Having had a pair of 12P80nds gathering dust for the last 6 years - i have been pondering do i use them or sell them. I saw this speaker over the weekend which got me thinking
https://www.abacus-electronics.de/produkte/aktivlautsprecher/oscara/oscara-212.html. I have a pair of TPLs , the 12P80nds and some seas subwoofer drivers all spare that could be used. The challenge with AMTs has been integrating them with other drivers. The 12P80nd was meant to be a good match, but i didn't like it when i tried them in a simple box a while back. So could the answer be trying a different box....... I know some will shout out dipole, however if you use the TPL's open baffle, they are bipole not dipole and you get some horrible interactions, from my experience mixing dipole and bipole.. So i was thinking monopole upto a 1000hz and then bipole or hornloaded TPL's above that with higher DI, if needed
So how to best use the 12P80nd... well i was thinking a terminated transmission line - so will effectively get a infinite baffle response. I modelled a logarithmic spiral as a first pass, not the most efficient use of cabinet space. Am i right in assuming that as the driver will only be covering frequency's up to 1.5k smoothing out features smaller than a wave length wont add much. I have the CNC so can make what ever shape of transmission path i like.
To manage the beaming of the 12" drivers i was thinking of trying something like this first to see if it works that well I have some 12mm Perspex to make a test waveguide.
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https://www.abacus-electronics.de/produkte/aktivlautsprecher/oscara/oscara-212.html. I have a pair of TPLs , the 12P80nds and some seas subwoofer drivers all spare that could be used. The challenge with AMTs has been integrating them with other drivers. The 12P80nd was meant to be a good match, but i didn't like it when i tried them in a simple box a while back. So could the answer be trying a different box....... I know some will shout out dipole, however if you use the TPL's open baffle, they are bipole not dipole and you get some horrible interactions, from my experience mixing dipole and bipole.. So i was thinking monopole upto a 1000hz and then bipole or hornloaded TPL's above that with higher DI, if needed
So how to best use the 12P80nd... well i was thinking a terminated transmission line - so will effectively get a infinite baffle response. I modelled a logarithmic spiral as a first pass, not the most efficient use of cabinet space. Am i right in assuming that as the driver will only be covering frequency's up to 1.5k smoothing out features smaller than a wave length wont add much. I have the CNC so can make what ever shape of transmission path i like.
To manage the beaming of the 12" drivers i was thinking of trying something like this first to see if it works that well I have some 12mm Perspex to make a test waveguide.
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Get rid of the TPLs they are not the last thing when it comes to detail and air. You will do a lot better with a decent Compression Driver like the Faital HF108R
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Put an 18 under them and use them as midranges.
Basic? math Q, assuming parallel sides it's a parabolic flare factor, so what would its flare frequency be based on the log spiral or is there none?
I should have mention that they will be run actively, so would be adding some contouring at the bottom end to get a crossover to the subs around 80 hz. Currently do similar with Supravox 400’s in a sealed cabinet.
Not sure I understand the question, using a 1/2 wave transmission line to absorb the back wave. Was planning parallel sides. I haven’t worked out how to model it in MK’s spreadsheets yet. The big question I suppose is it going to improve the drivers properties. I may make a dagger shaped rear box to test the concept before investing time in doing the cabinets properly.
Subscribed.
What will you be comparing these to? Currently using TPLs, with what midrange driver/setup?
What will you be comparing these to? Currently using TPLs, with what midrange driver/setup?
Again, know nothing about spiral design, but spiral or straight, terminated to a point or not, it can have a horn flare frequency (how I design TLs), so curious if from a math POV does log expansion or even golden ratio/whatever correlate to flare frequencies or just factors (expo, etc.)?
Is it the original 12p80nd you have? i seem to remember, and your picture linked kinda confirms its the V2.0.
Some links to different version/variations and discussions from here.
Terminated TL, Max flat impedance (open )TL, Closed box, Reflex,EBS, Aperiodic etc.
As for how to use it, a Large format midrange/voice range driver, with limited excursion/ IMD desireable.
Crosse over to large format woofers single 18, double 15 or similar.
As you can see from the plots in next post going much below 100hz is likely not desireable.
https://www.diyaudio.com/community/threads/beyma-12p80nd-tpl-150.231551/page-20
https://www.diyaudio.com/community/threads/hf10ak-12p80nd-custom-wg.360973/
https://www.diyaudio.com/community/threads/active-tpl-150h-and-12p80nd-v2-project.286060/
https://www.diyaudio.com/community/threads/terminated-transmission-line-for-midbass.277461/
Some links to different version/variations and discussions from here.
Terminated TL, Max flat impedance (open )TL, Closed box, Reflex,EBS, Aperiodic etc.
As for how to use it, a Large format midrange/voice range driver, with limited excursion/ IMD desireable.
Crosse over to large format woofers single 18, double 15 or similar.
