Subwoofer using B200's

[spikey]

Hi,

I have a couple of Kef B200's, ex Monitor Audio MA5's, and was wondering if I could put them to use in a subwoofer. Please excuse my lack of knowledge if this is a stupid thing to ask, but is this realistic, and does anybodu have any experience of this, and could perhaps suggest suitable designs?

Thanks
Stuart

[AndrewT]

Hi,
which version of the B200 was fitted to the 5?

Some data for your drivers would help. I think there are 3 or 4 versions on this forum.

[AKN]

Hi spikey,

Not much x-max on those Kef but good parameters otherwise.
There are several iterations of this woofer B-200-A,B,G etc, which is yours?

With several units in a large box total displacement can be good anyway.
How many units do you have? Can you tolerate a large box?

[spikey]

They're SP1014s, and I have 2 of them. I wouldn't be looking for lots of power, but I would like a clean sound if that helps.

[AndrewT]

Hi,
http://homepage.mac.com/planet10/TLS...200_SP1014.gif found in http://www.diyaudio.com/forums/showt...ht=#post731448
That 10Vrms for 96db is ~=85db/2.83Vac@1m.
Xpp=6mm is Xmax=3mm.
Q=.51 suggests sealed box.

Don't apply any Linkwitz transform nor similar EQ to extend the low bass, you'll run out of travel at very low volumes.

I did a search on sp1014 and found five other threads.

[spikey]

Thanks Andrew T.

This is all new to me, and I don't yet fully appreciate what those specs mean. Are you saying that I wouldn't be able to get much deep bass out of these drivers, and therefore that they aren't the most suitable to use?

[AndrewT]

Hi,
input the driver data into a sealed box modelling program and look at what Q you end up with for different sized boxes.

For lowish bass you need a big box, roughly equal to Vas in volume. This will not go loud but it might sound nice if you can disguise it as a coffee table or TV stand.

You could try diysubwoofers.org and use their sealed box model. and read the two sets of design notes (general+sealed).

[spikey]

Thanks for being so helpful Andrew.

Now I've got somewhere to start! The Subwoofer DIY page looks useful.

Cheers

[spikey]

So.....

Well I've done the numbers, and it's clear that to get a decent response from these drivers in a sealed box the enclosure size could lead to domestic difficulties. Looks like I'll knock that idea on the head and have a rethink - still that's something I've learnt today.

[bjorno]

Hi spikey,

Andrew T wrote:

For lowish bass you need a big box, roughly equal to Vas in volume.

Agree and suggest that if you include the effect of box enlargement from the stuffing, its possible to use about 15% less, e.g. if Qtc = 0.707 is the goal for B200 then the volume should be about 142.6 L - 15% = 121.2L + bracing volume = 124 L.

I dug up a TL I have made near a dozen of (1970-1980) since B200 could be purchased.

It may be used as a closed box or TL and if used as a sub lower than about 120 Hz, you can place the driver/port almost anywhere on the baffle.

b

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