SpeakerTalk

[willem-57]

Ok, i can try it, one of the above standing types are ok? They are indeed granules for fishtank filter purposes.The resun type is already packed in a open nylon netting, it's 250 gram, maybe put this in the upper chambers and get some BAF out?

[willem-57]

My plan is to put the carbon in the upper, smaller chamber. That way the B200 see's it as a bigger chamber and the sound wil be more in balance with the lower chamber that is 4 liter bigger, i hope

Question is now, how mutch should i put in? Begin with 100 grams, or more? This material expans the volume with a factor of 3. Rember that i will leave some of the acoustic foam, but the BAF has to go.

KEF's research shows that the apparent increase in volume achievable in practice can be as large as 3x. Still greater enhancements are feasible but rendered impractical because the activated carbon then adds too much internal damping.

Increasing the apparent cabinet volume by a factor of three equates to:
1.a 30 per cent (over a third of an octave) reduction in the bass corner frequency while keeping sensitivity and box volume unchanged;
2.a 4.8dB improvement in sensitivity while keeping bass corner frequency and box volume unchanged;
3.a downsizing of the cabinet internal volume by two-thirds while keeping bass corner frequency and sensitivity unchanged;

So this is the plan, as said don't know yet how mutch carbon i must use.

[SaSi]

I will dare a suggestion...

If you are able to drive each woofer directly from an amplifier using a sine wave generator and outputting a low output (say 0,1W) you could sweep the 20~50Hz range by 1Hz and see where the resonance frequency lies. Since the driver + cabinet + whatever you put in there creates a system with a new resonance frequency, you can check each driver+compartment and match resonances that way but adjusting filling, carbon content, etc.

That, assuming I have understood the sealed enclosure system correctly.

More knowledgeable members are welcome to comment.

[willem-57]

Good suggestion, but i don't have a sine wave generator , so that would be difficult to do. However i will just try to do it by hearing. As it is for now without the carbon it's already pretty good, only still a small bump in the lower region, say 70-120 hz . I think it's coming from the upper chamber because it's smaller.
First get the carbon and than we hear what is happening.

[willem-57]

Found a piece of airy fabric to make the bags for the activated carbon. Ask my wife if she will make them, me and a sewing machine.....
My plan is to make for each speaker 4 bags with the same amount of carbon, this way it is simple to tune the system.

This are the Kef ace bags that are placed into the cabinet, as you can see Kef is using not very mutch of it, so i think i also need 1 or 2 bags at the most.


My fabric for the bags.

[willem-57]

Got the A-C today, its rather a small granule, specially made for use with air, like smoking and other air filters etc. And indeed also too filter aquariums. As you can see my wife has made the textile bags for the carbon.

[willem-57]

Bags are ready, made several sizes/quantities, this way it's easy to test.

Activated Carbon
Acoustical Compliance Enhancement or ACE is the same process one can use to increase the cabinet’s internal Q value or bandwidth of our diaphragmatic absorber. Instead of replacing a carburettor with fuel injectors, we use a substance called activated carbon inside the diaphragmatic absorber. Activated carbon or charcoal has a high degree of porosity and is a powerful absorbing material. It is used to filter water and air. Activated carbon granules look like miniature meteors. Each granule of charcoal has numerous holes or pores in it. Each pore is a perfect place for sound to enter into and be absorbed. Each activated carbon granule has many pores and these pores translate into a large amount of surface area. If we could unfold one gram of activated charcoal it would equal anywhere from 500 to 1500 m2. One teaspoon of activated charcoal powder (about 3.3 gm.) has about the same surface area as a football field. This surface area translates into a tremendous potential to “absorb” large amounts of sound energy.

If the story above is treu, than i've here a surface as great as our planet.

small ones are 55 grams, the 4 middle ones about 150 grams, and the 2 bigger ones 212 grams.

[willem-57]

I have removed all of the BAF out off the upper chambers and put the 150 grams of AC into each of the upper chamber together with 2 pieces of acoustical foam as seen in the earlier published drawing, result is deep bas, but less pronounced as before. This is just a first attemp, will test more. I think it actually works

[willem-57]

Testing the whole morning and it really does something nice, bass remains deep but more controlled as with the BAF. It looks if the bass speaker cones are coming faster to a halt.
I've now put in to the upper chambers the 212 gram AC bags and put a smaller 150 gram into the lower (bigger) chambers. Result is good so far. But it remains difficult, because recording A (very nice one) sound now superb, but another (still good) recording is a little less, depending on the deep bass notes of the recording.



spelling correction by SG 14-6-15

[SaSi]

Nice progress

Don't underestimate that an excellent performing speaker will reveal the shortcomings of other parts in the chain, in this case a bad recording.

