Hello 🙂
I am playing arround with hornresp for some time now, trying to find the best enclosure for my DD Audio 608D2.
When i kinda understand now how to get what i want... i just realised... i do not really know WHAT i want.
So i got a few questions, you guys hopefully can answer me.
I got a pretty huge car (4.1m x 1.9m x 1.5m inside), in wich i want to use this sub in. So kinda low resonance and not that stiff chassis.
Lets start with the following image, how do i want it to look in my car if i want a mostly flat in car response? Do i want the sub to play up to 200Hz as seen in the images? Or is it better to crossover earlier?
So, more precise questions to this:
Do i want more like a curve at the end, like in "D", or more like a slope like in "A" ?
Do i want the upper end above 200Hz more like "C" going down continiously, or do i want it like in "B" with a as big as possible steep gap?
Also another thing i realised while simulating, since i am tuning below fs(38Hz), i get a lot of excursion OR group delay.
Is it allways low group delay vs high excursion / high group delay vs low excursion? Or is there anything i could do, do keep excurion AND group delay low?
Oh, one more question... my driver has a one direction xmax of 13mm and a xmech 32mm ... what would be a save value (hornresp displacement) to use it at low frequencys like 30Hz and below? (simulating at my amps rms output of 600w)
20mm? 25mm? Or should i defently stay at xmax?
Thanks in advance
Benni
I am playing arround with hornresp for some time now, trying to find the best enclosure for my DD Audio 608D2.
When i kinda understand now how to get what i want... i just realised... i do not really know WHAT i want.
So i got a few questions, you guys hopefully can answer me.
I got a pretty huge car (4.1m x 1.9m x 1.5m inside), in wich i want to use this sub in. So kinda low resonance and not that stiff chassis.
Lets start with the following image, how do i want it to look in my car if i want a mostly flat in car response? Do i want the sub to play up to 200Hz as seen in the images? Or is it better to crossover earlier?
So, more precise questions to this:
Do i want more like a curve at the end, like in "D", or more like a slope like in "A" ?
Do i want the upper end above 200Hz more like "C" going down continiously, or do i want it like in "B" with a as big as possible steep gap?
Also another thing i realised while simulating, since i am tuning below fs(38Hz), i get a lot of excursion OR group delay.
Is it allways low group delay vs high excursion / high group delay vs low excursion? Or is there anything i could do, do keep excurion AND group delay low?
Oh, one more question... my driver has a one direction xmax of 13mm and a xmech 32mm ... what would be a save value (hornresp displacement) to use it at low frequencys like 30Hz and below? (simulating at my amps rms output of 600w)
20mm? 25mm? Or should i defently stay at xmax?
Thanks in advance
Benni
Hello. Car is like a small room. It gives you rise in the bass region. Hard to guess what will be your car behavior, but towards the deep bass, you rather need slow decay. Much milder rounder shape, close to '"D".
In the top range, you do not need it to play up to 200Hz, but it is best to have clean 200Hz range too, as even at cutoff of 90-100Hz, some higher bass creeps into the sound from your sub, and you want it without peaks and excessive problems.
For both cases, good EQ helps. For deep bass flat response, and for further off-band cutting of nasty stuff that might creep in the usable band. The peak on D at 180Hz could be a horror...
Depending on the application, GD is not causal from excursion. You can have low excursion and poor GD. It is matter of system design, box type and such.
You want to exploit the driver capabilities. On the other hand, with the onset of an impulse, many enclosures allow for more excursion before few periods of the signal stabilize it at average excursion. Before this stabilizing, higher peak can happen. And so you are supposed to stay very near Xmax, and not push it. Also prolonged strain past Xmax might shorten the life of driver suspension.
I do not have great experience with simulators and excursion, as simulators have no way of knowing the progressivity/linearity of it. Therefore I "measure it" on place.
In the top range, you do not need it to play up to 200Hz, but it is best to have clean 200Hz range too, as even at cutoff of 90-100Hz, some higher bass creeps into the sound from your sub, and you want it without peaks and excessive problems.
For both cases, good EQ helps. For deep bass flat response, and for further off-band cutting of nasty stuff that might creep in the usable band. The peak on D at 180Hz could be a horror...
