About Speakers for organs in General.......
The provision of the correct amplification and speakers is one of the most important aspects in any Hauptwerk or other digital organ installation. Of course, pretty much any speaker set-up will produce "a sound" but there are some fundamental rules to be considered when trying to produce believable pipe organ sound in any environment.
The use of P.A. speakers and amplification is generally not recommended because these types of speaker are designed to project sound as far as possible into an auditorium. Whilst this is all very well for a pop group or rock band it is not suitable for pipe organ sound.
With the exception of some very loud stops, most organ stops are relatively quiet. Individually, pipes do not produce very high volumes and it is only when they are combined with others that a greater volume is produced. In a real pipe organ, the combining of several individual pipes at the same pitch does not in itself produce a marked increase in overall volume. It has long been known that it requires as many as 10 pipes of the same pitch (speaking in a similar manner and individual volume) to double the overall volume of the particular stop. However, the addition of a pipe at half the original pitch (ie; the octave above) has the effect of increasing the volume of the original single pipe considerably. This is caused by the fact that a pipe at say 64Hz added to a second pipe at 128Hz produces not only both the pitches of the basic fundamental but also reinforces the "base" fundamental by the addition of a "resonant" tone generated by the difference between 128Hz and 64 Hz (=64Hz). This phenomenon carries onwards and upwards as additional pitches are added according to the physics of sound. Every additional basic pitch above the original fundamental one will continue to reinforce the original fundamental and this is what causes the glory of the pipe organ sound as we have come to know it.
Unfortunately speakers do not operate in exactly the same way as physical pipes and all sorts of complicated factors come into play such as intermodulation distortion. Short of providing a speaker for the equivalent of every pipe in an organ, all solutions must be seen as a compromise and all that we can do is try to get as close to nature as possible. Fortunately, we don't have to go quite so far as providing an individual speaker for every pipe but the closer we can get to this, the more convincing and authentic the resulting sound will be. In order to emulate the true pipe organ, the first thing is to provide as many speakers and amplification channels as possible. This is not ostensibly to produce volume of sound but rather to reduce the problems of the conflicting intermodulation distortion and other factors such as "point source". Put simply, the more amplification channels and speakers that are used brings one closer to the ideal of one speaker per pipe. Every reduction in the amount of channels and speakers used will result in a less accurate end result.
The sound of any individual pipe when heard up close can be very unpleasant indeed since there are all sorts of spurious components such as noise and clashing harmonics. It is the damping action of air, absorption of frequencies by the room fabric, distance and several other factors that results in the sound that is heard by the listener. Basically the environment in which the pipe speaks is filtered and modified by its surroundings. Therefore, the concept is to produce the basic sound of a real pipe through the limited resource of a speaker and allow the room and other factors to create the desired sound as far as is possible. P.A. speakers tend to throw out the original sound (together with all of the original and unmodified undesirable sound components) as far as possible which results in a loud noise but retains much of the unpleasantness pipes listened to at close quarters. Whilst this is possibly desirable for the lower pitched stops which rely on the movement of large quantities of air for their effect, have less higher harmonics and are therefore less affected by their environment) , it is definitely not suitable for the higher pitched voices.
We feel that the provision of multiple channels of amplification and tonally uncoloured speakers provides the most accurate means of producing convincing pipe organ sound which is why we advocate the use of studio monitor speakers. In themselves, these speakers are not particularly powerful but in combination, they produce something approaching the desired effect.
There are a number of excellent speakers on the market which meet the requirements above and will adequately fulfil the needs of most installations at a reasonable cost.
The German company of Behringer produces a range of suitable monitor speakers which can be used for organ installations and which claim a better than average flat frequency response. Although their figures show relatively high frequency "bass-line" figures which would imply that they only just cover the bottom notes of an 8' stop (64 hZ), in practice, they extend much further downwards and they will adequately handle the bottom notes of most 16' stops. Of course, pedal stops such as 16' Open Woods require considerably more power and dedicated sub-woofers should be used in these cases. On the whole, the Behringer speakers offer a fairly economical solution which sounds good. Care must be taken in setting them up using the various controls at the rear of the speaker and obviously positioning is as important as it is for any other speaker in an organ installation.
There are a number of different models available which can be supplied in active or passive versions. We tend to recommend the B2301A which has built in bi-amplifiers at 150 and 75 watts plus 8" long throw woofer and HF tweeter. Frequency response is exceptionally flat with little or no colouring and is officially quoted as being from 50 Hz to 21KHz. As stated above, the lower response extends down far enough to be able to handle as low as 32Hz for many 16' stops.
Current prices of the above model as of Autumn 2014 are £250.00 per pair.
