My speaker kleptomania has got out of control, time to use up some of the far too many drivers cluttering up my shed. The drivers in this project are all gathered from the side of the road, & the offer of some free MDF office partions provided the enclosure materials.
First the drivers, being broken in, in odd boxes I had lying around:
First the drivers, being broken in, in odd boxes I had lying around:
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The mids/tweets: these weren't my first choice, but before I pulled the drivers out of the box to install my original choices, I had a listen - not bad, so laziness won out.
The mid drivers came out of someone's reject computer speakers, labelled "Lonya" & are 4 ohm. No Idea where the tweeters came from.
A little searching & I came up with a rough FR plot I'd done for the Lonyas a few years ago - pretty flat from ~100Hz to 10Khz, except for peak at 2KHz. I doesn't sound to nasty, just gives a 'forward' sound to the drivers, which can be easily tamed if needed, but should suit the intended recipient who has slight industrial deafness. The tweeters match the mid sensitivity well, current xover is a small value cap.
The mid drivers came out of someone's reject computer speakers, labelled "Lonya" & are 4 ohm. No Idea where the tweeters came from.
A little searching & I came up with a rough FR plot I'd done for the Lonyas a few years ago - pretty flat from ~100Hz to 10Khz, except for peak at 2KHz. I doesn't sound to nasty, just gives a 'forward' sound to the drivers, which can be easily tamed if needed, but should suit the intended recipient who has slight industrial deafness. The tweeters match the mid sensitivity well, current xover is a small value cap.
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The woofers - first a pair of old style 'Sharp" woofers, smallish magnet, paper cone, cloth surround. I got a bit carried away when I cleaned the dust off these, so have dammared the cones to ensure they're nice & stiff:
The other woofers aren't a pair, both 'Pioneer' brand out of passive subwoofers, both paper cone with rubber surround. One has a smaller magnet than the other, but they have similar sensitivity. The Pioneer with the larger magnet originally had a blue cone; I painted it with Inkjet ink to make them appear the same:
I have done preliminary measurements of the drivers, but am giving them a pounding to loosen them up, before I do final measurements & decide on box tunings
The other woofers aren't a pair, both 'Pioneer' brand out of passive subwoofers, both paper cone with rubber surround. One has a smaller magnet than the other, but they have similar sensitivity. The Pioneer with the larger magnet originally had a blue cone; I painted it with Inkjet ink to make them appear the same:
I have done preliminary measurements of the drivers, but am giving them a pounding to loosen them up, before I do final measurements & decide on box tunings
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The boxes - the free MDF turned out to be only 9mm thick - damn, well I guess it's a challenge. Also being discarded was a removalist's blanket, so I used that to line the boxes. I used bituminous Auto 'sound deadener' to glue the felt to the MDF:
I doubled up to front baffle to give it a bit more strength, next weekends task is to cut out the driver holes & glue on the mid enclosure
I doubled up to front baffle to give it a bit more strength, next weekends task is to cut out the driver holes & glue on the mid enclosure
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A couple more comments - why this size box? I plan to built another version of these using higher quality drivers I have, & this was the max size I could get out of a 1200x900 sheet of ply, without building square towers, They're ~ 55L which is roughly the total of the test box volume.
Crossover - they sound OK using simple 1st order, 2.85mH on the parallel woofers & 47uF on the mid. The mids may need to be padded back a tad, but that'll probably depend a bit on how the woofers sound with their final box tuning - they sound OK in the test boxes which I think are tuned somewhere the low 40s (left over from other projects)
Crossover - they sound OK using simple 1st order, 2.85mH on the parallel woofers & 47uF on the mid. The mids may need to be padded back a tad, but that'll probably depend a bit on how the woofers sound with their final box tuning - they sound OK in the test boxes which I think are tuned somewhere the low 40s (left over from other projects)
Job Done, Beer O'Clock
Measurements - turns out the best way to match up the bass response is to go for an EBS alignment; However, the 'pair' of drivers were more disparate that the odd woofers, one in particular measuring quite badly, I'll probably substitute another similar looking driver which I know measures better.
Measurements - turns out the best way to match up the bass response is to go for an EBS alignment; However, the 'pair' of drivers were more disparate that the odd woofers, one in particular measuring quite badly, I'll probably substitute another similar looking driver which I know measures better.
