OK, But he's specifically only talking about "small" roioms, which I assume means too small to support the fundamental. That's REALLY small, and we all know that you can put a sub anywhere in your A/V room. No big surprise.
But we're talking about live music venues here. (or even outdoors.) The entire pro audio world can't be wrong about the need for using delay or phase flips.
So does anyone know the real, answer ?
But we're talking about live music venues here. (or even outdoors.) The entire pro audio world can't be wrong about the need for using delay or phase flips.
So does anyone know the real, answer ?
I have used the info this guy shared , the video is very easy to digest , I applied those principles of delay and phase flip on subs and work like a charm on a "small dance hall" about 300 people , he also share a cheat sheet to calculate handy live audio calculations.
He have many videos PA related for different sub arrangement and PA system calibration and setups.
He have many videos PA related for different sub arrangement and PA system calibration and setups.
Hello Cableaddict,
Here are some videos, simple and straight forward:
1st, you need to understand what software and tools to be used to measure your system, in this case I'm suggesting you to use the Software REW, it's free. Some people uses Smart but is payed and expensive.
Once you able to setup the measurement system, you have below two methods to define the delay.
Impulse Response Method, this will take into account loudspeaker with longer horn as TH and others.
Distance Method, attention becasue you need to add Horn length** values
**Take a look at the attached image, as you can see, besides the driver is close to the mouth, there is a folded horn inside that needs to be taken into account, due to that there is the unfolded representation that you can better see how long it's, in my case I have one box with 2,4m.
Attachments
REW as a tool for matching delay is perfect. The best (for me) instructions I found were on the MiniDSP website.
REW instructions
I was able to calculate the delays on 3-way speakers to a pointlessly precise 5us (micro seconds). Pointless because I can only control delay to 100us, and pointless because I doubt my hearing is capable of discerning that precision.
Re-measuring the impulse response after adjustment did create razor-sharp peaks - spikes, really - giving me a warm glow of smugness that I had been thorough 😉.
As an unexpected benefit, the REW impulse responses made it apparent that the amp I was using for the tweeters was inverted internally !
I also used the software RePhase to unwrap the crossovers. That requires a DSP that is FIR capable.
REW instructions
I was able to calculate the delays on 3-way speakers to a pointlessly precise 5us (micro seconds). Pointless because I can only control delay to 100us, and pointless because I doubt my hearing is capable of discerning that precision.
Re-measuring the impulse response after adjustment did create razor-sharp peaks - spikes, really - giving me a warm glow of smugness that I had been thorough 😉.
As an unexpected benefit, the REW impulse responses made it apparent that the amp I was using for the tweeters was inverted internally !
I also used the software RePhase to unwrap the crossovers. That requires a DSP that is FIR capable.
Speaking of FIR, what current processors can do FIR, just don't say LAKE....yes they can do FIR but are not in the mere mortal DIY budget, they cost 3k+, something more attainable in the 400-800 range, don't matter if it is used.
@maxolini Several of the MiniDSP FLEX range have FIR support.
https://www.minidsp.com/products/minidsp-in-a-box
https://www.minidsp.com/products/minidsp-in-a-box
@BlinkTooFast
I just read you need at least 2048 taps to make some ok ok filters, better to have 4096 taps, but the more taps the more DSP power... iron law I think
I just read you need at least 2048 taps to make some ok ok filters, better to have 4096 taps, but the more taps the more DSP power... iron law I think
@maxolini Possibly.
I have the FLEX Eight, with 2048 per input channel.
From the MiniDSP website:
The following miniDSP processors support FIR filtering:
I have the FLEX Eight, with 2048 per input channel.
From the MiniDSP website:
The following miniDSP processors support FIR filtering:
- miniDSP 2x4 HD. Supports a total of 4096 taps dstributed across the four output channels.
- miniDSP Flex (without Dirac Live). Supports a total of 4096 taps dstributed across the four output channels.
- miniDSP Flex Eight (without Dirac Live). Supports a total of 4096 taps dstributed between the two input channels.
- miniDSP OpenDRC-DI. This is a pure stereo processor (two inputs, two outputs) and supports 6144 taps on each channel.
The 'phase trace overlay' method is the most time honored approach.
It is taught in Rational Acoustics' Smaart classes,.... by Bob McCarthy..... by many experienced folks.....and frankly I think by anyone who knows wtf they're talking about.😀
The Smaart instructors say the number one question they get asked is how to align subs to mains. They also point out the irony, that with PA the odds of subs being collocated with mains is lower than with perhaps any other audio, making the alignment much more particular to a spot.
If subs and mains are collocated, the major problem with alignment ime, is getting a good measurement of the sub's phase trace.
FFT's collect frequency data linearly, so the sub spectrum doesn't provide a whole lot of data to work with. The ability to use a dual channel FFT that allows temporal averaging when making transfer functions, really helps to get a more valid phase trace. Examples being Smaart and OSM (opensoundmeter).
Alternatively, REW can average a number of single channel sweeps to increase phase trace validity. If you can stand all the whooops!
This guy that someone linked previously has a pretty good vid on the 'phase trace overlay' method, if you can hand in with his non-stop machine gun presentations.
It's cool he uses OSM in his presentation, which like REW is donateware. Put's another great tool within our general reach.
It is taught in Rational Acoustics' Smaart classes,.... by Bob McCarthy..... by many experienced folks.....and frankly I think by anyone who knows wtf they're talking about.😀
The Smaart instructors say the number one question they get asked is how to align subs to mains. They also point out the irony, that with PA the odds of subs being collocated with mains is lower than with perhaps any other audio, making the alignment much more particular to a spot.
If subs and mains are collocated, the major problem with alignment ime, is getting a good measurement of the sub's phase trace.
FFT's collect frequency data linearly, so the sub spectrum doesn't provide a whole lot of data to work with. The ability to use a dual channel FFT that allows temporal averaging when making transfer functions, really helps to get a more valid phase trace. Examples being Smaart and OSM (opensoundmeter).
Alternatively, REW can average a number of single channel sweeps to increase phase trace validity. If you can stand all the whooops!
This guy that someone linked previously has a pretty good vid on the 'phase trace overlay' method, if you can hand in with his non-stop machine gun presentations.
Indeed. Geddes likes the multiple distributed subwoofer approach, but that's in small rooms. Geddes is in the "Bass is omnidirectional" camp, which may be perceptional correct in you living room, but isn't for larger spaces. Also, for PA work you tend to look for the best slam from the system, which may take some tuning of the phase or delay. Bass is usually much hotter/louder in a PA than it is in a home system. A PA is almost a musical instrument itself, shaping the music. Home "Hi-Fi" systems are different.
The cardioid stacked sub trick is very popular these days as it helps keep the LF off the stage. But the OP isn't doing that.
But wasn't this about a "small" room? A "small" room is larger than most people think. I don't think we were ever told how big the room is.
How big a room needs to be before it is no longer a "small" room is debatable, so the best starting point is to measure first to determine what the specific issues are. That will be more productive than debating definitions!
Room size will vary. But it likely is not living room size Medium size, nit small?
This isn't about a room in your house! (Obviously) In pro audio, any fully enclosed space is generically referred to as a "room". The volume of your entire house is a "small" room...assuming you don't own a literal castle...