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The Bantams Micro Speaker System

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  • Audio.Novize
    replied
    Thank you!

    Regarding your question: I was actively looking online for small-sized speakers for my desk - and "somehow" I found the Bantams. And I am very happy I did!

    Leave a comment:


  • tomzarbo
    replied
    Great job, they came out nice, the stone look is great for a small speaker like this. I'm glad you like them.

    The flexible putty you used for the tweeter is a nice way to seal it up as well. These tiny speakers sure are interesting to get put together.

    Just curious, did you see this design in the AudioXpress magazine or just online somewhere?

    TomZ

    Leave a comment:


  • Audio.Novize
    replied
    For certain aspects regarding the build of the Bantams, I chose a slightly different approach. Maybe some of them are are helpful for others:

    The cutouts for the chassis I did with the help of a circle hole cutter (that attaches to a regular drilling machine):
    Circle Hole Cutter

    To prevent the screws from getting lose over time in MDF (or if installing the chassis multiple time) I glued little MPX pieces on the back of the front baffle:
    MPX pieces for screws

    For the sealment of the tweeter I didn't use glue or silicone, but instead a kneading mass (which allows easy removement of the chassis if necessary; it also allows for installing the tweeter after completely building/glueing the speaker case):
    Sealment Tweeter

    Instead of using a terminal - and since space is limited - I used press-in sockets:
    Press-in Sockets

    With respect to damping I chose 4mm of felt for the sides as well as the for the top and bottom of the speaker case. Also, I added one "sheet" of damping between the chassis and the cross over:
    Damping

    Leave a comment:


  • djg
    commented on 's reply
    Well, the pictures aren't in German. Nice writeup (I assume) and pics.

  • Audio.Novize
    replied
    Just a quick update: I finished building the Bantams & I am super happy: They are amazing!

    But what did I do wrong: Are the Bantams supposed to play as of 40 Hz? Seriously, there almost seems to be a glitch in the matrix: How can (passive) speakers of that size produce such a low bass at full volume?

    If someone is interested, I documented (and am still documenting) the build in a German forum - of course, it's in German, but I also included a fair amount of pictures: http://www.hifi-forum.de/viewthread-205-1138.html

    TomZ: Thank you again, what a great little speaker you have developed!

    Leave a comment:


  • Audio.Novize
    replied
    Great, thanks for the quick answer!

    Leave a comment:


  • Wolf
    replied
    That difference in DCR is negligible.
    Wolf

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  • Audio.Novize
    replied
    Hi TomZ,

    First of all: Thanks for your development and the time and efforts you put in documenting it!

    Since I'm located in Germany it seemed unreasonable to get the necessary parts directly from Parts Express due to pretty high shipping costs. Thus, I ordered from a company located in the Netherlands (Soundimports). Luckily, I found all parts as listed - except for one: Instead of the air coil from ERSE I got one from Mundorf, which has a 0.01 higher DCR, see here. Does that matter? (Sorry, if this a complete noob question ...)

    Unfortunately, I have to wait until the middle of August before the parts are delivered. But as they say: Anticipation is the greatest joy ...

    I'm super excited to see, I mean hear how the Bantams will perform against the Microspeaker µ from Quint, which I built not too long ago - both speakers have pretty much the same size ...

    Audio Novize

    Leave a comment:


  • tomzarbo
    replied
    Dukk,
    That is a nice trick. I went lazy, there was no way I was breaking out the circle jig when I had a fostner bit that was 'close enough'
    TomZ

    Leave a comment:


  • Dukk
    replied
    I like to template any hole I need to make. If I make a hole that is slightly oversize, I will put heatshrink on a flush-trim bit's bearing so that the copy is slightly smaller. Varying the number of layers of heatshrink can really zero in on the right hole diameter. I use scraps of 1/2" for this and then label the scrap piece to what the hole is for.

    I did this recently to make rear mounts for 1.25" PVC vents and it worked very well.

