DL8 modding

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Dr Bunsen Honeydew
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#91 Re: DL8 modding

Post by Dr Bunsen Honeydew »

Yawn, and another one crawls out of the woodwork. Do you have anything to say about Doc Mods or Dave's project, or are you also fishing for conflict. Have I spoken to you, have I rattled your cage. NO!

The beauty of this is each time one of you starts or fishes for off topic conflict it shows *normal* people exactly what is going on.
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Dr Bunsen Honeydew
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#92 Re: DL8 modding

Post by Dr Bunsen Honeydew »

Back on topic.

What I like about this project is it is breaking new ground, I have never Doc Modded with a horn tweeter. I had concerns that the interface may be problematic, so it is with interest and relief that everything is interfacing so well.
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#93 Re: DL8 modding

Post by pre65 »

Dr Bunsen Honeydew wrote: Wed Feb 01, 2017 11:37 pm (complete surprise) thank you Noddy.

There is another change before the steel, that is the final doping coat of Plastidip.
I try to be open minded about most things. :)

I know Dave, and trust his ears, so his findings are more meaningful to me personally.
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shane
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#94 Re: DL8 modding

Post by shane »

Dr Bunsen Honeydew wrote: Thu Feb 02, 2017 12:44 am Yawn, and another one crawls out of the woodwork. Do you have anything to say about Doc Mods or Dave's project, or are you also fishing for conflict. Have I spoken to you, have I rattled your cage. NO!

The beauty of this is each time one of you starts or fishes for off topic conflict it shows *normal* people exactly what is going on.
It was a genuine question. I'm following Dave's progress with interest, but the thread keeps being interrupted by controversy (and yes I do realise that I'm contributing to that, but I can't think of another way of addressing the issue). I'm puzzled as to why this happens on most threads that you're involved with and not on any others. I'm not attacking you or criticising you, I'm just wondering if you have an explanation.
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#95 Re: DL8 modding

Post by Cressy Snr »

shane wrote: Thu Feb 02, 2017 9:27 am
....but the thread keeps being interrupted by controversy (and yes I do realise that I'm contributing to that, but I can't think of another way of addressing the issue).
This is the way:

Image

Perfectly simple.
Things are only an issue, if the mind makes them an issue.
Last edited by Cressy Snr on Thu Feb 02, 2017 10:32 am, edited 1 time in total.
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Dr Bunsen Honeydew
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#96 Re: DL8 modding

Post by Dr Bunsen Honeydew »

Stupid question, why ask me, ask the people who are doing it, or answer it yourself as you are one of them. Don't bother replying as I wont respond anymore, lets get back on topic.
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#97 Re: DL8 modding

Post by Dave the bass »

Dr Bunsen Honeydew wrote: Wed Feb 01, 2017 11:37 pm

There is another change before the steel, that is the final doping coat of Plastidip.
PlastiDip will hopefully be done this weekend. Out of interest, I thought I'd weigh the mild steel plating 220mm x 180mm x 3mm thick steel plate (16 off) = 14.7Kg.
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#98 Re: DL8 modding

Post by Dr Bunsen Honeydew »

Seeing as the Eagles have been a success I am interested in trying horn tweeters, these look ridiculously cheap. Sometimes these PA / disco drivers are a bargain.

http://www.ebay.co.uk/itm/SoundLAB-Tita ... 0577418866
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#99 Re: DL8 modding

Post by Dave the bass »

Agreed, they're good, but (dotdotdot) I do need to pad mine down again a bit further I think.

I did a really long listening session on Friday and after a good 4 hours I felt the treble was too forward and in yer face TBH. In shorter bursts they sound very good (IMO), but long term more padding I'm hoping will fix the 'in-yer-face-ness'.

Also, WRT to these modded speakers, I like the way they work with a cheap Denon SS amp. they seem to REALLY suit it. Why? I dunno! They just sound 'tight n right'.
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#100 Re: DL8 modding

Post by Dave the bass »

'Erks' Alert! 2 steps forward, 1 step back possibly this weekend....

