I did see these and concluded the purifi ptt10 were better ignoring the price difference.
If you consider breakup of the ptt8 to be around 4k what do you think the breakup of the ptt10 is?
yes it would move less due to its higher Sd. however, the 10” has a longer linear stroke with a super flat Bl(x) and Sd(x). Other distortion mechanisms will dominate. since the excursion when cut at 120Hz is generally low. The PTT10” has extremely low distortion.
Group delay: depends solely on the bass alignment and EQ. since you cut at 120Hz and these drivers go much deeper then group delay is essentially zero and if not you can add EQ to take it out. Transient response is just the mirror of the frequency response and if you EQ to flat then transient response is perfect.
In theory, a 15" at 1.2kHz will be -6db down at 90 degree's, I don't see any problems with that crossing to a matching horn. Even better, crossing lower is possible in home environment. If one need it or not, it's up to the user!
But look at this thread, it doesn't seem to be an issue?
https://www.diyaudio.com/community/threads/asathor-a-jbl-4367-clone.367215/
Anyway, this thread is going in all directions...
So if two different woofers a 10" and a 15" both have a flat frequency response, your saying they have the same transiant response... I thought it was more complex then that.
yes, that’s down to the fundamental math: time and frequency domain are linked through the Fourier transform. if you change one the other domain has to follow
To help me make a decision can someone tell me where the hf breakup is of the purifi ptt10 kindly?
The absolute most important to any project!
Especially the more practical constraints!
I personally think it's much wiser to start from a solution point of view, instead of "I have/want these drivers" point of view.
Or in other words, what are you trying to solve?
In fact, we don't even have to take care about BL(x), Kms(x), Le(x) and especially Sd(x) anymore.
Without cone excursion, there are NO intermodulation issues anymore from these things, or at least extremely low.
There are two ways we can get very low distortion.
1 - Either design a woofer that does everything. Which also leads to compromises.
2 - Split the frequency range into a woofer that is far more optimized for mid-range performance, as well as subwoofers that are more optimized for low-end.
Since a multi-sub system is always a better solution, the first option will always be a hard compromise in my book.
Purifi tries the tackle the first option.
The main question that I haven't seen being asked yet @Iamimpossible
Keep in mind that 10 inc vs 15 inch will give you a very different directivity.
A 15 inch will beam a lot more, has a smaller sweetspot, in-room radiation and will therefor also sound drastically different.
I don't know your room and also if that is the sound you're want to go after?
Thank you I will consider directivity. I think I have a really good idea of what to look for.
Does anyone know where I can buy a seos horn?
Does anyone know where I can buy a seos horn?
yes exactly !
there are several distortion mechanisms even for zero excursion: Le(x) causes Bl(i) modulation and the current induces hysteresis distortion in the iron of the motor. Especially the hysteresis distortion is annoying to my ears.
we simply lower all types of distortion. restricting the bandwidth adds another benefit of course but lowers but does not remove IMD
we have pointed the directivity difference out early in thread
I appreciate the recommended problem solution methodology, but I also wanted to be educated where I'm new to this and wasn't exactly sure what I wanted.
You probably mean Le(i) here, since there is basically no x
Well it removes the excursion component, so it most certainly lowers the IMD very significantly!
In some cases removing IMD for any practical purposes.
But yes, theoretically there always will be a teeny tiny hint of IMD left I guess.
But that's just getting incredibly pedantic in my opinion.
Even more so when this is being swamped by (background) noise and other masking effects.
Fact is that you can simplify the driver, cone and motor design drastically (and therefor costs) if you just don't want to do everything with one driver.
Or in other words, you're fighting against many compromises for choosing an all-in-one solution.
Yet it still limits the ability to have a proper low-end in a multi-sub setup.
Unless you want to renovate and rebuild the room with proper acoustics, there aren't many other solutions for the low end.
But even if we dismiss all of that for a second.
When we split the response over multiple drivers, we can also change the aesthetics as well.
Have a very slim and nice looking cabinet for example, while having some nice big Sd subwoofers discretely hidden away.
More Sd = less excursion = less IMD problems to begin with.
Probably even a lot more headroom as well 🙂
Le(x) causes a current dependent Bl if Le(x) is not constant with x (change in Bl is 1/2Le’(x)•i).
Even if excursion goes away the above mechanism persists since we still need current.
I agree that larger Sd generally helps reduce distortion. But some can be hard to make up by scaling Sd up, eg a 30dB reduction in the Bl modulation or hysteresis distortion.
Even if excursion goes away the above mechanism persists since we still need current.
I agree that larger Sd generally helps reduce distortion. But some can be hard to make up by scaling Sd up, eg a 30dB reduction in the Bl modulation or hysteresis distortion.
I don't follow because if we split the frequency response up, we don't only win Sd, but also win with all the other modulation products as well?
So we are literally improving in both directions.
Not only that but we can also optimize in both directions.
A (sub)woofer with a similar linear and nice performing motor with more Sd will always win, never loose.
Or in other words, you can simplify the design for getting the same amount of performance.
Doubling the Sd would already give you at least 6dB better performance with all things being equal and lower total power (therefor current) by a factor 4!
But looking at most measurements, that performance upgrade often seems significantly higher. 🙂
Really? If you are discussing filter theory I agree completely. If you are discussing a woofer as it functions it is not exactly that simple. The balance between motor force and mass is what will get you your transient response. The effects of a woofer to start and stop are solely the function of the motor system. The amplifier provides an opposite electric signal to the static motor force that ideally the motor reflects perfectly. There are a few places where that perfect reflection and be adversely effected. Generally size of cone has little if anything to do with this. One measure is the BL^2 /Re. This shows you the potential horsepower. (I know you understand this Lars, it's not written for you!)
There is no such thing as fast bass. There is a strong motor. What gets glossed over many times is that a woofer cone is more or less a fulcrum. The force provided by the motor gets multiplied as the woofer cone size increases. The basic efficiency goes up. When I design a motor for a small woofer like a 5.25 I need more motor force on that little driver to equal the efficiency of a 6.5. Take roughly the same motor and attach an 8 inch or a 10 inch cone and your efficiency increases a little more. A little food for thought about the basics.
Well there is, kinda.....
It's called Q-factor, which directly translates to either a boost, or a more even response, but less energy.
The phase and group-delay go along with that.
The law of conservation of misery is definitely at play there!
Because unfortunately we can't have it all! 🙁 🙁 🙁
filter theory yes and a driver or woofer here is a filter, mainly a linear one and nearly time invariant. this means that everything about its transient response is expressed by its frequency response. Any deviation from this is due to nonlinearities. All the things you mention affect the frequency response. so theory works.
I will stay out of the ‘fast bass’ can of worms 😊. it’s again all in the impulse response/frequency response.
I will stay out of the ‘fast bass’ can of worms 😊. it’s again all in the impulse response/frequency response.
Splitting the band reduces IMD. I don’t follow why that affects Sd? except that use of very large Sd forces us to use many drivers with cross overs?
my discussion above was for the Sd scaling. Band splitting ads on top. But again, making up for eg 30dB means a huge multi-way speaker which is not exactly simpler? Good for oligarch hifi of course 😀