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PostPosted: 07 Mar 2021, 21:20 
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Location: Australia
This is for a country Victorian who initially asked me to build an amp for his Gales and ended with me building him a whole system;- tube preamp, 300/500W SS power amp, Xovers and two way speakers. He had the boxes made locally and supplied the the drivers I recommended (Locally sold 12” poly cones -95db efficient and an fs of 25hZ). Flat to 30hZ in my room.

The horns use FailtalPro compression drivers and he had the 511Bs powder coated. Looks good. The box is 170ltr. Xovers 3rd order on the horns and 2nd on the woofer. Xover point is 1100hz. Horns 109db dropped 14db to match woofers. Still a little on the forward side but enjoyable. Boxes to be painted by new owner.
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PostPosted: 08 Mar 2021, 14:34 
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Nice work @mwhouston ! 8-)

A few questions, just for my culture ;) :
1 - what's the reference and brand of the 12" woofer used here ?
2 - is it a Bass-Reflex of a Sealed enclosure ?

Thanks to let me know & Cheers, :)

-tbln.

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PostPosted: 08 Mar 2021, 17:11 
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tubelectron wrote:
Nice work @mwhouston ! 8-)

A few questions, just for my culture ;) :
1 - what's the reference and brand of the 12" woofer used here ?
2 - is it a Bass-Reflex of a Sealed enclosure ?

Thanks to let me know & Cheers, :)

-tbln.


https://www.altronics.com.au/p/c3070-30 ... e-speaker/

Box is sealed.

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PostPosted: 09 Mar 2021, 14:59 
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It seems to be a cool speaker - I'm afraid it may be unavailable in EU though !

I made a quick simulation here http://www.mh-audio.nl/Calculators/CBCV.html of a sealed enclosure, with the parameters given in the link you provided :

Resonant Frequency: 25Hz
QMS: 2.42
QES: 0.18
QTS: 0.17
VAS: 367L

So I took an estimated 100L sealed volume, minus 2L for the speaker volume, that is to say a Vnet=98L, and the simulator gives me these results :
Qtc=0.367 (over damping)
F3=127.8Hz
F6=76.1Hz

With a Vb=23L - 2L, hence Vnet=21L, we have :
Qtc=0.7 (critical damping)
F3=104Hz
F6=78.7Hz

With a QTS at 0.17, and an EBP at 139, this speaker would in theory be more suitable for a Bass-Reflex enclosure, I think...

What are the audible results in terms of bass with your solution : are they light but fast ? It would be quite logical, according to the numbers.

But again : this is the theory, right ? Reality can be different... ;)

-tbln.

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PostPosted: 09 Mar 2021, 16:37 
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Your calcs are right. Not good on paper. They sound better than that. No problems reproducing 30hZ in my room which sounds like a resonance. Drops like a stone after that. Sounds flat down to this point.

But the bass sounds very tight. The speakers were about a metre out from the wall so no wall support and brand new drivers. I would think with the speakers against the wall and 100hours from now the bass will be even better. Nothing wrong with it now. Speakers were picked up yesterday and won’t be setup for a few days. If I hear back I’ll update here on what he hears.

Boxes are about 160ltr.

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PostPosted: 10 Mar 2021, 08:14 
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mwhouston wrote:
Your calcs are right. Not good on paper. They sound better than that. No problems reproducing 30hZ in my room which sounds like a resonance. Drops like a stone after that. Sounds flat down to this point.

But the bass sounds very tight. The speakers were about a metre out from the wall so no wall support and brand new drivers. I would think with the speakers against the wall and 100hours from now the bass will be even better. Nothing wrong with it now. Speakers were picked up yesterday and won’t be setup for a few days. If I hear back I’ll update here on what he hears.

Boxes are about 160ltr.


I see - thanks @mwhouston :)

Sealed enclosures are underrated and surprinsing beasts... 30Hz extension is more than fine ! 8-)

My Heresy I (with corrected Xover and full stuffing) are helped by their placement (slanted ceiling forming some kind of large horn) and OTL amps, but their neat non-stuffed volume is circa 45L only, for a QTc that I suppose to be between 0.7 and 0.8 (to be measured !).

Image

So yes, with a wall-close placement, your 160L box - even if they cut earlier in F3, offer a smoother bass cut-off slope (circa 12dB/oct. against 24dB/oct. for a BR) and better damping (and so better transient response) - will be at their advantage, exploiting the supplementary baffling offered by the wall. ;)

-tbln.

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PostPosted: 10 Mar 2021, 16:11 
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tubelectron wrote:
mwhouston wrote:
Your calcs are right. Not good on paper. They sound better than that. No problems reproducing 30hZ in my room which sounds like a resonance. Drops like a stone after that. Sounds flat down to this point.

But the bass sounds very tight. The speakers were about a metre out from the wall so no wall support and brand new drivers. I would think with the speakers against the wall and 100hours from now the bass will be even better. Nothing wrong with it now. Speakers were picked up yesterday and won’t be setup for a few days. If I hear back I’ll update here on what he hears.

Boxes are about 160ltr.


I see - thanks @mwhouston :)

Sealed enclosures are underrated and surprinsing beasts... 30Hz extension is more than fine ! 8-)

My Heresy I (with corrected Xover and full stuffing) are helped by their placement (slanted ceiling forming some kind of large horn) and OTL amps, but their neat non-stuffed volume is circa 45L only, for a QTc that I suppose to be between 0.7 and 0.8 (to be measured !).

Image

So yes, with a wall-close placement, your 160L box - even if they cut earlier in F3, offer a smoother bass cut-off slope (circa 12dB/oct. against 24dB/oct. for a BR) and better damping (and so better transient response) - will be at their advantage, exploiting the supplementary baffling offered by the wall. ;)

-tbln.

Your heresys are not in the picture. Which model do you have not the IV?

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PostPosted: 11 Mar 2021, 05:06 
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Here they are :D :

Image

These are Heresy I HBR from 1983, on which I modified the E-2 crossover to smooth the Z curve and balance horns level vs. the woofer. I also stuffed them 100% with cotton wool to lower the QTc and eliminate internal resonances.

Original Z curve :
Image

Crossover modification (in red) :
Image

Modded X-over Z curve :
Image

Full stuffing with cotton wool :
Image

Image

-tbln.

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PostPosted: 11 Mar 2021, 07:01 
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Would never have picked it.

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