High Pass Filter on PSW505?

dauber65

Hi guys, my first post here. I typically post on AVSforums, but I have a very specific polk question.
I'll give you my system run down.
90% HT/gaming. 10% music.
Very very large open basement. (well over 10,000 cubic feet. Maybe close to 14K depending on measurment). One section of this large space being used as HT. (maybe 15X25 area) but the rest is still open.
Polk Monitor 60 Front, CS10 center, Polk Monitor 50 surround, Polk TSI100 rears. Dual PSW505's. Aydessey tuned, reset all speakers to 80Hz crossover and Sub Low pass filter set to 80Hz at the receiver.
I use an Onkyo SR-TX606 receiver. I use the sub line out to the subs.
My question is on the PSW505. Does this sub amp have any built in HIGH pass filter built in. The crossover on the outside is a Low pass, and I do not even use it since I use the LFE input. My question regards the internal circuit for the amp to protect driving too much low frequency into the sub (1-30Hz). I have read this sub is tuned around 34Hz, so driving too much below 30Hz just drives the cone and since its vented, nothing protects it from overdriving.
Since many of you own the PSW505, do you know if there are any safeguards to protect the sub. Mechanical, High pass cross over, other tech I'm unaware of?

dauber65

Another question for fun. Anyone know the tuning frequency for this from Polk for this sub (PSW505) and the PSW10 (I own both).

Erik Tracy

I do not believe there is any high pass circuitry on the PSW505. Only the low pass and the upper freq that the sub will 'see'.

If you are using the LFE input, then the low pass circuitry and the upper frequency passed on to the PSW505 is totally determined by the AVR's setting.

High Pass would be for what frequencies would be 'passed on' to your other speakers - the lower cross over frequency being where the lowest frequency and up would go on to your other speakers - not the sub.

dauber65

Thanks Erik. Most people on the avsforum seem to think all "consumer" subs would have a built in high pass filter somewhere around the tuning frequency of the sub (likely not listed anywhere on the sub fact sheet). Others were not so convinced. They seemed to think most "consumer" vented/ported subs would have some filter to keep the really really low and loud material from damaging the cone/driver from being over driven unlike a sealed sub, where there is an air cushion behind the cone to slow the cone travel speed down. I am unaware of any way to set a high pass filter in my subwoofer feed on my onkyo receiver (obviously I can on all the other channels). Not sure if its an option in higher end models or not.

I am aware of the difference of a low and high pass filter even though the names get me turned around sometimes.
I do use my receiver to control the lowpass subwoofer channel which I set at 80Hz.
I was just trying to figure out if the subwoofer driver "sees" (aka the amp outputs with no filtering) 1-79Hz. Or it has some built in electric filtering to start reducing the power of the sub at a lower Hz to keep from damaging itself.
This came up as a topic for me on avsforum because my dual 505's seem to reproduce bass perfectly fine 99% of the time, but when a big bass sequence like in the THX "amazing life" demo when the mushrooms flop open the subs can really make an awful distorted noise. Obviously I could turn the sub down, but I really like the way it sounds in the 30 and up range. Just not the deep loud impact of material below 30, especially below 20. Here is another example of a clip that puts the subs into distortion for me. "Life of Echo"

tonyb

Not exactly sure what your asking, protection for a sub ? The best protection is careful control of the volume dial on the receiver and sub.

From the info you've posted, your happy with the subs 99% of the time. To get to 100% you may need better subs. You have an extremely large area, open, that even both 505 subs will have a hard time pressurizing. Even the speakers are pretty small for that size of a room. I would imagine your turning up the volume to fill the space, which neither the speakers or subs seem capable of doing imho.

Aside from the size of the room, placement of the subs, you've probably hit their peak as far as performance goes. Trying to push them further is only going to damage the subs.

dauber65

TonyB, you are 100% correct. I know the 505's are great subs for most applications. I'm asking A LOT from them for my application.
Long story short, I'm trying to figure out if these would be worth investing in.
http://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-30-hz-high-pass-rca--266-248
They basically go in-line in your LFE feed to your sub. This 30Hz set, starts blocking content at 30Hz. In theory at 15Hz it would cut 12 db out of the feed. (because it blocks 12db per octave and an octave is double or 1/2 of your starting point). Since it starts at 30Hz, it cuts 12db out by 15HZ and 24db by 7.5Hz.
Just a way to protect a subwoofer from attempting to play material it is not designed to play. In theory you might be able to turn up the subwoofer for the other Hz range if the low range below 30Hz is what is holding back. Which was my thought. Increase the gain, insert these to protect driver at low freqency. I am just trying to figure out if the Bash plate already has some form of a limiter designed by Polk to protect the sub from over driving. I do not think adding these would hurt the sub any. Just might double the signal being removed at a certain point. Just added protection at the risk of having no bass below 30Hz. Which might be ok to me since I run bass shakers.

tonyb

I don't believe the plate amp has any protective measures against over driving the sub. Again, it's the volume dial on the receiver and sub that will dictate. Never used those in-line things from Parts express so can't comment on their usefulness. I'm more of a right tool for the right job type.

It might help some if you could build a false wall behind you so the subs aren't trying to pressurize the whole basement. Just a thought. If your subs are bottoming out though, you need to turn it down or risk doing some damage.

Bass shakers too....lol. Grab some SVS subs and you might think twice about the bass shakers and handling of those lower bass notes.

dauber65

The right tool would be a bigger sub. I want to do a DIY 18 Stereo Integrity build and move the two polks to the front sound stage and just turn them down as filler. But for the time being I'm just tuning the 505's the best I can. I have them about 1/2 gain with the AVR set to -3db. So its not like I'm getting crazy with them really. Like I said, they are normally just fine. It is just the tracks below 20Hz that I would like to just cut out/lower. These filters are supposed to do that. Here is another track which puts pain on the sub. This is the THX "amazing Life" track. Material below 10Hz.

tonyb

Well, try it then. Price isn't too bad either. That's the only way to find out if they'll work for your application.

To me though, it's a band aid to a bigger issue. The 505's weren't designed to go that deep in that big a room anyway. I don't understand why your playing tracks with that low of bass when you know the subs can't handle it. Plus whats the point too if your going to cut out that bottom end with those filters ? What am I missing here ? Wouldn't the simple solution be to not play those ultra deep tracks on gear that can't handle it ? Just curious is all, no offense meant, just don't understand what your trying to do here. Everything has limits, you've found yours.

Best practice to protect the subs until you can replace them is to not play those deep tracks and turn the volume dial down a notch or 2. I have a feeling once you install those inline filters, your going to crank the volume even more. Just my .02

dauber65

So I should just not watch movies then? The "earth to echo" was a movie i had just rented. This happens 1% of the time or less from content below 20hz. The 505 according to testing is tuned around 34hz. According to avsform members; playing a sub below tuned frequency really does not do much other than move the cone without much audable noise. And all frequency below 20hz is felt, not heard. So if I were willing to let some of that bandwidth go before 20hz using a filter that the 505 struggles with anyway, that would free up power for the sub amp to use at frequency levels that are audable from 20 to 80hz. And yes in the mean time, I'm turning the dB down on the sub woofer channel to keep from over driving the subs.