Speakerplans.com Homepage
Forum Home Forum Home > General > Newbie Discussion
  New Posts New Posts RSS Feed - Passive crossover attenuators
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Passive crossover attenuators
 Post Reply Post Reply Page  <123>
Author
Message
  Topic Search Topic Search  Topic Options Topic Options
Risc_Terilia View Drop Down
Young Croc
Young Croc


Joined: 15 December 2007
Status: Offline
Points: 699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Risc_Terilia Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 1:25pm
Originally posted by Earplug Earplug wrote:

Passive crossovers are all an estimation anyway and best tweaked by testing. Hopefully it won´t make too much difference to your cabs. What are you using the xover for?


An X15, between a SN15B and BMD450.  
Back to Top
studio45 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 16 October 2007
Location: United Kingdom
Status: Offline
Points: 3864 		Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 2:54pm
If you're adding an L-Pad, then you have the opportunity to add some EQ as well, to flatten out the top end. BMD450 starts rolling off at about 11kHz and can benefit from some boost above that. 
To achieve this, you would add a series LCR (inductor, cap, resistor) string in parallel with the series resistor of the L-Pad. The LCR string is sized such that it presents a low resistance at some very high frequency, so it allows more HF to "bypass" the L-Pad and go directly to the driver.
By doing this you can run the box in situations where an EQ is not available, and still have good high frequency response.
The components are quite small. A good starting point for a low-Q boost centred at 15kHz would be 60uH (0.06mH) in series with 1.9uF, taking the assumption that there will be some DC resistance in the coil - wind it with fine wire, it doesn't have to take much power. This will start to boost from about 11kHz and continue to act until about 18kHz. The amount of boost of course depends on how much your L-Pad would have taken off, so in your case about 5.5dB.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
Back to Top
Risc_Terilia View Drop Down
Young Croc
Young Croc


Joined: 15 December 2007
Status: Offline
Points: 699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Risc_Terilia Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 3:05pm
Originally posted by studio45 studio45 wrote:

If you're adding an L-Pad, then you have the opportunity to add some EQ as well, to flatten out the top end. BMD450 starts rolling off at about 11kHz and can benefit from some boost above that. 
To achieve this, you would add a series LCR (inductor, cap, resistor) string in parallel with the series resistor of the L-Pad. The LCR string is sized such that it presents a low resistance at some very high frequency, so it allows more HF to "bypass" the L-Pad and go directly to the driver.
By doing this you can run the box in situations where an EQ is not available, and still have good high frequency response.
The components are quite small. A good starting point for a low-Q boost centred at 15kHz would be 60uH (0.06mH) in series with 1.9uF, taking the assumption that there will be some DC resistance in the coil - wind it with fine wire, it doesn't have to take much power. This will start to boost from about 11kHz and continue to act until about 18kHz. The amount of boost of course depends on how much your L-Pad would have taken off, so in your case about 5.5dB.

Great thanks for the advice and explanation.
Back to Top
ceharden View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 05 June 2005
Location: Southampton
Status: Offline
Points: 11776 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 3:37pm
A good starting point would be an 8.2Ohm resistor in the R2 position then experiment with different values of capacitor in the C3 position (which puts it in parallel) to get the HF lift desired.  Start with something like 2.2uF.  You may need to remove some shorting links which have most likely been added to the reverse of the board.
Back to Top
ceharden View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 05 June 2005
Location: Southampton
Status: Offline
Points: 11776 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 3:42pm
Originally posted by Risc_Terilia Risc_Terilia wrote:

Originally posted by Earplug Earplug wrote:

Ok - a true DIY board.  Disapprove

Glad you got it sorted, anyway.   Thumbs Up



Yeah well Blue Aran have been helpful as they always are.  The only thing is that I've not been able to get the precise resistance values and honestly I don't have the maths to reverse the formula to give me attenuation from resistances but intuitively I think that the only real difference will be a slight alteration in overall resistance as seen by the crossover.  

Attenuation networks are far from an exact science and you actually have to change the resistance a fair amount to get an audible difference.  Trial and error is likely to be the best approach and you'll probably still end up doing the fine tuning with some EQ depending on the venue anyway.
Back to Top
cravings View Drop Down
Old Croc
Old Croc
Avatar

Joined: 30 January 2007
Location: Ireland
Status: Offline
Points: 7442 		Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 3:57pm
Back to Top
Risc_Terilia View Drop Down
Young Croc
Young Croc


Joined: 15 December 2007
Status: Offline
Points: 699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Risc_Terilia Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2017 at 4:57pm
Originally posted by studio45 studio45 wrote:

If you're adding an L-Pad, then you have the opportunity to add some EQ as well, to flatten out the top end. BMD450 starts rolling off at about 11kHz and can benefit from some boost above that. 
To achieve this, you would add a series LCR (inductor, cap, resistor) string in parallel with the series resistor of the L-Pad. The LCR string is sized such that it presents a low resistance at some very high frequency, so it allows more HF to "bypass" the L-Pad and go directly to the driver.
By doing this you can run the box in situations where an EQ is not available, and still have good high frequency response.
The components are quite small. A good starting point for a low-Q boost centred at 15kHz would be 60uH (0.06mH) in series with 1.9uF, taking the assumption that there will be some DC resistance in the coil - wind it with fine wire, it doesn't have to take much power. This will start to boost from about 11kHz and continue to act until about 18kHz. The amount of boost of course depends on how much your L-Pad would have taken off, so in your case about 5.5dB.

