Grassroots Home Theater

If you weren't so far away, I'd tell you to come on over and we'll build one. I have all the panels cut, another driver, and the amp. Not only do I not need another sub, I don't have room for a second one.

DrBoost wrote: If you weren't so far away, I'd tell you to come on over and we'll build one. I have all the panels cut, another driver, and the amp. Not only do I not need another sub, I don't have room for a second one.

Dammit dont say that!!

jj wrote: So how does the theory work with the sub? How do you know what frequency to tune the box for? Is it the speaker fz? Also I'm curious how this enclosure does with xmax. Does it really flex the driver? Cool design and looks great BTW!

The horn is built around the T/S specs. If you search for picowrecker someone posted the parameters needed to model your particular driver to see what it'll do. My cabinet is tuned to put out a pretty flat output, 98 dB at 14 Hz to 103 dB at 100 Hz. I've not measured it yet, but I don't doubt that for a minute.
As far as xMax, the issue is the same as any horn, or 4th and especially 6th order enclosures. If the driver is bottoming out, it'll be harder to hear. But.....this cabinet is soo efficient I'm only pushing.....150 watts into it I'll never reach xMax with soo few watts. To be honest, I wouldn't mind a few more, but I bet I can tune the room and change parameters to boost output just a bit more.
This will give you an idea of how efficient it is. Before, I had two Infinity Kappa Perfect 10.1s. Each with it's own 150 watt monoblock, each with it's own sealed enclosure. After moving into the theater and setting the speakers up I started the room correction program. It immediately told me I had to reduce the subwoofer output before it would complete the calibration!
You asked about the theory.
The driver is mounted with the front of the driver (positive pressure wave) into the small throat of the horn. The size of the horn and the taper are calculated so by the time the cone has traveled back and is creating the negative pressure wave, the two waves meat up, timed so they don't cancel each other out, but they give you a boost in output by about 6 dB. That's the same as quadrupling your amplifier!
The drivers this box is designed around are readily available and cheap.

Hornresp. That's a program like WinISD but for horns.

So I just watched my first movie at an elevated volume with with some critical listeners in the room. We watched Cloverfield. WOW!!
That movie will put your system, especially your subwoofer, through a serious workout. I had to open the closet door at the back of the room. The subwoofer was building enough pressure in the room that it was pushing and pulling the door against the latch! It wasn't booming or muddy. Just clean, and very deep.
I really like the Magnepans the more I listen to them. They aren't in your face like a lot of other speakers, they don't try to impress with shrill highs or anything. They just make sound.
I don't know if this will make sense, or if I'll come off as a pretentious dork, but I'll say it anyway. When you stop "auditioning" the speakers, or actively listening to them, and just sit back and enjoy, they disappear and there's a stage in front of you. It's really amazing. Like I said, they don't blow you away at that first note, but they just do everything right. Like an early miata. Not fast enough to scare the muscle-car enthusiast neighbor you have, but take it on a winding road or an autocross course and you realize just how great the little car is.

The funny thing is, I ran the receiver's Audyssey room calibration program when I set things up. After the movie I went in there and made some adjustments because, you know, I'm smarter than a top-notch program
I ended up changing EVERYTHING back except the sub level, I kept that a whole 0.5 dB higher haha.
Audyssey is amazing. I looked at the measurements it had for my speaker distances, they were spot on, within 1/10th of a foot.
So, if anyone wants to build a HT on a grassroots budget, it can be done. I have as much wrapped up into the room as most guys have in 2 or 3 of the seats they use.

Great to hear! Nice that all your work paid off.

I've been looking at Building the sub and with some selective parts scrounging, is almost as cheap as a mate to my Dayton Audio SUB-1200

DrBoost wrote: If you weren't so far away, I'd tell you to come on over and we'll build one. I have all the panels cut, another driver, and the amp. Not only do I not need another sub, I don't have room for a second one.

OK, I'll bite and I'm not so far away. I'm in Beverly Hills, MI and have been looking at subs for a while to complement my HT system. You serious about that offer? What type of costs for components that you have (amp, driver, panels, etc)?

Thanks Todd

Curious as to which receiver your running? (model #?) im searching CL for a used one....

VWguyBruce wrote: Great to hear! Nice that all your work paid off. I've been looking at Building the sub and with some selective parts scrounging, is almost as cheap as a mate to my Dayton Audio SUB-1200

Do it. You will not be disappointed. The build isn't complicated, just remember to add internal bracing, there aren't any in the plans.

wawazat wrote:

DrBoost wrote: If you weren't so far away, I'd tell you to come on over and we'll build one. I have all the panels cut, another driver, and the amp. Not only do I not need another sub, I don't have room for a second one.

