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New Peerless STW350 subwoofer on the horizon...
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Old 22nd January 2018, 05:42 PM   #81
globalplayer is offline globalplayer  Germany
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Port area is very small, yes.
Especially for a high excursion driver.
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Old 22nd January 2018, 05:58 PM   #82
racingpht is offline racingpht  Canada
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Or, 2x STW15 + 4x 15inch passive radiator, so you can fill a sub with each surface of the cube, to get a perfect force cancellation
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Old 23rd January 2018, 07:43 AM   #83
gbullimore is offline gbullimore  United Kingdom
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in listening tests the pair of 10cm ports are quite acceptable, but careful flaring is needed,
of course you can increase the port area.
with 5kw and sine tones you could create audible port noise,

remember these are suggested design's to get you going, not an ultimate design guide.
i'm looking forward to seeing some creative DIY designs using this driver,

2xSTW and 2x18" PR would be interesting and force canceling,
the mounting with 2 drivers and 4PR would lead to a very cool looking sub.

my personal preference in sound quality would still be sealed though!
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Old 23rd January 2018, 11:50 AM   #84
TBTL is offline TBTL  Germany
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Quote:
Originally Posted by manninen View Post
did anyone check the frequency on this 176volt run? fs?
Such tests are best done around the resonance frequency (25 Hz for this woofer), as impedance peaks around there and dissipation will be low.

The impedance is plotted on a hard to read scale, though it seems to be around 35 ohms at 20 Hz. That would lead to a current of 176 / 35 = 5,0 A. Voltage and current are not in phase, so dissipated power would be lower than just the product of voltage and current (880 VA).

Last edited by TBTL; 23rd January 2018 at 11:56 AM.
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Old 24th January 2018, 04:37 PM   #85
gbullimore is offline gbullimore  United Kingdom
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ok, this is off-the-record data, not published spec.
below is some data showing the driver can achieve the displacements talked about,
bear in mind this is not an final production level driver, it's a beat up test unit, the production stock is actually better, but due to demand we don't have one to spare!
the odd looking gaps in the data is where the limits were adjusted and the system re-enlarged the signal.
there is a slight offset in the displacement data, due to the laser shifting slightly during the test. this driver puts a huge amount of force into the test rig.
also bear in mind that the RMS voltage on the graphs is not comparable to RMS sine signal. sine signal has a much lower peak to RMS ratio compared to the klippel stimulus voltage.
but from the graph you can see that 300V peaks do no lasting damage.
driver was connected with the coils in parallel !

Click the image to open in full size.

Last edited by gbullimore; 24th January 2018 at 04:39 PM.
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Old 24th January 2018, 05:14 PM   #86
5th element is offline 5th element  United Kingdom
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Quote:
Originally Posted by globalplayer View Post
For example...

here is a thread, albeit in german, where someone klippel`d 3 drivers:

IMD, HD, Xmax und Klippel - Vergleich und Bewertung von 3 Chassis - DIY-HIFI-Forum

- Monacor SP-8/150PRO
- Visaton GF 200 (coils in series)
- Faital Pro 8PR200


Calculated xmax:

-
Monacor: +-6mm
- Visaton: +-6mm
- Faital: +-5.15mm

(voice coil height/2 top plate thickness)
(Faital adds another 1/3 top plate thickness)


Measured xmax(10%THD):

Monacor: Xmax10 = 2.1 mm
Visaton: Xmax10 = 3.4 mm
Faital: Xmax10 = 4.5 mm
That isn't what I was meaning.

None of the manufacturers have exaggerated their xmax values based off of the purely mathematically derived value. Yes, they all fall grossly short of being linear out to that amount of excursion but most likely because the suspension/soft parts can't support that much in an adequate fashion.

By lying I mean that the mathematically derived value would = 5mm, but the manufacturer says it has 10mm, just to sound impressive.
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Old 24th January 2018, 09:40 PM   #87
gbullimore is offline gbullimore  United Kingdom
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Isn't adding 1/3 or 1/2 the gap height exaggerating?
10% THD is a fairly arbitrary figure to define a limit.
To be honest the fascination with excursion is a little odd if we think about it logically?
CEA 2010 or similar might be a better metric.
I'd like to see someone take it back to practical aspects.
E.g. who cares if it's a 15" or 4" driver as long as it produces the requires SPL at required distortion limit in a given cabinet size.
The practical aspects are cabinet size and useable SPL. Maybe with available amp power as a third boundary.
In reality it shouldn't matter if it's a long throw 8", short throw 18" or array of 16pc 2" as long as the performance in a particular physical package is as required.
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Old 6th February 2018, 06:11 PM   #88
racingpht is offline racingpht  Canada
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Quote:
Originally Posted by 5th element View Post
That isn't what I was meaning.

None of the manufacturers have exaggerated their xmax values based off of the purely mathematically derived value. Yes, they all fall grossly short of being linear out to that amount of excursion but most likely because the suspension/soft parts can't support that much in an adequate fashion.

By lying I mean that the mathematically derived value would = 5mm, but the manufacturer says it has 10mm, just to sound impressive.
At least I know Aura did it.

50.8mm(He) - 25.4 = 25.4mm (P-P xmax)

While quoting 50mm P-P

Aurasound NS18-992-4A 18" Subwoofer
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