Good evening
I purchased a pair of KEF B200 SP1039 drivers a while ago to repair a pair of KEF 104ab speakers, and now have a single spare functioning driver. I would like to use this to make a 2-way speaker for use in the garden for a (not so wild) summer party, and then use it in my 7x4m log cabin workshop/home office (with a basic solid state class AB amp). As a result, there are no WAF limits!
I was going to ask for suggestions for a tweeter to accompany the SP1039, but my first stumbling block is the enclosure. The data sheet for the SP1039 indicates typical enclosure volumes of 20-25 litres for a closed box, and 30-40 litres for a reflex cabinet. However, playing with online calculators suggests a need for larger volumes. I presume I am making a basic error, but I can't fathom it, so any pointers would be appreciated.
I used this site https://www.diyaudioandvideo.com/Calculator/SpeakerBoxEnclosure/
If I enter the data sheet values (Vas 130 litres, Fs 25 Hz, Qtotal 0.45) and a system Q of 0.707, I get given a volume of 88.5 litres for a sealed box.
If I enter the effective diameter of the driver (about 16cm) and calculate a ported box, the suggestion is 186 litres.
Clearly these are way off what the data sheet suggest. So, please someone put me out of my misery, where am I going wrong?
Thanks for any help.
I purchased a pair of KEF B200 SP1039 drivers a while ago to repair a pair of KEF 104ab speakers, and now have a single spare functioning driver. I would like to use this to make a 2-way speaker for use in the garden for a (not so wild) summer party, and then use it in my 7x4m log cabin workshop/home office (with a basic solid state class AB amp). As a result, there are no WAF limits!
I was going to ask for suggestions for a tweeter to accompany the SP1039, but my first stumbling block is the enclosure. The data sheet for the SP1039 indicates typical enclosure volumes of 20-25 litres for a closed box, and 30-40 litres for a reflex cabinet. However, playing with online calculators suggests a need for larger volumes. I presume I am making a basic error, but I can't fathom it, so any pointers would be appreciated.
I used this site https://www.diyaudioandvideo.com/Calculator/SpeakerBoxEnclosure/
If I enter the data sheet values (Vas 130 litres, Fs 25 Hz, Qtotal 0.45) and a system Q of 0.707, I get given a volume of 88.5 litres for a sealed box.
If I enter the effective diameter of the driver (about 16cm) and calculate a ported box, the suggestion is 186 litres.
Clearly these are way off what the data sheet suggest. So, please someone put me out of my misery, where am I going wrong?
Thanks for any help.
Attachments
For a vented enclosure using D B. Keele's ammendments* for typical losses, I calculate that 123 litres of internal volume suits the published T & S parameters supplied by KEF. * Vb = Vas/1.06
Go for a higher Qtc of 1.1 and you'll get a sealed box volume of 26 litres.
You can engineer for a Qtc that is beween 0.7 and about 1.0 or slightly greater.
A Qtc of 1.1 will give you slightly accentuated bass - good if you like rock music!
You can engineer for a Qtc that is beween 0.7 and about 1.0 or slightly greater.
A Qtc of 1.1 will give you slightly accentuated bass - good if you like rock music!
Pretty much what the Data sheet shoots for and recommends 20 to 25 liters
Qtc around 1 to 1.1
Seems to be around 8" speaker
Directionality be around the usual 1800 to 2000 Hz
So for a 2 way I would put it on a relatively wide baffle
And would need a large tweeter with 700 to 1000 Hz Fs
So 1" minimum or 1 1/8"
Highpass at 2000 Hz with 3rd or 4th order
And to get clean easy summing just use 4th order linkwitz
Qtc around 1 to 1.1
Seems to be around 8" speaker
Directionality be around the usual 1800 to 2000 Hz
So for a 2 way I would put it on a relatively wide baffle
And would need a large tweeter with 700 to 1000 Hz Fs
So 1" minimum or 1 1/8"
Highpass at 2000 Hz with 3rd or 4th order
And to get clean easy summing just use 4th order linkwitz
So, going well, and one week til the garden party of the year.
Cabinet cut from leftover 18mm marine ply, partly put together with glue and pocket screws. I've routed a rebate for the tweeter (Scanspeak 92200) using a simple jig to do circles and it fits nicely. i've done the same for the SP1039 woofer but it's a funny shape so need to add the 'corners' for it. Any simple way of achieving a good match to these corners? I don't have and can't find locally a top bearing router bit, which might have helped. Is it a case of doing this by eye?
Cabinet cut from leftover 18mm marine ply, partly put together with glue and pocket screws. I've routed a rebate for the tweeter (Scanspeak 92200) using a simple jig to do circles and it fits nicely. i've done the same for the SP1039 woofer but it's a funny shape so need to add the 'corners' for it. Any simple way of achieving a good match to these corners? I don't have and can't find locally a top bearing router bit, which might have helped. Is it a case of doing this by eye?
So, you have already made a circular hole and rebate for the SP 1039 and want to add the 'corner extensions'?
I can only give your query a bump!
I can only give your query a bump!
Galu, thank you. I have routed a circular rebate, but the baffle is still otherwise intact, no hole yet. Yes, just looking to extend the rebate into those corner extensions neatly using my handheld plunge router. I think the proper way would involve a router bit with a top bearing and use of a template, but I haven't been able to get one that fits my router. Just wondering if there is some trick / jig I might be missing.
I can only refer you to this thread: https://www.diyaudio.com/community/threads/quadral-ribbon-tweeter-923-112.339642/#post-5844902
See post #5.
Maybe you can make some sense of it, it's not my area of expertise!
See post #5.
Maybe you can make some sense of it, it's not my area of expertise!
33 litres. My ply offcut was 38cm wide, so I went with that for the baffle width, and half that for the depth. 0.6 m high was as big as I could go with what I had. Qtc=1 at this volume so it worked out well.
I somewhat randomly plumped for a 3rd order crossover crossed at 2500Hz from recollection. Have a selection of different 10W resistors to play around with different L pads. Haven't tried to flatten the impedance of either driver. Maybe I'll get away with this. Just want to get it playing initially! Will throw this together tomorrow hopefully.
I somewhat randomly plumped for a 3rd order crossover crossed at 2500Hz from recollection. Have a selection of different 10W resistors to play around with different L pads. Haven't tried to flatten the impedance of either driver. Maybe I'll get away with this. Just want to get it playing initially! Will throw this together tomorrow hopefully.
Too late!
Anyway, the speaker is initially for outdoor use so perhaps the sound will integrate in the far field. 😀
Anyway, the speaker is initially for outdoor use so perhaps the sound will integrate in the far field. 😀
Damn it! I core drilled out the hole for the tweeter, so I could re plug it, bit of wood filler, perhaps glue an oversize piece internally for some bracing, and a nice paint job to cover up the mess! 😂. If so do, is it worth also moving to the 11 o'clock position, as I read somewhere could be of some benefit?
Thank you!
Thank you!
Ply wedged in across the rear of the baffle and secured with screws at the tweeter rebate. Core screwed to ply. Bit of filler and Bob's your Uncle!