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Achieving overall system integrity: one approach

fas42

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30 years ago I first achieved, and shocked myself, by getting "special" sound - which I also call convincing or competent audio reproduction. I didn't intend to do so, it just happened a result of a set of steps of refining, improving the system at the time - what apparently was given the title of POOGE by some people, but I was never aware of this "movement".

To kick off, as a I mentioned elsewhere I'll just focus on the speakers, because most people would tune into this as being a smart approach - but it's just part of the overall package. Anyway, just the speakers for the moment ...

The speaker were bought second hand from a friend, for some nominal amount - we had other speakers, but in the house at the time there was a very large open plan living space, and there were two proper "hifi" setups - vinyl at one end, CD at the other. And the completely different speakers, by Technics, were used for the vinyl, which was there first - we needed extra speakers for the digital setup, and she wanted to upgrade ...

They were B&W DM10s, this picture makes it easy to assess their size:

_MG_7427.jpg


(Takes a breather, heads off for some lunch ...)
 
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fas42

fas42

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What did it sound like, in "raw" form? Pretty decent, the sound was as "big" as the size of the speakers would indicate, there was a small "club" of enthusiasts who were pursuing the B&W trail, she who sold to me got the intermediate model from the next person in line, who went the whole hog - DM 801s! Everyone was on the digital bandwagon - there were endless repeats of the "Love Over Gold" album, everywhere. Listening to that on the big B&Ws I didn't feel that too much was being lost in the areas that appealed to me, compared to the DM10s.

Diving inside, it's just a chipboard box with some loose padding, tiny crossover board, attached to the box using the terminal posts - simple as:

s-l225.jpg


The Bass/mid driver is quite decent:

B-and-W-DM-10-23-Bass-and-Mid.jpg


Note the stupid push-on tags - these offended my engineering sensibilities, and the wiring is the usual variety of course. Since I had caught the Van den Hul bug which was rife at the time, and the speaker cable were the usual thick monsters it made no sense to have this standard flimsy stuff at the end of the journey - got some of the dark brown DNM "TV feeder cable" speaker wire which was nice and cheap, and had plenty of copper in it, was very stiff, you had to bend it beforehand to exactly match up to the end points, and soldered at both ends, replacing the old wire.
 
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fas42

fas42

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The crossover linked to terminal posts by what to me seemed poor engineering - relying on the pressure of nuts clamping a piece of PCB metal against part of the post. Classic weak link in a chain scenario - so, made the mechanical mounting purely a means of holding the board in place, and added a proper wiring link between the post and the PCB circuit. Having secured the contacts on that side of the post it didn't make sense not to do it on the other, so I soldered the spade connectors of the speaker cable to the external part of the post - this was never a brilliant connection because it was hard to get enough heat in exactly the right area to create a strong mechanical linkage; was always breaking initially but eventually it was good enough to get the job done.

The last tiny tune up was tighten the screws holding the drivers in place - these were relatively loose when I got the speakers, and it didn't make sense to have something trying to vibrate madly not secured as well as possible. The rubbishy chipboard didn't help of course, so I tightened these screws a number of times over a period of time until the material stopped compressing under the stress.

And that's it! I didn't touch the crossover components, the structure of the drivers, the carcase, or the wadding at all - they remained as per original to this day.
 
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fas42

fas42

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The major work was done on the structure positioning the speakers. Being bookshelf speakers, and there was nothing beside the electronics to put them on, it obviously meant that I would need to buy some stands, or create something equivalent. I can't remember what I may have looked at, but they all looked very flimsy, unstable - especially since there was carpet at the spot - they weren't going to do the job of keeping the carcase from rocking and bouncing around.

