Recommended Tempest Box? (1 Viewer)

[Derek M]

I am finally getting around to designing and building my first DIY sub using a Tempest I bought last year and the 500W Parts Express amp I bought off of Brian a couple of weeks ago (Thanks Brian). While I have played around some with lspcad, I still think I need some help from those of you that already have a Tempest.

In my current system, I am running an older M&K sub (model V125) that is sealed. A very accurate and tight sounding sub. I'll use the new sub 70% home theater and 30% music. While I love the impact that a pure HT sub offers I still want very accurate and tight sound. Essentially I want very good low end extension but don't want to sacrifice musicality and accuracy to get there.

With that being said, what box type/size do you recommend? I was thinking the ported, mid Q design that Adire used to have in their docs. What would be ideal tuning to accomplish my goals? Lastly, what designs have worked for you?

Sorry to ask so many questions, just want to get it right the first time.

Thanks in advance.

 

[Owen Bartley]

Derek, I'm pretty happy with my Tempest. It's closest to the big design Adire provides, but I customized a bit to get it to fit where I wanted it. Basically a 210L ported box tuned to about 19Hz. It sounds great for movies, and it gets down fairly low at good volume. It might be a little boomy for more critical music listening, but mostly gets used for HT anyway.

The only reason I still want to upgrade is to get something that will dig down a little deeper and provide a little more output on the low end. If I were starting over I would just tune a bit lower. As it is, it really does shake things in the house (pipes in the wall, objects in cabinets in the next room), so it's a great way to get into the DIY arena, and is a hell of a performer for the money.

Good luck with your project, and keep us up to date!

 

[Robert_CA]

Derek,
If enclosure size isn't an issue, I belive that you may want to try Adire's Bessel alignment (Q=0.577 in a 230L cabinet). If it is an issue, you could try the Butterworth alignment (Q=0.707 in a 122L cabinet). I previously used my Tempest in a 214L ported alignment. It produced a whole lot of bass for HT but was not as well controlled as I would have liked for music so I sealed up the ports (it sounded better). You'll also find that with the PE amp, you will drive it nicely with plenty of reserve (actually 250 to 350 watts is enough to drive the Tempest well). You can also clean up your low end rolloff with the parametric eq if you go sealed. Check out Adire's white paper on Tempest sealed applicattions.

 

[Derek M]

So Robert with a sealed Tempest, could I reasonably expect SOLID low end extension down to 16-18Hz? From what little I have played with lspcad, it seems like a sealed Tempest starts rolling off well before 20 Hz and its output is down considerably at 16-18Hz. I know power won't be much of a problem with this amp so sealed is an alternative. I guess maybe I just want the best of both worlds...low end extension AND accuracy. Is this even possible?

BTW, size doesn't matter much (in this case), I am open to either large ported or smaller sealed. Just looking for the best performance.

 

[Derek M]

Owen, what sub are you considering going with now? I have considered just selling the Tempest I have and going with something newer, I'm just not sure if that makes much sense or not.

 

[Robert_CA]

If you're looking for really strong response in that range with a sealed sub, you could try a LT circuit. Also keep in mind that the software will not tell you how your sub will perform in your room (placement, room dimensions and room gain effect that). I still think that you will be ok with the larger sealed enclosure and using the eq on the amp or with the addition of a Behringer Feedback Desroyer. The other alternative is to go with a stronger driver (TC Sounds, SoundSplinter, Ascendant or Adire's newer offerings just to name a few).

 

[Owen Bartley]

Derek, here is a graph of my sub's in room respones before (blue) and after (orange) calibration with my BFD.



It starts to roll off around 25Hz or so, but the severity of the drop is probably due to the 19Hz centered rumble filter in my Adire AVA250 amp. I had thought about defeating the rumble filter completely, but after talking with tech support they confirmed that since my sub is tuned to 19Hz, that would be a bad idea, as drivers tend to get screwy below the box tuning frequency.

I haven't tried out my sub with the port closed, so maybe I'll give it some listening with a Nerf football stuffed in there and see if it improves for music. My suggestion to you would be to stick with the Tempest, it really is a great driver, especially for a first sub, and tune lower...say 15Hz? As long as your amp doesn't have a rumble filter built in that will negate the effects of a low tune. I guess it depends how much money you have available for the project. The real big boys can get pretty expensive, and so can LT circuits, and this driver is really great for the money. I ran my Tempest for 2 years as-is with just the level and phase tweaked and was happy, I just added the BFD in November as a small tweak.

I'm not really looking to replace my sub in the near future, it still blows any conventional subs I've heard out of the water, and friends love watching movies at my place. I am hoping to buy a house in the next year or two, and then when I can set up a more dedicated room I was going to look into a pair of Avalanches or something.

 

[Derek M]

Owen, thanks for the info. Unfortunately I can't see your frequency graph. Do you have this posted somewhere else so that I can view it?

 

[Owen Bartley]

Derek, that should do it. Switched hosting.

