Which speakers have rear firing speakers and how do they sound?

What do you mean? Rear-firing? Or di-pole?

he means like this

https://www.hifizine.com/2010/06/the-controlled-pattern-offset-bipole-loudspeaker/

My former Snell Elll speakers had a rear facing tweeter. There was a control for that driver’s volume. I didn’t notice much difference with that knob. 

I have zero experience with that particular speaker but do have some experience with bipolars (I wrote the article kenjit linked to). 

Assuming good execution, I think you can expect rich timbre and a bit more spaciousness than normal.  The sound will be more detached from the speakers than normal; it will sound less like the sound is coming from two boxes.  Also you won't have much in the way of baffle step issues, this because the rear woofer's output wraps around and helps the front woofer right about where the front woofer starts baffle-stepping.  

The upwards angle of the rear facing drivers makes me think they can be placed closer to the wall than most bipole and dipole speakers.  Ime what you don't want is, for the reflection off the wall behind the speakers to arrive too early.  The upwards angle helps to increase the reflection path length by including a bounce off the ceiling.  I do that too sometimes, but not in exactly the same way. 

Duke

I’m curious if you may be referring to speakers that have tuneable rear tweeters?  My Von Schweikert VR 4 JRs have a single rear tweeter per cabinet that has a volume control. I use it for recordings in huge halls to capture more ambience. It works well. A rear firing woofer is often a passive woofer driven off the excursion of the primary woofer. Both can be beneficial if designed properly 

Yes, tunable rear tweeters and or speakers, to give a more live feeling to the music.

The Vandersteen 5a, 7 include a switchable rear firing tweeter w level control for over damped rooms and  recordings lacking much ambient hall / venue information. In this time and phase accurate design, the rear firing tweeter is 100% distortion, but in some cases pleasing.

Isn't this the core issue that people debate

A. Box speakers with front facing speakers are "more accurate - distortion free.

B. Electrostatic, bipolar, open baffle and omni speakers are less accurate with sound coming not only from the front but the back or top - e.g. have distortion built in

But in reality, when you hear live music, there is all sorts of distortion in any hall, though typically the sound is better in say the orchestra at the Beacon in NYC or the Capital in Port Chester than in the balcony. 

So, jump in and tell me how I'm wrong, but my experience is that speakers that are designed to replicate this kind of distortion sound more live. E.g. the Thiel, KEF, Canton and Proac speakers I've owned sound great but less live and less engaging than electrostatics or omni or bipolar designs. 

So, in search of the most live sounding speaker - suggestions?

Tomic601 wrote: " ... the rear firing tweeter is 100% distortion, but in some cases pleasing."

I can certainly understand how the energy going off in other directions from any polydirectional speaker can be interpreted to be "100% distortion". It’s not on the recording, right? It just adds more of the room’s sound to what was on the recording, right? And "distortion" is certainly how a measurement microphone would see it!

Let me suggest looking at this from a completely different perspective, and along the way we will discover why this "distortion" is "in some cases pleasing".

There is a vital difference between ears and microphones: The ear differentiates between the first-arrival sound and the subsequent reflections, and a measurement microphone does not.

So let’s approach speaker design from this perspective: Let’s see design for the ears instead of for microphones.

In any non-anechoic space, the ear detects two events: The first-arrival sound, and the reverberant sound (the reflections). What we actually PERCEIVE is a combination of these two events. And the less discrepancy between the two, the better the perceived sound quality.

So if we are designing for ears instead of for test instruments, we would want the reflections to sound a lot like the first-arrival sound. Since most speakers beam in the top end, this can mean adding a rear-firing tweeter to put a bit more top-end energy out into reverberant field. Fortunately the ear is not very sensitive to time coherence in the reverberant sound, so it doesn’t matter that the reflection path for the rear-firing tweeter is different from the reflection path for the main tweeter.

Thus while that rear-firing tweeter’s contribution looks like distortion to our test instruments, it results in a more natural sound because not only can the ears tell what is first-arrival sound and what is reverberant energy, but also they BOTH matter.

