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Post by John on Dec 13, 2019 7:02:50 GMT
I remember about 8 years ago someone building a line array with these speakers he lived in Scotland on one of the islands and makes power supplies He even built a amplifier to cope with the load RD was very impressed with his amplifier design
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Post by MartinT on Dec 13, 2019 7:04:55 GMT
Is that Paul Hynes, John? I still have a couple of his PSU modules, which are very good.
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Post by John on Dec 13, 2019 7:05:50 GMT
Yes that the name Paul Hynes
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Post by karatestu on Dec 13, 2019 15:56:06 GMT
Some more buggering about with speakers......when will it end ? I moved the platform with little cuboid on right over the top of the up firing clamshell isobaric bass driver, resting on four wooden legs. Time aligned it best i could by having the front facing tweeter dome above the middle of the bass driver's magnet. I really like this. Having the magnet facing out on the bass driver and facing upwards seems to be a winner. The basket doesn't hinder output and the spread of sound is more room filling than having the cone facing outwards. There is maybe slightly less mid range coming from the bass driver with magnet out as it blocks the centre of the cone and dust cap area. Tweeter is now 100cm from the floor which is probably about 5cm too high. No strange rattles or booming bass so far but i haven't played Portishead dummy yet (that is my deep bass test CD). Currently listening to Air -Moon Safari. Another of my test CD's. The bass is lovely and full sounding and the rich texture of it on this CD is gorgeous. Finally found my scribbled notes about the 12" driver's T&S parameters from a site which is no longer on the net. Vas is quoted as 183.6 litres. They recommended a sealed enclosure of 70 litres with 470uf ballast capacitor for Qtc of 0.71. I expect this ballast capacitor is a filter to roll off the bottom end . Not going there thank you. Qts is quoted at 0.4 which i don't believe, i think it is higher than that especially with the added mass from cone doping. EBP with the quoted figures (which i don't really trust) works out at approx 50 which definitely means the 12" drivers are more suited for closed box loading. I remember way back running the figures through winISD speaker design software (it's a free download ) and it came up with 84 litres for qtc of 0.7. Having tried that i think it is bollocks. Something doesn't quite add up as the bass was too much meaning a too small box volume. Currently with 84 litres behind the inner driver in isobaric that corresponds to a Vas of 168 litres - not far off the 183.6 litres i got from the net. I am going to add things inside the cab to reduce the volume as i think it could do with it, bass is just a bit too tight and lean now. This all leads me to distrust the TSP i have :think: I have just had another idea......back soon.
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Post by karatestu on Dec 13, 2019 15:59:35 GMT
I have just come up with the design i have drawn below. Hope it makes sense, it's just a rough sketch. Up firing clamshell isobaric 12 inchers in a floor standing box. The dotted lines represent four legs, one in each corner. Then the top enclosure which holds the 5" mid bass and tweeters. I thought it would be interesting to try one 5" down firing magnet out into the same space between the two cabs as the 12" . Neither of those two drivers would be seen as i would cover the gap on each side with grille material. Another 5" up firing on top along with a tweeter and additional tweeters firing forward and to both sides. The two 5" would be in a push/push configuration and wired in parallel and in phase with each other. If i am thinking correctly this push / push arrangement will cancel out a lot of the cabinet vibrations . Wired in parallel to increase efficiency as these 5" drivers are the most inefficient out of the three. I don't think there is room to add side firing 5" drivers but i will have a think about it. Thoughts turn to how would the 12" and 5" drivers perform facing each other in a gap in the enclosure ? Is it some kind of slot loading or what ? I like how the 12" is performing at the moment firing in to a panel above. Only trying it will tell, the devil is in the detail as always
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Post by John on Dec 14, 2019 6:48:14 GMT
Do report back on how it goes. If you ever in London and want to hear what a baffle-less approach sounds like give me a pm
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Post by karatestu on Dec 14, 2019 7:47:53 GMT
Will do john. I need to make a highly aesthetically pleasing add on enclosure and buy some more drivers. Thanks for the offer to hear your drivers that is very kind. Living in North Yorkshire i don't get down to London village very often. In fact it has been over 15 years since i have been. Went to Lego land Windsor this year but that doesn't count
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Post by karatestu on Dec 15, 2019 14:21:23 GMT
How about a speaker enclosure made out of stacked tyres ? Would be good for up firing clamshell isobaric 12 inchers maybe. The trye side walls could possibly do something similar to the Hartley Boffle. Would it be rigid enough or need some reinforcement ? Would need to think of a way to cover the outside - bendable ply with lots of adhesive or filler to fill in the gaps, stick the plywood and make it inert. Up firing drivers would be no problem but how would one put drivers in the curved area where the tread is (was if you use worn out tyres) ? Cut a section out and bridge the gap with a piece of wood just big enough to mount the driver ? Need to think more about this
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Post by MartinT on Dec 15, 2019 14:31:31 GMT
You can't beat a nice bit of wood for an enclosure. Small (Mini?) tyres inside could be an excellent cheap damping treatment. Look at the skips outside of tyre shops.
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Post by karatestu on Dec 15, 2019 17:47:27 GMT
Well i would need to cover the tyres with something so why not wood. Thing is i kind of like the idea of the enclosure being round so that would mean bendy plywood.
Mini tyres might be the right size. Anything from 12" up . Then there is the depth of the sidewall to take in to consideration as well. Worn tyres are the wah to go -ones a garage are throwing out. Maybe i could get them for free. Thing is they all need to be the same size..
