This review page is supported in part by the sponsors whose ad banners are displayed below


4/29/09, Pete Riggle to Benjamin Webber, Bill Gau, Bill Woods, Bob Griffith, Bruce Edgar, Chris Brady, Chris Sullivan, Dale Tarrant, David Adams, Doc B., Eric Alexander, Jeffrey Jackson, Francis Chinen, George Kilcyznski, Grant and Carol Emigh, Harry Zweben, Jack Hess, Jaime Marzulli, Jason @ lovecraftdesigns, Jay Fisher, Jeff Day, Joe Burdick, John Hoffman, John Jaffe, Jonathan Weiss, Julie Davis, Kara Chaffee, Kathie & Kevin Walker, Kelly Clare Riggle, Kelly Hower, Ken Hanafin, Kent Layden, Leslie Cain, Lo, Nigel S., Margaret Riggle, Matt Edwards, Mark Hower, Maury W., PR Carter, Perry Riggle, Peter Anderson, Peter Shand, Ralph Henson, Rhonda Riggle, Rich Drysdale, Ron Barbee, Roz Rouse, Scott Kaufman, Steve Schell, Thad Aerts, Tony Peluso & White Mike -
Dear friends and family, please set aside Saturday June 13 for the sub horn construction party in the Garden of Earthly Delights here in Kennewick. The Po’ BoyZ horns are sounding so much more than wonderful, this with a cutoff at 60Hz. Just imagine what will happen when we extend the bass cleanly to 20Hz. 
 

Check the attached images for a reminder of what the sub horn is all about. The horn will live in the loft above the listening room. The horn extends 21 feet along the rear wall of the listening room loft, turns at the end wall and follows that for another 12 feet. The length of the horn along the midline is 29.5 feet. The throat is 12 inches high by 5.5 inches wide. The mouth is 6 feet high by 9.3 feet wide. The horn is exponential with a design flare frequency of 15Hz. The walls and floor of the loft serve as two of the four sides of the horn's rectangular cross section, greatly reducing labor and materials and simplifying construction. The horn will be constructed in segments, most 4 feet long but some 2 feet long and some 3 feet long. Each segment has a top panel and a side panel, the wall and floor forming the other side and the bottom.
 

The sub horn will be constructed of 3/4" flooring grade oriented strand board. It’s a nice dense material and inexpensive. Long panel spans will be braced externally with 2x4 lumber. The plan is to construct the sub horn during the day and party in the evening. This is like a barn raising. The more the hands, the lighter the work. We will form teams of two workers. Two teams will be cutting panels. As many teams as we can muster will be assembling and installing segments. There will be people drilling and people screwing (of course). We will have one or two people running latex caulk guns. The top panels are cleated to the wall. The side panels are cleated to the floor. The top and side panels are cleated together. This is not rocket science. 
 

In advance I have made cutting plans and built a 1/10 scale model from them so I know the cutting plans work. In advance I will have the loft cleared out, the wall and floor cleats installed and the panels marked and identified for cutting. We can sleep a bunch of folks in the Garden of Earthly Delights dormitory style. Also there are the guest bedroom and living room. We can even pitch a few tents if we wish. The Portlanders and Kara from Vancouver are planning to arrive on Friday afternoon, June 12. Old-time road warrior companion Joe Burdick will be here from Denver. Wouldn't it be nice if Peter Shand (or Peter and Kathleen) could join us from Denver? This should be the blast of the decade. So set Saturday June 13 aside and let us know you will be here. Food, beverages and companionship will be abundant. Stephæn and Joe will feed us well. Let me know if you'll be sleeping here at the house/shop. For information purposes, I have included folks on the distribution that will find it impractical to get here. Impractical or not, if you'd like to join us, please do.
RSVP
Pete


PS: Attached are images of a 1/10 scale model of the sub horn. I built the model to verify that the cutting diagrams for the full on project will work. Looks like they will. Friend Kara Chaffee has named the scale model The Little Bighorn.


4/29/09: From Rich Drysdale to Pete Riggle
- Thanks Pete, looking good. I'm going to try to be there. What's your address?
Rich


Comment: This email is from Rich Drysdale, partner with Steve Schell in Cogent True to Life loudspeakers. Apparently at this point, Rich figured we lived in the LA area and he would be able to drop by for the horn raising. Or he was just being funny.


