Quick questions...should I be buying the SI HT18 or HST18 for my stonehendge build?

[Paducah Home Theater]

In terms of the cool factor, they're a lot better if you have a big fat round wire. They look pretty dorky when you have standard wire. On my bass cabinet I used a four conductor wire and it filled out the entire back of it, that looked real nice. My home theater wiring, not so much.

[babadono]

 

Monoprice also makes RCA to XLR cables that are wired properly. One example:

http://www.monoprice.com/Product?c_id=115&cp_id=11509&cs_id=1150902&p_id=4777&seq=1&format=2

They make with either XLR male or female ends. Many different lengths available.

 

i just read your review on their site.  are you saying that buying something from parts express carries a higher chance of obtaining something that's improperly wired?

 

I do not want to start a 'cable' debate as has been known to happen here on this wonderful Klipsch website. Let's just say when feeding a balanced input(XLR) from an unbalanced output (RCA) there is a correct way to wire the cable. Monoprice does it correctly. I have no knowledge of how PE does theirs, so no I am not saying a cable from PE will be improperly wired.

[dewthedru]

deleted

 

Edited March 31, 2015 by dewthedru

[dewthedru]

thanks for the help guys.  i'm going to create a build thread if you don't think it will clutter up stuff too much.  

[CECAA850]

I had no problem.  If you ever went with a sealed enclosure, you could use a small piece of gasket material.

[CECAA850]

thanks for the help guys.  i'm going to create a build thread if you don't think it will clutter up stuff too much.  

 

 

Build threads are awesome.

[Paducah Home Theater]

I had no problem.  If you ever went with a sealed enclosure, you could use a small piece of gasket material.

 

I was reading a sub box design article the other day and it said ported enclosures can actually be twice the pressure as sealed.  

[CECAA850]

 

I had no problem.  If you ever went with a sealed enclosure, you could use a small piece of gasket material.

 

I was reading a sub box design article the other day and it said ported enclosures can actually be twice the pressure as sealed.  

 

 

 

Interesting.  Do you have a link?  I enjoy the read.

[Paducah Home Theater]

 

 

I had no problem.  If you ever went with a sealed enclosure, you could use a small piece of gasket material.

 

I was reading a sub box design article the other day and it said ported enclosures can actually be twice the pressure as sealed.  

 

 

 

Interesting.  Do you have a link?  I enjoy the read.

 

 

http://www.kicker.com/Ported_Enclosure_Pros_and_Cons

 

cons... "enclosure itself must be more solidly constructed because internal pressure at frequencies around vent tuning can be nearly twice as high as a sealed enclosure."

[CECAA850]

Thanks.  That's so strange as the driver barely moves at the tuning frequency of the box.  I never would have guessed.

[m0reilly]

i would assume they are referring to vibration rather than actual air pressure. there is a hole in the box...

[Paducah Home Theater]

i would assume they are referring to vibration rather than actual air pressure. there is a hole in the box...

 

Nope.  Here is an explanation from Klipsch's very own Dave the engineer:

 

-------------------

 

Yep, I've seen this topic tossed around a lot, and indeed yep, most people are of the mindset that since it has a "hole" in it, it doesn't have a lot of pressure. Kicker is actually correct and is likely citing a paper from many years ago which took in-box measurements of ported boxes. The pressures around the tuning frequency are extremely high, and indeed higher than a sealed box.

 

The reason is that given an adequate amount of air, it's not too hard to compress the air in a sealed enclosure. You can easily do so with your hand by pushing on the cone. When it's active and playing, the force that's moving the cone to get a certain SPL gets back to Bl * i, with i being the input current. The pressure on the cone is that force divided by the cone area, Sd.

 

Consider then, if you observe a ported box playing at the tuning frequency with the driver nearly motionless, just what sort of force is required to produce that same SPL, but then keep the cone from hardly moving? You've put in the same "i" and Bl is unchanged, so to drive that port to produce the same SPL and then keep the cone from hardly moving means that something is creating a back pressure. That back pressure is from the interactions going on inside the box where the port forces the driver to become motionless.

 

It's also not too unreasonable to accept when you consider a passive radiator box which must be airtight to function properly. The rule of thumb is to use either 2x the number of PRs as active drivers, OR, 1 PR with 2x the displacement capability. This is because of the same effect: the PR is not just going to create the SPL you want, it's also creating the back pressure to keep the cone motionless. Therefore, you need twice the excursion ability, and if you don't, your system output drops. (It's why most companies with single PR boxes put the PR on the front and active in the rear so that you see impressively massive excursion   )

 

If you're into cars and/or tuning, you know you can easily improve system performance with exhaust systems. This isn't necessarily because the original was so restrictive, but because the engine can't create full power for a given air/fuel input because it's held back by the original exhaust system's back pressure (e.g. undersized passive radiator). That backpressure isn't used to keep power away from the engine, it's to keep the SPL down so the muffler's job is easier. No coincidence that exhausts are carefully tuned resonant ports in effect. 

 

It all boils down to the nitty gritty of what happens in resonant systems.

 

Hope that helps some! 

 

-- DaveWJr.  

------------------------------------

 

Or, as a visual that you can try yourself, consider how the physics react if you were to take a weight and tie it to a string so that it is held 12-15" from your hand.  When you swing it back and forth a small amount at resonance, your hand is actually barely moving even though you are swinging the weight quite a bit.  It's hard to describe unless you actually do this.  You can feel the forces react on your hand, as you are switching directions before it gets to the full height.  In effect you are cracking a whip of sorts.  I think this same exact phenomenon is happening inside of a ported box at resonance.  The cone starts to compress air in the box while the air inside the port is still at velocity coming into the box through the port, creating back pressure.  Likewise, the cone is flexing outwards and lowering air pressure in the box while the air in the port is still at velocity heading out of the box through the port.  Both actions greatly limit cone movement, much more than a sealed box due to the pressure.  Get below the tuning frequency and all this pressure goes away, the unloaded driver starts flopping like a fish out of water.  At this point, yes, the "but there's a hole in the box" rings true.  

 

Read the "at resonance" bit here towards the bottom:

 

http://www.hometheaterhifi.com/volume_5_2/cmilleressayporting.html

 

Edited May 27, 2015 by MetropolisLakeOutfitters

[CECAA850]

That back pressure is from the interactions going on inside the box where the port forces the driver to become motionless.

 

That's the best explanation I've heard yet.

[m0reilly]

well i'll be...thanks for that dave the engineer!