Speaker High pass Low pass filter for a sub ?

[LouB]

I switched out an AVR 5.1 system for a 2 channel system. Now have a Marantz model 40 which has a sub output with low pass filter options of, 40 Hz / 60 Hz / 80 Hz / 100 Hz / 120 Hz (Default: 80 Hz). But since there is no filter for the mains won't the mains still get the full range all the down to 40Hz ? If that's the case than it seems that adding a sub would give me more bass but with mains still pumping out the low's I may end up with a messy bass response.
Should you have a filter to stop the low freq. from the mains when adding a sub ?
Thanks

 

[ZolaIII]

If there is no high pass filter mains will output all that they can regarding lows. It's not a huge deal but at least I hope it has variable subwoofer output or you are in trouble with it. High pass is good to get the load of the main speakers that is troubling for them (lows) and there for decrease THD and improve clarity and/or enable them to play louder. Unfortunately you can't implement high pass filter without loosing all additional functionality (it becomes just a power amplifier and nothing more as it's dependent on analog or digital input to it with high pass filter implemented on signal). Don't worry it's not that hard to cross the sub to full range output of main speakers and it won't be like you get a huge amount of lows all of the sudden (remember 2x the signal straight is +3 dB and that is not a problem to shave off). You just need to measure output of mains first and then match and cross them.
Considering this I am tempted to buy a A-S700 Yamaha (solo power amplifier only) which I discovered old stock hire where I live and for a bargaining price (tho black one only but brand new and with seller warenty) and pack out my old R-N.

 

[sigbergaudio]

Ideally yes, you should have a high pass (why on earth don't these amplifier manufacturers implement that as well?).

So now that you don't, you need to run the low pass at a very low frequency, so probably 40-60hz depending on what kind of speakers you have.

 

[LouB]

Thanks, kinda what I thought. The mains are Paradigm SE3 https://www.paradigm.com/en/floorstanding/se-3
Which have 4 drivers I think it's 2 - 5 1/2" for bass, 1-5 1/2 for mids & 1 tweeter. For music they have very good bass even at loud volume, I like the bass response from these better than when I had a sub going.
Not a bass freak & My thought on adding back the sub would be for Movies/TV. The Model 40 has an HDMI ARC input & I kinda miss the rumble of movie sound tracks & special effects I had going with a 12" sub.
Thanks for replies, it appears the best way to integrate a sub would be with a Hi pass filter & there is no simple/after market "filter" I could use with my amp. So maybe for now I'll put the sub back & just turn it down when listening to music.

 

[DVDdoug]

Are you sure there's no high-pass for the main speakers? It seems strange to have half of a crossover! Try switching between 40 & 120Hz or "off" and 120Hz without a sub attached to see if anything changes.

 

[ZolaIII]

@LouB it really isn't that hard to implement sub without a high pass on mains. You do need to have measurement microphone so you can measure output of mains (using REW) and then adjust property low pass for sub and that's about it. Of course you do need to PEQ them together afterwards (with PEQ that REW generates based on what you told him to do) and iron out response (± dB) and towards your liking (hause curve). Some people even like it more without high pass filter all do we can't discard benefits it brings in.

Edit: I am not sure what Marantz 40 does white it's crossover so key word would be measure it (output of mains at different crossover points).

 

[LouB]

Are you sure there's no high-pass for the main speakers? It seems strange to have half of a crossover! Try switching between 40 & 120Hz or "off" and 120Hz without a sub attached to see if anything changes.

Nope, not sure at all. Just no mention of it in the manual, good idea !
I tried it with a few different tunes & there is no noticable difference weather Low pass is 40hz or 120hz when just using the mains no sub plugged in. So maybe I've got 1/2 a crossover !
Thanks

 

[sigbergaudio]

There are unfortunately many amplifiers that are like this (lowpass but no highpass).

 

[antcollinet]

There are unfortunately many amplifiers that are like this (lowpass but no highpass).

It's bizarre - this is completely the wrong way around based on the fact most subs already have a built in lowpass.

