'LGT' Construction Diary - Page 57

ShinOBIWAN · 16th March 2007, 08:04 PM

Thanks everyone.

Quote:

Originally posted by richie00boy
Congratulations, I've just become an uncle as well, and my nephew was also premature and had to live in hospital for a bit. In fact I wonder if our nephews were in the same ward together!

Likewise and could well be! He was in the Royal Hospital at Calow.

Tenson · 16th March 2007, 08:08 PM

Congrats Ant!

You need to paint the speakers in bright prime colours to make them like like lego bricks.

ShinOBIWAN · 16th March 2007, 08:16 PM

Started appying the lead and treatments this evening.

The lead works really well and a good tap on the cabinet where its been treated reveals a substantial improvement in damping. However I quickly realised that it was madness to try and treat every panel in the enclosure what with the weight of lead and the enclosure itself. After a little thinking the best compromise was just to treat the mid enclosure. I figured this would be the most effective area because the mid will run up from 200hz and MDF has its main resonances above that point and also to help to damp the vibrations and waves coming from the bass driver, into the mid chamber and through the mid cone.

The bass section of the enclosure was treated with the 2mm bitumen + 10mm open cell foam and then the outer perimeter treated with a fairly dense fill of BAF. The area directly behind the bass driver has been left clear of any BAF so as not to overdamp the sound.

ShinOBIWAN · 16th March 2007, 09:06 PM

Quote:

Originally posted by Tenson
Congrats Ant!

You need to paint the speakers in bright prime colours to make them like like lego bricks.

Thanks Simon

ssabripo · 19th March 2007, 02:30 PM

congrats shinobi, from sunny florida! Tell your brother not to let Layten get too close to your speaker stuff....you never know what might happen!! he may become an addict like my kid became!!!

ShinOBIWAN · 20th March 2007, 11:21 PM

Quick question:

I've got some 0.6mm silver wire that I'm planning to use on the tweeter. Is one conductor for each polarity enough?

sq225917 · 20th March 2007, 11:42 PM

i'd say 3 would seem like a fine choice. 1.5mm should suffice, it does on all 3 pairs of speaker i have in the house and they are all rated over 100 watts.

no doubt there's a perefectly decent mathematical answer to the question.

toolkit · 20th March 2007, 11:49 PM

Quote:

Originally posted by sq225917
no doubt there's a perefectly decent mathematical answer to the question.

Can I steal that for my sig?

ShinOBIWAN · 21st March 2007, 01:57 AM

One of the bass/mid enclosures is ready for spraying. Only another 3 more to go

The cabinets are brilliantly dead, certainly the best I've built by someway. The midrange enclosure in particular has a very short decay after you knock on it.

I also tried something a little different with the volume of the mid enclosure. Aside from the 2mm lead, 2mm bitumen and 10mm foam on the walls there's also a tapered acoustic foam section at the rear which is about 6" thick tapering to 2" and in front of this is a 4" wedge. The aim of this was to prevent energy passing back through the mid. As a little test to satisfy my curiosity I wired up one of the 5" AT's and placed it in the mouth of mid enclosure of this completed cabinet and then also into one of the unfinished enclosures with no treatment. The conclusion was a huge and remarkable difference in favor of the treated enclosure.

That was all well and good as a bit of fun but I'm not sure how this implementation will pan out for midrange performance once the baffles are on. I've always liked to think that the rear wave should be killed but truth is its often better to harness it rather than take a brute force approach such as this. Listening is where I'll find my answers but I think already it shows excellent promise.

Here's a shot looking into the mid enclosure:

And finally the mid/bass enclosure:

Edit: Forgot to mention that I brought the electronic scales down to weigh him in. Nearly 46kg just on that one enclosure bit, add the baffle and the drivers and I bet its 65kg. I reckon a completed loudspeaker will be around 170kg or about 400lbs.

fgroen · 21st March 2007, 09:47 AM

Mucho Impressive!!!!!

Regarding the wiring of your tweeters:

0,6mm diameter silver wire equals a cross section of 0,28 sq mm. My first (intuitive) reaction is that it starts to be a bit thin.

A decent mathematical answer

:

Specific resistance (rho) of Silver is 1,6x10e-8 Ohm.m.

