Product News Pure Reference Extreme Loudspeakers Available Options on Coincident Speakers Technical Notes Passive vs Active Preamps The Coincident Sound Why Biwire? Cables: What is Important? Mirror Imaged Woofers Amplifier Power: How Much? Loudspeaker Impedance and Amplifier Matching

Pure Reference Extreme Loudspeakers

Coincident Speaker Technology is thrilled to introduce the Pure Reference Extreme Loudspeakers. The Extremes use the identical drivers, crossovers, internal wiring, and binding posts as the Pure Reference. The difference between them is that the Extreme physically separates the enclosures for the mids/highs and the woofers. The benefits of the Extremes are as follows:
	Pure Reference Extreme	Pure Reference Extreme (T)

1. Separation of the enclosures reduces vibrations and enhances cabinet rigidity. The interaction of the woofers with the mids/highs is more effectively isolated. Sonically, this translates to greater purity and transient precision;

2. Monitor- The connection from the midrange to the binding post eschews any wire at all. The crossover inductor is a direct, hardwire connection to the driver and the binding posts.

• The Pure Reference, due to its size, requires a 5 ft cable to connect the crossover to the binding posts.
• The wire connecting the tweeter to the binding post has been reduced from 5 ft in the PR to 4" in the Extreme. The aural affect is enhanced transparency and immediacy.
• The small Monitor enclosure( just large enough to house the 2 drivers) reduces diffraction affects dramatically which results in a more open soundstage with greater focus.

Additionally, the front baffle is sloped which results in perfect time alignment between the drivers.The sonic consequence is disarming realism in reproduction.

3. Woofer- The wider stance (13" vs 9" for the PR) and shorter height ( 33" vs 55" for the PR) results in greater physical stability which reduces micro movement of the enclosure.
Furthermore, the extra width moves the back of the side firing woofers 4" further away from the enclosure wall. This minimizes reflections back to the woofer which slightly reduces non linear cone motion at very high SPLs. The bass of the Extreme has a tad more weight and impact than the Pure Reference.

The Pure Reference Extreme takes the already state of the art performance of the Pure Reference and elevates it to a slightly higher degree. The differences are subtle and requires the highest resolution ancilliary components and musical sources to discern. For the audio perfectionist who values sonics above all else and is not bothered by the requirement of an extra pair of speaker cables, the wider footprint and the less than sleek appearance of the Pure Reference, the Extreme will more than justify its slightly higher price. The Pure Reference will remain available since it still offers practical advantages and a different aesthetic appeal.

Specifications:

Frequency Response: 20hz- 27khz
Impedance: 8 ohms ( never dipping below 6 or going above 10 ohms).
Sensitivity: 94 db @ 1M - 1 watt
Power Requirements: 3 watts- 500 watts
Dimensions: Monitor - 12" H x 9" W x 6"D - Sub Woofer- 33"H x 13"W x 24" D
Weight: Monitor- 28 lbs Sub Woofer- 175 lbs

Driver Compliment - Monitor- 1- 1.2 " Accuton Ceramic Tweeter
1- 6.5 " Accuton Ceramic Midrange

Sub Woofer - 2- 12 " Nomex Fiber Cone Heavy Duty woofers.
Price : $26,000 US /pr.

 

COINCIDENT PURE REFERENCE "EXTREME"

The "Extreme" is simply the "Original" Pure Reference, with the exact same drivers and crossovers, but in two separate cabinets (a mini-monitor and a subwoofer), instead of one large floorstander. With the monitor sitting directly on top of the subwoofer (at the front), the Extreme is around 12" shorter, though its subwoofer takes up around 50% more floor space, because it is 4" wider. The price for the Extreme is $ 26,000, compared to $ 22,000 for the Original.

I have around 100 playing hours on the Extreme, and all of it with the Coincident Frankenstein M300B II amplifier. Based on the experiences of others, it will further improve with more hours, but not dramatically. The big questions are how the Extreme compares to the Original, and whether the $ 4,000 price differential is worth it (since the Original will still be available). First though, I would advise those seriously interested to read, or at least skim over, myReview of the Original Pure Reference. This should help the reader to fully appreciate the sonic differences between these two (otherwise) similar sounding speakers.
Now, as to its performance...

The Original Versus the Extreme

The Extreme is superior to the Original in a number of areas, equal in others and inferior in none. A typical "neighbor", or "brother-in-law", would not be able to distinguish one speaker from the other, but any experienced audiophile should easily hear the differences. In every instance, but one, the sonic differences between them are minor, meaning they are "noticeable", but not "obvious", unless you are an exceptionally discerning listener, or are intimately familiar with their sonics (as a normal long-time owner should be). I will deal with these minor improvements first.

