High pass filters, low pass filters, no pass filters

[LemonBurst&OrangeCrush]

Hello all.

I'm trying to put together a 2:1 set with Dali Menuets at the foot of my bed. I'm planning on getting an SVS SB1000 eventually.

But I'm a little stumped about streaming amplifiers. I thought high and low pass filters were things I'd have to learn about but it looks like a lot of the more expensive ones don't have them.

So my question is - do I go for something without a filter or opt for a Marantz M1 or something similar? I was originally going for a Marantz before I read Amir's review.

Does a filter produce space I'd be missing or does the extra cost give you more in return?

Thanks.

 

[Redacted]

For me, HP & LP are just traditional "tone controls".
I don't use them as I'm lucky with my room or I am just a deaf git. But tone controls will be useful if your speakers are pointed at your duvet.

An issue for some people is about amps that have a separate sub-out port and the amp has controls that work with it, and also if the main speakers are filtered separately or not from the sub out. But don't sweat it.....

Making some assumptions about your potential set up, I'd say:

1) Buy amp/DAC/streamer that has features you care about, but realize pre-amp out ports and/or sub-out will be useful later.
2) Buy speakers that you have read about to be OK, that are the Dalis, in your case....
3) Buy a sub that has volume and XO controls (i.e. has a built-in amp). Even better if the sub has L & R inputs that can be fed from the pre-outs on your amp, but a single mono input will do if your amp has a sub-out port (of any description with or without filters)

 

[LemonBurst&OrangeCrush]

Thanks, that makes sense. I'd lost my way in the undergrowth.

 

[Keith_W]

@Redacted HPF/LPF are NOT tone controls! You must be thinking of high shelf / low shelf filters?

Anyway, to explain: a "high pass filter (HPF)" means it lets frequencies above a certain point through, and blocks frequencies below that point. Hence, "high pass". Low pass filters (LPF) does the opposite. Your Dali Minuet has a crossover network. The tweeter will have a HPF to only allow high freqs through, and the woofer will have a LPF.

If you have a pair of bookshelf speakers and you want to add a sub:

- the sub MUST have a LPF. This is to stop them from reproducing high frequencies which you don't want a sub to do.
- whether you put a HPF before your main speakers is a separate question. Sometimes you don't need one, e.g. if your speakers don't reproduce bass. Sometimes you might wish to put a HPF in to reduce bass distortion. Sometimes (if you are very clever), you can leave your speakers full range with no HPF and use the sub to fill gaps in the low bass response.

Do you "need" to buy an amplifier with built-in HPF/LPF? Well, if you are planning to add a subwoofer, DSP is almost mandatory. The built-in HPF/LPF of an amplifier is so rudimentary that it is crude. I personally wouldn't bother with it. So personally, I would choose the dumbest amp I can get away with and implement the DSP somewhere else.

And welcome to ASR by the way!

 

[LemonBurst&OrangeCrush]

Thanks; I think I'm getting there.

 

[Redacted]

"Anyway, to explain: a "high pass filter (HPF)" means it lets frequencies above a certain point through, and blocks frequencies below that point. Hence, "high pass". Low pass filters (LPF) does the opposite."

Yup. Essentially bass & treble tone, depending on whether you think of boost or cut, and to suit the audience here...
I think the OP just needs a powered sub with built in amp/DSP, without all the gobbledygook - it's for the foot of his bed! K.I.S.S.

 

[janbth]

A Wiim Amp may serve your purpose:

WiiM Amp | Smart Streaming Amplifier for Passive Speakers

Power passive speakers with WiiM Amp. Enjoy Hi-Res streaming, HDMI ARC TV audio, Room Correction, multi-room, AirPlay & smart control.

wiimhome.com

By the way, it’s utter nonsense to say that a high or low pass filter is a tone control.

 

[MAB]

Thanks; I think I'm getting there.

Here is an example using a speaker simulation tool, VituixCAD. High-pass and low-pass are at 1kHz with 6dB/octave slope (aka 1st order).

The 3dB-down point is at 1 kHz. The woofer and tweeter response are mirrors of each other. You can see that the filter attenuation is literally 6dB/octave:

Speakers typically use steeper slopes for the filters, and also have their own rolloff (this example uses two drivers with infinite frequency response!) But I hope you can see the red traces, with the high-pass filter literally allowing the high frequencies to pass to the tweeter while filtering the low frequencies. Same for the low-pass filter applied to the woofer while attenuating the higher frequencies. The two should sum to provide a neutral response. Slopes steeper than 6dB/oct are typically used, especially when the actual measurement of the drivers is considered.

