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Old 7th October 2008, 10:56 PM   #2361
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Thanks Steve,

The build looks great. I'm looking forward to the HornResp data and (hopefully) some dimensions.

Both William Cowan and Chris have made 20Hz subs. Is your's the third, or am I forgetting someone?
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Old 8th October 2008, 11:27 AM   #2362
JLH is offline JLH  United States
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Quote:
Originally posted by Don Snyder
Thanks Steve,

The build looks great. I'm looking forward to the HornResp data and (hopefully) some dimensions.

Both William Cowan and Chris have made 20Hz subs. Is your's the third, or am I forgetting someone?

I built this 20Hz tapped horn subwoofer. It was banned from the house by She whom must be obeyed. For some reason the wife got upset when one of her antique english tea pots rattled off its shelf and smashed into pieces. Anyway, since the Tang Band W8-740C woofers are 4 ohms I decided to wire them in series and give my amplifier an easier time. Also, I had to add a 2.5mH inductor to flatten the response some. The woofers are arranged in a distortion reducing push-pull configuration. One woofer’s magnet is inside the compression chamber, and the other is outside. Looking at picture #2, you can see that the woofer that would be mounted on the left side would have its magnet outside. I really like how this type of push-pull can make the Dumax behavior much more linear. I think its coolest trick is how low frequency SPL waves can massage your pants leg. The amount of output from this thing was ridiculous and lead to it being banned from the house. Every once in a while when the wife is gone, I carry it back into the house and play it.


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Old 9th October 2008, 01:44 AM   #2363
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JLH,

Cool design! I wouldn't mind trying that cabinet layout with a pair of high excursion 12" Hollywood DVC x4 ohm each car woofers I saved from a snowbank.

Care to share your cabinet dimensions?
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Old 9th October 2008, 01:50 AM   #2364
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Thanks for the kind words guys! I may have gone a little overboard with the bracing, but I was having fun playing with my new tools. One thing that is nice though is that the sub is silent (no rattles or other mechanical noises when producing 25-15hz signals. In contrast my VMPS subs made a fair amount of noise doing these test. However I never noticed anything when playing movies/music.

I just finished running some frequency sweeps in RoomEQwizard and even though my sub is crossed at 80Hz, 100hz from the sub is just as loud as the bandpass signal. In other words, that 100hz peak that HR shows is real. It was my intention to use a Behringer DSP1124P Feedback Destroyer to kill that peak and eq the sub a little. I know other people have reported that HR exaggerates the peaks, so I though I should mention it. I guess it could be a room mode though.

This sub still continues to impress. I watched LOTR ROTK the other night and compared to the VMPS, it's just so much more accurate. The TH seems like it's producing less boom and overhang. This sub has impact! Hits are very solid and weighty, but since there's less boom, the sub kind of sound quieter if that makes sense; less overall energy, but more information.

Anyway, here are the HR FR plots in 1/4 space (pi). My rough sketch build plan is based on a baffle/external wall height of 450mm.

Please note that I'm very new to DIY audio and while I'm happy with the overall result in my room, I'm sure there's lots of room for improvement. Basically I had some very specific requirements for size and frequency response, otherwise I would have just copied someone else's design . I've been following this thread for about a year now, so thanks to all who posted/helped and also thanks to Mr Mc Beans fantastic software. And last, but not least I think we all can appreciate a wife that'll tolerate such an absurd room to speaker ratio! So thanks Mrs Steve71!
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Old 9th October 2008, 01:52 AM   #2365
steve71 is offline steve71  Australia
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FR plot in 1/4 space
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Old 9th October 2008, 02:01 AM   #2366
steve71 is offline steve71  Australia
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Here is the rough build plan.. sorry Brett, this wasn't really meant to be understood by anyone but me.. and even then only for a brief period. D

If you have any questions, just let me know. Obviously this build plan doesn't take into account the internal baffle thickness. And as I said before the baffle/wall height is 450mm.
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Old 9th October 2008, 09:00 AM   #2367
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Quote:
Originally posted by steve71
Here is the rough build plan.. sorry Brett, this wasn't really meant to be understood by anyone but me.. and even then only for a brief period. D

If you have any questions, just let me know. Obviously this build plan doesn't take into account the internal baffle thickness. And as I said before the baffle/wall height is 450mm.
Thanks for that Steve, it's great.
I can't get HR to run with Vista and won't be going to XP Pro for a month or so and have drivers, wood and a new sawbench and want to play.

Cheers
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Old 9th October 2008, 12:23 PM   #2368
JLH is offline JLH  United States
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Quote:
Originally posted by rcavictim
JLH,

Cool design! I wouldn't mind trying that cabinet layout with a pair of high excursion 12" Hollywood DVC x4 ohm each car woofers I saved from a snowbank.

Care to share your cabinet dimensions?

The overall dimensions are roughly 17" deep X 16" wide X 6' tall. Of course if you want to use a different woofer, you'll have to redesign for the T/S parameters of that woofer. Unless you are DJing outside gigs, I really don't know what you would do with the output of a dual 12" version of my tapped horn. The dual 8" version is already too much for home use.
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Old 9th October 2008, 12:55 PM   #2369
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JLH,
How high can you run this TH?
Can it be used with a slow roll off past (into) the spikes that start @ 60Hz?
(I need a TH that goes up to 80Hz to mate with 85% 65Hz mid bass horns, we had emailed earlier about using 4012HOs).
Thanks,
Robert
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Old 9th October 2008, 03:14 PM   #2370
JLH is offline JLH  United States
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Quote:
Originally posted by serenechaos
JLH,
How high can you run this TH?
Can it be used with a slow roll off past (into) the spikes that start @ 60Hz?
(I need a TH that goes up to 80Hz to mate with 85% 65Hz mid bass horns, we had emailed earlier about using 4012HOs).
Thanks,
Robert

No, you can't run this one up past 60Hz. The Definimax 4012HO is a better tapped horn for reaching up to 80Hz - 100Hz. I find that with low sensitivity speakers like the Tang Band, you will have a restricted bandwidth. However, with higher sensitivity speakers like the 4012HO, you end up with more bandwidth before things get ugly in the higher frequencies.
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