# I just dont understand...



## kmatthews8 (Aug 9, 2010)

First off, I'm 40, not 17, but anyway - here's what happened. I have a 2011 Hyundai Sonata. Using factory nav HU with AudioControl LC8i, Hertz HSK 165 in front off a bridged JL 300/4, Morel Pulse 6.5 mids in back, and a Boston Acoustics SPG-555 sub off a JL HD750/1. Previously, the sub was pretty strong, yet very tight, in a pref-fab 1.25 cu ft sealed box (Recommended is 1 cu ft). I decided to add the Boston SPG-TR passive radiator, which according to Boston will add 3db of output, plus have my local shop build a better quality sealed box to the exact specs from Boston. It SUCKS now... Cant understand where my bass went??? There are no air leaks, the sub just seems to have very little output now. Also, it doesnt seem to take very much at all for the passive radiator to start making a "popping" noise, as if it is being overdriven, even though there is VERY little output. It make no sense to me. If I am just an idiot and missing something obvious here, by all means, talk to me like I'm 4 and tell me. Short of just trashing a perfectly built box and starting over, I'm at a loss. This sub was quite strong before. 
Thanks...


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## Notloudenuf (Sep 14, 2008)

So to try and narrow this down you added the passive radiator AND had the new box built at the same time?
Does putting the sub back in the old prefab box sound better?


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## Oliver (Jun 25, 2007)

The passive radiator can add some lower notes.

_It is flexing_ 

U need *more power now* 
_
more give = less output_


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## kmatthews8 (Aug 9, 2010)

Yes, added passive radiator and new boxat same time, but threw out old box before i actually listened... more power? Was afraid someone would say that. I know my 750 aint exactly a beast, but shouldnt it be enough...? Gonna try removing PR tomorrow and temporarily sealing the box back just to see what happens. I juzt cant imagine that adding the PR and the smaller boxwould've made THAT much difference. Any other thoughts?


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## Oliver (Jun 25, 2007)

Building and Designing Enclosures | KICKER



> Any leaks or flexing will cause cancellation, resulting in reduced output. Enclosures should be built with very dense and heavy wood


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## Mathew (Dec 20, 2010)

Oliver said:


> The passive radiator can add some lower notes.
> 
> _It is flexing_
> 
> ...


I disagree with this, going from a sealed enclosure to a ported enclosure is more give, but does not require more power to achieve the same output. Furthermore, according to Boston's response charts, there is 3db additional output when adding the PR.

There is a difference between a tuned enclosure and one that is flexing because it was not built well, which is to say that the possibility of it fexing is there, but typically not enough to make someone say, "What happened to my bass?".

After reading through the literature, the few possibilities I can come up with are:

1) The enclosure was supposed to be 1 ft2 gross according to the manual. I think most installers would assume that this be the net airspace unless finding the astrics in the description.

- if it is the wrong airspace, the tuning frequency could be too high, the f3 is already at 33hz as recommended, if it got something is wrong, then that may have pushed it up too high and that might be what you are missing. If you measure and find the airspace wrong, try adding polyfil to increase, and chunks of wood to decrease the volume that the sub is "seeing" before chucking the box.

2) The mass is adustable on the PR. Maybe it is tuned too high, you can double check that before chucking the box.

3) The silly, but worth checking, did the sub get wired as before? Did one voice coil get missed, did it get wired in series instead of parallel?

This enclosure should have better output than your last one without more power imo.


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## Eastman474 (Jan 8, 2010)

Mathew said:


> I disagree with this, going from a sealed enclosure to a ported enclosure is more give, but does not require more power to achieve the same output. Furthermore, according to Boston's response charts, there is 3db additional output when adding the PR.
> 
> There is a difference between a tuned enclosure and one that is flexing because it was not built well, which is to say that the possibility of it fexing is there, but typically not enough to make someone say, "What happened to my bass?".
> 
> ...


x2 ..... I've heard a couple sinarios where the PR was tuned wrong and output suffered tremendously.. However my first thought would be enclosure airspace wrong.


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## n_olympios (Oct 23, 2008)

Mathew said:


> I disagree with this, going from a sealed enclosure to a ported enclosure is more give, but does not require more power to achieve the same output.


