High pass filtering the main speakers

Ported speakers should be filtered below the tuning frequency. They don't produce sound below that and the woofer has no loading so can easily be damaged and is moving a very large amount that will cause doppler distortion.

McIntosh MC901

"Removing the demands of reproducing bass frequencies from the amplifier seems like a really good thing to do. Yet, not many amp manufacturers seem to support it. Why?"

rolleyes Even the cheapest AVR has high pass filtering.

@Paul: Do your findings here also apply to when a set-up is run fully actively with separate components, i.e. where amps, DSP/electronic cross-over and DAC(s) aren't bundled into the speaker? Myself I use such an active-as-separates system with no passive filters involved, yet it's still looking like a "normal" passive set-up with amps and a DAC on a rack, the difference though here being that it also houses a digital cross-over (Xilica XP3060) and extra amps to feed the different driver segments of the main speakers + two subs.

In principle I guess you'd still prefer for the main speakers to be run full-range, be it an active or passive set-up, but few appear to be using an active system where everything isn't bundled into one package, and from that approach (as separates) you're free to apply filter settings without the intervention and complexity of physical components between the amp(s) and drivers. Yes, there are still phase shifts involved with a digital cross-over, but still.

In my case the mains are high-passed at ~85Hz (36dB/octave L-R), but the basses here (dual 15") run all the up to ~800Hz, and so relieving them from the central to lower bass makes quite a difference being they are run all the way up into the central midrange. The HP filter on the mains here is about added headroom and a cleaner midrange, but also crossing over to the subs in the 80-100Hz region is about perfecting the "energy coherence" here. My system is both for music and movies, but all the dialing-in of the filter is made around music.

Sorry for the lengthy post.

I’ve been living this for 6 months, going back and forth between different configurations of running my mains (Tekton Pendragons) and subs (2 x 2x12” Rhythmiks). I have a K231 active crossover and have tried every variation from 60hz to 100hz. Paul is right in my experience. Any sq gain in the mains is minor compared to the loss in coherence and micro detail from bringing in another component. I changed it back to full range with the subs cut off low (55hz) this morning, and had that moment again of knowing immediately that it just sounds right, more musical, and more coherent. I use REW and have spent hours dialing in the best of each config, and the crossover helps get the smoothest response. But my ears tell me each time that some of realism is drained. I feel like I’m wasting these great subs by cutting them so low. But again, once I listen with my heart, it’s clear which config always wins, just as Paul said. I’m posting this because I doubted Paul when I heard this before in past videos, but today I feel like he’s totally right on this, and it’s time to move my crossover back to my studio system and keep my mains full range from now on.

More subs!!!

I love the videos Paul and they are very informative! However if I don't high pass my mains, my bass frequency response is all over the place because of phasing issues with the mains and subs trying to play the same notes from different locations. The speakers are about 4 feet from the front wall so I get an incredible soundstage, but this causes +/- 10db variations in the bass response. The only way I can fix this is to roll them off and let the subs do the bass. . I am using a Denon X7200W and love the IDEA of listening to music in "Pure Direct" to remove processing, but the wonky bass response it creates sounds worse than listening in Stereo with the mains high passed.

I high passed my live subs even. The band pass box and speakers I chose could only handle the power I used if I used 24db roll off at 34Hz. That's for live. At home I don't. My mono rig uses no filtering active or passive. It is only 25 watts RMS and I barely push 7watts ever. I only use it for listening to old mono recordings from back when most people had no more than a 3 watt max system. Some of those old recordings were engineered with that in mind. On some recordings I actually add a bit of distortion to make it sound "right".

There are benefits to band limiting the range of frequencies the main speakers are subject to, especially if the woofers are also tasked with carrying a lot of the midrange. The problem with speakers is that they are quite non-linear at their extremes of travel, and at substantial excursions they create quite a lot of harmonics as the surround and spider are not as linear as, say, a metal spring. In short, if you push a speaker with an increasing amplitude sine wave, you will see it start generating harmonics whos amplitude and range of frequencies increases with the volume. The speaker can (and will) also generate intermodulation distortion as well since the non-linear action of the woofer allows higher frequencies to be modulated by the lower ones. Using a sub and limiting the bass to (and thus excursion of) the woofers in the main speakers can help quite a bit with linearity at higher volumes with two-way speakers. Multi-driver speakers with a woofer that only has to carry low frequencies wont benefit much from it, however. As far as the amp goes, it will help reduce heating and power requirements, but I would not do it unless the amplifier does not specifically have enough headroom to drive the main speakers at the desired volume level. The only other reason I would use it is if there is objectionable interactions between the main speakers and subwoofer. Altering the response of both as well as phase adjustments can reduce or eliminate the interactions and give a much smoother transition between the two. With that said, the system next to me has just that: A digital EQ that band-limits the main tower speakers below 125 Hz and flips the phase of the subwoofer. It was the only way to make them actually work seamlessly together.