Also, the above model uses high- and low-pass filters that are similar to an active amplifier module. The equivalent of the above filters in a passive loudspeaker are a capacitor and an inductor, like this:

The response of the passive version is the same as the active, with some exceptions since passive components are not ideal (inductor DC resistance for example). In the above example they are nearly line on line.

Linkwitz has a nice page on many different filters, with some diagrams and math that may or may not be helpful.

Active Filters

 

[LemonBurst&OrangeCrush]

Thanks, that makes sense.

 

[john61ct]

AKA Crossovers between main pair and sub(s)

If you are sure you only want a single sub, the Wiim preamp / streamers are fantastic value

They include good adjustable crossover functionality as well as basic DSP to create a 2.1 system. Ultra has the most features, but then you still need separate power amps.

Wiim Amp Ultra a bit less featureful, but includes a great stereo power amp built in, plenty for your speakers, just add a powered sub.

If you want a different front end, miniDSP 2x4 HD goes between that and your power amps gives you a good crossover with lots of flexibility, including ability to go to stereo subs in future.

 

[DatSpeakerTho]

"Anyway, to explain: a "high pass filter (HPF)" means it lets frequencies above a certain point through, and blocks frequencies below that point. Hence, "high pass". Low pass filters (LPF) does the opposite."

Yup. Essentially bass & treble tone, depending on whether you think of boost or cut, and to suit the audience here...
I think the OP just needs a powered sub with built in amp/DSP, without all the gobbledygook - it's for the foot of his bed! K.I.S.S.

A HPF and LPF will not give one desirable outcomes if used a as tone controls. They are just not suitable for the task.

 

[RedPanda42]

@Redacted HPF/LPF are NOT tone controls! You must be thinking of high shelf / low shelf filters?

Anyway, to explain: a "high pass filter (HPF)" means it lets frequencies above a certain point through, and blocks frequencies below that point. Hence, "high pass". Low pass filters (LPF) does the opposite. Your Dali Minuet has a crossover network. The tweeter will have a HPF to only allow high freqs through, and the woofer will have a LPF.

If you have a pair of bookshelf speakers and you want to add a sub:

- the sub MUST have a LPF. This is to stop them from reproducing high frequencies which you don't want a sub to do.
- whether you put a HPF before your main speakers is a separate question. Sometimes you don't need one, e.g. if your speakers don't reproduce bass. Sometimes you might wish to put a HPF in to reduce bass distortion. Sometimes (if you are very clever), you can leave your speakers full range with no HPF and use the sub to fill gaps in the low bass response.

Do you "need" to buy an amplifier with built-in HPF/LPF? Well, if you are planning to add a subwoofer, DSP is almost mandatory. The built-in HPF/LPF of an amplifier is so rudimentary that it is crude. I personally wouldn't bother with it. So personally, I would choose the dumbest amp I can get away with and implement the DSP somewhere else.

And welcome to ASR by the way!

Sorry to butt in but this is a topic I am interested in. Before just a few days ago I didn't know much about high pass/low pass filters. Doing some research I found mostly positive things about it saying that you always needed to setup a crossover so the speakers weren't forced to do the low hz sounds and that would somehow make it easier for it to play the mid and high sounds it's supposed to be playing. But then yesterday I found a thread on another forum and almost everyone was saying it was a waste of time and could somehow make it sound worse which I really don't get.
Now I'm confused on how much I need to consider this. I've got a set of Polk ES15 speakers and an RSL Speedwoofer 10e coming next week. I believe the speakers can technically go down to 46hz, but is there any reason not to make a high pass filter for them with EqualizerAPO (I also am not sure what a good number would be, 60hz, 80hz, 100?) and let me subwoofer do the work below that? Are there benefits to letting the polks go all the way down and I guess setting the low pass filter on the subwoofer to 46?

I never see anyone mentioning doing a low pass filter higher than 100hz but almost every sub I look at can go up to 200. Why is 100 a cutoff point and why can subs go up twice that if no one does it?

 

[LTig]

Sorry to butt in but this is a topic I am interested in. Before just a few days ago I didn't know much about high pass/low pass filters. Doing some research I found mostly positive things about it saying that you always needed to setup a crossover so the speakers weren't forced to do the low hz sounds and that would somehow make it easier for it to play the mid and high sounds it's supposed to be playing. But then yesterday I found a thread on another forum and almost everyone was saying it was a waste of time and could somehow make it sound worse which I really don't get.

Did they explain why?

Now I'm confused on how much I need to consider this. I've got a set of Polk ES15 speakers and an RSL Speedwoofer 10e coming next week. I believe the speakers can technically go down to 46hz, but is there any reason not to make a high pass filter for them with EqualizerAPO (I also am not sure what a good number would be, 60hz, 80hz, 100?) and let me subwoofer do the work below that? Are there benefits to letting the polks go all the way down and I guess setting the low pass filter on the subwoofer to 46?

