The Geddes Multi-Subwoofer Bass Optimization Approach
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- Опубліковано 21 лип 2024
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Speaker and content creator: Matthew Poes
Videographer: Ryan Wohldmann
Event Host: Mike Masunas - Наука та технологія
I built my 5 sub distributed bass array based on science just like this. It really works! Freaks me out to think this has been around since 2004 (and really since the 1980's!) and works so well yet hardly anyone knows about it.
fantastic video... thanks for posting
Good job -- well done! Packing Dr Geddes work into a 30 minute bit without head-scratching (I did back up a time or two . . ;) ), or repetition takes some sharp planning . . good on ya'!
Awesome info.
I'm in a bit of an odd situation. I have one room that I use for general edit and mix tasks but also watch the occasional film in.
I am able to monitor playback on my Tannoy monitors and/or my 5.1 system. The 5.1 system is a bit of a Frankenfreak. The front and surround left and right channels are all full-range (2-way bass reflex tops on dual 8" EAW subs). My center channel and LFE are sort of a matrixed hybrid. As in, the center top sits on top of my LFE EAW configured identical to the other mains channels. I end up routing the center channel to the LFE output in addition to the center top. I do this because I only have five of the EAW subs and do not have the space for the LFE to float around elsewhere. My LFE serves double duty in being my LFE and the bottom end of my center channel.
I'm finally up and running with REW and have started analyzing each speaker as it sits in the room.
I've also got the ability to route my main Tannoy feed to any element or combination of my 5.1 system. I essentially have the option to spread my LF energy from any combination of source channels in either system to any of five physical LF playback sources. The testing is the simple part. This video just opened up my plans in a big way. It will be interesting to see what I can actually accomplish with this gear in the space I have.
I watched both the talks. Very interesting stuff!
I wonder what could be the application of the Geddes approach in a music studio, though.
Usually, in studios, monitor speakers have 8" woofers and are pretty capable of playing low frequencies. Expecially the good ones. In fact in many studios there are no subwoofers around.
So, I wonder if adding just one sub (instead of 3) in a different location of the room would make things better? Of course in this scenario one would avoid to hi-pass the main speakers.
Would this provide a similar result to multi-sub?
Or, at least, would 2.1 (no-crossover), be better than just 2?
Also how does the speaker stand when it comes to subwoofer quality for music studio application? An average, but linear, subwoofer could actually do the job potentially?
Anyways, thanks so much for posting this. It bustes so many myths and provides a lot of sometimes difficult to digest information in a easy way for the most part.
You should note that Geddes uses bandpass subwoofers which are rare on the commercial market, this is important relating to the crossover/ low pass application of a 6db filter versus steeper filters which is needed to get the preferred frequency response from more common subwoofer systems. The more common ported and sealed subs do not roll off like the bandpass, VERY important detail. Sorry I'm 10 months late ampslab.com/blog/2018/07/22/albatross/
No need to apologize! That IS a very important bit. Thank you. :)
Bandpass plus first order is butterworth 18db/oct
Interesting. I guess I'm using the Welti method then. The idea I am working with is that the same sound from multiple sources sums and cancels, but different sounds from different sources do not. So my stereo signal is crossed to a summed signal at 100hz. I'm copying the Genelec W371A, which seems to be Welti inspired as well, since it uses 4 symmetrical subwoofers. But it incorporates vertical height, which this vide says is from Geddes.
Does the LF source need to be the same size or can you mix as long as they are all the same type: sealed or ported?
J P I believe Earl says to mix them up if you use his approach. Mine are different sizes. Welti, I believe, recommends the same size and type of subs.
You mention the application of EQ, but didn't say whether that was global or on a per-sub basis. I'd be keen to know what is applied.
Its 2-3 bands of PEQ per subwoofer which then measured globally should result in a smooth curve (not flat)
I think the subwoofer still plays a big factor on sound quality. I’ve observed that even if the frequency response and spectral decay measures the same, one can still sound subjectively better. To me it just means we aren’t measuring or observing the specific attribute related to the perceived difference.
It has to do with the decay time of the subwoofer itself which is something what measured frequency response cant tell at all. Subwoofer in real use never plays one specific frequency at the time, there are always multiple frequencies and their harmonic distortion orders. Maybe thats what Matthew meant by linear behavior.
@@pulDag that’s precisely what he meant
Hang on, if Geddes uses his mains front left and front right speakers full range, then you can't use an AV receiver with his approach, because it won't send any of the bass content from front left and front right to the other three subwoofers, so none of that bass will get the multi subwoofer benefits. Right?
so am getting this right? despite all the times everyone has been told to crossover at 80 the best is to just run your mains as rull rangers and just tune your sub to match?
Linked Devices yes, so long as your mains can handle full range, your run them full range and overlap the first sub’s crossover point with the mains for better integration.
Yes definitely. The more bass sources the better.
Geddes uses "full range" speakers without any crossover because they goes only to 80Hz f3, so be carefull.
Also there is never only one solution as Matthew says in the end.
What about the 'infinity' solution of bass line , i read that putting bass speakers in line on 3/4 off the room hight cancels all roommode issues