Parallel cap to create 1.5 way?

boone · 16th November 2006, 01:42 AM

A couple of times recently I've seen mention of useing a parallel cap ( like a zobel without the resistor ) to low pass one of the drivers in a 1.5 way configuration. Both times the drivers were hooked up in series. Is there something specific to a series hook up of the drivers that makes this work or would it work if the drivers were in parallel also? Or for that matter each driver being driven by a seperate amp channel ( my situation )?

Would the value of the cap be the same as would be used to high pass the driver at the same frequency?

Is the slope 6 db per octave? And does the slope steepen as the drivers impedence rises as opposed to a series inductor on an unzobeled driver where the rising impedence reduces the slope?

Thank you.

boone

sreten · 16th November 2006, 12:23 PM

Hi,

You need a series inductor to make a 1.5 way arrangement, the drivers in parallel.

You cannot make a 1.5 way syetem with the drivers in series.

/sreten.

Paul W · 16th November 2006, 12:58 PM

The series cap configuration is useful for increasing LF power handling without adding baffle step compensation.

The speaker linked below used a series cap xo for the .5 woofers with line level baffle comp. The page explains how it works.

Value of the cap was determined for the specific purpose using LspCAD, so I didn't have any reason to see if was the same value as a highpass at the same frequency. The slope was ~6db per octave but don't remember if it varied with impedance (I'm thinking it didn't vary because the impedance of each driver is equal at any given frequency...no zobel was used).

Can't use it for parallel drivers. If you are using a separate amp for both drivers, you'll need to go with an inductor in series with the .5 driver...or go active.
Paul

MMTMM with cap

sreten · 16th November 2006, 01:33 PM

Hi,

OK. you can use the series capacitor configuration but you don't get BSC.

Each speaker driven by a seperate amplifier is equivalent to the parallel
configuration and a parallel capacitor cannot be used on one driver, a
series inductor would be used.
Though its a lot easier to but a passive filter on the amplifier input.
With seperate amplifiers you will get BSC.

/sreten.

boone · 16th November 2006, 01:45 PM

Stren & Paul W,

Thank you for your replies.

I am not after bsc.

I'm wondering why when the drivers are hooked in series the cap "shunts" HF so the driver plays as a .5 ( low passing it in effect )
but the same driver by itself, shunted with a cap in the same way doesn't?

Thank you
boone

Paul W · 16th November 2006, 02:18 PM

Boone,
SS amp acts as a constant voltage source...so the amp sees the cap as another load in parallel with driver. Amp is trying to drive a short at HF...not good!

Some resistance/reactance in series is needed to isolate cap from amp. Second driver in series provides isolation and allows cap to roll off HF.
Paul

boone · 16th November 2006, 02:33 PM

Paul W,

How much series R is needed to do this ( min. )?

Thank you
boone

v-bro · 16th November 2006, 02:39 PM

Just a couple of ohms (4 to 10 mostly), this is often done with ESLs because they tend to be a very heavy capacitive load too.

sreten · 16th November 2006, 03:39 PM

Quote:

Originally posted by boone

How much series R is needed to do this ( min. )?
boone

Too much, ruins the Qt of the bass alignment,

/sreten.

boone · 16th November 2006, 04:40 PM

To all who have replied,

Thank you for your help.
I would like to rephrase one of my earlier questions. If I had a driver that I wanted to high pass at 200 hz - and at that freq. it's impedence was 6 ohms -and the various tables/calculators sugguested a 130uf cap in series to accomplish that, would that same 130uf cap paralleled with the driver create a kind of low pass at 200 hz?