There is one constellation where not using a high pass on the LR-speakers might make sense: The LRs need to be capable to reproduce deep bass, so they act as additional subs. As we know multiple smaller subs are better to get an even bass response, so this constellation could help in a few cases. Keep in mind though that the LR-"subs" cannot be placed where they work bests like independent real subs.

I never see anyone mentioning doing a low pass filter higher than 100hz but almost every sub I look at can go up to 200. Why is 100 a cutoff point and why can subs go up twice that if no one does it?

The LF effect channel of multichannel recordings contains signals up to 120 Hz, so this is the minimum a sub must be able to handle. And if you want to use 2 subs and place them below each LR speaker you can safely use 200Hz or higher as crossover frequency without localising the sub as a separate entity.

 

[RedPanda42]

Did they explain why?

This is the exact quote of what they said.

This is the truth for most desktop 2.1 setups.

I have a set of Edifier MR5 monitors that actually have adjustable high-pass filters built in, and I went down the REW measurement rabbit hole trying to do it "properly." After measuring the speakers alone, sub alone, and then combined, I ended up turning the HPF back off.

What I found was that the low-pass setting on the sub was doing 95% of the work. The HPF on the mains made far less difference than I expected, and in some cases actually created a gap in the 60-100 Hz region where deep male vocals and bass guitar fundamentals live.

People often assume you need a perfectly matched HPF and LPF crossover to get good integration, but plenty of active monitors naturally roll off low enough that you can just run them full range and blend the sub underneath them.

That last part is what confuses me letting them roll off. All the research I had done before said the exact reason you do a HPF is so they don't have to roll off and do the work of deep bass which lets them work better at the higher frequencies.

 

[LTig]

That last part is what confuses me letting them roll off. All the research I had done before said the exact reason you do a HPF is so they don't have to roll off and do the work of deep bass which lets them work better at the higher frequencies.

As I understand it they say that you run the active main speakers in full range and set the cross over of the sub to the cut off frequency of the speaker. You can do this, but then you miss the opportunity of lower distortion and IMD in the main speaker woofer. With a proper highpass you can play louder and cleaner than without.

My active main speakers go down to 40 Hz, but I use a cross over of 100 Hz because REW showed a smaller dip around 80 Hz. Mains are high passed, of course.

 

[Chrispy]

It goes a bit beyond just a pair of filters for me. I like adjustability of delay as well. A simple pre-out with no filter on an integrated amp I see no point in having unless you have some external bass management. Fortunately more 2ch integrated amps are getting better bass management these days. An avr can do well as well as provide future multich audio options.

 

[john61ct]

Depends on the speakers.

Small bookshelf / satellite are super limited in the low end, so with other speakers/sub(z) to handle that they can play their mid + treble cleaner at high SPL by simply not being fed low bass.

Having overlap can be helpful for LF room resonances, but can also be more of a challenge without automated bass management solutions

which gets expensive.

Starting simple with 2.1 and Wiim Ultra or WAU gives you the ability to test out different scenarios with your speakers & unique room start to climb the learning curve,

wait until you know you want to go down the rabbit hole before getting more complicated

 

[Audionaut]

aka 1st order

aka Star Wars Filter

 

[Keith_W]

Sorry to butt in but this is a topic I am interested in. Before just a few days ago I didn't know much about high pass/low pass filters. Doing some research I found mostly positive things about it saying that you always needed to setup a crossover so the speakers weren't forced to do the low hz sounds and that would somehow make it easier for it to play the mid and high sounds it's supposed to be playing. But then yesterday I found a thread on another forum and almost everyone was saying it was a waste of time and could somehow make it sound worse which I really don't get.
Now I'm confused on how much I need to consider this. I've got a set of Polk ES15 speakers and an RSL Speedwoofer 10e coming next week. I believe the speakers can technically go down to 46hz, but is there any reason not to make a high pass filter for them with EqualizerAPO (I also am not sure what a good number would be, 60hz, 80hz, 100?) and let me subwoofer do the work below that? Are there benefits to letting the polks go all the way down and I guess setting the low pass filter on the subwoofer to 46?

I never see anyone mentioning doing a low pass filter higher than 100hz but almost every sub I look at can go up to 200. Why is 100 a cutoff point and why can subs go up twice that if no one does it?

There is a bit of nuance involved. You can not make a blanket rule and say that you should ALWAYS use a high-pass filter. Nor a blanket rule for NEVER low-passing a sub above 80-100Hz. You have to understand why we use LPF's and HPF's and decide if the reasons apply to you. As @john61ct said, it's speaker dependent.