The Extreme is a little cleaner and faster than the Original. The purity is more easily noticeable at higher volumes, but is still slightly audible at lower volumes. The Extreme sounds even more like a top electrostatic, such as the Martin-Logan CLS (in its greatest strengths), than before. While its overall tonal balance, perspective and neutrality are the same as the Original, the Extreme does have a small reduction of those tiny frequency aberrations which are unavoidable in every speaker. These deviations are too subtle to even describe, but they still inform you that a mechanical device is reproducing the instrument, rather than it being the real thing.

As for the frequency extremes, the highs are the same, though the bass appears to be just a touch more extended, and with a little more weight and body to it. The quality of the bass is also slightly improved, being, once again, a little more articulate, controlled and defined. The quality of the highs is also better, but it's even more subtle. This time, a very tiny resonance, only barely audible with very specific frequencies (flutes, violins and sopranos), has now been effectively eliminated. (Since this resonance was slightly more noticeable with the Ars Acoustica System Max, I wasn't able to isolate the cause of the residual problem when I heard it being reduced.)

I saved the best for last, because there is one area that the Extreme is significantly superior to the Original: Image Focus. In my lengthy review of the Original Pure Reference (PR), I mentioned that my ultimate reference for image focus was the Morrison, which is an omni-directional speaker. Just behind the Morrison was the Ars Acoustica, which is the speaker that the PR replaced. The PR, as good as it was, still noticeably lagged behind both of them. This is no longer the case. Now the Extreme equals the Ars Acoustica. In fact, it's so similar to the Ars in focusing, it's almost spooky (I lived with the Ars for 10+ years, and just heard it again in June 2009).

There is one small difference between them though, and it's actually in the Extreme's favor. The Extreme is slightly better focused at the lateral extremes (to the left of the left speaker and to the right of the right speaker) than the Ars. In fact, the Extreme is as good as I've ever heard, even including the Morrison, at the outer edges of the overall soundstage. (The Morrison is still the "champ" in the large middle.) I don't believe the soundstage itself is any larger, but it is better "organized", so it may appear larger because it is more easily "seen" and "understood". This brings us to the second "big question":

Is the Extreme worth the extra $ 4,000?

This question can only be answered by how much you value the various improvements. In my case, the improved image focus alone makes it worth the extra money, with the rest being "icing on the cake". The bottom line for me is simple: I can't go back to the PR.

Other audiophiles, who don't value "imaging", may have a very different perspective. In fact, unless you truly value imaging, then I would most likely pass on the Extreme, unless either:
1. You just must have that last degree of purity, speed and detail etc., discussed above, or
2. The added flexibility of having two separate cabinets is important to you, especially if you want to "double up" the speakers one day, and/or place the subwoofers elsewhere in your room, while optimizing the position of the monitors on their own.

Then there is one last question: What if you already own the Original PR? Should you spend something like $ 10,000 to trade up? Frankly, I don't feel it's worth it, unless you are an imaging "enthusiast", meaning someone who is actually bothered by the PR's imaging performance, but otherwise satisfied. Other than that, the differences I've described are just too minor to justify that kind of money.

Conclusion
The Extreme is a welcome improvement over the Original Pure Reference. If I was to asked to make an analogy, I would say that most of their differences are the equivalent of "turning a page or two", while the Image Focus improvement is the equivalent of an entire "new chapter". In the final analysis, the Pure Reference, in its Extreme form, is another step closer to the music, and a step further away from the "mechanics".

 

 

This past year has been a banner year for Coincident both commercially and in terms of product recognition. The following awards were bestowed upon Coincident components:

Statement Line Stage- Stereomojo Component of the Year.

Frankenstein M300B Mono Amplifiers- Stereomojo Highly Recommended Component

Super Victory -	The Absolute Sound Editor's Choice
	Stereomojo Speaker of the Year.
Total Victory IV -	Enjoy The Music - Blue Note Award of the Year.
	Stereomojo - Highly Recommended Component

Passive vs Active Preamps

Passive Preamp- In essence is merely a volume control designed to attenuate the signal going from the source (usually a CD player) to the amplifier. Since it is passive, it has no inherent gain because it has no active components (tubes or transistors) in the signal path.

