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Thread: Building my dream system, need lots of advise!

  1. #46
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by jmpsmash View Post
    my room is 20ft wide. right now on the side walls there is a 2x4" diffusion panel on first reflection each side. it was there for my previous pair of regular dome speaker. let me make it 4x4 and see if that makes a difference.
    My room was about 30’ by 25’... 10’ high heavy velvet curtains with a lot of “fullness” helped a lot.


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  2. #47
    Member jmpsmash's Avatar
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    I was doing a bit of research on the 2216ND-1. the speaker that it was used in is the 4367. There is a nice a detailed review on it.

    https://hometheaterhifi.com/reviews/...peaker-review/

    the exterior speaker size is ~37x26x16.75. taking off 1" panel thickness and a bit more for the front baffle and that lip for the horn. I assume gross internal volume to be 5.5 cu ft or maybe slightly less. Not sure how much more to remove to account for the horn, woofer and bracing, probably another 1 cuft? so it will be down to 4.5 cu ft.

    What I like about it is that it is wide and thin. The goal is to mount the 2216ND-1 as close as reasonable so if the cabinet is less than 17", the 2441 can dangle (supported) behind the back of the box.

    There is also a nice internal diagram in the above article.

  3. #48
    Member jmpsmash's Avatar
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    alternative is to design it to be more acoustic ratio like, but the 2441 will either make the 2397 further away than the 2216ND, or I will have to put in a hole for the 2441 to sit in.

    I plan to mount the 2216ND as high as possible within aesthetic constraints.

  4. #49
    Member jmpsmash's Avatar
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    I am trying to arrive at a alignment and thus box / port size for the 2216ND-1.

    in a previous thread, @zeljkor measured a pair of 2216ND-1 to have:

    T/S data measured from the first driver:
    Re = 5.556Ohm
    Fs = 28.26Hz
    Qts = 0.376
    Qes = 0.397
    Qms = 7.12
    Le = 0.461mH
    Mms=134.1gr
    Vas = 332.8liters

    T/S data measured from the second driver:
    Re = 5.52Ohm
    Fs = 27.59Hz
    Qts = 0.3572
    Qes = 0.3776
    Qms = 6.589
    Le = 0.4703mH
    Mms=123.8gr
    Vas = 378.4liters


    they differ a little as one is warmed.

    I tried plugging into WinISD for a few different standard alignments.

    SBB4 : 7.443 ft^3, tuned to 28.26Hz, F3=33.8, GD@40Hz=9.6ms, GD@30Hz=15.25ms
    SC4: 8.869 ft^3, tuned to 29.48Hz, F3=30.5, GD@40Hz=10.6ms, GD@30Hz=18.5ms
    QB3: 9.017 ft^3, tuned to 29.62Hz, F3=30.5,
    GD@40Hz=10.8ms, GD@30Hz=18.6ms

    Those are pretty big boxes, but their FR is pretty flat with no hump. And supposedly they are the alignments with tighter bass.

    QBB4 seems to be the most practical in terms of size.

    What I still trying to understand is...

    The 4367 cabinet is way smaller than the QBB4. I estimated it to be less than 5 ft^3. Is there something JBL knows? or is it just a marketing decision to go with a smaller box as a compromise?

    SBB4 traded off 3Hz for a few seconds GD. I know 3Hz is probably audible, how about a few mseconds in GD?

    There are also some stuffing in the 4367 cabinet. Is that something worth considering ? supposedly in closed box, it "adds" 10% effective volume.

    What would be the sound quality difference if I go with a even smaller boxes? I know GD will go up which means slower and less tight bass?

    How is everyone seem to be happy with just 5 ft^3?

    I want to make sure the bass is tight good quality. If there is small sacrifice in F3, I can EQ it back. But how about a few ms in GD?


  5. #50
    Senior Member grumpy's Avatar
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    I think the answers may lie between room gain and banana curve discussions.

  6. #51
    Member jmpsmash's Avatar
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    Quote Originally Posted by grumpy View Post
    I think the answers may lie between room gain and banana curve discussions.
    please explain...

  7. #52
    Senior Member Ian Mackenzie's Avatar
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    In the diy space you have freedom to select your own enclosure alignment.

    There are no cost, aesthetic or marketing constraints.

    A properly tuned bass reflex enclose will only differ in bass extension and physically in enclosure size.

    Generally the acceptance of a given box size is the controlling variable. You have to make that decision.

    Once that is decided you can then manipulate the box tuning frequency to suit a preferred location in the room.

    With the enclosure placed well away from a floor wall boundary intersection there is minimal boundary effect.

    Moving the enclosure closer to the floor wall intersection will create a more pronounced bass response. Moving the enclosure closer to the corner of the room will further increase the bass output. The effect of the boundary placement needs to be assessed in a particular room for a particular loudspeaker.

    The effect of a shift in the tuning frequency of 30 hertz over a small range (28-34 hertz) has a pronounced effect on the output of the system. This is because the woofer output tapers off significantly with frequency as the system approaches the tuning frequency. As this occurs the port output increases to a maximum at the box tuning frequency and then tapers off quickly below the tuning frequency.

