Giving the RE XXX another Try *Pic*

[audioholic 5,000+ posts]

hah, I used that scenario myself several times back in the day. "so if an 18" is slower than a 10", does that mean that the 10" actually plays a 50Hz tone when it is given a 40Hz signal? Does the 18" actually play a 30Hz tone when given a 40Hz signal?"

Exactly. Velocity affects excursion potential at a given frequency. This does play a larger and larger role at higher frequencies. So yes, mms could be said to affect bandwidth, but given the relatively narrow passband of subwoofers, its role is diminished. mms, for example, plays an extremely large role in tweeter design.

 

[Snow90 10+ year member]

lol @ Hornedfrog.

 

[FurbiesAndBeans 10+ year member]

How can you design the woofer around the box without knowing what box the person will be using? Different vehicles have different transfer functions and not everyone wants the same FR out of their subwoofer. The only company that I know does anything like that is DD as people generally want loud when they choose DD subwoofers. I'm quite aware BigRed uses DD subwoofers, but honestly, I'd say his perfect scores are mostly a reflection on the fact that his midbass to subbass transition is good as that's pretty much all they judge at SQ comps. If the bass isn't behind you and it seems to hit the lowest notes then your good to go. Kicker made plenty of SQ cars too for this very reason. Anyway you should elaborate on the better transient response as I don't see how having two radiators, both a a speaker and port that aren't even in complete phase would EVER have better transient response. You added more variables to a non-linear system.
Anyway Pete is a great designer, I know he uses Akabak, which is a very poweful design software, albeit hard to use for most. I'd also agree Ported enclosures are better for SQ in a car. Transient response in a car is a moot point since the subs are behind you reflecting 8000x times in a tiny car where almost every frequency is simply pressure mode as the waveform has no room to develop before reflecting. The extra couple m/s isn't going to matter a bit. However, when you use a ported enclosure you can cut down on excursion dramatically as well as use less amplifer power. Once you have more ouput than you can ever need to can shape the frequency response anyway you want without worrying about distortion. I'd rather do that than shoehorn a sub into a tiny box and get frequency response that is relatively close right off the bat, but have terrible dynamics as a result. Anyway since had a hand in it, what tuning frequency and box size is he using when he's competing, I was always curious?

Anyway most research on transient response shows that anything below 18m/s in subwoofer territory is ok. That's in a perfect room with good hearing, go into a car an any value you would get in even a decent enclosure is going to be ok. I doubt in the real world anyone can even tell, the better "transient response" that people think they hear when using a sealed enclosure is mostly due to a better frequency response, which a ported enclosure can very well do the same thing with even better dynamics!

Is that the guy that has a huge lifted F250(or 350?) thats red? I saw him at an SQ competition last year but didnt get to hear his truck cuz i had to leave //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[Kyle_Keating 10+ year member]

just to add some 2 pennies, i have a 12" xxx, the driver is indeed better for lower octaves, and it does excel at them, especially compared to other common drivers in a sealed alignment. It has lots of displacement and a high-ish q allowing it to have good response without a lot of EQ correction down low and lots of headroom. The issue is its about 80dB at 1 watt (per my TSP measurements) so compare that against a common ~86dB 12" woofer and you need 4 times the power to reach the same levels in non-displacement limited frequencies. So above 30-40Hz, its going to be hard to get this driver to match even average drivers, but when you start diving down it really beats everything. There are a lot of build threads and discussion about XXX over on the DIY avsforums with the 18" Version which go into a lot of details and tons of measurements. It would be worth checking out those threads if you are serious about this driver.

 

[Papermaker85 5,000+ posts]

problem with DD drivers are the terrible cms varience and high b/l..

they do minize inductance.. but honestly there by few means sq orented drivers..

the best thing is extremely low power compression and excellent damping.. the result is excellent efficency.. so when vented your excursion is minimal leaving BL,CMS,INDUCTANCE variance low.. problem is the enclosures required have cons as well.. you need much larger boxes and higher tuning.. from my experencies whit countless woofers is that there are several ways to get the same end result and everyones perferences differ..

when i design a woofer i try to find a medium between good efficency, low distortion techniques as in spiders, shortings rings excellent heat dissipation etc, as well as obtaining a natural response/sound with the ability to also be used to meet a certian perferences within reason..

example im a basshead BUT it simply has to sound extremely realstilic..

ill use 2 examples of woofers people love for a type of sound thats not transparent .

