TL;DR - do I have adequate info to model a box with the limited info I have?
The story...
I recently, maybe foolishly, got a couple polk DR1242SVC drivers from P E in Ohio. I was hoping to use these shallow (110 mm) drivers in a box indoors and out... and have put some effort into extracting info from Polk. I got... some... see the pic attached. When I asked for explanation or additional data, I got the explanation below. But there is no info about the voice coil or the magnetic characteristics. Am I missing something? It seems without Bl and Xmax in particular I can't really model this driver. I could measure/estimate Xmax... and maybe even the voice coil size, etc. Looking at the definitions... maybe I could derive BL? Or just return these and get something better characterized Any help or suggestions would be appreciated !! (I also attach the WinISD file I made... I include a guess that Xmax is ~10mm)
I should probably add that the manufacturer does give recommended box sizes for sealed and "vented" saying sealed should be btw 1.25 and 3.5 ft3; vented 1.75-2.25... but no vent info for tuning
"MLSSA Sd / Added Mass
• Sd (cm²): Effective surface area of the cone. Larger Sd generally means more air movement = more bass output.
• Added Mass (g): The mass added during testing (typically for the added-mass method of T/S parameter measurement).
- Added mass refers to a known weight temporarily placed on the speaker cone during Thiele/Small parameter measurement, specifically to calculate mechanical parameters like Vas, Cms, and Mms using the Added Mass Method (also called the mass-loading method). Added mass is NOT a permanent part of the driver. It's a temporary tool used during testing to help extract mechanical properties. The accuracy of Vas and Mms depends greatly on the precision of this added mass and the measurement setup.
Fs (Hz) – Resonant Frequency
• Frequency at which the driver naturally resonates.
• Lower Fs means deeper bass response.
Re (Ω) – DC Voice Coil Resistance
• Resistance of the voice coil, relevant for amplifier matching.
- All are around 3.3–3.5Ω (likely designed for 4-ohm systems)
Res (Ω) – Mechanical Resistance at Resonance
• Resistance at Fs, reflecting both electrical and mechanical damping.
Qms – Mechanical Q
• Mechanical damping factor (from suspension/spider).
• Higher values = less mechanical damping (longer ringing).
Qes – Electrical Q
• Electrical damping from the voice coil and amplifier.
• Lower = tighter control, but might reduce efficiency.
Qts – Total Q
• The total damping factor of a speaker, combining electrical (Qes) and mechanical (Qms) losses.
• Qts = 0.51 falls in the mid-range:
• Not too tight (overdamped), not too loose (underdamped)
• This value suggests flexibility in enclosure types:
L1 & L2 (mH) – Voice Coil Inductance
R1 (Ω) – Voice Coil Loss Resistance
- Resistance due to eddy currents and other losses.
Vas (L) – Equivalent Compliance Volume
• Imaginary volume of air that has the same compliance as the speaker’s suspension.
• Bigger Vas = softer suspension (needs larger box)
Mms (g) – Moving Mass
• Total mass of moving parts: cone, coil, air load, etc.
• Affects sensitivity and response speed
- Higher Mms → lower efficiency but deeper bass"
The story...
I recently, maybe foolishly, got a couple polk DR1242SVC drivers from P E in Ohio. I was hoping to use these shallow (110 mm) drivers in a box indoors and out... and have put some effort into extracting info from Polk. I got... some... see the pic attached. When I asked for explanation or additional data, I got the explanation below. But there is no info about the voice coil or the magnetic characteristics. Am I missing something? It seems without Bl and Xmax in particular I can't really model this driver. I could measure/estimate Xmax... and maybe even the voice coil size, etc. Looking at the definitions... maybe I could derive BL? Or just return these and get something better characterized Any help or suggestions would be appreciated !! (I also attach the WinISD file I made... I include a guess that Xmax is ~10mm)
I should probably add that the manufacturer does give recommended box sizes for sealed and "vented" saying sealed should be btw 1.25 and 3.5 ft3; vented 1.75-2.25... but no vent info for tuning
"MLSSA Sd / Added Mass
• Sd (cm²): Effective surface area of the cone. Larger Sd generally means more air movement = more bass output.
