Crossover in Castle Trent speakers

[NTS]

Hi all,

I have had a somewhat strange experience with a pair of Castle Trent speakers I bought via eBay a while back.

My initial impressions were of an extremely harsh treble. The first thing to check was the wiring / polarity, so I reversed the connections from the crossover to the tweeter - a bit of an improvement, but still not great.

I had already noticed that the crossovers had a total of six spade terminals - the left two being used by the tweeter, the right two the woofer, and two remaining unused in the middle. Being an inveterate experimenter I moved the left hand tweeter wire along one to the right hand unused central terminal.

The result was an immediate dramatic improvement in treble sound quality - sweet and smooth rather than shrill and harsh.

So my question is this - does anybody know why there are six terminals on this crossover, what they each of them do etc. I presume that the middle two (previously unused) connectors are not simply for a mid-range driver because (a) these bespoke speakers are two-way and (b) connecting one tweeter wire to a tweeter output and the other to a mid-range output would presumably simply not work.

I have contacted the re-launched Castle company for the relevant information, so far no reply. In any case many thanks in advance for any help with this somewhat vague and technically illiterate query.

[Inductor]

You know, a schematic or photos would help.

[NTS]

Hi Inductor,

Here is a picture of the Trent's crossover:



I made a mistake in my first posting, the tweeters were originally connected to the right hand two terminals, the woofer the left hand ones.

As you can see I have now moved the (reversed) left hand tweeter wire along one to the right-hand unused central connecting post, and also the right hand woofer wire along one to the left hand previously unused central connecting post.

The overall sound is dramatically improved, and again any information about the role of these six connecting terminals would be much appreciated.

Finally here is a picture of one of these beautifully finished, real wood veneer and hand-crafted driver equipped speakers:



Thanks again for the interest.

[Inductor]

I don't know what they are, and I can't see from here, but it could be a factory predesign for xover bi-amp that was never used. Post if any other problem. You could, certainly, get better caps for the tweeter. I can only see/imagine the two polyswitch going one for the tweeter and one for the woofer. Difficult to guess more. Maybe also the tweeter caps are not working properly.

[NTS]

Cheers for the info, and as I said before the speakers now sound as good as they look, no matter what is going on with the crossover!

[Richmond]

Hello NTS,

The answer to your question is, Yes, I do know why there is 6 terminals, I not only designed the PCB but also the Trent Loudspeaker.

I no longer work in the industry and I am currently away for the next 3 weeks, but when I get back I will put a “post on” to answer your question.

[Inductor]

Originally Posted by Richmond

Hello NTS,

The answer to your question is, Yes, I do know why there is 6 terminals, I not only designed the PCB but also the Trent Loudspeaker.

I no longer work in the industry and I am currently away for the next 3 weeks, but when I get back I will put a “post on” to answer your question.

I'm very interested in knowing the reasons of all such difficulties and mystery you gave to NTS.

[Inductor]

Off-topic: Richmond, by any chance do you know the type of speaker drivers on a Mordaunt-Short model MS5.30 (woofer+tweeter)?

[Richmond]

Hi Inductor,

There is nothing mysterious in my comments; it is purely that I need to access my archives / design data, which are now some 300 miles away tucked away in the loft.

Briefly the PCB has 6 spade terminals on, as the PCB was designed to accommodate all the smaller Castle range of Loudspeakers. The reason why there were 6 terminals is that the Castle Stirling had 2 x 15cm / 12 ohm bass units wired in parallel hence the 4 terminal on the left hand side and the 2 on the right hand side for the treble.

The reason why every PCB had 6 terminal fitted instead of 4 (which most of the models used) was for ease of production and more to the point a nice tag to solder thick 1.2mm wire on to without lifting the track due to heat and from a financial point, drilling extra holes costs money! This PCB board was produced in very large quantities which reduced the cost to production by over a third.

NTS has just moved the leads on effective common connections; I would need to look further as to the reason why there was an increase in audio output by moving the leads. There are some points to check, but I would rather give a full explanation later when I have all the facts in front of me.

I will supply more details later.

As regards Mordaunt-Short – not my speciality although Vic Sapsford who was the Sales Director of Mordaunt-Short owned Castle Acoustics Limited for a period of time.

My forte is Castle Acoustics limited from 1976 – 2004 as their Design Engineer / Service Engineer / Quality Control / Production / Historian etc, I am also well acquainted with all Wharfedale Loudspeaker product prior to 1980.

One of these years I will put the history together of Castle Acoustics Limited, how it was founded, the links between, Bill Escott- the original Managing Director of Castle (He was the Managing Director of Wharfedale Extension Loudspeakers before Rank purchased them) likewise Brother Phil Escott who was head of the Service Department at Wharfedale. Yes you have guessed he passed all the servicing of early Wharfedale Product to Castle as we were literally the only company who could build/rebuild units on a one off bassis. Indeed in the early stages of Castle history there was many a shared component due to joint purchasing by Castle and Wharfedale - although I am not so sure that the powers of be knew at Wharfedale!

[Inductor]

Originally Posted by Richmond

My forte is Castle Acoustics limited from 1976 – 2004 as their Design Engineer / Service Engineer / Quality Control / Production / Historian etc, I am also well acquainted with all Wharfedale Loudspeaker product prior to 1980.

One of these years I will put the history together of Castle Acoustics Limited, how it was founded, the links between, Bill Escott- the original Managing Director of Castle (He was the Managing Director of Wharfedale Extension Loudspeakers before Rank purchased them) likewise Brother Phil Escott who was head of the Service Department at Wharfedale. Yes you have guessed he passed all the servicing of early Wharfedale Product to Castle as we were literally the only company who could build/rebuild units on a one off bassis. Indeed in the early stages of Castle history there was many a shared component due to joint purchasing by Castle and Wharfedale - although I am not so sure that the powers of be knew at Wharfedale!

Isn't that great?! I hope you come out with a Richmond 'signature edition' model speaker or something of that genre - nice wood/compounds included, and maybe a kit - and all the valuable information you talk about, in the future.