So the resistance of e.g 2 metres run of 0,6mm silver wire is (R=rho x L / A) apprx. 0,11 Ohm. This starts to have some significance. Thicker cross section is hence recommended. I would recommend at least 1-1,5 sq.mm cross section on that wire, reducing it's resistance to some hundreths of Ohms.

19th March 2007, 02:30 PM	#565
ssabripo diyAudio Member Join Date: Nov 2005 Location: miami, Fl	congrats shinobi, from sunny florida! Tell your brother not to let Layten get too close to your speaker stuff....you never know what might happen!! he may become an addict like my kid became!!! __________________ My humble HT setup...shared with my toddler!

20th March 2007, 11:42 PM	#567
sq225917 diyAudio Member Join Date: Jun 2004 Location: sheffield	i'd say 3 would seem like a fine choice. 1.5mm should suffice, it does on all 3 pairs of speaker i have in the house and they are all rated over 100 watts. no doubt there's a perefectly decent mathematical answer to the question. __________________ hoping to pick up some things.

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16th March 2007, 08:08 PM	#562
Tenson diyAudio Member Join Date: Feb 2006 Location: Kent	Congrats Ant! You need to paint the speakers in bright prime colours to make them like like lego bricks.

16th March 2007, 08:16 PM	#563
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	Started appying the lead and treatments this evening. The lead works really well and a good tap on the cabinet where its been treated reveals a substantial improvement in damping. However I quickly realised that it was madness to try and treat every panel in the enclosure what with the weight of lead and the enclosure itself. After a little thinking the best compromise was just to treat the mid enclosure. I figured this would be the most effective area because the mid will run up from 200hz and MDF has its main resonances above that point and also to help to damp the vibrations and waves coming from the bass driver, into the mid chamber and through the mid cone. The bass section of the enclosure was treated with the 2mm bitumen + 10mm open cell foam and then the outer perimeter treated with a fairly dense fill of BAF. The area directly behind the bass driver has been left clear of any BAF so as not to overdamp the sound.

20th March 2007, 11:21 PM	#566
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	Quick question: I've got some 0.6mm silver wire that I'm planning to use on the tweeter. Is one conductor for each polarity enough?

21st March 2007, 01:57 AM	#569
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	One of the bass/mid enclosures is ready for spraying. Only another 3 more to go The cabinets are brilliantly dead, certainly the best I've built by someway. The midrange enclosure in particular has a very short decay after you knock on it. I also tried something a little different with the volume of the mid enclosure. Aside from the 2mm lead, 2mm bitumen and 10mm foam on the walls there's also a tapered acoustic foam section at the rear which is about 6" thick tapering to 2" and in front of this is a 4" wedge. The aim of this was to prevent energy passing back through the mid. As a little test to satisfy my curiosity I wired up one of the 5" AT's and placed it in the mouth of mid enclosure of this completed cabinet and then also into one of the unfinished enclosures with no treatment. The conclusion was a huge and remarkable difference in favor of the treated enclosure. That was all well and good as a bit of fun but I'm not sure how this implementation will pan out for midrange performance once the baffles are on. I've always liked to think that the rear wave should be killed but truth is its often better to harness it rather than take a brute force approach such as this. Listening is where I'll find my answers but I think already it shows excellent promise. Here's a shot looking into the mid enclosure: And finally the mid/bass enclosure: Edit: Forgot to mention that I brought the electronic scales down to weigh him in. Nearly 46kg just on that one enclosure bit, add the baffle and the drivers and I bet its 65kg. I reckon a completed loudspeaker will be around 170kg or about 400lbs.

21st March 2007, 09:47 AM	#570
fgroen diyAudio Member Join Date: Nov 2005	Mucho Impressive!!!!! Regarding the wiring of your tweeters: 0,6mm diameter silver wire equals a cross section of 0,28 sq mm. My first (intuitive) reaction is that it starts to be a bit thin. A decent mathematical answer : Specific resistance (rho) of Silver is 1,6x10e-8 Ohm.m. So the resistance of e.g 2 metres run of 0,6mm silver wire is (R=rho x L / A) apprx. 0,11 Ohm. This starts to have some significance. Thicker cross section is hence recommended. I would recommend at least 1-1,5 sq.mm cross section on that wire, reducing it's resistance to some hundreths of Ohms.

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