Depending on the application, GD is not causal from excursion. You can have low excursion and poor GD. It is matter of system design, box type and such.
You want to exploit the driver capabilities. On the other hand, with the onset of an impulse, many enclosures allow for more excursion before few periods of the signal stabilize it at average excursion. Before this stabilizing, higher peak can happen. And so you are supposed to stay very near Xmax, and not push it. Also prolonged strain past Xmax might shorten the life of driver suspension.
I do not have great experience with simulators and excursion, as simulators have no way of knowing the progressivity/linearity of it. Therefore I "measure it" on place.
Thank you, that allready answers some of my questions.
Based on what you said, i come with something like this... does that look usable? I know... i would need to know the incar resonsances for perfect fit, but i want to know in what direction i have to go for it.
So, how would this one look like?
About the group delay and excursion...i just can not get one without the other...
No matter, if i make the rear chamber smaller, to get less excursion, or if i add the highpass filter to reduce excursion... in both cases group delay like doubles at the point, where i can stay at xmax.
So what else could i do to decrese excursion without adding group delay?
Based on what you said, i come with something like this... does that look usable? I know... i would need to know the incar resonsances for perfect fit, but i want to know in what direction i have to go for it.
So, how would this one look like?
About the group delay and excursion...i just can not get one without the other...
No matter, if i make the rear chamber smaller, to get less excursion, or if i add the highpass filter to reduce excursion... in both cases group delay like doubles at the point, where i can stay at xmax.
So what else could i do to decrese excursion without adding group delay?
Yes, that way it looks closer. Even rounder knee in the low bass would be wanted. The peak at 150Hz could be EQd out further -6dB sharply if possible. Maybe stuffing the box could help.
What you probably do is not looking at it the right way. Maybe, making the chamber smaller means more loading of the driver by the vbox resonator. And resonators have big group delay.you might want to unload, so the speaker does more job, not the resonator. But the price to pay is cone excursion indeed. It is inevitable, you just pick your poison.
What you probably do is not looking at it the right way. Maybe, making the chamber smaller means more loading of the driver by the vbox resonator. And resonators have big group delay.you might want to unload, so the speaker does more job, not the resonator. But the price to pay is cone excursion indeed. It is inevitable, you just pick your poison.
Thank you once more.
I came up with another question...
Since i am designing my enclosure as frontloaded horn, i only have one accoustical output (the mouth of the horn).
Would it make sense to split the accoustical path and let the 2 mouthes end as far seperated from each other as possible?
To make it clear, i have like 200l for the woofer above my driver's cabin. My idea so far is:
Letting the horns mouth end alligned with my front window from above. Since my front window is 1.5m wide, and i need like 1500cm² of mouth area, i could do 1 slot 10cm as wide as my front window (10x150=1500cm²)...
...or i could do 2 ports 20cmx37,5cm, one at the right side, one at the left side, so 75cm apart from each other.
Does that make sense? Will it have pretty much the same effect as using 2 woofers (for sure not power wise, but sound distributioin wise)?
I came up with another question...
Since i am designing my enclosure as frontloaded horn, i only have one accoustical output (the mouth of the horn).
Would it make sense to split the accoustical path and let the 2 mouthes end as far seperated from each other as possible?
To make it clear, i have like 200l for the woofer above my driver's cabin. My idea so far is:
Letting the horns mouth end alligned with my front window from above. Since my front window is 1.5m wide, and i need like 1500cm² of mouth area, i could do 1 slot 10cm as wide as my front window (10x150=1500cm²)...
...or i could do 2 ports 20cmx37,5cm, one at the right side, one at the left side, so 75cm apart from each other.
Does that make sense? Will it have pretty much the same effect as using 2 woofers (for sure not power wise, but sound distributioin wise)?
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This is very "random" or unmanageable in the design part. Basically, no, for various reasons one source is better, but for the environment, we do not have much idea what will it do in your car. This rather needs to be tried and developed. No idea what will end up as better.
Generally I'd say you're identifying certain degrees of freedom responsible for changing certain properties.. however without knowing the reasons it's probably just overthinking. Much of it won't make a difference unless certain circumstances exist, especially at lower frequencies.
Since i am not verry flexible with the build, my idea was to get rid of as many bad pssible things as possible, while "engeneering" it.
