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Where's the (low) bass? (Read 3015 times)
BrianInCO
Ex Member



Where's the (low) bass?
02/06/06 at 02:43:12
 
Hi all,

Some time ago I subscribed to Steve's website and got the 10" DB plans.  Built the box itself back in April or May when I had a couple down days at work, but haven't gotten around to putting anything in it until now.

So far, I've tried it with two PPI C2-108 10" subs running isobarik, one of the PPI subs (current setup) and with a MTX Blue Thunder Legend 10" sub.

I'm hopeful, but not really impressed.  The MTX was unlistenable, which is odd, as it's specified as being compatible with several similar bandpass designs.  

The PPIs do a little better.  I started with the iso configuration and it was very loud in the upper bass region, overpowering and bloated, just what I'd expect from a small single-reflex bandpass box.  It's better with the single PPI at 8 ohms mono (magnet in the rear chamber) but is still not really satisfactory.  

Little to no bottom octave and overpowering upper bass.  It adds dynamics, but I think one of the PPIs in a 1.0cf sealed box would put out more low end.

Am I going to have to actively boost the bottom octave?

Box is built to prints.  I'm a professional cabinetmaker now working in production engineering.  Everything is tight and was cut on accurate machinery, I didn't make this with a jigsaw or something.  Insert currently positioned just at the top of opening.

System:

2005 Hyundai Elantra GLS Sedan
Factory CD Player
Coustic XM-1e Crossover, set to 18 db/oct low pass @50Hz
Alphasonik MA-2035 Class A amp at 35 wpc (mids and highs), under driver's seat
Earthquake 6.5 Coaxes in front doors (forget model, they're big)
1 Farad Phoenix Gold Cap
2 Gauge to dist block @ driver's seat, 4 Gauge from there to trunk
Linear Power 2202 at 220w x1 (@ 12V) running in mono, in trunk
10" Deathbox

Appreciate any advice.  I have a pretty good idea of what I'm doing (CASA/VSA and MEA certified back in the 90's and a grad of Mobile Dynamics) but not sure what's happening here.  Just need a more compatible driver?  Lower expectations?

I made a single-reflex BP years ago with one OZ Audio free-air 8 that put what I'm getting out of this to shame.

Brian
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J_Rock
Ex Member



Re: Where's the (low) bass?
Reply #1 - 02/06/06 at 04:24:25
 
I assume you have tried tuning the box while playing the driver.  Its amazing how much an inch of movement of that baffle does.

If the box begins sounding better and better, but all of a sudden your baffle is at the top, stuff the sealed chamber.

I have an Infinity in mine and it sound very good.  So I don't know how those other subs would compare with it....


Anything else I can offer would be to double check it is built to plans and is sealed up. But you already did that  ;)
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« Last Edit: 02/06/06 at 04:25:44 by j_rock777 »  
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Adrian D.
Ex Member



Re: Where's the (low) bass?
Reply #2 - 02/06/06 at 05:23:36
 
i also have an infinity. my insert is at the top of the half-moon. it plays down to 35hz (-3dB ?) in a room. i love it as a HT sub, but it gets better with music.
i haven't tested it in a car.
maybe you've got some weird cancellation in the trunk ???
try rounding the edges of the half-moon. imho, that makes the port appear longer, so you'd prolly get a bit lower tuning.
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« Last Edit: 02/06/06 at 05:24:02 by adi_ro »  
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Hotsauce
Ex Member



Re: Where's the (low) bass?
Reply #3 - 02/06/06 at 22:20:52
 
Try moving the insert to cover half the port.

Your PPI are oonly 8 ohm?  Thats part of the problem then, they aren't drawing as much power a dual 4 ohm coils wired parallel.

John C.

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60ndown
Ex Member



Re: Where's the (low) bass?
Reply #4 - 02/06/06 at 22:52:29
 
all 3 of my dbs played very low and very accurate ? keep playing with it.
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BrianInCO
Ex Member



Re: Where's the (low) bass?
Reply #5 - 02/07/06 at 00:25:00
 
Your PPI are oonly 8 ohm?  Thats part of the problem then, they aren't drawing as much power a dual 4 ohm coils wired parallel.

John C.