The quality (sonic purity) will be largely dependant on the volume potentiometer used. The finest discrete resistor pots will sound more accurate than a variable one, for example, since the signal travels through only one resistor at any given setting and is therefore not dependant on volume position as is the case with a variable pot. Many believe that transformer volume controls can be superior to even the best discrete resistor pots, since the TVC is inherently passive while the latter still requires the audio signal to traverse a resistor. The TVC is more costly to properly implement since the best transformers are very expensive.

Type, length and quality of the internal wire will also affect the sound as will the connectors being used. The inclusion of a selector switch will compromise the ultimate transparency of the sound to a greater or lesser degree compared to a passive eschewing this switch.

Active Preamp- Not only controls the volume of the source component but since it uses active devices (tubes or transistors) in the signal path it has gain. The active preamp inherently has many components in the signal path compared to a passive. It uses all the components of the passive with the addition of a power supply, capacitors, resistors, gain devices, and means by which all these parts are connected.

Logic would seem to dictate that the active preamp must adulterate the signal to a far greater degree than the passive by virtue of all those additional components.Further, since the active has the additional disadvantage of requiring a power source, tubes or transistors it must not only impose far greater noise, it is also more costly and inconvenient to use. Why would anyone want to use the active in a system? Theoretically, it would seem nonsensical to use anything but a passive preamp.

The Imposition of the Real World –

Passive Preamp - While it is inherently simpler in design with no active components in the signal path, it is highly susceptible to component interaction. The affects of the IC cable (impedance, capacitance and resistance), the source resistance which is the combination of the potentiometer and the actual source and the input impedance of the amplifier are all critically important in potentially altering the audio signal from source to the ultimate sound being heard.

The length of the cables between the source and passive and then to the amplifier must be strictly attended to. Too long a cable and roll offs at both frequency extremes will occur. Impedances between the volume control and the imput impedance of the amplifier must be compatible in order to avoid sonic degradation. Furthermore, since a passive has no gain, the output voltage of the source component must be sufficient and the amplifier and the speakers need to be of high sensitivity or not enough ultimate volume can be achieved.

The purest, simplest but admittedly most inconvenient method of passive attenuation is to have discrete resistor pots installed at the amplifier input. This method avoids the extra cable interaction and achieves the desired amplifier input impedance.

To summarize, in order for a passive preamp to work properly the following conditions must be met:

1. Source component must have sufficient ouput voltages;
2. Short, low capacitance cables must be used between the source to the passive and from passive to the amplifier;
3. Output impedance of the passive's volume pot should be low (less than 25k) while the input impedance of the amplifier should be sigificantly higher (100k);
4. Amplifier's input sensitivity should be high (minimum of .75v for full output).
5. Speakers should be high sensitivity (minimum of 90db).

If even one of the above conditions is not adhered to, passives will offer highly compromised sonics. However, when all of the above conditions are met, there are very few active preamps on the market that will yield better sound overall. For an active to provide superior sound, will require an amazing unit designed and executed to the highest level. (translation- it will not be cheap- but do not confuse excessive price with high performance- however high performance will be expensive).

Active Preamps - Due to the use of a myriad of components in the signal path, most active preamps severely color the sound. The signal entering them rarely resembles the sound exiting them. Theoretically, an active preamp should emulate a straight wire with gain. It should be as pure and transparent as the finest passives in an optimized system yet offer the benefits of gain and nonsusceptibility to component or cable interaction. This task would seem impossible to fully achieve and arguably no active preamp currently available has been completely successful in its accomplishment. The realistic goal of an active preamp is to provide sound with all the advantages inherent in the design with drawbacks that are so minor as to wither into insignificance when viewed in its totality. Achieving this objective requires the following:

1. The finest passive and active components available connected with the shortest signal paths possible;
2. A power supply that is impervious to voltage fluctuation or current demands;
3. The finest form of signal attenuation;
4. The purest gain devices;
5. Low output impedance;
6. A highly rigid chassis that is not prone to resonances.

The inherent practical advantages of an active over a passive is that due to output buffering, interaction between the source, connecting cables and amplifier input impedance ceases to be an issue. Further, due to added gain, much greater flexibility in system assembly is possible.

Coincident has up to the advent of our Statement Line Stage recommended the use of the best passives when all the system conditions were optimized. The sonic compromise inherent with all previously auditioned active units in terms of imposed colorations were too obtrusive to ignore, despite their other advantages.

