Tempest X Sub...

[Forte_II]

I just got my Tempest X installed. It is a great driver, I am impressed with its construction and SQ. It hits hard and goes fairly deep. I have a question though, Can a enclosure be too big? I have approx. 23 ft^3, tuned to 18hz. I think I am not getting all this driver has to offer. I have 1288 watts on tap, but It doesn't go as low as I thought it should. and I think it could go louder. So is the enclosure too big or am I wanting more than a 15 can give.

[Hdale85]

How low does it go? Have you measured with a DB meter or measurement software?

[Forte_II]

No not yet I will get fr tomorrow. Just my first impressions.

[Kevin Haskins]

I just got my Tempest X installed. It is a great driver, I am impressed with its construction and SQ. It hits hard and goes fairly deep. I have a question though, Can a enclosure be too big? I have approx. 23 ft^3, tuned to 18hz. I think I am not getting all this driver has to offer. I have 1288 watts on tap, but It doesn't go as low as I thought it should. and I think it could go louder. So is the enclosure too big or am I wanting more than a 15 can give.

Man... you don't mess around. 8O

Yes... it can be too big, especially if you want to maximize output in the pass band.

How big is your port? With that size box I'd like to see it tuned down around 13-14hz.

A better approach would be 360L, 75% fill with a 32" long 8" port which tunes it around 15-16Hz.



In this size enclosure you can overdrive the driver fairly easy. I suggest a subsonic filter @ 14hz, at least a 2nd order. You only need about 600W @ 23-24Hz to get to full excursion.

[Forte_II]

Well, The volume was not under my controll. It is a big brick fire place that was sealed off and a 3" baffle was installed in the opening. I could build a box to fit in the fire box...

[Kevin Haskins]

Well, The volume was not under my controll. It is a big brick fire place that was sealed off and a 3" baffle was installed in the opening. I could build a box to fit in the fire box...

How did you seal around the opening? Have any pictures? The bricks could be leaky too..... Your in uncharted territory with that kind of construction.

[Forte_II]

I built a 2x4 frame that fits snug in the firebox. The box is in good shape and the chimney is capped with 4" of concrete. The cracks around the baffle are sealed with tape on the inside. LOL I know... I am going to use expanding foam to seal the baffle this weekend.
I am embaressed to say the port is a 4" Precision flared port.

[Johnloudb]

I built a 2x4 frame that fits snug in the firebox. The box is in good shape and the chimney is capped with 4" of concrete. The cracks around the baffle are sealed with tape on the inside. LOL I know... I am going to use expanding foam to seal the baffle this weekend.
I am embaressed to say the port is a 4" Precision flared port.

Have you considered a sealed box. Sealed enclosures can have advantages in transient response and bass definition. You might find this interesting:

tempest.pdf

F3 would be 29Hz in a 3 cu.ft. with a second order roll off. Not bad. With all that space though you could probably shoot for a Qt of 0.6 (better transients).

[---k---]

Forte,
I know you can't read the attached graphs, but I'm not sure how to get the info in a format you can read. Sorry. The graphs are from Unibox of your configuration versus the configuration Kevin suggests. Basically, yours has a medium size hump centered on the tunning frequency and a lot of port speed. Kevin's is flat then a gentle roll off.


Kevin,
Looking at these graphs, I think I'm missing something. Frequency response can't be everything, can it? Looking at these graphs from about 30hz up, they are exactly the same. Port noise is obviously different for a 4" vs 8" port, but... Would you really in reality get port compression that would just kill the port output? What am I missing?

[Forte_II]

I will try sealing the fireplace and see what it is like. I think 100% fill in the fire box, the chimney will just have to be unstuffed.
Thanks for modeling that for me. will unibox export to a txt file? That is how I do it in TrueRTA and WinISD. I am curious about the port issue too. Kevin what do you think?

[Kevin Haskins]

I will try sealing the fireplace and see what it is like. I think 100% fill in the fire box, the chimney will just have to be unstuffed.
Thanks for modeling that for me. will unibox export to a txt file? That is how I do it in TrueRTA and WinISD. I am curious about the port issue too. Kevin what do you think?

I'm modeling your 23 ft^3 and a 4" PSP port would have to be 1.5" to tune it to 18Hz. So... something doesn't add up. How long of a port are you using?

I'd second the sealed box. You have a very non-standard enclosure so its difficult to accuratly model a ported alignment. A sealed alignment will be much more forgiving.

[Forte_II]

Well, something is off. I am off on the tuning freq. or the vol. is much less than estamated. I took 9.25" out of the Precision flared port. So without knowing how to calc. lenth with large flares... I figure 7.75" based on 17" - 9.25" = 7.75".
So I think the vol. is less than I guesstamated and the tuning point is lower. I will get a resister tomorrow and get the real" tuning point. After some thought I don't think I would like a sealed alignment. I am after good HT LFE performance...

