JustAGuy,
Your software that you are using , is it asking for "Pe" (watts input) or is it asking for something like "Acoustic Power" ?? It can be easy to mistake the difference ..
I am using other software to calculate port velocity and it is telling me that we are well below the DANGERZONE (yeah, thats an Archer reference) even at full power ...
Your port area calculations are good , ending up with a port area of around 120 cm sq (from the Akabak script for Saba's Alpine box) which is about 5 inches or almost 12-3/4 centimeters ....
I will post some screenshots so you can see what i did ..
The software I am using is Akabak. It asks for Input Voltage, same as Hornresp's Eg.
The only software I know of that can simulate velocity in the MIDDLE of a design is Akabak. If you are using Hornresp you can only check at the throat and the mouth, velocity should be safe at those places. You need to check velocity at the beginning and end of the constriction, and like I said only Akabak can do that.
I used 36 volts to get to 10 mm excursion (xmax) and checked velocity at Duct (1) D8 and Duct (2) D8 from the script in post 167.
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Again, you don't have to widen the constriction, you just have to flare the ends of the constriction.
If you guys could picture the constriction as a port joining two chambers together you would get it. Use a flared port instead of a straight port or it's going to chuff at both ends.
I got the image. Only really reasonable to "flare" on one half of the port (meaning the outer piece of wood), so you would have flares on both entry and exit but they would be like half flares.
Yes. You could redesign a bit so you could have full flares instead of half flares but either way the flare has to be pretty big, more than just rounding over the existing corners. Flare It is saying 40 mm flare radius on the 122 mm diameter port to get the blue chuffing line up to 26 m/s at 35 hz.
So at a minimum you would calculate the area of the exit of a 122 mm diameter port with a 40 mm flare radius and make sure your rectangular constriction exit and entrance are at least that big. You can flare up to 45 degrees on either side (so a full flare can flare out twice as fast as a half flare because a half flare only has one flaring edge) but I wouldn't flare any harder than 45 degrees on each side or the expansion will be too fast. It wouldn't have to be a long flare.
Anyway, waiting for Matthew to post up the screenshots. I need to sleep so if it isn't in the next few minutes I'm over and out.
Saba,
Since the magnet will be in the mouth you can actually make the mouth cm sq area larger than the pipe area (824cm sq or only about 7-5/8") ... The magnet and basket take up space there creating some additional mass loading and in order to compensate you can simply open up the mouth some more
According to model, size of the mouth doesn't affect fb. The fb is dictated by volume before constriction, TL length before constriction, and constriction width and length. Mouth size may affect how well the tapped-pipe 6th order bandpass feedback works and may reduce or extend bandpass so that HF cutoff changes.
Great to see that someone is using the script I posted.
A note to wanting to flare/round the ends to reduce port noise: it will reduce port noise but will also effectively make the port length "shorter" due to reduced fluid resistance. A squared edged mouth has what is known as a vena contracta where the effective CSA is 60% of the physical area. Adding round overs changes this to high 90%. You will end up raising fb if you don't compensate with either longer or skinnier channel.
What does vent 'chuffing' have to do with this cab alignment? I mean the vent is loading a chamber with a driver in it, ergo is mass loading it and the sum of these outputs vent through the terminus, so it's this vent area that sets 'chuffing' and being so large I find it hard to believe it can be a problem since it's going to be at least 80% of Sd.
GM
GM
AFAIK there's no limit per se as it just becomes more acoustically resistant in nature and at some point 'closes up'.
For typical vents, ~ 4.5 [after R. Small] - 5% [I forget who] vent mach is the goal. Way back when these were worked out, there was no high power, high Xmax drivers plus tended to be high compliance, so vents didn't need to be too big, but nowadays with low compliance, ridiculous high power and Xmax woofers; PRs, MLTLs, [inverse tapered] TQWTs are often required.
GM
XRK , Saba , and JustAguy
I am just waking up over here, catching up as well ...
I agree with you XRK, chuffing is NOT likely to be a problem...Not at all a problem with the Alpine 35hz (Saba's) ML-TP or the 40hz version , at 250w for either box , or 500w even ... I have been trying it out in multiple softwares and the results show that velocity is well within the safe range ... The fact that the port is recessed into the cabinet shouldn't worsen the matter,, at least it wont matter THAT much, in fact moving the port away from the highest velocity area (the very end of the pipe path, which is the mouth) could even be helping to reduce the likelihood of chuffing even further, and if not that then we have the masking-effects/bandpass-cutoff working in our favor by helping to filter out any such undesirable noise above the cutoff frequency (if those extraneous noises were even being generated to begin with) ..
