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Large Advent improvements


Carlspeak

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Recently finished working on a pair of series A34XXXX speakers with orange tweeters and metal framed woofers and wanted to share some results readers may find of interest.

Three changes were made which seemed to improve the overall performance.

First, the crossover electrical components were replaced with modern, audio grade caps and resistors. The switch and iron core coil were left intact. A new 12 and 1 uF cap were wired in parallel to equal the original 13 uF electrolytic.

Second, the box was stiffenedd with new braces. I felt it failed the 'knock' test miserably. Original box wasn't braced at all. Braces were added front to back and on the sides and were screwed and glued in place.

Third, the five foam blocks were replaced with slightly over 2 lbs of OC fiberglass. Note that stuffing content was not optimized for absolute lowest Fc.

The attached report contains photos of the crossover, braces and OC FG. Two impedance and phase plots are included to show that box Fc was measurably reduced with the FG and, equally important, both impedance and phase variation was noticeably reduced - something amps typically benefit from.

It's all about the music

Carl

Carl's Custom Loudspeakers

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>

>And did it improve the performance, in your opinion? Let us

>know what you think, please. Thank you!

The last paragraph of my original post references the data in my attachment that shows an improvement has been made. Is it audible? Try it and you be the judge. It's not that much work to do.

It's all about the music

Carl

Carl's Custom Loudspeakers

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  • 3 weeks later...

Hi I was reading your post with interest in replacing the foam in my advents. I have a question though. Is there an alternative way to figure how much fiberglass to use. Like R-factor or inches thick. Sorry but I don't have a scale to accurately weigh 2.1 pounds and am hoping you could help.

Thanks Larry

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>Hi I was reading your post with interest in replacing the

>foam in my advents. I have a question though. Is there an

>alternative way to figure how much fiberglass to use. Like

>R-factor or inches thick. Sorry but I don't have a scale to

>accurately weigh 2.1 pounds and am hoping you could help.

>

>Thanks Larry

Yes, there is an alternative way and I'll answer your question on Monday.

It's all about the music

Carl

Carl's Custom Loudspeakers

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>Hi I was reading your post with interest in replacing the
>foam in my advents. I have a question though. Is there an
>alternative way to figure how much fiberglass to use. Like
>R-factor or inches thick. Sorry but I don't have a scale to
>accurately weigh 2.1 pounds and am hoping you could help.
>
>Thanks Larry

AS PROMISED........

The following is based on a single sample test, so don't take it as gospel.

I took a roll of standard OC R-13 fiberglass batting and cut 3 ft off it, peeled off the paper backing as best I could and weighed it. It weighed 9.7 ounces. The batting is 15 inches wide and 3 inches thick.

Therefore, to obtain 2.1 lbs you must cut off about 10 ft. and 5 inches from a similar roll.

For future reference, the weight rate is 3.2 ozs per liner foot of R-13 OC insulation or, conversely, it's 4 ft, 11.5 inches/lb. Box stuffing is not an exact science so you could use 5 ft/ lb.

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>>Hi I was reading your post with interest in replacing

>the

>>foam in my advents. I have a question though. Is there

>an

>>alternative way to figure how much fiberglass to use.

>Like

>>R-factor or inches thick. Sorry but I don't have a scale

>to

>>accurately weigh 2.1 pounds and am hoping you could help.

>>

>>Thanks Larry

>

>AS PROMISED........

>

>The following is based on a single sample test, so don't take

>it as gospel.

>

>I took a roll of standard OC R-13 fiberglass batting and cut 3

>ft off it, peeled off the paper backing as best I could and

>weighed it. It weighed 9.7 ounces. The batting is 15 inches

>wide and 3 inches thick.

>

>Therefore, to obtain 2.1 lbs you must cut off about 10 ft. and

>5 inches from a similar roll.

>

>For future reference, the weight rate is 3.2 lbs per liner

>foot of R-13 OC insulation or, conversely, it's 4 ft, 11.5

>inches/lb. Box stuffing is not an exact science so you could

>use 5 ft/ lb.

>

Just some additional thoughts on the above:

1) The density of the OC FG uncompressed calculates to 0.64 lbs/cu. ft.

2) With 2.1 lbs stuffed into a 1.68 cu ft cabinet indicates the FG is being compressed to about double its original density.

It's all about the music

Carl

Carl's Custom Loudspeakers

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Here is another facet of the improvement project which may be of iterest.

Following installation of the new caps and resistors, etc. I measured the response of the tweeter at the three switch positions. The attached response chart shows exactly what happens at each switch position.

The plateau in the lower frequency range isn't ideal for this exercise because the woofer was also functioning at the time of the close miked readings of the tweeter.