[Forte_II]

Oh, yeah... How much effect does port size have on port performance? Not noise but actual affect on speaker output.

[ThomasW]

All the port does is create the resonant frequency for the Helmholtz resonator.

The port diameter inpacts the speed of the air moving in the port. Larger the diameter of the port the lower the Mach number.

For a 15" driver one usually doesn't need much more than a 6" flared port.

[---k---]

Get a Behinger DEQ2496 and then you can boost the low frequency of a sealed box using a Linkwitz Transform (LT) - could make you very happy with the deep bass.

I haven't been following the woofer widget. Is it going to do LT? I thought I read that.

[Forte_II]

I ordered the PQ2 from Elemental Design. It was design for there sealed subwoofers... It has a Hp filter and 2 bands of Parametric EQ. Can I use this to do a LT?

[ThomasW]

I ordered the PQ2 from Elemental Design. It was design for there sealed subwoofers... It has a Hp filter and 2 bands of Parametric EQ. Can I use this to do a LT?

An LT requires the use of shelving filters not just regular bands of parametric EQ.

[Kevin Haskins]

I ordered the PQ2 from Elemental Design. It was design for there sealed subwoofers... It has a Hp filter and 2 bands of Parametric EQ. Can I use this to do a LT?

As Thomas said, its not an LT (shelving filter) but you can still extend the bottom-end with one of the bands of PEQ. The thing is, you need measurement tools also to figure out how to set them. You can dowload a stepped sine wave signal to burn onto a CDR and then use the Rat Shack meter to get a rough idea of what your getting in-room. Your burning one of your bands of PEQ to extend the response but it may give you what your looking for.

[cjd]

Unibox is an Excel spreadsheet.

Under the pretty pictures are simple columns and rows of raw data. Might help?

[Forte_II]

Thanks, I have all the measureing equipment and TrueRTA...I just have to do the measureing when no one is home... I am sealing the enclosure better today and getting the port tuning as well as some in room FR.
I have unibox. But It is not Jaws friendly. I cant figure out how to get Jaws to find let alone activate the Macro buttones. It just doesnt reconize them. I would like to say I think the Tempest is a great driver and it sounds awesome. I am just a perfectionist... Most people would be satified with it as it is now.

[ThomasW]

Just a quick LT follow up. As massive as this box is there's no reason to use a LT circuit. These are primarily used when the box is too small and the goal is to create a low "Q" design. Your box "Q" is going to be very low from the onset, since the box is so big.

[cjd]

Ooh, the macros. You may have to alter the settings to get them to run (not sure what version of Excel you've got) - also, they do require Windows as the scripts don't run on a Mac. But it's NOT set up for JAWS I am certain. Hadn't considered that. Isn't that always the problem though?

Regardless, someone should be able to scrub the data if you're curious.

[Forte_II]

Ok, thanks everone...
Now useing 2 10 ohm resister in series to 20ohm...Is this ok? Second No matter what I do with the port the trough bottoms at 38hz. 1.5" or 13" same 38hz trough. Is that some resonent freq of the enclosure?

[Dennis H]

Ok, thanks everone...
Now useing 2 10 ohm resister in series to 20ohm...Is this ok? Second No matter what I do with the port the trough bottoms at 38hz. 1.5" or 13" same 38hz trough. Is that some resonent freq of the enclosure?

Yes, 2 resistors in series is fine.

Try sweeping lower in frequency like down into the single digits. You want the trough between the two sharp peaks. I suspect you're finding the trough above the second peak. 38 Hz is way too high for that driver in a big box.

[Forte_II]

I went down to 8hz. I must be doing something wrong. Oh well, I just finished resealing the baffle. after it sets up I will try it sealed.

[Forte_II]

Edited:
OK, No subsonic filter this time! Nice response just like it should be...Matchs what I am hearing too.
This is sealed and I think I will keep it this way. Will adding some fiber glass to the inclosure. (It is empty right now) make much difference? How much effect would that have at these low freq?

[Kevin Haskins]

Your fireplace sucks as an enclosure. ;-) It probably has a lot of small holes, not just one.

[Forte_II]

Yeah, I figured that out...:P I cant seem to reconcile what I am hearing with what is in the measured data. I can hear very deep bass, a 20hz sine wave rattles everything in the house. Oh well I am happy and will play around with a real box in Jan.
Edit: The fireplace doesnt suck... The tester does!

[Johnloudb]

Yeah, I figured that out...:P I cant seem to reconcile what I am hearing with what is in the measured data. I can hear very deep bass, a 20hz sine wave rattles everything in the house. Oh well I am happy and will play around with a real box in Jan.