4/29/09: Pete Riggle to Rich, æ & Steve - Rich, great to hear from you. Here’s the address. I don't know if you realize how far away we are from you. I'm assuming you are somewhere in the LA area, maybe Santa Monica. We'd love to have you. You are most welcome and I can promise a good time. Right now we are planning on driving the single sub horn initially with one or two Altec 15" biflex drivers (415C). One of the 415s gives a compression ratio of 2. Two of the 415s gives a compression ration of 4. I know these are not intended as woofers but they are on hand in the shop, reasonably efficient and made by Altec. Also, a friend is offering to ship a pair of Hartley 24" drivers. I think we'd use only one of the Hartleys. I plan to ask Steve Schell about these options. Do you have any related experience that would be helpful? You and Steve have been a huge inspiration to Stephæn and I in all of this. 
Yours,
Pete
 

PS for Steve Schell: Steve, hope this finds you doing well. I was going to email you this evening to ask about the drivers we are thinking about for a first go at the sub horn. Then I got Rich's message and tacked my message on to the reply to Rich. Any reason not to try the Altec 415C Biflex drivers? Any reason not to try the Hartley 24? We will be using a plate amp with a frequency adjustable 12dB low pass.
Yours,
Pete
 

5/12/09: Stephæn to Duke
- Hey Duke, thanks for getting back to me! Check out the note below and pics attached. The pics and story are not ready for sharing yet but I thought you'd enjoy them. As for the note, if you have plans to come this way, come to our sub raising party. Kara Chaffee and Harry Zweben and other good folks will be helping. It will be a hoot!
æ


5/12/09: Duke LeJeune to æ
- Hi Stephæn, thanks for including me in the circle. I consider that an honor. I won't show anyone without your permission. May I show my wife? It'll make her more appreciative of the restraint I've shown. What an awesome project! I have all kinds of envy going on right now.It should be a crime that you can even think about doing this for $190 in materials! Thank you for the invitation. It's possible that I might make it to the Northwest sometime in the next few months. I'm working on some bass guitar cabinet designs and a luthier who has some interest in my work lives in Seattle. If I make the trip I'll give you a holler.
Very best, 
Duke
 
 
Final group email: Dear friends and family, attached are some images provided by Stephæn of the horn-raising project last Saturday, June 13, which resulted in the construction of a 29 foot long sub horn in the loft of the listening room named the Garden of Earthly Delights. The mouth of the sub horn is 9.5 feet wide by 6 feet high. The design is intended to extend the bass of the Po Boy horns down to 20Hz. My heartfelt thanks to everyone who participated. It was a bundle of fun. Those of us who worked on the project were ridden hard and put away wet. That said, it was a lot of fun. Pizza for lunch. Steak and Tandoori chicken for dinner. We got rolling around 10:00 in the morning, had lunch at 2:00 and wrapped it up at 8:00 with the sub horn playing and hit the deck for dinner.
 

Who all worked on the project? Stephæn, Kara Chaffee, Ron Barbee, Joel Riggle, Harry Zweben, Joe Burdick, Ken Hanafin, uncle Bob Olson (senior consultant, kibitzer and cheerleader), Clark Blumenstein and yours truly. The super heroes were Kara, Ron, Stephæn and Joel. Joe and Gloria took care of catering and carrying of water to the thirsty hands. In addition there were various onlookers, curious bystanders—take this how you will—cheering section, kibitzers and peanut gallery, camp followers and celebrants throughout the day and late into the night.
 

There is a lot of cleanup work to do, panel bracing and joint sealing, but the sub horn is now in operation. Preliminary results? Amazing! The sub horn seems to integrate well with the Po Boy horns, providing a rich subliminal bottom end. Even though the sub horn is behind and above the listeners, the subjective aural effect is that the bass seems to emanate from the stereo soundstage. Stephæn suggests that with only 12dB per octave cutoff at the high end of the sub horn (roughly 40 to 60Hz), we are getting some noticeable bleed of the sub horn into the range covered by the stereo speakers, resulting in a little roughness in the crossover range. I think this is correct. The sub horn is driven by a plate amp with 12dB per octave roll-off. We will try to augment this with an additional 12dB filter in the sub horn driver circuit. Come by and check it out!
Yours,
Pete



9/22/09: Bruce Edgar to Pete Riggle - If you are missing the bottom octave, you may have to use sand damping. Go to Home Depot and buy some 50 lbs sack of playground sand and lay one sack on the bottom of the horn mouth just inside the horn. You can experiment with placement of another sack on top of the horn structure. You can also experiment with smaller bags of sand made with large freezer plastic bags. Your horn structure, floor or house structure may be vibrating and damping out the bottom octave. It has happen to me several times. My listening room at home has wooden plywood floors. In my demo rooms at my shops I had concrete floors and the bass was there in spades. I've put them in the bottom of my bass bin and the bass comes in. Take them out and the bass goes away. It's a cheap and dirty trick but it works.


