I think in general all AMT's respond better without a rear chamber. I noticed this with the Heil as well. Just a simple block of fiberglass at the rear to attenuate to taste works for me. Seems like the diaphragms don't like the additional pressure imposed on only one side with a rear chamber. Must have to do with how they work vs a regular cone driver.
How about comparing THD and CSD with and without the felt? Freq response it not the only important thing.....
I experimented with different types of damping and density. Each changed FR somewhat and distortion in the lower frequencies was lower overall. I ended with a layer of open cell foam (9mm thick) followed with a 30mm layer of regular fiberglass.
That's great input, thank you!
I am in fact xo at 1100Hz but I believe I'm on the limit, so I'm cautious to recommend going there. But since you are at 1300Hz you might want to explore further, with caution.
I cannot speak highly enough of the TPL open back and driven from a 45-type SET amp.
Great to know you like this xo with TD8M. Still in my list!!
Can I ask you for a picture of the back of your OB? Trying to understand how you attach the TD8M/TPL panel to the vertical structure. I'm thinking about how to do mine.
StigErik,
It's great to see you around here again! At least I haven't seen you in years, but have learned A LOT from your past posts/threads.
Just to say thank you!!! 🙂
Thank you - to all of you who have given me a welcome back here. Comments like this really warms my heart!
I've been active on an other forum in my native tongue (Norway/Norwegian), but that forum, like so many Hi-Fi forums is ruined by endless threads about power cables and other absolute nonsense. I'm really glad diyAudio does not suffer from this. 👍
I have revisited a few of my own build threads here, and man... I really went crazy with some of my baffle-less designs. Some of them sounded good, or at at least I remembered them that way. I haven't completely left DIY, even though I mainly play around with modifying Magnepan speakers these days.
I'd like to publicly thank Rudolf Finke ( @Rudolf ) for all his articles and insight into baffle-less dipoles. Rudolf's work has been a true inspiration for me. (I'm also glad I can read German quite well...)
I've been active on an other forum in my native tongue (Norway/Norwegian), but that forum, like so many Hi-Fi forums is ruined by endless threads about power cables and other absolute nonsense. I'm really glad diyAudio does not suffer from this. 👍
I have revisited a few of my own build threads here, and man... I really went crazy with some of my baffle-less designs. Some of them sounded good, or at at least I remembered them that way. I haven't completely left DIY, even though I mainly play around with modifying Magnepan speakers these days.
I'd like to publicly thank Rudolf Finke ( @Rudolf ) for all his articles and insight into baffle-less dipoles. Rudolf's work has been a true inspiration for me. (I'm also glad I can read German quite well...)
Counterintuitively, I have ended up with 1.8kHz crossover on my PA speakers which sounded better to me than the lower crossover frequency expected and at which I started. No measurements to explain this, simply better subjective sound! (Beyma 10LW/30N and TPL150H plus subs).