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Diy 2x15 cabinet build (the real deal)

Discussion in 'Amps and Cabs [BG]' started by BogeyBass, Mar 9, 2013.

  1. Black and Silver

    106 vote(s)
  2. Red and Tan

    49 vote(s)
  3. Something Else like Carrots

    41 vote(s)
  1. BogeyBass


    Sep 14, 2010
    Yep finally got to it, building a serious 2x15 unlike my last thread which was for fun and a little experimentation.

    So I have a extra pair of 3015's laying around, so decided to build a 2x15 for these drivers. The total volume and tuning would also be suited also for many other 15" drivers.



    There will be a cavity for each driver to minimize
    distortion, and dedicated ports for each.

    The design also includes symmetrical ports. The driver is centered to the enclosure. So any pressure leaving the rear of the cone will arrive at surrounding wall/corners at approximately the same time. Likewise with all port exits, all of them are symmetrical to the driver. The placement within the cavity of the ports is also spaced the same for all 4 ports.
    The combination of symmetrical ports and centered drivers within the cavity will promote all pressures to react the same and minimize offset distortions

    Typical baffle offset of drivers and offset or non symmetrical placement of ports is not being used which is common for most loudspeaker design. Symmetrical ports are being used to minimize cone distortion. And symmetrical driver location is being used so all pressures entering the cavity, and leaving the ports will react to the cavity in the same manner.
    Again also symmetrical ports to reduce distortion from cone pressure and port pressure when they combine to create the end waveform being produced. Viewed in models of port pressures with cone pressure, non symmetrical port location can create waveform distortion within frequency when port is not fully resonating at resonate frequency. But the port is still beginning to release pressure beginning when cone movement starts to reduce and ports are producing in phase or out of phase pressure from previous half cycle of the waveform. Depends on frequency Fb of reflex cabinet and current symmetry of waveform. Modeling port behavior with a symmetrical waveform without harmonic partials such as a sinewave. Will simply not show the complexity and distortions created by a reflex type transfer function. Again trying to equalize internal pressures and exiting port pressures will reduce distortion created by non symmetrical waveforms.

    when negative pressure and positive pressure meet distortion of the waveform occurs and can also create standing waves and more distortion within the port. Again with non symmetrical or harmonic waveforms each half cycle of the waveform is not equal and is more likely for standing waves and distortion to be created within the port. Since each half cycle of the waveform is not equal being non symmetrical, resonance does not occur evenly distortion will be created. The reflex or ported cabinet relies on a positive pressure to move forward from the cone, which in turn fills the enclosure cavity behind the speaker with a negative pressure, this completes on half of the sine wave waveform. Then when it reverses to finish the other half of the waveform. The negative pressure is now leaving the cone and a positive pressure is being produced behind the speaker in the cavity. Since the negative and positive pressures do not combine, the now positive pressure being created inside the cabinet will push out the negative pressure that just filled the cavity from the previous half cycle. This negative pressure will now be pushed out of the ports to combine with the current negative pressure leaving the cone. This is why very little cone movement at resonance occurs since you now have a speaker trying to create a negative or positive pressure within the enclosure, but it is pushing against a pressure of equal force of the opposite polarity. Pretty much reducing the ability of the cone to create a waveform and simply relieving the pressure out of the only place it can escape the port.

    So say a longer half cycle of say negative pressure has now filled the cavity, and will continue to fill the ports and possible start to exit the ports to meet the positive waveform now leaving the cone. or will also create standing waves within the tube since the negative pressure is colliding with positive pressure now being pushed out of the ports to combine with the current positive pressure leaving the cone. Remember the only amount of available pressure is from the previous half cycle. So if the other have cycle is larger or smaller, the smaller waveform will leave more of the opposite pressure inside the cavity,or a larger waveform will push out all the previous pressure and start to leak out. And then again since more pressure was introduced gives the likely hood that the next cycle might not be large enough to relieve the now extra pressure being produced. It does not magically disappear the pressure goes somewhere, which is distortion, either outside the enclosure as distortion to the waveform, inside the enclosure where it produces standing waves, or inside the port itself where it produces standing waves.

    reduction of the distortion i see happening a few ways, increase the length of the port, so when extra pressure is produced more likely standing waves are produced inside the port instead of pressure exiting and causing distortion at the cone. Also the port could include dampening material at the beginning or end of the port, which will actually turn the extra pressure not occurring from resonance into heat instead of audible pressure waves. similar in practice to transmission lines where the line is stuffed to reduce distortion. So when resonance occurs the port will perform as designed, but when standing waves or out of phase pressure is being introduced to the port the damping material is their to help get rid of it.

