'Perceive' Contruction Diary - Page 5

wigginjs · 12th March 2005, 07:39 PM

Just mount the top cabinet slightly further back than on the sub-cabinet. That way the baffle slope only has to bring the mid and tweeter into time alignment because the mid and subs are already aligned. See Andromeda.

ShinOBIWAN · 13th March 2005, 01:55 AM

Thanks Paul & Al.

Both issues raised warrant further investigation.

Bass can be calmed to a certain extent via PEQ in the active XO section but I agree its best if its not there at all.

So I'll build some rough and ready prototypes to see how they test.

I may use just 2 x L22's in each.

I've had a mess with the baffle tilted back and apart from a very minor drop of 2dB from 13.5Khz - 18Khz(the upper range of my testing equipment) its nothing to be concerned about. In fact it looks better than on axis since there was a steady rise from 10Khz to 18Khz.

David Gatti · 15th March 2005, 01:29 AM

Looks like it's going to be awesome.
I'm a little worried about your bass-driver impedance. 3xL22s in parallel right? That's hitting close to 2 ohms!

www.gattiweb.com

David Gatti · 15th March 2005, 01:31 AM

I think 2 x L22's is a better option and will give you the equivalent of a 12" woofer ouput capability, which is more than enough for music.

ShinOBIWAN · 15th March 2005, 04:23 AM

Cheers David,

Lovely work on the Delta's too.

To be honest I'm thinking 3 x L22's is somewhat excessive. I've built a single 30ltr cube with just one of L22's in and its deep, very tuneful, reaching flat into the early 30's after which output is negligible.

2 should certainly give me what I'm after and maybe even avoid a subwoofer altogether with a small LT and room gain.

I'm going to try an L22 in another box but with a Q of 0.707 to test the difference between that and the lower Q version I have now.

Hopefully I'll gain a little more speed, power handling and save a little space. I guess I'm not likely to lose a great deal of extension but I just want to be sure before I start work on the real thing.

vex0rg · 16th March 2005, 11:40 PM

Dear Shinobiwan

This is the third forum and fourth alias, I have had to track you down to!, can you please respond to my emails and let me know what is happening.

Thanks

Vexorg

ShinOBIWAN · 17th March 2005, 12:11 AM

Quote:

Originally posted by vex0rg
Dear Shinobiwan

This is the third forum and fourth alias, I have had to track you down to!, can you please respond to my emails and let me know what is happening.

Thanks

Vexorg

£10 was sent ages ago, must be 2 weeks now at least.

email me at: shinobiwan3264@hotmail.com and I'll pass along the track number.

ShinOBIWAN · 17th March 2005, 12:30 AM

Good news.

Just finished cutting virtually all the MDF for the bass section of the cabinet. There's been a few changes.

Firstly I scraped the matrix bracing arrangement as it seems somewhat redundant in a 40ltr enclosure not to mention it was going to swallow a considerable chunk of the volume. Instead I've opted for a heavy duty cross-braced arrangement. Should provide a similar level of stiffness to the originally planned matrix.

After taking onboard what was said about off-axis response re: the scan ring and performing pretty extensive tests with SW, I've made the bass cabinet 10cm shorter so as to better align the tweeter with the ear. I'm now looking at a near perfect flat response from 3Khz-20Khz using measurements made at the listening position with the test open baffles

So it looks very promising.

More importantly I've decided to go with just the two L22's per cabinet. I was intending to build another prototype enclosure to see how one would perform in a higher Q 20ltr enclosure, this of course didn't happen. Instead I choose to simply implement a 0.7Q enclosure with both drivers sharing the same volume of 40ltr and began cutting the necessary bits today. One sounds lovely in the test enclosure so I'm sure I'll be thrilled once I get all four bouncing

David Gatti · 17th March 2005, 02:08 AM

Great to hear of your progress.
Are you using MDF or plywood? What thickness?
I used MDF but in retrospect the greater rigidity of plywood may have been a better choice for the woofer enclosure. I'm going to add some more bracing now that I have them apart.
Hopefully we'll see some pics soon.
David

edjosh23 · 17th March 2005, 03:40 AM

ShinOBIWAN,

Any pictures of you progress so far? This sounds like a great project and I like those amps.

