Sorry... all I can offer is Bjorn's own explanation in the original pdf of the TABAQ.
And since I am more a "hands on" kind of guy, I will follow the way the simulation leads me, and leave the hair splitting questions to scholars.
Trust me, I have dedicated whole weekend studying this exact thread.
As I remember there are none posts about slot vent tuning, this one is not related, sorry. On the original drawing vent K is much much higher than 0,7 and its tuning is much lower than 55Hz.
I don't have original MJK software, maybe simulations of Bjorn have them calculated. Not sure if Hornresp has somewhere vent coefficient input. I took TABAQ dimensions as starting point have run simulations for like 5+ different drivers and with tens of positions, vent lengths, line legths and so on and just like few days ago got to a question what K value is. I don't use slot ports, so the thing is new to me.
Hi there, just wondering, I along with quite a few members here seems to have problem getting any bass with 100g stuffing. I ended up using only 40g while a member removed all stuffing. I know in Bjorn original design he recommended 100g. Did you able to get good bass from your speakers?
Not really following all this, so will only say that for a given tuning [Fb] and vent area [Av], the slot [shelf] vent's top plate will be a lot shorter than a standard tube's length [Lv] due to its bottom, side 'plates' being somewhat longer to average out its acoustic path-length to match the round tube's.
GM
GM
FWIW, using just basic max flat vented T/S theory it will do ~51.42 Hz Fb in 15.96 L, so should have plenty of nominal flat response with a strong peaking at a 55 Hz Fb = a significant amount of damping in theory, though Xmax wise, can only handle a fraction of a watt down low.
Vb = 20*Vas*Qts'^3.3
Fb = 0.42*Fs*Qts'^-0.96
Of course as net Vb shrinks, so goes the bass rolling off at an ever higher F3 for a given tuning.
GM
I've had people walk over to the sub to see if I was telling the truth when I said the sub was turned off.
I guess that means enough bass...
That was with the 4" TB 1052sdf.
Yes. The bass is good and tight. I ended also with 40g, anything between 20g and 60g also works well for me.
Yes, that's the exact thing I am asking. If translating it to online/offline calculators, what K coefficient should I use? Default is ~0.7 for simple round vent in the middle of the speaker baffle. The picture in my first link suggests 2.2 due to the reason you said, but if calculated with that coefficient the results are somewhat strange: very very short slot ports are suggested.
Of course, if some smart mind says that info in this picture is wrong - case solved. Or even another reason... I am just calculating wrong.
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Both my 4FE32 and P830987 cabinets produce a nice tight punchy bass with 100g stuffing. If you are used to larger cabinets and drivers which add more warmth to the bass you might think that something is missing to begin with. Bjorn kindly modelled the 4FE32 for me and recommended 100g which after experimenting with less stuffing I agree with. When I reduced the stuffing the slight increase in bass was at the expense of a loss in focus.
I should add that both my pairs are used right up against a wall (small uk rooms!!) which obviously helps. Also it is worth checking that your drivers are firmly mounted (gasket?) and appropriate screws are used especially with 12mm mdf!!. Plus no leaks from however you have mounted your speaker sockets.
I should add that both my pairs are used right up against a wall (small uk rooms!!) which obviously helps. Also it is worth checking that your drivers are firmly mounted (gasket?) and appropriate screws are used especially with 12mm mdf!!. Plus no leaks from however you have mounted your speaker sockets.
I think this might be the answer to nas's question. I'm not sure that BR maths applies in quite the same way to MLTLs. Maybe studying Quarter Wavelength Loudspeaker Design will help?
XRK is a guru of accidental MLTL, but in short - not exactly. MLTL box is defined not only by internal volume, but also by line length. If you have some known good BR design for a driver, maybe you can "translate" it to MLTL, but I hardly doubt, as, for example, Tabaq volume is 10L for small 3-4 inch drivers.
Tuning frequency of the port I think is the same and can be calculated as BR.
My suggestion to read Accidental MLTL Technique
p.s. I am newbie too and maybe you (and me) need for explanations from seasoned vets.
