My latest creation is almost done. I put together a couple of pages showing the speaker and the design. Comments/critique welcome.
Helios Project pages
Helios Project pages
That looks brilliant, and it sounds like you're very pleased with the sound as well so congratulations!
I'm not experienced in reading polar response charts, but my impression is the dispersion is quite wide and smooth, with only a dip at the upper crossover region - something I wouldn't necessarily expect from the Neo8. Has that been your experience when listening? I've been considering the Neo8 for a project of my own, but have been hesitant because the tight/small sweet spot I usually associate with planar drivers doesn't match very well with my listening habits. I suppose crossing it over to a discrete tweeter helps eliminate any tendency toward beaming, but I'd be very interested in your impression after listening.
Also, any chance you might be willing to share your crossover strategy? It looks like you have your drivers aligned physically, any details you'd be willing to share would be much appreciated!
I'm not experienced in reading polar response charts, but my impression is the dispersion is quite wide and smooth, with only a dip at the upper crossover region - something I wouldn't necessarily expect from the Neo8. Has that been your experience when listening? I've been considering the Neo8 for a project of my own, but have been hesitant because the tight/small sweet spot I usually associate with planar drivers doesn't match very well with my listening habits. I suppose crossing it over to a discrete tweeter helps eliminate any tendency toward beaming, but I'd be very interested in your impression after listening.
Also, any chance you might be willing to share your crossover strategy? It looks like you have your drivers aligned physically, any details you'd be willing to share would be much appreciated!
HeatMiser said:
Thanks. Yes, you are right about the discrete tweeter. It does help with the power response. It helps the speaker sound smoother off axis. The XT25 doesn't start to beam as early as the Neo8, therefore you get a much wider physical area where most frequencies are heard. Plus a small tweeter radiates in a similar pattern to the woofer and midrange drivers.
As to the polar plots. The dip you see in the 5000Hz curve is caused by negative interference between the tweeter and midrange driver. It is normal and is called lobing. The null points to your belly when seated in the sweet spot. You would have to lower your head to notice a suck-out of upper midrange. Other than that, the plot fluctuates mostly in a 10dB window at most frequencies, which makes the speaker sound even and balanced in the room.
The drivers are not aligned perfectly. That is the reason I had to tweak the LP and HP slopes to a non textbook slope. The phase was not tracking right at all with textbook slopes.
I started with textbook 3rd order Bessel acoustic response at 700Hz and 5000Hz for the mid and went from there.
I think I will post this complete design once I'm finished. I'm in the phase of ordering parts for the crossover. Once I solder them and verify that the speaker actually measures (and sounds) the same way as the sim suggests, I'll make it available for download. Keep in mind that:
1. it is an active crossover design
2. Dynaudio drivers are not very easy to come by.
so making it is not going to be very straight forward.
Thunau -
Thanks very much for your additional comments. I realize the speaker you are building is fairly complex, and the Dynaudio is not exactly available from Parts Express 😉 , so it's not my intention to try and get enough details from you to copy your design. Rather, I'm interested in your crossover choices as a learning experience - particularly since the mid and tweeter are available at reasonable prices and are generally well-regarded, and you seem to be doing a fine job of matching them to each other.
Thanks very much for your additional comments. I realize the speaker you are building is fairly complex, and the Dynaudio is not exactly available from Parts Express 😉 , so it's not my intention to try and get enough details from you to copy your design. Rather, I'm interested in your crossover choices as a learning experience - particularly since the mid and tweeter are available at reasonable prices and are generally well-regarded, and you seem to be doing a fine job of matching them to each other.
Also I re-read my first post and realized I wasn't very clear and may have been misunderstood - it isn't the lobing at the crossover point that I found surprising, it's the overall smoothness of the power response in general. In other words, I'm impressed with the way you've created a speaker with wide, smooth dispersion using the Neo and hope that I can learn some things by following the progress of your project.
Neo8 directionality
Neo8, if you look at the polar plots posted by manufacturer, gets progressively more directional from about 7kHz. I use it up to 5kHz with 3rd order LP slope. That assures that the beaming comes mostly at frequencies reproduced by the tweeter, which is what we are all acustomed to. XT25 is not the best at dispersion, there are other tweeters, especially 3/4" models, that disperse high frequencies in much nicer fashion. My choice of that tweeter was dictated more by the low distortion figures and extended frequency response, plus the sound of it is complementary to the planar driver. I have a few tweeters on hand and this one gels with the Neo8 the best.
If you are planning on trying the Neo8, I would say go for it. It's as good a midrange driver as you'll find anywhere. Marry it with a small tweeter at 5000Hz and you got a very nice speaker.
Neo8, if you look at the polar plots posted by manufacturer, gets progressively more directional from about 7kHz. I use it up to 5kHz with 3rd order LP slope. That assures that the beaming comes mostly at frequencies reproduced by the tweeter, which is what we are all acustomed to. XT25 is not the best at dispersion, there are other tweeters, especially 3/4" models, that disperse high frequencies in much nicer fashion. My choice of that tweeter was dictated more by the low distortion figures and extended frequency response, plus the sound of it is complementary to the planar driver. I have a few tweeters on hand and this one gels with the Neo8 the best.
If you are planning on trying the Neo8, I would say go for it. It's as good a midrange driver as you'll find anywhere. Marry it with a small tweeter at 5000Hz and you got a very nice speaker.
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