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crossover question

Wharfedale Linton Heritage Speakers

jaudere

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Hello friends,

could someone explain me whether adding a second order crossover ina threeway speaker change the final driver impedance. if yes then how to calculate it?

I tried to find an answer but couldn't. I don't have engineering background so can't do it logically( I am a critical care specialist)

what i know is how to calculate impedance when speakers are connected in series or parallel but cannot do it when crossover comes into circuit. so i am stuck on basic design itself.

for e.g., if i want to use 8 ohm tweeter, 4ohm midrange and 4 ohm bass driver with second order crossover(low pass: around 250Hz , bandpass 200-6000 and highpass 4000-20000.) how to calculate final impedance of the system?
or the other way round, how do I form a crossover if I am using yamaha RX V361 , which likes 6 or 8 ohm speakers.

from the net i got values of capacitor and inductors and R Pad but then I am stuck.

friends, please help me.

Please look at the following link where someone has done a threeway speaker, all drivers are 8 ohms and he has given crossover design. Now please tell me what will be final impedance presented to the amp?


1.618 - DIY 3-Way Hi-Vi Tower Loudspeaker Project (Page 2)


thanks
 

grubyhalo

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Hello friends,

could someone explain me whether adding a second order crossover ina threeway speaker change the final driver impedance. if yes then how to calculate it?

I tried to find an answer but couldn't. I don't have engineering background so can't do it logically( I am a critical care specialist)

what i know is how to calculate impedance when speakers are connected in series or parallel but cannot do it when crossover comes into circuit. so i am stuck on basic design itself.

for e.g., if i want to use 8 ohm tweeter, 4ohm midrange and 4 ohm bass driver with second order crossover(low pass: around 250Hz , bandpass 200-6000 and highpass 4000-20000.) how to calculate final impedance of the system?
or the other way round, how do I form a crossover if I am using yamaha RX V361 , which likes 6 or 8 ohm speakers.

from the net i got values of capacitor and inductors and R Pad but then I am stuck.

friends, please help me.

Please look at the following link where someone has done a threeway speaker, all drivers are 8 ohms and he has given crossover design. Now please tell me what will be final impedance presented to the amp?


1.618 - DIY 3-Way Hi-Vi Tower Loudspeaker Project (Page 2)


thanks

Hi,
I'm not too great when it comes to numbers and electronics either, but was just curious about a few things you mentioned:

1. Have you finalised the drivers that you wish to use?

2. I did not quite understand if you had already completed your network and the L-pad and want help in finding out the impedance of the network? I guess this would be possible using a software (WinISD Pro?) or by using forumlae. Sorry I can't help you more than that...:eek:

3. Also, I was a little confused with the ranges you've given for your network. If I'm not mistaken there would be just 2 frequencies of interest. F(h), which in the project you've linked to is 4000 Hz and F(l), which is 500 Hz. As I understand, anything above 4000 Hz would be taken care by the tweeter and anything less than 500 Hz by the woofer and everything between 500 and 4000 Hz taken care by the mid-range. Is this what you're trying to do as well?

Here's a resource that helped me understand crossover design a little:

X-over FAQ's
 

Abhishek

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hi jaudere!

you can use a zobel network to design your crossover with a fixed input impedance.
you may choose your input impedance to be 4, 6 or 8 ohms and design the zobel network likewise. this way the input impedance will not depend on the impedance of the drivers used. the amplifier will always see the load as the designed impedance of the zobel network.

regards,
abhishek.
 

Asit

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Hi jaudere,

Please take an opinion also from our forum member "cranky". I think he is in the process of relocating from one city to another and as a result not looking at the forum at all (for the moment, I believe).
 

jaudere

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Hi grubyhalo,

I am not designing any crossover but trying to understand the crossover thing. you know I am trying full range speakers . but if i go for open baffle in that, i will have to use something for the low frequency. so i am reading about crossovers.

Have you finalised the drivers that you wish to use? : Almost. Full range will ve philips and LF will be locally made 10" 4 ohm ,2 drivers for each.
there is a perosn called Walwekar in pune whose drivers i like although he does not give TS parameters. so will use those.

2. I did not quite understand if you had already completed your network and the L-pad and want help in finding out the impedance of the network? I guess this would be possible using a software (WinISD Pro?) or by using forumlae. Sorry I can't help you more than that...
>>>: No i have not compelted anything.