Why we use LPF's for subs: above a certain frequency threshold (>80-100Hz), subwoofers become directional - you can hear the location of the sub. If your sub is not co-located with your speaker, it will be audible as a separate source somewhere else in the room, which will frankly sound a bit weird. But if you place your sub in between your speakers, you CAN use a higher LPF if measurements suggest it would be advantageous to do so.

Why we use HPF's for speakers: to remove bass duties from woofers so that we can reduce distortion and make life easier for the amplifier. This is especially advantageous for 2 way speakers where the woofer has to cover an extended frequency range. Any distortion in the bass region will manifest as harmonics in the upper (mid/low treble) region. If you remove bass duties, you can avoid this.

But not all speakers are 2 way. Some speakers are capable of going down to 20-30Hz without a subwoofer. Do you need an LPF then? Well, it depends. Maybe you're lacking in amplifier power. Maybe there is still distortion in the low bass region. In that case, it would be advantageous to have a LPF. But you could also run it full range (as I do). I have two main speakers capable of going down to 20Hz, and two subwoofers. So I have four bass sources in my room, which I can blend together with DSP to produce the smoothest response possible.

 

[RedPanda42]

There is a bit of nuance involved. You can not make a blanket rule and say that you should ALWAYS use a high-pass filter. Nor a blanket rule for NEVER low-passing a sub above 80-100Hz. You have to understand why we use LPF's and HPF's and decide if the reasons apply to you. As @john61ct said, it's speaker dependent.

Why we use LPF's for subs: above a certain frequency threshold (>80-100Hz), subwoofers become directional - you can hear the location of the sub. If your sub is not co-located with your speaker, it will be audible as a separate source somewhere else in the room, which will frankly sound a bit weird. But if you place your sub in between your speakers, you CAN use a higher LPF if measurements suggest it would be advantageous to do so.

Why we use HPF's for speakers: to remove bass duties from woofers so that we can reduce distortion and make life easier for the amplifier. This is especially advantageous for 2 way speakers where the woofer has to cover an extended frequency range. Any distortion in the bass region will manifest as harmonics in the upper (mid/low treble) region. If you remove bass duties, you can avoid this.

But not all speakers are 2 way. Some speakers are capable of going down to 20-30Hz without a subwoofer. Do you need an LPF then? Well, it depends. Maybe you're lacking in amplifier power. Maybe there is still distortion in the low bass region. In that case, it would be advantageous to have a LPF. But you could also run it full range (as I do). I have two main speakers capable of going down to 20Hz, and two subwoofers. So I have four bass sources in my room, which I can blend together with DSP to produce the smoothest response possible.

Thank you for the info, guess I should have also mentioned what I would be working with. I'm getting two Polk ES15 speakers and an RSL Speedwoofer 10e that would be sitting a few feet below and in between the speakers. I have a JDS Labs Atom 2 DAC/AMP that I would be connecting everything to to act as the final volume control. So it would be the DAC plugged into my pc with a usb-c cable, that dac plugged into my amp through rca cables. Then two splitters coming out of the amp one going to the Douk/Fosi and one to the subwoofer.
I saw somewhere else mention that if you have the Douk/Fosi connected this way that you should just turn the volume all the way up since you are actually controlling the volume from the Atom 2 amp. This would let it use all of it's power, does that sound correct? This opens up the question of do I need the 48v power version or can I get by with the lower powered one? I wouldn't ever be using things at max or extreme volumes so I'm not sure if that extra power would just go to waste but maybe the 48v version has other benefits I don't know about?
I thought I had found my Amp and had a Fosi V3 ordered. But then I found a video on youtube comparing the v3 and Douk A5 and it said that the Douk won in almost every song tested sounding better. I know that can be subjective but it got me looking deeper and I was consistently finding praise for the Douk specifically for the high pass filter and PFFB (I don't really understand what that is but the review on this website made it seem like it was a good thing to have). These features are making me reconsider my choice, I can cancel my order and switch to the Douk and I am leaning towards doing that. Taking into consideration what I have do you think it would be a good move? If so do you have any suggestions on where I should set my high pass filter for those speakers? Is it something I'll just have to test at different levels or is there a general consensus on a good number?

After digging through more of the review of the Douk A5 a handful of posters are saying the HPF isn't very effective for some reason I don't quite understand. Seen a handful of recommendations for the Aiyima A07 Max instead. Man I've spent weeks doing research for this setup and every time I think I've figured it out I find something else that throws it all into question. I feel like I'm never going to be able to make a fully informed choice.