2245h in a fireplace

[audiomagnate]

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

[fpitas]

The chimney may work as a transmission line. Good use of an unused fireplace, in any event.

[1audiohack]

What does it sound like outside? :)

Barry.

[SEAWOLF97]

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.

[more10]

All you need now is recording of Santa coming down the chimeny :-)

[audiomagnate]

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.
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.

[cosmos]

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

[fpitas]

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 ;)

[audiomagnate]

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.

[audiomagnate]

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.

[fpitas]

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/hbase/waves/opecol.html

[audiomagnate]

8Hz fundamental, but then there are harmonics of the pipe resonance.

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/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.

[loach71]

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.

[audiomagnate]

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.

[svollmer]

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.

[audiomagnate]

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.

10 x Vas of the driver is the "rule," so that would be 4 x 29 x 10 or 1,160 ft3, close to a 10 ft. cube. If your closet isn't that big you can vent up to the attic, basement, outside or other adjacent space. The best thing about the IB website is their motto, "Hear the bass, bot the box." That pretty much sums it up. I've been building subs for over 40 years (damn I'm old!) but IMO this is the way to go. My next move is to find another 2245 and cut a new baffle.

[NickH]

Does your flue rattle at all?

the reason you don't hear it outside is probably because of the height. Bass is omni directional but only to a point. Your radiation is radiated out in all direction from the plane of the top of the chimney.

[audiomagnate]

Does your flue rattle at all?

the reason you don't hear it outside is probably because of the height. Bass is omni directional but only to a point. Your radiation is radiated out in all direction from the plane of the top of the chimney.

I have run sweeps down to 1 Hz and there are no rattles, except the ones in the room I had to track down. I'm sure if I went up on the roof I could hear it, but from down in the yard I can't hear anything at all, even at fairly loud levels.

To to answer a previous question, it rains a lot here but I've never seen water in the fireplace. Leaves do make it down here and I will fix that by placing a screen at the top of the chimney.

I do plan on getting a second woofer but I'm enjoying my system immensly as it is. Oddly enough, classic rock like Steely Dan is what I'm enjoying right now, not pipe organ or dub step. It's fun hearing these albums I've heard hundreds of times - usually with great conventional subs - the IB way. You don't realize how much box sound subs put out until it's gone. I'm going to have to get my regular mains, modded L200s, down here. The only downside is I get nodes and antinodes in this rather large room, around 20 x 70 feet. My sub swarm is better in that one respect. I may have to strategically locate a conventional sub or two, at a lower than normal level, to fix that. Or I could build some more IB's and into the feed the backwaves into the unfinished part of the basement... Hmm.

[svollmer]

10 x Vas of the driver is the "rule," so that would be 4 x 29 x 10 or 1,160 ft3, close to a 10 ft. cube. If your closet isn't that big you can vent up to the attic, basement, outside or other adjacent space. The best thing about the IB website is their motto, "Hear the bass, bot the box." That pretty much sums it up. I've been building subs for over 40 years (damn I'm old!) but IMO this is the way to go. My next move is to find another 2245 and cut a new baffle.

Thanks! So, my closet is approximately 280SF, but because it's in the basement, I didn't sheetrock the ceiling and the joists provide four 10"x16" (approximately) openings that lead into an adjacent closet. The adjacent closet might get me pretty close to 1,160 ft3. If it does, will that work?

[badman]

Thanks! So, my closet is approximately 280SF, but because it's in the basement, I didn't sheetrock the ceiling and the joists provide four 10"x16" (approximately) openings that lead into an adjacent closet. The adjacent closet might get me pretty close to 1,160 ft3. If it does, will that work?

It's plenty- the rule of thumb is to minimize any box rolloff, you won't see any pertinent rolloff in that sized space

[audiomagnate]

Thanks! So, my closet is approximately 280SF, but because it's in the basement, I didn't sheetrock the ceiling and the joists provide four 10"x16" (approximately) openings that lead into an adjacent closet. The adjacent closet might get me pretty close to 1,160 ft3. If it does, will that work?

Definitely plenty, you just have to make sure the backwave is isolated from the frontwave, and that everything is structurally sound. I also read somewhere that a box as small as 4x Vas acts pretty close to an IB.

[svollmer]

Great; thanks very much to you both.

[bubbleboy76]

Coool idea! The fireplace dvd just tops it up!

[Flaesh]

One you've gone IB, you can never go back to boxes or cardboard tubes..:cheers: phrase isn't original :D.
But place is! :thmbsup:
I think there is quarterwave resonance but enough\very low(??)

