Speaker enclosure tuning
All TRACE ELLIOT speaker enclosures have the facility of variable tuning, allowing any system to be uniquely tailored by the user to their particular preference or to better suit a particular venue.
A short description follows outlining the thinking behind this feature its principal and a few suggestions as to its practical use.
Firstly each speaker enclosure has two reflex ports tuned to appropriate lengths depending on the internal volume of the particular enclosure. These are easily identifiable by the Through the Grill custom moulded surround that neatly finishes the outer face of the port.
The tuning of the enclosure can be modified by plugging or unplugging either one or both of these ports, the resultant tuning is as follows:-
Both ports plugged = Infinite baffle enclosure
One port plugged = Reflex enclosure tuned to 35Hz
Both ports open = Reflex enclosure tuned to 45Hz
The only exception to this are the 1518 and the 1818 enclosures that are tuned to 25Hz and 35Hz respectively.
How does the tuning affect the sound
An INFINITE BAFFLE (both ports plugged) type of enclosure means a cabinet that is completely sealed i.e. nowhere for air to enter or be exhausted from the cabinet. In terms of sound this gives an extended low frequency response that is very even across the lower frequency range i.e. it has no peaks or dips in the bass response. However although the low end bass is very even and it extends further down the frequency range (below both the other tuning options) there is generally less of it than with either of the ported options.
A REFLEX enclosure has ports for the air from the rear of the speaker to be exhausted from the cabinet or be drawn back into the cabinet. The air in the port in fact oscillates back and forth through the port or ports and can either be in phase with the motion of the speaker and provide a boost to the level of sound or can be out of phase with the speaker in which case it in fact causes a cancellation in air movement and consequently a reduction in volume level. REFLEX enclosures are specially Tuned with the size and length of the port to a particular frequency that provides the correct rear loading to the speaker itself allowing it to work efficiently and safely and secondly to provide a bass boost at lower frequencies by using the air from the rear of the speaker through the port to add to the air from the front of the speaker, thus boosting the overall level of volume from the enclosure. This only happens when the air from the port is in phase with the air from the front of the speaker and this occurs at a frequency just above the tuning frequency of the enclosure.
However as with everything else in life you do not get something for nothing because at high frequency directly below the tuned frequency of the enclosure the air from the port is actually out of phase and consequently reduces the volume from the enclosure, this is usually at such a low frequency that in fact does not really matter when considering the range
of frequencies to be amplified. Providing the variable tuning facility gives the user the opportunity to experiment with tunings at both 35Hz and 45Hz to
find out which works best for them in a particular instrument. Remember that the bass boost is at a frequency just above the tuned frequency and that cancellation occurs at just below the tuned frequency.
How can this be used in a live situation Bass sound changes a great deal from one venue to another, for instance if your speaker enclosure is situated in the
corner of a room you will get a natural emphasis in low end from the walls of the room being at right angles. This can easily double the amount of bottom end in your sound just from the natural acoustics of the room. In this situation it would be best to plug both ports and use the infinite baffle response providing extended low end but less of it.
If on the other hand your speaker is situated backed on to the flat wall and not near a corner then less bass will be apparent, it would now be better to use the 45Hz tuning (both ports unplugged) to provide a bottom end boost. I suggest the 45Hz rather than the 35Hz because the speaker is better able to handle frequencies from the 45Hz upwards than from 35Hz upwards and you will consequently be able to have your amplifier louder before the speaker complains than with the 35Hz option. If you are however playing at lower volumes or in a studio recording situation you may well find the 35Hz tuning useful
as it will give natural boost to the bottom E string (42Hz) and above. Generally speaking, the loudness of your system will be in direct proportion to the number and size of the speaker cabinet you use.
Here are a few simple rules, which apply to any bass amplification system, however designed:-
1. If you need more volume, buy more cabinets (An AH300-7SM with two cabs will be louder than an AH400-7SM with one, for example).
2. The bigger the cabinet, the better the low end response.
3. A small combo is designed for sound quality with portability. Do not expect it to compete with a stack for more volume, add an extension cabinet.
4. Bi-amping should increase the quality (fidelity) of your sound, but will probably not increase the volume.
5. Doubling amplifier power will not double the perceived loudness of a system. (A 200 watt amp does not sound twice as loud as a 100 watt amp).
6. Bass frequencies are hard to amplify and are punishing on loudspeakers. To compete with a 100 watt guitar stack adequately you should use an AH400-7SM or AH400SMX with 2 cabinets.
