Full-Range Speakers and Cabinet Design Discussion

from CommonSense Audio


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What Makes Audio Nirvana Full-range Speakers So Good?

1. An Audio Nirvana speaker is full-range. No separate woofer, midrange, tweeter, or crossover is necessary. Without trying to blend different sizes and types of speakers together, there is a purity of sound that just can't be achieved in multi-speaker systems. Also, all of the distortion and phase shifts produced in 'normal' speakers--when a crossover changes from one speaker to another--are eliminated. Best of all, the music doesn't pass through any inductors (coils), resistors, or capacitors. A crossover is a necessary evil in all other speaker systems. With Audio Nirvana full-range speakers, there is no crossover to deal with.

2. In most applications, only one Audio Nirvana speaker is used per cabinet. This gives perfect pointsource imaging. Common sense tells you that when someone sings, sound doesn't come from their mouth, their chest, and their knee (like it does in so-called 'normal' speakers). In addition, there are no time alignment problems (one speaker being farther from the listener than another), because the sound comes from a single speaker. You have never really experienced stereo imaging until you listen to a single, full-range speaker. Where the artist was previously 'in the middle', now that artist 'holographically' appears as a real human being. At night, with the lights dimmed, you will find it hard to believe that there isn't a real person in your room.

3. Audio Nirvana full-range speakers have incredibly strong magnets. This gives extremely precise control of the movement of the cone. The result is a very clear, crisp, clean, and accurate musical presentation.

4. Audio Nirvana full-range speakers use very stiff and light paper cones. This allows the cone to respond to changes in the music instantaneously and without distortion.

5. Audio Nirvana full-range speakers are highly efficient. They will produce high sound pressure levels and excellent dynamics with amplifiers that have as little as 1 watt. All Audio Nirvana speakers produce at least 95 db for 1 watt at 1 meter. In larger cabinets, it can be even higher.


Full-range Speakers--Some Myths

There are a lot of myths surrounding full-range speakers. Let's take a minute to address some of these:

1. Full-range speakers only work well with low powered tube amps.

Actually, it's the reverse that's true. Low powered tube amps only work well with full-range speakers......

This is because other types of speakers require more power than these amps are capable of producing. Also, full-range speakers use no crossover. Because of this, they present a very easy load for the amplifier to drive. Low powered amps will produce full, rich sound--at normal listening levels--ONLY with highly efficient full-range speakers like these.

But quality full-range speakers work equally well with tube or solid state, low power or high power. The power rating of an amplifier is irrelevant, as long as it doesn't run out of power and 'clip'.

In fact, highly efficient speakers like the Audio Nirvana actually make high powered solid state amps better. How? Most of these amps run pure Class A for the first two or three watts--normal listening levels for this type of speakers.

Another reason that full-range speakers have been linked to tube amps is that many tube amps (especially modern ones) are very soft and warm sounding. Most modern speakers are the same. The combination can put you to sleep. The incredible detail, clarity, and realism of full-range speakers will bring out the best in these amps.

2. Because of their design, full-range speakers only work well in 'bass horn' cabinets.

Audio Nirvana speakers have an excursion of plus or minus 1.0 mm. This excursion works well in either bass reflex or bass horn cabinets.

3. No full-range speaker can really go to 20,000 cycles--that's why they invented tweeters.

It's not true. Ten seconds of listening and you'll wonder why anyone builds tweeters.

4. Full-range speakers don't have great bass.

On the contrary, these speakers have strong, articulate, accurate, realistic, and tightly controlled bass. They also produce surprisingly high sound pressure levels. They test down only 3dB at 40 cycles in a good bass reflex cabinet. The bass they produce is balanced and totally satisfying with well recorded material.

Of course, this is only possible with an amplifier with flat response. The myth of poor bass probably comes from many owners using low powered, single ended triode amps with a rolled off bass response. However, many new single ended designs are capable of producing excellent bass. For those that don't, a quality subwoofer is the answer.

