High pass filters, low pass filters, no pass filters

[john61ct]

Personally I think having all your bass management / crossovers at line level independent of various power amps, will give much greater accuracy and flexibility.

An all-in-one DSP + preamp + sources like Wiim Ultra / Wiim Amp Ultra would be the exception, at least for getting started and saving money.

It's not just frequency blending, but timing delays and phase alignment between main pair and sub(s).

There are DSP plate amps that get sophisticated enough but they aren't cheap.

 

[thcdru2k]

If you run PC to atom to splitters then the HPF happens before the split so it high passes both speakers and sub. I think that is not ideal.

I would not use a speaker’s claimed frequency spec as a crossover point. That number just tells you roughly how low the speaker can reach, not where it hands off best to a sub.

Also, overlap is not automatically bad. A sub LPF higher than the main HPF can work really well if the level, phase/delay, slope, and room response line up. If you have proper bass management and measurements, then overlap can be a useful tool.

 

[Keith_W]

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.

Well, let's take a look. First, the Polk ES15. I can't find measurements for the ES15, but here are Amir's measurements of the S15 (I don't know if it's the same speaker, Google images suggest they look alike?): link to Amir review.

First thing we see is that the speaker rolls off very sharply below 70Hz.

We also see that even within the usable range, distortion shoots through the roof at about 150Hz at 96dB. It is tolerable at 86dB though.

In short: this speaker NEEDS a subwoofer. If you don't play loud, you can get away with no HPF for the speaker. Simply give the sub a LPF at about 80Hz or so. But if you DO play loud, you will need to deal with all that distortion. One option is to give the speaker a HPF one octave above where all the distortion is (i.e. about 300Hz!!!) but this is unreasonably high. You are better off choosing a different speaker if your intention is to play loud. Or choose a pair of subwoofers that can go up to 300Hz, place it under the speaker (it MUST be co-located!), and XO at 300Hz.

This is what I mean when I say "it depends".

As for your subwoofer, here is a review done by Audioholics. First the frequency response:

... it's not great. It rolls off quite sharply below 40Hz. To be honest, it probably won't do this in your listening room - you will get some room gain. So in-room, you might get more bass than the measurements suggest. But what about distortion?

Again, note that their testing starts at 93dB and ends at 106dB, it's hardly fair on this small sub. IMO it's not going to be as bad as these measurements suggest, but it would be better if the sub didn't do that.

In short - your choice of speaker and sub are suitable for a small room, and at moderate listening volumes. If that's all you ask, it's fine. Just don't expect rock concert SPL and thundering bass.

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.

I have no idea what those things are. My view is very simple: if it has the features that you want, and the price is attractive, it's an acceptable choice. I don't care what people say about what it sounds like, and I don't even care about the measurements because the chance of hearing a difference is going to be very slim! I have to admit that my view is in the minority here on ASR, even among measurement freaks. My strong belief is to pick all the low hanging fruit, and it's ALWAYS speakers, rooms and DSP first, and electronics a very distant second!! I am very sorry, maybe someone else on ASR can help.

 

[RedPanda42]

Well, let's take a look. First, the Polk ES15. I can't find measurements for the ES15, but here are Amir's measurements of the S15 (I don't know if it's the same speaker, Google images suggest they look alike?): link to Amir review.

View attachment 541450

First thing we see is that the speaker rolls off very sharply below 70Hz.

View attachment 541451

We also see that even within the usable range, distortion shoots through the roof at about 150Hz at 96dB. It is tolerable at 86dB though.

In short: this speaker NEEDS a subwoofer. If you don't play loud, you can get away with no HPF for the speaker. Simply give the sub a LPF at about 80Hz or so. But if you DO play loud, you will need to deal with all that distortion. One option is to give the speaker a HPF one octave above where all the distortion is (i.e. about 300Hz!!!) but this is unreasonably high. You are better off choosing a different speaker if your intention is to play loud. Or choose a pair of subwoofers that can go up to 300Hz, place it under the speaker (it MUST be co-located!), and XO at 300Hz.

This is what I mean when I say "it depends".

As for your subwoofer, here is a review done by Audioholics. First the frequency response:

View attachment 541454

... it's not great. It rolls off quite sharply below 40Hz. To be honest, it probably won't do this in your listening room - you will get some room gain. So in-room, you might get more bass than the measurements suggest. But what about distortion?

View attachment 541455

Again, note that their testing starts at 93dB and ends at 106dB, it's hardly fair on this small sub. IMO it's not going to be as bad as these measurements suggest, but it would be better if the sub didn't do that.

In short - your choice of speaker and sub are suitable for a small room, and at moderate listening volumes. If that's all you ask, it's fine. Just don't expect rock concert SPL and thundering bass.



I have no idea what those things are. My view is very simple: if it has the features that you want, and the price is attractive, it's an acceptable choice. I don't care what people say about what it sounds like, and I don't even care about the measurements because the chance of hearing a difference is going to be very slim! I have to admit that my view is in the minority here on ASR, even among measurement freaks. My strong belief is to pick all the low hanging fruit, and it's ALWAYS speakers, rooms and DSP first, and electronics a very distant second!! I am very sorry, maybe someone else on ASR can help.

Don't worry about it I really appreciate the effort you took and it helps.

 

[Ropeburn]

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.

I find proper, full range preamp outputs way more useful than "subwoofer" outputs with simple lowpass. Because you can use them either as full range pre outs for chaining amps or using poweramps or whatever, and subwoofer outputs - anything active will have its own lowpass, and you neither need nor want two in a row. Useless and potentially messing with phase and response and stuff more than necessary. Stereo is also better than mono when you're using two subwoofers.

The only use case where it'd be practical is when you're running passive subwoofer(s) with amps without any filters. And let's be honest, that's a very niche use case for enthusiasts, who usually have active crossovers of some kind anyway. And then again they'll want a full range stereo out, not a forcibly lowpassed mono one.

 

[Chrispy]

I find proper, full range preamp outputs way more useful than "subwoofer" outputs with simple lowpass. Because you can use them either as full range pre outs for chaining amps or using poweramps or whatever, and subwoofer outputs - anything active will have its own lowpass, and you neither need nor want two in a row. Useless and potentially messing with phase and response and stuff more than necessary. Stereo is also better than mono when you're using two subwoofers.

The only use case where it'd be practical is when you're running passive subwoofer(s) with amps without any filters. And let's be honest, that's a very niche use case for enthusiasts, who usually have active crossovers of some kind anyway. And then again they'll want a full range stereo out, not a forcibly lowpassed mono one.

I'd find a full range set of pre-outs generally more useful than a single frequency limited "sub" pre-out. Many unfortunately use no crossover of any kind still