Coincident Statement Line Stage -

All the requirements mentioned above to create the superior active preamp have been met. The end result is an active line stage that is virtually as pure and transparent as not only the best passives but as accurate as going directly from the source component to the amplifier using the finest 1m interconnect. The sonic leap in dynamics, weight, impact and punch as well as full extension at both frequency extremes is dramatic.
The enhancement of musical enjoyment wrought by the insertion of the Coincident Statement Line Stage into an audio system is of enormous proportion. As reviewers and owners of the unit have confirmed, the superiority of the Coincident over passives and existing active preamps is not subtle. A short audition is all that is required to hear this level of advancement.

_______________________

 

VIDEOHIFI interviews Coincident Speaker's Israel Blume

Coincident Speaker Technology is proud to still state that unlike the majority of current speaker companies (i.e. Revel, Aerial, Von Schweikert, Red Rose etc.) all its speaker models are designed and completely manufactured in Canada.

All the crossovers are meticulously hand soldered in Canada, matched to within 1% tolerances using the finest Canadian and American components. Coincident does not use poor quality Asian sourced crossovers that are pre built and cost a couple of dollars. The price of one capacitor used in a Coincident speaker crossover exceeds the cost of these entire crossovers that are finding there way into very expensive competing speakers.

All internal wiring is manufactured in Canada using American 6N copper. Only the finest Canadian dielectrics like polypropylene and air Teflon are used. Our wire sounds the best and is very expensive to manufacture and labor intensive to terminate. Other high end speaker companies use off shore cable that is sonically inferior and costs pennies.

All Coincident speaker enclosures are meticulously CNC and hand crafted at our facilities in Canada. Only the highest quality Canadian made hardwood MDF using furniture grade cherry wood veneer which is pressure applied on both sides of the board is utilized. Having our enclosures made in China, as most other speaker manufacturers, would save 80%-90% of the cost. However, we would not even think of doing this since the quality of workmanship simply does not compare. Inspect a Coincident enclosure with those made in China and the difference is painfully obvious. Coincident will never sacrifice quality for profits.

All the drivers of Coincident speakers are sourced from only state of the art manufacturers such as Scanspeak, Vifa and SEAS. Coincident does not use any Chinese manufactured drive units that are knock offs of the above noted brands. Many high end speaker companies no longer use the expensive, best sounding drive units made by these European companies, instead opting to use inferior sounding and incredibly cheap (costing as little as a couple of dollars) Chinese units that are almost visually identical. The consumer is fooled into believing he is buying an expensive speaker using Scanspeak drivers when in reality the drivers are very cheap poor quality units that only physically resemble those drivers.

Coincident Speaker Technology is committed to providing the high end audiophile the finest value loudspeakers in the world. Coincident, therefore, will NEVER sacrifice quality. No detail is considered too trivial if it enhances the sonics or build quality of our speakers. Coincident will never offer an inferior product in pursuit of greater profits. Therefore, none of our speakers will be made in China nor will any of our models use inferior components because they are inexpensive to purchase and will increase our profit margins at the expense of quality. Coincident speakers exist for only one purpose: to provide the discerning music lover with the finest sounding, best built loudspeakers available anywhere near their selling price.

 

Why Biwire?

Biwiring is when a loudspeaker has separate connections to the bass and the treble/midrange. The idea is to use individual speaker cables to each section. Besides being profitable to cable manufacturers, since the user is required to purchase double the amount of speaker wire, are there any sonic benefits to this arrangement?

The answer is yes and no. Yes it is a benefit for loudspeakers that are not properly designed. In speakers where the crossover sections are interdependant and not adequately isolated from one another, biwiring will likely offer a sonic benefit. However, in speakers, (like all Coincident models), that have all the crossover sections, (high pass, low pass etc), completely separated and isolated from one another and are run to the binding posts, (as opposed to being interconnected between sections and wiring all the hots and grounds to the speaker's binding posts), biwiring affords NO sonic advantage and may actually involve a sonic degradation depending upon the speaker cable used.

Coincident recommends biwiring only in those cases where a consumer has the intention of biamping his speakers. A biwiring option will be necessary if one is biamping a system, meaning separate amplifiers will be powering different drivers. Otherwise, biwiring is not only totally unnecessary and a waste of money, but a pain in the derriere.

Mirror Imaged Side Firing Woofers - Advantages

Unlike the majority of other speaker companies that place their woofers on the front of their speakers, Coincident mounts their woofers on the side of the enclosures in a mirror imaged configuration.This is done because there are 3 distinct advantages with NO downside.
TOP

1. Elimination of Diffraction Effects -

Since the largest drivers,(the woofers), are mounted on the side of the enclosure, the front baffle can be made as narrow as the smaller midrange drivers, thereby eliminating diffraction effects, (which are responsible for impairing image width and creating high frequency smearing).

