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Passive crossover attenuators

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snowflake View Drop Down
Old Croc
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Joined: 29 December 2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2017 at 6:23pm
Originally posted by Risc_Terilia Risc_Terilia wrote:

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?


there's little point using a notch filter when an L-pad is in the circuit as shown in the diagram. the L-pad smooths the impednace spike sufficiently for the crossover to work well. the main thing is for the crossover frequency to be at least one octave above the resonance frequency.
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Andy Kos View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2017 at 9:42pm
Originally posted by Risc_Terilia Risc_Terilia wrote:

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 :)

Our aim is to make this a user configurable DIY product, as well as an off the shelf product. It can be quite time consuming to get all the relevant information together, and it's not top of the list of things to do, so we deal with a bit at a time as and when time allows.

A certain amount of user configurability is something I feel is lacking in many solutions currently available, so we're aiming to address that in small steps as and when we can.


just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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