Josh

12th March 2005, 07:39 PM	#41
wigginjs diyAudio Member Join Date: Dec 2003 Location: Columbia, SC	Just mount the top cabinet slightly further back than on the sub-cabinet. That way the baffle slope only has to bring the mid and tweeter into time alignment because the mid and subs are already aligned. See Andromeda. __________________ The Four Chairs DIY Home Theater

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13th March 2005, 01:55 AM	#42
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	Thanks Paul & Al. Both issues raised warrant further investigation. Bass can be calmed to a certain extent via PEQ in the active XO section but I agree its best if its not there at all. So I'll build some rough and ready prototypes to see how they test. I may use just 2 x L22's in each. I've had a mess with the baffle tilted back and apart from a very minor drop of 2dB from 13.5Khz - 18Khz(the upper range of my testing equipment) its nothing to be concerned about. In fact it looks better than on axis since there was a steady rise from 10Khz to 18Khz.

15th March 2005, 01:29 AM	#43
David Gatti diyAudio Member Join Date: Mar 2004 Location: Melbourne, Australia	Looks like it's going to be awesome. I'm a little worried about your bass-driver impedance. 3xL22s in parallel right? That's hitting close to 2 ohms! www.gattiweb.com

15th March 2005, 01:31 AM	#44
David Gatti diyAudio Member Join Date: Mar 2004 Location: Melbourne, Australia	I think 2 x L22's is a better option and will give you the equivalent of a 12" woofer ouput capability, which is more than enough for music.

15th March 2005, 04:23 AM	#45
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	Cheers David, Lovely work on the Delta's too. To be honest I'm thinking 3 x L22's is somewhat excessive. I've built a single 30ltr cube with just one of L22's in and its deep, very tuneful, reaching flat into the early 30's after which output is negligible. 2 should certainly give me what I'm after and maybe even avoid a subwoofer altogether with a small LT and room gain. I'm going to try an L22 in another box but with a Q of 0.707 to test the difference between that and the lower Q version I have now. Hopefully I'll gain a little more speed, power handling and save a little space. I guess I'm not likely to lose a great deal of extension but I just want to be sure before I start work on the real thing.

16th March 2005, 11:40 PM	#46
vex0rg diyAudio Member Join Date: Mar 2005 Location: Dublin, Ireland	Dear Shinobiwan This is the third forum and fourth alias, I have had to track you down to!, can you please respond to my emails and let me know what is happening. Thanks Vexorg

17th March 2005, 12:30 AM	#48
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	Good news. Just finished cutting virtually all the MDF for the bass section of the cabinet. There's been a few changes. Firstly I scraped the matrix bracing arrangement as it seems somewhat redundant in a 40ltr enclosure not to mention it was going to swallow a considerable chunk of the volume. Instead I've opted for a heavy duty cross-braced arrangement. Should provide a similar level of stiffness to the originally planned matrix. After taking onboard what was said about off-axis response re: the scan ring and performing pretty extensive tests with SW, I've made the bass cabinet 10cm shorter so as to better align the tweeter with the ear. I'm now looking at a near perfect flat response from 3Khz-20Khz using measurements made at the listening position with the test open baffles So it looks very promising. More importantly I've decided to go with just the two L22's per cabinet. I was intending to build another prototype enclosure to see how one would perform in a higher Q 20ltr enclosure, this of course didn't happen. Instead I choose to simply implement a 0.7Q enclosure with both drivers sharing the same volume of 40ltr and began cutting the necessary bits today. One sounds lovely in the test enclosure so I'm sure I'll be thrilled once I get all four bouncing

17th March 2005, 02:08 AM	#49
David Gatti diyAudio Member Join Date: Mar 2004 Location: Melbourne, Australia	Great to hear of your progress. Are you using MDF or plywood? What thickness? I used MDF but in retrospect the greater rigidity of plywood may have been a better choice for the woofer enclosure. I'm going to add some more bracing now that I have them apart. Hopefully we'll see some pics soon. David

17th March 2005, 03:40 AM	#50
edjosh23 Minimalist diyAudio Member Join Date: Oct 2004 Location: Raleigh/Atlanta	ShinOBIWAN, Any pictures of you progress so far? This sounds like a great project and I like those amps. Josh

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