Tony L
Administrator
Veneered vs. non-veneered baffle?
An Epic Tale Of Two Celestion Ditton 66 Refurbishments
- Thread starter ToTo Man
- Start date
Veneered vs. non-veneered baffle?
ToTo Man
the band not the dog
Possible I suppose, but would that not affect the upper frequencies more than the lower frequencies in terms of its reflectiveness? I did paint the non-veneered baffles with semi-gloss paint so both baffles have comparatively similar shiny appearance', but the non-veneered baffle of course has more texture as I didn't sand it smooth before painting. I'm not convinced that the baffle finish would account for all of the difference I'm hearing though.
ToTo Man
the band not the dog
Replacing the T2169 drivers in my 2018 66's with earlier T1600 has brought the frequency response below 500Hz measurably and audibly closer to that of my 2015 66s:
(Note: All of the following measurements were made at a distance of 1 metre and on-axis with the MD500 unit, so may not be relevant for farfield distances).
Before:
After:
(Note: All of the following measurements were made at a distance of 1 metre and on-axis with the MD500 unit, so may not be relevant for farfield distances).
Before:
After:
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ToTo Man
the band not the dog
Out of curiosity, I then reversed the polarity on one of the bass drivers, to see what effect it had on the LF/MF crossover region. Reversing the polarity on the woofer decreases output between 300Hz-550Hz and increases output between 700Hz-900Hz. The midrange sounds more forward with less upper-bass bleed when the woofer's polarity is inverted, - I think I prefer this new tonal balance.
Below are the Phase Response and Step Response graphs, before and after reversing the woofer polarity. I could use a little help to explain the changes in these! I'd also be grateful for test track recommendations that provide the best/easiest opportunity for an unskilled listener to hear the difference when woofer polarity is reversed. So far all I'm hearing is a change in tonal balance, I don't detect a change in transient response.
Phase responses:
Step responses:
My Tannoy (Edinburgh) Monitor Gold 12 for comparison purposes:
Below are the Phase Response and Step Response graphs, before and after reversing the woofer polarity. I could use a little help to explain the changes in these! I'd also be grateful for test track recommendations that provide the best/easiest opportunity for an unskilled listener to hear the difference when woofer polarity is reversed. So far all I'm hearing is a change in tonal balance, I don't detect a change in transient response.
Phase responses:
Step responses:
My Tannoy (Edinburgh) Monitor Gold 12 for comparison purposes:
ToTo Man
the band not the dog
Thought I should update this thread with how my Ditton 66s have been tweaked since my last post. In short, nothing much has changed. I still have the polarity of the woofers inverted to provide a cleaner response through the LF/MF crossover area. I have however since taken time to integrate my subs. I'm running the 66s full range and have set the XO frequency of the subs to where the <40Hz roll-off is minimised but the >40Hz peak isn't added to. Getting this dialled in exactly was finicky but doable with Periodic Pink Noise, an RTA and a steady hand!
I have EQ'd the entire system in 4 areas:
1) notch filter at 48Hz to capture the 42Hz, 45Hz and 52Hz room modes;
2) notch filter at 130Hz to control a response peak;
3) wide notch filter at 750Hz to attenuate mid frequencies;
4) notch filter at 6kHz to smooth MF/HF crossover region.
I used measurements to guide me where to set the centre frequency for each notch filter, but I ultimately used my ears to determine what areas of the frequency response needed to be ameliorated and how much EQ should be used to achieve this. My approach was to use the least amount of EQ possible to obtain an even-handed sonic presentation that is detailed and transparent but has no areas that draw undue attention.
The BBC-esque dip at 3kHz is a classic feature of the 66 tuning, as is the 5kHz-6kHz bump. (The 5kHz-6kHz bump is most noticeable when listening on-axis with the mid unit, which is how I prefer to listen to these speakers). I found that EQ'ing the bump completely flat robbed too much excitement so I left a little lift in.
I verified all EQ adjustments by listening and measuring in several locations around my listening seat to ensure I ended up with a response that was balanced and didn't create more problems than it fixed. Sadly I didn't save all of those measurements so am unable to upload an average of them.
The following graph shows a before & after EQ from my listening seat, with the left & right speakers averaged into a single measurement:
Some will no doubt argue I've ended up with a tonal balance on the brighter side of neutral, and they are perfectly entitled to this opinion! As I say, I have not been led by target house curves, I have EQ'd the system so that it sounds both natural and neutral to my ears.
This was all done with the speaker grilles OFF. As much as I think these speakers look best with the grilles on, they do have a significant effect on the frequency response, knocking an average of 2dB off everything above 4kHz (the effect isn't entirely linear so I suspect the metal grid structure diffracts certain frequencies more than others), which is detrimental to the transparency/clarity and crispness of the presentation IMO.
Although it took some fettling to get there, these Ditton 66s in the current configuration are probably the most satisfyingly balanced and articulate 'big monitors' I've thus far had the privilege of owning.
I have EQ'd the entire system in 4 areas:
1) notch filter at 48Hz to capture the 42Hz, 45Hz and 52Hz room modes;
2) notch filter at 130Hz to control a response peak;
3) wide notch filter at 750Hz to attenuate mid frequencies;
4) notch filter at 6kHz to smooth MF/HF crossover region.
I used measurements to guide me where to set the centre frequency for each notch filter, but I ultimately used my ears to determine what areas of the frequency response needed to be ameliorated and how much EQ should be used to achieve this. My approach was to use the least amount of EQ possible to obtain an even-handed sonic presentation that is detailed and transparent but has no areas that draw undue attention.
