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Which subwoofers for sound installation

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sonic_traveler View Drop Down
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    Posted: 14 May 2022 at 12:55pm

Hello everyone,


For my graduation project, I am working on an interactive sound installation, and am now looking for the right speakers. Maybe someone of you could help me out with some questions I am facing? That would be pretty amazing . 


The installation I am planning is being activated by around two to five people using pulse sensors. The sensors are set up as midi controllers in Ableton Live and the signal translated into sound. As the idea is that people can hear and feel their own and other people's heart rhythms, I would like to work with low frequencies to achieve a chest pounding effect (around 60-80Hz). I already figured that subwoofers might be the best solution, as they focus on low frequencies and display them in the best way possible, compared to mid-range speakers. But researching into subs I found myself in a jungle of possibilities, in terms of technology, design and price.


Another problem I am facing is the question: how many subs do I need, which size and how do I need to place them? My first idea was to have a sub for each sensor, so that the installation starts with displaying everyone's rhythm individually and after that, merging all sounds on all subs, creating an immersive soundscape. But I guess it is quite tricky to position them in a way that they do not interfere each other, right? Or is this something I could adjust by changing their angels a little, so they do not directly face each other? Or is it even possible to have subs that just end at some point, so they kind of don't touch each other?


Also, I will probably have my exam presentation in an open space like an industrial hall or something like that. Therefore, even though I will be limited to a space of 6 to 9 square meters, I will need to consider the space around and its acoustics that I do not know yet. I also have the possibility to build a little room around it or use acoustic panels. Researching the size of the driver and space I will need, I figured, with an 12-inch subwoofer, I reach 1.25 cubic feet. This feels like nothing to me, but might also solve the problem of interference? But is this the same with all kinds of subwoofers? I think especially if I use several speakers they shouldn't be too big but strong enough to create the tangible feeling in the body. Would 5 x 12-inch speakers, placed 2,50 apart from each other, be enough? 


Looking at the possibilities to access speakers, buying, renting and building them could all be an option for me. Even though I am still not so happy with the idea of rental. By looking into different opportunities of speakers especially in the DIY area, I found the direct sub, the scoop, the folded horn and the tapped horn. As I understood might folded horn and tapped horn be the best in quality as they have more space to amplify the vibration, but are also more difficult to build and probably more expensive. A guy from a music store recommended me to rent two direct 18 inch subs and 5 mid-range top speakers, while someone from Thomann Music recommended me to get five of these https://www.thomann.del/ld_systems_sub_88_a.htm?ref=sea_rslt_LD%2BSystems%2Bsub%2B88_244144_0_1 - active 8inch subs which are unfortunately a bit too expensive for me, especially without knowing if they would work as I want them to.


So that's more or less what I have now. It would be amazing if someone could help me out .


THANKS a lot. Best, Laura 


A sketch:

https://drive.google.com/file/d/1I4GV56ZWPSiCOpiP3h1z6Fb2ezpwHh7u/view?usp=sharing



Edited by sonic_traveler - 14 May 2022 at 12:55pm
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Lucasdude View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 1:12pm
That's an interesting project! From your sketch are you suggesting that each subwoofer is only connected to a single HRM, or all to all?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sonic_traveler Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 1:32pm
Originally posted by Lucasdude Lucasdude wrote:

That's an interesting project! From your sketch are you suggesting that each subwoofer is only connected to a single HRM, or all to all?

Hi, thanks for your reply. I hope I understood it right. With HRM you mean something like a mixer or interface? Because in the sketch I didn't drew it, but the idea was to use a digital mixer with at least 5 outputs yes, so I could manage each channel separately but could play them at once as well. Is that what you were asking?

