Hi Everyone, Cheryl here

I joined this forum a little while ago but have only been browsing for the most part.

I have an apartment home theater composed of used/repaired components and bedding for sound absorption. Screen, projector, height and wide speakers plus absorbers are attached to wall header plates from heavy duty shelving brackets (popcorn ceiling is useless for mounting). I fabricated or repaired many of the components but I did not build any electronics or speaker systems. Most of the fabrication consisted of drilling and cutting steel and aluminum for the various mounts and stringing nylon cords to hang the wides in basketball nets, plus I had to fabricate 4 steel bar outriggers for the surround towers, one each, since the originals were missing (probably broken, they are plastic). The AT screen dangles off the ends of long heavy shelving brackets.

amirm helped me with some of the debug. Still fine tuning but things are good in here now, except for the screen.

It is pretty crowded in here with 6 towers, 4 bookshelves, and a center plus dual subs. This is a smallish abode. The bedding is all black and covers the entire front (dead) wall. Design goal was cost minimization so almost everything was bought used.

Projector: BenQ HT1075
Mount: Chief RPMA on a short shelf just below the ceiling (nice mount BTW)
Screen: Elite '1080P' (not) AT 100" that needs replacing with a real screen, maybe DIY retractable tensioned AT with quality fabric
TV: older Samsung 46" LCD
Tuner: Samsung OTA
Stand: OmniMount glass/metal (originally for rear projection style)
Receiver: Onkyo TX-NR929
Digital AM/FM Radio: Sony XDR-S3HD
Amp: Crown ComTech 210 (for wides channels)
Speakers: Sapphire/TSC (Infinity co founder Cary Christie designed them)
3-way MTM ST2x2 fronts,
3-way MTM ST3x4 surrounds,
2-way SBx4 heights and wides,
2-way horizontal WTW SC center
Subs: 2xSVS PB10-NSD/ISD (one of each)
Turntable: Technics linear tracking moving coil 12"x12" that plays upside down
Cassette (yes I still have one): Yamaha 3 head
Blu Ray: Sony w/ wireless streaming
HTPC: 2xIntel Core2 Duo boxes running Ubuntu with 30TB NFS between them

Separate system with one HTPC and Sapphire/TSC speakers in the bedroom, currently 5.1 but I have enough speakers to go to 9.1. The TV is a 42" Panasonic plasma with the dreaded floatng black level. I am looking into the fix that is now available but it might not work on my TV since it was made in 2007.

Total investment in both systems is approximately $6000/$7000 USD, depending on whether I count pieces that are no longer in use or repurposed toward other systems in my son's home. That investment includes the living room furniture modular leather sofa and end tables. I also invested in several other Onkyo receivers with flaky/failed HDMI that I am gradually restoring to functionality with capacitor replacements. Those receivers are in use by my son and daughter and in my bedroom plus my neighbor is using one of them too.

Front wall of my living room system is on long dimension for wide sound stage and because the other dimension has sliding door on one end and kitchen/dining on the other. Three layers of comforter (two old ones that were laying around) in the middle of the wall plus two rows of pillows across the front corners with shams pinned together like sausages. The only rear corner also has a string of pillows hanging across/down the corner to the AC/heater unit. The build was quick cheap and easy, the way I like it.

Using Audyssey XT32 since it is my best option with a very dead room without adding significant cost. Favorite sound modes: Neo:x Music or Movie with Audyssey 'Music' (flat), DEQ and DV enabled most of the time, surrounds backed off 2dB. Sounds really good in here now (to me anyway).

My background is in electrical engineering. Before that, I did some solar photovoltaic, water, and heating, plus geothermal. Most of the work was residential but if you google the Gardner, Massachusetts Electric / Mobil Solar joint demonstration project you might get a glimpse of the panels I helped install on the Mount Wachusett Community College and a couple dozen residential homes. With the right address you can probably see a couple of streets' worth of homes all lined up in the neighborhood sporting the panels, with 27 out of 30 installations still operating nearly 25 years later last time I checked.