[willem-57]

Yes, that's true. But maybe i wanna try something else, as you can see the bag has 2 pipes witch are filled with the A.C. The A.C. that i got is in size the "rice" format, still it's also meant for speaker use. But when i put 1 of the 2 pipes full whit the bigger granules, than i have (maybe) best of both worlds.
The resun brand witch has granules, cost only about 5 euro for 250 gram's witch is enough.

[willem-57]

Testing a lot and now i've only put the upper chambers with the 212 grams a.c. The lower ones only have acoustical foam in it and at this moment Jacintha is playing and man .... its beautiful! So i will leave it this way.

[willem-57]

I've also put the crossover in the bigger lower chamber and added extra bitume plates in the lower aswell. Bass is now really good, even with fm broadcastings (classical radio) it gan go deep and stay's tight. Maybe i will improve the internal wires at some point, but first i have to finish another none Kef project: http://www.hifiloudspeakers.info/speakertalk/viewtopic.php?t=1719

[Parts]

An interesting project.

I still have an old pair of these in bits up in the loft.

My original pair were modded by me, initially a rewiring was done with some pretty expensive but damn stiff Audioquest cables which to be honest was pointless and good quality OFC would have sufficed, various cable models from the Audioquest range for the treble etc, with removal of the Stop protection circuit which really opened up the sound in my opinion (like cleaning a window) I had had issues previous with a dry solder joint and decided to fit an XLR in the Stop knob hole, the base of the original cab I had filled with concrete, then I added a 1" Birch plywood plynth and spikes.

It was the best sound I had ever got from the 105.4 for really minimal changes at the time, the stop removal improvement may well just have been due to the more direct soldered cabling and removal of the god awful multi connector strip.

The biggest thing for me though may well have been putting that weight into the base of the cab and anchoring it down with good spikes.

When I upgraded to 107's the Kef were handed through the family, eventually ending up back with me with a full coat of black gloss on heads and cabs.

The cabs had also some dry joints and damage.

Now I managed to get replacement cabs on the well known auction site, but those too got damaged, then one of the crossovers had a crack at the power input conductor so that had to be trimmed back and a new hole for a cable to be soldered was drilled, and there was some damage to the 110's.

I fixed up the bass cabs, got replacement T33's and B110's, but never sorted out the heads as a replacement set I did buy turned out to be for the original 105.2 and it's a different tweeter.

All sitting in the loft sigh, need to get myself more organized and back into this stuff. Sadly my 105.4 will never be as good as they were when i had them in their prime.

Not had the time or money to do anything audio related for the last however meany years, amazing what a throat infection can have you doing at 2 in the morning.

But I do like the look of that bass cab idea, did you state the cost of having those made?

I hope all of your forum regulars are well!

Edit,

The 105.4 and 107 head difference, there really is none, apart from they did not use the tilt bracket on the 107, a different size fixed spigot was bolted to the main head assembly, if i remember correctly teh dampening is more uniform and even as though poured/moulded but more to do with later manufacturing aesthetic than function, cell foam was grey not white, no LED indicator on 107 also.

[willem-57]

Hello Parts,

I only changed the cable's between the entrance > filter and filter > bass speakers, the mid and tweeter cables are the standard ones. On this moment the speakers are playing with the original standard capacitators. I also removed the activated carbon and put enough damping foam and a little BAF in them. As you can see the woofers have there own (little bigger) chamber, so it's now a mutch more dry and deeper bassnote. Sometimes i feel the table when playing on a normal level.
The 2 bass cabinets where made by a specialist, the black paint ive done by myself. They are very well made, all the glueing is done at an angle of 45 degrees, so you see no glue seams. And i used metal furniture gliders, works perfect on my stone floor and looks great.
Sometimes i look at newer (maybe better) speakers, f.i. pmc obd1 or spendors, witch are second hand offered, but the point is, the 105.4's are such fine and easy to listen too, no sharpness at all, but yet very good imaging and musical. So, i'll keep them.