More likely than not this is a room issue, significant null above 75 hz or so. The measurement was not expected to be useful up high but rather down low. Anyways unless someone wants to buy me a replacement SPL meter I'm done measuring response.
What would this look like? Can you give us a side sketch so we know what we would be looking at?
It doesn't sim better, I tried to make it as similar as possible to the alignment I was comparing to (but without a constriction) to make the point that a constriction is not needed. Aside from the compression issue there really isn't much difference, that's the point. There's no free lunch, any alignment that can be used to get somewhat flat response out of the intended bandwidth in the same size package will sim approximately the same, especially in the low end.
It's a simple single fold tl, but it would have to be changed to PAR segments and ideally it should be refined (or completely redesigned), it's really not (and wasn't intended to be) an ideal design.
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It all started when i was trying out different alignments with the Alpine 10s , this seemed to be something that worked well for them .... The LAB 15 (special) was just a curiosity that I fiddled with just recently when i noticed that it was a good value ... At first when trying it out in a standard non-tapered tapped pipe tuned to 35hz i realized that the driver was an overly tight fit and i wondered if it would work better in a scaled up version of one of my ML-Transflex designs which would have a more accommodating footprint ..... So that was the progression ...
For myself there is certainly an attraction in wanting to try something new and different, and i think that is because when browsing the forums or visiting websites to look at various high performance designs all i see is the same things rehashed and regurgitated over and over and over ad infinitum ....
I think some innovation or new ideas would be good, not that THIS is an extraordinarily innovative idea necessarily because i know that this ML-Transflex is just a remix of some age old concepts, but it is arranged to be fun and quick/simple to build, small, and happens to work great with some low cost drivers ... Having something unique also has a certain appeal to people, and even better if it performs well .. BONUS!
This discussion has also been a great exercise, a learning process and a way to explore some new possibilities.. The exchange has been thought inspiring and positive in general... I enjoy the debate and sharing of ideas ...
JustaGuy , your reverse taper TL looks like it would work well for the special Lab 15 , should have a large enough footprint to fit the driver , and is certainly simple enough.... I think you are right that the difference in SPL and excursion is probably somewhat due to the slightly higher tuning... That driver just seems to model exceptionally well in a TL...It also looks good in a reverse taper tapped pipe having a little more of a bump at FB + a saddle at this VB but adding a little stuffing in the first 3rd of the path would fix that right up
.. The Alpines look good in a TL as well ....I have conducted a few recent real-life experiments with some unique DIY parasitic resonator enhanced boxes and their measurements look very promising but i need to do some more work to make sure i understand what is going on inside of these cabinets before i can even begin to discuss them on a busy forum like this, i want to make sure i know what i am talking about before initiating any discussion about something unorthodox
... If all goes well i should hopefully have something really special to offer up to this community in the future..
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I don't have time to read everything in fast moving technical threads such as this one, especially ones where I don't agree with much of what's being posted, just saw the word used repeatedly.
Again, I don't consider it an issue unless it's a sustained high power app where the driver's construction may not be designed for it.
He did, but it's irrelevant! I used the math that's been proven over decades of high sustained power prosound horn apps to get the averaged throat area over distance for a stepped pipe version of a 0.736 M [T] hypex, so confidant that if there's any compression from high power transients in a HIFI/HT app it will be more due to thermal power compression than any pipe segment constriction.
GM
So true, it is starting to resemble a Karlson ... Hey now, Come to think of it, doesn't the "Karlsonator" even have a constriction in the path that vents into the front chamber followed by a little more path and ..... Well damn ... thats pretty familiar ....
Was there ever any complaints about the Karlsonators having any port compression due to the constriction?
I just remembered I actually started a thread asking about the max allowable velocity in a horn throat a few years ago, maybe weltersys remembers this too. There was a guy that seemed like he knew what he was talking about, he said for Art's Keystone throat size with a very smooth pvc surface, 30 m/s would start to detune it and by 38 m/s it would be completely turbulent. When I asked how to calculate acceptable velocity for smaller throats he said
He had previously mentioned that he independently verified that Flare It is very accurate.
Also note that he is talking about smooth (not stepped) expansion, stepped would be far worse.
I don't have the math skills to back up his statements but if he's right, this is a lot more useful than Olson's blh example with (probably) almost zero excursion driver. I'm pretty sure the last thing on Olson's mind was throat turbulence and/or distortion caused by small ducts, if he ever measured it or even mentioned it I'd like a link. In fact I'd like ANY links that show " relatively short lengths of straight pipes laid out in multiple bends like Olson did with his BLH only rolls off unwanted HF content." While this is almost certainly true for old blhs with fractional mm xmax fullrange drivers and reasonably sized ducts, I'm not buying it for modern high excursion sub drivers and unreasonably small ducts. The software backs me up.
The thread is probably worth a read, even if you only read revboden's posts, there are not many. http://www.diyaudio.com/forums/subw...-compression-ratio-different-perspective.html
He says basically exactly what I've been saying but in a more technical manner.
I was typing while you posted this, but anyway, it seems like average driver xmax has doubled in the few short years (less than 10) that I've been paying attention. What was the average xmax in these decades of prosound horns? 5 mm? Less?
We have klippel verified drivers with 40 mm xmax now. In the next few years probably 50 or 60 mm will be available. It might be time to consider compression issues. It's not irrelevant anymore.
If you haven't noticed I'm not a hifi/ht kind of guy, I design for punishment. This subforum is also geared more towards pro sound than hifi/ht, at least the threads I read and participate in. Also, I think the one guy that built one of these said he was interested in club/dj applications.
