Hello people,
Some dumb questions here..... 🙂
It seems books like Weems', Murphy' and Alden (ok - the only one I don't have is Dickason) don't specify recommended minimum values for parameters when choosing LCR components for crossovers.
Resistors:
- What power ratings do the resistors need to be rated at? Different rule of thumb for woofers (100watt+) and tweeters (10 watts?
- Are sandcast / wirewound types acceptable for a speaker?
- What about tolerances and matching?
Capacitors:
- 100V DC enough?
- Metallised polyprop preferred over mylar and other NP or polarised types?
- Again - tolerances and matching?
Inductors:
- aircore preferred over iron core or steel laminate
- Maximum tolerable DC resistance?
- Power handling?
....-> Any other relevant parameters when choosing XO components?
If the "guidelines" are dependent on cost of drivers - assume I'm spending about US$130 on drivers for a 2-way.
Maybe I'm just missing that good fundamental electronics / speaker crossover book... but none of the above texts describe these adequately (well, ok Weem's touches on them).
Thanks,
David.
Some dumb questions here..... 🙂
It seems books like Weems', Murphy' and Alden (ok - the only one I don't have is Dickason) don't specify recommended minimum values for parameters when choosing LCR components for crossovers.
Resistors:
- What power ratings do the resistors need to be rated at? Different rule of thumb for woofers (100watt+) and tweeters (10 watts?
- Are sandcast / wirewound types acceptable for a speaker?
- What about tolerances and matching?
Capacitors:
- 100V DC enough?
- Metallised polyprop preferred over mylar and other NP or polarised types?
- Again - tolerances and matching?
Inductors:
- aircore preferred over iron core or steel laminate
- Maximum tolerable DC resistance?
- Power handling?
....-> Any other relevant parameters when choosing XO components?
If the "guidelines" are dependent on cost of drivers - assume I'm spending about US$130 on drivers for a 2-way.
Maybe I'm just missing that good fundamental electronics / speaker crossover book... but none of the above texts describe these adequately (well, ok Weem's touches on them).
Thanks,
David.
As i understand it all this depends very much on your speakers.
max wattage: easy to calculate from wattage of speakers. Max voltage: what max voltage comes out of your amp + something for safety?
aircore preferred: yes DC resitance, i wouldn´t care for this. matching, tolerance: i would take what i get for reasonable money and use some measurement equipment to match....
max wattage: easy to calculate from wattage of speakers. Max voltage: what max voltage comes out of your amp + something for safety?
aircore preferred: yes DC resitance, i wouldn´t care for this. matching, tolerance: i would take what i get for reasonable money and use some measurement equipment to match....
Disclaimer:
These are my personal recommendations. Other's may think considerably different:
Resistors:
- What power ratings do the resistors need to be rated at? Different rule of thumb for woofers (100watt+) and tweeters (10 watts?
* It is not this easy in many cases. For Zobel's on a low frequency woofer, you may be able to get by with 5 watts as the point the zobel kicks in the impedance of the cross-over is sufficient. However, the "theoretical" requirement for a resistor in a high powered mid-bass could be 50 watts if you ran a continous sine wave of the "right" frequency into it. However, I have found that 20 watts for the Zobel on most mid-bases to be enough. I am not a big fan of tweeter response matching with resistors, but if you must, again, you must calculate. If you are using small value resistors, say 1 or 2 ohm with an 8 ohm tweeter, you may find that 5 or 10 watts is more than enough. However, if you are in the range of the impedance of the tweeter, you will need the same wattage as the tweeter!
- Are sandcast / wirewound types acceptable for a speaker?
* Go non-inductive. Best quality resisitance for tweeters, good quality for Zobels.
- What about tolerances and matching?
* 2 % for tweeters, 5% for zobels seems to work fine.
Capacitors:
- 100V DC enough?
* Should be enough in theory, however, higher voltage capacitors often have better specifications, but not always.
- Metallised polyprop preferred over mylar and other NP or polarised types?
* Film polyprop best, metalized next in general. Then Polyester, then Electrolytic NP ... for speakers at least.
- Again - tolerances and matching?
* Hmmm.... if you can get 2% for tweeters, great. 5% at a minimum. The issue is the inductor tolerance often. Hate to have both off by 5-10%.
Inductors:
- aircore preferred over iron core or steel laminate
* Aircore are often best for mid-bass and tweeter, however, for low bass, I will always take an iron core. I find the lower DC-resistance to be more important at low frequencies. Some designers prefer them even for mid-bass. In any case, get the largest guage wire you can afford. Foil ones tend to have lower DCR.
- Maximum tolerable DC resistance?
* Matter of opinion and must be part of the overall cross-over design
- Power handling?
* Never had an issue with anything rated 300watts and up, though most of what I use is rated much higher.
Alvaius
These are my personal recommendations. Other's may think considerably different:
Resistors:
- What power ratings do the resistors need to be rated at? Different rule of thumb for woofers (100watt+) and tweeters (10 watts?