3. Also, I was a little confused with the ranges you've given for your network. If I'm not mistaken there would be just 2 frequencies of interest. F(h), which in the project you've linked to is 4000 Hz and F(l), which is 500 Hz. As I understand, anything above 4000 Hz would be taken care by the tweeter and anything less than 500 Hz by the woofer and everything between 500 and 4000 Hz taken care by the mid-range. Is this what you're trying to do as well? :

>>In a 3 way system you will need a third filter for midrange which will be bandpass filter. which will cut frq below those for woofer and above those which will go to tweeter. 1st fiter: will cut evrything above 250, bandpass will cut anything below 250 and above 6000 and high pass will cut anything beloiw 4000. I mentioned those as i would like some overlap.

Here's a resource that helped me understand crossover design a little:
>>> Thanks a lot for this resource. immensly helpful
 

jaudere

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i am getting inclined towards Orion: open baffle for high and Mid, H frame for woofer.
ORION challenge to DIY


the modification:
1)won't use tweeter and midrange and tweeter frequencies will both be handled by fullrange driver.

2) will use induction coild as 1st order low pass filter for woofer. simplest thing to do. will cut anything above 250. using first order will automatically allow some overlap. isn't it?

Vikram
 

jaudere

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hi jaudere!

you can use a zobel network to design your crossover with a fixed input impedance.
you may choose your input impedance to be 4, 6 or 8 ohms and design the zobel network likewise. this way the input impedance will not depend on the impedance of the drivers used. the amplifier will always see the load as the designed impedance of the zobel network.

regards,
abhishek.


Thanks for the idea.i read at may places that more the components between amp and speaker, more is the colouration. want to avoid that and will like to keep things as simple as possible. besides that, the Zobel thing was getting over my head (not even tangent) as I studies electrics/electronics and physics some 12 yers bck. after that no contact with those 2 subjects. trying to learn things from scratch.

( myintension of using crossover but avoiding Zobel may look contradictory)
 

flanker.r

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i am getting inclined towards Orion: open baffle for high and Mid, H frame for woofer.
ORION challenge to DIY


the modification:
1)won't use tweeter and midrange and tweeter frequencies will both be handled by fullrange driver.

2) will use induction coild as 1st order low pass filter for woofer. simplest thing to do. will cut anything above 250. using first order will automatically allow some overlap. isn't it?

Vikram

1st order crossovers are the best for audiophiles because they dont invert the phase of the signal, however 3db/octave is simply not enough

getting an inductor fabricated for a woofer is not advisable simply because its going to be very very huge and 400-500 turns of wire is going to add lot of resistance

Go for an active crossover for woofers
 

jaudere

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Thanks Cranky for the explanation.

What i have gatheterd till now is that, the impedance of a driver increases if a frequency beyond the crossover point is presented. it does not decrease.so in any case, it does not drop down. so it shouldn't be risky as far amplifier health goes.

this is a bit complicated as i am doctor and not a techie. i have found a way out, may affect quality though.

I wanted the final impedance to be 8 ohms.
my philips full range will be 8 ohm, woofer 4 ohm and 3 rd full range driver will be a 3 way car speaker with 4 ohms (chose that the car speakers have builtin crossover and will give better high freqency output than the full range speaker). all connected in parallel will give me 8 ohms.

the sesnitivity is different. car speaker: 89dB/w/m, full range :unknown (but it is usually 93-95) and woofer:98. so though car speaker will sum up in impedance, it will contribute less to sound output. this method i found a bit better than adding simple 4 ohm resistor in parallel. lets see what happens.

for trial purpose i have bought cheap car speakers.i already have 10" 4 ohm subs working for me. will mount the drivers on baffle soon.
 

jaudere

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hello friends. Here is a new question. I got hold of a philips 3 way cross over. It says 100w rms with 8 ohm crossover impedance. It mentions nothing else. No cut off frequencies given & i am not going to try to find it out if it gives me good results. My problem is that it doesnt mention what should be impedance of the drivers that are attached to it. Does it have to be 8 ohm or 4 ohm is acceptable? My mid & tweet are 8 ohm each but the woofer is 4 ohm. A friend has used 4 ohm woofer with it but i just want to be sure before i start wiring. So the question is if the impedance of crossover at input levet is 8 ohm ,what should be the impedance of the drivers attached to it?
 

