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Old 28th Nov 2018, 12:25 am   #1
vonrozen
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Default External cross-overs for the Rogers 5/8

Hello !

I have just bought a pair of external cross overs, developed by Derek Hughes and marketed by Graham audio especially for the Rogers 5/8 to enable the user to use any power amp and not be limited by the Quad 405 and its rather badly designed cross-over.

Has anyone had some positive experiences with this ?

Can it really improve the quality of the good old Rogers ?

Thanks

Alexander
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Old 28th Nov 2018, 8:30 pm   #2
Ted Kendall
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Default Re: External cross-overs for the Rogers 5/8

Quote:
Originally Posted by vonrozen View Post
the Quad 405 and its rather badly designed cross-over.
Apart from some accessibility problems, there is nothing wrong with the AM8/16 - I balanced plenty of stuff on standard LS5/8s. You will get a different sound - but better? I doubt it.
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Old 29th Nov 2018, 1:24 am   #3
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Default Re: External cross-overs for the Rogers 5/8

Dear Ted,

thanks very much indeed for your opinion, especially coming from you it has weight and relevance. A few more questions, would be great to hear your thoughts:

1. Don't you think that the possibility to use a nice powerful power amp might improve the rather restricted acoustics of the Rogers 5/8 ? I suppose what you want to say is that it would be better to spend the money (750 UKP !) on changing the capacitors of the Quads and the cross-overs there!

2. Derek Hugh's passive cross overs do not have voltage protection - could this pose a real problem ? Any way around it ?

Thank you very much for your ideas ! It would be of real help !

Kind Regards

Alexander
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Old 29th Nov 2018, 11:55 am   #4
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Default Re: External cross-overs for the Rogers 5/8

I'm rather of the opinion that the 5/8 was conceived as a whole, and it's best just to make sure it works as intended. There was a passive version back in the day - the Chartwell PM450 - and it worked well enough, but not as well as the active version.

Bear in mind also that the 5/8 was a professional tool rather than a hi fi speaker as such. It was designed to tell the balancer what he needed to know, so was honest to a fault. Tweaking will change the sound, but if you find it "restricted", we're in the realms of individual taste here, and you might be happier with another speaker altogether. Bear in mind also that the original bass driver has long been unobtainable.

To exercise personal taste of my own, I'm suspect of the 5/9 being quoted as an exemplar of mid-range clarity. The pair I tried to work with in the day were turkeys.
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Old 29th Nov 2018, 4:23 pm   #5
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Default Re: External cross-overs for the Rogers 5/8

Thanks so much, Ted;
So what you are saying is that I should be better off giving the Quads 405 a good technical clean-up and replacing what needs to be replaced than bothering with a 850 UKP cross-over. Understood - an excellent point !
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Old 29th Nov 2018, 6:00 pm   #6
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Default Re: External cross-overs for the Rogers 5/8

I am a little abashed to say that I have four pairs of LS5/8 speakers which I bought, cabinets only, when the lunatics in the auction company separated them from their amplifiers. Having spent several years searching for the AM8/16 units and leads and sending the power modules back to Quad for rebuild, I did find a few components had drifted on the powered crossover boards, I was pleasently surprised by the sound quality which came from them. I have had all the cabinet damage removed by a furniture restorer and to my admittedly older ears they sound to me as thay did when I had the pleasure of working in the organisation for twent nine years, twenty of which were spent in front of them in studio work! There are not many speaker designs available where you can take an amplifier and swap it out, or a cabinet for that matter, and carry on having checked for phase, position and level! This was one of the features demanded for this device. I shall never part with mine as I do not consider I will hear better units in my life. Considering the value of the units Quad do a very cost effective job on the amplifier modules but they do not work on the crossover as they did not make it. Most of the amplifiers were sent to Rogers who I believe had the crossovers built by third parties to a BBC designs department design and rettro fitted.
I know nothing about the passive crossover but do know that the amplifier feeding the Son Audax tweeter is limited in order to provide some measure of protection against burnout!
I would recommend you try and have the amps brought up to spec and listen to them. I also have a pair of the last iteration of the speaker with the Chord amplifier (BBC No AM8/20). Apart from going louder I cannot say I think it sounds better than a properly fettled Quad! You might enquire of DADA electronis in Belgium, if they are still going. They were/are great enthusiasts and offered upgrades for the amp modules and also offered what they claimed was a very clean new sound. I am going to stick with mine.
Good luck and more have fun!

regards
Mike
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Old 29th Nov 2018, 6:20 pm   #7
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Default Re: External cross-overs for the Rogers 5/8

Hi Alexander,

Just a quick reply - I've received your email, and will reply when I have some time. It might be tomorrow or later, as I have a busy evening tonight.

In the interim, I will say that it's complicated. The production LS5/8s were far from perfect and, importantly, were not what BBC R&D originally intended. Lots has been written about that - too much to get into now - but clearly BBC staff were able to work around the idiosyncrasies and produce good work with it. Having got used to the new generation of monitors used around the BBC, most are quite surprised when they go back to the LS5/8. The LS5/8 is fun and appealing, but it ain't neutral or accurate. Proper monitors - i.e., tools that are designed for a specific job - should not be fun or appealing - indeed, quite the opposite.

Quad 405s definitely benefit from a service - more so than many other amplifiers from that era because their performance depends on a number of electrolytic capacitors that cook themselves in there - but better amplifiers exist. For those who might doubt that, consider the favourable reaction the Chord AM8/20 (and AM8/21) got within the BBC. In larger spaces, the 100 watts from the Quad was not enough. Pete Thomas founded PMC on that particular premise.

