Why are closed cabinet speakers required to be away from the back wall?

This photo begs for a caption of "when in doubt, pull them out"...

I also like the look on her face that says "Am I allowed to touch the vinyls?"

 

More like "People are going to believe this Code Acoustics system is working without a single cord in sight?"

 

What cord's?

 

It's affected by standing waves which reverberate back and forth in your room. I don't think porting is the main issue because this could be bass coming from the front as well as back of your speakers

 

I don't think that we disagree here at all.

Most home stereo's from the late 50's and 60's were consoles and not separates. They were usually found in living rooms, which were more spacious than an average English row house of the period. Couple that with the fact that our homeland was not involved in direct military hostilities, we emerged from WWII with our infrastructure intact and in far greater economic shape than in the many parts of the rest of the world in general.

After the war, we had housing boom's and baby boom's. Although we only accounted for less than 10% of the worlds population, we produced about 50% of the world's manufactured goods. We liked "Ike" and we were a wealthy and prosperous nation again.

Look at the huge American sedan's from the late 50's and early 60's, see how huge they were as compared to cars that were manufactured overseas.

We were building bigger and bigger homes, with larger family living spaces.

Wharfedale speakers were already being manufactured in England, they set up a plant in NY to deliberately manufacture larger speakers than they sold in England and were designed to produce more bass. They have 12" drivers, something that I have never seen in a "BBC" inspired type monitor speakers like they used in England back then. The cabinets were also larger than the typical speaker made in England at the time.

Americans have always liked big bass and I think that having generally larger listening spaces, needed more and better bass to pressurize a room.

British houses are generally smaller than in the U.S., so their speakers are generally smaller than the "vintage" speakers of yesteryear. Today, most homes with flat TV screens are lucky and proud to have sound bars.

Remember, that Splendor makes larger speakers today then in the vintage days. So do others. I have never had the pleasure to listen to Splendor's, but after reading your comments about their performance, I would very much like to hear them.

My comments about speaker placement were speaking about the effects, mainly from bass 300-Hz. and below. There are intended to simply explain what happens, in the physical world when you place a speaker in different places, nothing more.

Simply put, imaging and soundstage are but two of the many characteristics, that we can associate with speakers.

For the best imaging, I would consider a point source or as close to a point source as possible, such as a bookshelf speaker on solid stands, or by hanging by chains from the ceiling, which, under ideal conditions, would be about 12' high, or more, so as to avoid first reflections off of the ceiling. Likewise, I would place the speakers 4' to 6' from any rear boundary wall or side boundary wall. Ideally (depending on the speaker) they should be positioned about 6' apart, give or take.

There should not be anything in between the speakers, nor anything on the boundary walls around them.The listening position, would be close to nearfield, about 4'-6' from the speakers.

I don't necessarily support positioning speakers in corners, for one main reason, which is why I have never owned K-horns, every room has different dimensions. IF, your room has perfect dimensions, from your desired listening position then K-horns might be the ideal speaker (properly modified of course) or not, if the room dimension thing doesn't work out.

Plus, K-horns, like Tannoy Westminsters, need very large rooms to optimally perform.

As I have never owned AN speakers, I cannot comment on their placement. member's like @Warren Jarrett and @Richard Austen would be far better qualified on that subject.

I prefer to see speakers pulled out from the wall, but in some circumstances, it is not always practical to do so.

I go back to the days, where average American's had little or no knowledge of stereo's or bass. So I welcomed big but nice sounding bass, even in my younger days.

I'll agree with you about how you and perhaps myself view good strong bass, Which is why I run a commercial passive horn loaded bass cabinet.

The cabinet below is a Yorkville UCS-1, made in Canada. It can deliver 133dB, continuous program material. No flabby boomy bass here.

This American firmly believes that you can have volume and quality, but that's just me.



Myself, I have never been to a concert with excessive bass, but I don't really attend concerts that much anymore. Back in 2012, I went to see a performance of the Trans Siberian Orchestra in a hockey arena. The sound system was so loud, the narration hurt my ears. My eardrums were hurting after the show.

Most of the deep sub-bass is synth bass, which can be real nice if not used to excess. As I don't listen to the radio, I'm not aware of what music they play or what is on the pop charts.

 

There were plenty of 12" woofers in BBC monitors, going back to the origin of the species. Not many were offered to the public though.

Some BBC and BBC-pedigree speakers with 12" woofers that were commercially available include the Spendor BC3 and SA3, Rogers LS5/8, and Harbeth Monitor 40/40.1/40.2.

 

I agree that one can certainly have volume and quality, as long as the room is not overloaded. It just seems to me that the average American values quantity over quality where bass is concerned - maybe a consequence of a culture of excess.