jaudere

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had a closer look at the crossover. 4 coils. 2 air core & 2 probably iron core. Values not mentioned. 4 capacitors. 2 having 1micro f value & 2 having 22micro f value. From whatever knowledge i have, i have come to a conclusion that it is a 2nd order crossover and crossover point between mid & tweet is around 12k hz. (from that 1mf capacitor) but i am unable to find the lower crossover point. If philips follows simple tables , it should be around 600hz but i need the coil value to find it out. How can i find it? Again from the tables, if i attach 4 ohm woofer , crossover point will likely shift to 1k hz. But i know it is not so straight forward. With 2nd order slope, phase shift is going to be a problem but i should be fine if i reverse the polarity of mid. Someone please tell me how can a crossover keep impedance at around 8 when i am attaching 3 drivers at 8 ohm in parallel (albeit through the circuit)
 

jaudere

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thanks a lot for that explanation cranky. Got it to some degree. I cant find the crossover points as i dont have all the gadgets you mentioned. But please tell me,if the crossover impedance is 8 ohm for this xo,what could be the allowed driver impedance for each of the 3 drivers. I mean i got the point that i must follow the rules but philips has not mentioned any rules. Do i have to use 8 ohm drivers only or 4 ohm is acceptable.
 

jaudere

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thanks once again cranky. I already have 8 ohm mid & tweet. Woofer was 4 ohm. So i will use 2woofers in series to make it 8ohm. But let me ask you something more. If i use 4 ohm woofer in place of 8 ohm,will it change the final impedance seen by amp?and secondly will it change cut off freq only for woofer or for other drivers as well? Another thing. I understood how coils & capacitors decide cut off freq but how do they affect rms power?my xo mentions 100w rms. What does it mean. If my drivers have higher rated power ,what will happen?i know that i am never going to reach 100w rms while listening to music. Regards.
 

grubyhalo

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I was tempted to suggest an L-pad after your x-over for equalizing the impedance, but am not too sure...
 

jaudere

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hello cranky, please help me again.please tell me what will happen to the impedance seen by amp if i do not connect the woofer to the 3 way crossover ? I mean that i have a 3 wAY XO. I will connect mid & tweeter to the crossover and i will not connect anything to woofer terminal. You will ask me about why i want to do so. You have read my 2 amp & 1 speaker thread & you have answered my query(i knew you would be the one to help me. Thanks). So what i want to do is connect the woofer part to the sub amp and leave the woofer terminal of xo open.i have tried this & there was sound but i tried it only for few min as i didnt know whether that will damage the main amp.
 

jaudere

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hello cranky. I am very sorry for not acknowledging the active crossover suggestion. But i have given a thought to it. My reason for avoiding it was simple. I did not want 3 amps to work for me simultaneously. The cost,space & the power consumption will go up. The added cost of 2 amps & 1 active xo will go overboard. You can guess it from the fact that i bought a discontinued yamaha model as my AVR as i got a discount of 4k with full warranty. I know that , in future, i will be going towards active xo. In fact what i am going to use now is kind of built in active xo of the receiver for lower freq. I am going to use it because i have a locally made stereo amp lying idle. I had used that amp as sub amp previously & it performed to my satisfation. But cant think buying active xo & 2 good amps at this stage. I hope this is a satisfactory answer. Now let me ask you a question. How do you create a jumper?is a simple copper wire okay?
 

jaudere

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hello cranky. Thats a good suggestion. Will definitely keep that in mind. For now i have finally got something like a 4 way system. All this communication is on my mobile. I am unable to post pictures. Each speaker has 4 drivers. A tweeter , a philips full range as mid , a philips full range as mid bass & locally made 15" woofer as the bass driver. The first 3 speakers are connected through 3 way passive xo & bass driven by separate amp which is connected to sub out of av receiver.the results are good . This was an absolutely budget system. Speakers excluding amps cost me 8000rs. Getting better drivers worth another 5k for mids will be a big step up.
 

jaudere

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hello cranky. Please tell me if the following set up will work or no. CDP>3way active xo>Mids to analogue front input of 5.1 avr, HF to the surrounds and LF to centre input> output through respective speaker terminals. I think you have mentioned similar thing but for a 2 way setup. This LF To the centre was something different i had in mind. Please tell me some decently priced 3 way active xo. If i use active xo, what kind of input it has digital or analogue? Will it decode the signals or will CDP have to do it? Regards.
 
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