15hz subsonic filter

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jmalbright

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Joined: February 10, 2008

Location: Texas, United States

Posted: May 11, 2008 at 11:05 PM / IP Logged

Does anyone know where I can get an external 15Hz subsonic filter? The lowest I have been able to find is 20Hz offered by harrison labs. I could probably make a 20Hz filter work, but would much prefer one at 15Hz.

haemphyst

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Posted: May 12, 2008 at 10:37 AM / IP Logged

Why do you feel you need one that low? By the time you get to frequencies THAT low, your enclosure will be as big as your entire CAR, with ports 3 feet long, and as big as your driver's side window...

20Hz should be fine for nearly ANY application, yes, even a TL.

Fill us in, with a little more info regarding your application.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

jmalbright

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Joined: February 10, 2008

Location: Texas, United States

Posted: May 12, 2008 at 11:21 AM / IP Logged

The enclosure I am going to build will have a volume of 1.35 ft^3 tuned to 27Hz. Yes, the port is long, around 31" @ 4" diameter. The driver I am using is a Diamond Audio D910D4. I am running that off of a MTX Thunder 6500D which I should be getting 775 Wrms from.

I modeled this setup using winisd with 2nd order 20Hz & 15Hz subsonic filters. Here are the results.

20Hz:

15Hz:

I wanted to find a 15Hz filter because the response looks better to me. It's not that different though which I why I said I could probably use a 20 Hz filter and be OK.

I currently have this woofer in a box tuned to 45Hz with a 30Hz subsonic filter and I have to say that I'm not very happy with the way it sounds. I'm much more into sound quality and deep bass than SPL. To this end, I was considering doing a TL, but I don't think I can afford the space it would take to build a proper transmission line enclosure.

Btw, I have made a tentative design of my ported box. Accounting for the internal port and subwoofer volume, the complete volume of the box needs to be 1.75 ft^3. So, I was looking at making a box (3/4" MDF) that had exterior dimensions of: 21"L X 13.5"H X 14.5"D.

DYohn

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Posted: May 12, 2008 at 12:15 PM / IP Logged

You're looking at less than -1db difference. This is the same thing as NO difference in a non-SPL-comp system.

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jmelton86

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Posted: May 12, 2008 at 7:24 PM / IP Logged

You really should get one at 25Hz, seeing as your box is tuned to 27.

My box is tuned to 26.6Hz, and i'm getting a 25Hz ssf.

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stevdart

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Posted: May 12, 2008 at 9:22 PM / IP Logged

I was just about to agree with jmelton, but...with tuning as low as 27 Hz you're likely not going to need a subsonic filter at all. How much music material playing through the source will enter that realm of frequencies?

I would build the system without the SS filter. Then, instead of testing with tones in the lowest subsonic frequency range usually reserved for home HT setup, play music through the car's system that you know to be truly dynamic and unusually low ( the synthesized sub bass in some material ). Watch the cone as it hits those lowest freqs. That will tell you if you need to put a filter on it.

If the cone wobbles incoherently, I agree that 20 Hz is the lowest filter you should try.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

jmalbright

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Joined: February 10, 2008

Location: Texas, United States

Posted: May 13, 2008 at 10:40 AM / IP Logged

stevdart wrote:

When I built the box I have now (tuned to 45hz w/ a 30hz subsonic filter) I didn't think cutting off the lower frequencies would make much of a difference. However, after having a sealed enclosure prior to the one I have now, I notice a substantial difference in the low-end extension between the two setups.

It would be nice not to have to worry about a subsonic filter at all, but the model I got from winisd predicts that over-excursion will start to be an issue around 24Hz. I just don't want to damage my woofer as a result of myself being too cheap to get a subsonic filter because I really can't afford to replace the sub at this point.

jmelton86

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Posted: May 13, 2008 at 8:02 PM / IP Logged

The lowest H/P filter I have in my system is @ 32Hz, so that's what I use -until I order my F-Mods @ 25Hz.

I did play the system with no ssf and with the 32Hz ssf after I installed my new box. I didn't really notice much more cone movement with no ssf, and the sub didn't bottom out on "Bass, I Love You'' cranked up. But I, like you, cannot afford another sub. This is the only reason I use one.

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DDX470HD GTO14001 GTO1014D (x3)

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15hz subsonic filter

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