I'm adding a mid/upper range driver (Vifa TC9FD18-08) on top of a Transmission Line enclosure.
Obviously the TC9 will be in it's own sealed enclosure.
The TC9 has a Qts of 0.89.
This is outside the range of all of Vance Dickason's tables for sealed enclosures.
I've run it in WinISD with mixed success.
The first run was with the factory T/S parameters.
The second run was with someone's T/S parameters from their own testing.
I got dramatically different Vb's.
I also got high Qtc's (around 0.95).
Am I heading in the right direction, or can someone help with recommendations for how to design a sealed enclosure for a mid-range driver?
Obviously the TC9 will be in it's own sealed enclosure.
The TC9 has a Qts of 0.89.
This is outside the range of all of Vance Dickason's tables for sealed enclosures.
I've run it in WinISD with mixed success.
The first run was with the factory T/S parameters.
The second run was with someone's T/S parameters from their own testing.
I got dramatically different Vb's.
I also got high Qtc's (around 0.95).
Am I heading in the right direction, or can someone help with recommendations for how to design a sealed enclosure for a mid-range driver?
You usually want to cross the driver (far) above resonance frequency in the box, so the Qtc should not bother you.
It is more relevant to control enclosure reflections/resonances, so be sure to stuff the box, avoid identical dimensions and parallel walls.
At which frequency do you plan to cross the TC9 with your transmission line woofer?
If around 500Hz, just use a volume of about 2 litres and be done with.
If around 500Hz, just use a volume of about 2 litres and be done with.
At this stage, just based on the manufacturer's SPLs, I looking at crossing at around 800Hz (maybe).
The driver in the TL is Dayton's RS225-8.
X has used the RS225 in his FAST enclosures, but I want to design my whole system from scratch, so I can learn how to use Hornresp and Xsim properly.
Nordo, remember that the box calculations is about how to handle the drivers resonance and get the most low end out of the box/driver combination. If you cross far above the drivers Fs, no program vill really help you with anything. The Q is valid for the box at Fs but has no meaning at 4 or 5x Fs...
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have a look at this thread for fullrange enclosure and crossover frequency:
https://www.diyaudio.com/community/threads/10f-8424-rs225-8-fast-waw-ref-monitor.273524/sports cone enclosure:
https://www.diyaudio.com/community/...t-waw-ref-monitor.273524/page-45#post-5300841
https://www.diyaudio.com/community/threads/10f-8424-rs225-8-fast-waw-ref-monitor.273524/sports cone enclosure:
https://www.diyaudio.com/community/...t-waw-ref-monitor.273524/page-45#post-5300841
Not true, Basta! will tell you everything that you need to know, re. box volume, xover slope and freq., driver location on the baffle and much, much more.
http://www.tolvan.com/index.php?page=/basta/basta.php
On top of that Svante, the author is a member here at DIYAudio.
Absolutely - all that is useful but not the Q aspects. ("Anyting" was not correct -my bad!) By all means use Basta - I have met Svante - a very nice and insightful person.
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Don't forget the outside while thinking the inside! Mind baffle step and diffraction especially, the whole system you are putting together. Always remember to think possible trade-offs, what is it that you are not concentrating / doing but still happens behind the scenes. This is what can bite you, optimizing something further and further without noticing something else equally important deteriorate 🙂 This is something very inherent with a volume (box), there is inside and outside with kind of opposite interests yet they are interlinked. Bigger inside can benefit both bass and higher frequencies (effective damping) but at the same time you'd need to fit other drivers somewhere and mind things like the diffraction and panel resonances which can start to eat the higher frequencies as you optimize for bass or the other way around, then there is build difficulties and budget constrains and what not. As an example consider open baffle (no baffle at all!) that doesn't have any problems inside or outside because there is no either, and it is free, no construction at all! But now there is no bass and some back radiation that can be good or bad thing depending rest of the system. Just something to think about, why box at all? Have fun!😀
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The TL with the RS225 is only for the low frequencies.
Everything else (via the XO) will be taken care of by the TC9 in the sealed box.
I intend to incorporate the box on top of the TL enclosure.
