Bookshelf dipole speakers - is it possible ?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Gainphile, your latest with the 15" eminence has sent me off in a new tangent...

But what I learnt was not to skimp on Bass (with capital) and use simple baffle.

I was thinking of an OB desktop with with just Vifa A10CC-07 from Apexjr, though I'm still not sure if that's a good driver choice for OB.

If I do go down that road, should I pair it up with a 12" from Jaycar?
 
diyAudio Member
Joined 2007
The 12 inch go much lower due to a couple of factors; Fs is lower ( 32 nominal as against 40 nominal ) and Qts is higher.
Both drivers are X-max limited to 12 watts max, but that is actually quite loud, they won't rattle the walls or give explosive sound effects but they both sound good enough to recommend in this situation.
Try and find some 4 a side should work well even for me ( when I get a round to it that is ) or 1ten plus 1 12, but the midrange on the 10 inch sux

Regards
Ted
 
diyAudio Member
Joined 2007
I am beginning to think that the answer to the original question is yes but it depends on how big your bookshelf is.

Jaycar did have some 8inch paper coned woofers ( I have tried them ) if ultimate bass wasn't needed they seem to have the same resonance OB as the low string on a bass guitar some Jaycar stores still have stocks about $20 each last time I bought some, but no midrange definition so needs the extra driver and components to make 3-way
 
I am beginning to think that the answer to the original question is yes but it depends on how big your bookshelf is

I intend to use them on my desk as nearfields...space is at a premium

4 a side should work well even for me

That'd defeat the purpose, space again gets in the way

I was wondering tho, if i can get passable extension down to 200Hz in nearfield application from the Vifas, why not have a separate dipole (sub?)woofer?
 
diyAudio Member
Joined 2007
For near space you do not need the sheer volume (SPL ) so even an 8inch bass would do it.
I confess I am not familiar with that Vifa and not had time to search it.
Do you want a pair of the 8's, you can have them for the cost of postage plus $5 or come over and pick them up; they didn't sell at the garage sale you can experiment, why miss all the fun of making a dogs breakfast and having ti find out why and how to fix problems

Regards
Ted
 
Hi Moondog55,

If you don't get any interest from merajsalekj, I'll give you $30 for the pair of 8's, shipped to 2250.....are these the ones that they still sell, with a Q of 0.92, Fs of 39hz and power handling of only 30 watts, or are they a different 8" that comes from the previous range of response woofers? (to be honest, I'm more interested in them if they're not the the ones in the current catalogue....30watts is a little bit low, I want to do a small experimental active system).

If you happen to have any moderately interesting midranges too, I'll gladly make an offer.

(Background: I'm a broke student (OK, one of those words is redundant) who's never built a pair of speakers, but has mucked around enough with amplifiers and all manner of line level circuitry enough that an active OB seems like a perfectly achievable goal, given all the references that Linkwitz has given us on the topic. Oh, and my desk is too crowded already for even the smallest of dipoles, so even if I do build something that sounds fantastic, it'll be playing beautifully to a double garage)
 
diyAudio Member
Joined 2007
Yes thats them, they are not worth $30, the $5 is an honest price; I have played with the cone material and they are heavily driven, but if that is $30 including shipping thats fair.
These were in this speaker

http://farm4.static.flickr.com/3082/2684886778_ba0d885e65.jpg?v=0

OK sound if you want a 3-way crossed over low, Jaycars power handling is way too optomistic X-max limited to 12 watts so RMS 4 or 5 but near-field thats "LOUD"
E-mail me privately and I'll let you know about my spare drivers ( I need to clear my shelves of old & excess drivers ) so the price will be right
 
diyAudio Member
Joined 2007
Both dust and cone treatment, the baffle shown is 300mm with sides 100 deep.

I would say that 300 X 450 tall would do, but everything depends on every thing else as the saying goes.
There are some stocks of these drivers left in various jaycar stores but none of the 10's or 12's ( I have looked I need one more 12 )
The 8 has a lousy midrange, I'd probably use it crossed first order with as big an inductor you can afford as a low bass helper and use a good full range as the mid-woofer. Some of the old Tandy Radio Shack driver sound good, I have a pair of 8's I experimented with a while ago and they were good up to 4000, better crossed lower of course.
Where are you situated??
 
So, I spent a couple of hours mucking around with Basta!, Edge and Excel tonight.....and I plotted some nice little graphs about performance in OB for the old Jaycar 8"s.

The simulated baffle was 50cm wide and 100cm tall, with the driver 25 cm from the floor.

On this graph, the levels are normalised such that the MAXIMUM power is 1 watt. That is, the unequalised response shows the response at 1 watt, and the equalised responses show the SPL when maximum available power is 1 watt.

Not shown is the lowpass response, because it was too much effort to graph.

The raw OB response is nothing to call home about...with an appropriately placed 2nd order lowpass to counter the rising response, it has a -3dB point a bit above 50 hz.

However, while resulting in limits on output volume, this can be extended to about 27 hz using 6dB/octave from 300z. When combined with a linkwitz transform, this can reach 20hz, but at the cost of reducing output at 1 watt to just 79.5dB, which is, I'll grant, really rather low. It does make the resulting system a rather nice match to the HiVi B3S, though, and the nearly flat resulting acoustic output should be easy to crossover.

By my estimation, then, 2 per side would reach 82.5dB, the stereo pair 85.5dB, and, given a slightly optimistic power handling estimate of 8 watts RMS, a maximum output volume of 94.5dB, which is...ordinary, but not too bad, and performance ought to be better still in real life, with actual musical content <50hz generally a) transient and b) pretty quiet.
 

Attachments

  • system response.pdf
    19.8 KB · Views: 55
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.