Doc Mods

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Paul Barker
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#151 Re: Doc Mods

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Paul Barker wrote:
Dr Bunsen Honeydew wrote:Active is a crossover, a series of filters built around unity gain op-amps working at line level. It has similar if not worse musical problems associated with it. It is a pro solution not a domestic solution.
Absolutely, sold my Berrhinger active crossover premap long ago, no place in a subjective analogue home like mine.
But could make simple protective circuits like you speka of ta the speaker, except inherant in the map design. one amp per speaker. But would need to be very carefull there is no parasitic hf going on, certainly no high transconductance valves in the tweeter amp if this is its only protection from hf.
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Paul Barker
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#152 Re: Doc Mods

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I am enjoying this thread and learning and hoping everyone taking part keeps it on topic and respectful to the knowledge base of the originator whether you are or are not in agreeance. the thread is greta and deserves to be set free of personalities.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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DSJR
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#153 Re: Doc Mods

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B.B.C. wrote: My intended "nominees" are a pair of walnut Naim IBLs which it's a doddle to try the X/O mod with. Not so sure about doping given they have no dustcaps. I already took the foam out (but left a bit of long hair wool). Internals already have some steel plate.They are great with some music and just fail with other stuff, so not much to lose. They need to loosen up a bit, I feel. I keep them because I like the look of them and they take up little space.
IBL's had stout cabs and I think some form of panel resonance damping (I can't really remember, but I think they stuck some sort of 'block' stuck in the middle of each panel from memory and thick gooey tape stuck around each bass driver. The bass unit was a very cheap Mordaunt-Short sourced driver (the first SBL driver apparently cost Naim £6 each wholesale, so go figure), which was probably ok, but left balanced like a Kan, as IBL's were supposedly a Kan upgrade. The passive crossovers were 'deliberately' only just acceptable, as Naim wanted owners to go active and spend yet more thousands of pounds with them... The least said about the Scan tweeter the better, except to say it takes off at around 9kHz or so (the glossy chrome plating on string tone is partly due to this) and I grew to hate the bloody thing... Overall balance is 'refined Kan with less quack and a touch more bass.' You might get more headway by selling the Naim and Scan drivers and replacing with properly Doc-modded 5" drivers and Visaton tweeters, as they might better fit the metal mounting plates, which didn't do much to be honest I recall and were more of a sales pitch I think.

I'd try the IBL with the stock driver run full range to see how different it sounds to when fitted with a crossover. The phase-plug affair may just be enough (he says with all fingers crossed).
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Dr Bunsen Honeydew
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#154 Re: Doc Mods

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We had someone at HFS a while back saying he was converting a set of IBL to Doc Mods but I don't know if he went through with it.

Regarding lack of dust cap it is not a problem as I have done it with Royd drivers, some of which are the same. I can talk it through if and when it becomes relevant.
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#155 Re: Doc Mods

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Dr Bunsen Honeydew wrote:We had someone at HFS a while back saying he was converting a set of IBL to Doc Mods but I don't know if he went through with it.
It's here.

http://hifisubjectivist.org/viewtopic.p ... bl#p124837
The only thing necessary for the triumph of evil is for good men to do nothing.

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Dr Bunsen Honeydew
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#156 Re: Doc Mods

Post by Dr Bunsen Honeydew »

There is no more theory, you have it all. All it needs now is helping people with the nuances of doing it to different speakers.

Some HFS-ers notably a member from Netherlands called fretless just bought the cheapest load of crap he could find at eBay just for the fun of modding them. He was quite astonished at how they improved.
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#157 Re: Doc Mods

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Yes Bunsen I've got some very large Cerwin Vegas ported. They actually sounded pretty good. However one of the horn tweeters is fried. Cant recall the model, they are at the lockup cant go to it on a whim. But they have a large bass 15" I think. a midrange, a lot of crossover shenanigins.

Only question mark is I refoamed the bass units, possibly not well.

But anyway be nice to have a go with those, do you think there is mileage in that? Don't mind at all buying the visation tweeters, monwy isn't the issue.
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#158 Re: Doc Mods

Post by Dr Bunsen Honeydew »

It will be fun, in this case instead of padding the tweeter we may have to pad the bass driver :lol: :lol:
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#159 Re: Doc Mods

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Which Visaton Tweeter is it thta you like?
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#160 Re: Doc Mods

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Oooo, Paul, Cerwin Vegas? You planning on having a party? :roll:
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#161 Re: Doc Mods

Post by Dr Bunsen Honeydew »

I have used G 25 FFL 8ohm and G 20 SC 8ohm. I like both but the 20 is a fair amount cheaper. The 25 needs a bigger hole than the 20.
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#162 Re: Doc Mods

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Well Doc Bunsen and Greg, the price difference is insignificant, but if there are no advantages to the more expensive one, I'd get the smaller one as it would transfer to smaller projects. i.e. I have some Celestion 8" field coils which are very limited in bandwidth, so I plan to put them in an OB and put a tweeter with them. Currently I use a Saba Green cone tweeter helping them sat on top of the cabinet firing up, no crossover, just a cap. I prefer the sound with a really very small cap and with firing up for the ambience. I don't like to hera the tweeter, just as if using I don't like to hera the sub. Like these bretah of fresh air entrants to the forum, I make stuff at home for me and adjust on test to sound like what I want to listen to. If someone came here with spectrum analysers they would go away horrified. My hEraing is very specific to me and I know when I like whta I hear. That is usually something entirely different to what other people like judging by the horrible sounds thta come out of their speakers.

Now Greg I know that you have taken a different and very credible path with the dvaliet tuned to your speakers. That demo of a devaliet by your mate a few years back was flawless. It is an amaising method.

I could buy a devaliet and be done, for aslong as it lasts, but I couldn't renew it in my future, and I would be robing my daughters masters degree fund. So I am quite content muddling along as I always have.

The Cerwin Vegas sounded entirely different to a set of pro pa speakers. they were a model made for audio, and they did their job very well indeed.
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Paul Barker
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#163 Re: Doc Mods

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By the way Doc my best sounding speakers I made at home, which are still in the junk room, were single driver Graetz field coils, which to my hearing are very full range, and so organic thta to help them at the top or the bottom always netted a worse sound.

The amp I used ta that time was rediculously excessive. It had not a single capacitor in it. Power supply was choke input of course, with shunt valves doing all the smoothing in three stages. Not with amplifiers on the grid either, just the transconductance of the valve (572b's) did the correction.

The sound was amaising. Noone hear has heard it, there may be pictures i put up in the past. It was very low about 1 watt I think. I never brought those speakers to a meet, every one would be looking for the fane compression tweeter and the bass helper, and anyone everyone talking over the sound baout their own agenda. No the magic of such subjective satisfaction is in the beholder. A friend from here who doesn't want to be public heard the whole kit and was in agreeance with my findings.

I think there is a magic in the single driver open baffle made to the dimensions of the Quad 57. Something about that dimension for sure.

Maybe one day I'll go back to that type of system, but such an amp takes up the floor space of a lrge room just to produce a watt. There is no sound like it however, not even the devaliet though it comes second.

I must say is greta to be set free to talk wildly about stuff that would never sell in Currys or Richer Sounds.
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Mudshark
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#164 Re: Doc Mods

Post by Mudshark »

Doc mods........Doc shit........

Take a shit speaker....rip the stuffing out of it.
Add steel plates.....

Voila.....

What ya got .......A bauld shit speaker, that aint worth jack shit....now that yev ruined it.



SHIT.

:mrgreen:
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#165 Re: Doc Mods

Post by Mudshark »

TRUE.... :mrgreen:
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