Some of the BBC designs listed here used 12", 15" and even 18" woofers:
Mark's Pages › Loudspeakers - The BBC collection

This article explains why I believe they didn't exactly have small English homes in mind. However, I'd agree that some of the modern derivatives like the P3ESR S3/5, and M30.1 are definitely intended for small domestic applications. You could include the small floorstanders from Spendor and PMC in that category as well. Overall, I believe there's a wide variety of applications that these manufacturers address.

A speaker like the BC1 has more cabinet volume than many of today's small floorstanders and almost as much cone surface two 6" woofers.

 

The size of the speakers has very little to do to whether they designed to be close or far from the wall. Size is more related how much SPL you need or want given a certain distortion requirement. For example the Ino audio "monitors" below with 4x9 inch drivers per channel plays above 80 Hz and are close to the wall, while 4 subs take care of the register below 80 Hz.

 

That is very interesting, I have never seen the large commercial units before just the big shoe box size monitors.

 

I agree with that. But pulling speakers out form the wall can give you wonderful imaging that you will not get with most speakers that I am familiar with, if they are right up against a wall.

Herein noting that "imaging" is but one characteristic of a speaker.

My listening space does not lend itself to imaging per-say. So I don't really concern myself with it. I have four separate systems in the room that are all connected to the same source. Andy single system can be played, or they can all be playing together, at the same time.

Right now, I have three systems playing, for a more immersive audio experience, which is my listening preference.

 

If I would pull my speakers out to get "outside" the 15 ms window I would need at least 2,5 m/8,5 feet from the wall, preferably more, and this is not possible. Therefore I use damping behind the speaker/but hard center (TV screen) to take care of mid and high frequencies and use the wall for bass gain. Damping also on floor (thick carpet, table "filled with some damping") and work with diffusion in the rest of the room (walls, roof). I win 3 dB in the bass and at the same time make the wall "dissappear" almost completely. Imaging is terrific.

 

Very interesting topic. Thought I'd add my experience with a recent change in set up.

I recently changed the speaker placement in my room (images below - black squares are speakers, red thing is the listening chair). The original placement I was never really thrilled with. I didn't like having my audio rack between the speakers, didn't really like sitting with the wall behind me as close as it was, and just didn't like the lay out of things. But I couldn't really think of another way to have everything arranged.

Then it hit me to try a diagonal layout (see "After" pic). In between the speakers, along the right-hand side wall, there is actually a door that opens into a closet. So it's not really ideal having that there in between the speakers, but it's always closed and not really that big a deal.

In terms of sound, this is much improved over having the speakers in front of the long wall. The speakers before were about 18" from the wall (to the back of the speaker); now they are 7" away. So pretty close to the wall. AN speakers, so this should be expected to work well. And now there is nothing in between the speakers. There wall behind me is also a lot further back than before. I'm not sure what has the biggest impact but like I said, it's mission accomplished as far as sound or just general room layout goes! The soundstage is now more even and the level of detail that I perceive is much better.

Only downside - I have to pick up longer speaker cable!

 

May I suggest you consider the AN-D speaker cable? It is available either single bi-wired

 

I might suggest Home Depot 50 ft. 12/2 Black Stranded CU Low-Voltage Landscape Lighting Wire - at least then you know what gauge copper you are actually getting for your $17.

 

Best post ever SAND! I always do better with visuals! Love em

 

I like placing your speakers on the diagonal. It gives better imaging and helps eliminate standing waves.

My main system is on a diagonal.

 

Thanks! Never would have thought of AN. I'll definitely look into this cable. At the moment I'm leaning towards some Chord Odyssey cables. Would love to try Cardas Parsec but I'm not spending $1K on cables. Think I'm gonna say no to the Home Depot landscape cables, lol. Most cable companies publish a number for gauge.

Nice. Well, I am really enjoying it. Wish I'd have thought of this sooner.

Not sure if the pics I posted above make it very clear just how much room there was to the wall behind me before and after (I tried to make them to scale as best as I could but it's obviously not). Before I was 2' from the rear wall. Now, if I measure directly behind my head, it's almost 8'!! I imagine that has a lot to do with the change in sound. Room treatments are now something I'll want to explore.

 

Remember, low frequencies are omni directional. So backwalls can and do interfere with low frequencies

 

Well, in principle you're right, as I'm sure Barry Diament would agree: Setting up your monitoring environment . Indeed, I have seen measurements of a system of Genelec speakers that were wall-mounted, and they had a dip in frequency which was caused by cancellation by the reflected wave from the wall that the speaker was mounted on.

But in the real world, I think there are so many variables that speaker design and placement in the end becomes something of an art, and in the case of AN speakers, it seems to provide more benefits than disadvantages. But remember that AN speakers aren't known for being masters of imaging. Moreover, there are rooms where they simply don't work.

 

The concept of low frequencies being omnidirectional is of course mostly true, but there are qualifications. I had a budding career in science (but got out in time), and during that time I learned that the fields of fluid mechanics and acoustics lead rather separate lives and that even famous acousticians may be completely unaware of the transition phenomena between regions around a source where field may be viewed predominantly as a fluid dynamic field (close to the source) and a region where it is an acoustic field as we know it.

