Thanks @ Deleted b69c0aa that's also how I interpreted the wavelet, so good to know I'm on the right track with my understanding

PS: can I ask which processor you're using for delay correction? (software or hardware).

user of single subs/with monitors very close the front wall:

put your sub to fire sidewards so the edge of the cone comes as close as possible to the wall!

the effects (see below) cannot be achieved with any dsp; there is no substitute for correct physical placement - with carefull placement though, you may not even need to apply delay, you get better coupling (from an additional boundary, so a bit more level) for sure and way less phase cancellation in the lf area - for optimum reproduction, phase alignment is more important than flat/linear frequency resonse (or whatever curve you're aiming at)...

less work for your dsp processor can also yield lower latency (depending on processor).

...I'm using a BLU50 at the moment as a combo monitor controller/crossover/FIR processor etc. Attached below is the control app I made for iPhone...allows me to switch phase correction on/off or use a different EQ for rear of the room etc. (menu top left), mute, 0dB, dim, mono, switch LR...and there's a test oscillator on the right for pink, 100, 1000, 10000 etc...lower section allows me to mute individual speakers, reverse polarity...

Great unit, only thing I don't like about it is it's only 48k...BSS do 96k units that are three times the price, but they have really noisy fans so not useable in a studio IMO...drove me mad after five minutes.

This is how I have my sub setup actually, also tight to front wall...curious your resource for this however, haven't heard this stated anywhere before?

my 'resource' is 35 years of working in studios, live, as a recording/mixing/broadcast engineer, system tech, studio owner, designer, installer... - and simple physics:

with a front firing sub, you get a good deal of bounce from the front wall, or to be more precise: sound wraps around the sub, gets reflected on the front wall, bounces back into the room and combines with the direct sound - out of phase unfortunately...

[by changing the distance, you can actually 'tune' the sub to some degree or control which frequency gets affected the worst/where the most phase cancellation occurs. problem is that this only holds true for one specific distance/one frequency - yet we're dealing with a relatively broad band of frequencies, roughly two octaves.]

the only way to avoid this is to place a sub so it fires to the side and move it as close as possible to the wall (or to have it flush mounted) while all other issues can get adressed with eq, bandpass and allpass filters and delay.

keep in mind that sidewalls, table desks etc. have the same influence - and with multiple subs, things will complicate somewhat further...


p.s. cool app!

p.p.s. the 48k bss do not necessarily sound worse than the models capable of doing 96k; but shorter latency is always desirable - is the gui to control the bss still that horrible? and what are the steepest filters these days? haven't been programming any for years...

Nice! And to reiterate what deedee said, cool app! Wish I had some programming chops.

while we're at it: here's something seemingly slightly off topic... however, it's closely related to the use of dsp. but before we can do so, let's talk about the positioning of the measurement mic when aligning a sub...

regardless of dsp you are using, when doing phase alignment of a sub with mains,

put the measurement mic on the floor

at the listening position and use but one of the speakers! a measurement mic cannot know whether a signal is bouncing off the floor (and therefore arrives later than the direct sound) or if the sound arriving later is due to a larger distance from a speaker. by putting the capsule of the measurement mic as close as possible to the floor, you avoid (early) reflections to interfere with the direct sound, by using but one (top) speaker to go with the sub, you avoid getting phase cancellation from overlapping speakers firing from different angles/slightly different distance - mic orientation/axis then doesn't matter much while with both speakers, it'd need to be exactly on axis between them, down to millimeters.

do all eq alignments of all legs first, all at ear height/in the listening position; then put the mic on the floor at the listening position as the last step to phase align the sub with the mains.



p.s. you may have noticed that i wrote 'to phase align': you cannot really 'time align' a sub other than for one frequency/one distance! but by using allpass filters, you can get more even phase response over a larger frequency range of the whole system - unfortunately, not all/many dsp's have those filters available, so choose wisely....

p.p.s. use pink noise only for phase alignment, no sweeps - but that would be another topic and would lead a little bit too far...

Interesting, thanks. With multiple subs, how would you recommend going about phase alignment?

Cheers, I know a reasonable amount about this stuff, just hadn't heard of why placing a sub side firing would alleviate any issues...interesting, something I'll have to look into/experiment with! TBH the reason I have mine like that was just practical.

Thanks!...it's a work in progress...few other things I want to try and do with it, also make an iPad version, also see if I can link my Euphonix transport into it also...

Probably not OK...the latency on these is minuscule even at 48k, measured it before, I think it's under a 1ms I/O...I have a bit of a thing about response above 20k...also there is that bit of phase bending in the high frequencies from 48k...but anyway, I won't be changing it any time soon...Audio Architect is a bit of a PITA, but I've used it on a couple of installs so I'm pretty comfortable with it, you have to do silly stuff to get it to do what you want sometimes...the standard filters go up to 48, but there's also a NTM52, which I've never used...the biggest drawback with the Soundweb London is the lack of all pass filters...you can do those in FIR, but I don't get why they couldn't just have some ****ing all pass filters...other problem is it can't handle a huge amount of FIR, one BLU50 can only do 2x 4096...

that's way more tricky to answer...

if we really wanna dig into that topic, we then maybe should first discuss when and where to use a single or multiple subs, where to put them, what happens when doing so, what our goals and our preferences are...

we'd also need to consider what room size we'd be talking about as within smaller rooms (shorter than the length of the lowest frequency of a sub), lf behaves somewhat differently than in large rooms/open spaces.

also, there is a huge difference between distributed or arrayed subs, how they work, what they can achieve and how they interact with the room.


food for thought (and another thread imo)...

