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Multi-Way Conventional loudspeakers with crossovers

need help designing a 3-way crossover
need help designing a 3-way crossover
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Old 25th February 2018, 01:22 PM   #21
gfiandy is offline gfiandy  United Kingdom
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Yes, at the moment the best I can achieve in terms of impedance is just over 3 Ohms. That mid range is very misleading to be called a 8 Ohm driver. I even double checked my data to check I hadn't accidentally downloaded the wrong files. I might be able to improve it slightly but not by much. The only way I can raise it much higher is to reduce the sensitivity of the whole design and resistively pad the mid slightly.


If you need 8 ohms for your amp it might be better to look for a different mid.


See attached impedance plot
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File Type: png Impedance.PNG (75.9 KB, 50 views)
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Old 25th February 2018, 01:36 PM   #22
Jarryd is offline Jarryd
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My amplifier handles 4 ohms, I already have the drivers as it is part of my setup. I used an online calculator to design the first crossover which i'm currently using, could you suggest an alternative mid range? or can i continue using it?
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Old 25th February 2018, 01:42 PM   #23
Lojzek is offline Lojzek  Croatia
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Midrange proved to cause impedance drops so this is as benign as I could do at the moment. Why is this 4 ohm unit designated as 8 ohm, who knows. FWIW, here is the design.
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File Type: png Jarryd's 3 way.png (80.4 KB, 52 views)
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Old 25th February 2018, 01:45 PM   #24
gfiandy is offline gfiandy  United Kingdom
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I had another quick look at the mid and I can improve the impedance to 4 Ohms by introducing an extra capacitor to the high pass part of the mid crossover. This has not sacrificed any sensitivity it has just reduced power lost in the crossover. keep in mind if you want high quality capacitors here they will be expensive you are often looking at $$$ for high value polypropylene. Eg. a 160uF polypropylene is $64 at Parts Express. The other option is to go for non polar electrolytic which would be much much cheaper but there might be some loss of fidelity at higher frequencies.


If 4 Ohm is high enough for your amplifier it should be OK to proceed, however there still might be a compromise over sensitivity as its likely that even with baffle loss the bass might need to be padded slightly to match the mid.


Are you happy to proceed on this basis?


I haven't included the baffle simulation yet so it will all need re-optimising once I have, that will take a while so if you don't want to proceed or you want to change mid now is the time to say.


Regards,
Andy
Attached Images
File Type: png Impedance mid extra cap.PNG (76.0 KB, 53 views)
File Type: png xover extra cap.PNG (8.2 KB, 46 views)
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Old 25th February 2018, 01:53 PM   #25
Jarryd is offline Jarryd
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Quote:
Originally Posted by Lojzek View Post
Midrange proved to cause impedance drops so this is as benign as I could do at the moment. Why is this 4 ohm unit designated as 8 ohm, who knows. FWIW, here is the design.
Is baffle step loss included here as well?
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Old 25th February 2018, 01:56 PM   #26
Jarryd is offline Jarryd
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Quote:
Originally Posted by gfiandy View Post
I had another quick look at the mid and I can improve the impedance to 4 Ohms by introducing an extra capacitor to the high pass part of the mid crossover. This has not sacrificed any sensitivity it has just reduced power lost in the crossover. keep in mind if you want high quality capacitors here they will be expensive you are often looking at $$$ for high value polypropylene. Eg. a 160uF polypropylene is $64 at Parts Express. The other option is to go for non polar electrolytic which would be much much cheaper but there might be some loss of fidelity at higher frequencies.


If 4 Ohm is high enough for your amplifier it should be OK to proceed, however there still might be a compromise over sensitivity as its likely that even with baffle loss the bass might need to be padded slightly to match the mid.


Are you happy to proceed on this basis?


I haven't included the baffle simulation yet so it will all need re-optimising once I have, that will take a while so if you don't want to proceed or you want to change mid now is the time to say.


Regards,
Andy
I dont want to change my midrange, can you please proceed with the design with out padding the woofer?
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Old 25th February 2018, 01:59 PM   #27
gfiandy is offline gfiandy  United Kingdom
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Sorry just read your message. If you already have the drivers I would suggest we move forward and you use electrolytic for the large mid range values. If you find there is any loss of fidelity you can always bypass with a small polypropylene.


I see Lojzek (I agree with him about impedance, this mid should definitely be called 6 ohm if not a 4 ohm as it is just under 6 for most of the operating region) has come up with a much higher sensitivity solution as well. I was struggling to smooth out the mid without some resistance. I will re-review.


Andy
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Old 25th February 2018, 02:53 PM   #28
Lojzek is offline Lojzek  Croatia
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Yes, the baffle step loss was included. I'd be temped to open up this midrange dome for it appears as if the chamber wasn't stuffed good enough, or perhaps I'm imagining. The calculation of a standing wave in reference to overall depth of 7.8 cm would show a resonance just above 2 kHz.
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Old 25th February 2018, 03:41 PM   #29
Jarryd is offline Jarryd
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Quote:
Originally Posted by Lojzek View Post
Yes, the baffle step loss was included. I'd be temped to open up this midrange dome for it appears as if the chamber wasn't stuffed good enough, or perhaps I'm imagining. The calculation of a standing wave in reference to overall depth of 7.8 cm would show a resonance just above 2 kHz.
How do i open up it up?
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Old 25th February 2018, 04:08 PM   #30
gfiandy is offline gfiandy  United Kingdom
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I am interested to know if you can fix that peak at 2KHz following Lojzek's advice.


Anyway here is my effort at a design, good to see the bass is almost identical to Lojzek's. Hopefully this means the baffle simulation I used is valid.


To avoid less than 4R over all impedance I used a bit of resistance in the mid range. This gives an approximate sensitivity of 88dB and I make the deviations on SPL +/- 1.5dB. The F3 point is around 35Hz.


I have done two versions one which is +/- 1.5 across the whole range (This includes a 1R pad on the bass drivers) and one with no pad but the resistance loss of a cheapish inductor.


I have included close ups of the SPL and the impedance. To get the impedance to remain above 4R I had to compromise the phase a little its not completely in phase through the crossover. However the phase responses do track quite well through the crossover region so you should not get too much variation as you go off axis.


If you struggle to find any of the values let me know and I will see what the sensitivity is to the component. For instance I noticed after I had saved every thing that the 6.2mH inductor is not easy to get. I checked a 6.5mH I found at Parts Express with a slightly low resistance and it was fine the variation was small.
Attached Images
File Type: png xover 1R bass pad.PNG (250.5 KB, 35 views)
File Type: png SPL close up 1R.PNG (104.1 KB, 17 views)
File Type: png xover no bass pad.PNG (254.9 KB, 15 views)
File Type: png SPL close up no pad.PNG (104.6 KB, 14 views)
File Type: png Impedance no 1R.PNG (115.9 KB, 13 views)
File Type: png xover close up.PNG (7.9 KB, 11 views)
File Type: png Bass merge.PNG (88.5 KB, 11 views)
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