The American company of KRK offer an extensive range of slightly more expensive models than Behringer and which also offer a decent quality of sound. They are perhaps a little more delicate and honest in their presentation and as such we prefer to use them for more gentle stops or stops for the Choir or Solo divisions. In common with the Behringer's, their actual frequency response is slightly better than their official figures would otherwise imply. Yet again, care must be taken in their correct setting up and positioning. The only thing against them apart from the slightly increased cost over the Behringer's is that they have bright yellow drivers which are more difficult to disguise from view.
As with the Behringer's above, there are a number of different models available and the model we tend to recommend is the ROKIT RP8 G3 model which is active. The bi-amplifier is rated at 100 watts and frequency response is quoted as being from 35Hz to 35KHz.
Current prices as of Autumn 2014 are £370.00 per pair.
A relatively recent development in speaker technology, the "Sound-bar" was designed for home cinema applications. Most soundbars consist of a single unit which contains several small speakers often together with a separate sub-bass unit. Using soundbars is a slightly different approach and the main advantage is that the units are relatively unobtrusive and small enough that several can be used in a multi channel environment. Quality varies enormously and price is no guarantee of how good this quality might be when applied to organ sound. An additional factor to be considered is that many soundbars have unsuitable facilities such as optical inputs only.
We spent considerable time trying out many models at different prices to find one that was suitable. Eventually, we found one that was admirably suited to our needs. This soundbar is made in the UK. Where are soundbar differs from the others is that it is capable of producing a stereo effect regardless of listening perspective thanks to its unique design. It is also capable of projecting sound a considerable distance from its source and we have used it successfully in a number of large rooms.
We have found that using soundbars to handle upperwork and mixtures in conjunction with other speaker units is very effective. Another useful application is for chamber organs where their small size and acoustic characteristics are ideal.
Average output power - Total: 250 W
Dimensions - Sound bar: 85 x 500 x 93 mm (H x W x D) - Subwoofer: 340 x 140 x 230 mm (H x w x D)
Weight - Sound bar: 2.2 kg - Subwoofer: 3.6 kg
Current price as of Autumn 2014 is £275.00.
There are several other makes of speaker available which seem to offer similar quality and capabilities to those above. Some are slightly cheaper and others are considerably more expensive. The latter reason really precludes us using them so far and we have had no reason so far to opt for any of the cheaper models. Since we have not actually tried most of them or heard them, we cannot offer a valid appraisal at the moment.
These tend to be considerably more expensive than "normal range" speakers and often offer far less "bang for the buck" than their prices might suggest. There are plenty of companies that claim to produce sub woofer speakers but few actually come up with the results that should warrant such a description. One exception are the models offered by MJ ACOUSTICS which produce a firm and accurate bass down to and below the bottom notes of a 32' at 16hZ. Their sub woofers can genuinely be described as such and they produce remarkable results from units that take up very little space indeed. The only thing against them is that even the cheapest models are expensive and their more capable models (in terms of power) can only be considered in situations where cost is not the main issue.
A suggested guideline in pricing for active speakers to be used in a Hauptwerk instrument would be from £300.00 - £400.00 per pair. For subwoofers, a starting price should be from about £500 for a single mono unit. (Please note that since bass sounds tend to lack specific stereo field information to an extent, many consider that a mono bass speaker is sufficient. Whilst the foregoing statement is true to an extent, we still believe that in terms of organ sound (in all but a few situations), dedicated left and right speakers and amplifiers are essential.
After a considerable amount of research and trial, we have found a suitable model offering an excellent price / performance ratio. The quality of these units is really superb and they are able to handle 32' stops with great power and projection. Their quality has been been compared independently with other models costing up to 5 times more such as those by REL. There are several models available in different finishes. The largest comes complete with a built in 500 watt MOSFET amplifier allowing 1000 watts peak. The driver is 12". They are quite bulky and exceedingly heavy but they do the job admirably. A single unit can be used to cover the bass octaves of the lowest pitched stops or two units can be used for a true stereo effect. specifications are as follows:
System Type: 95 Litre reflex tuned to 20Hz, cabinet manufactured from veneered 25mm MDF and Critically braced
Distortion: 5% 102dB @ 20Hz
Frequency Response at -3dB: 20Hz / In Room at 15Hz
Amplifier Input / Output Impedance: High Level 100K - Low Level 10K - Balanced 10K
Gain Control Range: 80dB
Drive Unit Impedance: 4 Ohm
Dimensions: 560D X 540H x 420W
Current prices as of Autumn 2014 are £575.00 each including high quality connecting cables and optional floor spikes.
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