    Or simple by centering the driver within the enclosure and promoting equal pressure within the enclosure and using multiple ports of longer length which are also symmetrical to the driver. Standing waves are more likely to distributed and dissipated by being evenly divided to multiply long ports before exiting and effecting the cone , instead of just one short port being pounded with standing waves and dissipating pressure. and due to the short length more likely for more out of phase material to exit, and also creating standing waves which would promote any new resonate cycles to be distorted, since the port volume is now being occupied by standing waves and cannot resonate to calculated length.

    pressure leaving a port at a farther distance from the source, the speaker cone, can produce distortion of the waveform since the port can conduct before the waveform is starting to be produced. So the cone pressure will collide with the port pressure since the port pressure has left first, depends on frequency and symmetry of waveform being produced, also the opposite can happen cone pressure will leave first then port pressure will leave after. Essentially pushing against the developing wave instead of the wave colliding with a already existing pressure as before. From a single offset port source this pushing or colliding will be more intense and cause more distortion to one side of the waveform since all the pressure is being created at a certain velocity in a certain location.

    By using multiple longer lower velocity ports placed closer to speaker cone and in a symmetrical locations , it is more likely for the pressures to combine earlier and evenly and create less distortion. also due to the extra length of all the ports combined and extra port area, port pressure is being released more slower over multiple smaller openings placed closer to the source over the period of the half cycle of the waveform. Not all at once in a centralized area again reducing distortion and allowing the 2 pressures to combine smoothly and be produced from the same source being the speaker cone.
    Very similar practice to keeping 2 drivers as close as possible so they react as a single source, likewise keeping speaker cone and port openings as close together as possible so they react as a single source. trying to mend the port and speaker as one unit, since you cant really put a port in the middle of the speaker cone, simple just mount it as close as you can. possible even shape the exit to the shape of the cone itself.
    Maybe those old round port openings directly around the driver on the old fender tone ring speakers were on to something.


    Above image is for response of single driver

    Volume chosen was for good power handling and decent bass response. Each cavity is 3.2 Ft3 (90 L) for a total of 6.4 Ft3 (180 L). No specific alignment is being used, practice for Fb is very similar to a BB4 alignment where cabinet tuning is set at resonant frequency of the driver which is 45 hz for the 3015. Required volume for a actual BB4 is around 2.8 Ft3 (79 L) decided to use a larger volume for more bass response at 3.2/90L which is closer to a SC4 alignment.
    But still using a lower BB4 tuning frequency (Fb) of 45hz to match driver resonant frequency.
    Actual real world Fb im hoping will fall slightly lower around 43/44 hz.


    Power handling is roughly 300 watts per driver below 100hz for
    a total of 600watts with 2 drivers. Above 100hz the driver can be driven to its 450watt thermal limit without distortion for a total of 900watts

    External dimensions are 24"wide 38" high 16" deep
    again i have based the front dimensions according to the
    Golden Ratio 1.618. The ratio has been used for many years by famous architects and artists to produce a object that is aesthetically pleasing. Also the dimensions are very similar to a Sunn 200s and will also include a false front edge like the 200s to make the side walls look beefy. And will also use a pretty cloth grill like all classic cabinets should have. The sunn 200s is approximately 1inch higher than what the golden ratio would give you to the width of 24", Golden Ratio for 24" wide would be 38 53/64 ". I decided to round it off to a nice 38" dont need to twist my head on the table saw with a bunch of fractions to calculate. Biggest downfall i would say to the measurement system that i grew up on and was taught. Freakin fractions ....blah
  2. BogeyBass


    Sep 14, 2010
    The beginning, well could not get everything to lay out on one sheet. But it does work on 2 sheets, and with a smart layout I figured out a way to get 2 cabinets out of 2 sheets. Weird huh? one wont fit on one sheet but 2 will fit on 2 sheets.


    Decided to start with front baffle and port assembly. ports will be built in a similar manner of my last build

    just measure half the circle drive a nail into center spot and rotate around on router table cutout for 3015 is a real easy 14"



    cutouts all done

  3. Looking interesting, Bogey, what will you be using for amplification?
  4. Jordan S.

    Jordan S.

    Mar 25, 2012
    NSW, Australia
    Blacksheep Effects Pedals
    Sub'd. I love a good build.
  5. BogeyBass


    Sep 14, 2010

    I'll be using one of the usual dinosaurs;)
    they cab and grill will be wrapped to match the 200s

    but coming soon to a theater near you will be my
    amp build thread..to match woo hoo, quad of 6550's with a simple tone stack. Hopefully enough juice to get 150/180watts
  6. outstanding :cool: Sub'd.

    BTW, finished one of two 1-15s to house my JBL D-140Fs based on your advice from last year, turned out very nice, thank you :D Can't wait to have the other one done as gig season has begun :bassist:
  7. BogeyBass


    Sep 14, 2010
    cool cool thanks for stopping by.