As you can see from the plots in next post going much below 100hz is likely not desireable.
https://www.diyaudio.com/community/threads/beyma-12p80nd-tpl-150.231551/page-20
https://www.diyaudio.com/community/threads/hf10ak-12p80nd-custom-wg.360973/
https://www.diyaudio.com/community/threads/active-tpl-150h-and-12p80nd-v2-project.286060/
https://www.diyaudio.com/community/threads/terminated-transmission-line-for-midbass.277461/
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The realistic in me says sell it, for multiple reasons. The hobbyist says spend some time on thinking what to do about it and then do nothing 😎
But yeah, the results will be kind of mediocre if you make a project from some drivers laying around. Even if you managed to come up decent speaker it wouldn't sell much more than what you'd get from the drivers so its time wasted* if you are not going to keep them and enjoy them. If you don't have any speakers and quality doesn't have to be top of the pops and you don't mind about extra pocket money you could spend on proper project designed for your application reaching better end results then yeah, build it!🙂
The realist in me would come up with a plan for good speaker tailor fit for my application assuming ideal drivers. Then when the plan is ready I'd buy best drivers I can afford that are suitable for the plan. Might be 12p80nd or TPL or something else. If something else just sell the stuff you don't have any use for and buy the ones you actually need.
* you could spend the time for a project you want to keep and enjoy for rest of your life (or apartment) instead. Time spent with a hobby having fun is never wasted though, so do what ever feels good and fun 🙂
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Thanks for the links to all the existing threads.... some are from when i originally was looking at using the Beyma drivers. Its interesting how the posts from Linesource suggest with a parabolic taper to absorb the backwave it doesnt need to be as long as i was assuming. I was assuming terminated at both ends the lenght would need to be 1/2 wave.
I have spent a few hours today getting frustrated with software i thought i had. My mathcad licence doesnt work with the softwares latest version, i had saved the MK worksheets off my old laptop before it died. The leonard audio software doesnt work either. Wish i had kept an old XP machine. So i tried modelling the lograthimc line in Hornresp - it looked horrendous, but dont see how to account for the stuffing.
Last time i downloaded Leonard Audio Transmission line program, i had to dig the file up, on archive.org to make it work. The publicly available one that pops up on google searches i had no luck with. Have not tried it on Win 11 though if that is what you have.
https://web.archive.org/web/20170506211617/http://leonardaudio.co.uk/transmission-line/download/
https://web.archive.org/web/20161204124932/http://www.leonardaudio.co.uk/software/setup.exe
Bug fix list for all versions
https://web.archive.org/web/20170516170631/http://leonardaudio.co.uk/
Latest user manual v. 3.6.3.4
https://web.archive.org/web/2016120...k/wp-content/uploads/2013/12/TL-UserGuide.pdf
I know when they are from, you even have participated in some of them, still is the best collection of threads concerning alternate enclosures for the 12p80nd, as far as i know. I have the same drivers (V2.0) lying in the basement.
And yes tapering the line has a nice beneficial side effect, taper ratios of 10:1 or similar is popular due to that fact.
The 12p80s main issue partnered with the TPL from my POV , the horn forces it to cross over higher then ideal, if you wish to match directivity at xo.
So you suffer in coherency and vertical dispersion, pushing the xo upwards with a large CTC distance. Being large AMTs the vertical is already compromised by it's design.
There is also a objectionable resonance for some at 1,6k which is in the desired XO region.
IMO a TPL with backchamber modification, and possibly the lens that was posted here, attention to diaphragm etc.
Will let it play clean down to 1200, but that requires a new Horn/WG for a good directivity match to the cone below.
So a different beast altogether, and time consuming/expensive.
https://web.archive.org/web/20170506211617/http://leonardaudio.co.uk/transmission-line/download/
https://web.archive.org/web/20161204124932/http://www.leonardaudio.co.uk/software/setup.exe
Bug fix list for all versions
https://web.archive.org/web/20170516170631/http://leonardaudio.co.uk/
Latest user manual v. 3.6.3.4
https://web.archive.org/web/2016120...k/wp-content/uploads/2013/12/TL-UserGuide.pdf
👍
I know when they are from, you even have participated in some of them, still is the best collection of threads concerning alternate enclosures for the 12p80nd, as far as i know. I have the same drivers (V2.0) lying in the basement.
And yes tapering the line has a nice beneficial side effect, taper ratios of 10:1 or similar is popular due to that fact.
The 12p80s main issue partnered with the TPL from my POV , the horn forces it to cross over higher then ideal, if you wish to match directivity at xo.
So you suffer in coherency and vertical dispersion, pushing the xo upwards with a large CTC distance. Being large AMTs the vertical is already compromised by it's design.
There is also a objectionable resonance for some at 1,6k which is in the desired XO region.
IMO a TPL with backchamber modification, and possibly the lens that was posted here, attention to diaphragm etc.
Will let it play clean down to 1200, but that requires a new Horn/WG for a good directivity match to the cone below.
So a different beast altogether, and time consuming/expensive.
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