Cannot get a flat response below 50hz?!

[VWBobby 10+ year member]

I am needing a little help designing a box for a tricky sub. The sub is a Massive Audio Hippo 122.

Specs here:

View attachment 26546049

What I'm finding is .606 CF @ ~38hz is a pretty flat response. If I use the recommended - around 2.6 - 3.0 @ 28 to 32hz, there is a nasty hump followed by a dip. No way to get a flat response in a typical recommended enclosure.

View attachment 26546050

Does in-cabin response (cabin gain) smooth out the plot? I am using WinISD, and I've read that it doesn't account for cabin gain somewhere... Is this true?

I have quite a few other subs that will model with a flat response down to 30hz.... Why does this one have such a weird hump for a sub with a 34hz Fs? Why is the output less than 1 of my 500 watt PG Ti 12's?? I will be feeding it 1500 watts.

Thank you

Click to read more...

 

[T3mpest 10+ year member]

No winisd does not account for cabin gain. Best way to figure things out is to compare a subwoofer you have used in that vehicle and model it as a measuring stick. Then you'll see the differences on paper and you can have an idea how it will sound. Generally if you want good SQ if you can get a slowly falling, but generally fairly flat response in winisd it'll be fairly flat once you get it into the vehicle. The response you posed it similar to many subs, american bass has several models that look like that in just about any ported box you choose.

Output is hard to say. WINISD won't factor in things like power compression so don't always fully trust it's SPL plot. A subwoofer on 1500 watts with a 3inch coil will likely be louder than a 2inch coil on 500 watts, assuming box sizes are fairly close. However, if may not be THAT much louder and that can be true sometimes. Cone area really does dictate a lot when it comes to full range loudness.

Anyway ask yourself do you WANT a flat response? Again graphing a setup you've liked in the past might illuminate what kind of response you want. If you find it's not something peaky like that, then maybe that's not the best sub for you. Many people go about things backwards, picking the sub then going for a response.. Best way to build a system you'll be happy with is to figure out first what room you can spare, what response you want THEN what sub can give that response in the room you have, along with sufficient overall SPL, that's the way to go. Not, "here is the woofer I want just because, here is the room I have , give me whatever end result you think is best" as you often see online ( the what size box and tuning for my sub threads)

Anyway reading the info on the hippo they said they designed it for a "fat bottom end" well that's exactly what you get with that. A huge hump down low near tuning.

 

[Beatin' 10+ year member]

If you're using winisd, change the Ql from 7 to 10000, then give the sub 0.75 cubes tuned to 30hz and see if you like that.

 

[bbeljefe]

Subs with very high EBP will model like that in large boxes. That sub will give you a nice flat curve in half a cube tuned to 40 but as you go up in volume and down in tuning, that whoop de doo is gonna form and then grow.

If you want a large box pick a sub with an EBP of 60-75. That bugger has is at 104, iirc.

 

[VWBobby 10+ year member]

T3mpest,

Thanks for the detailed reply!

However, it may not be THAT much louder and that can be true sometimes. Cone area really does dictate a lot when it comes to full range loudness.

In other words, if you have two 12" subwoofers, but one can reach 15mm xmax at 500 watts, and the other can reach the same 15mm xmax at 1500 watts, the output will be about the same? The total displacement dictates the loudness, with similarly tuned boxes/plots?

Anyway ask yourself do you WANT a flat response? Again graphing a setup you've liked in the past might illuminate what kind of response you want. If you find it's not something peaky like that, then maybe that's not the best sub for you.

Now I'm confused.... Don't I WANT a flat response? Otherwise the sound would be very "boomy" at certain frequencies? I listen to a wide variety of music from classic rock to dubstep and rap....I'm looking for a setup that doesn't peak real high at any particular frequency, but is loud between 28 - 60hz, if possible. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif A 4th order might be a better design for me, although more complicated to design and fabricate.. This is going into a '65 VW Bus, so I'm thinking the cabin gain would be somewhere peaked around 40hz.

