Low pass vs. high pass filters

**Tito Jackson** · April 11th, 2003 07:10

I''m soooooo confused! I''ve done searches on this and tried to find the answer but I just keep getting more screwed up.
My sub is a polk psw350. Literature says it has a variable low pass filter but no high pass that I can tell.
If I run speaker level to the sub and then out to the sats, will the low pass filter stip the bass from the signal before it hits the satellites or not?

Could someone please explain the difference to me in "idiots" terms?

**rmyAddison** · April 11th, 2003 13:23

Tito,

My DefTech''s would strip the low and pass the signal, but I have no idea with Polk. That''s a Polk question, lots of different ways to build and configure speakers and subs. Unless you find an owner here, contact the manufacturer.

**rkkwan** · April 11th, 2003 14:46

Rich is correct. But from what I''ve looked into, many subs that don''t have a variable high-pass filter do have one a set one at 80Hz. But do check with the manufacturer, as they are many exceptions.

**BigSur** · April 13th, 2003 00:17

Tito,

I am having the same problem. I recently bought a pair of higher end, albeit smaller speakers (ATC SCM7''s). Because their frequency response only extends down to about 60Hz, I started thinking maybe I could hook up my subwoofer (Paradigm PDR8) or perhaps even buy another one to get full range on each channel. My subwoofer does not have a high pass filter (it doesn''t even have speaker out connections) so I started looking for an aftermarket filter. Cruthchfield sells several for the auto market, but they are cheap enough that I might buy one to see how it works.

I looked on the Polk web site for information about your subwoofer. From what I can tell from the web site, your model (PSW 350) does have speaker out connections, but the web site doesn''t mention it having a high pass filter. The specifications on the next model up (PSW 450) does refer to its high pass filter.

Perhaps Ray is correct and the PSW 350 has a built-in high pass filter. This would make sense or why else would it have the speaker out connections?

Let me know if you find out anything more.

Mike

TV · April 13th, 2003 00:45

Tito,

*lowpass* literally means the filter allows the "lows" to "pass"---filtering out the highs. So in this case, the lowpass filter is allowing the lows to pass thru for the subwoofer to reproduce.(keeping the highs out).

What type of receiver are you using? If it is a DD(dolby digital) unit, you should be able to set the speakers to SMALL, letting the bass management of the DD decoder highpass the speakers somewhere in the 80-100hz range(this my also be user adjustable).

Tom V.
SVS

**Tito Jackson** · April 13th, 2003 01:27

Thanks for the replies guys. What I'm trying to do is to have a sub on each of the front channels so that I can configure my setup according to the threads from rmyaddison and soundhound. Trying to accomplish stereo bass.
I am familiar with the psw450 having a high pass filter, it talks about it in the literature for my 350, but am unsure about the presence of one on my sub.
I am using a DD receiver, with preouts, and I am currently using the bass management on the receiver to separate the frequencies being played by the different speakers.Sub is currently hooked up to the sub out RCA jack. Just trying to demo another setup.
Gonna have to send an e-mail to Polk and see what they have to say
The sub does have speaker level ins and outs though, and this setup is one that is recommended in the owners manuel. Maybe I'll just try it and keep the levels really low to see what happens.
Thanks.

**rkkwan** · April 13th, 2003 01:41

Tito - You can try to find out yourself if you have some low-bass material or an AVIA test disc. Hook the front speakers via speaker level, i.e. through the sub, and then turn the volume of the sub to the lowest possible setting. If there''s a high-pass filter, your response under 80Hz will be way down. If you still get a full-range signal from your mains, then you don''t have a high-pass filter in the sub.

**rmyAddison** · April 13th, 2003 12:38

Tito,

Using a receiver, to get the stereo configuration, unless you have left and right LFE''s (I don''t) you have to set the mains to large and select no sub in the setup menu.

If you mains are full range, they get the amplified L/R signal and the subs get the L/R pre-out signal which their xovers strip out the mid/highs.

If your mains are not full range, you still need to set them large in the setup to get the .1 and low signals from any speakers set to small, but you put the subs in line from the amplified L/R out, to strip the bass before it reaches the mains.

Sounds like the last is what your trying. Ray''s idea is good, send speaker wire from the amplified L/R mains to the subs then to the main speakers. Turn the sub volume all the way off. If you have normal levels in your mains, but no lows you''re in business. Turn up the subs to add the low end.

Good luck