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Ready to rock:
Crossovers - simple 1st order, 2x 47uF on the mids/tweeters, 1uF to the tweeter,
& a couple of odd inductors total 1.46mH for the woofers.
Sound - well, they pass the Rammstein test
I may add a small resistor in series with the mids/tweeters, but the balance isn't bad... except that one of the odd woofers is a bit louder than the others...
Crossovers - simple 1st order, 2x 47uF on the mids/tweeters, 1uF to the tweeter,
& a couple of odd inductors total 1.46mH for the woofers.
Sound - well, they pass the Rammstein test
I may add a small resistor in series with the mids/tweeters, but the balance isn't bad... except that one of the odd woofers is a bit louder than the others...
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Solved the imbalance problem by swapping the paper cone drivers between boxes; unfortunately the nice low bass being produced form one side diminished, but still a good balance overall. Might swap out the paper cone drivers for a couple of poly cone drivers which I know are good. But what really impresses me is how good the thin 9mm mdf & gooped on blanket worked as a cabinet material. In fact I've cut out another set of boxes from the mdf for the above mentioned 'store-bought' drivers...got some glue to slather today...
The construction and finish of the boxes looks like good craftsmanship. How did you join those thin MDF panels in achieving a pyramid?
How about the speaker design, is this your own or from someone else? Now, instead of a collection of road kill drivers cluttering your shed, you will have a pair of speakers taking up a lot of space. You must plan to have the pair that you are building now to eventually be located elsewhere.
-Pete
How about the speaker design, is this your own or from someone else? Now, instead of a collection of road kill drivers cluttering your shed, you will have a pair of speakers taking up a lot of space. You must plan to have the pair that you are building now to eventually be located elsewhere.
-Pete
Hi CT,
re: "How did you join those thin MDF panels" - PVA & lots of clamps
OK I cheated, the top & bottom plates don't have the angle of the pyramid, so I used some construction adhesive along the inside of those joins. (I really need a table saw to get the angles right, everything is cut with a hand held circular saw)
The design - my own; this first set going to a mate who has plastic cr@p on a stick as his HT system; the second set with the $pendy drivers will be an upgrade to the mains in my own HT system
re:"The construction and finish of the boxes looks like good craftsmanship" - thanks, but you probably wouldn't say that if you saw them close up, the finish is just 3 coats of enamel from an old tin I had in the shed
re: "How did you join those thin MDF panels" - PVA & lots of clamps
OK I cheated, the top & bottom plates don't have the angle of the pyramid, so I used some construction adhesive along the inside of those joins. (I really need a table saw to get the angles right, everything is cut with a hand held circular saw)
The design - my own; this first set going to a mate who has plastic cr@p on a stick as his HT system; the second set with the $pendy drivers will be an upgrade to the mains in my own HT system
re:"The construction and finish of the boxes looks like good craftsmanship" - thanks, but you probably wouldn't say that if you saw them close up, the finish is just 3 coats of enamel from an old tin I had in the shed
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Pete,
A table saw is a big help. This past spring, I thought that I had found a discarded portable table saw that could be repaired without too much difficulty but I was wrong. The expense of new table saws and my lack of a really large enough work area means that I continue to use a hand-held circular saw.
It is possible to use a clamped guide with the hand-held saw to get a straight cut. Using the guide it would be possible to make an angled cut too, but then the guide is for one angle only.
Really, a table saw makes life a lot easier if you can afford one and have the space.
The pyramid-like design is not bad. Make it closer to a true pyramid, and then you will really have a problem with the joints and at the extreme you lose close to two- thirds of internal volume (compared to a rectangular box with the same height and dimensions of the base).
A table saw is a big help. This past spring, I thought that I had found a discarded portable table saw that could be repaired without too much difficulty but I was wrong. The expense of new table saws and my lack of a really large enough work area means that I continue to use a hand-held circular saw.
It is possible to use a clamped guide with the hand-held saw to get a straight cut. Using the guide it would be possible to make an angled cut too, but then the guide is for one angle only.
Really, a table saw makes life a lot easier if you can afford one and have the space.
The pyramid-like design is not bad. Make it closer to a true pyramid, and then you will really have a problem with the joints and at the extreme you lose close to two- thirds of internal volume (compared to a rectangular box with the same height and dimensions of the base).
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