Dipoles ?

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Jezz-the-Fezz

Jezz-the-Fezz

Member
Joined 2005
Doh!:whazzat: - that'll teach me to get my coffee before fathoming posts!

Ok; if we take the following driver (go with the red curve as being as near to a "free-air" reading as we've got):

http://www.ascendantaudio.com/archive/Avalanche%2018%20sealed%20graph.htm

using a 1 Metre radius baffle (assuming a "point source") sound velocity 344M/S; hence dipole cancellation commencing @ 344Hz. The -6dB/octave dipole effect will cause a -24dB attenuation @ 21.5Hz. A first order low pass is employed @344Hz to correct this.

At 4' listening distance, the +5dB "shelving effect" takes the 20Hz region to -4dB overall? :boggled:
 
LennyK

LennyK

Member
Joined 2002
Thanks to all of you - I'll try dipoles, for sure!!
Now I'm thinking about speakers.

opp said:

I am currently designing a dipole system using 4 Tang Band W8-740E, those 4 cost less than one Peerless XLS!
Click to expand...

Can I ask - Where did you get them ?
Do you use 4 per channel, or 4 overall ?
Do you have opportunity to compare them to SLS ?

Nemophyle said:

i assume that what's you want to know is is your choice of driver good

id say that you'd better go for the XLS or some similar driver for the bass, but that the SLS could be enough if you don't listen to music very loud.
Click to expand...

Finally someone wrote something about speakers. :D. thx !
To be honest - I really dunno hom much SPL I like... But I suspect not that much. For now I use 30 cm Vistaton speaker in transmision line, feed from 30W tube amplifier. And it's enough. More of less... :devilr:

Nemophyle said:

don't worry about the tweeter, the 27 TBCFG is 95 % as good as the millenium distortion wise. The millenium is having the ability to cross a little lower, but with the peerless nomex i assume you could cross around 1,5- 2khz so it would be ok.
Click to expand...

I think to cut the tweeter about 1,4-1,5kHz 24/oct. I searched a lot about them on the net, and everyone seem to like those Seas tweeters, especially 27TBFC... but it's so ugly.. :D

Nemophyle said:

so go for the HDS and seas, although they may be other choices for the 20cm mid driver a little less expensive and quite as good for this application.

if you can save the bits for the XLS
Click to expand...

Do you think it would be worth ? Can you give any examples ?
Problem is - that they are quite new, and there is not a lot info on the net about them.
But I suspect, that I should use them and do not make savings on the mid freq.
I hope that SLS [or something similar in terms of price] will be enough.

best regards

Lenny
 
mac

mac

Member
Joined 2003
opp[/i] I am currently designing a dipole system using 4 Tang Band W8-740E said:
Can I ask - Where did you get them ?
Do you use 4 per channel, or 4 overall ?
Do you have opportunity to compare them to SLS ?
Click to expand...
[/QUOTE]

Parts Express sells them here in the US. I built a set of dipole woofers using the "C" version of that driver (lower Fs). I used 4 of them per side. While the results were good, you might still want to consider using two of the SLS's per side. IME there is no substitute for cone area. :)

An externally hosted image should be here but it was not working when we last tested it.
 
opp

opp

Member
Joined 2005
I bought mine from Jumon-audio in Copenhagen ( www.jumon-audio.dk ), in international terms not far from Gdansk - and both inside the EU. Of course shipping cost is decisive.

Jumon is a small and flexible company, so if it is of interest, drop Jumon-audio a mail, maybe something clever regarding shipping can be worked out.

The units are not ideal for dipoles, Fs (32Hz) could be lower and the Q is low, but as my EQ is custom designed this it is not disqualifying. (> measured with SW > EQ designed with a Spice program > build on “the kitchen table”). I ended up with 18dB/oct from 150Hz!

The upside is: price (40 euro per unit), x-max and size. http://jumon-audio.dk/w8-740e.htm I use 2 per side, in a folded configuration, that’s ok for me, SPL-wise.

I will post some pictures once I get home.
 
E

exipnos

Member
Joined 2002
continuing on my quest to learn more about dipoles and HT. A common recommendation is to use dipoles for HT in the surround channels especially back and sides. I've seen that all the commercial dipoles for HT are boxed designs with 2 sets of drivers shooting in opposite directions. The placement of these dipoles are on the wall.