That's because the enclosure itself has bigger gain. 

I agree on all the other stuff you wrote.


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## Notloudenuf (Sep 14, 2008)

have you tried flipping the phase on the woofer?
That is the #1 thing and easiest to try.


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## aeon (Oct 11, 2007)

was anything on the amp touched?


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## kmatthews8 (Aug 9, 2010)

its at the shop right now being experimented with (I completely trust them..). Airspace is correct, triple checked the measurements. Its a single voice coil, so thats not it. I guess its possible that there could be some flexing from the box, but it really seemed very well built, plus its from the best guy at the most reputable shop in the entire area. Never even thought to check phasing - hopefully he did...

Anyway, when I dropped it off this morning, he told me that he still has my old box so he's gonna try multiple things and see what has the strongest improvement. Its just weird. I've been involved in car audio for more than 20 years and I've just never seen this effect before. Mostly, I want it fixed, but my curiosity is piqued as well...


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## Eastman474 (Jan 8, 2010)

kmatthews8 said:


> its at the shop right now being experimented with (I completely trust them..). Airspace is correct, triple checked the measurements. Its a single voice coil, so thats not it. I guess its possible that there could be some flexing from the box, but it really seemed very well built, plus its from the best guy at the most reputable shop in the entire area. Never even thought to check phasing - hopefully he did...
> 
> Anyway, when I dropped it off this morning, he told me that he still has my old box so he's gonna try multiple things and see what has the strongest improvement. Its just weird. I've been involved in car audio for more than 20 years and I've just never seen this effect before. Mostly, I want it fixed, but my curiosity is piqued as well...


So what results did you get?


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## my6x9s (Apr 15, 2009)

ok its a guess but there have been scenarios where you are trying to recapture the back waves of your woofer will cause a out-of-phase effect in a trunk and take sound levels away from the end result. i build horns and we work on timing alignment so that you are harnessing the back waves to time close to or be with the front waves at a desired frequency. last build was a 10" RF hx2 that metered 145.1 at 32hz but bare in mind this was a giant horn and built for only one goal in mind... so read on 1/4 wave theory as i disagree with 1/4wave math but the theory is valid


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## kmatthews8 (Aug 9, 2010)

Apparently, that is pretty close to what is happening. I guess its basically cancellation. We are going to try adding a simple baffle to isolate the front from the back. What happens right now is this: play a bass heavy track, get very little. Hit the trunk release to slightly open the trunk and WOW - massive difference. I've never experienced cancellation quite like that... will be trying the baffle tomorrow...


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## subwoofery (Nov 9, 2008)

You have the 555 and the TR on opposite face right? Did you try to turn your box 90°? Did you try to move your box around the hatch? Closer to a side? Away from it? 

Play with it and report back. 

Kelvin


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## sqoverspl (Aug 17, 2009)

my6x9s said:


> ok its a guess but there have been scenarios where you are trying to recapture the back waves of your woofer will cause a out-of-phase effect in a trunk and take sound levels away from the end result. i build horns and we work on timing alignment so that you are harnessing the back waves to time close to or be with the front waves at a desired frequency. last build was a 10" RF hx2 that metered 145.1 at 32hz but bare in mind this was a giant horn and built for only one goal in mind... so read on 1/4 wave theory as i disagree with 1/4wave math but the theory is valid


Off topic but how much power was on the hx2 and how much port area at the mouth and what was the tuning?


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## Sleeves (Oct 22, 2010)

I don't recall you mentioning the orientation of the PR in relation to the woofer, but in the limited experience I've had using PRs I've found they work well on a plane that is 90 degrees away from the subwoofer's plane. That seems to give the most sound reinforcement with the least cancellation. It also helps to try turning the box in different directions to see which way sounds the best.


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## kmatthews8 (Aug 9, 2010)

the PR is on the opposite side of the box from the woofer, per Boston's recommendation. The box has been moved and turned around in every possible way with very little difference. Will be working on it again tomorrow, I'll let ya know the final outcome.


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## my6x9s (Apr 15, 2009)

sqoverspl said:


> Off topic but how much power was on the hx2 and how much port area at the mouth and what was the tuning?


