A question about Tapped horns

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diyAudio Member
Joined 2007
I'm asking because I am still learning how to use the sim program and I can't seem to find the easy answer by searching.
How do you get the broadest possible bandwidth in the response??
How does the shape of the horn exit effect the response??

I once built an experimental shelf ported woofer where the rear of the port was angled at 45 degrees to see what the box sounded like ( I could not hear any difference ) and was wondering what effect an angled exit would have on the tapped horn if any

If I build a pair they would be used with my planned big OB project and only for the octaves below 80Hz

Second part of the question here, is there a cheap measuring microphone for these low octaves? All of my microphones (Tandy for voice ) have huge distortions
 
diyAudio Member
Joined 2007
I think (given the cost of postage) that the Behringer from a local shop is as cheap as I will get; $75AUD each, cheapest I have found. Being semi-poverty stricken i will be using an old car subwoofer I have in the shed ; Pair of older MTX Road Thunders 15 inch, talked about these in my bass box enquiry
 
Second part of the question here, is there a cheap measuring microphone for these low octaves? All of my microphones (Tandy for voice ) have huge distortions

behringer ecm8000 - $70 to $95 depending where you buy it.
http://www.coutant.org/behringer/ecm8000c.pdf

the low frequency response is not shown on the datasheet but the company claims it captures 15Hz to 20khz. Hmm not quite sure about the low response though.

Audix TM1 - $270-$400 depending where you buy it.
http://www.audixusa.com/docs_12/specs_pdf/TM1.pdf

The Audix microphone does show its low frequency response on the datasheet clearly extending to 20Hz.

Probably a safer bet, but more expensive.
 
I think (given the cost of postage) that the Behringer from a local shop is as cheap as I will get; $75AUD each, cheapest I have found. Being semi-poverty stricken i will be using an old car subwoofer I have in the shed ; Pair of older MTX Road Thunders 15 inch, talked about these in my bass box enquiry

Do you have the exact model number or T/S data?

TH for 15's are LARGE to put it mildly. Mine are just over 22 cu.ft. (623 Liters) in volume, and took a little less then 4 5'x5' sheets of BB ply
 
diyAudio Member
Joined 2007
Large is putting it mildly
I am not too good with the program yet but I got something almost 3 metres tall and 600 deep.
Here are the T/S parametres as measured at the local shop using Woofer Tester
Fs 18.9Hz
Vas 315litres
Qes .59
Qms 11.4
3.29DCR
Le 2.6mH
X-Max is only 9mm
856cm>2 is the Sd
Very close to the published factory specs

I looked at the Cowan Audio page and showed these to my beloved. here comment was
" Not in this house" but she has been saying that about the HT subbies since we moved here
 
Having tried hornresp, and ended up loving it, id say go throught the tutorial like 6 or 7 times untill the inputs become second nature to you.

then try a different driver and see if you can manipulate parameters to get to a desired response.

The sliders sure help here as you can push stuff around, theres an option to show the original and modified response ar the same time.

You just have to noodle with it till things kind of fall into place, like learning to drive a manual transmission by double clutching.

Also try modelling a simple vented box with it, seems weird but it works to be able to sim something familiar.
 
How low do you want it to go? ??-80Hz

And in Hornresp you don't have to get a perfectly flat line to end up with good response. Even if you get a ~ shape remember those are 5dB step so isn't a huge deal, if you are between two steps in the graph that only +/- 2.5 dB in sim. And they usually have a flatter measurement in the real world
 
Hi Moondog,

Here is an input screen to go with the one I posted in your other thread, I adjusted the driver data to reflect the measured FS=18.9Hz. This is just not the ideal driver for a tapped horn, but it would work.

Regards,
 

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  • MTX_15_TH_FS_18.9Hz_Input.jpg
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Wow, I remember having 4-15" MTX RT2's in a 6ft3 isobaric bandpass tri-chamber box tuned to 60hz in my 1983 Mercury Grand Marquis. I had 2 4" ports firing into each rear corner of the trunk. That thing talked to whales while sitting in a boat...LOL! I called it "The Coffin" though. It took 2 people to put it in the trunk. It use to make the front grill flex on low notes. The 4-15's were running off an Autotek 7300BTS.
 
diyAudio Member
Joined 2007
How low do you want it to go? ??-80Hz

And in Hornresp you don't have to get a perfectly flat line to end up with good response. Even if you get a ~ shape remember those are 5dB step so isn't a huge deal, if you are between two steps in the graph that only +/- 2.5 dB in sim. And they usually have a flatter measurement in the real world

Well if Fs is 18Hz the I would be quite happy to get 18 to 120Hz, I can't hear below 25 but i can feel it.

bjorno I can't expand your thumbnails to read them
 
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