5. Full-range speakers can be overly bright.

Nonsense. Unfortunately, the vast majority of speakers available today are totally lacking in detail. They are 'dumbed down' to the lowest common denominator. That is, they are designed to soften even the worst sounding CD's. People used to these speakers initially mistake 'detail' for 'brightness'. But they quickly overcome this when they listen to a good quality recording played through these speakers. We refer to these modern speakers as 'dead, dull, dark, and distant sounding' (the four 'D's). Audio Nirvana full-range speakers are accurate and detailed, not 'bright.'

6. Full-range speakers are fragile.

Absolutely untrue. They are far more robust than systems with delicate tweeters.


Cabinets--An Introduction

The speakers are only half the story. The cabinets you use are almost as important.

Over the many years that full-range speakers have been available, scores of different cabinets have been designed for them. Some of these are bass REFLEX cabinets and some are bass HORN cabinets. In our experience, everyone that hears these designs, side by side, prefers the sound of bass reflex cabinets.

For those of you unfamiliar with the term 'bass horn', it is a cabinet design where a small space BEHIND the speaker starts very small but grows exponentially as it moves through a wooden 'horn' built into the cabinet. The sound from the BACK of the speaker follows this passageway as it winds back and forth and grows larger as it moves towards the exit. Eventually, it ends in a very large 'mouth'. This is actually called a 'folded' horn. If it were not folded, it would extend 6 feet or more into the room. . The theory behind them is similar to the way that a cheerleader uses a megaphone to lead cheers at a football game. The sound will be amplified when it finally exits the megaphone (or bass horn) at the 'mouth.' Historically, this design was created to get the most volume possible from low powered amplifiers. Unfortunately--just as the cheerleader's voice is distorted by the megaphone--so is the music.

Problems historically associated with bass horn speaker cabinets are as follows:

1. Distortion is created by reflections from the 'box' behind the speaker.

In a normal bass reflex design, there is acoustic damping material behind the speaker. This absorbs the sound coming from the back of the cone. But, because of the necessity of having the sound waves move freely through the 'horn', it is impossible to fit damping material here in a bass horn cabinet. Consequently, the sound from the back of the cone hits the back of the box and reflects back to the speaker. This causes reinforcement of some frequencies and cancellation of others. In other words, distortion.

2. Horn-loaded designs tend to 'fatten' or 'smear' the midrange and upper bass regions of the music.

This is because the sound emanating from the BACK of the cone goes through the bass horn and reaches the listener AFTER the music from the FRONT of the cone. This time delay is especially pronounced with bass horns that exit at the front of the cabinet. All bass horns give a 'tubby' sound, one with exaggerated reverb affects. The single best feature of a full-range speaker is the detail they are capable of reproducing. Much of this is either lost by cancellation or unnaturally enhanced by the sound coming from the bass horn.

3. Stereo imaging and soundstage are very poor with bass horn designs.

This is because there are three separate sound sources coming from both the left and right speakers (sound directly from the speaker, from the bass horn, and from cabinet resonances caused by vibration). None of this information is time coherent. Each note on the recording arrives at three different times at the listener's ears (six, if you count both left and right speakers). This makes it very difficult to produce a precise stereo image. Historically, this was not important, because most of these designs date from the mono era. Before stereo, the concept of imaging didn't even exist.

4. Horn-loaded cabinets exhibit a ragged bass response.

Not the smooth response most people are used to--and prefer--from bass reflex cabinets. With each change in a third of an octave, bass horn cabinets may be up 8dB here, then down 6dB, then up another 7dB. They can end up making bass tones rather than clearly articulated bass notes.

5. Horn-loaded cabinets do not play very low bass.

Our testing indicated that a bass reflex design will actually go significantly 'lower' in the bass region than almost all of the horn designs. All of our bass reflex cabinets are capable of flat response to 40 Hz (-3 dB) using boundary reinforcement, while almost all of the bass horn designs roll-off below 63 Hz.

6. Horn-loaded cabinets are very difficult and expensive to build, and hard to place in most rooms.

Most of them are also very large and unusual looking and have a very low WAF (wife acceptance factor)! Of course, this unusual appearance can be appealing for some people. And, of course, they can make an interesting and challenging woodworking project.