    Leave a comment:


  • tomzarbo
    replied
    The AMT Tweeter body is round...you can cut the hole for the tweeter any size you want, it all depends on the method you use. I used a Fostner bit that was close to the tweeter barrel size as the set I own didn't have one that was exactly the same size. On the first set I built, I used foam sealant to mount the tweeters. That proved to be difficult to mount, so for the next few sets, I made the hole slightly smaller and used a few wraps of electrical tape to make the fit tight. Ultimately, sealing the tweeter to the baffle with silicone really does a fine job of securing it, as well as sealing it, at least on the 6 Bantam-themed projects I've done so far.

    If you can make the tweeter opening basically the same size as the tweeter barrel, than that's less work you have to do. I just didn't have an exact match for it, so that's why I used the 'build up' method with foam and tape. On occasions where I've made an opening smaller and tried to sand a perfect circle uniformly to get a slightly larger opening, it usually seems to be difficult to pull this off and you end up going from "It doesn't fit yet" to "heck, well now it's a little loose" in one sanding step. Often a "Press-Fit" tweeter will be spec'd to mount in a 'standard' size opening and be designed with a slightly tapered barrel so it "snugs up" slightly as you press it in the cabinet. These, being stand-alone automotive tweeters are not built that way.

    Regarding sealing things up... yup, Wolf's got it, I was speaking of where the wire exits the plastic housing.

    Here's a pic of what I'm talking about...

    Click image for larger version

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    The tweeter being designed as an automotive type driver doesn't need to be sealed up if used in an automotive environment... it was never intended to be used in a speaker cabinet, just 'taped' to an A-pillar in a car. The pressures inside a speaker cabinet will likely act on the tweeter, causing unwanted vibrations of it's diaphragm of some type... that's why I sealed up where the wire leaves the plastic tweeter body.

    TomZ

    Leave a comment:


  • Wolf
    replied
    Tom was referring to the wiring into the tweeter needing sealed, not the perimeter of the mount. A lot of times automotive products are not under the same pressure stresses as home audio drivers because they are not installed inside the same cabinet. For example- these would likely sit atop the dash, or be placed into an A-Pillar. The wiring from rear to membrane may very well be open, allowing an air-leak from the woofer pressure to intrude to the membrane of the AMT and add some unwanted flexure to its operation.

    Later,
    Wolf

    Leave a comment:


  • Trdat
    replied
    Originally posted by tomzarbo View Post

    Thanks for the kind words, I'm glad you guys are enjoying them. They are our main speaker system combined with my "Tenacious Bass-8" subwoofer system and we don't feel like we're missing anything sound-wise. I'd love to take the credit for them turning out to be such a great-sounding design, but I think I may have gotten 'lucky' a bit with the combo. :

    I didn't get a notification that you had replied, thanks for your response. The round over is exposed so not sure what is going on with what my wife is hearing. It could also be the AMT itself with it unique tweeter sound signature all my other tweeters are soft dome with one being hard dome but she definitively hears something. Still loves it just being a critic due to everything around her being speakers and audiophilery....

    Also, If I am not mistaken, apologise if it was my mistake but the cutout you gave for the AMT was slightly larger. The hole could of been a few mm smaller making the fit for the tweeter more firm, I used your method of using double sided tape to fit it in and it worked good and did seal it tight. But I am wondering why we couldn't cut the exact hole for the AMT? Is the AMT a perfect circle?

    I did add sealant behind the tweeters, I am a fanatic when it comes to sealing enclosures so leakage would be minimum. But reading your post a second time do you mean sealing the tweeter off around the cutout or behind the wiring? I don't understand why the wiring would need sealing? Also can you exactly confirm where I need to seal cause I am bit confused?







    Leave a comment:


  • tomzarbo
    replied
    Originally posted by Trdat View Post
    Tom,

    I am a avid participant on this forum and after building the Bantam's I have been meaning to write a praise post. I just would like to say firstly thanks for your effort in the design my project came out very successful and turned out beyond what I thought a micro speaker can pump out.