Coming from car audio, it’s borderline impossible to run the door speakers full range and get any appreciable volume from them without severe distortion. But the car is an extremely noisy place, and the woofers aren’t in a specific enclosure. In home audio, if you have enough volume while running the towers/bookshelves full range, why would you not?

How are the speakers not working as hard if there’s no highpass?

Paul delivers a very confusing ( Yes & No ) answer to a complex issue that he should have gone into more technically. Yes, there is a phase problem, or used to be, at the crossover frequency. But not really any more. The sub should handle the two lover octives ( 20 -> 40, 40 -> 80 ). At the 80Hz crossover point you should be using at least a 24db/octive filter. That used to be tough to do. Not anymore with DSP. Sure some phase errors from 79Hz to 81Hz. So what.

Dang, I listened to him and now my tweeters are burned out! 🤬

I use ls3/5a speakers trough Janis subwoofer crossover-amplifier. The main speakers sound better when crossed at 100 Hz. I think it’s because lower distortion than when they are used full range. The active crossover does make its affect on the sound, but the affection level is rather small.

Home theater improved a lot from not using high pass filtering with some acoustic corner panals

High pass filtering or not really depends alot on the speaker, sub and room.
With fullrange floor speakers I never filter them. With small speakers then It might happen in some cases.
In my combined stereo/cinema system I have my front as "large" (full range and connected to my combined power amp/stereo (dual mono) amp) and the center and surrounds are set as "small" and high passed at 40Hz (They really don't go any deeper anyway) and my sub is low passed at about 60 - 65Hz. That was the best way to set it for my system.
And of course: I NEVER play music in more than 2 channels! Unless it's a concert with surround sound.. That's a different story.

Shoutout to the MiniDSP 2x4 HD (~$200). Grab that and a $75 calibrated mic and you’re off to the races experimenting with all of this along with measuring your room’s effect on your setup and potentially improving it in Room EQ Wizard (free software).

Doing high filter to main speaker because we have subwoofer is logical because most of setup bass of the tower don't melt well with subwoofer, so adding a high pass filter at the subwoofer cutoff would be good. I do it but in digital domain, for the same reason Paul said that is bad for high pass on speaker crossover level (phase shift...). For home theater, ya of course today's receiver handle the cutoff easy and we don't have to bother but in stereo, in audiophile world it's not the same reality.

I have the smaller irs v cousins, you won't part me from them aslong as I live

Speakers are always a comprise , using active low end is always a improvement. Systems such as your irs v, rs1b, irs beta or the higher end genesis speaker .

Do it too, your irs has a servo controlled low end (it's active low end you need a amp on each tower)

You totally contradict yourself. Even your new irs killers +bold statement+ have a dsp ran set of woofers. Why do that?! If it's so great why didn't you guys design it just being passive ..

Active crossovers are almost always superior to the passive shit you find in most high end speakers. Makes no sense ..

Gosh disappointed with this video

DSP can correct phase shifting problems. Right?

Interesting this came up. i just did this with my JBL towers which are good down to 38hz. i crossed them over at 80hz (THX) and raised the sub up to 120hz. with a little EQ. in the speakers and sub with roll off, it's blending quite nicely. I have better sub and mid bass and it really opened up the Towers to have more air. Like Paul said it all matters on your amp. but with my AVR it works.

One application for High-Pass filtering that Paul didn't address is using a High-pass filter set at or just below the lowest frequency response limit of your mains. For instance, high pass filtering at 40hz for mains that have a range of 45hz - 20khz. This blocks the amp sending signals to the speakers which they cannot reproduce. One benefit it that the amp consumes slightly less power, and I've heard it can reduce strain on the woofers. However, I would love to hear comments from more someone educated on the subject.