* It is not this easy in many cases. For Zobel's on a low frequency woofer, you may be able to get by with 5 watts as the point the zobel kicks in the impedance of the cross-over is sufficient. However, the "theoretical" requirement for a resistor in a high powered mid-bass could be 50 watts if you ran a continous sine wave of the "right" frequency into it. However, I have found that 20 watts for the Zobel on most mid-bases to be enough. I am not a big fan of tweeter response matching with resistors, but if you must, again, you must calculate. If you are using small value resistors, say 1 or 2 ohm with an 8 ohm tweeter, you may find that 5 or 10 watts is more than enough. However, if you are in the range of the impedance of the tweeter, you will need the same wattage as the tweeter!
- Are sandcast / wirewound types acceptable for a speaker?
* Go non-inductive. Best quality resisitance for tweeters, good quality for Zobels.
- What about tolerances and matching?
* 2 % for tweeters, 5% for zobels seems to work fine.
Capacitors:
- 100V DC enough?
* Should be enough in theory, however, higher voltage capacitors often have better specifications, but not always.
- Metallised polyprop preferred over mylar and other NP or polarised types?
* Film polyprop best, metalized next in general. Then Polyester, then Electrolytic NP ... for speakers at least.
- Again - tolerances and matching?
* Hmmm.... if you can get 2% for tweeters, great. 5% at a minimum. The issue is the inductor tolerance often. Hate to have both off by 5-10%.
Inductors:
- aircore preferred over iron core or steel laminate
* Aircore are often best for mid-bass and tweeter, however, for low bass, I will always take an iron core. I find the lower DC-resistance to be more important at low frequencies. Some designers prefer them even for mid-bass. In any case, get the largest guage wire you can afford. Foil ones tend to have lower DCR.
- Maximum tolerable DC resistance?
* Matter of opinion and must be part of the overall cross-over design
- Power handling?
* Never had an issue with anything rated 300watts and up, though most of what I use is rated much higher.
Alvaius
Thanks alvaius for your thorough response.
I would have thought the lower the impedance, the more current drawn, therefore higher power handling required.
Maybe my point shows a general lack of my understanding of ohm's law / electrical physics in general.
BTW - I thought most modern SS amps are current voltage (if so, power output must therefore vary by current), and if so, why are caps rated at 100v+ required....
I must do some more basic reading
Thanks.
David.
Is this for a resistor in a resonance compensation (eg. series notch filter) or tweeter attenuation?
I would have thought the lower the impedance, the more current drawn, therefore higher power handling required.
Maybe my point shows a general lack of my understanding of ohm's law / electrical physics in general.
BTW - I thought most modern SS amps are current voltage (if so, power output must therefore vary by current), and if so, why are caps rated at 100v+ required....
I must do some more basic reading
Thanks.
David.
Correction
Should have read:
BTW - I thought most modern SS amps are constant voltage (if so, power output must therefore vary by current), and if so, why are caps rated at 100v+ required....
David.
Should have read:
BTW - I thought most modern SS amps are constant voltage (if so, power output must therefore vary by current), and if so, why are caps rated at 100v+ required....
David.
Rating of XO components
I’m about to buy the components for my first XO; as this is a first project, I’ll use an existing design. In fact I went into the shop with a list of resistors & capacitors, but discovered that I need to consider their power rating.
The drivers are Usher: the 6.5 inch & the tweeter, rated about 70 watts, sensitivity about 88 dB, to be crossed at 2.2 kHz; to be used in a room 4.9 m by 6 m (15’ * 19’) with say a 50 watt amp.
A rule of thumb suggested to me is to allow 5 watts for the tweeter, and 10 watts for the woofer. Seems too low to me.
My logic is that the load they will experience depends on how hard they are likly to be driven, which depends on:
- maximum listening level
- room size, and
- senstivity
It's not clear how impedance affects this. Alvaius's answer appeared to assume a zobel. Anyone know:
- what is the approach where there is no zobel?
- For the "theoretical" requirement
is their a formula for watts for the resistors?
or for the Capacitors/ Inductors??
I've ordered some books (Lnacaster & Singrim), but don't know if they'll deal with this.
I’m about to buy the components for my first XO; as this is a first project, I’ll use an existing design. In fact I went into the shop with a list of resistors & capacitors, but discovered that I need to consider their power rating.
The drivers are Usher: the 6.5 inch & the tweeter, rated about 70 watts, sensitivity about 88 dB, to be crossed at 2.2 kHz; to be used in a room 4.9 m by 6 m (15’ * 19’) with say a 50 watt amp.
A rule of thumb suggested to me is to allow 5 watts for the tweeter, and 10 watts for the woofer. Seems too low to me.
My logic is that the load they will experience depends on how hard they are likly to be driven, which depends on:
- maximum listening level
- room size, and
- senstivity
It's not clear how impedance affects this. Alvaius's answer appeared to assume a zobel. Anyone know:
- what is the approach where there is no zobel?
- For the "theoretical" requirement
is their a formula for watts for the resistors?
or for the Capacitors/ Inductors??
I've ordered some books (Lnacaster & Singrim), but don't know if they'll deal with this.
Recommended Passive Crossover Components
Dave this is good (17 odd pages):
http://ldsg.snippets.org/appdx-e.php3
😎
Dave this is good (17 odd pages):
http://ldsg.snippets.org/appdx-e.php3
😎
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