By doing OB dipoles we remove the box and its effect on sound. For surrounds, would placement of OB bipoles be the same as closed boxes? I imagine placing the speaker parallel to the side wall so that the front wave shoots to the front of the HT and back wave goes to the back.

Closed boxes have 2 sets of tweeters. For OB dipoles I imagine that I would have to use a tweeter where the back wave is used. That means some sort of ribbon or planar?
 
A

ALF in AUS

Member
Joined 2004
Planar type tweeters work well with OB
Ribbons are good, but might need taming.

In one incarnation of open baffles, I had a fullrange speaker mounted in a flat baffle, with an upwards facing dome tweeter as a top end help ... it took some fiddling initially, but did produce a pleasant "live" (well, "liveish") sound...

:) ALF
 
R

reins

Member
Joined 2004
LennyK said:
I think to cut the tweeter about 1,4-1,5kHz 24/oct. I searched a lot about them on the net, and everyone seem to like those Seas tweeters, especially 27TBFC... but it's so ugly.. :D
Click to expand...

I even crossed them at 1100 Hz 24/oct. But I need not so high SPL. It is really a superb tweeter and I have thrown out my Fountek Ribbons because they were a mess especially the handling.

Stephan
 
opp

opp

Member
Joined 2005
mac said:
Parts Express sells them here in the US. I built a set of dipole woofers using the "C" version of that driver (lower Fs). I used 4 of them per side. While the results were good, you might still want to consider using two of the SLS's per side. IME there is no substitute for cone area. :)
Click to expand...



Cone area is vital, but can't it be substituted by excursion in your opinion, mac? - in theory it can.:confused:

I'm not familiar with the SLS, but they are probably better quality drivers than Tang Band. But very important for me is size and price. So far I’m very happy with the prototype.

Pictures of my Tang Band Dipole prototypes. No comment on the woodwork pleas:nod: – they are only prototypes.

They measure:
Total height 85 cm. (33 inch)
Bas enclosure height 60 cm. (24 inch)
Width 29 cm. (11 inch)
Depth 36 cm. (14 inch)

Billede003.jpg


Billede002.jpg


Billede001.jpg
 
LennyK

LennyK

Member
Joined 2002
so many options...

... so litle money to spent :D

Anyone used L22RN4X/P [H1208] in dipole ?

About bass drivers I made comparsion. And now look:

1. Tnag Band driver - cheap, but low displacement [not that cheap spl/price wize]
2. SLS 12" in terms cost of cm^3 - real bargain
3. [X]XLS 12" family - big cost - lot of displacement

Now look:

First of all SLS is hard to beat in terms of price. One cubic cm costs about 0,1 Euro.

Then Tang-Bang - if I would like to but 4 speakers [2 per side] - we have displacement 532,4cm^3 [per side]. It's not more than 559,2 cubic cm from one XLS12. One XLS is only 20 Euro more expensive.

So I think about two options:
1. one XLS per side - if it would be not enough [in dipole] - I'll try sealed.
2. two SLS in diploe.

Maybe you have some other drivers in mind ? - I'd love to put them to my Excel.

best regards

L.
 

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opp

opp

Member
Joined 2005
Indeed a convincing excel :cool: . The price on the SLS is very favourable; I would have to pay 200 euro in Denmark for 2 SLS (Home of Peerless :headbash: ).


Large excursion is in IMO the only factor that can reduce the size of the total system (= raise WAF).



AJinFLA said:
Hi Opp,

I'm sure what Mac meant is that since swept volume is the key to dipole bass, cone area is as vital as xmax, since area x xmax = volume displaced.
What midrange are you using? Looking good so far;) .

Cheers,

AJ
Click to expand...



AJ - I am aware of that air displacement capability is = (cone area) X (x-max) :), but what I intended to asked mac about is, if large excursion is a disadvantages in terms of distortion, e.g. due to compression of air or deformation of cone/surround.

The midrange is special OME version of Vifa PL14, it reproduces voices with a nice depth frequency wise, IMO voices is often reproduced to bright (confusing brightness with clarity). The integration to the XT25 is not satisfactory at the moment.
 
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