Another thought occurs to me. Have you checked the resonance of your back chamber? Reactance annulling of the throat reactance may not be working. The resonance of the speaker with a sealed back chamber should be at the flare frequency for reactance annulling to work. The horn likes to see a pure acoustical resistance to work properly. At the flare frequency the inertia of the slug of air in the horn acts as a reactance commonly called the throat reactance. The negative reactance of the back chamber will cancel it out. You can check the system resonance with an AF signal generator (continuous tuning, not a switching type with fixed frequencies), a 10K resistor and an AC voltmeter. Connect the 10K resistor in series with the signal generator and the input terminals of the back chamber with the driver installed. Connect the AC voltmeter across the input terminals. The 10K resistor makes this measurement setup work as a constant current circuit. The voltage readings are directly proportional to impedance. You will find that there are several peaks in the impedance curve. That’s normal. Find the lowest peak. That is the system resonance and usually the highest reading. If the main peak is higher than the flare frequency, the back chamber is too high, the chamber itself too small and has to be bigger. If the main frequency is lower, the chamber is too big and has to be smaller. You can place blocks of wood inside to displace volume. If there is a leak you will measure a typical bass reflex impedance curve with two large peaks, one lower and one higher than the flare frequency. You can calibrate  this measurement system in Ohms by disconnecting the resistor and voltmeter from the system and loading it with a 100-ohm resistor. Vary the generator's output until the meter reads 100 millivolts. Now 1 millivolt reads one ohm. Hope this helps.
Bruce Edgar


Comment: Needless to say, Bruce Edgar is a tremendous resource for anyone doing horns. He has shared his knowledge in a way most helpful to DIY folks. For particulars, check out Bruce’s Show Horn article from the "Speaker Builder" days which is now available online.


9/22/09: Pete Riggle to Bruce
- It would be hard to overstate how much I appreciate hearing your thoughts on damping and measurements. Just got the 29' long bass-horn installed in mid June and have been too busy to get down to the brass tacks of measurement and fine tuning. When I do I'll have your notes below in front of me. I'll take some good images of the 29' long bass horn construction and send them to you.
 
Yours,
Pete


Pete Riggle - Hey friends, just wanted to let you know—especially those who have made contributions to the Poboys and/or the big sub horn—that the sub horn is now working very nicely. Since its installation I have been trying to get the sub horn to amaze and haven't been able to do so. The proposition on which my efforts were based was that we wanted the sub horn to do only the lowest notes. So I have limited most of my efforts to a cutoff frequency between 40 and 60Hz. Last week Ron Barbee brought over Bill Wassberg for a listen. Bill is an old pal of Ron and Sumi. He is the guy who went to Sumi's father and asked for her hand on Ron's behalf - Japanese custom, great story. Listening to the system Bill observed that with a lowpass cutoff in the 40 to 60Hz range, we weren't getting much from that big horn up in the loft. After Ron and Bill left I went over to the plate amp and adjusted the cutoff frequency to 160Hz, which is as high as the plate amp will go. Wow! Magic! Thanks Bill.


I propose the following explanation. The wave travel distance from the sub horn driver to the listener is about 40 feet. The wave travel distance from the Jhorn driver to the listener is about 16 feet. This corresponds to a 21ms delay for notes from the sub horn. I'm thinking that with the fundamental coming from the sub horn and the harmonics coming from the Jhorns, fundamental and harmonics are not working as a team. When we let the sub horn do the fundamental and first harmonic, we have a working set. Yes there are some earlier harmonics arriving from the J-horn but at least when we are psychoacoustically looking for the first 8 harmonics to go with the fundamental, there are some timed right.


There may be other explanations. Like the overall frequency response is better with the bass horn running up to 160Hz. What matters is that all the effort put into the sub horn is now paying off. From now on I'm calling it a bass horn. Thanks again to everyone who helped. For those who have listened recently, the sub was below par (another pun). The Poboy system is sounding pretty darned nice at this point, particularly sitting just a few feet closer than before to the near field. Also using a Mac computer at this point, which seems to be more musical than the HP PC it replaces. That's it for now folks!
Pete


To wrap up this portion of the series, here are a few more pix. Please understand that this device was created purely for its functional value and not aesthetics. We never stare at it while listening. Just sayin’. And as Pete mentioned earlier, "this doesn't have to be pretty. It just needs to be stout." Besides, given Pete’s fear of sitting still, he and I already had another project underway, which will be revealed in Part III of the Hornographic Pursuits series. We think its looks will more than make up for the glamour shortcut taken here.

Progress.

Ron does his best grand plié as things wrap up on construction day. Take a bow Ron!

Joe takes a well-deserved nap after a morning of hauling water, running wire and cooking lunch.

Harry shows his pride in mission accomplished.

Leslie, Clark and Ken celebrate success.

Here’s The Monster’s view from the attic.

And here’s the crew listening to the fruits of their labor.

With that, we’ll leave you with a brief image of what guests do see before they take their seats and face the music coming from the mains. Clearly Rocky Raccoon had no fear of the monster and thought it all pretty swell.


I’ll conclude by saying we had big fun. I have three rules in life: love family and friends; have fun; or make money to facilitate the other two. If I’m not doing one of those, why bother doing it at all? So this fits. There may be a bit more finish work to do but that’s gonna be on hold until after we complete the project that will be featured in Part III. Indeed, the unveiling of the Po’ Lil’ Things is just a short time away as they are—physically—already done but still need to be voiced. Stay tuned.
Enlarge!