Which value should I use for the resistor in the LCR plesae?
Back to Top
studio45 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 16 October 2007
Location: United Kingdom
Status: Offline
Points: 3864 		Post Options Post Options   Thanks (1) Thanks(1)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2017 at 2:21pm
There is no single answer for that. It depends on how much boost you want. For the maximum possible boost use no extra resistor, just rely on the inherent resistance of the inductor. For less boost, use a larger resistor. When the value becomes more than twice as large as the L-pad's series resistor, you will be adding very little boost. So that is your window of useful values - zero to 2x the L-pad series value. 

The resistor also affects the Q or frequency range of the boost. Small value or no resistor will give the narrowest boost the L and C values will allow, larger values will broaden the effect (but reduce the amount of boost, as discussed above). Again, this is a matter of taste and you can choose any Q that sounds good.

There is a very useful "RLC calculator" on the Iris Strassacker website here.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
Back to Top
Risc_Terilia View Drop Down
Young Croc
Young Croc


Joined: 15 December 2007
Status: Offline
Points: 699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Risc_Terilia Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2017 at 4:34pm
Originally posted by studio45 studio45 wrote:

There is no single answer for that. It depends on how much boost you want. For the maximum possible boost use no extra resistor, just rely on the inherent resistance of the inductor. For less boost, use a larger resistor. When the value becomes more than twice as large as the L-pad's series resistor, you will be adding very little boost. So that is your window of useful values - zero to 2x the L-pad series value. 

The resistor also affects the Q or frequency range of the boost. Small value or no resistor will give the narrowest boost the L and C values will allow, larger values will broaden the effect (but reduce the amount of boost, as discussed above). Again, this is a matter of taste and you can choose any Q that sounds good.

There is a very useful "RLC calculator" on the Iris Strassacker website here.

That's some awesome knowledge thanks very much.  I actually tried a broad 11k boost but to be honest it really sounded a lot like before I had the L-Pad in at all but I'll play about with the parametric and try to mirror the settings on the calculator.  Really can't thank you enough for all your help Clap
Back to Top
Andy Kos View Drop Down
Old Croc
Old Croc


Joined: 15 May 2007
Location: Southampton
Status: Offline
Points: 3038 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 19 June 2017 at 1:26am
This board doesnt use an L-Pad, you can use the resistors from the chart here:


They are 2 series resistors, to give a variety of configuration options, the guide above is the most basic.

You can also just use R2 for attenutation, and make R1 large (20 ohms or more) and fit a polyswitch of appropriate size into PTC1. When the power to the tweeter goes too high, the polyswitch goes open circuit, adding R1 into the circuit. This acts a bit like a harsh limiter if you overdrive your HF, ducking the volume by several dB for a while until the power levels drop.

As Chris mentions, you can put a capacitor in parallel with R2, and 2.2uF is a very good starting point. This gives a 6db/octave lift to help balance to frequency response, giving a hi-shelf boost.
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
Back to Top
Andy Kos View Drop Down
Old Croc
Old Croc


Joined: 15 May 2007
Location: Southampton
Status: Offline
Points: 3038 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 19 June 2017 at 1:30am
Originally posted by Risc_Terilia Risc_Terilia wrote:

Originally posted by Earplug Earplug wrote:

"Will this crossover give less power to the high pass output or will it just do equal split?"

With the xover point at 2k2, you only need about 15%-20% of the overall power going to the top end. The xover will ensure that happens - and if that is still too much, it looks like you can fit a couple of resisters to attenuate the signal. Didn´t the board come with any instructions?



I tried it out last night, by my reckoning it needs about 5.5dB off the top so I've bought the appropriate resistors.  No there was not paperwork.  

We have published the attenuation information online, I think at the time you made the purchase we were still finalising the pdf. It is now included with all crossovers.

We have started phasing out the old boards, which had been in use for probably 20 years or so, and we're updating the board to take higher spec components for higher power handling, also to make them more versatile.

Mike Keene (Convair) who made the Link Dynamics crossovers decided it was time to hang up his soldering iron and retire, so we have taken over the manufacturing of these crossovers. As the old stock runs out, we will replace the boards with new options, the first step was to add attenuation (sadly lacking in the old boards) and in the future we will be putting together more variations of customisable crossovers.
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
Back to Top
Risc_Terilia View Drop Down
Young Croc
Young Croc


Joined: 15 December 2007
Status: Offline
Points: 699 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Risc_Terilia Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2017 at 4:33pm
Originally posted by Andy Kos Andy Kos wrote:

Originally posted by Risc_Terilia Risc_Terilia wrote:

Originally posted by Earplug Earplug wrote:

"Will this crossover give less power to the high pass output or will it just do equal split?"

With the xover point at 2k2, you only need about 15%-20% of the overall power going to the top end. The xover will ensure that happens - and if that is still too much, it looks like you can fit a couple of resisters to attenuate the signal. Didn´t the board come with any instructions?



I tried it out last night, by my reckoning it needs about 5.5dB off the top so I've bought the appropriate resistors.  No there was not paperwork.  

We have published the attenuation information online, I think at the time you made the purchase we were still finalising the pdf. It is now included with all crossovers.

We have started phasing out the old boards, which had been in use for probably 20 years or so, and we're updating the board to take higher spec components for higher power handling, also to make them more versatile.

Mike Keene (Convair) who made the Link Dynamics crossovers decided it was time to hang up his soldering iron and retire, so we have taken over the manufacturing of these crossovers. As the old stock runs out, we will replace the boards with new options, the first step was to add attenuation (sadly lacking in the old boards) and in the future we will be putting together more variations of customisable crossovers.


That all sounds really positive Andy.  I didn't mean the lack of paperwork to read as a critisism - I wouldn't expect a product like this to have total hand holding :)
Back to Top
 Post Reply Post Reply Page  <123>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.094 seconds.