AM I CRAZY? DIY nearfield nude driver desktop headphone concept

I think I have a crazy idea... or maybe not so crazy (but for DIY only!). Read on for details...

I've often espoused the use of a nearfield driver for the "ultimate fidelity" subwoofer. Assuming this would be used when you are seated in one place only (e.g. at the computer) for music listening, the idea is this:
  • Construct a means to place a large-ish (e.g. 12 or larger) diameter driver right behind your head or as close as possible to this location.
  • The driver is mounted in a minimal open baffle or very shallow open-rear baffle-and-2-sides frame.
  • Because of the driver diameter and the proximity of one's head to the driver, you are in the nearfield. As such, the response will be essentially the infinite-baffle response of the driver.
The idea is that the "ultimate" bass extends low in frequency, is free of cabinet resonances and small-box-distortion, and has no peaks and valleys from room modes. About the only way I know of achieving this apart from being in a very small space like a car cabin is via the nearfield method. I happen to have the perfect driver for this - a 15" free air type subwoofer with Qts=0.7, Fs=20Hz, and 15mm Xmax. If I listen to this in the nearfield the response should be essentially the infinite-volume, closed box response! Wow. So that would cover the bass nicely.

I started wondering to myself lately if this concept could be extended to the full audio spectrum, that is to add a driver on either side of my head near my ears. If the drivers are large enough in diameter, I would again be in the nearfield (up to some relatively high frequency at least) and I would be creating something like an open-back headphone but with completely open-air drivers. Is this a crazy idea? Not sure, I have never attempted something like this. I am concerned that above 1kHz or so, some odd effects from the interaction of my head and the driver (e.g. interference) will take place and the frequency response will be anything but smooth. Also, there will be no way to measure the response (I like to measure) so I will need to adjust any FR irregularities by the "seat of my pants" (e.g. by guessing).

Can anyone recall something like this - a full range nearfield "listening station"? Could this bring some real high fidelity in a DIY-only package? I might have to build a "listening throne" (e.g. a chair-and-speaker contraption) test bed.

Any thoughts on driver selection (size, type, etc) for full-range nearfield listening are welcome. What is the best way to implement this idea?
 
Hey, that's a cool product. They mention they use "tactile" (transducers) like a Bass Shaker. I'm thinking more along the lines of an actual direct radiator driver application (since I have a few of these!)...

If you are not careful you might end up re-inventing the 'egg' chair Modern Pod and Egg Chairs For a Retro Look | Decorating Room
Ah yes, maybe the wicker version... Well, no, I was thinking more like something with a baffle running from the floor up, behind my "chair" seat, and ending just behind my head. The two "arms" sticking out from there to hold drivers on either side of my head. The only challenge I see with this arrangement is that I couldn't move my head from side to side much without bumping into one of the drivers placed there... Maybe if I came up with a counterbalanced positioning system with some kind of headgear-strap contraption to keep the drivers and head in a relative alignment... See, CRAZY!
 
Hi, for my desk and workbench speakers i use 13 x 7 cm oval fullrange drivers also for the beaming they provide. Still, the remaining reflections off the walls and table help me to understand where i am and not hurt myself. What works is much determined by practic, ergonomic issues, even tho man strives for the useless, exceptional. Thy idea fits into this frame, Charlie. Uli
 
Still thinking over how to execute this concept...

I think what I would prefer to do is integrate the nearfield system into a chair like a chaise lounge, for instance something like the Corbusier LC4 chaise. I have a Wassily chair that I rarely use that I might also use. The advantage of a reclined chair is that the height of the sub, which should be behind but still near the head, is lower. This makes the height of the drivers lower and reduces the size of the base.

Once the geometry is fixed I can build the fixture to hold the sub and the two side speakers that are placed on either side of the head.

Apart from the large subwoofer that I can use for this project, I am trying to figure out what might work best for the "side" drivers. I have a pair of 3.5" TangBand full range speakers that would work, but I think that something larger woudl work better, because the nearfield extends farther out away from the plane of the driver mounting ring. So, for example, this 8" full range driver with whizzer cone might be a good option from Parts Express. Not cheap, however. :(

Then there is the small problem that this system will lack all room reflections because you are sitting in the nearfield. I think many people underestimate the importance of room reflections in generating an "enhancement" of the stereo image and increasing depth and width of the sound stage. Well, I will have to add these into the sound sent to the drivers, artificially. I could do this by mixing in a delayed copy of the sound but that would be rather crude. Instead I may put into use a venerable Sony TA-E2000ESD preamp that I have lying around. This can "synthesize" room reflections and add them to the audio. It also has a multiband PEQ as well as a mono subwoofer output with crossover (fixed at 80Hz, 18dB/oct). If the nearfield response of the drivers is flat enough, I might only need this kind of correction to provide relatively flat response from the system.

So, some food for thought. This could turn out to be something interesting...
 
The one thing that strikes me as problematic about a project like this is the issue of sweet spot. You may end up so close to the drivers that moving your head by a few inches could affect frequency response and relative levels more than you like. Making your best impersonation of a statue does not sound like the ideal way of listening to music to me...
 
The one thing that strikes me as problematic about a project like this is the issue of sweet spot. You may end up so close to the drivers that moving your head by a few inches could affect frequency response and relative levels more than you like. Making your best impersonation of a statue does not sound like the ideal way of listening to music to me...