    Started the ports last night too. to tired to post what i had.

    at the front of the port i attach a small 4"x4" piece of wood. this will attach to the back of the baffle. then i use a trim bit to cut open the hole. Then do a slight round over to the port opening.

    Here is the stack of 4x4 pieces you can see their position in the drawing at the beginning of the thread on the back of the baffle. also is the 1" pieces for the false front and a few of the 2" braces to be used.


    just simply use a 3.5" hole saw for the outer dimension of the pipe. inner dimension is 3" for a total of 4 x 3" round ports.


    now i get to steal old pictures from my first thread to show a cutaway. I used wood glue at first to attach the pipe to the wood bezel this time im using a high strength epoxy.


    I could simply use 2 x4" round ports, but using 4 x3" round ports for the symmetrical design will actually yield a lower velocity as well. I would love to achieve 15 to 20ms at full power. But it is what it is 25 to 26ms is better than 30ms and at 300watts the power limit below 100hz velocity is around 20/21ms. Just like i wanted

  8. will33


    May 22, 2006
    Be following this one Bogey. Nice work and well thought out design, as usual.

    Some of you folks interested in DIY really should follow this, paying attention to the decisions made and why this guy does the things he does.

    Now...about this 4 x 6550 deal.:D That's in a real sweet spot. I still haven't tubed up my Classic400 but have been contemplating only loading it with 4. Would move my output taps to 8 and 16 but be in a really nice power spot for my non-arena gigs....which is all of them.:)
  9. BogeyBass


    Sep 14, 2010
    I knew i should not have mentioned that amp little distraction i guess all good though.

    just cant find a amp worth a #### that i would like to buy.
    so gonna do it myself to get what i want.

    mainly just a 4 x6550 that actually has a 2ohm tap, and switchable between ultra linear or non. ultra raises the overhead slightly nice for clean tones. but driven into overdrive UL does not have the same tone. so i want it switchable.

    no bs effects loops or fancy EQ's just simple and straight forward plug straight in and get the tone. and with a 2ohm tap actually able to run 4x15......;)
  10. astack


    Nov 12, 2011
    St. Louis, MO
    Subbed! Loved the last build thread and always good info from BB.
  11. mc_muench


    Sep 28, 2010
    Milwaukee, WI
    subb'd this is going to be one cool cab!

    Love those heads!
  12. Sub'd
  13. BogeyBass


    Sep 14, 2010
    Hey cool again guys, tanks fur stop'en by

    So finished the wood bezels that i attach to the port tube and then use to attach to the baffle. like i said used epoxy and then give them a good sand so they fit nice and flush


    and then stick em to the baffle with a few guide lines and lots of glue and a few tacks to hold them in place for the glue to set.
    you can also see 8 braces that attach to the port bezel and then will connect to the rear baffle. So im not using dowels for bracing but it is very similar to the method.

  14. BogeyBass


    Sep 14, 2010
    so this is the front and i have drilled some pilot holes so I can enter the router trim bit.


    trim away with a bearing to follow the port tube



    trim again with round over to add flare


  15. BogeyBass


    Sep 14, 2010
    time to attach side panels, false front strip has already been added
    makes a great guide and extra area for glue.

    that is it for today, gonna take my sweet pea to the movies and dinner...;)

  16. will33


    May 22, 2006
    Really dig the bracing scheme. Taking advantage of the bezel edges for more glue area and the flat sides allow you to tie together any cross pieces further down the line.

    Nice touch on the flares as well. Smart stuff there...allows you to use pipe stock by the foot instead of fancy, overpriced pieces of plastic labeled "flared ports"....cool.
  17. astack


    Nov 12, 2011
    St. Louis, MO
    I'm looking at the inside face of a side here, yeah? And the face of the baffle butts up to the back side of that ~1" strip? If so, makes a lot of sense for more surface area like Will said, but also just to align it easily and not worry about the baffle ending up angled to the front of the cab (not that I've ever had that happen :bag: ).
  18. BogeyBass


    Sep 14, 2010
    yeah its what i was hoping for. With 8 ports was thinking the cost would be a little higher. so far exactly 21 bucks for one 10 ft section of pipe. All the other parts and bracing is made from the extra pieces of drop from cutting out the main pieces.

    yep got it right that is the inside face, so far building it in my head. i will attach the front/back baffle and 2 sides. and the top and bottom pieces are left for last. So i can have access to the cavity and install all the further braces and add the damping material. then the last step will be to seal it up.
  19. astack


    Nov 12, 2011
    St. Louis, MO

    What kind of ply? Thickness, # plies, species? Your followers need to know man!
  20. Passinwind

    Passinwind I know nothing. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Here are some interesting ideas on how to do the inside flare too.

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