I have been an amateur musician since high school, playing primarily electric bass, but for the past couple of decades not so much anymore. Got busy, got older, lost physical endurance etc. and have just been coasting although I recently met another bass player in a band (my neighbor) and he invites me to his gigs. We also watch TV together on my system or his since we live close by. Nice to have someone to share it with.

Hearing brickwalls at 12KHz now, so I am very sanguine about all the pro audio hype. Useless to my ears now basically. I still dabble anyway. Keeps me from being bored.

As a teen I designed and built a 400W bass amp / stereo amp in bridged mode / quadraphonic amp in discrete mode. I used it exclusively for a number of years as my main system and just packed it up for gigs. I also assembled a quadraphonic mixer from old stereo PCBs, op amps, reverb coil, plus added a Space Invaders sound chip test circuit as a sort of synthesizer to the box. Did a few recordings with the equipment, solo, before getting busy with being a serious person. It was fun.

I also designed a 20WPCx4 car 'power booster' (remember when they were called that?) plus adapted a portable cassette machine to the car system.

I guess you could call me an audio buff, or an audio buffoon, on a small scale anyway. Everyone in my family except my mom has/had a technical degree, electrical x 3, programming, chemistry. In progress: my daughter is doing chemistry and my son is doing psychology. I guess we are all nerds.

So hello everyone and thanks to all of you who maintain this site. You are appreciated.

amirm said:

HI Cheryl. Good to read your full background. I would add that you personify the word frugal when it comes to audio. And put performance ahead of looks more than anyone I know . All admirable characteristics.

But did you say you did geothermal? I have actually built a low-grade geothermal to heat my greenhouse. I will document it at some point and would love to get your feedback.

Click to expand...

Yes I did help install (but not specify or design) a single geothermal system with heat pump and storage tank. In the early 1980s geothermal was mainly just a pipe dream (bad pun intended). Is your geothermal using a deep well or something else? The one I actually worked on was a deep well that was not needed for drinking water so we pulled the pump out and stuck in a long PVC pipe loop with a tight U bend at the end.

I was at the bottom of the chain of command. Not sure I have much insight to offer on any level but you are welcome to my rambling insights for whatever they are worth.

Phelonious Ponk said:

Hello Cheryl. I think most of us here are probably brick-walled at 12khz (or less), but hope springs eternal. I know, after 40+ years of playing in rock bands, anything remotely audible and above 14khz is just a distant memory...

Tim

Click to expand...

Hello Tim,

After 40+ years of anything after high school, just about anyone can have hearing loss by that age.

DaveyF said:

Hello Cheryl. Finally, someone who can hear the dreaded "ringing" that I have been complaining about in so many metal domed tweeters

Like Tim has stated above, most here are "probably brick-walled at 12khz or less".....

Click to expand...

Yet we still argue about inaudible things such as the sound of parents screaming at their kids to clean their bedrooms.

amirm said:

It is an unconventional "low grade geothermal." You dig a deep trench and put in a few hundred feet of 4 inch drainage pipe. A fan then takes air from inside the greenhouse, runs it through the pipes and it comes out the other end. In winter the soil temp is much higher than air so it heats up the greenhouse that way. In summer, it will do the reverse. It is a low efficiency system due to use of air but the cost is very minimal to run since all you need is a fan.

I finished most of my system already and it was fun watching it suck 75 degree air and have it come out at 55 at the other end! That was the good news. The bad news was the amount of static pressure in the corrugated pipe. What came out the other end was a trickle of what was going in. So I put in two more pipes but have not tested it much. I seemed to help as it reduced the impedance mismatch.

There is next to nothing as far as scientific literature out there. People doing it are the random people on the web. I needed help figuring out whether this was all junk science or there was something to it. Fortunately I have a tractor so digging up the trench while a lot of work, was free. And the pipes cost about $300. So if it doesn't work, I am not out much money. But if it does work, and is able to extract heat/cooling out of the ground, it will be quite nice.

Click to expand...