What frequency are you crossing over at? 60Hz? It's only down about 13dB at 20Hz (in reference to 60Hz, which is -3.4dB in the "sealed" fireplace). It looks like your getting an early roll off because of the really large enclosure. Anyway, I agree, a box is the way to go when you can.

[Forte_II]

Fixed testing method... All data is now correct!

[Forte_II]

Now that I know how to do this! Here are some FR files...Sorry no pretty graphs just raw data.
Now I can see how room modes mess with bass! EQ is next!

[ThomasW]

Now that the testing method is fixed, let's see a sweep with the mic placed 1" from the dust cap.

[Forte_II]

As you wish...
There is a xover cutting out the highs... This is not the natural rolloff of this driver...

Now that the testing method is fixed, let's see a sweep with the mic placed 1" from the dust cap.

[Kevin Haskins]

Looks like its still rolling off faster than it should in 23 cubic feet. How certain are you about the volume? Also... do you have a subsonic filter of some sort on it? What are your electronics?

[Forte_II]

Kevin Haskins Looks like its still rolling off faster than it should in 23 cubic feet. How certain are you about the volume?
At this point I am not certain of anything that has to do with this "enclosure". It could be as little as 13ft. Depending on what the P/O did with the chimney.
Also... do you have a subsonic filter of some sort on it? What are your electronics?
I am still waiting on the ED PQ2 to ship...Right now it is just a Pro amp fed off the subout of the reciever. Dont forget this is now a sealed alignment.

[Kevin Haskins]

Kevin Haskins Looks like its still rolling off faster than it should in 23 cubic feet. How certain are you about the volume?
At this point I am not certain of anything that has to do with this "enclosure". It could be as little as 13ft. Depending on what the P/O did with the chimney.
Also... do you have a subsonic filter of some sort on it? What are your electronics?
I am still waiting on the ED PQ2 to ship...Right now it is just a Pro amp fed off the subout of the reciever. Dont forget this is now a sealed alignment.

You should be able to use a shelving filter to adjust the bottom-end to taste. Its a fairly simple adjustment. Doe the ED PQ2 have a LT?

[Forte_II]

Kevin, No it doesnt. I thought I was going to run this vented when I bought it. Cant I just EQ it to taste? thanks, off to research selving filters.

[Kevin Haskins]

I'd look at a room measurement in your seating positions. You need to consider room gain also which is going to vary considerably room to room. If you want more deep bass, the only way to get it within the confines of using a sealed box is to EQ it. Just keep in mind that you will find the output limits of the driver quickly. :-) If you have a band of PEQ on that ED PQ2 you can use one of the bands to extend the low-end. It doesn't work as well as shelving filter because you make a hump, instead of a shelf but if you center it low enough in frequency with a broad Q you can achieve almost the same thing.

[Forte_II]

Ok, I am going to play around with eq and see how it goes... But I may be building a vented box in Jan. Maybe the 9ft^3 you suggest for this driver.

[Forte_II]

Well I decided to use one of my 1/3 oct EQ's to just see what I could do until I get the ED PEQ2... You should try EQing a sub as a blind guy! :P Test....export data...read data...make small adjustment...repeat a Jillion times...LOL Then your EQ looks (That is how I imagine it from the way the sliders feel) like the New York skyline pre 9 11!
Here is a file of the response at my chair

[ThomasW]

Well it's really flat if that's the goal.

Frequently people like to create what's called a house curve, that's something contoured to the owners taste, and they usually aren't flat.

[Kevin Haskins]

Yea.... f3 of 12Hz. Be careful with the big bass movies. ;-)

Now you see the logic behind the Widget. There is something to being able to push a button, take a measurement and adjust the PEQ seeing how it affects the room measurement all within the span of minute or two.

[ThomasW]

Now you see the logic behind the Widget.....seeing how it affects the room measurement all within the span of minute or two.

I imagine being blind makes seeing and using the GUI somewhat problematic...

[Kevin Haskins]

I imagine being blind makes seeing and using the GUI somewhat problematic...

We need a version that is voice activated! I didn't realize you where blind as in blind. Forgive my ignorance.

[cjd]

Kevin, if you're serious about considering interface improvements, holler. I probably can't help much with implementation, but getting the features to work right for all users, more possible. And general usability.

It doesn't have to be voice activated, it needs to interact via something other than visuals. JAWS does a pretty good job with software that's well written. Even a "view graph as pure data" setting with a properly tabular data assemblage could work.

I sometimes think the blind see more easily than the rest of us. Different things, of course. We get so used to sight that we actually forget to USE it so often.

C