2. Flexibility of Speaker Placement -

Because the side firing woofers are mirror imaged, there are two positions to avoid room standing waves - woofers aiming to the inside or to the outside. In a room devoid of standing waves, (a very rare phenomenon), there would be absolutely no sonic difference whether the woofers were firing inside or outside, (so long as there is sufficient distance to the side wall in the case of outside firing). This is so because the crossover frequency to the woofers is so low, (typically 125 hz), where the wavelengths are very long, (in the range of 9 ft). This means that the woofers can be placed a distance as much as 9 ft away from the midrange units and still achieve seamless driver integration.

The Stereophile Show 2001 provides a dramatic real world illustration of the benefits of mirror imaged side firing woofers. The demonstration rooms were plagued with a standing wave centered at 100 hz ( elevated in amplitude by 12db!). This was the case when the Total Eclipse woofers were firing to the outside and as other exhibitors experienced, when the woofers were front facing . However, when the woofers aimed to fire to the inside, the room standing wave was avoided and flat frequency response to below 30 hz was achieved.

3. Simulation of Steep Crossover Slope-

Since high frequencies are directional, (low frequencies are not), aiming the woofers to the side of the listening position causes out of band high frequency information to be attenuated, thereby simulating an acoustical high pass filter. Therefore, the electrical first order crossover (chosen for reasons of purity and phase coherency- attenuates out of band frequencies at a rate of 6db per octave), of Coincident speakers act more like an acoustical third order slope (with its advantages of steeper attenuation- 18db per octave- of unwanted out of band high frequencies), but with no sonic penalty since no additional electrical components are added to the signal path.

Amplifier Power - How Much Is Enough?

This is a question that is asked almost more frequently than any other.As with most issues in audio,the answer is complex and depends upon the following:

1. Speakers being used- Sensitivity and the impedance curve being critical.

2. Personal preferences of the listener- Type of music listened to and at what output levels.

3. Size of room - To fill a larger room will take proportionally greater amplifier power.

Speakers-
Acoustical output is dependant upon the power of the amplifier used and the efficiency with which the speaker being driven can transform the electrical signal into sound.The term "sensitivity" is a speaker measurement that reveals how much sound (in decibels) is produced at a specified distance, (usually 1 meter), from the speaker when it is fed a specified input signal, (usually 2.83 volts which is equivalent to 1 watt into 8 ohms). Therefore, a more sensitive speaker that has a flat, benign impedance curve (of 8 ohms or more), will produce greater acoustical output with the same specified amplifier power than a less sensitive speaker or an equally sensitive speaker that has a reactive, low impedance modulus. For example, a speaker that is 3 db more sensitive than another will require only half the amplifier power to generate the same sound output.

If a speaker has a sensitivity rating of 85 db @1 watt - 1 meter, to achieve an output of 88 db would require double the amplifier power or 2 watts.91 db output would take 4 watts. For 100 db output of sound, would require 32 watts of power. And if this speaker was rated at 4 ohms, a 64 watt amplifier would be needed to produce 100 db.

By contrast, a 94 db sensitive speaker would require only 4 watts to achieve a 100 db output level. Since most listening in the home environment is undertaken at 85 db or less, it can be clearly seen that only a fraction of a single watt of amplifier power is all that is required for the vast majority of listening. A 100 db output, which is loud, still needs only 4 watts of power to attain. However, it must be emphasized that while listening at an average level of 100 db, during musical passages that are very dynamic with lots of low bass content, many hundreds of watts may be necessary, (albeit for only the duration of a millesecond), to avoid amplifier clipping.

The above example clearly demonstrates how significant the sensitivity and impedance curve of the loudspeaker is upon determining how much amplifier power is necessary.

Personal Preferences of the Listener-

As the above example illustrated, higher listening levels requires greater amplifier power. Therefore, the output levels the listener chooses to listen at, will be critical in determining the amount of power that will be satisfying. The listener who is content at levels of 80 db will need a fraction of a watt while someone who likes to listen at 105 db will be using almost 260 times more power!

Of equal importance is the type of music enjoyed. Full orchestral music, for example, is very demanding on amplifier power in order to reproduce the exceptionally high levels of dynamics coupled with very low bass content (which uses enormous amounts of power). Conversely, chamber music, light folk etc. is usually listened to at lower SPLs and its musical content requires far less amplifier power to accurately reproduce.