[audiomagnate]

I've been playing around with slopes, eq, phasing, power, rear chamber (i.e the fireplace) damping, etc. for the last few months. I'm a little bummed that the best bass isn't located at my LP and moving a fireplace sub isn't an option. Besides that, I am extremely happy with this setup. There was a bit of a peak/resonance at 70 Hz, but that was cured with a steeper slope, and a lower crossover point. I can't hear 10 Hz, but it does something to the house way upstairs somewhere so I know it's putting out sound down to there, which makes me grin for some odd reason (14 Hz used to be my lower cuttoff so it's nice to a little more extension). If you happen to have an idle fireplace that also happens to be located in a good spot relative to your LP, I highly recommend this cheap and easy to implement (and "un-implement" if you have to) setup. The next step might be to add another 2245h as there's just enough room, but I'm pretty happy with things as they are to tell the truth.

[mech986]

wonder if putting a couple of 2245's in boxes and tuning them so they act as bass traps passively (not being run) at the high nodes, or putting in bass traps in the corners so as to redistribute the energy in the room might be useful. Also, wonder if deflector baffling the woofer might redistribute the energy better into the room, or cut off excess energy in a particular direction.

How does your flat screen manage not to essentially shake apart when you drive it so close by?

[audiomagnate]

wonder if putting a couple of 2245's in boxes and tuning them so they act as bass traps passively (not being run) at the high nodes, or putting in bass traps in the corners so as to redistribute the energy in the room might be useful. Also, wonder if deflector baffling the woofer might redistribute the energy better into the room, or cut off excess energy in a particular direction.

How does your flat screen manage not to essentially shake apart when you drive it so close by?

That seems like a real waste of a pair of 2245's. The room is 63 feet in one dimension and not at all regular; I really don't think I need bass traps. What would help is a swarm to even out nodes and anti-nodes, but a swarm of IB's is tough to implement and I don't want to add any boxes into the mix. The TV is more than a foot away from the woofer. Wavelengths in this region are extremely long (20 to 120 feet) so your deflector and vibrating TV comments don't make a whole lot of sense to me (the TV is about 12 inches away from the baffle). The only vibrations I'm getting are very far from the source and structural and audible (by me anyway) only when I sweep down into the subsonic range (10 Hz in particular), so I'm going to stop doing that. The bottom line (pun intended) is that this setup works wonderfully well and is incredibly cheap and easy to implement. This is by far the cleanest, most effortless, unobtrusive, uncolored (not a hint of "thump"), musical bass I've ever heard, and I've been building and buying massive subs and going to shows since 1977. Back in Colorado I had a swarm of 15s and 12s in custom made massive boxes that sounded very nice and probably had more "punch" (and floor impact) but this is much more satisfying, and now I'm thinking "punch" might not be such a good thing. I absolutely love the way this thing sounds. It's totally addictive and puts a huge smile on my face every time I listen, which is way more often that in the past. Visitors just shake their heads and say "wow." It really is that good. I'm becoming an IB (and 24 bit) evangelist. My next move is to simply cut a new baffle and add a second 2245 as well as a second bridged 620B for 1200 watts total. It's probably overkill as I don't listen all that loud but it couldn't hurt.

[dr_gallup]

That seems like a real waste of a pair of 2245's. The room is 63 feet in one dimension and not at all regular; I really don't think I need bass traps. What would help is a swarm to even out nodes and anti-nodes, but a swarm of IB's is tough to implement and I don't want to add any boxes into the mix. The TV is more than a foot away from the woofer. Wavelengths in this region are extremely long (20 to 120 feet) so your deflector and vibrating TV comments don't make a whole lot of sense to me (the TV is about 12 inches away from the baffle). The only vibrations I'm getting are very far from the source and structural and audible (by me anyway) only when I sweep down into the subsonic range (10 Hz in particular), so I'm going to stop doing that. The bottom line (pun intended) is that this setup works wonderfully well and is incredibly cheap and easy to implement. This is by far the cleanest, most effortless, unobtrusive, uncolored (not a hint of "thump"), musical bass I've ever heard, and I've been building and buying massive subs and going to shows since 1977. Back in Colorado I had a swarm of 15s and 12s in custom made massive boxes that sounded very nice and probably had more "punch" (and floor impact) but this is much more satisfying, and now I'm thinking "punch" might not be such a good thing. I absolutely love the way this thing sounds. It's totally addictive and puts a huge smile on my face every time I listen, which is way more often that in the past. Visitors just shake their heads and say "wow." It really is that good. I'm becoming an IB (and 24 bit) evangelist. My next move is to simply cut a new baffle and add a second 2245 as well as a second bridged 620B for 1200 watts total. It's probably overkill as I don't listen all that loud but it couldn't hurt.

