Doc Mods

Dedicated to those large boxes at one end of the room
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Dr Bunsen Honeydew
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#1 Doc Mods

Post by Dr Bunsen Honeydew »

I have a system for waking up all the dull lifeless boxes around (especially daft BBC designs). It is free to you in concept and can be done in reversible stages so you can prove the worth or not. Has been talked about lots at hifi subjectivist forum and tried by many members there, no one has gone back.

Stages (in this case for two way)
1 remove all wadding and damping panels from the speaker, block and seal any ports.
2 line the inside of the cabinet with steel plate
3 remove the crossover and replace with just a protecting capacitor and padding resistor on the tweeter
4 dope existing bass driver to control the response mechanically or buy the already doped drivers from HFS

Find music at last.
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#2 Re: Doc Mods

Post by Cressy Snr »

Nice to see you here Doc.
The mechanical method of controlling a bass/mid driver has a lot going for it, as anyone who has heard my
five foot Metronome speakers in my own home will testify.
If I steel plated a pair of five foot high truncated pyramids, I'd never lift the things,
so I haven't done that :lol:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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#3 Re: Doc Mods

Post by chris661 »

Sorry, but I can't agree with that lot.

Maybe at low SPLs, you might get away with a protecting cap on the tweeter. Which values would you recommend, by the way?
Anyway, I want a HiFi that sounds good with good recordings, but will also satisfy on a Saturday night when you want to rock out with Bon Jovi. Steep crossovers are essential for the latter, since low order crossovers really seriously take their toll on power handling.

Chris
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#4 Re: Doc Mods

Post by Cressy Snr »

Ah but Chris, you're a young whippersnappper who likes a system that will kick ass and take down names, us jaded old coves just want a system that'll play music.
First order crossovers done right and crossing over high enough, give music, I've used them, and yes you’re right, they don't like it up 'em if overworked, but do sound lovely at reasonable listening levels.
I've also used three way high order crossovers and IME (admittedly nearly 40 years ago) the resulting speakers had to be thrashed with a big amp to get them to come to life. They would go awesomely loud and stay clean, if the amps were up to the job, but at lower levels suffered from a lack of microdynamics and presence.
I remember hearing a Spendor BC3 setup, which boasted a "three way, 16 element dividing network" according to the blurb; It was about as exciting as watching paint dry. A pair of big JBLs with simple crossovers woke up half the street, but then they were enormously efficient and only needed a 10 watt amp to wake the dead.
Horses for courses.
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Paul Barker
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#5 Re: Doc Mods

Post by Paul Barker »

Dr Bunsen Honeydew wrote:I have a system for waking up all the dull lifeless boxes around (especially daft BBC designs). It is free to you in concept and can be done in reversible stages so you can prove the worth or not. Has been talked about lots at hifi subjectivist forum and tried by many members there, no one has gone back.

Stages (in this case for two way)
1 remove all wadding and damping panels from the speaker, block and seal any ports.
2 line the inside of the cabinet with steel plate
3 remove the crossover and replace with just a protecting capacitor and padding resistor on the tweeter
4 dope existing bass driver to control the response mechanically or buy the already doped drivers from HFS

Find music at last.
Serious question. How about open baffle, does the steel plate mod help that also? Or maybe black anodised aluminium? For that matter, no doubt doping the driver element helps with OB. So is this the dope used on model aercraft? By the way my only fault is I can'`t spell.
"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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Dr Bunsen Honeydew
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#6 Re: Doc Mods

Post by Dr Bunsen Honeydew »

Open baffle is a very good solution and solves most problems without introducing too many of its own. There are very few commercially available ones as they are not seen as an aesthetically good solution by manufacturers, apart from Jamo who make / made a very good one but at a ludicrously high price. So build from scratch = good solution. My point is how to turn a sows ear into a relative silk purse.

And for the daft post in denial, this is not theory it is empirical and work I have been doing for over 30 years which I decided to give free two years ago. And as with all these things the proof of the pudding is in the eating. There are many user of NVA Cubes in all their different form built to these principles plus a few others, and loads of people who have done the mods (JPW P1 or 2 seem to be a fav to mod) and on some very decent speakers not just sows ears and everyone of them has sung the praises and not returned to pre mod. You can read about them on hifisubjectivist.org

I also know of a high end disco in the early 90's that ran using mk1 Cubes built to these principles so SPL was not a problem. You set the cap and pad by ear but a good place to start is 3.3mfd and 12ohms.
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#7 Re: Doc Mods

Post by Paul Barker »

thanks
"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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#8 Re: Doc Mods

Post by Scottmoose »

With the best will in the world, I have some reservations. A number of questions immediately come to mind that may stand clarification:
...but a good place to start is 3.3mfd and 12ohms.
For what tweeter impedance?