    As the tuning frequency is increased the bass output becomes more aggressive but the lower frequencies will diminish. A lower tuning frequency will produce a less aggressive bass output and will sound more damped.

    With this in mind a skilled loudspeaker engineer can work with the box size and enclosure tuning so that as the enclosure is moved closer to the wall floor intersection the bass response output increases progressively at lower frequencies without becoming overly boomy in the mid to upper bass region. This is often an empirical process involving experimentation and listening tests.

    Putting this another way a loudspeaker with a maximally flat enclosure alignment may look good on paper but may prove tricky when attempting to obtain a smooth extended bass response with the enclosure near a wall floor intersection.

    This is because the mid bass frequencies will tend to dominate and appear louder than other bass frequencies due to a hump in the bass output with the enclosure placement near the wall. The bass quality can be sensitive to small changes in the distance of the enclosure from the rear wall. The user may then need to raise the enclosure off the floor to obtain the most satisfying bass response.

    In comparison a sealed loudspeaker bass response will roll off at a higher frequency than a bass reflex loudspeaker but the rate or slope of the bass roll off is more gradual than a bass reflex design. Hence bass reflex designs have a reputation for being boom boxes in small rooms that don’t allow freedom of room placement.

    Not every loudspeaker has a bass response that is going work in every room.

    I therefore suggest you mock up an unfinished enclosure with a false back and try out some different enclosure volume and tuning options. Then experiment with room placement. You will more than likely prefer the bass of one enclosure and tuning over another in a particular room placement.

  8. #53
    Senior Member Ian Mackenzie's Avatar
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    Another approach is to pick the minimum acceptable enclosure size for the driver and tune the system in accordance with a maximally flat alignment.

    Then apply low frequency EQ using either a graphic equaliser or dsp equalisation if extension of the bass response is desired. This is a more straightforward approach than a customised tuning.

    Generally a bass reflex enclosure has maximum power handling at the enclosure tuning frequency. Below that frequency the system is unloaded. You may therefore be able to modify the system low frequency response within reason. But be aware there are limits that need to be observed if overloading system the system is to be avoided. Moderation is important in how much EQ you apply as power dissipation and voice coil displacement must not be exceeded. A 3rd order high pass filter just below the tuning frequency is recommended if the system requires +6 dB of bass boost at the system tuning frequency.

    If the bass response is dominant over other frequencies equalisation can be applied to reduce this effect.

    Be aware that “cut” is preferred over boost in taming room related bass response problems. There are several reasons for this. Below 290 hertz room modes and other effects dominate the response in the form of peaks and dips. Attempting to boost a dip in the response may require significant equalisation and cause damage to the woofer. Dirac and other dsp based EQ is useful for cleaning up problems when flexibility in enclosure room placement does not exist. However not everyone likes the idea of converting an analogue source to dsp and then back to analogue. Analogue parametric equalisation is another option but can be expensive. The choice is yours.

    Generally equalisation and adjustment to enclosure placement works most effectively when used together.

    You can also consider room treatments. However such treatment is both expensive and bulky to be effective at bass frequencies. Also bad for WAF factor.

    This is not an in depth discussion on the subject of loudspeaker and room equalisation but points to some of the key issues and choices available.

    There is no benefit in aiming for perfection unless you are prepared to experiment with some ideas on a practical level before committing to a final design.

  9. #54
    Member jmpsmash's Avatar
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    Ian,

    Thanks for the lengthy reply!

    I like the idea of having a adjustable enclosure. I don't mind having a larger enclosure, I just want to have the best sounding one. So far I have only read about all these alignment and tunings on books and from forums and articles online. Even though I believe in theory, I also believe in hands on experimentation. Having such an enclosure will allow actual listening, experimentation and measurement.

    My rough plan is to have a front baffle internal area of 18.5" wide x 30" tall. Adding 1 cu ft will be ~3 inches deep difference which is quite OK!

    Wood will be cut this weekend.

  10. #55
    Senior Member Ian Mackenzie's Avatar
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    Its entirely up to you what you end up doing.

    However, with the 2397 as wide as it is (660mm or 26 inches wide ) I would shoot for an enclosure of that width.
    http://www.jblpro.com/pub/obsolete/2397.pdf

    That will give you more volume if you decide to go for a 7 cu ft enclosure.
    Assuming your 30 inch (76cm) internal enclosure height then a 5 cuft3 enclosure will have internal depth of 11 inches and a 7 cuft3 will have an internal depth of 15 1/2 inches.

    Remember a larger enclosure buys you a more extended bass response.

    You can buy that bass extension in a smaller enclosure with these woofers by adding some EQ if required. Greg says you can hit the 2216nd with 8-10 db in a 25-27 hertz tuning in a 130 Lt enclosure.. This type of enclosure tuning delivers deep extended bass in a somewhat smaller enclosure. The trade off is amplifier power and lots off it. (reference to the JBL M2) As the voice coil heats up the DC resistance drops (due to the negative coefficient of the wire) and they punch hard. The 2216nd-1 cone has an acquaplas coating to lower the Fs a bit. Its otherwise a 2216nd driver.

