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Thread: A speaker project

  1. #31
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    Quote Originally Posted by RothwellAudio View Post
    Vented enclosures need to be carefully designed to avoid the port resonating at the wrong frequency and doing peculiar things to the bass. The easiest thing to do would be to use the same enclosure volume and port dimensions as the original cabinet.
    No argument there (and already suggested earlier) - however, see initial posts in the thread about why this didn't happen - particularly post #3:

    "OK - I should stress at this point that this project was no more than simply having a bit of fun and maybe learning a little along the way (without getting a headache from thinking too much)"

  2. #32
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    Sorting out some grilles with the only bit of 9mm MDF to hand (sorry Paul Klee - you had to go...)



    Cladding them (oodles of scrim left over from my Quad 22L refit):



    A couple of bits of stick-on Velcro and 'up and away'


  3. #33
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    Finally put them back together this afternoon and added some pillow stuffing (my wife magicked a Boyes' bag full from the spare room)

    Into the shed and RPi plugged in for some AIFF renditions of popular tunes from the 90s (and even earlier). ..

    How did they sound? ... well actually quite splendid, enough bass to satisfy my needs and a surprising amount of upper end definition. The sound was definitely an improvement on what I remember from years of listening to the DM-10s in their original form ... less woolly at the bottom end and with a fuller mid to high presence. As with the initial 'open baffle' experience the most noticeable improvement was a distinct sense of presence and space - a directness that really grabbed me.

    As to to top-end roll off, I am not a great judge of that given that I get a pretty sharp fall off at about 8 - 8.5 kHz so I asked my wife to have a listen (her hearing range exceeds mine by a long chalk, being younger - and a woman). She couldn't detect anything miss with what she was hearing at all, listening to a range of tracks from Portishead and Massive Attack. Later I tried a few tracks from Art of Noise 'In Visible Silence' - the speakers handle stuff like 'Paranoimia' and 'Peter Gunn' with ease but also the more sensitive 'Camilla' was handled with aplomb.

    Was it the last word in listening pleasure, audio nirvana and a giant killing solution? - of course not, and I never expected them to be. But for a total cost of £1.80 to replace two 2.8mm spade connectors that had rotted, I have a pair of worthy boxes that will enliven my summer days in the garage




    Flickr
    Last edited by mikmas; 29-06-2018 at 21:23.

  4. #34
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    Bravo Mike! A good effort! And a great learning experience I’m sure. And, your project need not stop now. You could do some math, figure what length port they would need and drill a hole, and glue a paper towel roll into the hole. I’ve got books on the shelves around here somewhere with the equations for such things, from back before they made all the computer programs that calculate all this stuff for us. A properly installed port can give a bit of deeper bass, and less boxy or boominess to the sound.

    Perhaps keep your eye out for some ratted out old car speakers? Coaxial, or triaxial types, with the tweeter suspended over the woofer. If the woofer is rotted out the tweeter may still be fine, as they are mostly plastic. And on car type speakers you’ll see a small capacitor glued right behind the plastic tweeter mount. You could simply wire it right in at the terminals and mount them right on the tops of your boxes. Instant two way speaker! B&W style, with the top mounted tweeter, enclosed in a shampoo bottle painted black or something.

    Hind sight is 20/20, and you did a fine job. In the future you may want to observe the Golden Ratio on speaker dimensions. 3x6x9? Something like that, I’m sure a Google search would turn it up? And I really like your grills! And the stuffing, I was thinking some pillow fill, (polyfil), sells for $10 a bag at speaker parts stores, but you can buy the exact same stuff at the fabric shop for $2. Your wife was on the spot with that one!

    I’m not sure why, but speakers you built yourself always sound a bit better than store bought, a little pride of ownership and sense of accomplishment could be causing a bias?

    I’ve got notebooks full of fantastic speaker designs! All calculated to exacting tolerances with crossover designs, using expensive drivers, etc. etc.. but the difference between mine and yours, mine are still on paper and yours are up and running! Bravo!
    And love the shop, looks like a place where things get done.

    Russell

  5. #35
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    Quote Originally Posted by alphaGT View Post
    Perhaps keep your eye out for some ratted out old car speakers? Coaxial, or triaxial types, with the tweeter suspended over the woofer.
    Yes. Car speakers can be extremely good, but seem to be looked down upon by the Hi-Fi fraternity (the usual 4 ohm load puts some off too).

