We give up perspective to avoid tone controls

Phase matching of subs-to-mains should always be optimized at the applicable crossover frequency, and the measurement point to define the match should be located (precisely) at the intended listening position.

OK, with you so far...

When ported speakers are involved, crossover frequency waveform propagation becomes more indistinct,

<< cough >> No it doesn’t. The crossover frequency doesn’t move around depending on the sub's cabinet type.

diverse, and increasingly affected by room-induced peaks and nulls that muddy the matching precision.

Which is why you should deal with the sub’s overall response first, and then the crossover matching second.

Peaks and valleys are easily dealt with by use of bass traps and EQ, regardless of whether the sub is sealed or ported. Again, if you like sealed, that’s fine. However, the crossover frequency and how it matches the subs is at the top of the sub’s range, not the bottom, where the room modes are (hopefully) less frequent and severe.

What often confuses listeners is that the same speaker, ported, will go deeper, and therefore is more likely to run afoul of those room modes. The peaks and valleys you mention.

Sustained wide area phase matching is a fantasy, and any expectation that synchronized phase can persist over more than a small part of the home listening room, or beyond the limits of a given test frequency, is misplaced.

Which is weird, because this is the very opposite of what you are attempting to discuss in your first sentence. It’s also a point no one has brought up, but since you have ... this all depends on how co-incident the sub and main speakers are, the measurement area, and the crossover frequency. If the sub is directly underneath the satellites, this is hardly an issue in most listening rooms.

At 80 Hz, 1 wavelength is 14 feet long. A quarter of that is around 4 feet. That’s how much the distance must vary from ideal before you have significant change.  So if you have two subs and satellites are right next to each other, so that in the center of the room, they are equidistant, you'd need to find a place in the room where the sub was 4 feet closer  or further away to you than the satellite.  On the other hand, if you use a single sub, located in the center, then yes, listening directly to the sides is probably this far. 

And like I think you are trying to get to, those peaks and valleys will make a much bigger deal than microsecond phase matching of the sub. However, they are just as hard, or easy to deal with in a ported or sealed speaker which covers the same range. So far it seems to me you are conflating phase/amplitude matching at the crossover frequency with the rest of it, which I don’t really get.

Best,


E

Virtually all such circuits cause significant channel tracking imbalance, and some add other phase and distortion anomalies that seriously degrade any aural benefit.

vtvmtodvm:
That's pretty breathtaking in it's scope. While I do agree: I wish manufacturers paid more attention to the quality of the tone controls, in general I have to disagree. I think the convenience factor needs to be weighed in. Like loudness controls for instance, being able to "convert" my speakers from medium to low-volume listening is a good thing, not to mention transforming them into party mode speakers.

Also, placement. Being able to adjust for speakers too close or too far from the walls is a case where tone controls are a lot cheaper than buying new speakers.

*Sealed-subs can be more accurately phase-matched with your main speakers than when using ported subs.

Since the ports contribute only to the bottom end, and the phase matching must occur at the top, I don't follow your logic.

There are many who feel sealed subs have the best transient responses though. In my experience, this is more a matter of integration and EQ than any absolute technical superiority of port vs. sealed.

It's also helpful to use sealed (not ported) main speakers.

This is often true. This is what THX tried to do with the satellite specifications, and has to do with phase and amplitude matching. They were big fans of LR4 alignments, and sealed sats + 2nd order HP electrical helps achieve this rather consistently.

Tute:

Yep, but how many want to do this? 

I mean, I do, but I'm a geek. :) I think when it comes to auto-room correction, the default curves matter a great deal. That's why I like to recommend JL Audio despite their absurd prices, and Dirac. I think they have the best default, out of the box settings. 

Best,

E

Let's put Audyssey in a different category! :) 

I agree it sounds horrible. 

But this isn't a condemnation of all DSP or room correction. Just this particular implementation. 

Best,

E

Room EQ Wizard is just measurement software. :) 

I have OmniMic, which does a fabulous job of creating FIR filters for miniDSP. I just don't want to futz like that.

Best,

Erik 

There's the MiniDSP DDRC series that does that. They have a version with digital inputs/outputs (which I use since I don't have any analog components and don't plan to purchase any) and one with analog inputs/outputs (balanced XLR).  

Yep, I am aware. My problems with that solution are

A) I don't want to pay for Dirac just to play with it
B) I like USB sources
C) I'm using Squeezelite as my virtual Squeezebox touch. 
D) My music server is Linux

So ideally, I'd like to have any EQ/time altering to happen in real time on my Linux box. There are many threads about using EQ in general with Squeezelite, but they are old and many of those links don't even work anymore. 

Best,

E

I do get some of the anti-tone control arguments. I never thought about channel to channel tracking for instance. Cheap stereo pots may vary widely. I’ve also used cheap pro EQ’s and they were not up to par.

I use a Parasound P7 for my pre, which has tone controls as well as bass management. Honestly I feel they are veiling. I wish I knew more about the circuits to see if they could be improved. On the other hand, the DSP unit I use for my subwoofer and center (sometimes) is as transparent as I could wish for. It is also far too cumbersome to use for basic album to album tweaking. It’s a measure, calibrate, and forget type of unit.

What I wish I had today is closer to the Theta Casanova. Convert everything to digital, and EQ in the digital domain. And I’d like that not to cost $10,000. Also, it has to sound GREAT, which the Casanova did, and was the only affordable processor I ever liked the sound of. Affordable only because it was used. :)

Best,

E

Many years ago, i had set up a half-assed rear channel system (long before surround sound) that relied on out of phase information (Hafler) and delay lines from a small processor. I used it with a pair of modest bookshelf speakers to supplement my Quad ESLs.

Interesting. I worked for a theater equipment company competing with Dolby. We were also a major buyer of Hafler amplifier modules and probably kept them in business.

We used a similar feature for non-surround encoded films. I wonder who licensed from whom?

Best,
E

@almarg and @mapman


Interesting! Maybe this is the year I finally figure out how to do this for free. :)

I think about this project from time to time, and then I remember that I am just not a big fan of old Thiel or any Vandersteen speakers. Wish I was, so many seem to love them, so then I just sort of give up.

Best,
Erik

 This is potentially the most important thread that could have possibly been started on any forum anywhere in the HEA world.

Thanks for your kind words, Michael, but I feel like this is probably just covering old ground. :) 

Best,


E

Kind of related to this, was the old Theta Casanova. Like the Casablanca, the Casanova was really an all-digital preamp. All analog signals were converted to digital first. Then DSP was used to do bass management. And honestly, that was a great little pre/DAC. Way ahead of it's time and still available for around ~$300. 

I believe there may have even been an EQ card available  (not sure if it was planned, but not implemented). 

It's a shame in many ways that this approach hasn't taken off, and that Theta is still chasing the installer only markets. << sigh >> 

Then we could be living in pure digital EQ world all our lives. :) 

Best,

E

@nonoise 

And this is kind of the problem. I mean, we give up any alleged "damage" for the sake of purity. Aren't we a little obsessed, to the detriment of our actual enjoyment and experience? 

Best,

E