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B200 Sub woofer?

 
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Garethwatkins
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Location: Tring, UK

PostPosted: Fri Nov 18, 2011 3:04 pm    Post subject: B200 Sub woofer? Reply with quote

Hello

I have sadly cooked one of the bass units in my 104aB speakers. I am considering my options

1. Source another B200 which appears to be quite rare
2. Convert the remaining good B200 into an active Sub woofer using a suitable amplifier and enclosure. To be used with LS3/5a or Gale mini-monitors

I am tending towards option 2 as Mrs Watkins would prefer not to have 2 big cabinets filling up the lounge. Would the B200 be a suitable candidate?

Can anybody advise?

Regards

Gareth Watkins
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ColinR
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PostPosted: Fri Nov 18, 2011 4:21 pm    Post subject: Reply with quote

Contact www.wembleyloudspeaker.com/ or one of the other speaker rebuilders I've mentioned here from time to time.

Regarding your question from what "Speakerguru" has said in the past the SP1039 has a shortish throw so won't move vast amounts of air in a subwoofer application.

O.K. it was used in IMF TLS50 damped tapered reflex lines but those boxes are quite big.

Any chance of getting rid of the wife?

As your small speakers roll off from about 120Hz a couple of the cheaper crappy(?) subwoofers which will go that high may have to be sourced.
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proffski
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PostPosted: Fri Nov 18, 2011 9:19 pm    Post subject: Re: B200 Sub woofer? Reply with quote

Garethwatkins wrote:
Hello I have sadly cooked one of the bass units in my 104aB speakers. I am considering my options 1. Source another B200 which appears to be quite rare 2. Convert the remaining good B200 into an active Sub woofer using a suitable amplifier and enclosure. To be used with LS3/5a or Gale mini-monitors. I am tending towards option 2 as Mrs Watkins would prefer not to have 2 big cabinets filling up the lounge. Would the B200 be a suitable candidate? Can anybody advise?

Regards Gareth Watkins


104aB Big? Shocked
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speakerguru
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PostPosted: Fri Nov 18, 2011 10:06 pm    Post subject: Re: B200 Sub woofer? Reply with quote

Garethwatkins wrote:
...I have sadly cooked one of the bass units in my 104aB speakers...


That takes a bit of doing these days! In the 70s with dc coupled amps and warped vinyl you could get the coil out of the gap if you didn't use a rumble filter but nowadays.....!?! Go on....... tell us how you did it...

btw, no, hold out to repair them. Is the coil open circuit?
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proffski
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PostPosted: Sat Nov 19, 2011 12:48 am    Post subject: Re: B200 Sub woofer? Reply with quote

Garethwatkins wrote:
Hello

I have sadly cooked one of the bass units in my 104aB speakers. I am considering my options

1. Source another B200 which appears to be quite rare
2. Convert the remaining good B200 into an active Sub woofer using a suitable amplifier and enclosure. To be used with LS3/5a or Gale mini-monitors

I am tending towards option 2 as Mrs Watkins would prefer not to have 2 big cabinets filling up the lounge. Would the B200 be a suitable candidate?

Can anybody advise?

Regards

Gareth Watkins


SpeakerGuru has raised a valid point.
Many years ago I did build a couple of subwoofers based on the B200 but NOT using the variant in the 104aB.
They were mass loaded with bitumen pads to get the fs down and reflex tuned with Laphroaig whisky containers.
The pictures here are in a friends house after he bought them about twenty years ago, a bit tatty now but still woring well. The maximum SPL attainable is nothing to write home about! Note their size... http://s891.photobucket.com/albums/ac114/AndyGoloskof/?action=view&current=4J.jpg
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man standing in a bucket and trying to lift himself up by the handle.
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Garethwatkins
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PostPosted: Sat Nov 19, 2011 11:57 pm    Post subject: Reply with quote

Speakerguru. The amp went a bit bonkers, I am not sure what happened but there was definitely a dodgy connection somewhere which resulted in my home-built quad 405 sending 50Hz at full whack into the RHS unit. It all happened a bit fast...Presently using the old Yamaha CR620 which has been held in reserve for a couple of decades.

Proffski. The 104aB's are big to her. But if I can stash a big box in the corner of the room I might get away with it, especially with a pot plant on it.

ColinR No plans to get rid of the wife, and I would still need to get the diddy speakers off the ground somehow. I might pick up a cheapo sub from Richer Sounds to keep me going and see if I can get another SP1039. If that fails, look out on the big auction site for a pair of T27's and a single woofer.

I've also got a stonking great Philips 4522 reel-to-reel which needs to go back into action. Maybe Kef's out Philips in!
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speakerguru
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PostPosted: Mon Nov 21, 2011 5:38 pm    Post subject: Reply with quote

You didn't say if the woofer is open circuit. If it still measures ~6 Ohms and is making scraping noises, it could be recovered by someone who knows what they're doing.
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Garethwatkins
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PostPosted: Tue Nov 22, 2011 9:56 pm    Post subject: Reply with quote

Open circuit I'm afraid. The voice coil is pretty well stuck fast.
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Joddle
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PostPosted: Wed Nov 23, 2011 8:17 pm    Post subject: Reply with quote

The B200s (all types including yours) come up pretty regularly on Ebay and I have bought several over the years and never had a problem with any of them. I don't find them difficult to replace at all - just takes a few weeks to wait until some of the type you want come up (from someone you would trust) - but they always seem to come up in the end -
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Garethwatkins
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PostPosted: Wed Nov 23, 2011 10:20 pm    Post subject: Reply with quote

Yes I might hang on after all. Are there any issues with unmatched pairs if I got a single one? I am guessing that the crossovers have probably drifted over time, although they still sounded pretty good (until last week)
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Joddle
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PostPosted: Thu Nov 24, 2011 8:23 am    Post subject: Reply with quote

Garethwatkins wrote:
Yes I might hang on after all. Are there any issues with unmatched pairs if I got a single one? I am guessing that the crossovers have probably drifted over time, although they still sounded pretty good (until last week)


Hmm - that depends - I always try for matched pairs but to be honest I wouldn't know if that was not the case - in several speakers I have owned the DC reisitance was a little different from one chassis to another so I am not too sure that is a definite sign of a matched pair! - obvoiusly the nearer the DC resistance the more likely they are to be a match 0 and usually on the bay they come up in "pairs" anyway!
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speakerguru
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PostPosted: Thu Nov 24, 2011 11:36 am    Post subject: Reply with quote

Sorry to hear that. RIP.

104 and 104aB pre-date pair matching in production, so grab any SP1039 and that'll be as good as you would have got.
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Garethwatkins
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PostPosted: Fri Dec 09, 2011 9:42 pm    Post subject: Reply with quote

Well I got a replacement B200 ( well, 2 actually) and the 104's are singing again. I have also treated myself to a new set of caps from Falcon Acoustics so just need a rainy day to stick them into the crossover. Happy days!
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