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Kevin Kendrick
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06/10/2019 2:03 pm  

@123toid

Thanks Nick! Glad to be back, and looking forward to interacting with you guys again.

Agreed, it's a bummer the way it's set up but understandable, they're just trying to keep it fairly easy to distinguish which speakers should be in which class. IMO, some of their classes need to be modified. For instance, the "All Dayton" class should be able to have active and or passive speakers within it as long as all of the drivers are "Dayton". Also, like you said, the "Unlimited" class is really tough to compete in with smaller speakers. Seems like a sub-division of some type for that class would be a good idea. For those of us who participate, best thing to do is make recommendations to PE, they might listen and agree.  They do want it to be a good experience for everyone involved and I've always considered them open minded to suggestions.


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Lindelium18
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18/10/2019 4:58 pm  

Well, the past couple of weeks have been busy...and not with anything I WANTED to do. But, I did get a little work done on these.

image

 

I’m hoping that when I put a round over on the port, it resolves my chuffing issue. I mean, it’s only audible at 125 watts or higher on the sub alone so I don’t think it’ll be an issue for now. But if I go the separate amp for the sub route in the future...I may have an issue. Time will tell. 


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TVOR-Ceasar
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18/10/2019 7:36 pm  

@lindelium18

Looks pretty good so far. Any test video slated for the future?

-Charlie


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Lindelium18
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18/10/2019 9:57 pm  

@tvor-ceasar

Actually, I forgot that I shot some already. 


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123Toid
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19/10/2019 10:07 am  

Holy cow!  That surround!  That looks pretty awesome.  I hope you can get the chuffing worked out.  I know that can be a pain to work out.


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TVOR-Ceasar
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19/10/2019 12:33 pm  

Flares, man, flares! 🙂 

It's all about fluid dynamics. Since air is classified as such, the same applies. Chuffing is generally attributed to the violent depressurization and turbulence at the end of the port. Smoothing the transition to open air (and entry to the port) goes a long way toward taming the noise. If that doesn't resolve the issue, then a larger, longer port is usually the remedy.

Of course, you could always go with a bandpass design...

-Charlie


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Lindelium18
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19/10/2019 1:04 pm  

@tvor-ceasar

Yeah, I’m hoping the round over is going to be enough flare...  we will see. Is there any need or benefit from rounding over the internal parts of the port?


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TVOR-Ceasar
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19/10/2019 3:44 pm  

That is a really good question. 

The 2 basic camps are:

1. There is no real difference since all that is inside the enclosure.

2. The turbulence inside can be heard through to the outside.

**SPECULATION ALERT**

I am of the thought that if you control both sides of the port, you will reap the best response possible. Smooth in, smooth out. Any diffraction of the waves at either end can carry through to the opposite side. As an example, if you throw a stone into a pond, you create waves spreading out from the impact. If you then throw another stone into the pond in a different area, those waves will intersect the original ones and continue on their own path regardless of the original waves, and vice-versa. So if you reduce the turbulance at both ends, you will ultimately make the port more effective at what it is designed for. And what would it take to round off the edges inside? Not much, and it can only help, imo. Thing is, you'll have to experiment to find the right amount of round off and if you'll need a slight extension of the port to compensate (I doubt it.)

-Charlie


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Kevin Kendrick
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19/10/2019 5:02 pm  

I'm with Charlie on this, if it needs the flare, flare both ends. 


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Kevin Kendrick
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20/10/2019 6:07 pm  

@lindelium18

Maybe I missed it? Can you share the information about the size of your enclosure and port? You mentioned hearing chuffing at 12 m/s in a different thread. Something doesn't sound right about that so I was curious about your vent size and enclosure choice. How much volume did you allow  for the sub and what is the height, width, and length of your current slotted vent? I can run the simulation in BassBox and maybe Nick can run it in WinISD to see if everything looks good.  Just trying to help if you're interested in one of us double-checking your numbers.  


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Lindelium18
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20/10/2019 11:01 pm  

@kevin-kendrick

Sure, that’s no problem. 
Total enclosure is:

42”h x 10”w x 12”d

The port is a 2” x 8.5” slot, 34.5” long. 

Volume of the enclosure (internal minus the port, the driver and bracing) is currently is approximately about 1.5 cu ft. 


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Lindelium18
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21/10/2019 1:06 am  

So, the way I see it, as the enclosure sits now. I’m tuned to 28.3hz. And with a 125w plate amp hooked up, she’s a huffin and a puffin from around 20 to 30hz.  I don’t know if this video does it justice but here’s what I whipped up real quick:


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Kevin Kendrick
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21/10/2019 1:37 am  

Okay...here's what I've come up with. Granted, my simulation is run in BassBox and it's based on PE's published specs for the 8" Ultimax. If you've run a DATs sweep, might be better to work with.

Making some assumptions here, guessing you are trying to tune somewhere around 29-30hz. That's the estimate I'm getting from BassBox based on your vent size and length in the 1.5 cu ft enclosure. Hoping it's close anyway. BTW, Bassbox is also recommending a smaller vent than you're using, it's suggesting a 3.75" round vent. Your slot vent is equivalent to a 4.75" round vent. Doesn't seem like a big difference but the extra size in diameter is increasing your length requirement by 14".

 Anyway, according to the BB software, anything more than 125 watts in your enclosure will be pushing the driver beyond it's X-max capabilities, but that would only apply to frequencies below 20hz. Without a HP filter, might be an issue on some movies, but fine for most music. The curious thing is, you mentioned chuffing, but it's not making sense. At 125 watts, with your current vent size, I'm showing vent velocity at 9 m/s. That's well below what most recommend and it really shouldn't be making any noticeable noise at that rate. Thinking out loud here, but I'm wondering if the extra length is causing a problem and the vent isn't actually acting like a Helmholtz resonator but more like a transmission line? Just taking a guess here man, not sure what's going on but trying to help.   

Hoping Nick will take the time to run the simulation also, curious what his thoughts will be. Best of luck! 


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Lindelium18
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21/10/2019 8:48 am  

@kevin-kendrick

A 18hz high pass is planned but since that calls for a 2,500 uF capacitor, I haven’t bought that yet. I originally had a 1” vent (I think it was something like 13” longish) and I could hear chuffing even under my test amp. So, I made the vent bigger (and obviously longer) to try to compensate. It is weird the BB is saying port velocity is only 9 while winisd said something like 12-14 I think...  


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Kevin Kendrick
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21/10/2019 1:29 pm  

@lindelium18

2500 uF cap, well I've got several of those laying around, just kidding. You can probably buy a MiniDSP and actively high pass cheaper than building a 18hz passive filter. Which sub amp are you using, surprised it doesn't have a HP filter option?

That is strange the m/s isn't matching. I'll go back and double check the T/S parameters to make sure I loaded them all correctly.

Do you have a DATs? If so, have you confirmed the port tuning of the enclosure?

 


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