Open speakers? - Head-Fi: Covering Headphones, Earphones and Portable Audio

Joe Bloggs · 02-01-2002, 02:30 PM

Hey, if open headphones are such a successful design, why don't we have open speakers too? Like, three-way speakers with just the minimum structures required to hold the drivers at the right heights and maybe just a plastic / wooden frame to enclose the drivers and prevent damage.

Braver · 02-01-2002, 02:47 PM

because it would reflect off the walls and create havoc I guess. open backed speakers in a big field might work tho.

aren't Magnepan electrostats open backed tho?

Joe Bloggs · 02-01-2002, 03:07 PM

Dipole speakers shoot right toward the back too

Neruda · 02-01-2002, 03:40 PM

Speakers are different in many ways. for one, most speaker drivers need to be in an an enclosure of a certain volume (whether or not it's ported) to help reinforce bass. However, there are a few types of speakers that I believe fit your idea: infinite baffles and open baffles. Some drivers are built specifically for these types of systems.

however, one f the main reasons to use an open headphone is to improve soundstaging and "airyness," but speakers can do that regardless. (Well, I suppose that sort of depends on the speaker. it does with headphones too for that matter!)

Joe Bloggs · 02-01-2002, 03:54 PM

Originally posted by Neruda
Speakers are different in many ways. for one, most speaker drivers need to be in an an enclosure of a certain volume (whether or not it's ported) to help reinforce bass.

Is this quite ideal? I don't understand this reinforcement thing really--how do you design the enclosure to reinforce certain frequencies? In physics terms if possible

And wouldn't the resonance from the enclosure be out of phase with the sound produced directly from the driver?

And sorry, I can make absolutely nothing of the pic you posted, it looks like a wardrobe to me

Can you explain what it is?

setmenu · 02-01-2002, 08:00 PM

There are also hybrids like Martin Logans to consider, they have
open electrostatic panels for mid and top frequencys and an enclosure for a moving cone bass unit.

Xevion · 02-01-2002, 08:52 PM

You can actually get some open dynamic speakers too!

The Legacy Audio Whisper is the most open dynamic speaker I have seen short of an electrostatic.

The woofer in the box is a passive speaker, it is actually there to dampen the bass going the wrong way, or something like that.

gerG · 02-02-2002, 12:08 AM

There have been lots of bipolar (open back) designs over the years. Magnaplanars, Acoustats, Martin Logan, Carver, Apogee are planars. Infinity had a beautiful looking system using cone drivers.

Problem is that as the wavelength gets longer the evil wave from the back starts coming in phase with the good wave from the front. This results in a 6db/octave rolloff below the wavelength corresponding to the baffle size. In short, wimpy bass. That is why the hybrids exist (conventional cabinet for the bass section).

This isn't a problem in headphones. The whole situation gets turned inside out (visualize that one a couple of times) and now you are isolated from the evil wave by the ear pad, unless you have K1000s. In that case the proximity of the good side allows for reasonable bass response, but they still roll off a bit early. I will admit that I have tried a foam surround for my K1000s, and bass was enhanced dramatically. Getting them closer to the ear also helps. That experiment is incomplete.

As for the higher frequencies coming out of the backs of the speakers, it gives a sense of spaciousness and air. Some like it. I don't. I keep trying to figure out a way to get rid of the back blast off those Martin Logans, because I love them otherwise.

There are also Di-polar speakers out there. They add extra drivers on the back of the cabinet to get a similar effect. Bose 901s are the extreme example.

gerG · 02-02-2002, 12:12 AM

Xevion, if you can figure out how those Legacy Whispers work please clue me in! I read Bill's explanation a while back, but there were some details missing. I hope to drop by his shop next time I am in the area and talk to him about it.

gerG · 02-02-2002, 12:16 AM

Ooooh, I forgot to mention the GMAS (Great Mother of All Subwoofers) that was around 10 years ago. I can't remember who made it (Paradigm maybe?) but it was actually a bipolar subwoofer. They overcame the rolloff with equalization, I think. Must have resulted in som HUGE cone excursions. Anybody get to hear one? It is one of my favorite names in all of audio.