OK, I'll bite and I'm not so far away. I'm in Beverly Hills, MI and have been looking at subs for a while to complement my HT system. You serious about that offer? What type of costs for components that you have (amp, driver, panels, etc)? Thanks Todd

Shoot me a IM, or PM, or whatever they are called here. I'm in Fenton, so it's not very far really.

I can't say exactly the cost for what I have in the sub, because I can't find the amplifier I have. It's a Soundstream M1 monoblock. Soundstream is big in car audio and I think this was the attempt to break into home theater. It's THX certified and high quality. It's only 150 watts. Doesn't seem much, but I think the sub design being as efficient means that's plenty of power. I think Carver sold the same amp, rebadged.
The driver is an Infinity Kappa Perfect 10.1.
The box takes 1 1/4 sheets of plywood, add in less than $100 for a new driver from Madisound, paint, terminal cups and you're there.

java230 wrote: Curious as to which receiver your running? (model #?) im searching CL for a used one....

Pioneer Elite SC-05. I'll admit to being a total snob and turning up my nose at the name Pioneer. But the Elite is like AMG is to Mercedes or the M cars are to BMW. It has NO problem at all with 4-ohm loads.

I went to madisound and they were excellent folks. Highly recommend them. I plan on buying from them again.

DrBoost wrote:

java230 wrote: Curious as to which receiver your running? (model #?) im searching CL for a used one....

Pioneer Elite SC-05. I'll admit to being a total snob and turning up my nose at the name Pioneer. But the Elite is like AMG is to Mercedes or the M cars are to BMW. It has NO problem at all with 4-ohm loads.

Thanks, I have an older Yamaha now, but I have had an 80's or maybe older elite in the past, It was a very nice unit. I really like the sound of the auto tuning on the new ones. They are still $$ on CL though. There is one of the lower end VSX-30's for a reasonable price though...

Since im derailing your thread anyway, have a GRM budget suggestion for a sub amp?

RossD wrote: I went to madisound and they were excellent folks. Highly recommend them. I plan on buying from them again.

Madisound is great. Not everything there is expensive, and some deals are really, really good.
I'm Thinking about. 2.1 Bluetooth project for our computer. They've got some nice stuff that's tempting me right now....

java230 wrote:

DrBoost wrote:

java230 wrote: Curious as to which receiver your running? (model #?) im searching CL for a used one....

Pioneer Elite SC-05. I'll admit to being a total snob and turning up my nose at the name Pioneer. But the Elite is like AMG is to Mercedes or the M cars are to BMW. It has NO problem at all with 4-ohm loads.

Thanks, I have an older Yamaha now, but I have had an 80's or maybe older elite in the past, It was a very nice unit. I really like the sound of the auto tuning on the new ones. They are still $$ on CL though. There is one of the lower end VSX-30's for a reasonable price though... Since im derailing your thread anyway, have a GRM budget suggestion for a sub amp?

No suggestion off the top of my head, but try Accessories4less The prices they have are insane. They don't carry everything, but I've seen 75% off more than once.

DrBoost said:

I can't believe this project isn't done, life has been getting in the way. But it's time for another update.
I started the subwoofer build.
I really, really wanted to build a transmission line sub, but there's no proven formula to get it right, and I don't have the time and money to build multiple boxes, that's some expensive trial and error.
I decided on a tapped-horn style cabinet. It's much more complicated, in the design, and build phase, than a sealed, ported, 4th, or 6th order box. When done right, it's pretty amazing. Basically, the size of the throat (small end), mouth (big end) and the length of the horn time things perfectly so when the positive pressure wave travels through the horn it will meet up with the negative pressure wave at the same time. Instead of the waves canceling each other out, you get a 6 dB boost in output.
6 dB might not sound like much, but to increase the output of any speaker by 10 dB, you have to double the input power! So a 6 dB input for free is just too hard to resist. Here's a pic of the box with the side panel off.

It's not done yet, so I don't have any listening impressions, but it is designed to put out 98 dB at 14 hz and stay pretty flat all the way to 100 hz (103 dB) (1 watt/1 meter).

I approve and am totally envious of your project...let me make one correction to something you said here that will help put things in perspective for folks that dont understand the value of 6db....first of all, 6 db works out to DOUBLING the power. Its like the difference between a 300 watt amp and a 600 watt amp. 9 db is doubling the power and then adding half again to that, so if you are starting with a 300 watt amp, add 6 db you are now at 600 watts, another 3 db is another 300 watts. So now you are at 900 watts. One more db is just a little more... 10 db is really a LOT more than 6 db....at least in absolute numbers. Its funny how logrithmic numbers work. And I really want to hear/feel this sub...any chance I could get a copy of its design????