WAW via an external Subwoofer

Jump to Latest
M

Malm7913

Member
Joined 2021
#1
Hi Guys,

I've been reading about WAWs and want to try to make a single driver speaker where I use my Dynaudio Sub from about 120 Hz and down. Pretty standard.

But what if I want to add a high-pass-filter on the single driver?

Two questions:

- Is there a way to add a high-pass-filter that doesn't compromise the purity of a the single driver? (I really like the idea of practically nothing but speaker wire between the amplification and the driver).

- Is there a way to add a switch where I can toggle the high-pass-filter on and off?

I'm a complete amateur and, admittedly, part of the attraction of a single driver speaker is the simplicity of no crossover.

Best regards
Mads
 
#2
A couple of different ways that you can do it. You can actively crossover upstream of your amplification (DSP or analog) or you can put in an inline filter on full range driver. You can add a switch to toggle the active crossover on and off. I am assuming you would be using two amps already.
 
  • Like
Reactions: Malm7913
#3
I do this all the time. Just run the full range driver full range (no filter) and run the sub at a point that matches well by ear. If you want, use a large electrolytic cap to high pass the full range. Something like 1000uF should be about 150Hz for 8ohm driver. Add a circa 2uF film bypass cap if you want.

I am running this flower baffle open baffle as the full range with a 6th order XKi sub woofer.

https://www.diyaudio.com/community/threads/foam-core-board-speaker-enclosures.223313/post-5809767
 
  • Like
Reactions: Malm7913
#4
Capacitance in parallel add, so typically tiny $$$ || small $$ || medium $ || big cheapie. If you increased the number of binding posts to four, you can attach the caps between two posts and one of the posts will be bypass to speaker +. This is first-order XO. Second-order XO will require an inductor between the - post and a fourth binding post, and a removable jumper between it and the + bypass post. (Some amps don't like changing speakers on-the-fly so be careful.)

Easy-to-remember first-order HPF frequency (160khz/ohm)/uF so 8ohm impedance means 20/uF khz. LPF frequency (160hz*ohm)/mH so 8ohm means 1280/mH hz. These simplified do-in-head formulae are within 1% of the textbook formulae.
 
Last edited:
  • Like
Reactions: Malm7913
#5
look the SCHALMEI SAT, perfect soundstage, small, "subsonic" filter by construction, so fullrange no filter needed,
http://www.hm-moreart.de/9.htm
 

Attachments

  • Schalmeisat1.JPG
    Schalmeisat1.JPG
    59.7 KB · Views: 72
#6
First with your scheme you have a sub + satellites. WAW usually cross a bit higher.

Only 1 woofer? 2 are better.

The simpliest HP filter is a single capacitor in conjunction with the input R of your HF amplifier will create a first order roll-off. Faster really requires some active circuitry. A passive filter with a big-*** cap brings lots of issues, is problematic due to the increase of impedance at resonance, and is not that transparent. A tiny cap built into the connection cable is much less $$ and as transparent as possible.

What FR in what box?

dave
 
  • Like
Reactions: Sub Sonic
#11
xrk971 said:
Just run the full range driver full range (no filter) and run the sub at a point that matches well by ear. If you want, use a large electrolytic cap to high pass the full range. Something like 1000uF should be about 150Hz for 8ohm driver. Add a circa 2uF film bypass cap if you want.
Click to expand...
I'm running my full range speakers and sub exactly like this and it sounds great. The full range speakers on their own actually gives satisfying bass for music, but I would like to try a (simplest) HPF (electrolytic cap) on them to relieve them from bass duty lower than say 80Hz.

But this formula confuses me. Using only an electrolytic cap as high pass for 80Hz gives 250uF. While X suggested a 1000uF for 150Hz, using this formula (0.15 khz = 20/uF khz) gives 133uF. Does not add up.

What size uF cap to try for 80Hz HPF?
 
#12
xrk971 said:
I do this all the time. Just run the full range driver full range (no filter) and run the sub at a point that matches well by ear. If you want, use a large electrolytic cap to high pass the full range. Something like 1000uF should be about 150Hz for 8ohm driver. Add a circa 2uF film bypass cap if you want.

I am running this flower baffle open baffle as the full range with a 6th order XKi sub woofer.

https://www.diyaudio.com/community/threads/foam-core-board-speaker-enclosures.223313/post-5809767
Click to expand...
Thank you.

An active crossover is not something I want for this particular build.

And running the single driver fullrange is basically what I want to avoid. Relieving the single driver of the lowest bass is the goal here🙂
 
#13
planet10 said:
First with your scheme you have a sub + satellites. WAW usually cross a bit higher.

Only 1 woofer? 2 are better.

The simpliest HP filter is a single capacitor in conjunction with the input R of your HF amplifier will create a first order roll-off. Faster really requires some active circuitry. A passive filter with a big-*** cap brings lots of issues, is problematic due to the increase of impedance at resonance, and is not that transparent. A tiny cap built into the connection cable is much less $$ and as transparent as possible.

What FR in what box?

dave
Click to expand...
Thanks Dave,

I have something like this, I think? The FMOD from Harrison Labs. It works but you need a pre and a power amp setup, which I have, but some of my favorite amps are integrated....

And yes, I only have one sub at the moment.
 
#18
twocents said:
I'm running my full range speakers and sub exactly like this and it sounds great. The full range speakers on their own actually gives satisfying bass for music, but I would like to try a (simplest) HPF (electrolytic cap) on them to relieve them from bass duty lower than say 80Hz.

But this formula confuses me. Using only an electrolytic cap as high pass for 80Hz gives 250uF. While X suggested a 1000uF for 150Hz, using this formula (0.15 khz = 20/uF khz) gives 133uF. Does not add up.

What size uF cap to try for 80Hz HPF?
Click to expand...
My math may be off.

Let’s see…

Fc= 1/(2pi RC), solving for C we get

C = 1/(2pi R Fc) = 1/(6.28 x 8ohm x 150 Hz)
= 132 uF

Sorry, my bad earlier.
 
You must log in or register to reply here.
Top Bottom