Page 1 of 3 123 LastLast
Results 1 to 15 of 35

Thread: 2245h in a fireplace

  1. #1
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014

    2245h in a fireplace

    Here we go. It works! The flue is wide open, so it's technically an IB. Fun stuff.
    Attached Images Attached Images   

  2. #2
    Senior Member
    Join Date
    Apr 2011
    Location
    Leesburg, VA
    Posts
    322
    The chimney may work as a transmission line. Good use of an unused fireplace, in any event.
    Oppo BDP-95 DCX-2496 RMX-850 Parasound A21 First Watt J2 Dayton RSS390HF-4 MTM Quads of SEAS W18E001 511Bs TAD TD-2002

  3. #3
    Senior Member 1audiohack's Avatar
    Join Date
    Jul 2007
    Location
    Las Vegas Nevada
    Posts
    2,704
    What does it sound like outside?

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  4. #4
    Senior Member SEAWOLF97's Avatar
    Join Date
    Jan 2006
    Location
    PDX, ®egon
    Posts
    9,108
    I had an old audio book that showed how to mount drivers in closet doors for IB effects.

    and a driver outside the house coming to a horn that filled the interior wall. Pics in some old thread.
    The 50's was a great time for audio experimentation.
    “If you think that’s the dumbest thing you’ve ever heard,
    just wait a couple minutes!”

  5. #5
    Senior Member
    Join Date
    Aug 2010
    Location
    Jättendal (Giant Valley), Sweden
    Posts
    736
    All you need now is recording of Santa coming down the chimeny :-)

  6. #6
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014
    Quote Originally Posted by fpitas View Post
    The chimney may work as a transmission line. Good use of an unused fireplace, in any event.
    What is commonly called a transmission line is actually a 1/4 wave tuned port (like an organ pipe) with sound damping materials along the tube to absorb upper frequencies. A true transmission line slowly absorbs the back wave with denser and denser materials until the wave can be transmitted into a solid material. The end of this tube, the top of the chimney, is open. The chimney has to be resonating at a frequency with a wavelength 4x its length since it's a open/closed tube, but it isn't ported back into the room, so this is functioning like as an IB, not a TL.
    Quote Originally Posted by 1audiohack View Post
    What does it sound like outside?
    Inaudible, I checked. It sounds absolutely glorious inside, and I still don't have the EQ/rolloff/subsonic filter where I want it yet, miniDSP is probably in my future, but a good parametric eq combined with an EC will work too and keep things analog and simpler. The group delay and phase plot for an IB are amazingly good, you are hearing the signal, not the box. You really need more moving area to do an IB properly (four 2245's would be about right), but this works great at moderate levels, the cleanest bass I've ever heard (my first IB) and I've been building subs since the 70's. I've got a bridged BGW 620B driving it, around 500 watts, but I don't want to push it to beyond the Xmax limit. I can't imagine going back to box subs. This really is special.Construction was extremely easy. Materials are a 31" x 49" sheet of 3/4 MDF, a roll of roofer's sealant, some fiberglass for behind the driver, screws and T nuts, and eight masonry bolts, about $60 total. The seal is tight but I don't think it's super critical because there is no pressure buildup. I did remove the damper mechanism to make the path more open and to prevent potential rattles.
    Attached Images Attached Images  

  7. #7
    Unabashed Speakerholic cosmos's Avatar
    Join Date
    May 2007
    Location
    Ohio
    Posts
    297

    Rain Concern?

    Is it possible for the driver to get wet during a storm? Not sure how your chimney is built, but it would be bad if a 2245 got wet.. or critters in the chimney?

    Dan

  8. #8
    Senior Member
    Join Date
    Apr 2011
    Location
    Leesburg, VA
    Posts
    322
    Quote Originally Posted by audiomagnate View Post
    What is commonly called a transmission line is actually a 1/4 wave tuned port (like an organ pipe) with sound damping materials along the tube to absorb upper frequencies. A true transmission line slowly absorbs the back wave with denser and denser materials until the wave can be transmitted into a solid material. The end of this tube, the top of the chimney, is open. The chimney has to be resonating at a frequency with a wavelength 4x its length since it's a open/closed tube, but it isn't ported back into the room, so this is functioning like as an IB, not a TL.Inaudible, I checked. It sounds absolutely glorious inside, and I still don't have the EQ/rolloff/subsonic filter where I want it yet, miniDSP is probably in my future, but a good parametric eq combined with an EC will work too and keep things analog and simpler. The group delay and phase plot for an IB are amazingly good, you are hearing the signal, not the box. You really need more moving area to do an IB properly (four 2245's would be about right), but this works great at moderate levels, the cleanest bass I've ever heard (my first IB) and I've been building subs since the 70's. I've got a bridged BGW 620B driving it, around 500 watts, but I don't want to push it to beyond the Xmax limit. I can't imagine going back to box subs. This really is special.Construction was extremely easy. Materials are a 31" x 49" sheet of 3/4 MDF, a roll of roofer's sealant, some fiberglass for behind the driver, screws and T nuts, and eight masonry bolts, about $60 total. The seal is tight but I don't think it's super critical because there is no pressure buildup. I did remove the damper mechanism to make the path more open and to prevent potential rattles.
    It's still a transmission line, but it may not be tuned where you want it
    Oppo BDP-95 DCX-2496 RMX-850 Parasound A21 First Watt J2 Dayton RSS390HF-4 MTM Quads of SEAS W18E001 511Bs TAD TD-2002

  9. #9
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014
    Quote Originally Posted by fpitas View Post
    It's still a transmission line, but it may not be tuned where you want it
    No it isn't. It's a closed end/open end pipe with a fundamental resonance of 8 Hz (the chimney is 35 feet long). What are marketed as transmission lines in the audio world act as transmission lines for the upper frequencies only. They morph into 1/4 wave resonators at the tuned frequency. Real transmission lines absorb waves without reflection by slowly increasing the density of the transmission media, like a wedge in an anechoic chamber, which goes from zero density at the tip to the solid wall of the structure at the fat end of the wedge.