Edited by sonic_traveler - 14 May 2022 at 4:42pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 2:26pm
Just re-read the post... still. Ever heard of a thing called "Feedback" ? Like with drum triggers you are likely to  have problems with false triggers , those sensors will pick up more than heart beat (unless they are electro cardiogram . What are the sensors your using ? Im getting more enthusiastic by the second) have you tried this at low level yet?
In the very centre of any listening space is a dead spot where bass will not occur due to room reflections and the opposite happens next to a wall where you will get more bass.
Best place to put any bass speakers is in one corner of a room only. If your going for immersive sound maybe have one speaker in each corner ,like you say,  fed of sub groups or aux sends  on a desk  and route the individual sounds to one speaker only (Hmm this sounds like an interesting project now!where do I sign up?) Subs in freespace will be very hit and miss at the best of times  although you will not have cancelation ,you will also not get as much volume. If your in a large closed space you will get a lot of resonant reverb that will destroy any directional imaging. The whole thing is entirely dependant on the listening position  and there can only be one !........ ATMOS is pointless!... discuss....(and really......
"couldn't we just like... use headphones?")


Edited by Tinnitus Rex - 14 May 2022 at 3:13pm
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sonic_traveler Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 3:23pm
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Edited by sonic_traveler - 14 May 2022 at 4:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sonic_traveler Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 4:32pm
Originally posted by Tinnitus Rex Tinnitus Rex wrote:

 Just re-read the post... still. Ever heard of a thing called "Feedback" ? Like with drum triggers you are likely to  have problems with false triggers , those sensors will pick up more than heart beat (unless they are electro cardiogram . What are the sensors your using ? Im getting more enthusiastic by the second) have you tried this at low level yet?
In the very centre of any listening space is a dead spot where bass will not occur due to room reflections and the opposite happens next to a wall where you will get more bass.
Best place to put any bass speakers is in one corner of a room only. If your going for immersive sound maybe have one speaker in each corner ,like you say,  fed of sub groups or aux sends  on a desk  and route the individual sounds to one speaker only (Hmm this sounds like an interesting project now!where do I sign up?) Subs in freespace will be very hit and miss at the best of times  although you will not have cancelation ,you will also not get as much volume. If your in a large closed space you will get a lot of resonant reverb that will destroy any directional imaging. The whole thing is entirely dependant on the listening position  and there can only be one !........ ATMOS is pointless!... discuss....(and really......
"couldn't we just like... use headphones?")

Hey hey :), thank you for your comment. 

Yes, indeed, I have heard and experienced feedbacks ;). But it's a bit hard to understand it's meaning in the context of my project Unhappy. Do you mean feedback in the sense of the sensors or the speakers? Maybe you have to elaborate on it a bit more? 

I've first made some experiments with a stethoscope and a lavalier mic but giving the circumstances that in a live performance set up is a bit difficult to handle other incoming sounds I switched to the simple pulse sensor. And it works. I created already a setting with four sensors, each one connected as a midi and each midi having their own output / speaker. For that, I used tactile transducers with 40W. It worked, but the signal wasn't that accurate indeed. But the reason was that every person would have need to have a different threshold within the code, and after trying some hacks with setting up global / local maximum and minimum this still didn't work. So I went for the DFRobot Gravity Heart Rate Sensor, which is a digital sensor and therefore more accurate. I know it is not exactly the heartbeat, but at least it detects the rhythm of the heart pumping the blood through the body. In my case it was necessary to find a way, so people can attach the sensor easily without using electrodes or placing it on weird parts of the body, if you know what I mean ;). Therefore, I think this is the best solution for now. Or what do you think?

What do you mean with low level? Like low frequencies? Yes, I've tried it with a stereo of a friend. I guess it's mid-range speakers. Te result comes very close to what I want, but it's still not enough to create a strong feeling in the body :).

And thanks, that's also what I've heard a few times already. My question is now, do I need to create a room for my installation, or does it have a different effect if the space around is open? Maybe I just need to test this. Anyway, what do you mean by this: "fed of sub groups or aux sends on a desk and route the individual sounds to one speaker only" because as I understand you mean I should use a mixer that manages every sub as an individual channel? Because that's also was what I was thinking of :).

And thank you for being so enthusiastic :). It's great to hear that my idea sounds interesting. Unfortunately, no signing up yet, but maybe I can put it somewhere as an open source project as soon as it's done. We can keep in touch if you want. 

With ATMOS  you mean Dolby Atmos?

And no, unfortunately, headphones wouldn't work for this project. They would never create a chest pounding effect. Also, it is nice if the rest of the audience can still listen as well.

Thanks a lot.


Edited by sonic_traveler - 14 May 2022 at 4:42pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 5:22pm
I would just point out that "chest pumpumg bass" will definitelyfeed back into your sensors as your body and the sensors  will become the microphone and intern trigger the chest pumping bass into a coninuous noise/trigger signal. Rather than  "chicken and egg" ,you get a loads of unstoppable chicken egg smoothie........if you know what I meanConfused Also sub bass is not directional, but it will destructivly cancel out if it meats itself.
 I have pondered ideas for people where the idea is good but the practicality and realtime  physics do not allow it to work. It would be better to record the thing you want quietly and to your satisfaction and then play it back at volume,  your half way there but alas the other half adds maybe 10% to the actual experience and is exponentualy more difficult  to achieve ..(thats why big stars often mime ..no shame , art is just theatre after all)
Yes dolby atmos, .....................but thats another thread and I would hate myself for starting that one !! ...or would I? ..he he he
 check these out, they look like fun
https://www.thomann.de/gb/eich_amplification_bassboard_m.htm


Edited by Tinnitus Rex - 14 May 2022 at 6:52pm
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sonic_traveler Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 7:11pm
Originally posted by Tinnitus Rex Tinnitus Rex wrote:

I would just point out that "chest pumpumg bass" will definitelyfeed back into your sensors as your body and the sensors  will become the microphone and intern trigger the chest pumping bass into a coninuous noise/trigger signal. Rather than  "chicken and egg" ,you get a loads of unstoppable chicken egg smoothie........if you know what I meanConfused Also sub bass is not directional, but it will destructivly cancel out if it meats itself.
 I have pondered ideas for people where the idea is good but the practicality and realtime  physics do not allow it to work. It would be better to record the thing you want quietly and to your satisfaction and then play it back at volume,  your half way there but alas the other half adds maybe 10% to the actual experience and is exponentualy more difficult to imposible to achieve ..(thats why big stars often mime ..no shame , art is just theatre after all)
Yes dolby atmos, .....................but thats another thread and I would hate myself for starting that one !! ...or would I? ..he he he
 check these out, they look like fun
https://www.thomann.de/gb/eich_amplification_bassboard_m.htm

Ahh, that's what you mean. True, I actually did not consider this. And I definitely don't want chicken egg smoothies ^^. 

I think of the following options now:
- planning and controlling the signals live, so that they are never playing all together at the same time
- and/or downsizing the amount of people interacting with the installation, for example just one or two people
- having one person's pulse sensed outside the installation, while the rest of the people can experience the person's heartbeat inside, while using subwoofers.

I also see the option to do some tests again with a home stereo system where 60-80Hz are at least a little tangible, to see what the signals do regarding feedback. Because somehow I am also curious to see if this randomness of feedback signals and noise might turn into synchronization after a while? I just had to think of dancing in a club for a while, where the heart rate also adapts to the bpm of the music at some point. Just wondering. Maybe it's a stupid thought.

The recording part is also a good hint, I think, because what I could do would be to play the heartbeats individually and at the same time record them in a loop. After playing everyone, I could just play all recorded loops together. Could definitely work, but I am not sure if this is what I want.

And no worries, if you think it is not necessary for my project we don't have to get into it and if so, I could also have a look myself ;).

Wow, yeah, that's a fancy thing Big smile. It is made with tactile transducers, right?

Thx a lot!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2022 at 9:31pm
I looked at your drawing and at sub 60hz you cannot distiguish where the sound source is and the more speakers you have the more they will just cancel each other out. Also having the listening position in the centre of a space there will be the worse listening possition possible for bass . please do watch this ,its important
 Those floor transducers may be hire-able and they would  elliminate the problem because
contrary to most peoples understanding "You dont hear sub bass , you feel it", and you have to get it to resonate you at your resonant frequency ( or you lung cavity frequency)
You would be very supprised how good  those transducers are in action .. they are used by drummers and bass players preciely because it is imposible to hear bass when your close to it as each frequency has a different accoustic wavelength.
Forget speakers ,you will create more problems than you will solve , transducers are WAY better because they use conduction rather than radiation . and only the people experiencing the instalation will perceive it ,win win
 Having battled acoustic feedback for most of my sound career, there is an art to it ,
its "like a snail crawling on the edge of straight razor!" (Apocalypse now)Cry
Obviosly the people experiencing this cannot be the sourse of it , or it will give them a heart attack by phase canceling their heart (Dont have nightmares ,just a thoughtBig smile)


Edited by Tinnitus Rex - 14 May 2022 at 10:01pm
"couldn't we just like... use headphones?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2022 at 12:44am
You may not be happy with the idea of rental but with the multiple sub approach you are going to run into budget problems. 5 cabinets with amplifiers that can produce the impact you want will cost a conciderable amount, and if you only want them for a single project there seems no point in buying or building.
Bass frequencies from a single cabinet are not directional, so can not be steered by rotation. But bass from multiple cabinets will give interference patterns. They don't cancel but will have various summation and null points throughout the soundfield. This assumes that the speakers have the same bass signal which is probably not the case here.
Multiple speakers are are usually coupled together to produce a bass response with the least amount of interference for the listeners. This can be as simple as grouping all the speakers together to create a even dispersion.
When bass speakers are distanced from each other the soundfield is usually controlled by the timing of the signal using a digital crossover.
However If you can keep all the signals separate the result is far more chaotic and natural. Think of the difference between one bass drum through multiple speakers which would give fixed null positions, and the different impact of 5 separate drummers where each transient would be different in time and phase.
Subs have a limited pass band. A lot of the information in an audio signal is contained in the higher frequencies which convey the harmonics and directional information. So I would think you would need to concider if each speaker position actually requires to be full range.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2022 at 1:06am
I agree with Xoc1, just rent in a bunch of powered 15” or 18” subs and spread them around the listening area - if you’re bussing the individual people to different speakers (or a mix thereof) instead of all people to each speaker.

Even if the latter was the goal, you can use this with an external (rented) DSP or even a multi-channel soundcard and delay VST assigned to each channel in something live Waves MultiRack. A £30 measurement mic is ideal, but any microphone will get decent enough results:
https://www.andyc.diy-audio-engineering.org/mso/html/

For non-sub content, your uni probably has a bunch of Genelec or similar small-format monitors that you can use for free, if it has a music focus of any kind.

You're looking at a few hundred quid to rent for a week versus thousands to build a decent setup from scratch. Especially if you wanted to do something with a lot of tactile transducers. Using those for a large area is a *very* different thing than sticking one to a drummer's seat. I've got four Powersoft Mover sat in a box because the budget to apply the design at scale wasn't feasible. That was for an area smaller than what you're intending to use, and the Mover are the most powerful tactile transducers by far at 20kN per unit.

I believe the original BodySonic dancefloor in Fabric nightclub uses at least 64 of a custom Beyma tactile unit, alongside the six subwoofers. It’s not a massive area.

Subs in one location is actually a pretty terrible idea if you’re after the least spatial variance across the sound field.

I’d ignore comments from people who clearly haven’t studied the applications of spatial sound via the various methods, such as VBAP, Ambisonics, WFS and all the stuff in-between. Respected and smart engineers such as Earl Geddes & Floyd Toole are huge advocates for multiple subwoofer deployments, with good reason.

You can also get great results with just two subs:
https://www.andyc.diy-audio-engineering.org/mso/html/reference-manual/tips_tricks.html#how_many_subs

Plenty of links on the MSO site for further study - which you can cite in your dissertation more easily than "Random Internet Guy"

Edited by toastyghost - 15 May 2022 at 1:18am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2022 at 5:54am
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