-How does your system prevent uncontrolled excursion around the tweeter's Fs impedance peak if (like many tweeters) it does not use ferrofluid or large decompression chambers, and is expected to have reasonable dynamic range / SPL capabilities?

-How does this system prevent rising harmonic distortion due to excessive tweeter excursion (a 1st order electrical filter cannot prevent its excursion increasing below the crossover frequency without other measures being applied)?

-How does removing wadding or damping material from a speaker enclosure and substituting steel plates prevent the generation of standing waves within the box or reflections from passing through or modulating the moving components of the drive unit[s]?

-What compensation measures are applied to prevent the large quantities of steel affecting the electrical damping of the drive units?

-What advantages are obtained by creating a sub-optimal sealed box from a properly designed vented alignment?

-What quantities of damping material and locations for this are applied to drive units in order to 'control the response mechanically' and how is this varied to address the requirements of specific drive units, which have massive differences in their behaviour that cannot be equally addressed (nor even vaguely similar results be obtained)?

I am far from being a fundamentalist, and I cheerfully accept that the measurements we can take do not tell us everything. However, total rejection of any kind of design whatsoever does not strike me as being an especially good idea.
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Dr Bunsen Honeydew
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#9 Re: Doc Mods

Post by Dr Bunsen Honeydew »

Think what you like, question what you like, I will give you no answers, as there are none but what your ears tell you. I have said clearly this process is empirical, it was developed over a period of 30 years, as such, basically saying / questioning feck what the so called experts and convention say - what if!

There was a range of speakers built to the early stages of this in the early 90's, and reintroduced in mk2 form in the late 00's, so there is product that can be listened to and judged. About two years ago I decided to open my self up to the objectivists derision who can't see beyond the end of their noses (theory and test gear). I think nearly 20 members at HFS (hifisubjectivist.org) have so far started with the first stage, some have left it at that others have progressed through the stages to basically the only thing left of the original speaker being the cabinet. NOT ONE has reversed the process, that is enough proof for any normal person, apart from if you are one of the loony objectivists who insist that if people prefer thing with their ears then they are delusionary.

You are welcome to come and talk to them at HFS or I will publish a note there for some of them to come and talk here about their experiences. This process has been entirely subjective and about music, nothing else.
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#10 Re: Doc Mods

Post by Dr Bunsen Honeydew »

I really do not want to promote the commercial side of this but there are many user reviews of the commercial product which includes other design considerations that will maybe seem equally outlandish but are based on the room interface work (extended by me) done by Roy Allison.

There is a review section at HFS, I will post there asking people with experience to join and post here (if they can be bothered).
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#11 Re: Doc Mods

Post by Mudshark »

With the best will in the world Scott.....

Take a lump of cow, chop it up finley, bung it in a pan with a wee drop watter, onions, diced carrots, add seasoning......plate up with potatoes.

Voila......."Mince n Tatties"

Who would have thought - Measures shit & shouldn't really work.....Tastes smashing.

The proof is in the pudding. :D
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#12 Re: Doc Mods

Post by pre65 »

Oh my god, not Jammy395, I thought it was a Bunsen disciple. :(

As usual, bugger all content on the topic. :lol:
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Mudshark
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#13 Re: Doc Mods

Post by Mudshark »

My god its the annoying little tit noddy......... :bootyshake:
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Dr Bunsen Honeydew
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#14 Re: Doc Mods

Post by Dr Bunsen Honeydew »

And the irritating little tit appears again, I knew he wouldn't resist. Carry on with your childish disruption if you wish, where is the giant lettering and massive spaces between words you so enjoy inflicting on us. Last time I had nothing to defend and no motive to do it. If you have nothing to contribute to the thread apart from ad hominem and irritating injections why don't you just stay out of it for once, or are you once again determined to have conflict with me.
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pre65
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#15 Re: Doc Mods

Post by pre65 »

So Jammy polluting the thread is OK then, It's not as if he has ever tried Doc mods on speakers. :wink:
The only thing necessary for the triumph of evil is for good men to do nothing.

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