Question about modelling Lpads in LSPCad

morbo · 11th March 2005, 05:47 PM

I am building a 2 way ported tower for home theater. The 'tweeter' will be a TangBand 871, crossed over 2nd order to a ported Dayton RS225 at 600hz. I have modelled all this in LSPCad and it seems to work out fairly well, nice phase tracking, fairly flat FR, low excursion demands on the 871, and impedance doesnt dip below 5.5 ohms anywhere in the range.

I am purposely crossing over at the spot the baffle step starts to roll off the bass. My idea was to use an LPad on the tweeter or in some other way adjust the relative levels of the 2 in order to have a crude sort of adjustable baffle step compensation. I simmed the RS225 in-baffle using EDGE, and the rolloff started at ~ 600hz, so I thought that if I XO at 600hz as well, I can just adjust the relative levels of the drivers to get the desired BSC lift in the low frequencies.

My question is, how do I model putting this Lpad on the tweeter in LspCAD? I want to see how the LPad affects the modelled response. I am currently modelling the system as a 'simple 2 way', do I use the 'attentuator' field in the tweeter XO?

ergo · 11th March 2005, 05:51 PM

Yes the attenuator is the correct setting if you use simple filter..

Ergo

morbo · 11th March 2005, 05:55 PM

thanks ergo! Is this true even for the adjustable Lpads with the dial on them?

11th March 2005, 05:47 PM	#1
morbo diyAudio Member Join Date: Sep 2004 Location: Guelph, Ontario	Question about modelling Lpads in LSPCad I am building a 2 way ported tower for home theater. The 'tweeter' will be a TangBand 871, crossed over 2nd order to a ported Dayton RS225 at 600hz. I have modelled all this in LSPCad and it seems to work out fairly well, nice phase tracking, fairly flat FR, low excursion demands on the 871, and impedance doesnt dip below 5.5 ohms anywhere in the range. I am purposely crossing over at the spot the baffle step starts to roll off the bass. My idea was to use an LPad on the tweeter or in some other way adjust the relative levels of the 2 in order to have a crude sort of adjustable baffle step compensation. I simmed the RS225 in-baffle using EDGE, and the rolloff started at ~ 600hz, so I thought that if I XO at 600hz as well, I can just adjust the relative levels of the drivers to get the desired BSC lift in the low frequencies. My question is, how do I model putting this Lpad on the tweeter in LspCAD? I want to see how the LPad affects the modelled response. I am currently modelling the system as a 'simple 2 way', do I use the 'attentuator' field in the tweeter XO?

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11th March 2005, 05:51 PM	#2
ergo diyAudio Member Join Date: Mar 2001 Location: Tallinn, Estonia	Yes the attenuator is the correct setting if you use simple filter.. Ergo

11th March 2005, 05:55 PM	#3
morbo diyAudio Member Join Date: Sep 2004 Location: Guelph, Ontario	thanks ergo! Is this true even for the adjustable Lpads with the dial on them?

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