600w from a jbl 600.1(cheap amp) the port mouth is 12"x16"ish sorry dont have it here any longer and the start of the taper from the inner chamber is 12"x3/4" total travel length before exit at the mouth was 23' of folding horn
it was also in a single cab lil pick-up blow though style box


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## Sleeves (Oct 22, 2010)

Take it as you will, but I'm not keen on "Boston's recommendation". I would put the PR 90 degrees away from the main driver and either point the PR towards the corner of the trunk or build a loading board to cover the PR with a slot opening firing the same direction as the main driver. If i went the loading board route I would design with a horn-like taper (maybe 2" at the closed end and 4-6" at the opening).


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

kmatthews8 said:


> First off, I'm 40, not 17, but anyway - here's what happened. I have a 2011 Hyundai Sonata. Using factory nav HU with AudioControl LC8i, Hertz HSK 165 in front off a bridged JL 300/4, Morel Pulse 6.5 mids in back, and a Boston Acoustics SPG-555 sub off a JL HD750/1. Previously, the sub was pretty strong, yet very tight, in a pref-fab 1.25 cu ft sealed box (Recommended is 1 cu ft). I decided to add the Boston SPG-TR passive radiator, which according to Boston will add 3db of output, plus have my local shop build a better quality sealed box to the exact specs from Boston. It SUCKS now... Cant understand where my bass went??? There are no air leaks, the sub just seems to have very little output now. * Also, it doesnt seem to take very much at all for the passive radiator to start making a "popping" noise, as if it is being overdriven, even though there is VERY little output.* It make no sense to me. If I am just an idiot and missing something obvious here, by all means, talk to me like I'm 4 and tell me. Short of just trashing a perfectly built box and starting over, I'm at a loss. This sub was quite strong before.
> Thanks...



I bet you are seriously over-driving it now... The PR loosens the box a lot.. I mean you are adding a flexible diaphragm to the box.. 

Overall power handling is going to drop... 

You'll end up more like IB with the power, meaning a LOT less will get you to the mechanical limits of the woofer/PR..


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## Oliver (Jun 25, 2007)

http://www.diymobileaudio.com/forum...ical-advanced/94754-trunk-open-more-bass.html



> Apparently, that is pretty close to what is happening. I guess its basically cancellation. We are going to try adding a simple baffle to isolate the front from the back. What happens right now is this: play a bass heavy track, get very little. Hit the trunk release to slightly *open the trunk and WOW *- massive difference. I've never experienced cancellation quite like that... will be trying the baffle tomorrow...


Read Andy's post I highlighted from another thread from a long time before.

If I look I might be able to find some more stuff on this from 2,000 on Richard Clark's old posts.


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## kmatthews8 (Aug 9, 2010)

In case anyone cares about the final outcome of this, I ended up adding a JBL MS-8 and now, holy hell - I have retarded bass.... what a massive difference that little thing made...! Anyway - thanks again to all who tried to help!


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## subwoofery (Nov 9, 2008)

Strange... Doesn't bother you that you still don't know what happened? 

I know I would lol

Kelvin


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## Potbelly (Nov 23, 2010)

subwoofery said:


> Strange... Doesn't bother you that you still don't know what happened?
> 
> I know I would lol
> 
> Kelvin


 feel me?

"your bass is gone from the box we built ya. but hey! we can give it right back to ya for the price of a Ms-8!"


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

kmatthews8 said:


> In case anyone cares about the final outcome of this, I ended up adding a JBL MS-8 and now, holy hell - I have retarded bass.... what a massive difference that little thing made...! Anyway - thanks again to all who tried to help!


And all it cost you was 700$...!!!!












I can almost bet the MS8 cut output gain to the sub amp by 1/2 or better.. did you change your gains at all with it's install?? 

(Will we ever know?)


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## chapdawg1971 (Mar 8, 2010)

^^^^THAT is exactly what I was thinking!!!! Wait??? Eff No!!!


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## kmatthews8 (Aug 9, 2010)

for the record... its 100x stronger and cleaner now than it ever was, plus all the other benefits of the MS-8. I was looking at it already before this happened.


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