So, assuming competent implementation, is the rear-firing tweeter’s contribution a "distortion"? In my opinion, only if we listen through test instruments instead of through ears.

Just for the record this post is by no means a complete examination of the subject, and I have nothing against microphones as design tools.

Duke

Duke...nicely thought out BUT in the case of an acoustic event recording in the space a nicely placed microphone captures first arrival and subsequent arrivals, that information IS encoded in the wave form over long periods of time, well past first arrival.  So if the bounce is already in the waveform, why add another off the back wall ? I have in 3 rooms now tested the rear tweeter on the Vandy 5a, while I dont generallt prefer it, there are some combinations of room / recording where it sounds better. In general overdamped rooms and IMo over mic’d DG recordings. In those rooms a 2 L suffers w rear tweeter on. Just my buck fifty, but this is psycho acoustics at it’s best, imo

best and again congrats on the Subwoofer award, cool

I should clarify, a 2L “ the Nordic sound “ recording, but substitute in any good hall ambience / instrument balance recording, of which there are multitudes...

@tomic601 wrote: " Duke...nicely thought out BUT in the case of an acoustic event recording in the space a nicely placed microphone captures first arrival and subsequent arrivals, that information IS encoded in the wave form over long periods of time, well past first arrival. So if the bounce is already in the waveform, why add another off the back wall ? "

Excellent question, goes right to the heart of the matter. Unfortunately my answer is not going to be as succinct.

When we listen to recorded music, there are TWO venues in play: The FIRST venue is what’s on the recording (whether it originated in an actual acoustic space or was synthesized by the engineers). The SECOND venue is the room we listen in. At the risk of oversimplifing: FIRST venue GOOD, SECOND venue BAD.

So we want to the first venue cues to be effectively presented, and the second venue cues to be as innocuous as possible.

An effective presentation of the first venue cues would have them come from all around, which implies having a lot of reflections. Also those reflections should have a spectral balance that mimics the first-arrival sound - when they do not, they are more likely to sound unnatural.

So, by correcting the spectral balance of the reverberant energy via a rear-firing tweeter, we are making the second venue cues less obtrusive.

But, we need to look at the time domain as well. The relatively short reflection path length of that rear-firing tweeter makes is an early reflection. And we know from the experience of countless Maggie owners that rear-firing energy sounds good when there is a long time delay, and bad when there is a short one (clarity is degraded and second venue cues are emphasized). So with speakers close to the wall a rear-firing tweeter may not always be a net benefit.  Having spent a fair amount of time working with secondary arrays of drivers, I try to aim them in a direction that results in a relatively long reflection path length.

This long path length for the additional reverberant energy has an unexpected benefit: It makes the second-venue cues weaker!

Let me explain: The ear judges the size of a room by the time between the first-arrival sound and the "center of gravity" of the reflections. By injecting additional relatively late-onset reverberant energy via long-path-length reflections from additional drivers, we are pushing that center of gravity back in time, and we are making the second-venue cues more ambiguous. As a result the "small room signature" imposed by the second venue becomes less obtrusive, so it does not dominate the first venue cues as much as before. We hear more of the soundscape that is on the recording and less of whatever room we are listening in.

I don’t really expect you to believe me because this is a highly unorthodox idea being described by the guy who has a commercial interest in it. So here is my question to you: Are there any audio shows that you sometimes attend? I usually only do about one big show a year, but maybe just maybe we can cross paths at one.

Duke

I don’t disagree, the 2nd room, 3rd room, listening room all add.
even in the control room listening in the near field, there is bounce off the board, etc. mastering rooms not usually near field, etc...

I did some experiments with trying to replicate ratios along the chain, for example if the stereo pair was 9’ in the air and 7’ from small chorale and ... x you get the idea ( but the math is complex and results indeterminate, but think this is but one reason why stereo images vary in realism so much

happy listening 

Lots of good thoughts and comments. Question is

Which speakers actually get it right accomplishing both goals of
A. providing accurate sound replicating the studio recording with decent imaging
B. provide a sense of realism and space to give that you're in the room feel to the music

Possible solutions include:- Electrostatic and planer speakers like MLs, Soundlab, Magepan, etc
- Omnis like Ohm Walsh, or hybrids like Decware's HR-1
- Open baffle speakers like Spatial Audio's
- More traditional box speakers that include a rear or upwards facing tweeter and or midrange 

And of these - which works in more rooms than not? E.g. doesn't need to be placed 5 feet into the room and isn't the size of a barn door or cost as much as a new car?