I have no problem with overengeneering... i am allways doing that 😀
The question is just... could it help more, then it would make it worse? If the answer is yes, i might do it.
Just to show why i am kinda unflexible to rebuild the box... i got the green area for the box, while the grey area is used for other sstuff.
Thats a view from top on my driver's cabin.
I have no problem with overengeneering... i am allways doing that 😀
The question is just... could it help more, then it would make it worse? If the answer is yes, i might do it.
Just to show why i am kinda unflexible to rebuild the box... i got the green area for the box, while the grey area is used for other sstuff.
Thats a view from top on my driver's cabin.
What would you do if I said horns do their best radiating when they are kept round because it reinforces their directivity? Don't worry, that's probably not the concern with a tapped horn and I say probably because I'm probably doing as much speculating as you are.
In any case I'd be running simulations of how cabin modes are driven using this setup and investigating the alternatives that way.
In any case I'd be running simulations of how cabin modes are driven using this setup and investigating the alternatives that way.
Slots should be limited to < ~9:1, so @ 15:1 it may 'whistle' even at low power. Otherwise, consider that two sources < ~1/4 WL apart will sum as one, so @ 80 Hz = ~13543/4/80 = ~42.32" Vs your 1.5 m = ~59" = < a 1/2 octave apart (still pretty good summation), ergo in such a confined space seems like 'six of one/half dozen of another' to me. 😉
Wow thank you, that was some missing information for me, and exactly what i was looking for.
So, as long as i dont place 1 sub at the end of my car, and the other one at the front, it does not make any sense at all.
Also that means, a 20x75 mouth placed in the middle would be best.
Oh, talking about "ports" design, how does that count for horns? Dont they chuff at the throat? Is it just the end of the port, wich contacts with the surrunding wich chuffs?
Thank you 🙂
Oh, one more thing to this... i am not sure, but does this 9:1 thing make sense? I just thought a bit more about it...
...and lets take a 100x10cm Port... since this is >9:1 it should make problems. But if i divde that port now into two, it is 2 times 50x10cm, wich would be 5:1 and like that beeing <9:1
So if that 9:1 thing would be true, you could just make the port "smaller" to get rid of that noise? Does that make sense?
Great clever thinking and approach. Take this as rule of thumb, not a dogma. Best outcome usually comes from round port. Anything deviating from that will result in lower tuning, more air drag and more noises from the port friction and such. The thinner the port is, the more likely it will happen. It usually happens more for small ports, like 2cm x 18cm, hence this rule of thumb. at 10x100cm, it is wholenother story. But it is not realistic either. Try to simulate this 100x10cm port length for normal case of enclosure. It will be out of usability "band". So, yes, no... 🙂
It is in the usable band at this size, as you can see in the following pics 🙂
I was simulating a lot more in the last days, and came up with something nice (at least in my eyes), and need your opinion about it.
It is a stubbed horn, here are some pics of the simulation:
I got a few questions related to that:
- What do you think about it? will this be usable?
-> The cone movement should be ok like that... i did not use any high- or lowpass here...could i use it WITHOUT any filters, like it is?
My idea here is to adress the delay, wich filters produce... i think i could come up with some similar or even better delay compared to a BR-Box wich uses filters
- At wich frequenzy would i crossover, and more important...how does the crossover work with these delays/phase changes?
Thanks for your help
Benni
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You're welcome!
Not really if you mean its acoustical center since you'll be placing it in the 'room's' open pipe eigenmode's fundamental null 🙁, so ideally needs to be at an odd harmonic.
Not that I'm aware of, it just becomes increasingly more compressed til the driver fails.
It's my understanding that too high a vent mach causes excessive stiction (friction losses) increasing vent noise to audibility.
In theory and apparently in practice since it's based on heating/AC duct design experience, or at least it was when I learned in the mid '60s, so maybe been updated.
It's my understanding that at large WLs relative to the (divided) duct that it's acoustically just a single large one and breaks down as the WLs become shorter, 'fitting' inside the smaller ducts/tubes, so yes, it's a good way to 'divide and conquer' vent mach noise. 😉
Really need to Export, Attach the .txt file for us to install/view when wanting more than just basic/generic questions. 😉