John,

That's true, but it's not a fantastic idea to run a Linear Power 2202 at 2 ohms mono, it's a voltage amp.  I like my shiny rails of TO-3 transistors unblackened and the power supply toroid intact.  The DB certainly was louder in the 4-Ohm mono isobarik configuration, but not in a flattering way, very boomy and uncontrolled.

To be fair, this is not a high budget project.  I selected the PPI's because I bought them at an auction for $30 several years ago in mint shape, and they were just laying around in hard-to-tell-from-new condition.

All the components in my system, down to the wiring, cost less than $200 total.  So I'm not expecting miracles, but it seems like it should do a bit better.  I have a 15" CV Vega 154 that's going in there aperiodic as soon as I pick up the requisite parametric EQ and find the time to fab the box, so this was intended to provide some low end in the meantime and just be something to toy with a bit.

I played with it a lot over last weekend, several hours total.  I will do some more movement of the insert and see how that changes things.  Not sure cancellation is the issue, as I've moved the box about and fired the port towards the driver's seat (where it is now), towards the side trunk wall, and towards the rear of the car.  I've tried reversing the speaker polarity.  Some changes in the sound were obvious, but not much of an improvement.  I'm happiest and it's the least boomy firing towards the driver's seat in the proper phase.

Here's some T/S params from the web, maybe this will shed some light on things?

   * Size:  10"
   * VAS: 68.14L
   * FS: 25.24Hz
   * Impedance: 4/ 8 ohm
   * X-Max: 9.97mm
   * Power Handling: 500 watts (max)
   * Sealed Box: .5-1.0 cu. ft.
   * Ported Box: .75-1.25 cu. ft.
   * Displacement: .065 cu. ft.
   * Voice Coil: 4 Layer TIL
   * Peak Excursion: 17.25mm
   * Sensitivity: 89.64dB

It's a pretty robust driver, at least compared to more traditional woofers.  It's not designed to be a W7 or something.

I'll play some more and report back, thanks to all for your replies!

Brian
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« Last Edit: 02/07/06 at 00:31:07 by BrianInCO »  
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Hotsauce
Ex Member



Re: Where's the (low) bass?
Reply #6 - 02/07/06 at 01:34:07
 
I have mine with the port facing back, loading off the rear, it is such a dramatic difference from pointing forwards.  Forwards it sounds like its lacking the lowest octave that shakes the seats and floor.

My box is lowpassed at 80Hz, and subsonic set at 20Hz.

John C.

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BrianInCO
Ex Member



Re: Where's the (low) bass?
Reply #7 - 02/07/06 at 15:18:39
 
OK, a quick update.  I now have the insert covering about 3/4" to 1" of the top of the port.  That helped the midbass boominess out a good deal and really tightened things up, but the bottom octave is still lacking.  I'm going to play some more.

Last night I fed the T/S params of the PPI woofer into BassBox.  I can't come up with anything I like.  The optimum single reflex BP is small, about the size of the DB, but it has a huge peak at 120hz.  Something like 9db.  That jives with what I heard.  It was so bad that at 18db/oct at 50hz lowpass, it was still pulling the image backwards from the front stage.  I tried modeling some interesting iso vented alignments with the PPIs too, and the response looks great, but the cone excursion is off the map and power handling is about 8 watts below 45Hz.  Think I may just get things as good as I can with sliding the insert and call it good for now.  Doesn't seem like a very compatible woofer.

Crutchfield has the Infinity Ref 10 right now for $59.99.  I might jump on it, but it's even cheaper to stuff my 15" CV into the 32-liter sealed box I modeled last night and have predicted in-car response that's nearly flat to 15hz.  The CV never gets even halfway to Xmax with a 500W input according to the model.  Going to give that a try first before I get interested in the Infinity, thanks for all the advice!

Brian
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Adrian D.
Ex Member



Re: Where's the (low) bass?
Reply #8 - 02/07/06 at 17:52:33
 
good thinking. the db-10 is somewhere around 50 l total volume, so the cv in sealed would take less space.
anyway, a ten is a ten. you can't expect the same response like you would get from a 15...
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boydon_lepasci
Ex Member



Re: Where's the (low) bass?
Reply #9 - 02/08/06 at 00:18:51
 
Just one more thing that someone eventually gets around to: once you have found what baffle position sounds best, you need to seal it in place no matter how air tight you think you built it. Then put a hurt on it with the amp.
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