7. There is no significant efficiency advantage with the bass horn designs.

The best are only around 1 or 2dB more efficient than a properly designed bass reflex cabinet.

8. It is possible to overdrive bass horns.

Speakers used in this type of cabinet can't have a lot of excursion and can't be driven too hard. If they are, the pressure builds up in the chamber behind the speaker and produces distortion. If you really want thunderous bass and dynamics and bass response to 20 cycles or lower, it will be necessary to purchase a quality subwoofer.

We'll also discuss another type of speaker cabinet--open baffles--below.

9. Horn Loaded cabinets were never designed to accomodate full-range speakers.

When Paul Klipsch originally invented bass horn cabinets, they were designed only for woofers, and only for frequencies from 200 hz to 20 hz. Used this way, the problems mentioned above in 1, 2, and 3 are not important.


Bass HORN Cabinets

Is there any situation where we could recommend a bass horn cabinet? Well, actually, there is one....

Classical music is unique in that the concert hall is an integral part of the enjoyment of the sound. It is virtually impossible to make a recording which can accurately capture a classical music performance. This is because when you sit in a concert hall, you hear many different sources of sound--the music coming directly from the orchestra--the reflections off side walls, the ceiling, the back of the hall--resonances coming from the floor under the orchestra and the hall itself. And stereo imaging is not an important element in orchestral works.

In this case, the colorations of a bass horn can mimic what goes on at a classical concert. It's not accurate, of course, but if it can simulate the actual event, then isn't that what's important? So, some of the liabilities of the bass horn design CAN become assets if many factors are carefully considered (like room placement, etc.)

But there is a way to produce the same results with bass reflex cabinets and we have done so. By mounting a second speaker on the top of the speaker--pointing up--it is possible to produce the same wide, spacious, ambient sound. Coincidentally, we call it the 2.8 'Ambience'. It produces a wonderful ambient presentation--much as the bass horns do--but without many of the problems mentioned previously. Most people prefer it to bass horn designs for classical music.

The 2.8 'Ambience' has better imaging, lower distortion, and all the accurate, realistic bass that can only be achieved with a bass reflex design. We believe that it is the best answer for classical music.

In addition, this speaker can be built with a switch for the top speaker (so it can be turned off). With this switch, it is possible to have it both ways. You can operate the front speaker for most 'normal' types of music. You can turn on the top speaker when you want a more ambient or powerful sound. Two speakers working together doubles the bass and dynamics of the system. This is better for all types of music.


Bass REFLEX Cabinets

Probably 99.9% of all speakers ever made are Bass REFLEX. Why? In our humble opinion, because they give the best sound! This design produces the most realistic bass and most accurate midrange and treble. So, we strongly recommend the bass reflex cabinet.

A speaker cabinet only exists to do one thing: make bass. Generally speaking, a well designed larger cabinet will always sound better than a well designed smaller one. That's because it's hard to make enough bass to balance with the mids and treble, especially with very detailed speakers like Audio Nirvana. So, over the years, we have developed larger and larger cabinets (as well as larger and larger full-range speakers). However, we haven't forgotten that many customers have space limitations. For them, we have tried to design smaller cabinets that maximize bass output while maintaining the clarity and tightness often missing in small cabinets.

Our first bass reflex design, for the 6.5 and 8 inch full-range speakers, was called the '1.3'. The external dimensions are 32T x 10W x 11D (with the grill mounted). It's an excellent small floorstanding speaker system. By the way, the name of all of our floorstanding speakers is the volume in cubic feet.

Further development resulted in a larger cabinet we call the '2.8.' There are two main variations. The original 'Series I' has a wide front baffle. The 'MkII' has a thin front baffle. Overall dimensions are approximately 38.5T x 14.5W x 11.25D (Series I) or 38.5T x 12W x 13.75D (MkII). They are close enough in sound quality, that you can pick the one that looks best to you. But the 'Series I' does give a bit softer, smoother, and warmer presentation and might be preferable in 'live' rooms. The 'Mk II' is slightly more detailed and efficient and might be preferable in 'soft' rooms. The greater internal volume (twice as many cubic feet when compared with the '1.3') has resulted in stronger bass response and dynamics (maybe 15%).

