Tall and narrow 9' cab for 2269

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Originally Posted by gasfan

What would/could the consequence be? The driver on the 22" side 10" up from the bottom, the ports up top.

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I see no problem with raising the 2269 off the floor but I would go higher than 10”.

I don’t see a successful cabinet with a depth of less than 18” (drop the height to 46).

You’ll have to account for the size of the ports on the baffle as I believe that you’ll need 3 ports. With 2 ports (4”) the tube length will be too short to be usable.

You’ll have to use ports with both ends flared as the 2269 moves a lot of air.

With flared ports the cutout is much larger than the tube diameter. My cabinets used 4” Precision Ports the cutout for this size of port is 6.25”. This allows the inner flare to go through the front of the baffle – very convenient.

As you can see on the baffle only two ports fit in one horizontal line, but there is no issue mounting 2 below and one above.

I also think using ports less than 4” will generate port turbulence noise, the SUB18 is approx. 5”.

Pay attention to all the suggested reading from RMC and Robh3606. I like the 1983 article as it has very efficient bracing suggestions – no need to go crazy with CNC cool looking bracing unless you want to.

Just my thoughts on the matter YMMV…

Also, I’m LMAO with you thinking a 2269 sub-woofer can be unobtrusive!

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Originally Posted by christo

I see no problem with raising the 2269 off the floor but I would go higher than 10”. I don’t see a successful cabinet with a depth of less than 18” (drop the height to 46). You’ll have to account for the size of the ports on the baffle as I believe that you’ll need 3 ports. With 2 ports (4”) the tube length will be too short to be usable. You’ll have to use ports with both ends flared as the 2269 moves a lot of air. With flared ports the cutout is much larger than the tube diameter. My cabinets used 4” Precision Ports the cutout for this size of port is 6.25”. This allows the inner flare to go through the front of the baffle – very convenient. As you can see on the baffle only two ports fit in one horizontal line, but there is no issue mounting 2 below and one above. I also think using ports less than 4” will generate port turbulence noise, the SUB18 is approx. 5”. Pay attention to all the suggested reading from RMC and Robh3606. I like the 1983 article as it has very efficient bracing suggestions – no need to go crazy with CNC cool looking bracing unless you want to. Just my thoughts on the matter YMMV… Also, I’m LMAO with you thinking a 2269 sub-woofer can be unobtrusive!

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Those dimensions fit neatly behind my Acoustats. :)

Hello gasfan;

Since the modal calculation rules of acoustics applies to all spaces large and small we find what plaques us in small rooms benefits us in low frequency enclosures. Where the length of frequencies in subwoofer enclosures are almost always longer than the enclosures internal dimension we can often get away with murder, so to speak. We can build cubes with no negative consequences.

Where the oft quoted golden ratio or other acoustic ratios are applied we find even distribution of modes ie the golden ratio divides standing waves on 2/3 octave intervals. Another often used enclosure ratio is 0.7937 X 1 X 1.2559 divides standing waves at 1/3 octave intervals and these ratios avoid mode stacking as well.

The math on your enclosure with the longest dimension of 57” dictates the enclosures first standing wave mode will be about 118Hz. That is likely outside of the passband of most subwoofers and while there will still be some energy at 118Hz with a say an 80 Hz crossover, with the high aspect ratio of your proposed enclosure there will not be another mode anywhere close. Everything below 118Hz will be pressure modulation only.

As has been stated, be sure the motor has adequate venting distance to the back of the enclosure.

I say build it and brace well.
Barry.

You need to like the box shape and its fit in your home, something you can live with under different circumstances since lifestyle changes over time.

Golden ratio cabinet typically leads to what some call a shoebox type cab, e.g. 5 cu.ft. = 33.2 X 20.52 X 12.68"

As for the Acoustic ratio the box usually isn't as tall, but deeper type, e.g. 5 cu. ft. = 25.85 X 20.52 X 16.29", this assumes woofer assigned to baffle in the same manner as above.

Another cab building rule. Even though one has respected a proper box ratio (Golden, Acoustic, etc), therefore shouldn't have to bother further about this, there's yet more to reinforce the prevention of standing waves in the cab: woofer placement off-center vertically and/or horizontally!

