top half and 2/3 of the bottom (B).
Please see photo for clarification. The photo shows a cross section of the cabinet. My port is built into the base.
Attachments
The OW1 has a SPL of only 87dB so shouldn't be able to shout compared to the P13 even without any padding.
Have a look at that wiring once more as they can sound shouty at the top if the tweeter and woofer are wired in the wrong place. A pic may help (send me a PM if you do not want to post it here).
Just in case the 87dB isn't right, you can try to pad the tweeter further by changing resistors as follows until it sounds right. Change R1 to 1R5, 2R2, 3R3, 4R7, 5R6.
If it still sounds hot or wrong, then try a parallel crossover using the same values as follows.
To the tweeter:
On +ve leg, 1R to 7.5uF to tweeter -ve terminal .....yes -ve
To the woofer:
on the +ve leg, 0.47mH to woofer +ve terminal
I have a lot of experience with the P13 so know it's SPL is around 88dB but none with the OW1 and only going by manufacturer's data.
Have a look at that wiring once more as they can sound shouty at the top if the tweeter and woofer are wired in the wrong place. A pic may help (send me a PM if you do not want to post it here).
Just in case the 87dB isn't right, you can try to pad the tweeter further by changing resistors as follows until it sounds right. Change R1 to 1R5, 2R2, 3R3, 4R7, 5R6.
If it still sounds hot or wrong, then try a parallel crossover using the same values as follows.
To the tweeter:
On +ve leg, 1R to 7.5uF to tweeter -ve terminal .....yes -ve
To the woofer:
on the +ve leg, 0.47mH to woofer +ve terminal
I have a lot of experience with the P13 so know it's SPL is around 88dB but none with the OW1 and only going by manufacturer's data.
I took the drivers and crossover out of the box, hooked them up to the power amp and took measurements at various frequencies.
Attached is a file of the results.
Rabbitz, what does this mean regarding the crossover frequency? Since the voltage level for both tweeter and woofer occurs at about 4410 hz, does that mean this is the resonant frequency of the crossover?
Attached is a file of the results.
Rabbitz, what does this mean regarding the crossover frequency? Since the voltage level for both tweeter and woofer occurs at about 4410 hz, does that mean this is the resonant frequency of the crossover?
Those readings would indicate a crossover point around the 4410Hz. It would not be exact as the voltage is only part of the story and in theory the impedance at all frequencies for both drivers are the same, which it is not. It does however give you a guide to the filter operation.
The modelled crossover point is between 3800-4300Hz so the figures you have shown are not too far off that.
You can relate those voltages into approximate dB by using dB=20Log(volt out/volt in).... remember the impedance varies so will not be accurate but will give you an idea on what's happening.
Frequency; Tweeter dB; Woofer dB: (dB rounded off)
1280Hz; -11dB; -1dB (chosen as it's just above the tweeter Fs)
3000Hz; -5dB; -1dB (getting close to the xo point)
4410Hz; -2dB, -2dB (I used 1.2V input at a guess)
10240Hz; 0dB, -10dB (about 2.5x XO point)
At a stab, about -12dB for the tweeter at Fs which may be a tad high for the OW1.
It looks like the function of the filter in working properly as the voltage to the tweeter is lower below the xo point and higher above the xo point and the the variations are quite linear. You can picture the roll off from those dB values so the woofer rolls off after the XO point and the tweeter rolls up to the XO point and then is quite linear.
I still have no answer why it's sounding harsh. Sometimes the mid-woofer can have too much upper info but I've had no problem with the P13 at those xo points. Other times a zobel on the woofer can help but would throw this filter out of whack and shelf the tweeter in a horrible fashion so it would be about 3dB down at Fs.
I use a D27TG-35-06 tweeter and have no problem and sounds great. Others have reported similar results. I'm afraid I do not know enough about the OW1 and someone who is familar might butt in with some ideas.
Is there any damping in the box at the back, bottom and top?
The modelled crossover point is between 3800-4300Hz so the figures you have shown are not too far off that.
You can relate those voltages into approximate dB by using dB=20Log(volt out/volt in).... remember the impedance varies so will not be accurate but will give you an idea on what's happening.
Frequency; Tweeter dB; Woofer dB: (dB rounded off)
1280Hz; -11dB; -1dB (chosen as it's just above the tweeter Fs)
3000Hz; -5dB; -1dB (getting close to the xo point)
4410Hz; -2dB, -2dB (I used 1.2V input at a guess)
10240Hz; 0dB, -10dB (about 2.5x XO point)
At a stab, about -12dB for the tweeter at Fs which may be a tad high for the OW1.
It looks like the function of the filter in working properly as the voltage to the tweeter is lower below the xo point and higher above the xo point and the the variations are quite linear. You can picture the roll off from those dB values so the woofer rolls off after the XO point and the tweeter rolls up to the XO point and then is quite linear.
I still have no answer why it's sounding harsh. Sometimes the mid-woofer can have too much upper info but I've had no problem with the P13 at those xo points. Other times a zobel on the woofer can help but would throw this filter out of whack and shelf the tweeter in a horrible fashion so it would be about 3dB down at Fs.
I use a D27TG-35-06 tweeter and have no problem and sounds great. Others have reported similar results. I'm afraid I do not know enough about the OW1 and someone who is familar might butt in with some ideas.
Is there any damping in the box at the back, bottom and top?
Rabbitz,
I have not mentioned this before but my tests of the Vifas show differences in the TS parameters that what the factory indicates. I believe it will make a big difference in the size of the boxes.
I'm going to attach the results of two of the tests. The second of the two will follow.
I have not mentioned this before but my tests of the Vifas show differences in the TS parameters that what the factory indicates. I believe it will make a big difference in the size of the boxes.
I'm going to attach the results of two of the tests. The second of the two will follow.
The box I use is the larger design and has a very small kick between 70-80Hz plus has a fuller sound than the 5.2 litre version. Vb=9.5 litres, Fb=66Hz, F3=60hz, 47x76 port.
I use a standard series xo 3.3uF, 0.68mH, 5R6, +ve polarity to tweeter.
The pic is mine and is used nearfield.
Usually measurements vary from the manufacturer's data but the following are normally constant and therefore give similar outcomes.
Fs/Qts
VasFs²
These days I have given up on measurements and do building and testing only.
I use a standard series xo 3.3uF, 0.68mH, 5R6, +ve polarity to tweeter.
The pic is mine and is used nearfield.
Usually measurements vary from the manufacturer's data but the following are normally constant and therefore give similar outcomes.
Fs/Qts
VasFs²
These days I have given up on measurements and do building and testing only.
Attachments
Parallel xo
I decided to start experimenting with parallel crossovers with this speaker. My first try is with a 1st order Butterworth @ 3800hz using a 6.2uf cap and three inductors (didn't have one big enough) that added up to 0.62mH.
It was a huge improvement right off but the tweeter was still a little hot so I put a 2.5 (or so) ohm resister in series with it. That tamed it a little too much but it was heaps better (to my ears anyway).
I decided to start experimenting with parallel crossovers with this speaker. My first try is with a 1st order Butterworth @ 3800hz using a 6.2uf cap and three inductors (didn't have one big enough) that added up to 0.62mH.
It was a huge improvement right off but the tweeter was still a little hot so I put a 2.5 (or so) ohm resister in series with it. That tamed it a little too much but it was heaps better (to my ears anyway).