So...mindfull of the way the rubber parts have reacted to chemicals in the past, I thought it'd be best to try and avoid too much PlastiDip spluttering onto the rubbery surrounds and made up a simple template...
Image

And "Et Vwahlahr" as the French say...
Image

Then another coat....
Image

And whilst thats drying lets get busy with the Steel Plating...
Image

Whahey!
Image

It's all going so well....... but wait.... oooerrrr...
Image

Errr......close up...
Image

There seems to have been a reaction (again!) btween the Bison Kit and the PlastiDip in the centre of the speaker, looks like the PlastiDip has shrunk and melted a layer of the Bison Kit or summat. It's more cosmetic than anything but it does look pants!

Meh!

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Dr Bunsen Honeydew
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#101 Re: DL8 modding

Post by Dr Bunsen Honeydew »

The Bison obviously still not gone off (still has some volatiles). just use them it wont cause sound problems and in a week or two a light spray of Plastidip. Should look a lot nicer.
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#102 Re: DL8 modding

Post by Toppsy »

There seems to have been a reaction (again!) btween the Bison Kit and the PlastiDip in the centre of the speaker, looks like the PlastiDip has shrunk and melted a layer of the Bison Kit or summat. It's more cosmetic than anything but it does look pants!
Dave,
Having used solvent based impact adhesives extensively I have some concern in using this for doping driver cones. I am not surprised you have had a reaction. The volatile solvents in the Impact Adhesive you were recommended to use by Richard may have eaten away at more than is visible? It is a brand I have not used so cannot comment, still it would have been most helpful had Richard advised of this possibility with this brand of glue especially since he has stated this had happened to him in the past. Still water under the bridge.With time you may find the whole cone will part company with the rubber suspension surround. So I would be cautious not to drive the speakers too hard until you have complete confidence in the treatment process. However, Richard in his Doc Mods thread has categorically stated the whole process is fully reversible so there is nothing to fear in doing all the mods including the cone treatment. So nothing to loose. Having said all this I am pleased the end result to date is proving a worthwhile exercise with improved sound over the originals.

With the experience you have had I would air caution to anyone else attempting to dope driver cones with Solvent based Impact Adhesive. Perhaps best to use water based contact adhesive which does not have same volatile solvents. But this isn't cheap and is hard to find a supplier of small quantities.

Regards the in-yer-face treble from the Fostex FT17H horn tweeter; You will need to attenuate this more than with the inline resistor you have. As Richard does not seem forthcoming with suggestions of what value resistor to use may I offer the following suggestions:

1. The original mid-woofer was around 86dB efficient. The Fostex tweeter is rated as 98dB efficient. So you have a difference of around 12dB. Assuming a 'Z' of 8ohms for the tweeter and mid-woofer. To balance the efficiencies you will need a single inline resistor (10W minimum) of 23.85 ohms (say 24 ohms). However the 'Z' total will increase to 31.85 ohms using a single resistor. For this reason I do not like using a single resistor to attenuate a tweeter. I suggest you use a L-Pad to maintain the total 'Z' to 8 ohms. This will require R1 (serial) 6 ohms and R2 (parallel) 3 ohms to achieve the same attenuation.
2. However, by applying all the coatings of the impact adhesive and then the rubberised paint to the cones this will have reduced the efficiency of the mid-woofers by 1dB or 2dB, if not more. Therefore you potentially have a efficiency disparity now of around 13dB to 14dB. This will require a single resistor of 27.73 ohms (say 28 ohms), or 32.09 ohms (say 32 ohms) respectively to restore efficiency balance between the mid-woofer and tweeter if using a single resistor.

I hope the above is helpful to you Dave and good luck with the further mods.
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#103 Re: DL8 modding

Post by Nick »

However the 'Z' total will increase to 31.85 ohms using a single resistor.
Out of interest, why would that be a problem, its not as if you have any other crossover to worry about, you just use the new value when it comes to calculating the single cap. Should mean you can use a smaller value (cheaper or better for same price).
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Dr Bunsen Honeydew
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#104 Re: DL8 modding

Post by Dr Bunsen Honeydew »

