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Sub Box

SUBWOOFER construction

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Sub box developed by Hertz R&D to achieve the best performance with Hertz ES.5 subs Construction


When building a subwoofer box, you”d better care for some details:

Use rigid, anti-vibration materials not to compromise the project acoustic performances. Employ high-density wood, MDF, multilayer sea wood, etc. All panels must be perfectly glued and sealed. Use a lot of good quality vynil glue, evenly distributed onto touching surfaces. To prevent all breathing, you can put a paste of vynil glue and sawdust (the one you get while working, for instance) onto all internal joints.
Use damping materials, like AZ audiocomp FONOMAT, onto internal walls in order to eliminate vibrations. In order to get a perfect match between the speaker and the box it has to be put into, always use the gasket between basket and baffle and firmly fasten screws gradually and simultaneously. Use the inserts given with the subwoofer in order to cosmetically complete the screws housing after fastening them.
Use at least one slanted wall in order to make the enclosure fit the car compartment, solve size problems and decrease the box internal vibrations. Consider the speaker overall dimensions when calculating volumes since it is not included in the indicated volumes. If you place the magnet speaker inside the box, add Total driver displacement to the volume of the box itself.
Don”t add tubes and ports overall dimensions to total volume calculation in case of Reflex, Asymmetric Bandpass and Double Reflex projects. You only have to add the volume of the type of support you use, i.e. the wooden panel in case of Reflex Port. Don”t put the box rear panel close to the speaker bottom plate. Place it at least 5 cm far from it, not to affect the correct functioning of the speaker rear vented hole.
When building a reflex box, remind that the closer the port is to internal panels, the longer it virtually seems, lowering frequency; thus, if you put the port next to a corner, make it about 30% shorter. The same extension has to be used when building rectangular ports. This type of port can be put in every corner of the box in order to solve possible size problems. After finishing your reflex box, please test it into your car compartment by changing the port length and, thus, frequency, or the quantity of sound-proof material into it. This is the only way you can be sure you get the acoustic results you want. By shortening the port or decreasing the quantity of sound-proof material, you increase frequency and get clearer, crisper bass; vice versa, bass will be deeper but less sharp.
If you want to build a bass section using several speakers, we suggest that you mount the same kind of subwoofer (same model and same number of voice coils) and that you configure all components in the same way. Build several equal enclosures, one for each subwoofer, or design a single structure divided into different boxes.
Power cables are very important because they directly affect the system damping factor. In the enclosed table, we show cable diameters, which we recommend according to length and applied power. The table refers to continuous power into 4 ohm load. When load decreases, the cable size will have to proportionally increase. Firmly secure the subwoofer boxes to the vehicle chassis through brackets, screws, nuts and bolts, to guarantee stability and safety while driving.
The amplifier gain level should be adjusted in order to keep power in a linear functioning area, without distortion or saturation that might damage the speaker. Cut-off frequency should be between 80 and 50 Hz, according to the configuration you use (direct emission like Sealed Box or Reflex Box or indirect emission like Asymmetric Bandpass or Double Reflex).
If possible, use subsonic filter by setting its cut-off frequency around 25 Hz. Avoid to use loudness or equalisers at low frequencies (<150 Hz): ENERGY ES subwoofers have full, smooth response and don”t need any corrections, that might cause the amplifier saturation or distortion.
The subwoofer connection phase determines acoustic results and needs to be tested by being listened to. It might be necessary to invert it according to the configuration of main speakers and of other electronic devices in the system. Make some listening tests in both ways and choose the solution you prefer.
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