 

[Papermaker85 5,000+ posts]

w7s.. there great drivers with alot of output, but there bold and can easily sound bloated and warm when the material is simply flat and dry..

another example is the dd 9500 it sound great for high engery quick dynamic bass lines like heavy bass drums, now on bass gatiar or tuba its simply dry and snappy when its supposted to be smooth and warm..

also crossover points can make a HUGH difference so being able to have a wider flat FR is always a +...

 

[Toxic Tuan 10+ year member]

problem with DD drivers are the terrible cms varience and high b/l..they do minize inductance.. but honestly there by few means sq orented drivers..

the best thing is extremely low power compression and excellent damping.. the result is excellent efficency.. so when vented your excursion is minimal leaving BL,CMS,INDUCTANCE variance low.. problem is the enclosures required have cons as well.. you need much larger boxes and higher tuning.. from my experencies whit countless woofers is that there are several ways to get the same end result and everyones perferences differ..

when i design a woofer i try to find a medium between good efficency, low distortion techniques as in spiders, shortings rings excellent heat dissipation etc, as well as obtaining a natural response/sound with the ability to also be used to meet a certian perferences within reason..

example im a basshead BUT it simply has to sound extremely realstilic..

ill use 2 examples of woofers people love for a type of sound thats not transparent .

There are designs that I can only do with DD subs and with no other. Just out of curiosity, when was the last time you tried out a DD sub? The current models are incredible and a lot better than the previous models. Provided a huge enclosure is required, it makes an outstanding SQ driver with the proper enclosure. In a sealed enclosure, it sounds terrible...as it was not designed for it. Also, with ported type enclosures, many traditional TS parameters are thrown right out the window and is not accounted for. Let me know if you like to try one. I think I might have a 1508 sitting around somewhere.

Tuan

 

[T3mpest 10+ year member]

Shush, the adults are talking.
Good thread Tempest, Tuan and papermaker. BTW Tempest, even a simple radio shack db meter can be utilized as a make-shift RTA for what you are wanting to accomplish, it just takes a bit more time than an actual RTA.

Yeah I've got everything for a full MLS setup using ARTA coming in very soon, lol.

 

[Kyle_Keating 10+ year member]

only properly ported XXX 18 i know of...

http://www.avsforum.com/avs-vb/showthread.php?t=1033905

 

[Electrodynamic 10+ year member]

Exactly. Velocity affects excursion potential at a given frequency. This does play a larger and larger role at higher frequencies. So yes, mms could be said to affect bandwidth, but given the relatively narrow passband of subwoofers, its role is diminished. mms, for example, plays an extremely large role in tweeter design.

Mms has nothing to do with bandwidth no matter what kind of speaker you're talking about. Inductance effects bandwidth, not Mms. Mms effects efficiency and Fs. Take a look at this picture and tell me which one has more mass and which one has higher inductance (same driver - one is the reference line [driver as is], the other is with inductance added, and the other is with mass added):

Mms's role in subwoofer design is closely associated with BL and Cms as it relates to the F3 of the system in its target enclosure size and type, not with how high the driver will play (aka: bandwidth).

 

[ciaonzo 5,000+ posts]

Green line is inductance added?

 

[ciaonzo 5,000+ posts]

Red line is reference?

 

[Electrodynamic 10+ year member]

Red line is reference?

Yep, we have a winner. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

PS: Your previous post is also correct. Added inductance has a much more negative effect than mass does in regard to high frequency extension.

 

[Papermaker85 5,000+ posts]

ffunny how the red and green are nearly identical thoughout the FR whike addind mma wreaks havoc on FR..

 

[ciaonzo 5,000+ posts]

Yep, we have a winner. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
PS: Your previous post is also correct. Added inductance has a much more negative effect than mass does in regard to high frequency extension.

That was a tough one not knowing which line was the reference but I knew that adding mass would change the frequency response in a way that inductance wouldn't so I went with my gut.