If I am not listening to movies, how low do I really have to go??? - Page 2 - diyAudio
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Old 4th October 2012, 11:52 PM   #11
tvrgeek is offline tvrgeek  United States
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I listen to a wide variety of music. Jazz mostly I find goes into the 30's quite a bit. Even some folk music I thought was happy at 60, when I added a sub to my office I was surprised what was there. I would say 40 minimum, 30 better. About the only thing lower that that are special effects and heavy organ, which I don't listen to.
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Old 5th October 2012, 01:26 AM   #12
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Originally Posted by djn View Post
Hi Welter. how do I change the Fb (Enclosure resonance)? In WinISD, if I change the tuning freq for my box and driver, the response starts to roll off above 100hz.
Djn,

The driver Fs remains the same regardless of Fb, Fb will remain the same with any driver put in the box.

To lower Fb, lengthen the port(s). Fb can also be lowered by putting an inner “Top Hat” on the existing port, a speaker cut out can be used, cut a port sized donut hole in the cut out and put it over the inner end of the port.

Rounding the port ends reduces chuffing.

Simulations often disagree with actual tunings.

The actual Fb can be determined by putting a white dot on the cone, and sweeping a sine wave tone through the speaker. The cone movement will be at minimum at Fb.

While it is not advantageous to use a Fb below Fs for PA use, acoustically small rooms provide LF “cabin gain”, so tuning lower than simulations may still provide a relatively flat LF response.

Art Welter
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Old 5th October 2012, 03:24 AM   #13
djn is offline djn  United States
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Thanks Art. I hear the term "room gain" or "cabin gain" a lot when discussion LF. Is that independent of room treatment like bass traps or absorption panels?

Also, I am thinking about using adjustable length tubes on the outside of the cabinet just for easy of adjustment. Does it matter if the port tube is outside or inside the cab?
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Old 5th October 2012, 03:37 AM   #14
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Might be a good idea to stick to a sealed box and eq it to get what you want. With a box placed near the wall room gain will lower the f3 frequency though you need to check this in your room. Moving the box around will change the lift due to room gain. You can alter the Linkwitz filter to get a curve to match your driver/box/room.

One way to get your room gain identified might be to get the free field response of a sealed sub ( small one might be OK ) and then place it where you desire in your room and get a response at your listening position. The difference would be the gain you can expect. You could then eq it the way you want.
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Old 5th October 2012, 01:46 PM   #15
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by djn View Post
Thanks Art. I hear the term "room gain" or "cabin gain" a lot when discussion LF. Is that independent of room treatment like bass traps or absorption panels?
Hi,

In the room 'pressure zone' no but depends on the size of 'panel areas' and the effective BW to the total room area.

Bass traps can be effective in the room modal region: Acoustic Treatment and Design for Recording Studios and Listening Rooms

Quote:
Also, I am thinking about using adjustable length tubes on the outside of the cabinet just for easy of adjustment. Does it matter if the port tube is outside or inside the cab?
That is practically the only way a Diy'r can figure out correct port lengts and yes it matters as the end correction factor depends on how the port is terminating.

For a simple BR box design:The trick here is to cut the lenght for a chosen Fb then recalculate or make the port somewhat shorter and test when flush to the baffle.It's an itreative procedure.

Important is also to check the large port signal behaviour as its very different from a small signal view.

b
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Old 5th October 2012, 02:42 PM   #16
johnr66 is offline johnr66  United States
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After building a lot of boxes, I find with most music, tuning my ported boxes to around 35hz works best. I have an odd way of doing it. I select drivers and model the box to 27-30Hz, but shorten the port for a 35Hz tuning. This creates a bump in the range where the bass feels powerful, but not in the boomy range (70Hz+).

For sealed "hifi" designs, I select a driver with a low fs of around 20hz and put it in a box so the Qtc is around .7. This allows for a sealed design that can hit the low notes and has good extension.
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Old 6th October 2012, 01:35 AM   #17
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well, after looking into the linkwitz trans thing, a guy had better results with 1 driver with a passive radiator compared to 4 of the exact same drivers in a small box but eq'd. I think cone motion reduction is the key there.

I'm still tempted for an easy dual 15 push pull sealed box.
11ft3 = qtc .707 = F3 /fsb of 31hz
dayton rss390hf

That's deep for an un-augmented sealed.



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Old 6th October 2012, 06:00 AM   #18
djn is offline djn  United States
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Hopefully I have the system back up and running Sunday. Measurements to follow.
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Old 7th October 2012, 03:10 PM   #19
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Originally Posted by johnr66 View Post
After building a lot of boxes, I find with most music, tuning my ported boxes to around 35hz works best. I have an odd way of doing it. I select drivers and model the box to 27-30Hz, but shorten the port for a 35Hz tuning. This creates a bump in the range where the bass feels powerful, but not in the boomy range (70Hz+).

For sealed "hifi" designs, I select a driver with a low fs of around 20hz and put it in a box so the Qtc is around .7. This allows for a sealed design that can hit the low notes and has good extension.
1. Smart man with experience. +1

2. The ancient AR-3 was pretty flat on the curve going low but with a bit of boom around 37 Hz. Provided all the good quality bass you'd want and to this day, I can recall the delightful experience of hearing the organ pedals in St. Saens' 3rd Sym in 1967 (Munch, Boston??).

3. There always are trade-offs and choices. Going super-low is silly because there is almost no music down there and better to trade-off for smooth and clean curve (meaning you should use sealed boxes or OBs). Go for quality.

4. To answer your question, download free signal analysis software which will give a frequency analysis plot of your music as you play it. Do you see bumps at the bottom of the bass on your computer screen that your speakers aren't playing? Or, to tell the truth, do you see much of anything below 35 Hz?

5. I have dozens of organ CDs and they contain a few seconds of sound below 30... maybe. Even when your speakers don't play down there, your ears hear it anyway. As anybody ought to know. Granted, your sternum doesn't feel it.

B.
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Last edited by bentoronto; 7th October 2012 at 03:15 PM.
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Old 8th October 2012, 12:33 PM   #20
DrDyna is offline DrDyna  United States
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Originally Posted by bentoronto View Post

4. To answer your question, download free signal analysis software which will give a frequency analysis plot of your music as you play it. Do you see bumps at the bottom of the bass on your computer screen that your speakers aren't playing? Or, to tell the truth, do you see much of anything below 35 Hz?
This is why it's a tricky question. "much of anything below 35 hz" is an idea that audio guys have been lugging around for a long time because for many years, there really wasn't much down there except for organ music, which is why we see statements like this. "Well, if you're not listening to organ music..."

The truth is, in a lot of modern music, electronic in particular, we see tons of information below 35 hz. Sometimes, lots of it, and more as time goes on.

Just playing around for a few minutes, here's a few examples.
Attached Images
File Type: jpg bt - godt - 20hz.jpg (110.2 KB, 107 views)
File Type: jpg burial - broken home 26hz.jpg (121.4 KB, 108 views)
File Type: jpg burial - etched headplate - 19hz.jpg (122.1 KB, 105 views)
File Type: jpg distance - my demons 27hz.jpg (118.2 KB, 103 views)
File Type: jpg porter robinson - unison knife party-lol.jpg (115.4 KB, 103 views)
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