Move around the room when adjusting delay on subs, not tops. Then, delay tops to match with subs.
See above
I've experimented w/reversing polarity at my possessor. I don't run them that way. Most I've heard from don't run them reversed; just delayed if needed (they don't always need delay - not all venues are the same).
Between 85Hz and 100Hz, depending.
Cresendo,
1)Sorry, but this makes no sense. A TH sub lags behind the tops by the path length difference plus filter latency, there is no reason to delay the subs, unless you were to delay only one sub to align with another at a particular place in the room. That type of alignment would result in misalignment at all other locations.
2) If the TH driver is wired so positive voltage moves the cone towards the horn throat, the polarity is correct, and does not need to be reversed. If the polarity is reversed (positive voltage makes the cone move towards the mouth), the path length corresponds fairly closely with the wavelength of a crossover around what you use (85 Hz to 100 Hz) and can result in an "in phase" response that lags behind the top cabinets by one wavelength when using no delay.
To time and phase align the tops to TH requires the polarity to be wired so positive voltage moves the cone towards the horn throat, and the tops wired so positive voltage makes the cones move toward their exit, then delayed by approximately 6-12 ms depending on cabinet and DSP design.
Assuming the tops are placed above the subs and the alignment is done correctly, the delay will not change regardless of the room.
Art
If you're trying to accomplish what I was referencing in post 1675, it does. All you have to do is delay your tops a bit further to match. It's a way I've found to "cheat" some venues with low spots in a certain frequency I needed more of. It's always a trade-off, however.
I agree
In post 1675 you wrote:
" you can adjust the subwoofer delay to increase (aka move) 40Hz in the center of the dancefloor, yet you'll notice a different frequency (maybe 80Hz, for this example) decrease. But, that 80Hz may have increased a few steps back. Change the delay to have 80Hz strong in the middle and 40Hz will decrease there and increase a few steps back (where 80Hz was solid)."
Adding delay to the subs is the same as delaying the time when you hit "play", the only difference it can possibly make is if you delay one sub in relation to the other, which is not implied by what you wrote.
Changing the alignment between tops and subs will change the frequency response in the crossover region, but there is no reason to delay subs unless you were trying to align sound to a delayed video.
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Hi Art,
With tops muted, changing delay on the subs will make an SPL meter fluctuate at a given frequency. If what you said above were that plain and simple, this would not happen. Although, what I'm suggesting as an experiment may not be conventional, something else is going on when delay, on the subs alone, is adjusted.
With tops muted, changing delay on the subs will make an SPL meter fluctuate at a given frequency. If what you said above were that plain and simple, this would not happen. Although, what I'm suggesting as an experiment may not be conventional, something else is going on when delay, on the subs alone, is adjusted.
A temporary fluctuation in the response of a SPL meter is certainly possible (though SPL meters do not measure a given frequency, they measure a range of frequencies dictated by the weighting chosen), as room reverberation at low frequencies will allow the "old" signal to combine with the new delay time, creating a comb filter response. After the reverberation of the initial setting dies, the meter will revert to it's previous response. If using a single frequency sine wave for testing, the larger the size of the room and longer it's RT-60 time, the longer the temporary change would be heard.
If you measure response using a dual FFT system like Smaart or Systune, or even a standard RTA you will find the fluctuations you noted are temporary, the same as they would be if you had the same track cued up on two playback units, hit "play" on player one, then hit "play" on the second unit the same instant you hit "stop" on player one.
Yes, a single frequency sine wave for this example.
I knew there was theory behind what I witness. Thanks for that.
While we're on this topic (and maybe a longshot), but is there a window (or windows) in Hornresp or Akabak that may shed some knowledge on how one speaker/subwoofer might behave/fill the room vs another? Although different systems (TH, FLH, BR, etc) have different sound characteristics, some fill the room differently than others. I didn't think it was purely due to drastic differences in frequency response. There's got to be more to it (thinking pressure at mouth, particle velocity, and some other stuff I'm hoping to learn about)
I knew there was theory behind what I witness. Thanks for that.
While we're on this topic (and maybe a longshot), but is there a window (or windows) in Hornresp or Akabak that may shed some knowledge on how one speaker/subwoofer might behave/fill the room vs another? Although different systems (TH, FLH, BR, etc) have different sound characteristics, some fill the room differently than others. I didn't think it was purely due to drastic differences in frequency response. There's got to be more to it (thinking pressure at mouth, particle velocity, and some other stuff I'm hoping to learn about)
Delaying one or more subwoofers if you have multiples of them in different locations can help "direct" the bass. Look up "directional bass array" for examples.
On getting the delay right between the tops and the subs, anyone know of a good, simple and repeatable way to get this right?
On getting the delay right between the tops and the subs, anyone know of a good, simple and repeatable way to get this right?
A quick (& dirty?) way that works well: After positioning your tops & subs in their performance location, set your spl meter about a meter away. Reverse the polarity of your subwoofer(s). Play a sine wave of your crossover frequency through the system. Adjust your delay (typically of the sub(s), but either will work, theoretically) until you reach the maximum dip (sometimes -3dB to -6dB or more). Reverse the sub(s)' polarity back to normal. Enjoy!
This sounds like something meant for subs and tops, on a single pair of subs @1m, why make muddy bass?
Sorry, I misinterpreted some of what I read. For the most part I agree with what you wrote, although 1m is way to close IMO as it exaggerates the correction because of the usual difference in height of the tops vs subs. The TH measures "better" at a distance too, it seems to me that some distance is needed for the radiation from both sides to driver to fully combine.
I don't disagree. I suppose I should've asked about room size.
To clarify, might as well measure with meter at the listening position.
To clarify, might as well measure with meter at the listening position.
The muddy bass comment came from the earlier discussion of using delay between subs to address a FR hole (AKA room mode). If the subs are just a pair or two of TH18's side by side the delay is making a mess of the impulse response in exchange for a better SPL meter reading, I say this is comparatively worse than EQing a room mode. Room modes suck, and I know there are relatively few options at a gig, but if I were ever going back again, I'd for sure schedule some time to work out a better placement.
Are you referring to a delay between sub #1 & sub #2 when paired, side by side? Can't say I've ever done that.
You got me thinking, and I remembered there is a decent example in a paper by Rog Mogale of Void Acoustics. It uses larger cabinets than the TH-18 on it's side so I would think there would be a difference in directivity vs a double 18" in the examples, but they are still worth checking out IMO. It does show there are reasonable benefits to be had using mild delay with 4 cabs.
Well, yeah - with 4 cabs. Delay the outer subs a bit. Except when I run 4 of my subs (TH-18), they're typically with all of their mouths together, so - no outer subs to delay. If they were all standing up I could.
I try 😉
Would you have rather clicked on this? My brain went NOPE!
Code:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB8QFjAA&url=http%3A%2F%2Fwww.voidaudio.com%2Fsupport%2Fitem%2Fdownload%2F81_11ff1f36257aea2cbccaa0c34d54e4cc.html&ei=Y9e2U4XOJ8OBqgbRhoKIBA&usg=AFQjCNEw3c4RsGFs4eAa79UCDM6laPsp-w&sig2=NuVGDNSfbLx7wGN_ciM_vQ&bvm=bv.70138588,d.b2kHornresp and Akabak both simulate cabinet response, not room interaction, other than a view of 1/2, 1/4 or 1/8 space which is not helpful in room prediction since it simulates the rest of the space as free space.
Meyers and DSL both have freeware that can simulate room interaction with multiple subs, though they don't address the third dimension properly, nor do they address directionality, which is a separate function from frequency response and can result in different room response even for subs equalized flat on axis.