Autotuba measurements, plus shiva

[johninCR]

RCW,

When you talk about higher distortion with sealed, are you talking about when you are driving that sealed sub into high excursion that you get the obviously high distortion, because that would make sense. It would also help explain my real world results because I never push mine hard at all with music. It would be too loud, since I don't listen to anything with really low LF content like organ music or trance type stuff. I can only go by my real world results. As soon as a built this sub, I loved it for HT but really disliked it for music. At first I just assumed it was tuned too low to work well for music, so I used a switch to use a different sub for music. When I read somewhere about stuffing ports, I tried it and it made a very audible difference. I've hauled the monster outside as well just to see what effect the room had and the difference is in the alignment, not how they interact with my room.

Now it's just a matter of stuffing the ports with big chunks of foam rubber when I listen to music. Occasionally I forget but I quickly notice the sonic difference. That also makes me certain that there's no psycho acoustic ** going on, because whether the ports are stuffed or not isn't visible from where I sit. For HT I forget to switch sometimes because I may not notice it, but never for music.

[simon5]

I tend to side with RCW on this... maybe it's because I'm studying in engineering I guess.

I think you prefer your EBS sealed for music because you don't like the extra low end which is there in the music you listen to that your EBS subwoofer can produce, compared to the missing bass your sealed subwoofer can't produce.

So, the sealed subwoofer have more "punch", because the lower bass is rolled off.

To have a fair comparison, you should compare your EBS to a sealed subwoofer with a parametric equalizer to compensate for the loss of low end. I guess you'll get back your "sloppy bass".

Anyway, that's my opinion, and if you prefer your subwoofer sealed, then seal it hehe!

[paulspencer]

RCW, I'm inclined to agree. I'm not convinced there is an audible penalty for the extra output and extension of vented boxes - certainly not one that is purely attributable to the nature of vented boxes which applies in all cases.

I'd like to at some stage conduct a blind AB test of some things like this with a good number of people. Using my Ultracurve outdoors, I could calibrate a sealed and vented sub to exactly the same response. I'm very curious to see if they would be able to pick the difference. I doubt it.

I don't doubt that John can tell the difference with his, but it's not the same kind of comparison.

Some of the best bass I've heard was from a fairly sohpisticated setup which included:

* 3 x M&K subwoofers
* 1 x 15" vented focal audiom in a 200L box
* 1 x 15" vented tumult in a similar 200L box
* Ultradrive DCX for phase correction
* Ultracurve to calibrate them all flat

Now there's more money in calibrating those things than most over here spend on subs!

Subjectively speaking, none of the negative comments I've heard about vented subs applied. The bass was clean, loud, low. My first impression was that I wanted more bass, but I think that was in fact the absense of untamed modes, including a typical 35hz room mode which exists in my room.

Now my more humble system has a pair of AV12s sealed and Ultracurve, they are sealed only temporarily since I haven't gotten around to building proper boxes. The aspect of their bass performance I'm least happy with has nothing to do with the difference between how they sound vented vs sealed, but is in fact the upper bass, around 80 Hz at the top of their bandwidth. I'm yet to determine what this is, but it may be that I need something that has a cleaner top end, which brings me back to the original topic ...

I have considered the idea of an 8" driver in a small horn to handle 40 - 80 Hz. Anyone have thoughts on a bass horn vs drivers like the AV12s for this range? or possibly extending up higher ...

[rcw]

Modelling my woofer in sealed the two types of shelving alignments in Win ISD, and my own QB5 box shows that in fact the sealed box has slightely better power handling over the range 22-40Hz. than either the shelving alignments have, but not nearly as good as with the QB5.
I think it was Bass who commented that comparing the QB5 box with the shelving box might not be a fair comparison and this is true over the range where you find musical bass since no advantage in power handling is there.
The other thing of note is that you need 4x10.2cm. diameter pipes
88cm. long in order to get the vent air velocity down to around 10m/s, so the vents that people have mentioned will probably produce considerable noise for large outputs.
Overall the shelving box might make loud noises that sound a bit like the original sound effects people intended but if I had one I would probably stuff up the port when listening to music myself.

[RobWells]

Originally posted by paulspencer


-snip-

Now my more humble system has a pair of AV12s sealed and Ultracurve, they are sealed only temporarily since I haven't gotten around to building proper boxes. The aspect of their bass performance I'm least happy with has nothing to do with the difference between how they sound vented vs sealed, but is in fact the upper bass, around 80 Hz at the top of their bandwidth. I'm yet to determine what this is, but it may be that I need something that has a cleaner top end, which brings me back to the original topic ...

I have considered the idea of an 8" driver in a small horn to handle 40 - 80 Hz. Anyone have thoughts on a bass horn vs drivers like the AV12s for this range? or possibly extending up higher ...

-snip-

Hi Paul,

As you know I run 3 tempests each in their own 200L cabs. When I had 2x10" scanspeaks in each of my mains crossed to the tempests at 40Hz (24dB/oct) the sound quality was way better than running the tempests up to 80Hz. I'm working on a pair of labhorns to place behind my screen, corner loaded and will use the tempests below ~30Hz. If I wasn't doing the horns I'd be looking at a pair of large (18 or 21") pro drivers to cover the 40-80 Hz range instead. (Have changed my mains to high eff stuff.)

Cheers,

Rob

I posted this question here, but I don't think people took me seriously

Doesanyone cross horn subs to sealed for low bass ?

[rcw]

The thing that I would consider is that a "small" horn to cover that range is still big, and if you make it smaller by reducing mouth size you are going to get the invitable peaks and valleys caused by the reflected wave, and typically with little room gain the frequecies below mouth cut off will be attenuated since the horn turns into its equivalent single ported bandpass box, overall its a damn complicated way of making a bandpass box.

[paulspencer]

Originally posted by RobWells
I posted this question here, but I don't think people took me seriously

Doesanyone cross horn subs to sealed for low bass ?

Ahhhhhh, don't you hate that? Sometimes it's surprising what people respond to on a forum, and what they don't.

[mwmkravchenko]

RobWells

Your idea has a good basis behind it. Most of the slam in music is in the lower end around 40 to 80hz. A horn can when designed properly and not ham strung by over zealous foreshortening produce those bass transients with greater ease than anything else short of stacks of drivers and kilowatts of power. So yeah go for it! It does work and there are plenty of examples in the idustry to support it. THe transition will be tricky. The horn size and placement will have to be well thought out. But it will work.

Mark

[johninCR]

Rob,

Maybe you should try something like the Jensen Imperial. With the huge chamber you get the slam in 40-80 range, plus the region below the acts like the bandpass output giving you deep extension as well.

Steve over at Decware is coming out soon with a sub only version of the design with a throat that is open to the air which is loaded via a Kslot at the side making is some kind of Kslot loaded helmholtz resonator with horn loaded output.

[RobWells]

Thanks for the interest chaps

John - I remember that cabinet coming up a while back in a search I did. I've actually started cutting the wood for my labhorns now. Already have the side panels done for 4 cabinets. (you never know, one day I might have a room big enough!)


As an aside, I'm considering ebs'ing the tempests to lower the eq on them. Figure that below 30Hz I probably won't hear a quality difference as you feel it, not hear it.

Cheers,

Rob.