Aren't you going to need a second faux fireplace too? :blink: So much for incredibly cheap!

[JeffW]

Anne seems to be very concerned about chimney saftey, she left the same message on another board this morning

http://discussions.probrewer.com/showthread.php?60735-Steam-and-Firebox-Stacks-Through-Attic-Space

Or she's a spammer.

[Champster]

Very cool project. Sorry to jump in so late but I somehow missed the post.

Now you can see why I've become such a fan of Linkwitz Labs LX521.4 (http://www.linkwitzlab.com/LX521/Description.htm). It is an amazingly articulate and coherent speaker system and surpasses anything else I've ever owned. I agree with your open baffle comments. Woofers when they are free to breath, front and back with no cabinet, produce amazing detail. The only drawback, is over driving them. You've hinted at doubling the 2245's. I see your last post is about a year ago. Did you ever do that? Did you use a MiniDSP to help smooth the frequency response and how high of frequency do you run them?

Very cool project!!!!

[maxserg]

Finally someone made it IB on this forum with JBP pro speakers !!!:applaud:

Congrats and enjoy real bass!

[audiomagnate]

QUOTE: Very cool project. Sorry to jump in so late but I somehow missed the post.

Now you can see why I've become such a fan of Linkwitz Labs LX521.4 (http://www.linkwitzlab.com/LX521/Description.htm). It is an amazingly articulate and coherent speaker system and surpasses anything else I've ever owned. I agree with your open baffle comments. Woofers when they are free to breath, front and back with no cabinet, produce amazing detail. The only drawback, is over driving them. You've hinted at doubling the 2245's. I see your last post is about a year ago. Did you ever do that?

Not yet, but I did add a couple of conventional "helper subs" for HT sessions. I haven't bottomed the single yet, but I've come close on 24 bit organ stuff. I've upgraded to L300's and moved the SVA's in the rear for HT BTW.

Did you use a MiniDSP to help smooth the frequency response and how high of frequency do you run them?

Crossover is 12 dB/octave at 50 Hz. No DSP, but the room is huge (63' x 24') with lots of irregularities and well damped so it's pretty well behaved. I've done lots of sweeps and it's reasonably flat over its relatively limited operating range.

Very cool project!!!!

Thanks, once you go IB, you'll never go back!

[Champster]

Good call on adding the subs for HT. There is really no point in overdriving the 2245 and asking it to do a task that it wasn't designed to do. When you're ready, I would encourage you to get your hands on a miniDSP for a couple of reasons. First, it is super easy to set a lower cutoff frequency so that you can really protect that driver. You know how valuable and hard it is to get a 2245 re-coned with a real JBL cone these days. Secondly, the trouble with passive crossovers at these frequencies are the size and cost of the parts. The DSP solution allows ever steeper slopes to transform that driver into a true sub and get it out of the upper frequencies altogether. I use a pair of 2245's in 9cf cabinets with my LX521.4 system and take a slightly different approach at determining the upper frequency of the JBL. The 2x10" seas drivers are wonderful but in the cabinet-less LX521.4, they really start making some shockingly large excursions below 35hz. There is also a sense of loss in acoustic energy as the frequency gets that low, so, to protect them, I use the 2 unused digital channels in the minDSP 4x10HD for a 24db/oct 35hz crossover point and then in the PEQ set a 24db/oct lower cutoff at 17hz. For most program material, the 2245's, honestly, rarely has much to say, but when there is program material in this region, they bring a lot of energy to the bottom end that the 2x10" drivers just really struggle to do on their own. I, too, like organ music and movie soundtracks and, on the occasion when I get into that mood for bass heavy material, the 18"s really show their merit and this allows me much higher volumes and a much more realistic soundstage.

Have fun with your project!

[LowPhreak]

Very cool, magnate. If I'd have thought of this with my old house (had similar fireplace), I might have stayed married! :spin:



On the other hand...:banghead: :D

[audiomagnate]

... Secondly, the trouble with passive crossovers at these frequencies are the size and cost of the parts. The DSP solution allows ever steeper slopes to transform that driver into a true sub and get it out of the upper frequencies altogether...
The 50Hz crossover is electronic, not passive.