Full range cardioid

[speaker dave]

Originally Posted by Koen K

That's better

Adding a delay should be effective over a wide range. I'd also expect a hypercardioid to be pretty effective at reducing irregularities in room.

Good job!

The way to think of it is to picture your speaker array in front of a large mirror. If you stand well in front of the actual speaker the array behind will be in line and the time delay between the monopole and dipole will be simply the time of flight of the physical distance between them.

Now if you walk to the side such that you are at a 30 degree angle relative to the speaker, you will also be about 30 degrees relative to the reflected monopole/dipole elements. This will contract their effective spacing so that you can still get full cancelation, but only if you adjust the time delay for the contracted spacing (cos30 = .866).

You should still get a broad (frequency) band null at the 30 degrees (from 180 straight back) and also 30 degrees on the other side, i.e. a hypercardioid pattern.

[Jag768]

Originally Posted by speaker dave

The way to think of it is to picture your speaker array in front of a large mirror. If you stand well in front of the actual speaker the array behind will be in line and the time delay between the monopole and dipole will be simply the time of flight of the physical distance between them.

Now if you walk to the side such that you are at a 30 degree angle relative to the speaker, you will also be about 30 degrees relative to the reflected monopole/dipole elements. This will contract their effective spacing so that you can still get full cancelation, but only if you adjust the time delay for the contracted spacing (cos30 = .866).

You should still get a broad (frequency) band null at the 30 degrees (from 180 straight back) and also 30 degrees on the other side, i.e. a hypercardioid pattern.

I spend some time thinking about your explanation but im afraid i still do not fully understand it yet :P. The dipole and monopole are physically in line in my proto sub.

My approach to a hypercardioid would be to increase the gain of the dipole elemenet, which would result in a small lobe at the rear and a null to the rear sides, the angle depending on the difference in gain. Or am i missing something ?

[Jag768]

Today i spent the whole optimizing the damping in the damped u frame of the woofer. Nasty business. Took me hours to get it as good as it was before. Dog didn't help . I actually used ground plane measurements rather than the speaker lifted 2m of the ground as the picture shows. At the end of the day i got one of the speakers right, but can't get the other one to match it . I tried to match the damping material as closely as possible, but still there were clear differences.

[Jag768]

Ok, time for some more measurements. I have spent some days with only the subwoofers in my home (two Hypex amps are rma, so i cant use top cabs yet). Reasonably pleased with them. Today i put them to the test.

I made a comparison between different combinations of monopole and dipole, yielding different radiation patters. Subwoofers were positioned close to rear wall. Room is 6 x 4.2 meters, see attached picture (room is a bit longer than you can see here). Response was measured at listening position just before facing the opposite wall (3.5meters away), no gating and 1/6th octave smoothing. Results are quite close, no radiation pattern has the clear advantage to me. Cardioid seems to be able to pressurize the room as evidenced by rising respons towards 20Hz, as can be expected since it features a pressure source as well.

Not very pleased with the results, i tried measuring at multiple positions using both supercardioid and monopole radiation. I wile save you all off these images, but there was no clear winner here. Although the supercardioid seemed to be at a slight advantage showing slightly less variable freq response throughout the room (4 positions).

I suspected that the contribution of the dipole might be limited because of the proximity to the back wall. Although it shouldn't matter, since the netto contribution of the rear side should be 0 because opposing output of monopole and dipole woofers. The distance didn't change much, only with increasing distance a null appeared around 75Hz. Im not sure what this signifies.

Finally i tested the effect of a different angle for the dipole. Exciting the room modes in the perpendicular direction might yield a more even response. For both the right and left speaker, the respons got more even when more toe out or toe in was applied. The optimum was radiation to the sides for the dipoles for both speakers and this seems to work quite well for a single subwoofer. However, the summation of two subwoofers facing outward or inward is not optimal (but much better than both subs facing left or right).

It seems combining a single monopole and dipole combination can yield quite an even reponse, in my case by turning the dipole woofer 90degrees. However, im not sure what the best way of combining two of these subwoofers is. And whether this outperforms a multi mono sub setup, remains to be seen. It could well be mostly a waste of energy :P.

[gainphile]

Impressive project !!

[Jag768]

Thank you! Really great to hear from someone whose projects I read so much about . What do you think of the results? Do you have suggestions?

[gainphile]

Unfortunately no . I have zero experience with Cardioid designs.

I am closely monitoring few threads here to do some education. So THANKS a lot that you post your project. I have something in mind to build but that will need to wait until this FREEZING weather pass

Hope to compare notes by november... that's our SUMMER

[Jag768]

In the meanwhile i have built a new center speaker, also using a damped u frame to achieve a cardioid polar for midbass frequencies. The results is not perfect yet, presumably because the enclosure wasn't sealed properly by the baffle.

Currently im working on the front speakers plus extra sub. In total it wil be:
front speakers: 10"woofer + 10"waveguide
sub: multisub using 2 single10"sealed + 1 dual10"sealed + 1 15"sealed (4 subs total)
center: 2x6.5" + tractrix hf horn

Its a good thing i have an understanding girldfriend

[Jag768]

Some new progress, completed building the front speakers, sub and center. Next is working on the finish, applying absorption materials for cardiod polar and filter design.

Oh, and optimizing the multisub in my room, that we'll be a laborious process

[gainphile]

That's a lot of speaker . Love it.

Have you checked out Dutch&Dutch cardioid video on Facebook? Quite impressive
https://www.facebook.com/dutchanddutch