For solar greenhouse it is common to have direct solar storage such as slab or gravel on the ground inside and toward the north, storage that has optionally been thermally decoupled from the earth with insulation. It is not so much a geothermal system as it is a thermal storage system that extracts heat from the storage at night to keep the plants from freezing. This is the most popular way to manage greenhouse thermals because it can be completely passive or have varying degrees of pumping and automation. Usually a backup system is required.

Geothermal does not require a backup and IMO it is also a better approach if done right although the aesthetics are usually not as nice as warm stone-paved gravel storage. No reason not to have both in one greenhouse though.

Earth berming the entire residence is another option, although it can be a pain to have to plant the walls with ivy to keep them from washing away. Some residences are nearly completely buried and others are 'envelope dwelling' where the entire building is surrounded by a separate shell with geothermal circulating through the air gap. Superinsulation works very well and is the most efficient way to condition a living environment, probably the future of humanity IMO once we stop making toxic consumer household goods and building materials. Fresh air intake with air-to-air heat exchange to conserve heat can help with that to some extent.

Actually, to tell you the truth I am astonished that such systems as yours are not commonplace or even mandatory. Putting an air duct underground with an optional heat pump is the simplest and cheapest way to extract free energy. It can be put directly underneath or adjacent to almost any dwelling. Prehistoric human cave dwellers used geothermal so it cannot be that hard to figure out.

The hardest part is keeping fungus out of the system. With a heat pump it is also necessary to prevent freeze-up of the evaporator.

The best way AFAIK is to draw your airflow from outside environment, as long as your sink can handle that thermal load, but you still might want to investigate methods of drying and filtering the air stream to prevent problems especially in the summer. Drawing the air from outside adds the benefit of a constant ventilation stream that can be used to pump air contaminants out of the greenhouse (methane and ammonia and fungus come to mind).

Sorry, I only did the one deep well system so my experience is not going to help you much. You need to make such decisions on your own based on better info than I have.

I did get to see several greenhouse installations with varying degrees of sophistication though so I have some general background but probably not even equal to what you can find online today. In the 1970/80s the Northeast was far more progressive than California or Florida in terms of alternative energy and there were many wonderful innovations. I will take a look through my library and see if I have any old references hanging around. Most of the books I bought are decades old so they might not even be up to date on current tech or best practices.

There were many printed references on alternative energy available during the Carter presidency. I suspect there may be a sort of modern-day renaissance going on with the global warming scare and global economy run amok. People seem to be trusting 'the system' less and becoming more independent in their thinking again.

One of the most difficult aspects of a greenhouse is optimizing its efficiency. It is a complex system, with a biological component. That requires some ingenuity and a good deal of experience is essential for optimal performance plus you have to keep on top of it or it can get out of control quickly.

It is difficult to estimate let alone measure the biological efficiency of a greenhouse but ultimately the biological efficiency is what you are really after, unless you are also planning to use its heating and cooling capability to supplement your residential HVAC in which case you have an even more difficult optimization problem.

The plain truth is that such greenhouse systems are a labor-intensive PITA that require an able body, lots of time for planning/construction/operation, and a dutiful regularity that people like me are basically incapable of providing (Black Thumb is my organics screen name).

No sane city dweller or suburbanite gets within a thousand miles of operating a greenhouse on a serious level because the amount of work and savvy is exceptional so there is little market for commercially installed residential systems let alone DIY references for building your own. Most residential greenhouses are only a hobby for the suburban gardener rather than an integrated part of the house/HVAC.

For simplicity I am going to call your buried pipe a 'sink' even though it can also be a source.

I am not expecting answers to all these questions, but these are the questions you should be asking yourself:

Are you hoping to extract useful residential heating and cooling from the sink, or will it only serve the greenhouse? Is the greenhouse attached to your residence? Is the shared wall insulated? Does the greenhouse share the residential ventilation system via windows or doors or ducting with/without blower? Does the greenhouse have external ventilation via external windows and doors, or ducting/blower/turbine? Automatic/insulated window coverings? Automated watering system? Moisture sensors?

Ammonia/methane sensor? Not even sure if anyone uses such sensor but I know that bacterial decomposition is a potential problem in greenhouses, along with fungus, especially if you run a year-round composting bin inside or you tend to over-water.

