Hsu buyouts

[mattk]

The 12" sub drivers look very appealing for the price:

https://www.parts-express.com/hsu-re...ofer--299-4044
https://www.parts-express.com/hsu-re...ofer--299-4020
https://www.parts-express.com/hsu-re...ofer--299-4022

[Unbiasedsound]

The 10inch HSU for $40.00 combined with the $75.00 matching HSU amp is a good deal for $115.00.

[RobertM64]

What would be the required port size for the 10" vented construction?

• Vented Volume 1.307 ft.³
• Vented F3 37.68 Hz

[RobertM64]

Some quick research reveals this 10" was used in the VTF-2 MK1 and MK2. Both are downfiring subs. The MK1 has one port, the MK2 has two. The plate amps used are the buyout 150W for the MK1 and the 250W for the MK2. I have not been able to confirm, but looks like the ports might be 3" diameter.

[Millstonemike]

What would be the required port size for the 10" vented construction?

• Vented Volume 1.307 ft.³
• Vented F3 37.68 Hz

Here's an analysis using WinISD box modeler ...

In each of the pics, the VTF-2 is modeled in two different vented box sizes at 200 W with a 4.0 diameter port. Blue is 1.37 ft³ box suggested on the PE site. Pink 2.2 ft³ as suggested by WinISD. Right click and open in new window for a full size version of each pic.

First Pic: The transfer function aka frequency graph. Notice that the larger 2.2 ft³ box has a flatter curve and extends much deeper in the low end. The 2.2 ft³ box has an F₃ of 30 hz. The 1.37 box has an F₃ of 37 Hz.

Second Pic: SPL. The smaller box peaks near 113 dB but the larger box provides a consistent 109 dB throughout its usable range.

Third Pic: Excursion versus driver Xmax. The excursion graphs are within limit sub 30 Hz. Translation: you can play this thing at max volume and it'll hold composure - for music. The infra-sonic stuff in home theater applications will cause it to lose composure at the loudest volumes.

Forth Pic. Rear Port Air Velocity: Both good with a 4" port of the depicted length for each box in the pic.

In the larger box, you'll get every note in the most demanding music (except for those multi-story church organ pipes). The shorter port should fit w/o issue. The smaller box is smaller. Its advantage. It will play most all of music as well, just not as technically accurate. I'd say you have to be an long time audiophile to really notice the difference. The longer port required fitted into the smaller box may be a build issue, Elbows are allowed.

This is net box volume. You have add the volume displacement of the ports inside the box into you gross internal box size (as well as bracing and some for the woofer itself).

[RobertM64]

Fantastic, thanks Mike. The 2.2 cu ft volume compares very favorably with the volumes of both the VTF-2 MK1 and MK2, I'm getting 2.1-2.2 cubic feet gross volume based on published exterior dimensions and assuming 3/4" walls.

[duronboy]

I don't understand the point of the PF-12100LPV with its 10.5mm xmax.

Somebody was saying they got the V-PF-12100LP as an upgrade to the JBL CS1214. I'm using 3.8 cu. ft. boxes tuned to 22hz, and I think they were using 3.5 tuned to 20. I didn't see much, if any improvement at 3.8/22hz, but I see even less at 3.5/20hz, if we account for xmax. With a 3.5/20 situation, both drivers are xmax limited to pretty much just 250 watts, so the extra 150 watts RMS isn't doing the HSU any good. I mean, you're that much further away from the thermal limit, maybe, so it's a peace of mind upgrade, if nothing else. Unless I'm missing something.

The JBLs are $50 all day long, and sometimes $30. I've been keeping an eye out for something that beats that and I just haven't seen it.

I know I prefer the appearance of the V-PF-12100LP, except for the bright white logo. The newer version of the CS1214 is an improvement over the old ones, but the V-PF with their large dustcaps are the best. Also, the magnets appear larger and the weight of the whole thing is almost double that of the JBLs. The BL product isn't notably better so ¯\_(ツ)_/¯

[Millstonemike]

... I mean, you're that much further away from the thermal limit, maybe, so it's a peace of mind upgrade, if nothing else. ...

The thermal limit is defined using a sine wave. Music is no where near as power dense as a sine wave, perhaps 1/2 to 1/3 as dense given my casual observations. So your already way down from the drivers thermal limit for a given wattage in reality.

[duronboy]

I still feel like I'd rather have a 400 watt coil rather than a 250 watt coil as I have seen some burned out coils where the suspension was perfect, but the coil burned up. It comes down to the xmax rating. If the HSUs had more, they'd be a no-brainer.

[RobertM64]

Here are the DATS v2 results for the HSU VTF-2 10" woofer currently on the buyout. I will probably build as a front firing woofer like the VTF3 MK1 shown here with a rear firing port.

image_80281.pdf





Measured T-S (DATS v2):

f(s) = 39.03 Hz
Q(ts) = 0.4679
V(as) = 35.14 liters (1.241 cubic feet)
SPL = 87.92 dB SPL 1W/1m
Nominal Diam. = 0 mm (0 in.)
R(e) = 3.445 Ohms
Q(es) = 0.5222
Piston Diam. = 214.3 mm (8.437 in.)
SPL = 91.57 dB SPL 2.83
Vrms C(ms) = 0.192 mm/N
L(e) = 1.116 mH at 10kHz
Q(ms) = 4.503
BL = 11.83
n(0) = 0.3815 %
M(ms) = 86.47 grams


T-S From Product Listing:

Thiele-Small Parameters
Resonant Frequency (Fs)38.36 Hz
DC Resistance (Re)3.202 ohms
Voice Coil Inductance (Le)1.114 mH
Mechanical Q (Qms)7.15
Electromagnetic Q (Qes)0.48
Total Q (Qts)0.45
Compliance Equivalent Volume (Vas)1.36 ft.³
Mechanical Compliance of Suspension (Cms)0.208 mm/N
BL Product (BL)11.53 Tm
Diaphragm Mass Inc. Airload (Mms)82.85g
Maximum Linear Excursion (Xmax)8 mm

[Brian Steele]

Le should really be measured at 1kHz for woofers (for subwoofers 100 Hz might be better, but DATS doesn't offer that option). Could you export the impedance data from DATS as a ZMA file and share it here please?

[RobertM64]

I have re-run DATS V2 with the woofer Le at 1KHz to get 2.778, changed substantially from the 1.16 at 10KHz. I also noted that the Qms from the product listing (7.15) is much different than actually measured (4.539). Does this have an effect on the box measurements previously provided? I have included the zma file.

[Brian Steele]

I have re-run DATS V2 with the woofer Le at 1KHz to get 2.778, changed substantially from the 1.16 at 10KHz. I also noted that the Qms from the product listing (7.15) is much different than actually measured (4.539). Does this have an effect on the box measurements previously provided? I have included the zma file.

Thanks for the ZMA file. I've attached a screen capture of the derived semi-inductance parameters for the driver, useful if you want to more accurately sim its response in a particular alignment. The inductance between 10 and 100 Hz is actually significantly higher than that at 1kHz (it varies from 5.8 to 4.3 mH) , and that will likely cause the response of the driver to roll off a bit earlier than expected.

I wouldn't worry too much about the change in Qms. The impact on Qts will be small.