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Old 10th October 2012, 04:53 PM   #1
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Default Hitting 20Hz cheaply...

Hi guys,

The bug has bitten again.

I've got some rather nice bookshelf speakers (2-way FAST with a FE126eN and a TB W6-1139 per side, biamped).

They'll hit 40Hz, but I'd like more right at the bottom end for movies and the like.

So, the logical solution is a subwoofer.

I've come across threads where a JBL car sub (or two) has been used in a tapped horn-style enclosure, and wondered where that might take me.
I have access to the GTO1214 (seems to be the popular one), and have played around with TQWPs in Hornresp, as I can't get a decent result when trying tapped horns.
I can get 120dB to ~20Hz (corner loaded) from either a ported box or a TQWP. In fact, the ported box appears to go a little louder. However, I am suspicious of the Xmax ratings for these drivers, so I doubt they'll hit 120dB.

Power isn't a huge issue - I'll be using my bass guitar amp (once I've bypassed the 30Hz low-cut) that'll swing 200v p/p @8ohm when bridged. Long term power would be more like 3-500w, but the headroom's nice to have.


So, a few questions.

Are the JBL car subs worth playing with?
For those of you that have played with them, how far can you push them before they start putting out harmonics?


I'd like to hit 20Hz clean in a small room. Will a single 12" be sufficient? (I expect so, but would like confirmation either way)

Now, room placement isn't something I can play around with - it'll be in the corner of the room, underneath my desk.
The maximum size I'd accept is around 150L, but smaller would be better: I've been toying with the idea of throwing away maximum SPL by going for a small sealed cabinet with plenty of eq. I know this probably wouldn't get the most out of the driver, but I'd save of money (and time) by getting one of those prefab 35L sealed cabinets.

Guidance would be much appreciated

Chris
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Old 10th October 2012, 05:45 PM   #2
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Make sure you also model a normal ported design to compare with your T-QWT. You may be suprised. Also, any tapped design has group delay at crossover that will require time correction, the mains will need delay.
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Old 10th October 2012, 06:14 PM   #3
jbell is offline jbell  United States
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since you are mating up with bookshelf speakers, I assume refrigerator size cabinets are out.

Check the thread on avs and grab the hornresp inputs.. but I think lilmike's 25hz insubnia works with the jbl804 when built 8" internal width... don't remember for sure, and too lazy to search.... I know I've built one without the bottom fold for a MCM 55.2421..

Reed Exodus Anarchy 25hz Tapped Horn
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Old 10th October 2012, 09:19 PM   #4
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Quote:
Originally Posted by chris661 View Post
Hi guys,

The bug has bitten again.

... TB W6-1139 per side ...

Chris
If my memory serves me correct I managed to get 24hz-1db or so out of the W6-1139. It is possible to go that low with no eq with this driver in the correct enclosure.

Very impressive sound for the size. But as they say "There's no replacement for displacement", although the W6-1139 can pump some air, and it takes abuse too. If you want to build something like that you need to depend on room gain though, or the FR will run away from it SPL wise.
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Old 11th October 2012, 01:32 PM   #5
eXa is offline eXa  Norway
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Since you mentioned GTO1214

Build your own 2x12" TH (The Kraken 212 TH)

There is the Kraken 212 with 2 of them, and the kraken 112 with 1 GTO1214 and the Kraken 210 with 2 GTO1014
The plans for the 112 and 210 is on page 10

Last edited by eXa; 11th October 2012 at 01:36 PM.
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Old 11th October 2012, 02:25 PM   #6
eXa is offline eXa  Norway
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And Kraken 112 with 19mm panels on page 12...
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Old 11th October 2012, 08:35 PM   #7
tvrgeek is offline tvrgeek  United States
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#1 What music do you have that reaches 20? 25 to 30 is fine unless you listen to heavy organ or distorted special effects.
#2 120 dB at 20 and the word "cheap" do not mesh.
#3 120 dB at 20 Hz. I hope you live at least a mile form anyone else, or they will be very upset with you.
#4 120 dB at 20 Hz, you will need it louder as you will have no hearing in no time.

A lot of people seem to go for deep and loud bass forgetting totally about distortion. One more problem that means not cheap. It makes a bigger difference than most understand.
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Old 11th October 2012, 08:40 PM   #8
DrDyna is offline DrDyna  United States
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Originally Posted by tvrgeek View Post
#1 What music do you have that reaches 20? 25 to 30 is fine unless you listen to heavy organ or distorted special effects.
Here we go again.
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Old 11th October 2012, 08:42 PM   #9
tvrgeek is offline tvrgeek  United States
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#5, A single sub in the corner is very problematic, as it is a different distance from the sub to the mains. This means you will have phase nulls no matter what you do. The steeper the crossover the better you will do. B3 won't cut it. LR4 closer, but I would go for LR6.

#6 In the corner means yo will gave a lot of room gain. Be very careful thinking you want a flat response from crossover down. You don't. This is like I prefer low Q ( .5 or so) sealed subs. They flat work better in a real room.

#7, I will never give up my old 830500's because of their low distortion. I drive them with a Parasound HCA series amp. Yes, it made a difference.
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Old 11th October 2012, 08:45 PM   #10
tvrgeek is offline tvrgeek  United States
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Originally Posted by DrDyna View Post
Here we go again.
Yup. Valid question yesterday, still valid today. How many people have actually run their music collection through a spectrum analyzer with a hold feature? I have. I'll stand by my 30Hz number.
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