I agree with all that you said there, although if you're handy with Smaart you can get away with not putting the mic on the floor...worth checking after however, and best practice for bigger systems/crazy rooms OK. Regarding time aligning, I think it's best to turn off your crossover, both lpf to sub and hpf to mids, and align the speakers in time first, then enable the crossover and make adjustments etc. This way gets you close, and then you're only dealing with minor adjustments...my 2c.

hm, i'm having this thing with utmost phase accuracy (same on the way in and hence prefer coincident over spaced pairs) so i first want to have all things sorted out which affect phase relationship (eq, filters) and only then align. on some controller/dsp i don't want to re-visit previous pages in the controller menue again!:-) - but yeah, why not align the way you described it! and thx for an 'update' of audio architect: 'burning down the house'comes to mind...

here's a valuable contriution from a friend of mine:

___


Digital Room Correction is a very poor choice of words. This has made it the subject of attack, even ridicule, by many unwilling to recognise it’s fortes.
In a purpose built room with the world’s best speakers, Eq would have little or nothing remedial to do, but even there is widely used to create Target Curves, to achieve better translation to Home Hi Fi or Cinemas.

How can we Correct a Room? Well, acoustic treatment of course. This can vary from Passive (Fibre) to Reactive (Tuned) to fully Active.
The latter would include Double Bass Array, The Bag End E-Trap, and PSI’s AVAA. The last two are autonomous, they ‘listen’ to what is going on in the room and cancel some low resonances by emitting reverse phase energy. Electronic Room Correction, but I think they are both Analogue.

Everything else is Eq which controls the Speakers. Speaker Controllers. In both live and studio systems 1/3 Octave Graphics were originally widely used. They are sill popular in Live work, hands on, but in all cases Parametric Eq addresses between band frequencies and varied bandwidths much more accurately and so has become the norm in Studios, and increasingly so in Live.
The Eq can be software in the DAW, the OS. Analogue or digital in an external box, in the converter, in the amplifier, in the speaker.
Meyer Sound were the first or most notable to use computer based sound analysis including time. Using their SIM system, they analysed the differences in the responses between the electronic signal in the mixing desk and at various locations in a venue via mics. In real time using real performance signal. Rather than guessing algorithms, a trained operator would decide on mitigating Eq and apply it using their Analogue Complimentary Phase Equaliser. https://mpe.berklee.edu/documents/st...0%20manual.pdf
Pun intended, it is a compliment to the design and quality that these boxes are still regularly sold in the Live sound equipment context.
Probably a good choice for the Studio too I reckon. It is noteworthy that the once popular Meyer HD1 Studio Monitor had similar Eq on board, again analogue. So complex only the factory or distributors were authorised to adjust the many interactive controls. This onboard calibrating system was to make a pretty good speaker much better. Speaker Control, Calibration…..
Many other manufacturers include tweaks in the crossovers, both analogue and digital, to ‘Correct’ some transducer or box anomalies. Indeed what is a crossover but a Speaker Controller, by Eq, and with DSP, including timing.

Moving back the chain from the speaker, we have Trinnov, Coneq, Sonarworks, Acourate, REW+EQ, Dirac Live as standalone software or built into hardware products. In Live, Lake, XTA, and many speaker controllers proprietary to particular speakers.
They are all speaker controllers, they are all Eqs. None will affect the room in any way. But by modifying the signal going to the speaker, they can greatly enhance it’s delivery to the ear via the room.

DD

Wish I had programming chops also BSS designed the shell iOS app. You just make up stuff in Audio Architect to get it to work...it's a bit like Max/MSP if you ever used that...mostly drag and drop...though some tables for values stuff...see pic below.

HiQnet Motion Control v1.x (iOS) | HiQnet Audio Architect

good to see you back, DD.

The digital room correction or the negation of the properties of a wave: length, period, cycle, time....

Today all is possible ; The Prap

Herb's Postscript from the Park Lane Hotel | Stereophile.com

too bad you deleted your post...

seemed more like you're not knowing what a capable dsp can do: for instance, even very well designed speakers with typical 24db x-overs show asymmetrical phase behaviour far above and below the crossover point with speakers under non constant load (such as music) - only dsp with allpass filters can correct this (to some degree), but no amount of room treatment gets just anywhere close...

...but to get to the point:

acousticians aim at tuning the room, engineers aim at tuning the speaker response!

in small but typical rooms, most folks have not much options for speaker placement and they don't have much space to waste - yet all they actually need to do us to make sure their speakers sound reasonably well at exactly one position, which is their listening position. this is realively simple to achieve: use a sub to load the room, use some corrective eq - voilà! not ideal, but gets the job done.

don't invest too much in gear that kills your sound (room treatment), invest in time to learn your speakers and your engineering, use simple apps or sophisticated fft to assist you, get a dsp and apply minimal treatment for some of the obvious things - besides, you can take dsp anywhere you go; try doing this with your bass traps, absorbers, diffusors etc.?!?

you're right though that dsp can not correct all issues - but don't call it room correction ever again