DRIVE UNITS BY MANUFACTURER:
SPH-135C
DISCONTINUED BY MANUFACTURER - LAST BATCH, NO MORE AVAILABLE AFTER THIS.
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.
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 |
SPH135C, SPH 135 C
Thanks for the review Graham !
Will & Caroline
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
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
Friendly technical support
40+ years in the trade
UK family run business
Excellent customer service
Quick dispatch
Been looking for a supplier of replacement drivers for some years.
Willy's HiFi had just the parts at a good price and they arrived in a couple of days.
Excellent service. Even a personal thank you hand written on the invoice.
A quick delivery and the tweeters are perfect on my mission 753 freedom speakers. Easy to fit . Highly recommend.
I’m no expert when it comes to speakers, but after some research (and a strong recommendation from ChatGPT), I went with the SB Acoustics SB65WBAC25-4 as a reference full-range speaker in this size range.
Having now tested them, I can confidently say they’re probably the best speakers I’ve ever owned. The clarity is outstanding—every detail comes through with incredible precision. The bass is surprisingly full and punchy for a speaker this size, and they handle power impressively well. For anyone looking for a high-performance compact full-range driver, these are hard to beat.
Item as described and arrived quickly - and did the job. However, I suggested that anyone replacing speaker foam makes sure they have a very large pair of sharp dressmaking scissors as it was not easy cutting to size without producing a ragged edge (which I managed to hide short of a close inspection)!