I had Klipsch Epic series CF1'S even though had plenty bass and huge cabinets....I ran them of highpass of powered sub and sounded even better !!! Depends on speakers you're running off crossover how it sounds. It was at 80 hz

I'm high passing at 80 Hz into a pair of Magnepan LRSs. It sounds good. Why not let the sub reach up a bit if it does a good job, possibly better than the main speakers would do at those same frequencies. In my case, I think I'm getting a bit better sound. But the improvement is subtle, and subtle improvements are often imagined improvements (so who knows for sure). However, one additional thing I like about crossing over at 80 Hz is that I can hear the sub better when I'm adjusting it to blend with the main speakers, so the process is usually easier and quicker. In a different situation, not high passing at all and trying to blend a sub with speakers that may get down to 40 Hz to 45 Hz, I have to listen to a lot of music to try to get the blend right, and I'm never sure about it.

wow man talk about some tower speakers you have them behind you.... any tyme you want to give them up im willing to take them i have the bose 201 series III i could upgrade cant afford on disability...

Running full range speakers with the subwoofer crossover set to where the speakers roll off naturally. It's the way audiophiles have been doing it since the beginning and it sounds the best.

What about comb filtering on those tweeters in your back?

it depends! in a problematic room a subwoofer with EQ can better handle modes - if I just switch from 80 Hz to 60 Hz the room wouldn't work and I have not the place for add more absorbers

and then there are the neighbours

having the subwoofer playing everything below 80 Hz near the sweet spot in practice here means I can turn up the volume and have bass in the middle of the night

even my kitchen don't have bass and there is no door between

when I play the main speakers full range the whole house starts to live

Great information, very thorough. Thank you!

Love this video

With a pair of bookshelf speakers that sound nice at low volume levels but get midrange-through-high-bass muddy around 60-80Hz at higher volume, the HPF totally changed the character of these speakers. Without all of the low frequency clutter in the mids, the sweetness of the music really opened up. If I was adding a sub to a full-range speaker that handled the full range at louder levels better, I wouldn't use an HPF necessarily. But in the setup I have, the Sub's HPF has been most welcome.

Depends on the speakers, I suppose.

If one has little teeny-weeny on-wall Home Theater speakers, I suppose they (a) would not reproduce bass very well and (b) would be harmed by high levels of it that they would effectively dissipate mostly as heat, eventually damaging themselves. Bass management and subwoofer(s) are a must in such circumstances.

As the other extreme is a large, full-range speaker. No need to keep bass out of it.

The devil is in the middle.

I have a pair of BG Radia 520 mains, a 220 center, and four 420 surround speakers. All are rated for 80Hz to 20 kHz in terms of "flatness" and have modest 5-1/2 "bass" drivers (typically two). Should I run them full-range, and use a sub for LFE only?

Audio below 80 Hz is largely non-directional, so bass-managing it to the sub(s) seems to make sense, but such crossovers are not brick walls. If a crossover is 3 dB down at 80 Hz that is still a fair amount of signal that it is removing from between 80 and, say, 160 Hz, that IS directional.

For music, my front speakers are EACH externally crossed over to a 12" Rythmik Audio Audio subwoofer COLOCATED with them. For movies, Left, Center, and Right signals are bass managed with LFE to the same pair of subwoofers (I use an Emotiva XSP-1 for this).

The surround speakers are treated differently. They are run full-range, with only audio below 25 Hz bass-managed to the front sub(s) (And whoever made a movie mix like that would be an idiot). However, each pair (left and right surround and back surround) is augmented with an old Klipsch 12" ported sub to fill in bass in the 25 to 80 Hz range.

I have no problem with driving my speakers full range for music, but what about those huge movie soundtracks and special effects? Having that 20Hz and below signal going to a speaker that can only do 50Hz scares me. Simple solution would be getting more versatile amp that has those ”big, medium, small” speaker setiings and a Sub out, but I can’t afford a deacent one right now and I like my current amp. Any suggestions?

Paul, are you also implying that the reduced Doppler / IM distortion due to high passing isn't that much of a benefit in practice? After all most popele don't have five-way speakers.