Would 4 ohms of series R before the parallel cap affect the value of the cap?

v-bro
Is 4 ohms the absolute minimum to isolate the cap (less is better)

sreten
I think I have enough volume to accommodate a moderate increase in Qt

Thank you
boone

16th November 2006, 01:42 AM	#1
boone diyAudio Member Join Date: Jan 2004 Location: Portland, Or.	Parallel cap to create 1.5 way? A couple of times recently I've seen mention of useing a parallel cap ( like a zobel without the resistor ) to low pass one of the drivers in a 1.5 way configuration. Both times the drivers were hooked up in series. Is there something specific to a series hook up of the drivers that makes this work or would it work if the drivers were in parallel also? Or for that matter each driver being driven by a seperate amp channel ( my situation )? Would the value of the cap be the same as would be used to high pass the driver at the same frequency? Is the slope 6 db per octave? And does the slope steepen as the drivers impedence rises as opposed to a series inductor on an unzobeled driver where the rising impedence reduces the slope? Thank you. boone

16th November 2006, 02:39 PM	#8
v-bro diyAudio Member Join Date: May 2006	Just a couple of ohms (4 to 10 mostly), this is often done with ESLs because they tend to be a very heavy capacitive load too. __________________ Max. cone displacement can be several foot on any speaker!Too bad it can be done only once......http://www.41hz.com http://www.octopusamps.com/http://sound.westhost.com/http://www.t-linespeakers.org/http://www.marchandelec.com/

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Create your own DAB signal?	nichall	Digital Source	1	22nd June 2009 03:17 PM
Parallel amps & Parallel Voice coils?	officeboy	Multi-Way	7	26th May 2004 07:12 PM
How do I create a poll???	Prune	The Lounge	3	31st March 2004 08:08 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

16th November 2006, 12:23 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, You need a series inductor to make a 1.5 way arrangement, the drivers in parallel. You cannot make a 1.5 way syetem with the drivers in series. /sreten.

16th November 2006, 12:58 PM	#3
Paul W diyAudio Member Join Date: Oct 2003 Location: North Georgia	The series cap configuration is useful for increasing LF power handling without adding baffle step compensation. The speaker linked below used a series cap xo for the .5 woofers with line level baffle comp. The page explains how it works. Value of the cap was determined for the specific purpose using LspCAD, so I didn't have any reason to see if was the same value as a highpass at the same frequency. The slope was ~6db per octave but don't remember if it varied with impedance (I'm thinking it didn't vary because the impedance of each driver is equal at any given frequency...no zobel was used). Can't use it for parallel drivers. If you are using a separate amp for both drivers, you'll need to go with an inductor in series with the .5 driver...or go active. Paul MMTMM with cap

16th November 2006, 01:33 PM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, OK. you can use the series capacitor configuration but you don't get BSC. Each speaker driven by a seperate amplifier is equivalent to the parallel configuration and a parallel capacitor cannot be used on one driver, a series inductor would be used. Though its a lot easier to but a passive filter on the amplifier input. With seperate amplifiers you will get BSC. /sreten.

16th November 2006, 01:45 PM	#5
boone diyAudio Member Join Date: Jan 2004 Location: Portland, Or.	Stren & Paul W, Thank you for your replies. I am not after bsc. I'm wondering why when the drivers are hooked in series the cap "shunts" HF so the driver plays as a .5 ( low passing it in effect ) but the same driver by itself, shunted with a cap in the same way doesn't? Thank you boone

16th November 2006, 02:18 PM	#6
Paul W diyAudio Member Join Date: Oct 2003 Location: North Georgia	Boone, SS amp acts as a constant voltage source...so the amp sees the cap as another load in parallel with driver. Amp is trying to drive a short at HF...not good! Some resistance/reactance in series is needed to isolate cap from amp. Second driver in series provides isolation and allows cap to roll off HF. Paul

16th November 2006, 02:33 PM	#7
boone diyAudio Member Join Date: Jan 2004 Location: Portland, Or.	Paul W, How much series R is needed to do this ( min. )? Thank you boone

16th November 2006, 04:40 PM	#10
boone diyAudio Member Join Date: Jan 2004 Location: Portland, Or.	To all who have replied, Thank you for your help. I would like to rephrase one of my earlier questions. If I had a driver that I wanted to high pass at 200 hz - and at that freq. it's impedence was 6 ohms -and the various tables/calculators sugguested a 130uf cap in series to accomplish that, would that same 130uf cap paralleled with the driver create a kind of low pass at 200 hz? Would 4 ohms of series R before the parallel cap affect the value of the cap? v-bro Is 4 ohms the absolute minimum to isolate the cap (less is better) sreten I think I have enough volume to accommodate a moderate increase in Qt Thank you boone

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)