The usual reasons. A sonotube sub is lighter and stronger than a MDF or plywood sub of the same weight. Whenever possible I use sonotubes for subs.
These subs are MASSIVE. Their footprint is less than one square foot, but they're EIGHT FEET tall. If I built the same thing out of MDF they would be almost unbearable to move.
Also, I live in a three story house, and the idea of hauling three 100lb subs up the stairs isn't too appealing
These subs are MASSIVE. Their footprint is less than one square foot, but they're EIGHT FEET tall. If I built the same thing out of MDF they would be almost unbearable to move.
Also, I live in a three story house, and the idea of hauling three 100lb subs up the stairs isn't too appealing
~100 lbs isn't my idea of 'massive', but I always had a cheap hand-truck for heavy and/or awkward size loads such as my ~245 lb speakers (less drivers), which I have moved by myself up/down stairs before a car accident ended such endeavors.
Anyway, the way I've dealt with your problem is to buy a second one to mount the baffle at each end, trimming off the large side so the seams can easily be sealed up, then glue it up and slide it down the other tube and add the end caps.
GM
Anyway, the way I've dealt with your problem is to buy a second one to mount the baffle at each end, trimming off the large side so the seams can easily be sealed up, then glue it up and slide it down the other tube and add the end caps.
GM
I've been working on this for a few weeks, and I just came up with THE PERFECT SOLUTION!
The problem with a sonotube tapped horn is that the board has to be ABSOLUTELY airtight. When the inside dimensions are small, it's practically impossible to get your arm inside to seal things.
But how's this for a solution:
Cut four discs. Each disk is the EXACT size of the sonotube. So if the sonotube is 10.5", each disk is 10.5". Then you cut the discs down the middle, and attach them to the center board. By doing this, the discs will insure that the sonotube is PERFECTLY cylindrical. And that will solve the problem with gaps between the board and the sonotube.
See, the reason there are gaps is that the sonotube isn't perfectly cylindrical. The discs solve that. In addition, they also reinforce the sub in a big way.
Of course you would have to cut holes in the discs, otherwise they would turn your tapped horn into three six sealed chambers.
The problem with a sonotube tapped horn is that the board has to be ABSOLUTELY airtight. When the inside dimensions are small, it's practically impossible to get your arm inside to seal things.
But how's this for a solution:
Cut four discs. Each disk is the EXACT size of the sonotube. So if the sonotube is 10.5", each disk is 10.5". Then you cut the discs down the middle, and attach them to the center board. By doing this, the discs will insure that the sonotube is PERFECTLY cylindrical. And that will solve the problem with gaps between the board and the sonotube.
See, the reason there are gaps is that the sonotube isn't perfectly cylindrical. The discs solve that. In addition, they also reinforce the sub in a big way.
Of course you would have to cut holes in the discs, otherwise they would turn your tapped horn into three six sealed chambers.
In a strange turn of events, my 2nd tapped horn threw itself off the deck of my house, plunging fifteen feet in the process. This is the first time I've seen a subwoofer commit suicide. Sure, I've murdered a few subwoofers, but never seen one kill itself. I woke up on Saturday morning, couldn't find my tapped horn, only to see it's crumpled body laying in the weeds in front of my house.
Sad really.
Sad really.
The Gedlee Summas sure look a lot better than my subwoofer. As you can see in the picture, the finish is like a mirror. You can see the reflection of my front yard on the speaker, via the window beyond the speaker.
Tapped horn is in the corner; audio video cabinet in front of it.
I placed a 18sound waveguide there to give you a sense of scale, the Summa waveguides are easily twice as big.
I need to finish two more subwoofers, and carpet them.
Tapped horn is in the corner; audio video cabinet in front of it.
I placed a 18sound waveguide there to give you a sense of scale, the Summa waveguides are easily twice as big.
I need to finish two more subwoofers, and carpet them.
Since my 2nd tapped horn commit suicide, I built a pair of bandpass boxes to replace it. They're fairly similar to the boxes I considered on page two of this thread. I built two instead of one since the tapped horn should be much more efficient (and bigger!)
So here are some thoughts on a tapped horn versus a bandpass, using the same woofer:
The first thing I noticed was that the bandpass is more efficient. Which was quite a shock, I was expecting the tapped horn would be a good 3-6db louder. I didn't measure the response, so it's possible that the difference was psycho acoustice, due to fletcher munson curves. Because the tapped horn was *definitely* playing lower than the bandpass.
The second thing I noticed was a buzzing present in the bandpass that was mostly absent in the tapped horn. Both enclosures are quite inert, so I'm guessing that this buzzing sound is either 2nd or 3rd harmonic distortion, or a pipe resonance in the bandpass. It's a sound I've noticed in every bandpass box I've built, going back for years. It's not obvious once you turn on the main speakers, since they mask it. But it's quite prominent when listening to the subs alone.
