|last update 07/12/2015
FAQs: Loudspeakerboxes / Lautsprecherboxen
|1. How can I calculate the capacity/volume of my loudspeaker-box?|
|2. What are Thiele-Small-Parameters?|
|3. How can I calculate something with the TSPs?|
|4. I don't have the TSPs. How can I get them?|
|5. I got the TSPs from the manufactor of the speaker. But the values are different from the table on your site. What's right?|
Hier sind die meistgestellten Fragen zum Selbstbau von
Lautsprechern in deutsch.
|1. Wie berechne ich das Volumen für meine Lautsprecherbox?|
|2. Was sind die Thiele-Small-Parameter?|
|3. Wie kann ich damit etwas berechnen?|
|4. Woher bekomme ich diese Parameter?|
|5. Die Daten (TSPs) vom Hersteller des Chassis weichen von denen in der Tabelle ab. Welche Werte sind nun richtig?|
1. How can I calculate the
capacity/volume of my loudspeaker-box?
If you don't have the exact parameters you can't simulate or calculate the volume or length of tube etc. Parameters... this doesn't mean only diameter, and max. Power, these parameters are called Thiele-Small-Parameters or TSPs. You need them for calculation.
2. What are
The TSPs describe the acoustic and electrical behavior of a loudspeaker in a special case.
The most importent params are the resonance-frequency fs, the equivalent-volume Vas and the quality/grade Qts of the woofer. You need these specifications for calculation of the capacity of a box. The most important params are:
|That's the look of the AC-Resistance of a 4ohms-Bass-Speaker in dependence of the frequency. The DC-Resistance (0 hertz) Re is 3.1 ohms. At freefield-resonance-frequency fs (here 30Hz) the impedance increases to its first maximum, so you get a quality Qts of about 0.400. The increase of Z to higher frequencies is the result of the inductivity of the speaker-coil and is here about 3mH.|
For decision is the EBP useful: The Efficiency-Bandwidth-Product is quotient of fs and Qes
or you use this: X = fs/Qts
With X you can recognize the best or a good combination of the loudspeaker to the acoustic system.
X <= 40 Transmissionline (TML)The easiest way is the contained Box. In a smaller volume increases the resonance-frequency of the chassis fc, so as the Quality Qtc (Quality of the chassis in a capacity). The Qts of chassis should be in that case between 0.4 and 0.6. A higher Qts (maybe between 0.5 and 0.7) will increase the the box-volume or / and produce worse precision and impulsivity. If you do the speaker in a contained volume, the quality (Qtc) and the resonance-frequency rise.
X about. 50 (40...80) contained systems / geschlossene Systeme
X about. 60 (50...100) contained bandpass-systems / geschlossene Bandpässe
X about 100 (80...120) Reflex / Bassreflex (BR)
X>= 120 for Hornsystems
Calculating of Bandpass- and reflex-systems isn't so
easy. The best way for that, using a
simulation-software, like the Freeware BassCADe.
You need a Qts of 0.3...0.4, for best performance, lower values does not produce enough low frequency sound pressure, higher values will increase the volume of the box for a good sound.
OK, here the formula for the Helmholtz-resonance-frequency:
sqrt... square-root, Quadratwurzel
4. I don't have the TSPs. How
can I get them?
They are different ways:
1st: the manufacter gives you the most important values (often you can find them on the manufact.-page)
2nd: Maybe they are on my side, here If you can't find them, please do not mail me, I don't have these TSPs.
3rd: search in other sources (maybe in web or cataloges)
4th: The final way (but the best) : You can measure and calculate for yourself. How? You need two impedance-graphs, then the software calculate the parameters. SW like BassCADe or you know the formulas...
They exist software (like Hobbybox) they can measure the parameters with help of PC-soundcard.
5. I got the TSPs from the
manufactor of the speaker. But the values are
different from the table on your site. What's right?
Sometimes manufactor change the speaker and keep the name. You don't know how was the measurement of the speaker. Usually you should measure with cold coil and soft membrane-hanger. But the values are not so exact, because lifetime and temperature have an importent influence of the parameters. So you get high tolerances.
Often some manufactures specify for their speakers low Vas- and Qts-values. For Marketing? Some comparriosons an further TSPs (manually measured) on www.northcreekmusic.com.