Dipoles ?

[ALF in AUS]

It all starts to sound the same after a while, but what the guys above have said sound mostly pretty right to me ... I'd been fussing over enclosures for years - box after box - sealed, BR, TL, voigt pipes, back horns ... Then I built (and here "built" is a relative term) a pair of open baffles - 600 X 1000 mm with 300 mm wings on the sides, with a three way driver configuration, and I couldn't believe it - they sounded so REAL .
Now I am running a 15" bass driver and a Visaton full range (with active Xover and bi amp) in an OB that is simply a sheet of mdf with holes in it ... I still have my horns in my office, but for my main listening I can't see me ever going back to boxes ... this open sound is so good!
I don't think you can go wrong with the Linkwitz speakers, and by all accounts the NaOs are pretty amazing too.
Good luck ... keep us posted!
ALF in AUS

[ScottG]

Originally posted by PHilgeman
Hmmm...

Having built several dipoles, I have come to the conclusion that cardioid, or sealed box bass has the edge on diple bass.

It really requires tremendous ammounts of EQ to get it right and in a good room, equally flat response can be had with sealed.

The midrange however is where the magic is, especially 150Hz-1000Hz. The lack of 'boxyness' and the problmatic transition from 2pi radiation to 4pi radiation is where the magic happens IMO.

-Paul

Yup..

It really has little if anything to do with the radiation, rather its about:

1. resonances
2. resistance
3. compression

1&2 principally corespond with bad sound from 300 Hz up. All 3 however are important from the bass region up to 300 Hz.

There are some generalities however that can be "usefully" attached to the bass-300 Hz range:
1. the lower in freq. you go the less important resistance becomes (i.e. acoustic resistance from fiber fill)
2.the lower in freq. you go the more acoustic compression is usually DESIRED, and it can be advantageous at a lower sp level (than reference - i.e. flat on axis) up through to 300 Hz. For instance a driver that operates in dipole between 60 Hz and 300 Hz at reference level (or slightly less than reference level due to summing), can actually be improved upon by using a secondary driver (in perhaps an acoustic suspension) that covers most of this bandwidth (say up to 100 Hz) but at a lower level (say 6-9 db less). This subjectivly adds back a degree of "punch" that is missing via the dipole approach while minimizing the "forward" "bunched-up" imaging that results from acoustic compression.

[LennyK]

Originally posted by ScottG

This subjectivly adds back a degree of "punch" that is missing via the dipole approach...

Scott - do you say, that dipole designs, like Orion for example, lack bass punch ?

I like punches [in terms of bass of corse ].

L.

[Rudolf]

Originally posted by LennyK
do you say, that dipole designs, like Orion for example, lack bass punch?

I haven´t heard Orions, but my own dipoles definitely don´t "punch" as much as most monopole designs. Which I see as an advantage, since "kick bass" in typical rooms seems to be enforced by excitation of room modes in the region from 80-120 Hz. This is a feature dipoles commonly "lack".

That´s IMHO. Would be nice if someone could explain exactly where the "punching" difference between monopoles and dipoles stems from.

Rudolf

[Scottmoose]

The room, as you mention. Depends on the room of course, which is why I despise rooms as a pain in the neck, and try to circumvent their influence whenver possible. Most likely a horizontal mode, though in some cases the vertical mode will also come into play, especially if the speakers are near corners.

Below 40Hz dipoles are impractical, so I'd shift to bipolar operation for the subs, which also tend to energise less room-modes than monoples. That 'punch' might be subjectively impressive, but don't forget that it's rarely on the recording. Fair enough if you like it, but remember it's not accurate. Most rock is already tickled up in that range anyway during the mixing.

Beware the assumption of flat responses. It's very easy to get a flat response from both dipoles and monopoles -in an anechoic chamber. The principle advantage of dipolar bass down to 40Hz or so is that it excites far fewer room modes, with the result that you hear your drive-units more, and much less of the room. This is generally a good thing -rooms are far harder to predict, especially at low frequencies, than drive-units, which will almost invariably be better behaved.

[reins]

Originally posted by Scottmoose
s.

Below 40Hz dipoles are impractical, so I'd shift to bipolar operation for the subs, which also tend to energise less room-modes than monoples. That 'punch' might be subjectively impressive, but don't forget that it's rarely on the recording. Fair enough if you like it, but remember it's not accurate. Most rock is already tickled up in that range anyway during the mixing.

[/B]

I have no Problem to get flat response down to 25Hz with my 15" Lambda driver

I believe that many people think punch is equal to BOOOOOM. I don't miss the BOOOOM

Stephan

[kneadle]

"Punch" in DIY speaker circles has become the "ballsy" of guitar pickup circles. It has no meaning at all.

Dave

[Rudolf]

Originally posted by reins
I have no Problem to get flat response down to 25Hz with my 15" Lambda driver
Stephan

In the light of J.Ks examinations regarding dipole response
http://www.musicanddesign.com/roomgain2.html
would you mind stating your room dimensions and fr of the Lambda?
I´m curious to see John´s findings verified in real life.

Thanks
Rudolf

[reins]

Originally posted by Rudolf


In the light of J.Ks examinations regarding dipole response
http://www.musicanddesign.com/roomgain2.html
would you mind stating your room dimensions and fr of the Lambda?
I´m curious to see John´s findings verified in real life.

Thanks
Rudolf

The article describes exactly the behavior in my room:
Room dimensions are 6m x 4m x 2m and below 25Hz is not much response left. I observed the rise in response around 30Hz too. Fs of the driver is around 20Hz.

Stephan

[Rudolf]

Originally posted by reins
The article describes exactly the behavior in my room

Nice to know, thanks.
My room´s size is just between the two simulated by John (except height) and my dipoles follow his results quite well too.

Rudolf