Having listened to quite a bit of stuff at dealers, it was clear that solid, big speakers sounded solid, and big! Didn't take much thinking to connect the dots, and surmise a large part of that aspect was due to the drivers not wobbling around in space while working hard - the vibrations of the carcase, and hence driver structures in small boxes sitting on softish surfaces must be modulating the sound - let's try to minimise that! One thing I noted on even the biggest and meanest looking speakers in the showrooms was that they were still quite wobbly - would go up to the side of them and push them with my little finger, and they would rock back and forth! This is just silly, I thought - they should feel like a huge lump of concrete, to do justice to the mass of the speaker itself.

So, I aimed for creating maximum stability of the speaker carcase in space. I decide that concrete was the way to go for a column; the idea of steel or such columns was too hard, they ring like the devil, and still don't create a mass structure. Do it the easy way of course, buy lumps of concrete from gardening supplies: two flat, square pavers for top and bottom, two square concrete building bricks to on top of each other becoming the column. These were joined together with a mastic suitable for concrete, strong enough that the finished stand could be picked by the top "plate"; while assembling I filled all hollow parts of the concrete blocks to the top with fine sand - more mass, less ringing. The finished column had no air spaces in it, and would have crippled you for life if it fell on your leg!

But these sitting on carpet were still useless in terms of stability - the, new, house was a concrete slab foundation, and speaker spikes were all around - trivially obvious was the solution to drill some holes in the bottom paver, and araldite three, not four spikes at the edges. When placed in position the column was pushed down hard, the spikes went clean through the carpet and underlay to the foundation, visually the bottom paver seemed to be sitting on the carpet but the column was effectively "grounded" to the slab - we were starting to get somewhere! Then, used Blu Tack, because it was around and an obvious choice, in the very corners of the bottoms of the speaker carcase, and pushed it down hard on the top paver to squeeze out the goo. The end result was very pleasing, in terms of how solid the overall felt when pushed against.
 
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fas42

fas42

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The final touch was that I decided that even more mass would help - I wanted to create the heaviest speaker/support combo that I could easily muster; and the trivial answer was to add weight on top of the speaker. Plenty of encyclopeadia type books around; I just created a tower of them on top of the carcase - it looked ridiculous, but it made it easy to experiment with the weight, by adding or subtracting books.

So, what had I got? Very solid, big sound of course ;) - the little bookshelf vibe had disappeared long time earlier, and in particular the impression of intense bass content was there in spades - extremely tight and impacting; treble was good too, courtesy of having a clean electrical path all the way from the cable to the voice coil.

Note that I never measured frequency response, phase, worried about the room, or the position of the speakers. Part of getting the best from this speaker setup was that I learned that they had to be given a very decent warmup - the crossover capactors were the OK Bennic bipolars, and I surmised they needed to be conditioned; plus the driver voice calls and suspension needed to settle down. We were in a buzz of enjoying music at that point, so the system was going continually, there was always a CD being played.

Of course, the sound wouldn't have been as good as it was if I hadn't played with the electrical bits in the rest of the rig - but that's another story ...
 

tomelex

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May I suggest a rotation schedule for the speakers, say every few years, by 180 degrees or 90 degrees. That is unscrew them, turn the appropriate degrees and screw or bolt them back in. Did it with my JBL speakers all along through the years, they are beffier than yours as far as weight but hey, you might add that to your tweak list. Gravity is hell on speakers as well as humans, hahahhaha.
 
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fas42

fas42

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Yes, Tom, interesting point! I have thought about such issues, now and again - and your approach makes excellent sense. One of the DM10s started to make scraping noises after many years, which I imagine could be caused by a severe case of your point, but I wasn't in the mood at the time to investigate properly. Finally the voice coil died, because there was too much friction happening - had a look and it was the back plate adhesive letting go, very, very slowly sideways - the whole structure went out of alignment.

So, next round, had to grab some other speakers to play with ... :).
 

RayDunzl

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May I suggest a rotation schedule for the speakers, say every few years, by 180 degrees or 90 degrees

Oh, no... I haven't done that. I don't think I can get to my woofers without me causing some cosmetic accident.

I've not heard them complain, though (18.75 years).
 
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