Resource to calculate, building and measuring Hi Fi Loudspeakers and more... Home Email Links Forums Tips "How It's Made"  Something about Espresso  Disclaimer For Sale Calculators Loudspeakers Projects My System My System CD Master Clock Generator Components explained  Recommended Records  Measurement Software  Calculate Tonearm/Cartridge Capability Phono Cartridge Specifications Acoustics About Acoustics Acoustical Measurement Basics  Acoustic Calculations Acoustic Glossary Absorbtion factors(Excel) Specials

 Saturday, December 15, 2018 782 users online

Back to overview

and what can you do with it...

Impedancecurves are essential for the vote of BassReflex enclosures.

The BassRelex alignment is through the impendance minimum between the two impedance peaks defined and therefore accurately determined only with a impedance measurement.

The formular:

fb = 48.4 * d / Sqrt(V * (L + 0.8 * d))

• fb = tuning frequency [ Hz ]
• d = Port diameter [ mm ]
• V = Enclosure volume [ liters ]
• L = Portlength [ mm]

The measured Reflexport alignement is 34.6 Hz

The Reflexport frequency is measured at 0 degrees Phase.
• d = 50 mm
• L = 110 mm
• V = 28 liters
fb = 48.4 * 50 / Sqrt(28 * (110 + 0.8 * 110)) = 37.34 Hz

The difference to the measured Portfrequency is 2.73 Hz

Calculate fb
 Port diameter [ mm ] Port length [ mm ] Enclosure volume [ liters ] Port alignment frequency  (fb) Hz

 Impedance curves are helpful to find enclosures leaks or too little, too much or incorrectly found damping material arranged. Improperly damping: Enclosure resonance at 220Hz Too much or improperly arranged damping material is recognized by flattened impedancepeaks without rizing the impedance minimum inbetween Leaks in vented systems make themselves felt through a less than optimal pronounced minimum between the impedance peaks. Leaky enclosure Here we have by not properly tightened the chassis screws a leaky enclosure produced. The impedance peaks becomes flatter, the minimum between them increases.

 A circuit error in the crossover is clearly show in the impedance curve of the loudspeaker. Defect capacitor in the midrange section A shorted capacitor in the impedance correction of the midrange driver.

Impedance measurements are an important systems tools for every loudspeaker builder

All measurement are done with ARTA