And we offer two tuning choices for both the 'Series I' and 'MkII'. One is called the 'Twin Port', which uses--obviously--two small round ports. The other is a 'Big Port' variation which uses a single, very large port. The 'Big Port' offers more mid bass at the expense of some lower bass output. You can use Audio Nirvana 6.5, 8, 10, and 12 inch models with either type of tuning.

Both the '1.3' and the '2.8' can test relatively flat (minus 3 or 4 dB) to 40 cycles and give at least 98 dB from one watt (at one meter). We say 'can' because changing the porting will shift the bass emphasis. We find that some people prefer more output in the 50 to 100 hz range and we developed the 'Big Port' tuning to emphasize this range.

In response to demand for a smaller monitor type speaker, we completed a design of only 19T x 10.5W x 11.25D, or .87 cubic feet. We call it the 'Minimonitor'. We had our reservations about putting an 8 inch full-range speaker in such a small cabinet, but we were very pleased by the results. The bass rivals any other minimonitor in output and far surpasses them in clarity, detail, accuracy, and realism. All of the astonishing midrange and treble is unchanged by using the smaller cabinet. This speaker could become a reference for all recording studios serious about making great recordings. And it could also become a standard for small speakers in the home environment. It can also be used successfully as a surround speaker or center channel.

Some customers wanted more bass from a 'bookshelf' style speaker than our 'Minimonitor' could provide. For them, we developed the 'Monitor'. Dimensions are 24T x 13.5W x 11.25D. It is 1.5 cubic feet in volume, almost twice the 'Minimonitor's' volume. As such, it produces a lot more bass. The inspiration for this speaker was quality bookshelf speakers from the 1960's and 1970's.  This was a golden age for audio. We still don't think mainstream speakers today are as good as they were back then. The 'Monitor' will accept Audio Nirvna 6.5, 8, 10, and even 12 inch models.

Other customers asked for a speaker even smaller than the 'Minimonitor', one that they could use for surrounds, for a center channel, for computer speakers, and as an extension speaker in smaller rooms. For them, we designed the 'Micromonitor'. It's only 16T x 10W x 7.25D, or .41 cubic feet. The 'footprint' is only 10 by 8 inches. The 'Micromonitor' can also be used with a quality subwoofer. With careful matching, we were able to achieve excellent sound. It will accept 6.5 or 8 inch speakers.

Development of our Audio Nirvana 'Super 15 Cast Frame' meant that we needed a new cabinet designed specifically for this speaker. We came up with a beautiful tower speaker of 44T x 18.75W x 14.75D which we call the '5.6'. Such a cabinet produces effortless performance. Big, expansive, powerful. If you have the space, it's an excellent choice. And many customers have also used it for our 10 and 12 inch models, also with excellent results.

For the 'ultimate', we developed our huge '13.6' cabinet. Dimensions are 48T x 24W x 24D. The 13.6 is capable of producing all the dynamics that anyone could reasonably want in the home environment. It will accept the 'Super 15 Cast Frame' or 'Super 12 Cast Frame.' In addition, it was specially designed to accept two 12 or 15 inch speakers, if the customer chooses.

While all of our cabinets are satisfying full-range systems in their own right, for those who value extreme dynamics in their listening, or are seeking the lowest possible bass extension (for music or home theater), any of these systems can easily be supplemented with a quality subwoofer. We have done extensive testing of this combination and can tell you, quite honestly, that this will provide all the bass and dynamics you could ever possibly want.

Once you've decided on the bass reflex cabinet that best meets your needs, it is important to note that the material used to make the cabinet is an important factor. Plywoods will generally give a softer sound, particle board--intermediate, MDF will give the most detail. For a soft listening room, you may prefer MDF. Medium rooms--particle board. And for live rooms, we recommend high quality Baltic Birch or marine plywood. As the quality of your source material goes up, so too can the density of the material you use to make your cabinets.