Complete bloody nonsense and not worth replying to but....1/ there has never been damage to a cone from my doping, look at HFS. The only problem was the dome detaching but that was sitting in a pool of the stuff. I have used Kevlar, paper, doped paper, Bextrene and other cone materials in these mods with no problems 2/ this is an empiric subjective process, and will be subjectively judged, as I have said I have never used a horn tweeter so obviously it will need greater padding to a dome or cone, and that is no problem and DOES NOT need complicating the tweeter protection by going to a crossover. The WHOLE POINT is to avoid this.
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#105 Re: DL8 modding

Post by Daniel Quinn »

Toppsy wrote: Tue Feb 07, 2017 2:31 pm
There seems to have been a reaction (again!) btween the Bison Kit and the PlastiDip in the centre of the speaker, looks like the PlastiDip has shrunk and melted a layer of the Bison Kit or summat. It's more cosmetic than anything but it does look pants!
Dave,
Having used solvent based impact adhesives extensively I have some concern in using this for doping driver cones. I am not surprised you have had a reaction. The volatile solvents in the Impact Adhesive you were recommended to use by Richard may have eaten away at more than is visible? It is a brand I have not used so cannot comment, still it would have been most helpful had Richard advised of this possibility with this brand of glue especially since he has stated this had happened to him in the past. Still water under the bridge.With time you may find the whole cone will part company with the rubber suspension surround. So I would be cautious not to drive the speakers too hard until you have complete confidence in the treatment process. However, Richard in his Doc Mods thread has categorically stated the whole process is fully reversible so there is nothing to fear in doing all the mods including the cone treatment. So nothing to loose. Having said all this I am pleased the end result to date is proving a worthwhile exercise with improved sound over the originals.

With the experience you have had I would air caution to anyone else attempting to dope driver cones with Solvent based Impact Adhesive. Perhaps best to use water based contact adhesive which does not have same volatile solvents. But this isn't cheap and is hard to find a supplier of small quantities.

Regards the in-yer-face treble from the Fostex FT17H horn tweeter; You will need to attenuate this more than with the inline resistor you have. As Richard does not seem forthcoming with suggestions of what value resistor to use may I offer the following suggestions:

1. The original mid-woofer was around 86dB efficient. The Fostex tweeter is rated as 98dB efficient. So you have a difference of around 12dB. Assuming a 'Z' of 8ohms for the tweeter and mid-woofer. To balance the efficiencies you will need a single inline resistor (10W minimum) of 23.85 ohms (say 24 ohms). However the 'Z' total will increase to 31.85 ohms using a single resistor. For this reason I do not like using a single resistor to attenuate a tweeter. I suggest you use a L-Pad to maintain the total 'Z' to 8 ohms. This will require R1 (serial) 6 ohms and R2 (parallel) 3 ohms to achieve the same attenuation.
2. However, by applying all the coatings of the impact adhesive and then the rubberised paint to the cones this will have reduced the efficiency of the mid-woofers by 1dB or 2dB, if not more. Therefore you potentially have a efficiency disparity now of around 13dB to 14dB. This will require a single resistor of 27.73 ohms (say 28 ohms), or 32.09 ohms (say 32 ohms) respectively to restore efficiency balance between the mid-woofer and tweeter if using a single resistor.

I hope the above is helpful to you Dave and good luck with the further mods.
Whilst I like dissenting opinions as it is the stuff of dialectical materialism , there are a few facts that if listed dilute the efficacy of what you are saying .

1] The problem was with the dust cap only , nobody knows what the dust cap is made off , the rest of the drivers are made out of materials that are listed as fine to use with the glue .

2] There is a reason for the use of bison , a reason that would be negated with a water based alternative .

3] Nowhere is it stated that the whole "doc mod" process is reversible . Doping is obviously not. When you wrote that sentence just how did you consider it could be reversed ?

4] Your calculations on sensitivity and the value of the tweeter resistor , ignore the effect of the crossover components that are now removed and replacement capacitor . There is no hard and fast rule it is an empirical exercise not a theoretical one ,any suggestions by anyone based on theory would not be valid and in my experience your figures are two high but who knows . Wire wound resistors are however pennies and the tweeter can be tailored to room and personal preference by the judicious use of a value decided upon empricially .
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