Coming to this way after the video dropped but there is another consideration. I don’t want my small speakers to try to reproduce the low bass frequencies. I am going to build my own filters to test (they’re not complicated) and see how it affects the sound. My theory is that by cutting off the midwoofer at 60-80 hz you free it from having to try to reproduce the low frequencies which should allow it to play the remaining frequencies louder without damaging the driver. There may be some phase issues with the sub but those issues already exist. We’ll see how well it works.

Paul, if that is your opinion then fine, but why do (hi fi) powered speakers use more powerful built-in class d amps for bass and less powerful built-in class d amps for mids and tweeters?

This is likely out of scope of the video, but are there any examples of where a speaker designer might/would use a HPF to extend a mid-bass woofer's low freq range? I noticed in Basta, you can manipulate the capacitance & the inductance to extend low frequencies in simulation. Additionally, you could use a 4th order HPF to extend the low freq range further than on a 2nd order HPF since you're able to manipulate cone extension & impedance as well. I understand this adds more circuitry than necessary typically, but I was curious if essentially forcing the woofer to play lower freqs via a HPF has ever been done & what potential trade offs that would have if possible.

When I did a frequency sweep on my main speakers (having a 1" tweeter and a 10" woofer) I found that there was little output below 40 Hz. So there was little need for a high-pass filter since the woofer was doing it for free! Of course, low-pass filters are necessary for subwoofers since they would beam and distort at higher frequencies.

That's really helpful, thanks!

Sorry Paul, but I’ve gotta disagree on this one. Many modern woofers aren’t designed to be playing the first 2 octaves. They exhibit ringing and massive distortion in the midrange while contending with low frequencies. Many manufacturers know you need a sub to play the first octave anyway, so why add mass to the woofer? I’m sure your tower speakers at many thousands of dollars don’t have that problem, but your average “prosumer” stuff does and the cheap stuff definitely does. My bookshelf speakers are rated at 40W with a filter. Without it, they can only handle 3W! This is like saying a tweeter doesn’t need a high-pass filter. Bottom line is if the driver isn’t rated for it then don’t do it.

Using a high pass filter when you have small satellite speakers isn't advantageous?

My system is day and night better with the mains high passed at 60Hz

Wow. Cant believe he thinks there isnt a benefit to cutting off anything below 60hz going to your mains. In a 2.2 stereo system especially if your using bookshelf speakers with 6 inch and smaller drivers

a tower speaker(or whatever) def play better midbass when the subbass is removed

It depends on the speakers…. Most towers aren’t capable of producing very low bass frequencies, it’s even in the design knowing most people that buy these speakers are going to add at least one subwoofer.

A 10nF silver mica cap inline with my tube amps gave me a 6dB high pass filter near 60hz in a tube/solid state bi-amp configuration. It made a wonderful improvement in the lower vocal region and overall clarity, allowing the solid state amp to handle the woofers and subwoofer in the lower regions, and tubes to shine in the lower mids to treble range. Recommended in my case...YMMV.

hi passing the smaller cones and letting the subs do anything below 90 or so is great for 2 way speakers - it opens out all the mids and transients

doesnt do as much for 3 way

If your amp can't drive higher frequencies, you don't need a high-pass filter. You need a more powerful amp.

The premise of the question is wrong. The purpose of a high-pass filter is to reduce unnecessary (i.e., inaudible) cone movement in the frequencies the cone is too small to reproduce effectively.

Eliminating unnecessary cone movement at low frequencies reduces intermodulation distortion in the higher frequencies the loudspeaker can actually produce. To reduce inaudible cone movement and its associated intermodulation distortion you need a high-pass filter tailored to each speaker/amp combination.

For example, my McIntosh pre-amp has a switchable high-pass filter that rolls off bass starting at 50 Hz. That's lower than the 3dB down point of my sealed box speakers. Everything should be fine, right?

Nope.

Because the speakers roll off at only 6 dB per octave, there is still a fair amount of music below the 3dB down point. The 50 Hz high-pass filter in the preamp noticeably cuts out the lowest frequencies of the bass guitar (41 Hz and above). At the same time, the high-pass filter increases the clarity of all other frequencies because the cone moves much less. So it's a tradeoff.

The solution is to build a second- or third-order high-pass filter to put between the pre-am and amp. Done right, this will cut out the bottom octave and leave the bass guitar alone while also reducing the intermodulation distortion (that is, increasing the clarity) in the higher frequencies.




That's what a high-pass filter is really for.