ScanSpeak subwoofer 26W/4558T00
Hypex DS 4.0 plate-amp

PART 2

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Copyright 2015 © Troels Gravesen

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CABINET    MEASUREMENTS

CABINET
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CONSTRUCTION PICS


Click left umage above to view large


Lefy: Fitting in braces. Now, there are A LOT OF HOLES AND CUT-OUTS to be made here!
Actually some 38 holes per cabinet. This took a couple of hours!
I used a wood drilling hole saw - believe this is the right name - rather than the router.


I started gluing the bracings so I could slide the whole structure into the cabinet from the front.


Using two straps and a few clamps turned out sufficient.


Mounting the plate amp.


Only little damping material was added: 30 mm egg crate foam in the three middle sections.


MEASUREMENTS
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Whenever referring to a setting on the dials, I use a clock scale, e.g. 1500 is three-o'clock, OK?

 

   
Above my default setting for my AT-3WC speakers. This is a summed nearfield response from 26W + passive-radiator.

 
        
Above the summed response of 26W and PR from the following setting (full volume for all measurements):
EQ level = 1400. EQ frequency = 1400
Green = PR response. Red = 26W response. Orange = summed response.
From left: Crossover frequency set to 1200, 1500, 1600 and 1700 respectively. Between 1200 and 1500 very little happens.


Above all the summed responses in one image.


 

Volume = 1700
Crossover = 1400
EQ-level = 1200, 1300, 1400, 1500, 1600 (blue) and 1700 (purple)
EQ-frequency = 1400

As can be seen, this makes very little difference. Only at 1600 and 1700 do we seen some significant rise in level at 20-40 Hz.
  Volume = 1700
Crossover = 1400
EQ-level = 1400
EQ-frequency = 0700, 0900, 1200, 1500, 1600 (blue) and 1700 (purple)

Given the settings of the other variables, this does provide some variation in level of 30-60 Hz range.


I wish I could give more solid recommendations for the settings with regard to various speaker sizes, but it really takes careful measurements and practical tests to make a a good integration of subs and satellites. And I even haven't touched the phase issue. There are a wide range of settings for phase and with the AT-3WCs I can clearly hear differences from changing the phase 180 deg, but further fine-tuning with the dial is trouble.
Take care with equalising! It's easy to get an almost flat response down to 20 Hz but even 10" subwoofer drivers have to work hard to cope with a pair of 90 dB speakers at loud levels. With more than average efficiency speakers we may soon start considering 12" or even 15" drivers.
Despite all reservations with regard to the plate amp, I can fully recommend the basic set-up. It truly extends the low-end and brings a more solid and powerful presentation, even with tiny 4+1 speakers, although the full Monty first comes with a speaker that already has a decent response below 100 Hz, like a good 6" or even better, an 8" driver in the main system.
These subs are keepers and will remain part of my stock components.