Why does my Sonosub sound louder with the top cap off??

5142 Views 13 Replies 6 Participants Last post by robbo266317, Jul 8, 2017

03roadking

Discussion Starter · Nov 3, 2011 (Edited)

Why does my Sonosub sound louder with the top cap off?? Updated with some Pics

Driver- Dayton Audio RSS390HO-4
Enclosure - 18" dia Sonotube at 8.8 cuf. Damped with pink insulation.
Amp - Behringer Inuke 3000DSP bridged to 4 ohm mono

I had the top cap off today while I was waiting for some glue to dry on it and I thought ehh what the lets see what it sounds like...

It sounded and felt awsome! It was filling the room with bass and I was actually feeling the bass like I had not before

Once the the glue dried on the top cap I put it back on and it sounded rubbish again. Really confused by this. Did I make the enclosure completely wrong? By taking the top cap off does it make the tuning higher and so I am just hearing and feeling the higher bass better?

I played the scene in war of the worlds where the pods comes out of the ground and it sounded awsome with the top cap off. Played it again with the cap on and it wasnt even close to sounding or feeling like it did with it off.

Any Ideas and thanks for reading!

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Mike P.

· #2 · Nov 3, 2011

What's the port size and tuning frequency and how tall is the sonotube ?

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03roadking

Discussion Starter · #3 · Nov 3, 2011

What's the port size and tuning frequency and how tall is the sonotube ?

I used the sonosub software to get my values.

I cut the sonotube to 5'3" 3/8

port size - was one 4" dia cut to 13" long with flares at each end.

You suggested that I was maxing that port out in another thread so I cut two new holes in the top cap and used 2 non flared 4" pvc pipes cut to 29". I then used a round piece of mdf to seal the old port hole.

The tuning frequency should be 16.6 hz according to Sonosub V2.03

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Mike P.

· #4 · Nov 4, 2011

My first thought is the tube is leaking air if you are able to take the top cap off. When you mounted the driver did you use foam tape to ensure a air tight seal?

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03roadking

Discussion Starter · #5 · Nov 4, 2011

I did use the foam tape when mounting the driver.

Last night I had time to play some test tones and sweeps with it and what is happening when I run it with the cap off is it must be raising the tuning frequency of the enclosure.

Cap off it sounds and feels awsome from about 40hz up to ~100hz. Anything below 35hz is really weak.

Cap on the sound and feeling from 15hz up to about 35 is awsome.

Any thoughts?

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Mike P.

· #6 · Nov 5, 2011

It doesn't make sense to me, hopefully someone will join in here.

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tonyvdb

· #7 · Nov 5, 2011

Im thinking it may have alot to do with the placement in the room. have you tried moving it around to a few other possible locations to see if its sounds better?

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03roadking

Discussion Starter · #8 · Nov 5, 2011

tonyvdb said:
Im thinking it may have alot to do with the placement in the room. have you tried moving it around to a few other possible locations to see if its sounds better?

I have only tried the corner to the left side of my tv and the corner to the right side of my tv. no where else really. The room is fairly deep and there is an open stair well going upstairs as well. I cant imagine that is helping me out either. I will try to get dimensions of my room tomorrow for reference.

Does anybody else think I have too much insulation inside the sonotube? Does it occupy more volume than I think it does?

Thanks for the help!

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ironglen

· #9 · Nov 7, 2011

03roadking said:
Does anybody else think I have too much insulation inside the sonotube? Does it occupy more volume than I think it does?

That looks like a whole lot of insulation in that wide a tube. I have thin eggcrate foam on the inside of my 24" tube and it doesn't fill it up nearly so much as yours. I recall a member stating that my sonosub really shouldn't have the eggcrate in it, saying it would decrease spl. I never took it out, so I really can't say either way, but if they were correct, then that may explain your results.

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robbo266317

· #10 · Nov 7, 2011

Sorry if I missed it. How high is the endcap from the top of the tube?

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Toffkanda

· #11 · Jul 7, 2017

From my little experience with enclosures. When the original volume is correct according to design and you load an excessive amount of stuffing or wall padding, you tend to lower the bass emphasis to the lowermost range leaving the sound lacking in fullness and upper/mid low frequencies. I don't know if this is valid and whether it applies in your case. If you have not yet stuck the stuffing to the wall of the cylinder, try playing it without any stuffing and the end cap on. This could give you an idea.

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robbo266317

· #12 · Jul 7, 2017

Toffkanda said:
From my little experience with enclosures. When the original volume is correct according to design and you load an excessive amount of stuffing or wall padding, you tend to lower the bass emphasis to the lowermost range leaving the sound lacking in fullness and upper/mid low frequencies. I don't know if this is valid and whether it applies in your case. If you have not yet stuck the stuffing to the wall of the cylinder, try playing it without any stuffing and the end cap on. This could give you an idea.

You do realise that this thread was last posted to six years ago.

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Toffkanda

· #13 · Jul 8, 2017

Really sorry! Don't know how I managed not to see the date while searching current threads. Awkward.

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robbo266317

· #14 · Jul 8, 2017

Hopefully they have already resolved their issue.

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