In other words, i really don't think this is anything to be concerned with..
We are talking about the equivalent of a 5" diameter port on a box for a 10" woofer after all ..... Think about it .... Thats pretty big , and in other scenarios (like a reflex or a bandpass box) would be considered perfectly acceptable in regards to velocity at these power levels...
Saba's testing results further support what i am saying.. He says he can drive his Alpine ML-Transflex enough to shake everything in his house without noticing any chuffing whatsoever ... It is a real life experience at 36 or 38 volts, so what more do we need?
Lets not be scared about a non-issue ...We have both virtual simulated proof and also real-world experience to support that Mr Chuffy The Boogeyman doesn't live in this Alpine box ...
I will take a closer look at the constriction in the Eminence box too..
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Good deal - although I haven't started - I will be - and it would be nice to incorporate any additional tweaks that may optimize performance.
Thank you.
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I agree that having a real life operating unit thanks to Sabaspeed says it all about this non-issue. There is another driver that you guys may want to take a look at: Infinity 1260w for $62 shipping included. It is even higher sensitivity than Alpine and has huge xmax of 13mm Qts of 0.39, 93dB sensitivity, and 300watt rating. I have used it in several other tapped horns designs and the sims are pretty amazing for the price.
http://s3.amazonaws.com/szmanuals/663ab8fc44823217fd87abef74b72ce5
http://www.amazon.com/gp/aw/d/B0028AVGEO?pc_redir=1408457165&robot_redir=1
If you guys want to take a crack at the design in HR first I will also try in AkAbak.
http://s3.amazonaws.com/szmanuals/663ab8fc44823217fd87abef74b72ce5
http://www.amazon.com/gp/aw/d/B0028AVGEO?pc_redir=1408457165&robot_redir=1
If you guys want to take a crack at the design in HR first I will also try in AkAbak.
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Well, I have several NIB 10" subs (don't ask why) and I think I'll give "your box" a go once the Lab 15 has been built.
I picked up a Crown x1000 (a somewhat heavy (30 lbs) somewhat no frills, 300W per channel @ 4 ohms pro amp for $99 new) and they could drive a couple of 10s nicely in my study.
BTW the Crown X1000, X2000 and X4000 are on a sort of blow out (they are $99, $199 and $299, respectively) at Guitar Center.
Crown X4000 Stereo 2x1350W Power Amp | GuitarCenter
Beau ,
You betcha , and no prob
Since JustAGuy seems to show extra concern for potential chuffing with this Eminence box, i will definitely take a closer look at things ....
At a quick glance it seems that under normal circumstances the 150cm sq constriction APPEARS to be fine at 600w in that Eminence box, but i will thorough by digging deeper to be absolutely sure ... If there isn't plenty of headroom and things look marginal then i will modify the design to open up the constriction somewhat just to be safe ...
Beau ,
You betcha , and no prob
Since JustAGuy seems to show extra concern for potential chuffing with this Eminence box, i will definitely take a closer look at things ....
At a quick glance it seems that under normal circumstances the 150cm sq constriction APPEARS to be fine at 600w in that Eminence box, but i will thorough by digging deeper to be absolutely sure ... If there isn't plenty of headroom and things look marginal then i will modify the design to open up the constriction somewhat just to be safe ...
I've planned on rounding over (routing the edge) of the internal corner edges.
Thoughts?
Thats a really good deal for those X series Crowns! I understand they are good enough to drive subs if you don't mind the weight of them ...
What are the Thiele-Small parameters for the 10" drivers that you had in mind? The ML-transflex likes an FS at or above the FB, tight suspension and high motor strength within reason, and a QTS or around .5 (plus or minus depending on FS , bl , MMS etc)
I'll have to look. They include some old Stereo Integrity 10s, DD2510s, and TC-1000s.
I know, stupid, huh?
I did this driver like 2 weeks ago in the simulation and it is poorly designed for this alignment, too high FS. I agree it is a kick *** driver for TH and even FH but it simply doesn't produce a "nice" response in this cabinet design. Again I didn't spend too much time messing with it but from what I could tell it was a lost cause and I moved on. Maybe if you're building a MLTL that wants to go to 15 Hz, but that wasn't my design goal and then we're talking 6 feet tall subwoofers.
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