• Added Mass (g): The mass added during testing (typically for the added-mass method of T/S parameter measurement).
- Added mass refers to a known weight temporarily placed on the speaker cone during Thiele/Small parameter measurement, specifically to calculate mechanical parameters like Vas, Cms, and Mms using the Added Mass Method (also called the mass-loading method). Added mass is NOT a permanent part of the driver. It's a temporary tool used during testing to help extract mechanical properties. The accuracy of Vas and Mms depends greatly on the precision of this added mass and the measurement setup.
Fs (Hz) – Resonant Frequency
• Frequency at which the driver naturally resonates.
• Lower Fs means deeper bass response.
- 8" = 45.56 Hz (less deep bass)
- 12" = 31.57 Hz (better for sub-bass)
Re (Ω) – DC Voice Coil Resistance
• Resistance of the voice coil, relevant for amplifier matching.
- All are around 3.3–3.5Ω (likely designed for 4-ohm systems)
Res (Ω) – Mechanical Resistance at Resonance
• Resistance at Fs, reflecting both electrical and mechanical damping.
Qms – Mechanical Q
• Mechanical damping factor (from suspension/spider).
• Higher values = less mechanical damping (longer ringing).
Qes – Electrical Q
• Electrical damping from the voice coil and amplifier.
• Lower = tighter control, but might reduce efficiency.
Qts – Total Q
• The total damping factor of a speaker, combining electrical (Qes) and mechanical (Qms) losses.
• Qts = 0.51 falls in the mid-range:
• Not too tight (overdamped), not too loose (underdamped)
• This value suggests flexibility in enclosure types:
- Suitable for sealed enclosures (tight, controlled bass)
- Also works in ported enclosures, though some optimization may be needed
L1 & L2 (mH) – Voice Coil Inductance
- Inductance values at different frequencies.
- Affects high-frequency roll-off.
R1 (Ω) – Voice Coil Loss Resistance
- Resistance due to eddy currents and other losses.
Vas (L) – Equivalent Compliance Volume
• Imaginary volume of air that has the same compliance as the speaker’s suspension.
• Bigger Vas = softer suspension (needs larger box)
- 12" = 43.13 L (requires large box)
- 8" = 8.65 L (compact box)
Mms (g) – Moving Mass
• Total mass of moving parts: cone, coil, air load, etc.
• Affects sensitivity and response speed
- Higher Mms → lower efficiency but deeper bass"
Attachments
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might help if I state my general goal-
a couple cheap, small, portable subs that I can hopefully hide around our open floorplan ... the family room opens directly into both the dining room and kitchen... effectively 3x 12x18' rooms together. Portable for convenience, will probably be wired and passive. I have no real DSP ability ATM, so applying filters is unlikely; just what I can get from the LFE channel, sent to a dedicated ~200 W amp. These will be to complement polk monitor xt20s and/or Dayton BR1s with the dennis murphy crossovers. Don't need to reproduce earthquakes... music probably more than theater... but more low is OK too ; )
I have a budget of ~300 USD for drivers. Enclosures I can make. I'd rather have 2 so I can moderate room issues.
a couple cheap, small, portable subs that I can hopefully hide around our open floorplan ... the family room opens directly into both the dining room and kitchen... effectively 3x 12x18' rooms together. Portable for convenience, will probably be wired and passive. I have no real DSP ability ATM, so applying filters is unlikely; just what I can get from the LFE channel, sent to a dedicated ~200 W amp. These will be to complement polk monitor xt20s and/or Dayton BR1s with the dennis murphy crossovers. Don't need to reproduce earthquakes... music probably more than theater... but more low is OK too ; )
I have a budget of ~300 USD for drivers. Enclosures I can make. I'd rather have 2 so I can moderate room issues.
Maybe you can measure the actual driver ts parameters with a Dats V3?
https://www.parts-express.com/Dayto...ter-Based-Audio-Component-Test-System-390-807 ($129)
Break the drivers in for a few hours before measuring them.
https://www.parts-express.com/Dayto...ter-Based-Audio-Component-Test-System-390-807 ($129)
Break the drivers in for a few hours before measuring them.