The BBC-esque dip at 3kHz is a classic feature of the 66 tuning, as is the 5kHz-6kHz bump. (The 5kHz-6kHz bump is most noticeable when listening on-axis with the mid unit, which is how I prefer to listen to these speakers). I found that EQ'ing the bump completely flat robbed too much excitement so I left a little lift in.
I verified all EQ adjustments by listening and measuring in several locations around my listening seat to ensure I ended up with a response that was balanced and didn't create more problems than it fixed. Sadly I didn't save all of those measurements so am unable to upload an average of them.
The following graph shows a before & after EQ from my listening seat, with the left & right speakers averaged into a single measurement:
Some will no doubt argue I've ended up with a tonal balance on the brighter side of neutral, and they are perfectly entitled to this opinion! As I say, I have not been led by target house curves, I have EQ'd the system so that it sounds both natural and neutral to my ears.
This was all done with the speaker grilles OFF. As much as I think these speakers look best with the grilles on, they do have a significant effect on the frequency response, knocking an average of 2dB off everything above 4kHz (the effect isn't entirely linear so I suspect the metal grid structure diffracts certain frequencies more than others), which is detrimental to the transparency/clarity and crispness of the presentation IMO.
Although it took some fettling to get there, these Ditton 66s in the current configuration are probably the most satisfyingly balanced and articulate 'big monitors' I've thus far had the privilege of owning.
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davidsrsb
pfm Member
I wonder how the wood damping and density changes from 40 years of central heating. Quality musical instruments were made from wood seasoned for years to allow the material to stabilize.
ToTo Man
the band not the dog
Time to resurrect this thread once more!
After experimenting with in excess of twenty HF2000 tweeters, I have now settled upon a matched pair for my original 2015 refurbished 66s. I suspect this will be as a good as it gets when it comes to high-frequency pair matching.
1-metre FR before:
1-metre FR after:
This is how the new driver combo measures from the listening seat before & after EQ:
Listening seat FR before EQ:
Listening seat FR after EQ:
Listening seat average FR before & after EQ:
Was it worth the effort? I'm hardly going to say no, am I??!! The latest tweeters have smoother FR and less output than the previous ones and to my ears integrate better with the mids and draw less attention to themselves. Not a "night and day" difference, but still worth the hours spent listening to and measuring numerous pairings. Imaging has become even more stable and holographic as a result.
I've also changed how I listen to these speakers. The plywood plinths have been temporarily ditched and I now have them sitting directly on the carpet but tilted backwards. I've discovered this provides exactly the same benefits to midrange-treble cohesion as elevating the enclosures on 250mm high plinths, but with the added benefit of making it FAR easier to move the speakers out of the way when I want to listen to my Tannoys! Ideally I'd love my Tannoys to be on castors so that I could wheel them out of the room and place the Dittons closer to the wall, as the bass sounds a little anaemic to my ears (I suspect it's being adversely affected by SBIR, but that's a topic for another day!...).
After experimenting with in excess of twenty HF2000 tweeters, I have now settled upon a matched pair for my original 2015 refurbished 66s. I suspect this will be as a good as it gets when it comes to high-frequency pair matching.
1-metre FR before:
1-metre FR after:
This is how the new driver combo measures from the listening seat before & after EQ:
Listening seat FR before EQ:
Listening seat FR after EQ:
Listening seat average FR before & after EQ:
Was it worth the effort? I'm hardly going to say no, am I??!! The latest tweeters have smoother FR and less output than the previous ones and to my ears integrate better with the mids and draw less attention to themselves. Not a "night and day" difference, but still worth the hours spent listening to and measuring numerous pairings. Imaging has become even more stable and holographic as a result.
I've also changed how I listen to these speakers. The plywood plinths have been temporarily ditched and I now have them sitting directly on the carpet but tilted backwards. I've discovered this provides exactly the same benefits to midrange-treble cohesion as elevating the enclosures on 250mm high plinths, but with the added benefit of making it FAR easier to move the speakers out of the way when I want to listen to my Tannoys!
Ideally I'd love my Tannoys to be on castors so that I could wheel them out of the room and place the Dittons closer to the wall, as the bass sounds a little anaemic to my ears (I suspect it's being adversely affected by SBIR, but that's a topic for another day!...).
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ToTo Man
the band not the dog
Cheers Alan... if only I knew half as much about tape decks as I do about 66s!Excellent work Richard
Alan
They weren't a cheap commodity, were they? £160 was a piece of money back then.
ToTo Man
the band not the dog
If that were true I'd still have my 44s and wouldn't have cannibalised them for my 66s.
Still very nice speakers though.
Maybe sacrificing a pair of 44s is worth it for that last 10%!If that were true I'd still have my 44s and wouldn't have cannibalised them for my 66s.
Still very nice speakers though.
ToTo Man
the band not the dog
Let's hope so as there's no way I can revert and do an A/B comparison now that the 44 cabs are in landfill and the crossovers are 200 miles away!
On a serious note, I had the 44s in my possession for about 2 years before I gutted them. They were a lovely sounding pair of speakers, REALLY easy to listen to and pleasing on the ear. However, as a detail-chaser I ultimately found the the colouration in the upper-bass / lower-midrange too detrimental to transparency. The 66s suffer from the same issue to some extent but it's not as noticeable as the 44s also had cabinet coloration to contend with. Besides, I'm a sucker for a dome midrange driver!
PS - Before anyone disses me for parting out a heritage pair of speakers, the 44 enclosures were in pretty beat up shape. About a third of the lip on one cab was broken off, - looked like it had been devoured by a Rottweiler! However, I have no excuse for gutting a pair of B&O 5700 and 5702 other than being told by my parents I wasn't allowed to bring any more speakers into the house until I cleared some floorspace. I regret doing that as it would have been interesting to refurbish the crossovers and pit them against my 66s and see which came out on top...