What latitude do you live at? What is your local building code demanding for the depth of a foundation or water pipe to get it below the frost line? How deep is the duct that you buried in your sink? What is your target/measured flow rate through the sink? Is the temperature of your sink constant and if not what range does it vary over the seasons? What is your BTU/hr (pick any convenient unit) capability/requirement from the sink and how does it change over the seasons? Do you risk condensation in the sink? Can you dehumidify the sink and/or use outside air to keep it dry?

Ideally you want the sink well below the frost line for the system to function properly in the winter. Ideally it should be a constant sink temperature at the outlet and if it is relatively shallow it should be insulated on the top so it couples deeper into the ground but then the total sink area might need to increase also since half the coupling surface is blocked by the insulation.

You have a choice of using the system with or without a heat pump.

With no heat pump, the ground temperature is always the target output temp and the usefulness is reduced unless you need cave temperature year round or you are prepared to use an alternate mechanism for heating.

If you only care about keeping the plants alive and healthy through the night then a simple sink fan that runs continuously is fine as long as the total BTU capacity of the sink will keep the temperature above about 40F on your coldest winter day but of course that depends on what you are growing in there. With a 55F sink temperature that is not so easy to do, especially if the sink temperature decreases in the winter, or the outside air is very cold, or there is no movable insulation on the glazing, and even worse if the air flow through the sink is restricted.

It is probably a good idea to take some measurements and do some calculations. If you ever sized a heat sink and fan for a transistor then you already pretty much know what to do but there are also online references to calculate these things for you (I am guessing but it seems improbable that they do not exist anywhere). You need to do a min/max thermal analysis that takes into account all the paths including through the walls, through the glazing, through the ground, fresh air flow, automated insulated blind failure and geothermal failure worst case etc. to know what your risks are, especially risk to the plumbing.

It can be quite nice to have freshly oxygenated air with an organic smell to it circulating through your entire home. The key is careful design of the thermals and careful management of the organics. You already pointed out that the available references are minimal so you are basically re-inventing the wheel unless you hire a consultant. The lack of standardization means it is very difficult to compare approaches too. Pretty much every alternative energy system is a custom install to some extent and as you can see now from me just running things off the top of my head there are lots of considerations and options.

As long as you manage any compost properly and use moisture sensors for the irrigation you should not have problems with ammonia but you need to keep an eye on that or the smells can really mess up the living space. Count on it happening at least once, probably while you are away on vacation during a power failure or system breakdown, especially if your appointed caretaker is novice or nonexistent. Expect to come home to a disaster.

You can add active heater capability to your existing geothermal air system with an in-wall air conditioner used in reverse but you will need a system control unit that senses the condenser loop temperature rather than the evaporator loop. Strong air flow though the sink is essential so count on beefing up the blower considerably with HVAC style squirrel cage blower. You might also need to protect the evaporator from freezing up with the water vapor, either by thermal design or with a freeze sensor that disables the compressor.

If you want a custom design with substantial physical separation between the evaporator and condenser you can use standard central air conditioning parts run in reverse but in the USA you need a refrigeration license to legally buy the freon and to legally charge the system with freon. All the same fungus and freezing considerations apply.

You should probably consider doing some quick calculations and tests of your sink so that you know its limitations (ideally you do this step before installation). There must be current references available somewhere, they existed in the 1980s anyway even if only in college thermodynamics texts.

There might be off-the-shelf solutions for the heat exchanger and control unit. You should investigate those too.

Air systems and water systems function very similarly, but the required hardware is a little different.

The control system for a heat pump can be quite complicated if you also have to switch ducting circuits around, say into three possible circuits, each activating on set points and mode settings that you control (fresh air intake on the sink is assumed):

1) Cooling mode bypasses the heat pump and exhausts the fresh air drawn through the sink into the living space
2) Heating mode 1 bypasses the heat pump and exhausts the fresh air drawn through the sink into the living space
3) Heating mode 2 pipes the fresh air drawn through the sink into the evaporator and exhausts it to the outside air

Well I hope this helped you out some. It has been a very long time since I even thought about such things.