 

[barrows]

Would like to re-vive this topic a bit. My main speakers, Focus Audio Signature 888s have pretty good bass extension, but are two ways. I have a JL Audio 112e single sub with them. The single sub is OK (as opposed to two) because I low pass the sub ~40 Hz, and at these low frequencies the sound from the sub is not perceived as directional. I am experimenting with high passing the input of my power amp (a DIY Purifi build) to relieve the amp/main speakers of just very low bass. Differential input impedance on the amp is 97K, and I am running .047 µF caps on the input to the amp, for a -3 dB point of 36 Hz. this stops the mid woofers in the main speakers from having to make huge excursions, which should reduce distortion in the main speakers, and allow them better handle upper bass and midrange frequencies. My DAC has separately driven XLR and RCA outputs, so I run the Sub from RCAs. This approach seems to work well, and my measurements show I can get pretty smooth response by tweaking just my sub high pass filter and level, at least at the listening position. I feel like my main speakers sound a little better, and it certainly is a bit of a relief to not see the drivers having to make huge excursions when playing at high levels.
I am an audiophile, and do believe that one needs high quality capacitors for this, as of course I have added series caps to the full range signal. Good quality film caps should be used, but for only .047 µF caps these are not too expensive.

 

[Gringoaudio1]

If anywhere in the menus in your receiver there is an option to choose your Main speakers as Large or Small that is a high pass filter. The speakers in the Small setting are high passed. At what frequency is a good question. I have no control of the frequency in my older Marantz 7005 receiver.

 

[Gary_G]

My Parasound P6 has both a mains high pass and subwoofer low pass filter option.

I am try different options with crossover set in the sub or in the p6, as well as the mains being full or high passed at the crossover freq.

 

[LouB]

Would like to re-vive this topic a bit. My main speakers, Focus Audio Signature 888s have pretty good bass extension, but are two ways. I have a JL Audio 112e single sub with them. The single sub is OK (as opposed to two) because I low pass the sub ~40 Hz, and at these low frequencies the sound from the sub is not perceived as directional. I am experimenting with high passing the input of my power amp (a DIY Purifi build) to relieve the amp/main speakers of just very low bass. Differential input impedance on the amp is 97K, and I am running .047 µF caps on the input to the amp, for a -3 dB point of 36 Hz. this stops the mid woofers in the main speakers from having to make huge excursions, which should reduce distortion in the main speakers, and allow them better handle upper bass and midrange frequencies. My DAC has separately driven XLR and RCA outputs, so I run the Sub from RCAs. This approach seems to work well, and my measurements show I can get pretty smooth response by tweaking just my sub high pass filter and level, at least at the listening position. I feel like my main speakers sound a little better, and it certainly is a bit of a relief to not see the drivers having to make huge excursions when playing at high levels.
I am an audiophile, and do believe that one needs high quality capacitors for this, as of course I have added series caps to the full range signal. Good quality film caps should be used, but for only .047 µF caps these are not too expensive.

Interesting approach & it sounds like it worked. This may make no sense for many reasons I don't know, but if an amp has no high/low pass filter options for mains but it does have a sub out would it be possible to just build an external crossover for the mains just blocking out the low freq. ?

 

[barrows]

The problem with creating a high pass filter between the amplifier and the speakers, is that one would need huge capacitors to do it because of the low impedance of the speaker load. By high passing at the input of the amplifier, one is working with the much higher (94 Kohms in my case) input impedance of the amplifier, thus requiring only a very small amount of capacitance. Note that the entire signal is passing through this capacitor, so it is important to use a very good high performance capacitor for this, which would be very, very expensive in high values. This is considering a two channel audio system mostly here, for home theater of course there are many other solutions. But for hi fidelity, one wants the high pass filter to be of very high quality, otherwise it will affect the signal quality.
Aesthetix Audio makes their amplifiers with the option of ordering with a switchable high pass filter like this built in; it is too bad more companies do not offer such, as this approach is an elegant way to high pass the mains for use with a sub. For a full on external cross over, there are active options available like this:

CR-1 Active Subwoofer Crossover - Electronics - Home Audio

www.jlaudio.com

But that is an expensive and complex solution, which needs to have really good electronics to not add its own distortion/noise to the signal. The passive approach I used requires a little more knowledge, but is simple and quite elegant.