Furthermore, some listeners prefer a punchier, gutsier sound presentation than others whose priorities lie more in the area of detail retrieval, imaging etc. For some, visceral impact is mandatory or at least may represent much more of a priority than it is to others. These personal predilections must be factored into the equation of how much power is sufficient.

Room Size -

All things being equal, the larger the room, the more amplifier power required to fill it. The sensitivity rating of a speaker is the measurement of acoustical output at a distance of 1 meter. The further away the listener is from the speaker, the lower the sensitivity. Therefore, a speaker producing 94 db from 1 watt of amplifier power at a distance of 1 meter will produce less sound pressure when the listener is 2 meters away. For a speaker to energize a room of 1000 cubic feet, for example will require significantly less amplifier power than to do the same in a 2000 cubic foot space. As a real world example, at the recent 2001 CES, Coincident demonstrated in a hotel suite of 1872 cubic feet using a 24 watt amplifier. To achieve similiar sound pressure levels and bass impact in another space of 7200 cubic feet, required 3x the amplifier power.With the same 24 watt amplifier in the much larger room, the sound was not as weighty, impactful or as dynamic as it was in the aforementioned smaller environment.

Conclusion-

With easy to drive speakers, like Coincident, many are afforded the opportunity of using low powered amplifiers like SETs with completely satisfying results. For those in a compact room, who listen at moderate levels to jazz , light rock, folk etc, then the inherent superiority of the best SETs will be appreciated. That is not to suggest that SETs are for everyone.They are decidely not. If your musical tastes are focused on big orchestral music, heavy rock, etc., and you listen at high spls in a large listening space, then small tube amplifiers may not be your sonic cup of tea. It would be recommended that a more robust amplifier be used.

Loudspeaker Impedance And Amplifier Matching
06/29/01

Solid State Amplifiers:
With transistor amplifiers ,the amp's output impedance is never matched to the load it drives.The lower the load impedance ,the closer it comes to a true impedance match , because the output impedance of a solid state amp is very low - typically a fraction of an ohm.This helps explain why (all things being equal- and the amplifier has sufficient current capability)4 ohm speakers produce greater acoustical output than 8 ohm speakers.The lower impedance speaker offers less resistance to current from the amp.The transistor amp sees less resistance into 4 ohms , therefore its output stage delivers more current.

Tube Amplifiers:
A tube amplifier's output stage(s) are totally different. A true match between the load impedance and the plate impedance ( or plate - plate impedance of a push - pull tube output stage) is never absolutely possible.The tube's plate impedance is typically exceptionally high
( thousands of ohms.) Therefore ,even a tube output transformer ( which becomes necessary to lower the plate impedance so that a typical speaker can be driven) with a primary impedance of 3K - 8K ohms will not closely approach this match. Therefore, it can be seen that the operation of tube versus solid state outputs is reversed. In the case of transistors, impedances cannot be matched due to the ultra low output impedance of the amp ,while with tubes, the match cannot be achieved because of the very high output impedances.

The output transformer in a tube amp lowers its impedance to a level where speakers can be made to operate and extract power from the driving amplifier. The output transformer is designed with a given ratio between the number of turns of wire in the primary and a nominal secondary impedance. For example, if we connect an 8 ohm loudspeaker to an amplifier with a primary impedance of say, 5,000 ohms and a transformer tap of 8 ohms, the primary impedance remains at 5,000 ohms and the amplifier delivers a given amount of electrical power. But ,if a 4 ohm speaker is connected to this amplifier, the output volume will diminish because the 4 ohm load causes a reduction of the primary winding impedance. This reduction means the amp's output transformer presents a poorer match to the plates of the tube output stage than it previously did.

On the other hand, if a 14 ohm loudspeaker is connected to the same 8 ohm tap, the primary winding's impedance is increased. The transformer represents only a ratio of turns and its impedance is determined by the load connected to it. Because the transformer's impedance has increased, it comes closer to matching that of the plate circuit. The result is greater output volume from the speaker.

In conclusion, a tube amplifier will produce more output ( greater voltage delivery) into higher impedance loads. Therefore , a 14 ohm speaker will be much more efficiently driven by a tube amplifier than will a 8 or 4 ohm speaker. This becomes of critical importance when using OTL or single ended triode tube amplifiers when available output power is low and amplifier output impedance is very high.

Available Options for Coincident Speakers