theres a company in canada called unobtanium welding. they took hemhotlz tubes to a new level on the 996 turbo and its a beautiful thing to see and hear. here is one of the early models they built. basically the tube changes the rpm range were the drone is the worst. by lengthening or shortening the tube you change the pitch

 

Wow that looks amazing, I'm sure they're a pretty penny though.

 

Yes the above works but it's also about cost. When most clients now a days look for garages to make X exhausts for them ( at cost and then all of a sudden there is a big long thread about how great it is followed contact into), I highly doubt most will spend he $4500 or more for an exhaust. Thats just a fact.
My point is : someone has a shop that's making him a a X no mufflers Probably for pennies on the dollar meanwhile you guys are comparing it to the most expensive product on the market.
Heck, give me enough money I'll make airplane quality Intercoolers lol.
Cost to benefit ratio tells me that some decent mufflers does take care most of the issues. I've driven so called no drone exhausts and I'm sorry but they drone too. And I've been at this since 2001. I've probably driven just about every exhaust on the market.
The last one I was in was pipes only x someone made for my client and I thought ( mind u my car has straight pipes and revs 8500) I was going to get a stroke. The piercing in my head was so bad cruising in 6th.
I probably have the video somewhere where u an hear the repetitive howl every second.
Just sharing my thoughts.

Ps. Most guys who spent big money on no drone exhausts will never admit they drone because they are either in denial or they need to justify their spending.

 

I think it would be very simple and cheap to add a couple of helnholm resonators to the OPs X pipe exhaust. The material cost is insignificant, certainly not any more than mufflers would cost. It just takes the know how in calculating the proper length of each resonator based on the drone frequencies you are targeting. There is a formula for that. Different turbos will emit slightly different resonance frequencies and you can account for that by slightly varying the length of the resonators. Yes, the exhaust pictured above is expensive but a large part of the expense is the German 130mm 100cell HJS Motorsport catalysts which retail for $1800 for the pair. Without the cats the exhaust is not any more expensive than other 3" exhausts.

I'm a good judge of drone. I've spent thousands of hours in aircraft and my ears are beat up and extremely sensitive to resonance. The exhaust pictured above is a 3" flow through and does not have any drone. Certainly less than a stock TT exhaust which I still consider to have a tiny amount of resonance. So, yes, you can have your cake and eat it too. I certainly would not talk up an exhaust to justify my purchase. That's silly. If it didn't work. I'd get something else. It's that simple. Again, it boils down to either reducing drone by masking it with mufflers or eliminating drone by canceling it with resonators.

 

first of all nobody ever said anything about comparing the o/p exhaust to a u/w exhaust. i was merely showing him what hemholtz is all about. if he chooses to add that to his design thats his choice.
second the u/w with no cats and no mufflers is closer to 3300$ not 4500.
third your exhaust is no different than a gmg , speedtech, srm, or the op exhaust. 2 180 pipes cut and welded together and some resonators and possibly cats. you are charging 2800+$ for yours so the difference in pricing is minimal but honestly the difference in quality of the welding between your tig work and u/w is worlds apart you posted your tig work on f/b with coolant fittings and until you declared it was tig work i thought it was mig. huge beads and no conformity.

just because you havent figured out the hemholtz ratio doesnt mean another smarter better prepared shop cant. i simply removed the slash cut tips off my gmg and added double wall s/s round tips and the drone all but ceased.

 

I'll let everyone know how the drone and welds look when it's all done. As for price, the shop is charging me $1000 with 3 5/8" tips. They do a lot of custom Turbo piping and exhaust work mostly on JDM cars so they aren't charging me any "Porsche Tax". I've seen a lot of their work and it's very high quality.

 

I'm fortunate to spend many hours in Porsche's...stock 6tt has drone, think SOME aftermarket stuff may have less TBH...going to fab my own up this winter, can't be worse than straight outs...there's a few parts I might start working with....

 

The pipes work much the way noise cancelling headphones work, they echo back a cancelling tone. The trick to making them is using a slip fit tube and clamp so the pipe can be adjusted to the customer's particular setup. You aren't going to beat Unobtanium's welding or materials very easily - he's an artist!

http://www.performancetrucks.net/for...-drone-489463/

 

Heimholtz chambers are far from a secret lol, it's easy to fab and the formula for length is online.

 

I agree, that most x-pipes are the same and no one is reinventing the wheel; however, these aren't parallel pipes and most of the ones I see here look like they create a tremendous hot spot because they are just forcing the exhaust into each other. I have the EB werks and yes it's very loud, but drone isn't bad at all as some make it seem here and I just drove my car from Florida to CT and back (over 3,000 miles in a week!). I chose the EB muffler because it's the only x merge I see that still keeps the pipes somewhat separated and doesn't make a large forced merge which IMO is worlds better than all the others posted. It's kind of like the one posted here at the beginning of this thread. That also appears to be well thought out.

 

protomotive design.

 

That's correct. Many of the X pipes utilize a design where the gasses crash into one another creating a bottleneck and a hot spot as a result. You can see an example of that in the picture below where where "X" is all discolored blue from heat while the rest of the exhaust is a nice golden color. Other X pipe manufacturers use a design where the pipes merely "kiss" this reducing or eliminating this bottleneck. Off the top of my head, Protomotive, Kline, and UW use this concept. I know in the UW the window between the pipes is rather small, maybe 1" x 1" so only a very small amount of the gasses transfer to the other side. The UW exhaust I have is used very hard at the track and it has a uniform color though out without any evident hotspots. The function of the X is strictly sound. The X certainly does not help flow so you really want to minimize the amount of the X to minimize the restriction. If the two pipes were totally separate, that would be ideal from a flow standpoint (i.e. straight pipes) but the sound would suffer.


[url=https://flic.kr/p/LU416z]

 

Yes, proto seems like a nice design and is more of an H-pipe versus an x merge. I don't know about the UW and all the others as they still start to merge at the top of the radiused turn in the center. Inside though the UW does seem like a nice(r) merge but again looking at the whole picture it doesn't appear as "divorced" as I would like it. Even the GMG and BBI ones to me look terrible. It's like a basic 90' chopped in half. The top of the merge should be closed and only allow each bank to flow into each other and not force the exhaust from each bank together.

Attached EB pic for reference of a nice deep x merge.

 

It might look deceptive but the UW is very much divorced. The window between the pipes is only about 1x1". I can't speak for the others. The best judge of a bottle neck is to look at the particular exhaust once it has been exposed to sustained heat. Bottlenecks will be evident by the discoloration.

 

I can say that I have never seen a SpeedTech X-Pipe with blueing of the metal at the center or anywhere else, even after years of hard use. We often swap out customers X-Pipe sections for performance or sound reasons, so I end up seeing a lot of used SpeedTech X-Pipes. Never have I seen even a remote hint of blue. Only a golden brownish color.

Just adding another data point for this thread.