  10. #10
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014
    Quote Originally Posted by fpitas View Post
    It's still a transmission line, but it may not be tuned where you want it
    No it isn't. It's a closed end/open end pipe with a fundamental resonance of 8 Hz, outside the audio range and way below the subsonic filter anyway (the chimney is 35 feet long). What are marketed as transmission lines in the audio world act as transmission lines for the upper frequencies only. They morph into 1/4 wave resonators at the tuned frequency. They dump that out of phase resonance back into the room. Mine puts the (non-existent) fundamental resonance outside where you wouldn't hear it even if it did exist. The third harmonic is around 24 Hz, so that MIGHT be significant, but it doesn't seem to be as the level of the third is much lower than the first, and it's behind the closed baffle anyway.

    Real transmission lines absorb waves without reflection by slowly increasing the density of the transmission media, like a wedge in an anechoic chamber, which gradually goes from air density at the tip to the density of the solid wall of the structure at the opposite end of the wedge.

  11. #11
    Senior Member
    Join Date
    Apr 2011
    Location
    Leesburg, VA
    Posts
    322
    Quote Originally Posted by audiomagnate View Post
    No it isn't. It's a closed end/open end pipe with a fundamental resonance of 8 Hz (the chimney is 35 feet long). What are marketed as transmission lines in the audio world act as transmission lines for the upper frequencies only. They morph into 1/4 wave resonators at the tuned frequency. Real transmission lines absorb waves without reflection by slowly increasing the density of the transmission media, like a wedge in an anechoic chamber, which goes from zero density at the point to the solid wall of the structure.
    8Hz fundamental, but then there are harmonics of the pipe resonance.

    http://hyperphysics.phy-astr.gsu.edu...es/opecol.html
    Oppo BDP-95 DCX-2496 RMX-850 Parasound A21 First Watt J2 Dayton RSS390HF-4 MTM Quads of SEAS W18E001 511Bs TAD TD-2002

  12. #12
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014
    Quote Originally Posted by fpitas View Post
    8Hz fundamental, but then there are harmonics of the pipe resonance.

    http://hyperphysics.phy-astr.gsu.edu...es/opecol.html
    Yes pipes have resonances, transmission lines don't. The level of the third, is much lower than the 1st. The level of the fifth is even lower, and in the range of the upper cutoff frequency anyway.

  13. #13
    J.A.F.S.
    Join Date
    Aug 2005
    Location
    Back in the audio lab.
    Posts
    382

    Nelson Pass' subwoofer project

    Quote Originally Posted by audiomagnate View Post
    Yes pipes have resonances, transmission lines don't. The level of the third, is much lower than the 1st. The level of the fifth is even lower, and in the range of the upper cutoff frequency anyway.
    You may want to examine Nelson Pass' subwoofer project plans -- 'El PipeO'
    It would work well with qty. 4 JBL 2245Hs. It is easy to build -- using Sonotube and some MDF.
    Amazed I'm still alive!
    Tim

  14. #14
    Senior Member audiomagnate's Avatar
    Join Date
    Jan 2011
    Location
    Colorado and Georgia
    Posts
    1,014
    Quote Originally Posted by loach71 View Post
    You may want to examine Nelson Pass' subwoofer project plans -- 'El PipeO'
    It would work well with qty. 4 JBL 2245Hs. It is easy to build -- using Sonotube and some MDF.
    One you've gone IB, you can never go back to boxes or cardboard tubes. If you haven't heard an IB setup, you owe it to yourself to hunt one down and give it a listen. Check out the Cult of the Infinitely Baffled website for more info.

  15. #15
    Senior Member svollmer's Avatar
    Join Date
    Dec 2004
    Location
    Northern VA
    Posts
    584
    I have four 2245H's in four 10 cubic foot boxes stacked in a closet next to my room. In the room, you can only see the front of the boxes. I desperately wanted to do them as IB's, using the closet as the cabinet, but alas, it didn't have enough volume according to an IB website calculator I used at the time (pretty sure it was the Cult of IB).

    If anyone has an IB sub in the Washington metro area, I'd love to hear it and learn if I can actually get rid of those boxes.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Jbl 2245h
    By BillR in forum Lansing Product Technical Help
    Replies: 5
    Last Post: 04-23-2010, 10:59 AM
  2. Box for JBL 2245H
    By Niklas Nord in forum Lansing Product DIY Forum
    Replies: 4
    Last Post: 04-22-2003, 01:45 PM
  3. Box for JBL 2245H
    By Niklas Nord in forum Lansing Product General Information
    Replies: 4
    Last Post: 04-22-2003, 01:45 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •