All systems go ! Fountek NeoPro5i and NeoPro10i ribbon tweeters in UK stock.

All systems go ! Fountek NeoPro5i and NeoPro10i ribbon tweeters in UK stock.



Monacor SPH-135C Bass / Midrange

135mm / 5¼" Carbon Fibre Midwoofer.

The SPH-135C is a versatile drive unit from the Monacor 135 series featuring a woven carbon fibre cone, vented pole piece and diecast chassis. When mounted in correctly aligned cabinets this long throw unit is capable of reproducing bass that is surprisingly deep and accurate  - ported cabinets of around 14 litres can give an in room response extending down into the upper 30s (Hz) which is excellent for a driver of this size.

A fine replacement unit for a wealth of mainstream designs requiring a high quality 5¼ bass driver such as Rogers, Castle, Mission etc. Full details and dimensions can be found on the downloadable datasheet.

Key Features:

  • Woven Carbon Fibre Cone
  • Rugged Diecast Basket
  • Vented Pole Piece
  • Long Throw Design
  • Excellent Bass Response

Basic parameters:

Resonant frequency (fs) 40 Hz Nominal impedance (Zn) 8 Ω
Mechanical  Q factor (Qms) 4.48 DC resistance (Re) 6 Ω
Electrical Q factor (Qes) 0.43 RMS power handling 50W
Total Q factor (Qts) 0.39 Sensitivity (2.83V/1m) 88 dB
Equivalent volume (Vas) 17L Chassis diameter (pincushion profile) 133 mm


Here's the full datasheet:

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SPH135C, SPH 135 C

Customer Reviews

Based on 2 reviews
Ian Schofield
Castle Isis driver update

Great update to the original Castle drivers which started to crack anround the edges after many years of service.
More bass response and energy when playing rock tracks.
Would note that driver surround is slightly larger than original.

Thanks for the review Ian!

Will & Caroline

Mark Winterbourne
Castle IsIs replacement drivers Monacor sph135c

Ordered two of these to replace the original Castle IsIs units as over a period of 35 years the polypropylene cones had gone brittle due to UV degradation, a common occurrence, units arrived in quick time and came securely packed, they took 20 minutes to solder in and slipped straight in, they sound better than the original units as they develop quite a bit more bass something the originals were very light on, very good build quality, and most importantly, a very good sound quality I’ve just acquired a a pair of Castle Avons for £60 that need the same upgrade, I will certainly buy these again from Willys very competitively priced with a quick efficient service 10/10
Thanks very much Willys HIFI

Thankyou for your review !
Will & Caroline