To make a long story short, the tapped horn sounds pretty darn good. The bandpass box is much MUCH easier to build, but there's definitely something special about the TH.
Having said that, the bandpass IS easier to build, and the tapped horn doesn't appear to have an efficiency advantage over the bandpass. Of course in-room measurements should be done to confirm this.
Also, I checked the tuning frequency of the bandpass, and it's tuned a few hz too high, which gives it an additional DB of output.
I'll fix that in the next few days.
So here are some thoughts on a tapped horn versus a bandpass, using the same woofer:
The first thing I noticed was that the bandpass is more efficient. Which was quite a shock, I was expecting the tapped horn would be a good 3-6db louder. I didn't measure the response, so it's possible that the difference was psycho acoustice, due to fletcher munson curves. Because the tapped horn was *definitely* playing lower than the bandpass.
The second thing I noticed was a buzzing present in the bandpass that was mostly absent in the tapped horn. Both enclosures are quite inert, so I'm guessing that this buzzing sound is either 2nd or 3rd harmonic distortion, or a pipe resonance in the bandpass. It's a sound I've noticed in every bandpass box I've built, going back for years. It's not obvious once you turn on the main speakers, since they mask it. But it's quite prominent when listening to the subs alone.
To make a long story short, the tapped horn sounds pretty darn good. The bandpass box is much MUCH easier to build, but there's definitely something special about the TH.
Having said that, the bandpass IS easier to build, and the tapped horn doesn't appear to have an efficiency advantage over the bandpass. Of course in-room measurements should be done to confirm this.
Also, I checked the tuning frequency of the bandpass, and it's tuned a few hz too high, which gives it an additional DB of output.
I'll fix that in the next few days.
I just double checked the models, and it looks like the bandpass should have an F3 of 28hz & 70hz, while the tapped horn has an F3 of 18hz & 70hz.
So that confirms what I was hearing, the TH is playing much lower.
Having said that, the efficiency claims of the TH seem hard to believe; according to hornresp the TH is *12DB* more efficient than the bandpass. It doesn't sound like that at all. Also, the bandpass is exactly 1/2 the size.
So that confirms what I was hearing, the TH is playing much lower.
Having said that, the efficiency claims of the TH seem hard to believe; according to hornresp the TH is *12DB* more efficient than the bandpass. It doesn't sound like that at all. Also, the bandpass is exactly 1/2 the size.
Patrick Bateman said:
John
I am guessing this is turbulence. I am very careful to radius every corner in the ports as not doing so will create a turbulent noise that can be objectionable. I also often use foam in the port to quiet them down. The "smallish" ports on a bandpass are its Achieles Heal.
You comparison is not really fair since the bandpass in the same volume as the TH would go as low. I would expect the two devices to be quite comparable at these very LF in comparable volumes, etc. 12 dB more output from the TH is rather absurd.
Dr Geddes,
I've become accustomed to this buzzing sound in every bandpass I've built, assuming that it was a pipe resonance or perhaps mechanical noise from the woofer. But I trust your advice so I went and took a look.
First I took a look at the port, and there *was* a lot of turbulence. Which was a surprise, as the computer model indicated that my port was adequate. It turned out the turbulence wasn't from the port, but the SEAL on the port. In my haste I hadn't caulked the seal, and a TON of air was escaping through the seal.
That eliminated 25% of the buzzing, but the tapped horn still sounded more relaxed, while the bandpass buzzed away at the same power levels.
I noticed that the subwoofer was rattling quite a bit on my wood floors, so I pressed my entire weight against the cabinet, while the sub was playing. The idea was to keep it from bouncing off the floor.
And THAT solved the problem!
This buzzing sound was radiating from the end caps of the sontube! Honestly, the difference was night and day. So the woofer was turning the plywood end caps into a 10 inch passive radiator, on both sides of the subwoofer.
I am seriously kicking myself right now, because I've heard this distortion in every damn bandpass I've built for over a decade. If only I'd caught this years ago.
Once I placed some weight on the bandpass sub, to fix the problem with the end caps, the bandpass sub sounds *completely* different. It sounds a couple of DB less efficient, but also appears to be playing deeper, and there's isn't rattle or a buzz to be heard. It's very VERY clean, definitely cleaner than the tapped horn now.
Next up, I'm going to reinforce the heck out of BOTH subwoofers.
I've become accustomed to this buzzing sound in every bandpass I've built, assuming that it was a pipe resonance or perhaps mechanical noise from the woofer. But I trust your advice so I went and took a look.
First I took a look at the port, and there *was* a lot of turbulence. Which was a surprise, as the computer model indicated that my port was adequate. It turned out the turbulence wasn't from the port, but the SEAL on the port. In my haste I hadn't caulked the seal, and a TON of air was escaping through the seal.