JBL 1983 2245H original article, extract page 5, picture. There's another pic about this i'll post it tomorrow. Gotta go now.

Richard

A PICTURE IS WORTH A THOUSAND WORDS... Might be the best one i saw yet to show this specific aspect.

Installing a woofer exactly in the center of the baffle may look better to some but it promotes standing waves inside the box.

This is a picture from the speaker building material of former British manufacturer McKenzie Acoustics (integrated into Fane Acoustics if i remember well). Its a generic box drawing, no proprietary info given, simply to illustrate what is referred to in the phrase under the sketch. That phrase is what matters about where to put the woofer.

Although the numerous box dimensions in the document (not shown here) are in the Golden ratio as indicated, McKenzie engineers still recommended asymmetrical woofer placement on the baffle. Again to minimize standing waves in cab. So here, a proper box ratio + off-center driver = the belt and the suspenders.

In a subwoofer cab its often easier to locate the woofer off-center since there's usually no other driver sharing the baffle space, contrary to a multi-way system.

I try to take best practice from each manufacturer i come across. You can increase the pic's size at will its clear. Please don't repost it on other web site(s).

Richard

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Originally Posted by christo

I see no problem with raising the 2269 off the floor but I would go higher than 10”. I don’t see a successful cabinet with a depth of less than 18” (drop the height to 46). You’ll have to account for the size of the ports on the baffle as I believe that you’ll need 3 ports. With 2 ports (4”) the tube length will be too short to be usable. You’ll have to use ports with both ends flared as the 2269 moves a lot of air. With flared ports the cutout is much larger than the tube diameter. My cabinets used 4” Precision Ports the cutout for this size of port is 6.25”. This allows the inner flare to go through the front of the baffle – very convenient. As you can see on the baffle only two ports fit in one horizontal line, but there is no issue mounting 2 below and one above. I also think using ports less than 4” will generate port turbulence noise, the SUB18 is approx. 5”. Pay attention to all the suggested reading from RMC and Robh3606. I like the 1983 article as it has very efficient bracing suggestions – no need to go crazy with CNC cool looking bracing unless you want to. Just my thoughts on the matter YMMV… Also, I’m LMAO with you thinking a 2269 sub-woofer can be unobtrusive!

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Thanks, I appreciate your input and advice. I can tweak the width to 23". Mind you these dimensions are internal. I accommodated 1.5" baltic birch thickness so 9.10 cu. ft. gross. Why do you see no success with a depth less than 18"?

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Originally Posted by gasfan

Thanks, I appreciate your input and advice. I can tweak the width to 23". Mind you these dimensions are internal. I accommodated 1.5" baltic birch thickness so 9.10 cu. ft. gross. Why do you see no success with a depth less than 18"?

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I’m not an engineer of any sort so my thoughts are purely from an amateur speaker builder
1. See Widget’s post #9
2. Look at of all of the JBL Pro cabinets that use a 2269 on average all have an approximate a depth of 30 inches
3. You have to allow the free flow of air within the cabinet to hook up with the port, the speaker, cabinet and port are a connected system. By having the back of the 2269 against the wall I believe you going to restrict the speaker’s ability to move air properly (i.e. connect with the port).

When I tuned the ports on my 4345s at 29 Hz I listened to them for a few days something did not sound or feel right. I went back and inserted another port tube length (I had pre-cut 3 different lengths) and then things sounded / worked better. The only way I can describe it is the 2245/Cabinet seemed to be able breath better the bass was more free sounding - sounds crazy but that was my impression. My point is I changed something in the system and it worked better.

I don't think you need a cabinet thickness of 1.5 inches. If you use 1" Baltic birch with adequate bracing you'll be fine. I use 1” x 3” Baltic birch for all bracing and never had a problem. I use the bracing technique outlined and page 62 in the 1983 article New Lows in Home-Built Sub-woofers to tie the sides, top and bottom together, it’s simple and works. Remember to tie the front and back baffles together with bracing, with a 2269 I’d use 2 braces back to front above and below the driver.