The TC9 will be offset on it's baffle so that the distance to each edge is different.
Thanks to the experimenting with the manufacturer's T/S data versas someone's tested data, I'm now realising that I'll have to buy all my drivers, then test them individually before I can design my enclosures.
I just never realised the enormous variation between the manufacturer's specs and actual individual testing.
Everything else (via the XO) will be taken care of by the TC9 in the sealed box.
I intend to incorporate the box on top of the TL enclosure.
The TC9 will be offset on it's baffle so that the distance to each edge is different.
Thanks to the experimenting with the manufacturer's T/S data versas someone's tested data, I'm now realising that I'll have to buy all my drivers, then test them individually before I can design my enclosures.
I just never realised the enormous variation between the manufacturer's specs and actual individual testing.
Another quick question :-
My sealed box for my Vifa TC9 (3" cone) is 100mm (4") high x 251 (10") wide x 342 (13.5") deep.
It ended up being this size and shape, as it is bult into the main cabinet.
This gives me a Vb of 8.58L, but WinISD, etc. give me a Vb of around 5.2L.
Therefore I'm thinking of adding some non-absorbent packing into the rear of the box, to maybe form a concave shape which will reduce the reflections off the rear of the box and reduce the box volume a bit as well.
The rest of the box will be fully filled with fibreglass.
Is this idea worth doing?
And if so, what would be a suitable material to use for the rear packing?
My sealed box for my Vifa TC9 (3" cone) is 100mm (4") high x 251 (10") wide x 342 (13.5") deep.
It ended up being this size and shape, as it is bult into the main cabinet.
This gives me a Vb of 8.58L, but WinISD, etc. give me a Vb of around 5.2L.
Therefore I'm thinking of adding some non-absorbent packing into the rear of the box, to maybe form a concave shape which will reduce the reflections off the rear of the box and reduce the box volume a bit as well.
The rest of the box will be fully filled with fibreglass.
Is this idea worth doing?
And if so, what would be a suitable material to use for the rear packing?
Don't do a symmetrical fill - it will make any reflection more pronounced i.e. with a higher Q (peakier resonance). If you can create a space wich is a pyramid with 3 sides it would be advantageous. Why not try some of the stiffer/denser polystyrene packing material? Cut it to suitable pieces and use some glue to fix them in position. Easy try and quickly removable if a fail... butI think it will be good.
The TC9 has an equivalent volume of compliance Vas = 1,24. This means that if you put it into a sealed enclosure of 1,24 litre, you will get a Q of 0,7 at the resonance frequency which is 125 Hz. Now, if you cross it higher, you could do with even lesser volume. What is your X-over? As someone said above - make it 2L and call it the day ;-) I would make it 1 if I used it down to 4-500 Hz....
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The TC9 has an equivalent volume of compliance Vas = 1,24. This means that if you put it into a sealed enclosure of 1,24 litre, you will get a Q of 0,7 at the resonance frequency which is 125 Hz. Now, if you cross it higher, you could do with even lesser volume. What is your X-over? As someone said above - make it 2L and call it the day ;-) I would make it 1 if I used it down to 4-500 Hz....
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The woofer is an 8" Dayton RS225 in a transmission line enclosure.
I know I haven't really picked two drivers that suit each other, but my idea was a FAST design, and I admit, without a lot of driver research.
I dispensed with a tweeter as I can't hear above 15kHz anyway.
I was hoping to get a bit more value out of the RS225 by crossing closer to the 1kHz - say 800-900Hz.
The RS225 is almost dead flat up to nearly 2kHz (factory SPL).
The polystyrene sounds like a simple method.
When you say pyramid (which would be a very skinny pyramid - 100 x 251)) are you thinking with the pointed top facing the driver, or facing the rear of the box?
As well as my idea of creating a concave rear to the box, I was also thinking of maybe making the whole rear wall a acoustic diffuser. Your polystyrene would be suitable for any of these ideas.
I'm not sure which shape would create the best end result, or even if it's worth doing anything.
Logic says any method of breaking up the flat surface of the rear wall would help.
