need help with tapped horn calculation...

[morpheus82]

Hi guys,
I have a Sintel 10 inch subwoofer who needs a box, so I decided to build something "new" for me, a tapped horn.
So I learned how to choose the parameters and made some simulations on Hornresp.

Driver parameters are:

model: 90.25E8
Re(ohm): 7.2
Le(mH): 0.67
Fs(Hz): 63
Qes: 0.52
Qms: 8.14
Qts: 0.49
Mms(g.): 25
Cms(mm/N): 0.36
Vas(litri): 60.1
Xmax(mm.): 3.5
Bl(Tm): 9.6
G(m/s^2 A): not available
h(%): not available
SPL/2.8V(dB): 92

Now, I've chosen a S2=sd/2, so 150cm2 and an S3=2*Sd.
Put L12 and L34 = 15cm for construction and L12=200cm.
Then simulated and used the wizard to see the result...

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

I think not really good...and with just 50w, displacement is too high...
Response absolutely not flat...

So, where I am wrong?
I tried to modify the values, but there is no way for me...
Maybe the driver is not good for a tapped horn?
Thanks a lot in advance guys!

 

[oublie]

Try this, not great but a start. With 3.5mm of xmax your not going to get loud and low.

 

[morpheus82]

Thanks mate, but now we have a much bigger enclosure, and just 10w of power.
And we're still on the limit for the xmax...

 

[oublie]

your not going to get great response from a driver like this.

what are your requirements?

box size, frequency response, db lvl?

 

[morpheus82]

I know, but the driver is here looking at me...for free...!
Let's say max 80 liters, 30-100Hz would be great, dB level not really important...
Which box do you think it's good for this driver?

 

[tb46]

Sintel 90.25E8 10"

Hi Y'all,

The Sd looks a little small for a 10" driver, you might want to check that because it affects the following calculations if you use Hornresp to calculate Cms etc.
Also, it would be better to use Par for the horn taper, as it more closely reflects a horn path with 2 parallel sides. If you double-click Sd in the Edit mode it gives you the Thiel-Small parameters Hornresp is using in the calculation, they should agree with your measured parameters (or the manufacturers).

Regards,

 

[morpheus82]

Thank tb46,
well, for the measurement, do I have to consider only the cone diameter? Or also the foam?

 

[tb46]

Hi morpheus82,

A general method to establish Sd is to measure the diameter of the cone plus 1/3 to 1/2 of the surround on each side, then it's just Sd = D^2 * pi/4.

For a volume below 100L you may be best of with a simple bass reflex (vented) enclosure.

Regards,

 

[morpheus82]

I've tried some simulations with vented, but I have lower efficienfy and higher cutoff frequency...Cannot reach nothing under 55Hz...

 

[morpheus82]

actually I measured again, effective diameter is 212mm, so Sd is 350cm2 more or less.
This helps more than what I expected!I will post some results later.
The behaviour of the response is still not so good, but I can put 100w without destroying the driver and reach 30Hz...Not bad...

 

[tb46]

Hi morpheus82,

I guessed at 340cm^2, try this in Hornresp:

Regards,

 

[morpheus82]

Thanks tb46, do you think I have to simulate it with rear chamber too?
Same dimensions for the box?

 

[bjorno]

FYI:

b

 

[IslandPink]

Hmm

The original post didn't look like a proper TH set-up - it was likely missing the second driver input .
Post 11 is also not a TH set-up .

Bjorno's post makes more sense , as does Oublie's .
Try this script attached ( store & read it from the 'import' folder ) if you are still having problems - you'll have to change most of the data of course !

 

[tb46]

Hi,

Post #11 is a BR (bass reflex, or vented). The tapped horn will be much larger than what morpheus82 is looking for. Bjorno's is tapped tapered quarter wave tube.

Regards,

 

[IslandPink]

Aha, Thanks, looks like the project is changing fast !

 

[morpheus82]

Well, not really changing...
My idea is to try the tapped horn, because I'm curious to hear the result.
Then my target for volume is around 80 liters, but I can change this value...
Thanks bjorno for your simulation, looks very good! But you used parabolic sections, how can I achieve easily a parabolic section? Conical one is very easy...

 

[epa]

Well, not really changing...
My idea is to try the tapped horn, because I'm curious to hear the result.
Then my target for volume is around 80 liters, but I can change this value...
Thanks bjorno for your simulation, looks very good! But you used parabolic sections, how can I achieve easily a parabolic section? Conical one is very easy...

have you set th in the driver arrangement?
first post doesnt look like a th.
post your hr inputs
bjorno's design looks alright,you can make it even a bit smaller ,start with s2 500,and s4 275,lengt 215 total ,i think ~110 ltrs when bild

 

[morpheus82]

Thanks A LOT epa, you are right, I did not seected "tapped horn" in the driver arrangement.
Sorry for my stupid question, I have always seen TH with S4>S1, is it still a TH if S4<S1?
What is the difference between the 2 systems?
Have you chacked also the displacement?

 

[tb46]

Hi,

Bjorno's design is not a tapped horn. He even indicates on his diagrams that it is something different. It 's a fine design, there is nothing wrong with it, but if you want to build a tapped horn, bojorno's design isn't it.

Regards,