It's all about the music.

Carl

Carl's Custom Loudspeakers

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  • 7 months later...
Recently finished working on a pair of series A34XXXX speakers with orange tweeters and metal framed woofers and wanted to share some results readers may find of interest.

Three changes were made which seemed to improve the overall performance.

First, the crossover electrical components were replaced with modern, audio grade caps and resistors. The switch and iron core coil were left intact. A new 12 and 1 uF cap were wired in parallel to equal the original 13 uF electrolytic.

Second, the box was stiffenedd with new braces. I felt it failed the 'knock' test miserably. Original box wasn't braced at all. Braces were added front to back and on the sides and were screwed and glued in place.

Third, the five foam blocks were replaced with slightly over 2 lbs of OC fiberglass. Note that stuffing content was not optimized for absolute lowest Fc.

The attached report contains photos of the crossover, braces and OC FG. Two impedance and phase plots are included to show that box Fc was measurably reduced with the FG and, equally important, both impedance and phase variation was noticeably reduced - something amps typically benefit from.

It's all about the music

Carl

Carl's Custom Loudspeakers

Re-attaching the missing document lost during web site upgrade

LARGE_ADVENT_A34XXXX_SERIES_UPGRADE.pdf

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Here is another facet of the improvement project which may be of iterest.

Following installation of the new caps and resistors, etc. I measured the response of the tweeter at the three switch positions. The attached response chart shows exactly what happens at each switch position.

The plateau in the lower frequency range isn't ideal for this exercise because the woofer was also functioning at the time of the close miked readings of the tweeter.

It's all about the music.

Carl

Carl's Custom Loudspeakers

re-attaching the missing document

post-100237-1198682250.jpg

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Guest Kloss Groupie

Greetings.

Long time occasional lurker but first time poster.

I wanted to comment on this thread as I have a pair of NLA that I have been debating cleaning up and potentially updating with new caps. This thread has helped me decide to actually do this. So far, the only thing I have done is refoam the woofer....

I wanted to ask about the insulation you used to pack the cabinet and why you chose the pink insulation over the more common polyfill that can be found in craft stores? Is it a matter of density?

Also, how hard is it for a novice to recap the crossover?

Thank you,

Daniel

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Greetings.

Long time occasional lurker but first time poster.

I wanted to comment on this thread as I have a pair of NLA that I have been debating cleaning up and potentially updating with new caps. This thread has helped me decide to actually do this. So far, the only thing I have done is refoam the woofer....

I wanted to ask about the insulation you used to pack the cabinet and why you chose the pink insulation over the more common polyfill that can be found in craft stores? Is it a matter of density?

Also, how hard is it for a novice to recap the crossover?

Thank you,

Daniel

Stuffing studies posted here and elsewhere have shown that FG is a bit better than polyfil. If you have an aversion or, cannot obtain the OC FG, then use the polyfil. If you want to read further on stuffing do a search on the subject. Much has been posted - particularly in the AR area.

With regard to the recapping, It is not hard if you have some mechanical ablility and can use a soldering iron. REmove the woofer & stuffing and the xover will become visible. Check the caps you have for their values. They are usually in the 13-16 uF range depending on your exact vintage. Suggest you replace with Metallized polypropylene caps of reasonable cost. Boutique caps are not worth the money.

Good luck with your project.

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Guest Kloss Groupie
Stuffing studies posted here and elsewhere have shown that FG is a bit better than polyfil. If you have an aversion or, cannot obtain the OC FG, then use the polyfil. If you want to read further on stuffing do a search on the subject. Much has been posted - particularly in the AR area.

With regard to the recapping, It is not hard if you have some mechanical ablility and can use a soldering iron. REmove the woofer & stuffing and the xover will become visible. Check the caps you have for their values. They are usually in the 13-16 uF range depending on your exact vintage. Suggest you replace with Metallized polypropylene caps of reasonable cost. Boutique caps are not worth the money.

Good luck with your project.

Thank you...off to the search..

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  • 1 year later...

I've written about this before and wanted to share a similar expreience on a new speaker. Only now I've added cabinet resonance measurements which show adding a brace eliminates a noticeable 200 hz resonance. WT2 testing also shows a slight reduction in Fc with fiberglass vs the foam blocks and a nice reduction in overall Q.

Attached are 6 charts which compare the SPL response and cabinet resonance in a stock NLA with the 5 foam block stuffing to no stuffing to a braced upgrade with 1.75 lbs OCFG stuffing.

Stock NLA with 5 foam blocks Fc=43 hz, Q=1.03 Zmax=30. Min impedance meas. about 4 ohms at 7600 hz.

