It does. Scott gave me the numbers. We are currently working on a set on the smaller Mileva to install A7.3 instead of FE127. Should be tuned lower so a simple addiiton of a vent spacer.
Beingan ML-Voigt the cabinet dominates, so more latitude for alternative drivers. Native alignment is overdamped to fit flush against wall.
If there is too much bass some damping in the vent slot shoud help there.
dave
PS here is the link to the real drawing instead of a screen shot.
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To the 1st approximation all vented alignments adhere to the basic BR alignment:
Vb = 20*Vas*Qts'^3.3, Fb = 0.42*Fs*Qts'^0.96, so until Vas gets quite large, Qts' dominates both box size and always box tuning.
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
Using BS2022 method in HornResp gives a reasonable looking first draft in a 68L tapered TL for the SB20FRCP30-- light stuffing and guessed path.
Thanks for all your answers! I spent the better part of my night (got to bed at 4AM) playing around with HornResp and reading all I could about transmission lines. I finally somewhat made sense of how things work. I might go all the way with this and really try to design my 'own' speaker
I understand that though. I wish I had a home and enough mean to truly make something both optimized and remarkable. Thing is, being a poor, budding visual artist with very limited means, my bedroom at the moment is my living room, office and studio at the same time. Every bit of sqm counts and it's all about optimization.
Given the fact that having a cabinet built to my specifications would cost me over 400€, and that simply ordering pieces cut out of 18mm MDF without any angles, holes or anything else would by itself still be about 200€s (gotta love Belgium where every single thing has gotten immensely, stupidly expensive over the past 3 years), I have decided I was going to build a few cabinets prototype out of XPS foam before committing to having something made out of wood.
I have given this a lot of thoughts over the past few days, and I'm currently designing a set of 3D printed tools that will make the fact of cutting, glueing, chamfering and sealing XPS a lot more precise and a lot more efficient. I will make sure to post my findings regarding that. The cabinet's bracings will also be made out of tough 3D printed parts to ensure the cabinet doesn't sound weird.
From what I've seen, and thanks to xrk971, some great things can be achieved with XPS, as long as you're precise.
I understand that though. I wish I had a home and enough mean to truly make something both optimized and remarkable. Thing is, being a poor, budding visual artist with very limited means, my bedroom at the moment is my living room, office and studio at the same time. Every bit of sqm counts and it's all about optimization.
Given the fact that having a cabinet built to my specifications would cost me over 400€, and that simply ordering pieces cut out of 18mm MDF without any angles, holes or anything else would by itself still be about 200€s (gotta love Belgium where every single thing has gotten immensely, stupidly expensive over the past 3 years), I have decided I was going to build a few cabinets prototype out of XPS foam before committing to having something made out of wood.
I have given this a lot of thoughts over the past few days, and I'm currently designing a set of 3D printed tools that will make the fact of cutting, glueing, chamfering and sealing XPS a lot more precise and a lot more efficient. I will make sure to post my findings regarding that. The cabinet's bracings will also be made out of tough 3D printed parts to ensure the cabinet doesn't sound weird.
From what I've seen, and thanks to xrk971, some great things can be achieved with XPS, as long as you're precise.
Yes, the response looks messier without the tapered line, minimal filling and the path between the driver unaccounted.
Hi Scottmoose
what is the dimension of the vent hole ?
Nevermind, saw the dimension as 60 mm diameter and 49 mm length
FWIW, can't recall ever seeing a round vent, always rectangular with area/aspect ratio required to make it resistive enough to only be baffle thickness depth. A sampling of Altec cabs that some go back to Lansing Manufacturing times.
Agreed; I was thinking more alignment than the duct shape per se. I did have a look at a rectangular, but CSA was a bit smaller for the 36mm baffle thickness than I usually like & without being able to test it I wasn't sure how extreme we'd need to go in the aspect ratio for a larger vent area. That's probably just me being over-cautious; as a temporary SWAG though (it's about 0350 here 😉 ) a 14mm x 150mm slot should get us roughly in the region.
Hmm, anything over ~9:1 is moving towards aperiodic with Altec's A8's 12:1 damping this cab's horrible box modes.
Right, that was the idea; I was going for about as large an Av as I could there (while boss-eyed at some unnatural hour 😉 ) for the target Fb & 36mm baffle thickness, & relying on a bit of loss since I was winging it & couldn't check. Better (now I'm able to look at it) would be 30mm x 80mm, or for the frictional limit about 27mm x 90mm, with the 36mm baffle thickness. That's maxing out the CSA for roughly the target tuning without ducting it.
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Functionally it is. This is basically GM and I having some fun as we're both paid-up fans of the old ways. 😉 He's just pointing out that because I used one of the traditional pre-T/S BR alignments for the box above (which were largely created by Western Electric / Altec etc.) I really should have used a rectangular vent of baffle thickness for the full 'authentic' design method, because that was how they were done back in the day. Corrected, or at least option now provided, above. 🙂
Got you now, thanks. When I sim the design with that port, it suggests that the excursion of the air in the port is high, relative to the port length. Is that an issue, or not actually something to worry about?
(Also, according to my sim, this driver will really unload below the port tuning - you'd want to avoid any sub 25 Hz signals, as it's up around xmax down there with just 2.83V.)
(Also, according to my sim, this driver will really unload below the port tuning - you'd want to avoid any sub 25 Hz signals, as it's up around xmax down there with just 2.83V.)
Depends how you are defining 'high' and relative to what alternatives.
Given the relatively small linear excursion of a wideband & the fact that 'you' are accepting that's what it is, in a modest sized vented box, I would say not. You'd need about 5w to push it to 0.5% SoS & you're already beyond 1-way rated travel at that point. But that's ultimately one of those 'your choice' scenarios.
It's a vented box, so unloads 4th order < Fb. With a driver that has very little mechanical damping & requires a large vented Vb, excursion naturally rockets at the bottom end, same as any such design. Try as I might, I've yet to break the laws of physics -although that isn't for lack of trying. 😉