    The speaker is absolutely awesome, not just the SPL the general quality of the sound and the bass is phenomenal. I would like to add though that my wife does hear either some distortion in the high frequencies which obviously I can't hear, this could be the cheap tweeter(which isn't that cheap) or just general high frequencies that sound too silibant or the tweeter type. It could also be the lack of time alignment which isn't something we would expect at this price point or simplicity but something makes my wife think that something isn't right then again it could pertain to my specific build.

    Putting that mild criticism aside, the speakers pump I love them. There is something about the transients i adore, can it be the small woofer? I know passive radiators don't match the transients of closed box and even a ported design but perhaps it is the tiny woofer.

    Now and again I got to pull out the Bantam's hook it up to a descent DAC and power amp and listen to them. And sometimes it gives more pleasure than my main DIY set up which is worth close to 10k. So thanks the design I am sure the DIY community appreciates it.


    Thanks for the kind words, I'm glad you guys are enjoying them. They are our main speaker system combined with my "Tenacious Bass-8" subwoofer system and we don't feel like we're missing anything sound-wise. I'd love to take the credit for them turning out to be such a great-sounding design, but I think I may have gotten 'lucky' a bit with the combo.

    As to the high frequency distortion your wife is hearing, I have two theories...

    When I originally was testing different methods to mount the tweeters, I ended up testing slightly different "depths" with each mounting method. When I took measurements with Omnimic, I noticed that variations in depth caused somewhat different high-frequency responses. The mounting depth that gave the smoothest response -- and the one I ended up using -- was to mount the tweeter so that the tweeter body protruded just to where the barrel began to curve towards the front and no more. In other words, the roundover on the tweeter face should be fully exposed, or proud of the baffle, but no further -- the tweeter should not be flush to the baffle.

    Click image for larger version

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    I suspect that may be what you are hearing... a response signature that has a few more 'jaggies' to it than if the tweeter is mounted exactly as pictured above. I didn't save the response graphs of those less-than-optimum mounting depths -- and they weren't awful by any means -- but they were not as flat as the above mounting and 'may' be what your wife is hearing. That's the only bad thing about using these tweeters -- the mounting can be a little tricky.

    One more possible cause... did you seal off the tweeter back where the wire exits the housing with caulking or sealant? I suspect the tweeter is not 'air-sealed' as it wouldn't need to be since it is intended to be used as an automotive tweeter. That 'could' cause some weird flexing of the tweeter membrane due to pressure changes inside the cabinet which may be heard as 'distortion' of some sort.

    Without seeing your speaker I can't be sure, but I haven't heard anything I would consider 'distortion' from the AMT tweeters, and it seems that the response directly from the driver itself is unlikely to be the problem. They are crossed over pretty high at around 6,500 to 7,000 Hz, and they use a third-order crossover, so they are well within their safe and 'comfortable' limits.

    I've built half a dozen of these speakers and have not heard anything I would consider 'off' on the high end, even at loud volumes, so I suspect one of these issues may be the cause.

    Hope this helps, take care,
    TomZ



    Leave a comment:


  • Trdat
    replied
    Tom,

    I am a avid participant on this forum and after building the Bantam's I have been meaning to write a praise post. I just would like to say firstly thanks for your effort in the design my project came out very successful and turned out beyond what I thought a micro speaker can pump out.

    The speaker is absolutely awesome, not just the SPL the general quality of the sound and the bass is phenomenal. I would like to add though that my wife does hear either some distortion in the high frequencies which obviously I can't hear, this could be the cheap tweeter(which isn't that cheap) or just general high frequencies that sound too silibant or the tweeter type. It could also be the lack of time alignment which isn't something we would expect at this price point or simplicity but something makes my wife think that something isn't right then again it could pertain to my specific build.

    Putting that mild criticism aside, the speakers pump I love them. There is something about the transients i adore, can it be the small woofer? I know passive radiators don't match the transients of closed box and even a ported design but perhaps it is the tiny woofer.

    Now and again I got to pull out the Bantam's hook it up to a descent DAC and power amp and listen to them. And sometimes it gives more pleasure than my main DIY set up which is worth close to 10k. So thanks the design I am sure the DIY community appreciates it.



    Leave a comment:

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