That eliminated 25% of the buzzing, but the tapped horn still sounded more relaxed, while the bandpass buzzed away at the same power levels.
I noticed that the subwoofer was rattling quite a bit on my wood floors, so I pressed my entire weight against the cabinet, while the sub was playing. The idea was to keep it from bouncing off the floor.
And THAT solved the problem!
This buzzing sound was radiating from the end caps of the sontube! Honestly, the difference was night and day. So the woofer was turning the plywood end caps into a 10 inch passive radiator, on both sides of the subwoofer.
I am seriously kicking myself right now, because I've heard this distortion in every damn bandpass I've built for over a decade. If only I'd caught this years ago.
Once I placed some weight on the bandpass sub, to fix the problem with the end caps, the bandpass sub sounds *completely* different. It sounds a couple of DB less efficient, but also appears to be playing deeper, and there's isn't rattle or a buzz to be heard. It's very VERY clean, definitely cleaner than the tapped horn now.
Next up, I'm going to reinforce the heck out of BOTH subwoofers.
Here's the details on the bandpass sub. It's stupid easy to build. I put two of them together in under six hours with nothing more than a jigsaw, a drill, and a handsaw. One sub is about 80% complete, the other is about 50%. It is easily 10x easier to assemble than the tapped horn, which is MUCH more difficult to build than I realized.
First off, the bandpass sub requires modifications to the MCM 55-2421 woofer. In a nutshell, I add mass to lower the FS and raise the QMS, then I add a resistor to raise the QES. These modifications make it work much better in a single-reflex bandpass.
The front chamber of the sub is 15.8 liters.
The rear chamber of the sub is 34.1 liters.
The front chamber has a vent which measures 22" in length and 3" in diameter. The volume of the vent is 212."
The rear chamber is sealed; the woofer is in the rear chamber, and takes up 113".
The total volume of the front chamber, including the port, is 1176" (964" + 212").
The total volume of the rear chamber is 2194".
I juggled all the numbers so that this sub needs exactly ONE sonotube
The rear chamber is 31" in length; the front chamber is 17" in length. Note that you'll have to use a 180 degree turn to fit a 22" port into a chamber that's 17" long. No, I didn't factor in the volume of the front cap and the end cap, but it certainly wouldn't make more than a half DB difference
First off, the bandpass sub requires modifications to the MCM 55-2421 woofer. In a nutshell, I add mass to lower the FS and raise the QMS, then I add a resistor to raise the QES. These modifications make it work much better in a single-reflex bandpass.
The front chamber of the sub is 15.8 liters.
The rear chamber of the sub is 34.1 liters.
The front chamber has a vent which measures 22" in length and 3" in diameter. The volume of the vent is 212."
The rear chamber is sealed; the woofer is in the rear chamber, and takes up 113".
The total volume of the front chamber, including the port, is 1176" (964" + 212").
The total volume of the rear chamber is 2194".
I juggled all the numbers so that this sub needs exactly ONE sonotube
The rear chamber is 31" in length; the front chamber is 17" in length. Note that you'll have to use a 180 degree turn to fit a 22" port into a chamber that's 17" long. No, I didn't factor in the volume of the front cap and the end cap, but it certainly wouldn't make more than a half DB difference
gedlee said:
I wonder if some of the shockingly high SPL numbers that people are getting with their tapped horn simulations are due to everyone assuming perfect corner loading with their simulations? Did you see this post:
http://www.diyaudio.com/forums/showthread.php?postid=1488070#post1488070
This project has definitely made me re-evaluate what's important in a subwoofer design. Off the top of my head, here's what I think at the moment:
- The tapped horn is a very cool design for prosound, where absolute maximum SPL in the smallest and lightest package is king.
- Tapped horns in the home are a bit silly - they're just more trouble than it's worth. They're too damn difficult to build. As I see it, why spend an extra three weeks building subwoofers, when I could work a few more hours AT MY JOB and just buy a bigger amplifier?
- Bandpass subs are MUCH easier to build, smaller, and they have distortion killing mechanisms which are comparable to a tapped horn.
- I tried half a dozen different dual-reflex simulations, and kept coming back to single reflex. Theoretically dual-reflex will offer greater bandwidth, but the size of the ports just gets out of control. It all comes back to what your time is worth. Would you rather spend three times as long building a box, or just spend a few extra bucks on a bigger amp? The only way I could make a dual reflex perform better than a single reflex was by using extremely long ports, and it got to the point where the cost of the PVC pipe and elbows would be more than the subwoofer!
- Once I fixed the buzzing end caps, the bandpass easily sounds cleaner than the TH. Of course it's only fair to make the same evaluations about the TH enclosure, which I intend to do.