I do like both the LS5/8 and the LS5/9 a lot, and I have huge respect for the work that R&D did back in the day, and I have plenty of nostalgia for them. Actually, that's not quite true, as we still have examples of them in use here. But with all that said, I can be objective about the imperfections of both.

All the best,

Mark
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Old 29th Nov 2018, 6:35 pm   #8
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Default Re: External cross-overs for the Rogers 5/8

I think that's the way it goes.

Have the speakers the way the developers intended, restore any damage and any aged components and then you should have what the originals were, capable of doing what they were designed to do.

If you disagree with the sound, and feel the need to do something to change it, then you are doing your own design. It's a bold step and easy to criticise by asking if you can replicate all the development cycles, testing, measurement and evaluation the originals went through. But your application may be different and everyone is entitled to their own opinion.

There are three dangers. If you take it on yourself, it is a big undertaking if you want to achieve the same legel of justification there is behind such originals. If you publish what you've done people will throw rocks at you. It's just what some people do. Most of them are clueless, a few have a bit of a clue and very very few really do know what they're up to. And thirdly, If you decide to buy someone else's designs, what makes you think they'll be any better? There is an awful lot of bull out there to wade through and sift out real info.

Happiness is hard to achieve.

I managed to eventually give up and divert my time to listening to new music. I feel easier about life.

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Old 30th Nov 2018, 7:16 am   #9
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Default Re: External cross-overs for the Rogers 5/8

"I managed to eventually give up and divert my time to listening to new music. I feel easier about life." You crack me up sometimes David : )

Andy.
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Old 30th Nov 2018, 9:52 am   #10
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Default Re: External cross-overs for the Rogers 5/8

Once I realised that sanity is a very fragile thing and has only precarious stability, I decided to develop a stable level of insanity which can be maintained long-term. It seems to be working.

David
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Old 12th Dec 2018, 10:04 pm   #11
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Default Passive Crossovers for Rogers 5/8 - your opinion

dear All,

what is your opinion of these cross overs by Derek Hughes of Graham Audio for Rogers 5/8 - only 200 were made. From the engineering POV does it look good or do you see drawbacks in the circuit ?
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Old 13th Dec 2018, 2:51 pm   #12
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Default Re: External cross-overs for the Rogers 5/8

Have you listened to them yet?
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Old 13th Dec 2018, 5:35 pm   #13
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Default Re: External cross-overs for the Rogers 5/8

Fair point - if they give you the sound you like, what's the problem? The construction, at least, doesn't look skimped.
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Old 22nd Dec 2018, 1:09 pm   #14
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Default Re: External cross-overs for the Rogers 5/8

Quote:
Originally Posted by mhennessy View Post
Hi Alexander,

Just a quick reply - I've received your email, and will reply when I have some time. It might be tomorrow or later, as I have a busy evening tonight.

In the interim, I will say that it's complicated. The production LS5/8s were far from perfect and, importantly, were not what BBC R&D originally intended. Lots has been written about that - too much to get into now - but clearly BBC staff were able to work around the idiosyncrasies and produce good work with it. Having got used to the new generation of monitors used around the BBC, most are quite surprised when they go back to the LS5/8. The LS5/8 is fun and appealing, but it ain't neutral or accurate. Proper monitors - i.e., tools that are designed for a specific job - should not be fun or appealing - indeed, quite the opposite.

Quad 405s definitely benefit from a service - more so than many other amplifiers from that era because their performance depends on a number of electrolytic capacitors that cook themselves in there - but better amplifiers exist. For those who might doubt that, consider the favourable reaction the Chord AM8/20 (and AM8/21) got within the BBC. In larger spaces, the 100 watts from the Quad was not enough. Pete Thomas founded PMC on that particular premise.

I do like both the LS5/8 and the LS5/9 a lot, and I have huge respect for the work that R&D did back in the day, and I have plenty of nostalgia for them. Actually, that's not quite true, as we still have examples of them in use here. But with all that said, I can be objective about the imperfections of both.

All the best,

Mark
Mark,

Interesting thread, I have been considering going down the LS5/8 route myself, then getting a pair of the passive crossovers to drive them passive.

I would have gone passive as I have amps which would vastly outperform the quad 405s even against the active 405 config.

I wonder how the lanter Graham LS5/8s (Volt bass) compare to the earlier LS5/8 with the Graham passive crossovers?

Simon
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Old 22nd Dec 2018, 1:15 pm   #15
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Default Re: External cross-overs for the Rogers 5/8

Quote:
Originally Posted by vonrozen View Post
Hello !

I have just bought a pair of external cross overs, developed by Derek Hughes and marketed by Graham audio especially for the Rogers 5/8 to enable the user to use any power amp and not be limited by the Quad 405 and its rather badly designed cross-over.

Has anyone had some positive experiences with this ?

Can it really improve the quality of the good old Rogers ?

Thanks

Alexander
My first instinct is the limiting factor in the BBC LS5/8 is the Quad 405 amps, the Chord version would I guess considerably outperform them.

It is always very difficult to compare active vs passive, as active drive will always have an advantage with like for like power amps.

If you have very high quality power amps then it is possible that there may be improvements, using the Graham passive crossovers; having never heard the Graham crossovers I cannot really fairly comment.

Be interesting to have your listening results / impressions, as I have considered this route myself.

Simon
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