Celestion F12-X200 And Thiele Cabinet Design

  • I am going to build a pair of FRFR cabinets and load them with the Celestion F12-X200's.

    -- I am going to follow the Celestion Cabinet Design for this.

    -- Yes I am aware of the Kemper Kone.

    -- Yes I am aware that Zilla Cabs will build me one, but I am a hobbyist wood worker and want to do it myself.

    -- I am doing this simply to see how my Profiler will sound in a true FRFR Thiele environment, I.e. removing

    all of the speaker and cabinet coloration I can from the equation.

    -- I want to see how close it would get to the tone I hear through my audio interface and a pair of 20Hz-20kHz studio monitors.

    In the design specification comments with the PDF it says:

    'Polyester wadding recommended, affix using staples'.

    Being an exacting anal programmer I have a problem with this statement:

    -- What is 'polyester wadding'? I am state side and am assuming this is polyester batting as in sold by the yard at fabric stores.

    -- If I am correct about this I see that batting comes in different 'weights' (light, mid, heavy and ultra). Would the weight matter?

    -- Do a line the entire interior of the cabinet with the batting?

    I am pretty sure the 'polyester wadding' is there for sound deadening. I am used to using

    Owen Cornings 703 and sometimes Roxul for sound deadening applications.

    Since the Celestion design is clearly for a DIY'r (wood glue, screws, table saw, jig saw is really all that is required)

    perhaps the suggestion for 'polyester wadding' is their because it is readily available?

    On the other hand if I where to utilize Owen Cornings 703 it is denser and thicker (1") and therefore would muck with the

    Thiele design of the box (less internal volume).


    My anal tendencies have me frozen like a deer in the head lights!

    I asked this question of Dr. Decibal at Celestion and have received no response.

    I suspect they think I am crazy.

    Opinions (and I understand that is what they would be) on guidance are most welcome.


  • I have received a response from Dr. Decibel!

    He / She said:

    The wadding isn’t essential, but it fools the speaker into thinking the air volume in the cabinet is greater than
    it actually is: it smooths out and extends the low end a bit.

    I did not ask the Dr. all of the things I stated in my original post, I simply asked them 'what is the polyester wadding for?'

    Perhaps the Dr. has a Kemper account. If so I will direct them to this posting, perhaps they will choose to answer here.

  • Hello !

    I did exactly what you want to try before I purchased the Kabinet. And I think I had exactly the same main question: How does it sound compared to the studio monitors I've tried ?

    indeed I tried two pairs of 8 inch studio monitors before (KRK-8 and presonus ones) and I've been very impressed by the sound it had. But it was just a 1 month trial and had to send them back. Since then I'm looking for the best speaker solution for me. I tried different things (PA speakers 12" Audiopro passive, 12"Yamaha, 10"Yamaha active, the home made cabinet with F12-X200, and finally the kemper Kabinet). My conclusion now is the following :

    1- first position : studio monitors is by far my favorite sound-nothing compares. but it's for home training situation, I'm quite sure in rehearsal or live situation it wouldn't be good anymore- not made for.

    2- second, not far : some details are well kept using good headphones (mine are AKG reference headphones I forgot the number), but it's when it is used quite loud

    3- at equality in the last position, all the series of 10" and 12" PA speaker active or passive I've tested (including the F12-X200, and except the Kabinet which is my 3rd position). They are all different, but they all loose A LOT of the "fine details" in the sound that makes the kemper so pleasant (don't know how to be more precise on this point, but it's very clear to me that it lacks, not in the EQ only, maybe more in the transients or something like this...)

    4- the Kabinet : it's a very good one (I kept it) because the "amp in the room" feeling is really something obvious at the very first second you try it. I couldn't try it yet in rehearsal, but, it's sure it's gonna make it. That being said, I find the sound quite different from both what I remember I had with the monitors, and the headphones. And I also experience (maybe a bit less) this lack of "details" compared to the monitors.

    A few last points, the home-made F12X200 cab is very heavy with its ton of plywood while the Kabinet is much lighter. And i thought I could reuse my F12X200 in a two-speaker daisy-chain configuration, but the kone and the f12X200 don't have the same impedence, so it's not so worth. And also I'm more in classical rock and blues sounds than in metal ones (it probably better for you to know where this opinion comes from)


  • Thanks for the input semguigui.

    Yes the cabinet is pretty heavy for a 1X12.

    -- 13 ply 18mm Baltic Birch is a lot heavier than standard plywood.

    -- The box is larger than a standard 1x12 due to the fact that it is designed with Thiele / Small parameters (the internal volume is needed).

    -- Even if it ends up weighing 40Lbs it is much better than my current Gemini 2 powered cabinet (70Lbs).


    Dr. Decibel response (Wadding / batting question).

    -- Yes 'wadding' is also referred to as batting.

    Batting weight (light, medium, heavy or ultra)

    -- The light density is what should be used.

  • Received the F12-X200's today.

    There is not a gasket in the box for front mounting the speaker.

    It is my understanding that the cabinet should be as air tight as possible (save for the port).


    Did you use some sort of gasket material when you built your cabinet?

    If so what did you use.

    -- I do not want to use the standard Celestion gasket pieces which I believe are pretty much made to apply to the front of the speaker for rear loading. This seems like a less than desirable option as the Celestion gasket material is pretty thick. Or am I wrong?

    -- I am thinking of using automotive from-A-gasket.

    Any ideas from anyone?

  • Yes It was perturbing for me to see that the gasket material on the speaker was for rear mounting, and quite thick and hard.

    I finally mounted it "front" and used what I found in my garage : an adhesive gasket band that you normally apply on the windows or the doors. It was very soft and became very thin once the screws were tightened. I think it does the job well enough.