Box construction is a very important aspect in any design. So many people just don't do the structure right. I make my boxes so that all the sides are nearly equal in size and nearly square - this minimizes the surface area for a given volume. Then internal bracing in the right places and I "usually" don't have a problem. Where I have had endless problems is with the plate amps - most of them are built like toys - even the "top-line" models and tend to vibrate like crazy. I usually end up hot melt gluing everything in sight right off the bat just to avoid the problems down the road.
"Corner loading" is a completely misused concept as it can only exist in a room of infinite volume - all opposing walls are at infinity. In a finite sized room "corner loading" becomes "modal loading" and then we are back to multiple subs as the only real solution.
"Corner loading" is a completely misused concept as it can only exist in a room of infinite volume - all opposing walls are at infinity. In a finite sized room "corner loading" becomes "modal loading" and then we are back to multiple subs as the only real solution.
The sobering conclusion I came to after working on this project was that a tapped horn is pretty darn cool IF maximum SPL from a given enclosure size is your number one goal.
I can really see why these are a fantastic option for prosound, because an extra one or two DB per cabinet could be the difference between lugging around six subwoofers for a show instead of six. A tapped horn is also incredibily attractive if you're using a woofer with loads of excursion and a high power voice coil. The distortion-masking mechanisms in a TH would make a TH sound audibly superior to a vented box at high power. For instance, the MTX and Eminence woofers that Danley uses are damn near ideal.
But for the home?
Three or four small subs will sound more natural. My house, like a lot of new construction, is hyooooge. Yet I have no idea where I'd hide three or four tapped horns. Even if I figured out where to hide them, I'd have to re-construct the listening room to deal with that much bass I think. I'm mystified when I see people building eight cubic foot tapped horns, when three or four subs would give you comparable SPL, sound better, and they're cheaper (if you use inexpensive woofers.)
At this point I'm running two subs, with one more to finish, and I might go to four.
When I turn on the second sub, my ability to "localize" the subs is diminished greatly, which is one of the greatest benefits of using multiple subs.
In my experience, the biggest complaint that people have about their subs is that they're too easy to localize.
The use of multiple subs addresses that nicely.
I can really see why these are a fantastic option for prosound, because an extra one or two DB per cabinet could be the difference between lugging around six subwoofers for a show instead of six. A tapped horn is also incredibily attractive if you're using a woofer with loads of excursion and a high power voice coil. The distortion-masking mechanisms in a TH would make a TH sound audibly superior to a vented box at high power. For instance, the MTX and Eminence woofers that Danley uses are damn near ideal.
But for the home?
Three or four small subs will sound more natural. My house, like a lot of new construction, is hyooooge. Yet I have no idea where I'd hide three or four tapped horns. Even if I figured out where to hide them, I'd have to re-construct the listening room to deal with that much bass I think. I'm mystified when I see people building eight cubic foot tapped horns, when three or four subs would give you comparable SPL, sound better, and they're cheaper (if you use inexpensive woofers.)
At this point I'm running two subs, with one more to finish, and I might go to four.
When I turn on the second sub, my ability to "localize" the subs is diminished greatly, which is one of the greatest benefits of using multiple subs.
In my experience, the biggest complaint that people have about their subs is that they're too easy to localize.
The use of multiple subs addresses that nicely.
Can you post some spl graphs and distortion measurements of the two? In my experience, after reading all the stuff gedlee has said, Ive had 3 different subs in the room at the same time Dayton DVC, Dayton Ref, and Lab 12, and my single tapped horn completely blew them away sq wise. It wasn't even close, yet I havent hooked the 2 tapped horns up at the same time.
I'm dying to do that, but my measurement rig is in a box at the moment. I can do impedance measurements, but not SPL measurements at the moment.
As soon as I can, I'll take a crack at it.
I'm not trashing the TH by any means - it's a neat design. I'm just coming around to the belief that a bandpass has comparable distortion killing mechanisms, and is easier to build. Without a doubt, the biggest advantage to a TH is that big fat distortion-killing notch that lies just above the passband. That could explain why your TH sounds so much better than your prior subs. Based on listening to them back-to-back, at the same power, the bandpass is noticeably more efficient (thought it *doesn't* play as low.)
If you have the patience and the room to build three or four tapped horns, by all means, go for it. If you don't, I believe three or four bandpass subs will trump a single tapped horn.
As soon as I can, I'll take a crack at it.
I'm not trashing the TH by any means - it's a neat design. I'm just coming around to the belief that a bandpass has comparable distortion killing mechanisms, and is easier to build. Without a doubt, the biggest advantage to a TH is that big fat distortion-killing notch that lies just above the passband. That could explain why your TH sounds so much better than your prior subs. Based on listening to them back-to-back, at the same power, the bandpass is noticeably more efficient (thought it *doesn't* play as low.)
If you have the patience and the room to build three or four tapped horns, by all means, go for it. If you don't, I believe three or four bandpass subs will trump a single tapped horn.
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