The cabinet resonance test was done in 3 locations using a surface applied microphone on the front baffle board at the locations denoted next. The blue line corresponds to a location between the upper left woofer bolt hole edge of frame and edge of grille strip. The red line corresponds to just above the top edge of the woofer frame (below the tweeter) and the green line = just below the bottom edge of the woofer frame. The cabinet resonance plots show a pronounced spike at 200 hz in the stock and empty cabinet tests. However, when a 5/4 by 3 1/2 inch pine brace was added internally front to back at the location just above the top edge of the woofer hole, the 200 hz spike was gone (see the last graph). Also note the significant upward shift in empty cabinet resonance test at all three test locations. This shows the effect the absence of stuffing has on overall cabinet resonances.

Empty NLA cabinet Fc= 47 hz, Q=1.14, Zmax=44.

Cabinet volume was meas. and calc. to be 1.75 cu. ft. Using my rule of thumb for OCFG, I put 1.75 lbs in the box. Fc=41.3 hz, Q=0.96, Zmax=22.3 ohms. Note the lower overall Zmax with OCFG. The WT2 tests also showed the overall phase angle swing was reduced by about 12.5%.

The 3 SPL charts show minor differences (disregard the relatively lower SPL reading on the stock NLA chart). The shape of the near field measured woofer curve changed slightly with the empty box showing a more pronounce Hi-Q hump at about 60 hz. The curve for the OCFG stuffed box was smoothed somewhat with a more gradual slope in the 50-120 hz region. These tests were run on axis @ 50 inches.

post-100237-1249003500.jpg

post-100237-1249003521.jpg

post-100237-1249003538.jpg

post-100237-1249003554.jpg

post-100237-1249003570.jpg

post-100237-1249003590.jpg

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My measurements from 2/1/09 are here:

http://www.audiokarma.org/forums/showthrea...270#post2462270

Our findings are similar with respect to overall response and effect of replacing foam damping with fiberglass.

Readers should be aware that nearfield bass measurements reflect 2-Pi alignment, essentially (but not entirely) equivalent to response with one boundary, e.g., against a wall or floorstanding....

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My measurements from 2/1/09 are here:

http://www.audiokarma.org/forums/showthrea...270#post2462270

Our findings are similar with respect to overall response and effect of replacing foam damping with fiberglass.

Readers should be aware that nearfield bass measurements reflect 2-Pi alignment, essentially (but not entirely) equivalent to response with one boundary, e.g., against a wall or floorstanding....

Hey Zilch, whatever happened to the grille cloth emporium?

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Hey Zilch, whatever happened to the grille cloth emporium?

Still here; we only sell one kind of grille cloth -- OEM JBL Monitor Blue.

And the Biradial Babes still pour a selection of fine wines in the spa, by appointment.... ;)

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  • 3 years later...

>Hi I was reading your post with interest in replacing the

>foam in my advents. I have a question though. Is there an

>alternative way to figure how much fiberglass to use. Like

>R-factor or inches thick. Sorry but I don't have a scale to

>accurately weigh 2.1 pounds and am hoping you could help.

>

>Thanks Larry

AS PROMISED........

The following is based on a single sample test, so don't take it as gospel.

I took a roll of standard OC R-13 fiberglass batting and cut 3 ft off it, peeled off the paper backing as best I could and weighed it. It weighed 9.7 ounces. The batting is 15 inches wide and 3 inches thick.

Therefore, to obtain 2.1 lbs you must cut off about 10 ft. and 5 inches from a similar roll.

For future reference, the weight rate is 3.2 lbs per liner foot of R-13 OC insulation or, conversely, it's 4 ft, 11.5 inches/lb. Box stuffing is not an exact science so you could use 5 ft/ lb.

After seeing this thread recently I replaced the insulation from foam to fiberglass in a pair of large Advents and was really impressed with the results. I also have a pair of Advent Heritage speakers that I would like to replace the foam with fiberglass insulation.

Do you know how many lbs. or feet of 3" R13 insulation I'd need?

Thanks.

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Holy cow! Over 11,000 views.

Calculate the approximate internal volume of the Heritage cabinet and use 1 lb/cu. ft of stuffing. I'm not sure what the volume is.

Thanks. Finished the project yesterday. The Heritage speakers already had some fiberglass insulation instead of foam rubber. There were three 3" x 12" x 38" bats inside.

Fantastic, low cost upgrade. After stumbling upon this thread I converted three pairs of large Advents from foam to fiberglass insulation along with the Heritage pair. I could really hear the difference and it's been quite the eye opener to re-experience some of my favorite albums.

IMG_0702_zps1effb73e.jpg

IMG_0711_zpse278d514.jpg

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