You can also experiment with different damping materials and how much of it you use inside the cabinet. The main role of the material is to absorb the sound coming from the back of the speaker cone (any speaker cone sends sound to the rear as well as to the front). If this back wave is allowed to reflect off the back of the cabinet and then go forward and strike the cone, it will introduce distortion. Standard procedure is to apply damping material to all sides inside the cabinet except the front baffle. But you can get different--and sometimes better--results by varying how much you use.


Dual Speaker Bass Reflex Cabinets

Some people have some special requirements that their speakers need to address. For them, we have developed two different dual speaker bass reflex cabinets. Why use two speakers when we've been praising the virtue of using only one? There are some situations where the compromise of using more than one speaker in each cabinet is worthwhile. These two situations are as follows:

One. You have an extremely large room or like to play music at extreme volumes, but don't have enough floor space for the '5.6' or '13.6'. Or, perhaps, you just think these cabinets look too big. For you, we developed the '2.8 Dynamic.'

Two. You like the idea of using 8 inch speakers but think they won't make enough bass or dynamics in your room. For you, we have developed the '2.8 Ambience.'

Of course, there are some tradeoffs. A dual speaker system will not image quite as well as a system using only single speakers. However, the reduction in imaging is less than you might imagine. And because these are Audio Nirvana full-range speakers, even the dual speaker systems image better than any other speaker. For some people, it may be a worthwhile tradeoff in exchange for what these dual speaker systems can do.

Audio Nirvana 2.8 'Dynamic'

We took a standard '2.8' cabinet and added a second speaker below the first one on the front baffle. Both speakers are wired in parallel for an effective impedance of 4 ohms. This combination gives more bass and effortless dynamics. It is a good choice for very large rooms or for people who prefer their music loud.

Audio Nirvana 2.8 'Ambience'

For this design, we again took a standard '2.8' cabinet and mounted a second speaker on the top, pointing up at the ceiling. Both speakers are wired in parallel for an effective impedance of 4 ohms. This design doubles the bass and dynamics of the speaker without giving up much in the way of imaging or soundstage. Two 8 inch speakers have the equivalent cone area of a 12 inch speaker. So, you get the precision of an 8 with the power and dynamics of a 12. There's also a touch of 'ambience' from the top speaker. How much will depend on the height and reflectivity of your ceiling.

While it probably doesn't produce any more bass than the 'Dynamic', the 'Ambience' gives the impression of making more bass. That's because a lot of midrange and treble output, from the top speaker, is 'lost' in the room before it reaches the listener, but the increased bass is not. So, the overall tonal balance is different, with more bass.

One interesting advantage of the 'Ambience' is that you can put a switch on the top speaker. For the best imaging and soundstage, you can turn the top speaker off and enjoy all the advantages of the original '2.8.' For more ambience, more power, or more dynamic you can turn the top speaker on.


Open Baffle Cabinets

Open Baffle cabinets are basically just flat pieces of wood supported by two 'wings' to hold them upright. Since cabinets exist mainly to generate bass, one has to ask 'why' these are used. They don't generate much bass and what they do produce rolls off below 63 cycles, even with the largest full-range speakers. With 6.5 or 8 inch speakers, this rolloff can occur below 100 hz. The situation can be helped somewhat by placing them close to rear walls or corners.

The answer lies because they have a 'different' sound to box type speakers. Because there is no damping material behind the speaker cone, the sound from the back of the speaker is free to reflect off rear walls and join the sound from the front of the speaker. This time delay gives a 'fat' sound that some people like for classical music. And some people just like this type of sound. Supplemented with a quality subwoofer, the missing bass can be replaced, but not as seamlessly as with bass reflex systems.

Open Baffles give an unusual presentation. Initally, they can be quite interesting, but for many listeners they soon grow tiresome when you realize both what's missing and what's being (inaccurately) added. But they're extremely easy to build and we would encourage everyone to give them a try to see what all the fuss is about. They work best with the largest full-range speakers, which can generate more bass without an enclosed cabinet.


Conclusions

The advantages of using full-range speakers are easy to describe, but hearing is believing. Once you've heard a quality full-range speaker, you will never be able to go back to so-called 'normal' speakers. But it's important to put these speakers in a properly designed bass reflex cabinet. You can't expect great performance if you put a Ferrari engine in a pickup truck.....