This is true but it depends on the size of the driver. This is because the nearfield extends out from the driver a distance that corresponds to some fraction of the width of the driver where it starts to transition to the far field. If I can use two large drivers they do not need to be that close to the head, giving one some freedom of movement. In any case, this isn't a system that one would use to do anything else besides listen to 2-channel audio while lounging in a chair. The listening position is fixed, and therefore so is the listener. The advantage is that the nearfield positioning should essentially eliminate all room interaction (for better or worse) much like a good headphone set, but can include real tactile bass that the whole body can feel from the subwoofer. I'm hoping that with larger drivers the frequency response could be flatter than many headphones can achieve because of the lack of a sealed cavity between the driver and the head.
 

Intrio

Member
2016-05-29 12:56 am
ipad behind head as a prototype.

I just signed up on this forum for this topic.

You're not crazy. Though it might not have to require nude or big drivers to work well enough.

This may or may not work for you, it doesn't for my audioloving neighbor.

I discovered by accident, with an ipad on the couch and me on the floor using the couch as a head rest, that if an ipad is positioned about a hands distance from *behind*the head, forming somewhat of a triangle. Speakers pointed to the back of the ears, that it produces a sound stage significantly better than my fancy sennheiser and genelec studio monitors, an illusion hanging in front of me.

Doing some research, the ipad speakers are full range, point source, decent magnet, and 3 watt ish adequate power for that space between headphone and near field.

Even with average encoded youtube music videos I'm hearing things I've never heard before on CD, in how it's mastered, though the sweet spot is indeed small about hand sized wide and high. But...when it's on, it' so worth it for me I'd sell my sennheisers! (which give me headaches wearing them with glasses)

As the ipad speakers are about 2 inches apart, and create a venn like diagram of where the left/right audio overlap, where the head is the middle and basically blocks oppossing audio.

It works better if you put a divider between the speakers and head to help deal with lower frequency crosstalk cancellation, as those are bending around the head.

I think part of the effect is when it's on a flat surface acting like a horn, but the spatial aspects seem independent of that. As it's close and if the head is connected (say by couch foam) to the ipad there is a tactile effect and if ears are plugged there's an inner sensation effect typical of live audio (typically missing from headphones listening)

It also works reflected for me. Like put a foam pad on the floor, lie down staring up at the ceiling, and then the ipad on a pillow pointing down (if you have hardwood), reflecting up into the back of your ears.

Wierdly direct audio (ipad in front) doesn't product the same almost holographic spatial detail for me.

I ordered some ipad replacement speakers trying to integrate it into a zero gravity like recliner floor chair , but sadly they can't be driving by a conventional amp.

Was hoping others might have some suggestions as to alternate ways to power or similar sized drivers that are equally small/powerful.
 

pelanj

Member
Paid Member
2008-07-17 8:47 am
Hořovice
I had a similar idea this morning. I am glad I hit the search button first:) I have a chair in a corner where I listen to headphones. To move the drivers out a bit so one does not have to wear the headphones sounds doable. Ideally, mounted to the rotating chair as anything placed on the floor would be tripped over by the kids or the wife:)

So I imagine a pair of small full range loudspeakers mounted on the handles in a similar fashion as backview mirrors on a motorbike with an optional subwoofer mounted on the back of the chair. I have some small full rangers and a 3D printer available. I am sure my wife will love the looks:)
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Wanting to give Charlie's hare brained idea a try I had envisioned building a giant rig with multiple drivers and series parallel wiring, etc. But this morning I thought "Hang on, why not just hold up the drivers and listen?" :xeye:

Well yeah, it sounds about how you might expect. Bigger is defiantly better for tonal balance because the small drivers have no bass until they are within a hands width of your ear. But once the speakers get close, they just sound like headphones with the same inside the head image. They sound like very open, clean headphones without much bass. For sure the 8" drivers had the best bass, even tho they aren't great drivers overall.

Getting the drivers out to about 1/2 arm's length helped imaging and getting the sound out of the head. All the way out at arm's length was getting close to a normal sound stage, but lacking bass, of course. The little oval speakers where the best for imaging, and not bad for bass. Raising the drivers above head level results in more top end, below head level more bass. I found the normal stereo triangle best, off to the sides positioned in front of the ears sounds like headphones, too close to center sounds mono.

You would want a woofer with these for sure, there just isn't much bass unless you are wearing the drivers as headphones.

TL: DR This Sounds about like you'd expect. Close to the ears gives more bass. Bigger is better, add a sub.

Fullrange drivers from left to right. GRS 8", FaitalPro 4", Vifa 3.5" Brazilian oval TV speaker.
 

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PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> small drivers have no bass until they are within a hands width of your ear.

Within a baffle-width of your ear.

If no added baffle, then frame width.

For the small range of speakers you tested, no great difference.

Hold out a couple of 18" or 30" speakers. They do not have to be hand-width near.

The Eight in a 2-foot square of cardboard can be a foot (not just a hand) away.

Try 1-inch speakers. Need tiny hand-width or maybe thumb width.
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Yes, about a frame's width. Closer than that and they actually have decent bass.
Sometimes you'll see people post OB measurements that look a little too good in the bass. Too good until you find out the mic was 6 inches from the woofer. ;)

What did surprise me was that only the long oval TV speakers could project any depth behind their distance plain. Not sure why that was.
 

Hearinspace

Member
Paid Member
2008-06-03 5:18 am
In my uneducated view, No, you needn't. I had the opportunity and I found wearing them uncomfortable enough that it took an effort to stay focused on the sound and the sound wasn't worth that effort.
Though they were a novel design (and very well built), having them on felt just as novel . . . . . . a little like a cross between Dumbo and a techno flying nun. : )

They were considered very high end by some though so what do I know?