ROOSKIE
Major Contributor
Yup that big 1st resonance wave is trying wrap itself around that box from the rear.The port resonance can act as a cancelation to the rear wave as it is rear ported, thus causing a cardioid high Q effect at that frequency
A front port can also cause cancelations. All port placements can cause either a peak, null, both or ideally neither.
This port has such a low untamed1st resonance that it is hitting the system hard.
If this must have a long port to meet response goals, then Purifi can try moving the inlet around in box and find a spot where the resonace is in more of a null state. They can also try placing the outlet on the bottom, top, side(s), front. Any of these option can affect the response in a way meaningful to a SOTA type project.
Again this is a reason to really invest in the port design, right now it just seems tuned for the box tuning without addressing the additional issues a state of the art design would ideally address. It is more like a port I designed and built vs a very experienced engineer. Not the end of the world but under the microscope it is not possitive.
It would always be great to get a Kipple test for a Helios DIY, but I fear that design is not in the Q.However, those who value optimal directivity should wait until angular frequency response measurements are available for the kit before buying.
Due to the fact that the crossover frequency is at 1.3 kHz, there should still be significant influences of edge diffraction on the tweeter despite the waveguide.
The designer is well known and respected and known to be extremely thorough.
That said a test is test and that is what counts here. He did public some basic off axis measurements though I do not know how much smoothing was applied here. o,22,45 degrees. What is shown here is exceptional - again not near complete as a full Polar or Kipple test.
With the low X-Over frequency are you saying that the smallish/medium sized waveguide on a semi-wide baffle can no longer responsibly direct the sound and the waveguide has given up it's primary influence to front baffle?
I ask why the 1300hrz crossover is suspicious for the waveguided tweet in the Helios example as I am actually designing a DIY active using a similar design of my own. In my case I would be willing to place the tweeter in a separate box sitting on top on the woofer box. This is both for the ability to mix and match drivers easily and to optimize the case size for each driver.
Yes, at this point it is hard to say how much more I have spent on audio due to DIY.Not a pot shot at all. I meant it. The MODDERS and DIY crowd like to build themselves and they enjoy that and buy tools and all sorts of stuff for the tasks. I've been a DIY MODDER in the past and it's fun.
Sometimes I wish a could just buy a set of the JBL 708p's a couple subs and be done.... nah! Really this is the only fun thing I do that regularly cost me $, most of my other loves are very inexpensive or free activities - which is good as I am deff not flush in $USD or BTC or Gamestop or whatever. (I am rich in enjoyment )