    As I said earlier when you EQ the system with your Mini dip you might find the EQ shaves back the bass response if you place the larger enclosures within 20 inches of a wall. Therefore the larger enclosure volume is wasted space. This is in part what JBL have opted for what appears a smaller enclosure than your diy box simulator suggests. The marketing department also knows sales will plummet with large enclosures (over 6 cuft3 net internal volume).

    Once the room environment is introduced what you hear in the bass is the room influence not the best sounding enclosure tuning per say.
    Your Minidsp EQ will clean up the bass.

    I use a Nad C658 streaming preamp in a family room with a floor standing loudspeaker up against bookcases along the rear wall and the inbuilt Dirac EQ really improves the bass clarity.

    By all means try a larger box of that is your desire but be careful what you wish for.

    I hope this makes sense.

    In the end you must decide what your going to do.

  11. #56
    Senior Member Ian Mackenzie's Avatar
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    Its entirely up to you what you end up doing.

    However, with the 2397 as wide as it is (660mm or 26 inches wide ) I would shoot for an external enclosure what wide.
    http://www.jblpro.com/pub/obsolete/2397.pdf

    That will give you more volume if you decide to go for a 7 cu ft enclosure.
    Assuming your 30 inch (76cm) internal enclosure height then a 5 cuft3 enclosure will have internal depth of 11 inches and a 7 cuft3 will have an internal depth of 15 1/2 inches.

    Remember a larger enclosure buys you a more extended bass response.

    You can buy that bass extension in a smaller enclosure with these woofers by adding some EQ if required. Greg says you can hit the 2216nd with 8-10 db in a 25-27 hertz tuning in a 130 Lt enclosure.. This type of enclosure tuning delivers deep extended bass in a somewhat smaller enclosure. The trade off is amplifier power and lots off it. (reference to the JBL M2) As the voice coil heats up the DC resistance drops (due to the negative coefficient of the wire) and they punch hard. The 2216nd-1 has an acquaplas coating to lower the Fs a bit. Its otherwise a 2216nd driver.

    As I said earlier when you EQ the system with your Minidsp you might find the EQ shaves back the bass response if you place the larger enclosures within 20 inches of a wall. Therefore the larger enclosure volume is wasted space. This is in part what JBL have opted for what appears a smaller enclosure than your diy box simulator suggests. The marketing department also knows sales will plummet with large enclosures (over 6 cuft3 net internal volume).

    Once the room environment is introduced what you hear in the bass is the room influence not the best sounding enclosure tuning per say.
    Your Minidsp EQ will clean up the bass.

    I use a Nad C658 streaming preamp in a family room with a floor standing loudspeaker up against bookcases along the rear wall and the inbuilt Dirac EQ really improves the bass clarity.

    By all means try a larger box of that is your desire but be careful what you wish for.

    I hope this makes sense.

    In the end you must decide what your going to do.

    Edit. The Mms=134.1gr data you posted might not be accurate as the acquaplas coating adds mass to the cone (2216nd is 135gr).

  12. #57
    Member jmpsmash's Avatar
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    Again thanks for the very detailed explanation.

    I plan to have the speakers around 5-6 ft off the front wall and 7-8 feet apart. That's where they (2397/2441 + T825A) are right now and they sound pretty good with a deep sound stage. I don't expect to move them that far into the front wall. I have a few things in mind:

    having a 60cm baffle will push the baffle step cutoff down to 200Hz. I probably won't end up using the 2123H but would be nice for them to coincide with the 2123H low cutoff in case I do. I also not too sure about the look of a wider baffle honestly.

    I have also in the back of my mind that, further in the future, probably some time next year, after I have figured out the crossover points, to build a passive crossover for the whole system. Why? Well to learn and gain some knowledge, and also to use a 300B amp that I have build but not utilized at the moment. I know it won't give the type of bass that my current amps will give, but something about claiming to have listened to something that I built by myself is very attractive. Also I am longing for the seductive sound of a class A SET plus horns.

  13. #58
    Member jmpsmash's Avatar
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    This is what I have so far. Still need to work on the bracing.

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  14. #59
    Senior Member Ian Mackenzie's Avatar
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    Your right it will image better out from the wall.

    If you want to get fussy there are some interesting baffle diffraction modelling programs that predict the midrange response of the driver position on the baffle. Offsetting the driver a bit can smooth the response.

    None of this matters if you use the Minidsp EQ but if you plan to use the SET solo it’s something you might consider.

    If you do eventually try the SET amp my suggestion is Biamp with a high quality analogue active crossover so the SET is running the horn and the Fostex. You’ll get tight bass and that midrange you prefer. The mini dsp is a nice entry into active loudspeakers but not Hi end HiFi. Pm me when you want to explore analogue active crossovers.

    My suggestion is to invest in the Dayton loudspeaker tester if you are serious about tuning your enclosures with actual TL data from your drivers.

    https://www.parts-express.com/dayton...ystem--390-807

    Good luck with your project.😀

  15. #60
    Member jmpsmash's Avatar
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    A pair of this showed up in the mail today.

    I need that DATS but they don't sell the old one anymore and the new one isn't released yet!

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