Some of the problem with the Idunn is definitely the crossover, but the U18 is not an easy driver to make sound good. It has that plateau centered at 500 Hz which creates a nasty hollow sound unless it's directly addressed. In addition, there's a resonance dip at 800-900 Hz which makes vocals sound less realistic. I've played around extensively with crossover voicing and still haven't gotten it to sound totally right.
I have 2nd order electrical with an RLC in parallel with the shunt capacitor on the woofer circuit. The RLC reduces the 500Hz plateau. The problem with this is it requires large L and C values. You may be able to get a better result if you run a 2nd series inductor in parallel with a resistor. This 2nd inductor would increase the baffle step at low frequencies to provide a minima at the 500Hz peak of the driver. The parallel resistor would stop the baffle step attenuation at 600-700Hz. You really need measurements and a good sim to do this with any accuracy.
Interesting statement.
I have built the Idunn exactly to Seas' plan. Like 100% exactly. Almost everybody who has built them has a similar observation.
It is not a terrible design or so, but certainly nowhere close to the Audioexcite design (dxt + u16). This design is by far superior to the iDunn.
By the way, 'Dun' means 'Thin' in dutch ;-)
I have no doubt about the quality products of Seas. But, their business model is to sell woofers and tweeters etc, not to sell completed loudspeakers.
Greetings,
Satefan
I used to simulate Idunn strictly based on Seas official data and the simulated design with original Idunn XO filter appeared ok on the paper so I conclude that Seas probably did a pure simulation so they have something to offer to their customers but probably not optimized all the way.
For anyone knowing universal speaker design rules, it should not present too much trouble to get that last bit of performance right.
For anyone knowing universal speaker design rules, it should not present too much trouble to get that last bit of performance right.
That's exactly what i think. Its most probably a simulated filter. Such approach can greatly help to get to 80% of what can be achieved perhaps. However, i also think the U18 in itself is not as good as the U16. The base characteristics seem more favourable and allow for a much more simplistic x-over design. Matching the drivers to supplement each other is really a critical step in every design. Yes you can do a lot with cross-over design, but if you don't have to because the drivers match nicely is always better IMHO.
Satefan
Don`t forget they designed the Jamo Concert series for the then Danish company which were regarded by buyers.
Idunn looks like it was designed to be placed close to a wall, so for small to medium rooms. When you design a bookshelf, you need ot take your bet, if crossover is optimised for stands (weird solution considering for the same price you usually get the floorstanding version but some people like to use bookshelves on stands), it will sound boomy when placed near a wall or in a corner. Same if you put it on a standard bookshelf.
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I am very sure Seas knows exactly what they are doing. I really like their products. My only comment was that this specific design (iDunn) does not reflect what their products are capable of.
I think seas idunn kit is superb for the cost.
But crossover is too simplicistic by the woofer side.
It is evident also from seas graphs that the U18 has a bumpy response in the 250hz-700hz and it makes the sound "fat". I think the crossover needs some adjustement . Maybe a second inductor after the 2.2mh one bypassed by a 4.7-47 ohm resitor may help. Also the shunt to ground is bad in my advise. Could be better a LC to ground, maybe 8.2uf and 0.05mh that help a lot to correct the slope of the woofer and the bump at 2khz.
What do you think guys?
But crossover is too simplicistic by the woofer side.
It is evident also from seas graphs that the U18 has a bumpy response in the 250hz-700hz and it makes the sound "fat". I think the crossover needs some adjustement . Maybe a second inductor after the 2.2mh one bypassed by a 4.7-47 ohm resitor may help. Also the shunt to ground is bad in my advise. Could be better a LC to ground, maybe 8.2uf and 0.05mh that help a lot to correct the slope of the woofer and the bump at 2khz.
What do you think guys?
I dont know what other people has done and how they have built the kit.
But the polycone U18rnxp in a 20 liters vented box doesn't sound thin in anyway! But i placed the port on the rear of the speaker . Maybe the port in the baffle is the responsible for that. Another issue in my opinion is the damping material recommended by seas in thei kit: i have calculated the internal resonances of that box and also the thickness of damping pad for stop them. Also the acousta stuff (white polyester) is not good anyway. I used 5 cm pyramidal pads. 2 layers in the bottom, one layer on the rear and on the top. 2-3 cm acousta stuff only on the sides.
I can swear that doesnt sound thin and goes very deep for a 20L box and 6.5" driver. With environment gain i reach 30hz very smoothly. My issue is more in the 250-700hz
But the polycone U18rnxp in a 20 liters vented box doesn't sound thin in anyway! But i placed the port on the rear of the speaker . Maybe the port in the baffle is the responsible for that. Another issue in my opinion is the damping material recommended by seas in thei kit: i have calculated the internal resonances of that box and also the thickness of damping pad for stop them. Also the acousta stuff (white polyester) is not good anyway. I used 5 cm pyramidal pads. 2 layers in the bottom, one layer on the rear and on the top. 2-3 cm acousta stuff only on the sides.
I can swear that doesnt sound thin and goes very deep for a 20L box and 6.5" driver. With environment gain i reach 30hz very smoothly. My issue is more in the 250-700hz
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How did you calculate the resonanses and standing waves inside the box? Curious.
Pyramidal pads are good at splitting the soundwave but have poor ability to convert sound energy into heat and what you want inside the box is both. I would place some polyester fill over the pyramidal lining. For bass frequencies, fiberglass exhibits higher absorbtion characteristics, sheep wool is better at the midrange and high frequencies (also cotton).
Standing waves are calculated this way:
344/2/inner dimension in meters.
The calculation must be done for all the 3 dimensions.
So, for example, for an inner width of 17cm you will have :
344/2/0.17=1011 hz.
Concerning the damping material, i have tried all materials you said and found that only polyester makes the sound boomy. Only polyester is not good and you can see the peaks at the correspondant standing wave frequency with an impedance measuration. If the box is overdamped (pyramidal pads on all the sides) the bass will be dry. I found the optimum in this way. This is only my experience and i see no standing waves alterations in the impedance
344/2/inner dimension in meters.
The calculation must be done for all the 3 dimensions.
So, for example, for an inner width of 17cm you will have :
344/2/0.17=1011 hz.
Concerning the damping material, i have tried all materials you said and found that only polyester makes the sound boomy. Only polyester is not good and you can see the peaks at the correspondant standing wave frequency with an impedance measuration. If the box is overdamped (pyramidal pads on all the sides) the bass will be dry. I found the optimum in this way. This is only my experience and i see no standing waves alterations in the impedance
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