Erin's Fosi ZA3 Review and Bass Management

[Humon]

I like Erin and I watch most of his videos, but this one I couldn't get onboard with. I'm not really concerned with that particular product, but in the end he says the purpose of a subwoofer is to alleviate the load off your mains. Really? Maybe I'm dumb, but I thought the purpose of a subwoofer was to play the low frequencies that the mains can't reach, or to be more accurate, the frequencies that they can only reach with diminishing returns. They're powered because lower frequencies require more power. He strongly suggested that high-pass filtering was a must for bass management, yet he didn't say anything about what frequency the cutoff should be or how much, if any, overlap there should be between the mains and subs. There wasn't any discussion of the sound trade-offs involved with making subs produce a wider range of frequencies, which is obviously a very real concern.

Outside of AVR's, how many amps actually have high-pass filtering for the mains? It doesn't seem to me like there are very many, regardless of price. I have owned two amps that had some of the most extensive bass management that I'm aware of for analog amps: the Emotiva TA2, and the Parasound PA6. I literally spent many hours over several weeks tweaking the bass management of these amps trying to find the right mix. In the end I turned off the high-pass and low-pass filters and ran full signal to the mains and the sub and set the crossover on the sub, completely bypassing bass management. None of that filtering did a thing for the sound, and I actually preferred the sound without any of it engaged.

I sold those amps and now I have a Musical Fidelity MS6 preamp that has no bass management at all, and it sounds absolutely fantastic. I feed the subs from my power amp through the high-level inputs and set the crossover on the sub somewhere around 50 Hz, but I could probably go lower. I'm sure it has its uses, but my experience was that bass management, especially high-pass filtering, was a solution in search of a problem. It's just patently not true that these things are a necessity.

 

[roladyzator]

In recent reviews, Erin shows multitone distortion with an 80 Hz high pass filter. Usually smaller two way speakers show an improvement in the numbers.

Typical frequency for high pass filtering is 80 Hz, but it is good when you can adjust it.

Studio subwoofers typically have adjustable high pass filters. You connect your stereo source to the subwoofer, set the HPF there and use subwoofer line out to connect to your mains. Some non-studio models have pass-through connnection to the mains (they don't filter the signal going to the mains), which makes them possible to be used with a stereo input. Some subwoofers don't even have that and they need a dedicated signal.

It's easy to create the LFE channel yourself if you have an AVR or a 5.1 soundcard, but with typical stereo equipment, a sub output is a less common and should be appreciated.

Bass management is not only about adding more output at lower frequencies but also about improving the response in the room and reduce seat to seat variations.

For example, four subwoofers in wall mid-points would give you a consitent bass across a wide listening area, like a home theater system. Todd Welti has done research into this, and it's described in Sound Reproduction by Floyd Toole as well. That's a book every audiophole should read.

The location of the main speakers is often dictated by non sound-related factors, but more practical reasons like the availability of space, existing room arrangement concepts etc. If they produce bad quality bass because of it, it's worth trying delegating all bass to subwoofers.

 

[GM3]

he says the purpose of a subwoofer is to alleviate the load off your mains. Really?

Depends on the mains. If you're using speakers designed to be fullrange speakers, such as https://www.focal.com/us/high-fidelity-speakers/utopia-iii-evo/grande-utopia-em-evo , then you likely want to run them full range and make use their 16 inch woofers.

By contrast, if you're using something like Kef LS50 Meta https://us.kef.com/products/ls50-meta , which use 5.25 in woofers and aren't designed for bass or high SPL, then yes, you definitely want your sub to take over the bass, and alleviate the load of your main speakers. (Their performance at high SPL or bass reproduction isn't amazing)

For such a tiny and cheap budget amp, the odds that you'll want to use them with truly full range speakers is kinda low. Pretty sure that in in ~90% cases you'd be better off using a crossover with a sub. In the amp's review page, some mentioned that the crossover would be better to do in the digital domain, by another device. Probably true, but when considering whether it would be better to have the feature vs not having it, even if not optimal, likely would be much better to have the option rather than not, in the majority of cases.

I know I was kinda considering one because of the lack of options for sub out of my current digital amp, but lack of crossover made me dismiss the idea. That's with bookshelves going ~45Hz. If I can't cross them over ~60-80Hz ish with the sub, then in my particular case it's not worth adding a sub. I would want the sub to take over the bass, not just add lower bass. But YMMV. Depends on your sub, speakers, usage, etc. (in my particular case, with room gain, it would be impossible to add a sub without having 40-80 Hz go absolutely nuts; would be impossible to balanced bass while having both sub + speakers play bass)

 

[DVDdoug]

he says the purpose of a subwoofer is to alleviate the load off your mains. Really? Maybe I'm dumb, but I thought the purpose of a subwoofer was to play the low frequencies that the mains can't reach, or to be more accurate, the frequencies that they can only reach with diminishing returns.

That's pretty much the same thing. Bass management re-directs the bass to the sub and combines it with the LFE (if any). It's one reason for a subwoofer.

Without a sub you lose the "point one" LFE channel in movies.

Bass management (a crossover) is optional. If you have full range speakers you can turn off bass management and allow the stereo and surround speakers handle the "regular bass" from the stereo and surround channels with only the LFE going to the sub.

Outside of AVR's, how many amps actually have high-pass filtering for the mains?

Not many. And most don't have decoders for surround sound or the LFE.

I sold those amps and now I have a Musical Fidelity MS6 preamp that has no bass management at all, and it sounds absolutely fantastic. I feed the subs from my power amp through the high-level inputs and set the crossover on the sub somewhere around 50 Hz

That's fine. If you have another crossover you don't need "bass management". But of course, you should feed the main amplifier/speakers from the high-passed crossover output.

 

[amirm]

As I commented in the other review thread, folks trivialize addition of subwoofers. As you experienced, you can be in a world of hurt the moment you do that and saving a bit of distortion from your mains may be the least of your issues. Any addition of subwoofer must, let me repeat, must be accompanied by measurements and optimization of bass response as you have now hugely increased modal issues in the room.

In addition, there is a school of thought advanced by Earl Geddess which says leave all speakers full range so they act like distributed set of subs.