If i had all my 12" & 5" drivers up and down firing i just need to find a way to mount three tweeters on the rounded side. That's the tricky bit.
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Post by ChrisB on Dec 16, 2019 5:06:01 GMT
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Post by karatestu on Dec 16, 2019 5:19:00 GMT
Hi Chris, Of course you are right and it is uses a very different material. I was hoping no one would notice my error . Surely the side walls will have an effect for better or worse ? Edit - maybe material can be added to progressively reduce the holes then increase them.
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Post by ChrisB on Dec 16, 2019 5:28:14 GMT
I am sure you're correct. In the meantime, just for fun and for the sake of ensuring cross compatibility between the two materials, maybe we could try assembling some tyres out of felt underlay. Could be fun?!
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Post by karatestu on Dec 17, 2019 12:55:32 GMT
Experimenting with tyres is put on hold until i.........get some suitable tyres True infinite baffle is on hold too. Needed a fix from messing around with something. I have messed with a leaky bass box not too long ago and liked what it did. That was just a small 6mm hole drilled through the back panel. The theory says it lowers the magnitude of the resonant frequency peak, makes the enclosure seem bigger and increases Fs (frequency of resonance) slightly. Well i have tried it again but this time with a 5" hole on the back panel. Stuffed it with some slightly over sized foam which moulds to the edges of the circular cut out. It has had quite an effect on the bass. I am pretty sure this is going to be a permanent feature of my speakers but obviously done in a neater fashion when final build happens. Yes i keep saying that and then i decide to mess about with something else The beauty of this is it can be tweaked even after the speakers are finished by altering the type of stuffing and thickness of it. I could also make it so it can be blanked off fully when not required and maybe other partial blanking plates to change the size of the hole to suit. A bit like a tone control or bass boost for quiet listening . Some of the electronic music i listen to can be a bit too bass heavy at times - well this aperiodic vent has tamed it no question about it. But i also listen to electric and acoustic jazz and other well behaved music where sometimes i wish i had a bass tone control. Yeah shoot me now . I don't think i have veered too far from the sealed box loading. It is not a tuned vent like a bass reflex (although it does leak a small amount of out of phase sound through it). I have not put any stuffing in the box so my hfs credentials are hopefully still in tact All in the pursuit of tight, deep, tuneful and room filling bass which is full of the texture and detail that i know real bass has (guitar, acoustic or electronic). The plus of all this is the reduction of cabinet volume required. I have some scope now to decrease the volume which is a good thing when it comes to getting these past the wife when i do the final build. There is no need to but an aperiodic vent on the 5.25" mid bass drivers as their required cabinet volume is tiny in comparison and their zmax at Fs is relatively well behaved. Only thing is that if the mid bass share an enclosure with the 12" bass drivers then they will have to be aperiodically vented. I will cross that bridge when i come to it as current thinking is along the lines of a separate enclosure with up and down firing 5" drivers which is above the up firing 12 " driver (as per my hand drawn sketch i posted recently). If that design turns out to be crap then the drivers may be all sharing an enclosure. Time will tell. Anyway, back to the tunes
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Post by karatestu on Dec 17, 2019 12:57:12 GMT
My cheap crap chipboard enclosure panels are vibrating a lot less too
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Post by MartinT on Dec 17, 2019 12:59:45 GMT
I have messed with a leaky bass box not too long ago and liked what it did. That was just a small 6mm hole drilled through the back panel. The theory says it lowers the magnitude of the resonant frequency peak, makes the enclosure seem bigger and increases Fs (frequency of resonance) slightly. Well i have tried it again but this time with a 5" hole on the back panel. Stuffed it with some slightly over sized foam which moulds to the edges of the circular cut out. It has had quite an effect on the bass. I am pretty sure this is going to be a permanent feature of my speakers but obviously done in a neater fashion when final build happens. I guess the maths would call it an extremely short ported cabinet for the sake of calculations.
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Post by karatestu on Dec 17, 2019 13:04:37 GMT
I have messed with a leaky bass box not too long ago and liked what it did. That was just a small 6mm hole drilled through the back panel. The theory says it lowers the magnitude of the resonant frequency peak, makes the enclosure seem bigger and increases Fs (frequency of resonance) slightly. Well i have tried it again but this time with a 5" hole on the back panel. Stuffed it with some slightly over sized foam which moulds to the edges of the circular cut out. It has had quite an effect on the bass. I am pretty sure this is going to be a permanent feature of my speakers but obviously done in a neater fashion when final build happens. I guess the maths would call it an extremely short ported cabinet for the sake of calculations. Quite possibly Martin. Just don't mention the word ported. Oh no i said it I will be strung up
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Post by MartinT on Dec 17, 2019 13:11:46 GMT
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Post by ChrisB on Dec 17, 2019 13:45:51 GMT
Maybe 'porous' would be better!
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Post by karatestu on Dec 17, 2019 14:14:52 GMT
Porous - that's brilliant. I will use that term to describe my aperiodic bass cabs from now on Currently testing my porous bass speakers with some bass heavy material. It's a plus that i get to listen to music whilst doing my paperwork. Herbie Hancock - Secrets Portishead - Dummy Morcheeba - Big calm Gorillaz - Demon days Jamiroquai - Funk Odyssey Beck - Odelay Air - Moon Safari Chemical Brothers - We are the night I would have mentioned Bob Marley but the bass is weak relative to the above, which surprised me. A lot of the music i listen to doesn't have the bass content to really test diy speakers for failings. I know this forum slightly leans towards the classical side of music but i don't have any with a lot of low frequency in it. The Planets has a moment or three but they are very few and far between.
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