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...It may be, if my question was about the MLTL. The question was about TABAQ, but i can ask the same question about any box design with slot port, which has slot port of all speaker box width. I will not over complicate asking about proximity to the ground etc.
It is dead simple: if I want to simulate/calculate vent tuning, what K(or k) coefficient I have to use? Closer to 0.7-0.8 or 2.2?
Yes, I have read pretty much everything related to MLTL on the internet. It is not that much of structured info as you think.
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May I ask to calculate vent tuning frequency for me of the default TABAQ? With any online/offline calculator available.
Thank you.
I would ask Bjorn to do it for me on this thread. He did the original calculations with the MJK software, which I don't have.
I have not seen MJK software, but from the all the result sheets over the web there are no port correction factor. We are here on our own.
Hi Captain!
Wondering if you can share the specific PDF/design you used with the Peerless 830987 driver, along with any other design thoughts/etc?
I built this design (TABAQ TL for Tang Band) using those drivers, and am, at this point, a bit disappointed with them. Certainly not comparable to the Alpair 11ms I've since built in both BR and MLTL.
That said, I haven't experimented with stuffing amounts & location, so I'm hoping it's something obvious!
Thanks in advance!
Translating to nothing........ Per the chart, a shelf vent has a 2.227 'pipe' end correction, though without access to my own calculator based on measurements, not on pipe end corrections per se, I can't say how accurate it is other than it's my understanding that the chart has been vetted/well proven by others, both pro and DIY.
Re when does a reflex, which is presumed to have a uniform particle density air mass 'plug', change to a 1/4 WL resonator [MLTL, etc.], is when simmed using accurate pipe/horn theory, the 'visible' and/or measured turnover point is when the reflex calculated alignment is 'stretched' to a high enough aspect ratio [pipe compression ratio [CR] to my way of viewing it] that the vent is becoming too long for a given vent area [Av], i.e tuning [Fb, Fp] is 'creeping' lower due to increasing 1/4 WL pipe action increasingly damping the vent with increasing CR.
I currently only have Hornresp
loaded, which has no shelf vent option and otherwise WRT accuracy only know that it's good enough when the vent is a reflex [hole in a box], be it just a box or some type of MLTL and one pipe vent MLTL recently done by 'Scottmoose' in MJK's software for comparison.
All that said, historically it was recommended to start with too large and or too long a vent and do final tuning in-room and IME, many times I had to tune each cab individually for best overall in room performance; though admittedly I'm from the era of 'acoustic solutions to acoustic problems' since highest practical acoustic efficiency was a primary goal, whereas today with ~affordable, high SQ, all encompassing DSP, cheap high power; speaker design has become mostly moot in [casual] DIY, consumer HIFI/HT apps.
GM
So the cabinet I built is the same as yours except the distance from the port to the inside top of the cabinet, where you have 792mm mine is 774mm i.e 762mm (30 inches) length (inside top of cabinet to start of port). Don't suppose this makes a difference though.
Used 100g stuffing (can't be changed once box is sealed due to very small driver cut out so I haven't tried any other amount).
Stuffing is one continuous piece per speaker rather than small bundles.
My first thought would be the driver itself. I'm still not certain how much driver break in affects a speaker or whether its our ears getting accustomed to a certain sound but my 830987 were previously broken in. Prior to this they did sound a bit bright on occasions. Also they do not come with a gasket, I assume you made something up for this?
To me the Tabaq with 830987 are just so 'listenable' and not fatiguing in any way. Not big bass monster speakers of course but there is so much else as a trade off. If you could say what disappoints you it would be useful, it may just be we have different tastes and requirements
I agree with the captain – very very pleasant and satisfying to listen too and certainly their bass is amazing for the size driver and cabinet. I don’t think the stuffing or driver break-in is the problem here.
I built a set with 12mm MDF using the P830987 drivers using Plan B in Post #1651. I probably used less stuffing than 100g. I can't weigh it. But you can see my build and the amount of stuffing in Post #2404.
Something else might be your problem:
- are all the joins air tight?
- how did you mount the drivers?
- are the drivers not out of phase perhaps?
Some photos of your build might help.