  6. #36
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    Quote Originally Posted by alphaGT View Post
    Bravo Mike! A good effort! And a great learning experience I’m sure. And, your project need not stop now. You could do some math, figure what length port they would need and drill a hole, and glue a paper towel roll into the hole. I’ve got books on the shelves around here somewhere with the equations for such things, from back before they made all the computer programs that calculate all this stuff for us. A properly installed port can give a bit of deeper bass, and less boxy or boominess to the sound.

    Thanks for the kind words Russell
    To be honest I doubt I'll be doing much more of this - I like to keep active if only to give my finger joints some exercise (they get really creaky and crampy during the winter months..) but serious speaker design and construction doesn't quite rock my boat. I still can't quite get my head around the whole 'wave' business. If I hadn't had the speakers going begging I would probably have made a hat stand or something

    I didn't get a lot of time to listen today because we had to be somewhere else but I was actually quite surprised they they didn't sound like complete shite given by what I had read beforehand and also what others have said earlier in this thread. I think they will be very music mode dependent - I did listen to a short piece of classical via BBC 3 on the RPi but they clearly aren't subtle enough for that, smooth jazz would also probably suffer (might try a little Coltrane though tomorrow if I get the chance)

    As to adding a tweeter, if you look at the top of the bookshelves on the shed picture you might just make out a Harman Kardon SoundStick tweeter set; I picked up a pair from a junk shop a while back for £10 and I might lash them in at some point and see what they do ... but to be honest I don't really feel the need and also have some fairly urgent domestic paintwork to attend to ... (the balance is important)

    The shop was a garage - only problem is it was built for very narrow cars. I had a mini for a while but if I drove it in there I could only just get out the car .... so now it just serves as a general dump for boxes in Winter and a place for me to tootle about in the Summer. Most of the time it looks like what we generally refer to in the UK as a 'shithole'

  7. #37
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    Quote Originally Posted by mikmas View Post
    I still can't quite get my head around the whole 'wave' business
    Talking of 'waves'. Now is the time to consider bunging those drivers in a quarter wave transmission line cabinet system with suitable tweeters etc.

    Something like this:



    Those drivers are likely to be well suited and the bass response will blow your mind!

  8. #38
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    Quote Originally Posted by walpurgis View Post
    Talking of 'waves'. Now is the time to consider bunging those drivers in a quarter wave transmission line cabinet system with suitable tweeters etc.


    Those drivers are likely to be well suited and the bass response will blow your mind!
    No problem Geoff - you send me all the wood cut to size ... and I'll supply the glue

  9. #39
    Join Date: Apr 2015

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    Quote Originally Posted by mikmas View Post
    Thanks for the kind words Russell
    To be honest I doubt I'll be doing much more of this - I like to keep active if only to give my finger joints some exercise (they get really creaky and crampy during the winter months..) but serious speaker design and construction doesn't quite rock my boat. I still can't quite get my head around the whole 'wave' business. If I hadn't had the speakers going begging I would probably have made a hat stand or something

    I didn't get a lot of time to listen today because we had to be somewhere else but I was actually quite surprised they they didn't sound like complete shite given by what I had read beforehand and also what others have said earlier in this thread. I think they will be very music mode dependent - I did listen to a short piece of classical via BBC 3 on the RPi but they clearly aren't subtle enough for that, smooth jazz would also probably suffer (might try a little Coltrane though tomorrow if I get the chance)

    As to adding a tweeter, if you look at the top of the bookshelves on the shed picture you might just make out a Harman Kardon SoundStick tweeter set; I picked up a pair from a junk shop a while back for £10 and I might lash them in at some point and see what they do ... but to be honest I don't really feel the need and also have some fairly urgent domestic paintwork to attend to ... (the balance is important)

    The shop was a garage - only problem is it was built for very narrow cars. I had a mini for a while but if I drove it in there I could only just get out the car .... so now it just serves as a general dump for boxes in Winter and a place for me to tootle about in the Summer. Most of the time it looks like what we generally refer to in the UK as a 'shithole'
    There’s certainly no hurry on jumping back on the speakers, as long as they make you happy. But, in a few months if you get curious attach those tweeters and perhaps it will handle a classical tune?

    I too am one to work on projects as the urge arises, I’ve got two guitars that don’t belong to me waiting for work, I’ve had them several months, and I told the owner that he doesn’t want me to be straightening necks and leveling frets until I’m good and in the mood. So far he’s been patient.

    Russell

  10. #40
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    Just to follow up on the latest ...
    Having listened to them occasionally over the last couple of weeks and enjoyed what I heard, I decided that time was to pop in a port.
    Following Geoff's suggestion earlier, I opted for a down firing one and did a quick scale sketch on graph paper to check for placement:



    ... followed by some swift jiggerypokery with a jigsaw to fabricate a home for the original port tube:


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