A Victim of My Own Arrogance (Or: PA130 Revisited) - Page 2 - diyAudio
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Old 2nd May 2008, 02:23 AM   #11
fwater is offline fwater  United States
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GM- I knew that the Vas would sum, but I was aprehensive about the "particulars" as you say. I just don't want to find out the hard way that there's a hidden or unexpected interference found in a horn or ML-TQWP when using two drivers. The more I think about it, what's the worst that could happen if the PAWO or Mileva don't like the PA130? Cover the back hole, buy a set of Fostex, be happy.

Kensai- I had completely forgotten about bottom loading a BiB! If they were built correctly, they could be reversible without any major modifications. Seems like a great way to get back some of the benefits when not close to a wall, but then I suspect that BSC might need to be employed. I'm not into HT, but I am into heavy music (Ministry, High on Fire, Clutch, etc.), so there has to be a bass presence but not any massive amount below 40Hz.

Between the BiB and the Plant 10 designs, the only difference I can observe without actually hearing them is size. My listenning room is fairly small. If anyone can convince me that the BiB is the way to go, I can live with big enclosures (no spouse to enforce WAF). If the other designs have sonic advantages, I'd like to know that as well. I will be building this weekend, so I need to settle soon. Hell, maybe I'll have to build all three...

BTW, I'm always impressed at the exchange of ideas and guidance lent on these types of forums. I know that is what's expected here, but I just want to express my gratitude to those who know better than me and are willing to speak up and help out.
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Old 2nd May 2008, 05:29 PM   #12
Kensai is offline Kensai  United States
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Don't forget, you can turn the BiB 90 degrees so that the driver is mounted on the longer side (off center, of course), and then you can have the mouth fire to the side at the floor. For a single fold design, you can use 0.416 for the zDriver calculation to get the driver position up and have good ripple performance. This way you'll have a fairly flat, slightly wide enclosure that could easily be placed up against a wall, which would effectively corner load the mouth without needing an actual corner.

As for the other designs, I've not heard them. They look great. They've got good commentary around here. What I think we're going to see among all cabinet types we've mentioned hear will be absolute extension and gain at the bottom versus absolute detail. The BiBs should win on extension and gain, but the P10 designs will sacrifice various amounts of bass for a bit more refinement in bass presentation (look at the BiB sims in these posts and see the various bits of ripple in the mid and upper bass; gonna bet any P10 design will be significantly smoother through that region).

Anyway, I think that go get solid presence to 40Hz, you're going to need a BiB, probably with a line length of at least 120", though I am just making a sorta educated guess there.

Kensai
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Old 2nd May 2008, 08:49 PM   #13
fwater is offline fwater  United States
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"The BiBs should win on extension and gain, but the P10 designs will sacrifice various amounts of bass for a bit more refinement in bass presentation..."

Gain is important here. Once I can establish a quantity, I'll worry about quality. I think I'll go with the BiB for ease of building and low-end extension, then do one of the P10 designs shortly down the road. It's a good opertunity to A/B the different designs; i have enough drivers to run all three in the same sitting.

Kensai, you say something to the effect of using 0.416 to determine Z. With a line length of 144", that would put the driver at 60", a little high for my liking. GM's Bib calculator is telling me 31", a little low when turned upside down. 40-50" driver height is about where I'd like to be. Is there an acceptable range for this 0.416? Also, when putting the mouth on the side instead of the end of the enclosure, does the length need to be changed to account for an earlier exit of the wave? In my estimation, it shouldn't matter much since we're trying to tune much lower than driver Fs anyway, but i've been wrong (grossly wrong) before.

I promise to make these the last questions before I hit the saw...
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Old 4th May 2008, 03:11 AM   #14
Kensai is offline Kensai  United States
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144" may be more than these drivers can handle, though I've not been made aware of what happens when you tune one of these suckers too low.

Anyway, 144" gives you an enclosure about 6' tall, so there shouldn't be any reason to invert them, unless you're ceilings are like 12'. The 31" from GM's calculator will put the driver at about 40" when built to fire upward. It can be hard to get the driver height in a good place when designing these. I think the .416 position is supposed to minimize the response ripple the most, while the position from the standard calc is the next best option. Anyplace inbetween will be some sort of compromise, and since there hasn't been many made that weren't really close to one of those points, I don't think we can say what real world effect might be audible. As long as you're not tossing much money away on the cabinet materials here, I'd say put the driver right where you'd want them to be and see what you get.

As for determining the effective line length of any given design, you measure following a path that passes down the direct middle of the line, including as that path goes around any bends, so in the case of a side firing mouth, that line measurement will go to the point in the center of the line area that is level with the middle of the mouth and then curve 90 degrees to exit, which will add some length as the line curves and travels to the side, mostly making up for not traveling all the way to the bottom of the cabinet.

Anyway, good luck, and we want pics ;-p

Kensai
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Old 4th May 2008, 06:59 AM   #15
fwater is offline fwater  United States
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"144 inches may be more than these drivers can handle, though I've not been made aware of what happens when you tune one of these suckers too low."

I would imagine the net result of tuning too low would be loss of output and cone control. Upon further consideration, I'll shoot for 55Hz (120" or so) instead of 45Hz (144" or so). I seem to remember that 70% of Fs being the absolute minimum for tuning, and that might be with a healthy X-max driver- a characteristic which these drivers don't have. 55Hz puts me around 80% of Fs.

"...so there shouldn't be any reason to invert them..."

Remember that the enclosures will probably end up too far from any wall, hence the desire to use the floor for loading. You're right, though, MDF is cheap and a BiB is not labor-intensive, so Z height can be experimental without huge consequences. Again, once I start getting ideas, they can sometimes quickly get out of hand (the double chamber bass reflex that I started with for instance), so I'm a little gunshy without some encouragement.

There will be pictures. I had planned on listenning to these guys in a new cab by Sunday, but my job is so market-driven that when there's weekend work to do, I can't say no. There will be some free time during the beginning of this next week to fiddle around...
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Old 4th May 2008, 07:58 AM   #16
fwater is offline fwater  United States
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"55Hz puts me around 80% of Fs."

Correction: 55Hz puts me at less the 70%. I had confused the Fs of the driver, remeberring it to be 70Hz instead of what it actually is- 85Hz. Lets hope there is a little bit of output left over below tuning, which I may have to put at 65Hz...
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Old 6th May 2008, 04:12 PM   #17
Kensai is offline Kensai  United States
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Actually, according the the DIYer measured specs I have, the Pioneer had an Fs of 109.14Hz rather than the 70Hz listed on the PE site. We do, however have proof, built and listened to cabs using the Pioneer in 120" BiBs, so we know they can handle that. If the PA130 given specs are more realistic, then who knows, perhaps it can handle the 144" line.

Kensai
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