Sanity check request for 30 Hz Tapped Horn

pk · 10th April 2010, 09:58 PM

Hi,

I am simulating a 30 Hz Tapped Horn (please see attachments) for a friend who needs a mono sub to be placed between his horn satelites. The sub is meant to be placed againt the back wall. The desired frequency range is 30-100 Hz. The driver will be a 15" Eminence Definimax 4015LF. I have tried to move the 'high frequency peak' as far up in frequency as possible. The sub will probably be run by one of the larger plate amps.

I would be really pleased if some of you would run a 'sanity check' on the simulation before my buddy finally makes saw dust! Thanks a lot!

Best regards
Peter

MaVo · 10:19 PM

Generally said, it looks fine. Personally, i try to avoid having a deep cancellation right above the passband of the woofer, as i think it will make the integration with the mains difficult, not even speaking about the horror of realizing that it is a few hz deeper than simulated and cutting into the passband. Although i have to say i never tried such a dip-thing, so this is only theoretically important. With all the tapped horns i have build so far, the high frequency spikes you see in the simulation are not present in the real measurements, so using the dip to reduce the peaks is not necessary. Also, i think none of tom danleys horns use such a dip.

EDIT: You can half the S1-S2 segment in length, since the midpoint of the woofer is where S2 is. This should reduce the dip. Also, you could try a little higher compression ratio, ie make the S1/S2 values smaller, maybe down to 300-400, which would equal a compression ratio of 2-3, which should be safe and get you a little more output.

letsbangout · 11th April 2010, 12:25 AM

A few comments:

1) S3 and S4 will be closer to 2000 or 3000 in reality - your current S4 isn't even the size of one 15" driver.

2) L12 and L34 will probably be a little shorter in reality. All of my designs seem to love a short L34, albeit I work with sometimes less-than-ideal drivers

3) lol @ the WGA crack on your desktop

pk · 11th April 2010, 08:06 AM

Hi Mavo and Letsbangout,

Thanks a lot for your thoughtful suggestions! I will try out a few more simulations with these in mind.

Best regards
Peter

pk · 11th April 2010, 08:35 AM

Hi Mavo & Letsbangout,

I have made a new simulation with reduced L12/L34 and with higher compression (due to larger mouth) in order to:

1. reduce the magnitude of the dip, and
2. to increase sensitivity

Does this look more sensible? Thanks a lot!

Best regards
Peter

MaVo · 11th April 2010, 09:43 AM

@ letsbangout: With a mounting depth of 17cm and a diameter of about 38cm the minimum value for S3 and S4 should be 646cm².

@ pk: I spoke about reducing the S1 sliders value... but maybe that would need a 4 segment horn to work properly. You could just keep it that way and it would be fine.

pk · 11th April 2010, 10:25 AM

Quote:

Originally Posted by MaVo

@ letsbangout: With a mounting depth of 17cm and a diameter of about 38cm the minimum value for S3 and S4 should be 646cm².

@ pk: I spoke about reducing the S1 sliders value... but maybe that would need a 4 segment horn to work properly. You could just keep it that way and it would be fine.

Mavo: About 'keeing it that way' - did you refer to my last simulation?

Thanks!

Best regards
Peter

bjorno · 11th April 2010, 10:45 AM

Hi Peter,

Compare with my simulations:

b

MaVo · 12:04 PM

Your last looked better than the first. I think its good.

pk · 11th April 2010, 01:51 PM

Quote:

Originally Posted by MaVo

Your last looked better than the first. I think its good.

Mave: Thanks a lot for your help and response!

Best regards
Peter

10th April 2010, 10:13 PM	#2
MaVo diyAudio Member Join Date: Jan 2006 Location: Herne	Generally said, it looks fine. Personally, i try to avoid having a deep cancellation right above the passband of the woofer, as i think it will make the integration with the mains difficult, not even speaking about the horror of realizing that it is a few hz deeper than simulated and cutting into the passband. Although i have to say i never tried such a dip-thing, so this is only theoretically important. With all the tapped horns i have build so far, the high frequency spikes you see in the simulation are not present in the real measurements, so using the dip to reduce the peaks is not necessary. Also, i think none of tom danleys horns use such a dip. EDIT: You can half the S1-S2 segment in length, since the midpoint of the woofer is where S2 is. This should reduce the dip. Also, you could try a little higher compression ratio, ie make the S1/S2 values smaller, maybe down to 300-400, which would equal a compression ratio of 2-3, which should be safe and get you a little more output. Last edited by MaVo; 10th April 2010 at 10:19 PM.

11th April 2010, 12:00 PM	#9
MaVo diyAudio Member Join Date: Jan 2006 Location: Herne	Your last looked better than the first. I think its good. Last edited by MaVo; 11th April 2010 at 12:04 PM.

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11th April 2010, 12:25 AM	#3
letsbangout diyAudio Member Join Date: Sep 2008	A few comments: 1) S3 and S4 will be closer to 2000 or 3000 in reality - your current S4 isn't even the size of one 15" driver. 2) L12 and L34 will probably be a little shorter in reality. All of my designs seem to love a short L34, albeit I work with sometimes less-than-ideal drivers 3) lol @ the WGA crack on your desktop

11th April 2010, 08:06 AM	#4
pk diyAudio Member Join Date: Apr 2003 Location: Aarhus, Denmark	Hi Mavo and Letsbangout, Thanks a lot for your thoughtful suggestions! I will try out a few more simulations with these in mind. Best regards Peter

11th April 2010, 09:43 AM	#6
MaVo diyAudio Member Join Date: Jan 2006 Location: Herne	@ letsbangout: With a mounting depth of 17cm and a diameter of about 38cm the minimum value for S3 and S4 should be 646cm². @ pk: I spoke about reducing the S1 sliders value... but maybe that would need a 4 segment horn to work properly. You could just keep it that way and it would be fine.