 

[Robert_CA]

I also agree that the Tempest is a good driver and you can still achieve most of what you're looking for with it. I just wanted to make you aware of some of the alternatives that are out there which may or may not be a cost effective option for you.
Owen's response graph illustrates the room's effect(s) on his Tempest as well as what can be acheived with equalization. In most cases you will get another 2-3 db of low end gain from your room even without equalization. Most people will use a BFD with it's multiple filters to equalize a sub because the BFD can give you the increased flexibility needed to "dial in" the sub's response to the room.
If you own the PE 500-watt class G amp, the parametric equalizer's frequency adjustment range is from 18 to 80Hz so you could try to get close to your target using it at 18Hz if you limit the bandwidth of your boost but there is an obstacle. The problem is that there is also a 3rd order subsonic high pass filter (f3) @ 18Hz. However, this cutoff can be modified to lower it to 12Hz (I could give you the link to this if you wish to explore it). You could modify the amp's filter and use the Tempest in a larger sealed enclosure. That way you can retain the tight response you prefer while getting the deep response you are seeking given the proper equalization. A larger enclosure has a gentler roll off and would require less equalization (and power input) from the PE amp. Some prefer to use much smaller sealed enclosures (2 cu.ft. or less) but they require more boost (hence much more power input) to acheive a flat response (750-1000+ watts).

 

[Derek M]

Robert, thanks for the tremendous input you have provided. Yes I would definitely like to see the link to lower the freq at which the rumble filter kicks in. So you think that sealed would be ideal for what I am trying to accomplish? It seems as though most go ported with this driver so I just want to make sure that would be best for what I am trying to accomplish. Thanks and have a great new year.

 

[Derek M]

Owen, thanks much for posting the graph. Definitely some "food for thought."

 

[Owen Bartley]

That sounds like it could work really well for you Derek. I would recommend that you do lower the rumble filter to 12Hz, and tune your enclosure low. My amp starts stealing my subsonic bass, which makes it hard to even compensate for with EQ, but if yours kicked in at 12Hz, I think that's a very reasonable filter for a Tempest, still giving you some driver protection, but allowing the low notes to appear.

Then down the road if you decide you want a little more control and tweakability, you can pick up a BFD and boost your low end like I did in my graph, except yours would be considerably lower. Also, you will have a lot of headroom with that amp, so I wouldn't be afraid to kick in some extra boost down low. I'm only pushing 250W so I didn't want to boost much, if any, and I only added a bit.

Edit: Ah, sorry, I read Robert's post too quickly, and thought we were still talking about a ported enclosure. A larger sealed box should work well too, and you can apply my same points about the BFD and EQ'ing that box. Typically, as mentioned, a sealed sub will need more EQ to get down lower, but you have the power available to do it.

 

[Robert_CA]

Derek,
Here is the link to the PE amp modification. I hope that it's still active. If it's not, let me know. I have a hard copy of it and I can send it to you. Let us know how it all turns out. Cheers!

http://maxhawk.bravepages.com/projects/subwooferamp/

 

[al lout]

Here is the graph of my sealed mid-q (122L) measurements.
I'm extremely happy with it. Lots of work but it's well worth it and it's kinda fun doing it.

Al,

 

[Derek M]

****

 

[Derek M]

Al, thanks. Maybe I am doing something wrong in lspcad but according to the program, the -3dB point was at 31.84 Hz and the graph continues the decline from there. This was for the mid-Q sealed design that you are using. However your graph is not at all indicative of this. On the graph in lspcad that I am looking at, it supposedly (assuming I am using it correctly) is showing the estimated in-room response. While I understand that the program has it's limitations, your graph is showing solid response to 20Hz. I don't mean to question your results, but this just doesn't seem to match up with lspcad. So what is your secret? Also what amplifier are you using in this example and do you have an eq that is affecting your uncorrected graph?

 

[Derek M]

Ok, so after looking at the site that shows how to lower the cross over point for the rumble filter, I decided that even though that would be ideal, I am just not going to take chances on opening up a brand new amp and solder in new components. Too much risk with my limited abilities on a $300 amp.

So with that being said, I will live with the 18Hz filter built into the amplifier. I assume that if I decided to go ported, I would want to stick with 18 Hz tuning at the very lowest but probably would be best to tune slightly higher...correct? Since I won't change out the rumble filter, does this have any effect on your recommendations? I have just been flip flopping on which to go with...ported or sealed. Obviously there are pros and cons to both...I just don't know which makes more sense. BTW, I really appreciate everyone's assistance and patience on this.

 

[Joe L.]

Derek,

I built a 260L Sonosub using the same Adire Tempest driver you will be using. I tuned the enclosure to just under 17 Hz using a single 6 inch diameter port. I estimate the "Q" to be somewhere near 0.6

I paired it up with a Parts Express 250 watt plate amplifier. (The one without any bass-boost)

When I measured its frequency response at my listening position (About 10 feet away from the sub) I ended up with this un-equalized frequency response:


The roll-off on the bottom end is probably due to the rumble filter in the plate amplifier combined with the response of the driver. The roll off at the top end is because I had it crossed over at 80 Hz. I think you can see a "SOLID" low frequency response down into the 16-18 Hz range, in fact, my measured response was only a few dB down at 12.5 Hz and that was below the tuning frequency of my sub.

I don't think you will be unhappy with the in-room low end frequency response with the Tempest driver. With a big enough ported enclosure, you will find it very easy to listen to with music as well.

Joe L.

 

[Derek M]

So Joe, with your statement: "With a big enough ported enclosure, you will find it very easy to listen to with music as well", I guess you are strictly recommending ported for the extra low end extension then. This is why I was leaning towards a ported enclosure, but al's plot above shows pretty solid response using a much smaller sealed enclosure. Was sealed even an option for you. While I don't necessarily mind going large and ported, if I can get pretty similar results with a smaller sealed box and only sacrifice some spl then obviously I want to consider this. Taking into account that my amp supposedly has a rumble filter at about 18 Hz do you see an advantage of one design over another?