  • Thanks semguigui.

    I will search around for some sort of material as you suggested to make a gasket out of.

    In case anyone else is reading this thread I have encountered another problem.

    -- I am going to apply a grill to the front of the cabinet.

    -- The position (in the vertical) of the speaker means that at the apex of the speaker I only have roughly 3/8" (9.52mm) space for the grill frame. I of course will apply a radius cut out to my frame but 3/8" is not very wide and will not be all that strong.

    -- I was planning to utilize 'Super Velcro Discs' to attach the which would mean a lot of tugging to get the grill off and I am worried that the 3/8" portion will be pretty week.

    I am not all that familiar with Thiele / Small parameters and can find no information pertaining to whether or not the location of the speaker and port are relevant (at least in the vertical plane). If they are not relevant I will move the speaker down and the port a little to the right,

    I have asked Dr. Decibel and will post their response when I get it.

  • RobD,

    You could always try a gasket sealer typically used for making automotive gaskets. It comes in various colors, but black may be better suited for the cab. It dries to a rubbery texture. I suggest you create a continuous bead around the cab or speaker, wait for it to tack, then mount the speaker. If you don't like it, then it can be removed w/ little effort.

  • Hi Rob,

    I didn't change the dimensions that Celestion give. I just did the round cutaway in my grill cloth frame where the speaker is too close to the edge. (see photos)

    In my case, by luck, I don't need to use velcro or anything because it holds very well alone. IN fact i chose to reduce by only 2mm the frame dimensions compared to the frame into which it has to be inserted, but with the added thickness of the grill cloth plus the staples, it's just enough to force against the frame, and when I add the last panel (see photo) it holds very well and i don't perceive any parasitic vibration (until now at least)

  • Dr. Decibel replies that the position of the speaker and port is not relevant within the design (i.e. it has nothing to do with Thiele / Small). He says they both can be positioned anywhere as long as neither of them end up touching anything (sides, each other). So I am repositioning both the port and speaker within the baffle to give myself ~7/8" thickness for the grill frame on the top and bottom of the speaker. I feel this is much better (stronger) than the ~3/8" defined by the design.


    I am extending the top, bottom and sides to extend out from the baffle (overhang) by 1 3/4" (not the 18mm specified). I am going to utilize SJ3463's to attach the grill frame to the baffle. These are by far superior to normal Velcro strips. The 1 3/4" gives me the clearance for the engagement thickness of the SJ3463's, semguigui's 2mm for staples and grill cloth thickness. This also allows me to be a little sloppy on the grill frame dimensions (undersize it slightly to make sure!).


    'guigui'? You a programmer?


    Thanks Bob. I am aware of form-a-gasket and it is my go to if I cannot find any other suitable gasket material. I am also aware that I could simply purchase a sheet of gasket material and cut my own. It would be nice though if speaker supply houses had a 1/16" thick, sort of soft, 12" gasket available! Plenty of 6.5" and 8" such animals available, but no 12".

    All (Just some babble for general readers) :

    Note: I am a very anal programmer. I will now put my anal tendencies on display for all.

    I am envious of all of you non state-side individuals whom have wood working tools and tape measures allowing you to cut on mm's! Metric->imperial measurements never work out. I have re-sized the design so I have cut lines on 1/8" and 1/16" inch marks. This has of course changes the interior volume of the cabinet (has made it larger). I am making up for this by re-sizing the battens (treated as bricks in speaker designer terms) so they take up more volume.

    It is my understanding from my reading of Thiele / Small that this is all really about the volume of free air contained within the cabinet along with the amount of air pressure created by the movement of the cone (flexing in and out). The circumference and length of the port provides a sort of throttling effect that provides 'back pressure' against the back of the cone at a certain pressure to keep it in equilibrium. So I believe that the slight resizing of my cabinet and matching the volume of my bricks to make up the difference does not effect the performance of the cabinet.


    I am utilizing T-nuts and machine screws to connect a pair of handles, four feet and the 8 machines screws that hold the speaker to the baffle. It took me several days to decide whether or not I should utilize a forstner bit to 'sink' the T-nuts into the plywood so they are flush, or to simply drive them in. If I drove them in then the surface of them would be sticking up above the surface of the plywood which would decrease the interior volume by roughly the circumference of the T-nut head * the thickness of the T-nut head. I say roughly due to the fact that a T-nut head is not a perfect circle as it has 'wings' on it. To minimize this I decided to utilize a forstner bit to the depth of the thickness of the T-nut head. This of course is still not perfect as the circumference of the forstner bit is a bit larger than the circumference of the T-nut head, and I still have the 'wings' issue. Utilizing the forstner bit increases the internal volume of air within the cabinet! This keeps me awake at night!

    I have thought I could get a finely graduated cylinder, fill it with liquid and then dip the T-nut into the liquid up until the bottom of the head. The difference in the level of the liquid would be the volume displaced by the head of the T-nut. I could then find the volume of my forstner 'indentation' and subtract the volume of the T-nut head from it. This would be the internal volume added to the cabinet by the presence of the T-nut. One would of course need to know the evaporation rate of the liquid chosen at the current room temperature, humidity and barometric pressure to be accurate with this measurement.

    And yes, I am aware that if I used wood screws to attach my hardware this is a non-issue, but that is not the point!



  • Woke up this morning with a clear head (un-cluttered by Thiele / Small, cubic volumes,...) and realized my answer to the additional volume created by the usage of a forstner bit and T-nuts is of course bondo (automobile body repair material)! I will simply fill in the gaps created with bondo and then sand it smooth (wood filler will not stick to metal, Bondo will stick to both metal and wood).