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Maz4bz

TPAM10HTL tapped horn sub & Altronics PECC 10" woofer build

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Posted (edited)

Dear all,

I like to dabble in a bit of speaker building and really wanted to build a folded tapped horn for the experience of the build and what others have described favorably about the sound these make.

 

I had an old Altronics C3026 PECC 10" woofer laying around ...

 

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that I wanted to reuse and so landed on the Martinsson TPAM10HTL as a candidate to build.

 

Read here for some background and the refinement process from the designer Mr Martinsson.

 

Here are the very complete design drawings. I omitted the second (top) layer of the speaker motor board as I didn't need the additional depth because I wanted to mount the driver magnet side out for the cooling benefits for this configuration.

 

TPAM10HTL_overview.jpg.0ef0902c145abedaa439eaf3324bbd3e.jpg

 

The PECC woofer model's great in this enclosure. The original speced B&C driver will operate solidly down to 30hz but it costs $250 USD! As this was really an exercise of wanting to see how the modelled response translates into reality.

 

So here is the PECC's modelled response....

 

1024773573_Hornresp30cmTPAM10HTL.jpg.71d428133999fa7668fa6e0761c169e6.jpg

 

I call it 3db down by 40hz. Great for music. Might even do home theater with some room gain, andthe efficiency is super at 95db @ 1watt simulated input! 😀

 

The build was quite complex. Building a slot ported bass reflex is a breeze compared to this build. I followed this nice how to step by step guide at speakerplans.com.

 

Some obligatory build shots for fun....

 

IMG_20190324_213509900.thumb.jpg.dc9c1ae3771ec5d15a96e1fc392b5bae.jpg

 

 

IMG_20190327_092516022.thumb.jpg.c5b95de08c0df97cbbe25df7d2f03566.jpg

 

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In retrospect I may have added in additional braces  for the innermost baffles in the path. The energy generated by this thing is intense.....

 

I used 12mm CD non-structural ply from Bunnings. Cost of the sheet was $40 plus a few cuts. Bunnings will not cut a sheet down to anything less than 300mm which is a new safety rule. I learnt this on the Saturday morning I arrived at my local store to procure my ply!

 

Not to worry, the additional width makes virtually no difference to the performance. So, I went ahead figuring the extra internal volume might give me some extra efficiency and perhaps some additional extension?  At the very least it made mounting the driver a little easier once the box is all put together. The modeled response for the 30cm width is negligible as seen in the Hornresp sim above.

 

I did some measurements using the ground plane approach with my trusty Audyssey microphone that came with a previous receiver. If you have a look over at AVS Forum this mic has been proven as a good unit for subwoofer measurements, this post describes how I did my measurements.....  

 

Here's my measurement setup.....

 

IMG_20190327_135808458.thumb.jpg.e47e435389d7a1ac26dd0ffdc71718f9.jpg

 

In this photo you can see a different 10" woofer. My brother donated this Soundstream Trantula SST-10/2. I was unable to unearth the specifications for this driver online however, but threw it into the box to see how it measured.

 

Here are my results for the two different woofers:

  • Gold = Altronics (outside ground plane measurement approach)
  • Purple = Soundstream (also outside ground plane measurement approach), and 
  • Aqua = MLP (measured inside my listening room at main listening position) with 20hz high pass filter...

 

1420121067_GroundplaneandMLP.jpg.2689aa633e9dab88bdf43cbb25fbe509.jpg

 

The striking thing about these results for me was that:

  1. The two drivers matched each other so closely in the ground plane (2pi) measurements;
  2. That the 2pi measurements follow the Hornresp prediction very closely in that the inflection point at about 50hz and the similar response at 40hz; 
  3. The sharp 15db modelled dip at approximately 120hz is a a much smoother dip in reality; and
  4.  At main listening position, this sub gets me solid 20hz extension with no EQ! :hyper:

 

And just to really drive home how low this thing can go, and this is WITH a 20hz high pass engaged....

1389952106_THAM10HTLMLP.jpg.f0a2b5fd14ec88e635eab6d4f5075314.jpg

 

 

Granted its a bit lumpy inside due to room modes but that's easily tamable with some PEQ from my trusty old DCX2496!

 

So how does it sound? Like nothing I've built before. I'm up to probably +20 ported and passive radiator sub builds now. The best of which would be my pair of Alpine SWR 15's. Plus I really didn't expect much from this build, the box is not optimised for the drivers, heck the box is not even to spec because of the minimum 300mm cut rule!

 

So you can imagine how surprised I was to get so much output from this box, for $40 worth of ply and a few screws and PVA glue!

 

Playing the Danley Sound Labs "Train Start" track shook my room with all the authority I get with my Alpine 15's. However the most impressive part is the amount of "chest slam" the horn gives. Its not like a bass reflex where you get port wind at higher volumes. This is different. You instead get more perceived  "energy" from the horn, standing next to it your legs kind of resonate with the bass, less wind, more energy. Its hard to describe.

 

Punchy music with kick drums really kick. I was playing some music inside at a moderate level whilst i scooped my pool outside. I had the back sliding doors open to our patio area that looks over the pool. Standing at the back corner of our block I could feel the bass in my chest probably 25 meters away from the sub! Crazy! 

 

So whats the down side? Probably build complexity/time and size. The box for this 10" driver has as much volume as my Alpine 15's......

 

 

 

 

 

IMG_20190327_145412556.thumb.jpg.2696e4bcc243195264b1cb1e295656a8.jpg

 

Compared to my old Jaycar 12" subs in my man cave....

 

IMG_20190327_144216292.thumb.jpg.5b4cb2ac251b564689d32962550fa569.jpg

 

But not quite as large as the Snider Lab12 based tapped horn with an Alpine 12.

 

That's a stubby on the Alpine 15....

 

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Modelling the Alpine SWR/R-W 10" driver in this box will get down to 30hz before it turns downward. Now that would be something.

 

Here comparing Altronics PECC to Alpine R-W10D2.....

 

1669176332_THAM10HTLHornrespPECCvsR-W10D2Similulation.jpg.1209b415e613064d8d1d8680b22ba555.jpg

 

Here comparing the original B&C to an Alpine R-W....

 

1383353200_TPAM10HTLBCvsAlpine.jpg.3db81715916863ace36e2d3390e145c2.jpg

 

 

 

So if you haven't tried a tapped horn sub, I think you should!

 

Cheers.

 

 

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Edited by Maz4bz

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Excellent!

 

Quote
  1. The two drivers matched each other so closely in the ground plane (2pi) measurements;
  2. The sharp 15db modelled dip at approximately 120hz is a a much smoother dip in reality

 

 

1.   Remember that 3dB difference literally represents double the energy.  ;) 

 

2.   The simulator overestimates the peaks and dips due to its assumptions.    It might also be that the frequency resolution of your measurements is hiding some wiggles.

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