If you're using winisd, change the Ql from 7 to 10000, then give the sub 0.75 cubes tuned to 30hz and see if you like that.

That made a huge difference. So a higher Ql means more "leakage" from the box? I'm not sure what this setting does... Why 10,000? I thought the type of box was factored in, so you wouldn't need to trick the program by using more leakage...?

I've never put this much thought into box design... I usually tune to around 30hz and adjust the size of the box to close to the manufacture's "optimum"... Now seeing the affect that tuning and box size has on a plot has me worried if I was loosing quite a few db in overall output. :-/

 

[hispls 5,000+ posts]

If you tune lower still you may flatten out that hump some, but I'd bet it won't sound much better IRL.

*edit*

Bear in mind 3db + or - is going to be adequately flat for normal listening. Your transfer function will likely give you a bit of a boost in the low 40's so the response won't look quite as bad with that modeled box in the van on an RTA.

 

[Beatin' 10+ year member]

So a higher Ql means more "leakage" from the box?

less leakage.

 

[T3mpest 10+ year member]

T3mpest,
Thanks for the detailed reply!

However, it may not be THAT much louder and that can be true sometimes. Cone area really does dictate a lot when it comes to full range loudness.

In other words, if you have two 12" subwoofers, but one can reach 15mm xmax at 500 watts, and the other can reach the same 15mm xmax at 1500 watts, the output will be about the same? The total displacement dictates the loudness, with similarly tuned boxes/plots?

Anyway ask yourself do you WANT a flat response? Again graphing a setup you've liked in the past might illuminate what kind of response you want. If you find it's not something peaky like that, then maybe that's not the best sub for you.

Now I'm confused.... Don't I WANT a flat response? Otherwise the sound would be very "boomy" at certain frequencies? I listen to a wide variety of music from classic rock to dubstep and rap....I'm looking for a setup that doesn't peak real high at any particular frequency, but is loud between 28 - 60hz, if possible. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif A 4th order might be a better design for me, although more complicated to design and fabricate.. This is going into a '65 VW Bus, so I'm thinking the cabin gain would be somewhere peaked around 40hz.

If you're using winisd, change the Ql from 7 to 10000, then give the sub 0.75 cubes tuned to 30hz and see if you like that.

That made a huge difference. So a higher Ql means more "leakage" from the box? I'm not sure what this setting does... Why 10,000? I thought the type of box was factored in, so you wouldn't need to trick the program by using more leakage...?

I've never put this much thought into box design... I usually tune to around 30hz and adjust the size of the box to close to the manufacture's "optimum"... Now seeing the affect that tuning and box size has on a plot has me worried if I was loosing quite a few db in overall output. :-/

That depends. Many people rave about DD subs, American bass, plenty of subs that will have a large peak in frequency response in their recommended boxes. Flat response isnt' everyones cup of tea. If you really aren't going for just loud, then yes, you do want a fairly flat response. As far as your question about displacement, that is sort of what I was referring too. Box size and cone area relative to it dictate a lot about response. More cone area tends to giver more overall output, more box space relative to cone area gives more output down low. 2 12's in 5 cubes may have the same SPL score on a termlab as 2 15's in 5 cubes, but it's because the 12's will be peakier over a smaller area, so peak scores would show similar readings, with the 15's sounding more balanced since they are louder everywhere else.

Anyway as others said the box looks better if you go smaller and tune a bit higher. I'd probably run a pair in a vehicle that size, 1.5 cubes at 35hz give or take a bit of space and a few hz tuning either way. If you can only run one, just cut it in half, .75@35. BBeljefe's reccomendation is also a somewhat flat response, although I'd go bigger and lower unless the space is an issue. They will both sound fairly flat, but my reccomendation will extend down with a bit lower, good for dubstep, but it will take up a decent bit more space. However, looking at what your initial box size was, that shouldnt' be an issue.