It seems absurd to have to argue that small ducts and high velocities are not ideal, especially on a high performance forum.
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Hey there XRK ,
According to your hand written sketch that does look like work , thanks for putting this into Akabak .... 130 or 135 liters is enough volume for the Lab 15 , but i think it might not be clear about how the HR sim relates to the sketch .... The throat chamber has no port attached to it so it is basically just a big chamber with an open end that comprises the first 2 feet of the path which the S1 through S5 connect to... The path then proceeds to S1 & S2 which open up to a large area as it goes around the turn (the reason for the large cm sq area of S2) , then a squeezed down S3 creates the constriction , then below that there is another 30+ inches of path ..... It certainly works well with HR , not sure why it isn't translating to Akabak...
You are right that it is similar to a BVR , or even a Cubo but this box will have more quarter wave action because of it's longer path length , Cubos have a pretty short path
If I were to run an Akabak script with the same four segments you prescribe in HR, they would get the same thing. What I am saying is that your sketch in no way looks like anything like your geometry in HR. In fact, look at the HR diagram and you will see that it has no parallel walls in the section after the driver on the closed end, and an expansion from the throat to the opening with no parallel walls except at the mouth.
-never ran the Karlsonator12 at high power with anything which has much displacement but have 12" Eminence coax with 4.8mm xmax, 109oz magnet and 4" coil - assume Karlsonators 6-8 and 12 would be difficult to overload or compress with the type of drivers intended - never heard K15 wheeze. The 1958 4-saw slit vent Karlson 12 with one watt will blow out a candle and distort horribly on sinewave near fb - its fine with music I like as music is or was transient in nature (before the synths and things like Maschine)
XRK,
Ok , that might be what is missing , take a look at VTC and ATC in Hornresponse ... Those inputs define a chamber/pipe about two feet tall , 57.75 liters with 824 cm sq area .. It has parallel panels... It is the beginning of the path and goes before S1 , S2 and the rest ..
Right on Freddi , that is some good insight on the K boxes ... The Karlsonator with it's longer path looks like it was made to produce some deeper bass than the classic Karlsons, and it's expansion makes me think it would work well with some lower Q pro drivers (lower Q than what we are working with here anyway... .5 or .6 calls for less expansion or none at all to keep things compact)
Correct.
The Lab 12 vent on the back of the magnet structure is quite noisy at high excursion, easily audible with sub only output. The vent noise is not audible if the speaker is placed "normally", magnet inside the cabinet, cone facing the outside world.
If the Lab 15 is similar, (I have not heard one) it would be something to listen to and determine if the noise is objectionable in actual use. Normally the noise would be masked by upper frequencies, but with some types of very bass heavy music and movie sound tracks the wheezing of the vent could be a problem.
Trying out the SWS because it is roughly a lab 15 and is 116 including shipping with no shortage of supply. Hoping to turn this into as simple of an enclosure as possible maintaining maximum spl 30 to 100. I need to know what it would look like so I can modify it to make it reasonable to build.
I know there are multiple threads out there that help with this kind of thing so if someone could kindly point me to a step by step that would be fantastic.
I know there are multiple threads out there that help with this kind of thing so if someone could kindly point me to a step by step that would be fantastic.
Matthew,
A bit of clarification, I tested the Definimax 4015LF in the Keystone, although the FR and sensitivity were quite good, it sounded quite distressed when driven near Xmax, unlike the heavier coned dual Lab 12 and B&C18SW115. BL was not the issue, there was plenty of magnetic force to push the cone into severe breakup, so obvious that I did not even test the distortion, though in retrospect wish I had, just to show how bad it was.
I then postulated that the Kappalite 3015LF, having an even lighter cone (93.4 compared to 139 gram mms) would not be a good choice, even though it may sim OK.
My compliments on designing something a bit different with the Transflex!
Art
JAG,
1) The Hornresp simulated output of the port below 50 Hz is louder than the radiation from the slot (Horn). The port output at 100 Hz is around 16 dB less than the radiation from the slot. The excursion minima at Fb allows a large EQ boost without over excursion, not possible in a sealed enclosure with similar raw response.
2) Ideally, a test of Mathew Morgan's Transflex design would be conducted at various levels to determine if the constriction leads to a compression issue.
3) As a study of port compression compared to predicted port velocity, though perhaps not an ideal case, it provides useful data. The measurement below using pink noise is more indicative of real world response than the sine wave tests we were looking at. The PPEQ+ curve shows response with the amp just hitting limit (around 2500 watts) using the EQ required to flatten response, including the upper crossover filter. PPEQ-10 is the response with 10 dB less drive level (around 250 watts) raised by 10 dB. Worst case compression appears around 90 Hz, compression in the range where the port's contribution is primary is just over 1 dB.
The "Shoehorn" PPSL2x15" has a Hornresp calculated particle velocity peaking at near 48m/s at 23 Hz, around 34ms at the 40 Hz Fb, falling to around 8m/s at 90 Hz (the slot output reaches a maximum of 16m/s at 18 and 78 Hz). The actual measurements show only one dB compression in the port range over a 10 dB increase in power.
The upper response exhibits more compression, while using only a fraction of the LF power, it appears that calculated particle velocity is not adequate to predict compression effects.
Art
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I see ! I am surprised that the Definimax failed, it seems like a tough driver, and im sure you are absolutely right when you assume that if the Definimax fails then the Kappalite 3015lf is surely going to fail, horrifically even
Your Keystone apparently has an extraordinary degree of cone control/damping!
Good stuff ...
Working on the ML-Transflex has been a lot of fun , im just getting finished with ironing out the last few bugs on the 135L version for Eminence's Lab-15 (special)...