Wow.. I know that's expecting a lot but interested in. your suggestions.

I have Vandersteen 5A’s that have a rear firing rear speaker that can be turned on/off via a volume control. Clearly it sounds best off as recommended in the owners manual. With the rear speaker operating, the sound is more diffused/confused.

@cdc2


"Which speakers actually get it right accomplishing both goals?"

I'm guessing that most of our experiences have been that all of the discussion regarding speakers and rooms is 'theoretical'...UNTIL...we get the speaker being considered in our own specific rooms playing with our equipment and our music.  When we begin tweaking the speaker location/position, we begin to understand...that it is very difficult to identify the 'one size fits most' loudspeaker....especially when you add the placement challenges of many rear firing loudspeakers.


There are plenty of people that own all of the speakers listed above and love them.  And there are plenty of people that have tried them and moved on.

Let me just pick one 'usually agreed upon' example.  Magnepans in the right room, with the right amplifier, the right positioning and the right type of music can sound shockingly real (live music)...but move them a little bit, change the amplifier or change the type of music and they seem to lose that magical quality.

So, where does that leave us.  I suspect that there are two solutions which from a practical standpoint, people often end up with:

First:  pick the loudspeaker that has the most positives and fewest negatives in your room with your equipment and music

Second:  have two systems in two rooms that have different strengths and play the one that suits your mood at any given time

Cdc2 wrote: " in search of the most live sounding speaker - suggestions? "

Cdc2 breaks it down for us: "Which speakers actually get it right accomplishing both goals of

"A. providing accurate sound replicating the studio recording with decent imaging

"B. provide a sense of realism and space to give that you’re in the room feel to the music."

And cdc2 takes the real world into account: " which works in more rooms than not? E.g. doesn’t need to be placed 5 feet into the room and isn’t the size of a barn door or cost as much as a new car? "

I am a SoundLab dealer, and imo SoundLabs set up properly do a very good job of recreating a "you are there" type of experience. But accomplishing that does require placement a good 5 feet out into the room... they are approximately the size of a small-to-medium barn door... and it depends on the car...

My mentor in loudspeaker designer is Earl Geddes. Earl is a master of ultra low coloration and room-friendly design.

The SoundLabs (when given their 5 feet of real estate) create more of a sense of being enveloped in the acoustic space of the recording than Earl’s speakers do. Earl’s are more dynamic and are every bit as low in coloration and vanishing as the apparent sound source.

I build speakers inspired by Earl’s design principles, and then I add additional late-onset reverberant energy via drivers aimed to bounce off the wall behind the speakers, and then off the ceiling, before reaching the listening area. So conceptually similar to what you saw with the BMC Purevox, except that my rear-firing drivers are not identical to the front-firing ones, and they are mounted as close to the floor as I can reasonably get them. Also, my rear-firing drivers are level-adjustable, as we found there to be a "sweet spot" in loudness relative to the front-firing drivers, and dialing it in for different rooms requires some adjustability.

One difference between what I do and all of the speakers you listed above is, my speakers use horns. Low-coloration, constant-directivity, waveguide-style horns. Their pattern control helps us minimize early reflections, and it is primarily the early reflections which superimpose a "small room signature" atop the spatial information on the recording. Of courese if my horns have audible horn signature then all of this is of academic interest only.

I am NOT going to claim that my designs do what you want - that’s a subjective evaluation and I’m the last person in the world in a position to make it without bias. Instead, I’ll say that I think my goals are similar to yours, and that I’ve tried to incorporate design elements that at least theoretically might work.

My website is being revised so contact me if you’d like a link to a recent show report with some good pictures.

Duke