For at true monopole, i.e. a source like a pulsating sphere that changes volume and radiates equally in all directions (a pulsating fish swim bladder is a close approximation), the contribution from the two aspects of the field are equal at a distance of wavelength/2pi. With air as a medium, this means that at 20 Hz, there is a not insignificant contribution from the fluid-mechanic aspect of the field out to at least about 3 meters. This part of the field behaves like a fluid and doesn’t reflect of surfaces.

This isn’t widely known, and the reason I came across it was that I did research in the bioacoustics of underwater animals where it becomes a prerequisite for arriving at meaningful conclusion. If anybody is interested, PM me, and I can send the references to the original scientific literature.

A normal speaker isn’t a true monopole in the strict sense of physics—its surface doesn’t radiate in all directions. But below a certain frequency, the pressure generated in front of the driver will leak to the back side and become more and more omnidirectional with lower frequencies. However, a bigger and bigger part of the measured pressure will be associated with the fluid-mechanic aspect. I think this is the near field effect that John Atkinson measures in his speaker measurements. The interesting part is that this fluid-mechanic of the field isn’t reflective in nature.

Now, I’m a biologist, not an engineer or physicist, so I won’t venture into any prediction as how this may influence speaker design but I can’t help think that it may be part of why some speakers work even though they violate some of the best practices of speaker design. What I do know is that during my grad student days, I tried to follow a course in speaker design at an engineering school, and although I had to drop out because of too little basic engineering knowledge, what I did observe was that the modus operandi was to translate all mechanical phenomena into electric equivalence diagrams in order NOT to have to understand what actually was going on mechanically, something I have heard other engineer friends complain about.

 

One of our member's @The Pinhead had replied to a current thread about your dream castle system.

He had a pair of Klipsch KW-120-THX SUBWOOFER's as his "dream system" in the thread, Dream your mansion castle set up. shown here at the top of page two of the thread.

So, along the lines of this discussion...

Under the sub's specification's, I noticed;

Max Acoustic Output 130dB @ 30Hz, 122dB @ 20Hz, 112dB @ 15Hz 1/8 space

It is interesting for them to disclose the condition's that the actual speaker sensitivity measurements were taken.

Corner loading is the most important with lower frequencies and how the LF sound waves waves propagate, which is governed by the physical geometry of real space.

So, in the above example at 30 Hz., in the corner placement, they can put out 130 dB.

But... here is the rest of the measurement specification's; 1M (2 enclosures side-by-side per THX Ultra2).

It indicates that the measurements were taken at a distance of 1-Meter. But, it also indicates that it is with two enclosure's placed side by side. Which means, that they are both placed in the same corner (which makes little or no sense in the practical audio world).

So, if there is only a single sub, it would measure down -3 dB's from the 130 dB figure, or 127 dB's.

now take this same speaker out of the corner and place it along the back wall and we are now in 1/4 space and the maximum SPL is now reduced by another -3 dB to to 124 dB.

Pull the same sub out from the back wall and place it in 1/2 space and we loose another -3 dB to 121-dB.

So, even if it was possible, we are now at -9 dB's down from the original measurement specifications. So if we wanted to increase the SPL back up 10 dB's to 131 dB. It would require a ten times increase of amplification power.

These are apparently passive subs and are designed to be operated by an external amplifier.

It is interesting to note, that they do not specify how much power these speakers are rated for and what type of rating system is being used.

They only specify the use this specific model amplifier, "Use only with KA-1000-THX". In referencing this amplifier, we find out that it is a sub-woofer specific amplifier and it is rated at 1,000-Watts, into 4-Ohms.

The nominal impedance of the sub-woofer is is 8-Ohms and that this amplifier is capable of running two of these subs.

Which would mean that both subs are connected in parallel and each sub can be operated with a maximum input of 500-Watts.

(Even if you were only running a single 8-Ohm sub, you would only still get 500-Watts maximum out of this amp.)

So, in order to achieve their published levels of performance you would need to have two subs, next to each other in the same 1/8 space corner.

Anyone who has the most basic knowledge and/or experience will tell you, that the preferred method is not to place two subs right next to each other because of room node issues. The only time that this becomes practical is when they are placed close to each other against the center of the rear wall, which may or may not be workable, depending on the acoustical properties of the listening room.

Now 500-Watts is not an overly impressive amount of power for a sub. So, if you would even attempt to and IF you wanted to position this "single" sub pulled out from the center of the front (or any) wall, and you still wanted to get to the 131 dB SPL, you would need a power amplifier that was capable of delivering 500-Watts of program material.

But, at least they did provide us with their specific measurement techniques.

We do remain largely in the dark about what kinds of space, that most speakers are measured in, aren't we.

And, you can see that the differences can be significant.

S&G