Digging deep, 4th order bandpass subwoofer build

[Welder]

If I can tear myself away from the tuneful bass I get here I may well do that one day Mark. I would like to meet you anyway.

You never know mate, I may just come equipped with a server so you can chuck your cd player out with the speakers

[Reid Malenfant]

All the best John, have a good weekend m8

Weekend? I must be enjoying myself

[Welder]

And you Mark

Cans time here methinks

[SPS]

i'm sort of with welder with my feelings about the quality.. but i cant help but admire your balls in attempting this project this Mark.
i also think heat is the least of your troubles

in my experence with hi fi its about understanding what gives



your clearly far more technical in your approach .. and I hope you succeed, so the best of luck to you

but when you have those very low notes you will have little to compare it too with regard to accuracy,

i was in precision devices's factory test room a few years ago, they have a wall of pa speakers and lots of good gear powering it up and the ability to cut/boost most frequencies , i was looking at their 22" drivers for an open baffle project, but got to hear only 15 & 18 units. He played me music that sounded like a concert.. but when he cut the (around) 70 hts upwards sounds, what an awfull sound came out of the speakers, sound full of distortions, in my view due to the amplification and port outputs, and the slowing of the cones movements due to the loading imposed from box speakers.

the design engineer sort of said whats the point.. look whats there?
but the whole picture sounded very impressive
and he was right to a point, if most people hear a little thunder through a system they are very impressed.

now, 2 years on.. in my system there's nearly the same drivers, with clean amplification and those low notes that have the sound like any real instruments that produce low notes. its very clean..

best of luck...

[Reid Malenfant]

Cheers for the luck Steve, it's nice to have it

Ok, so i'm not attaching accelerometers to the bass drivers & forcing them to follow the input waveform precisely a la motional feedback. So yes in that respect these & just about everything else isn't perfect. The drivers are very high quality units though, with a motor circuit designed to cut distortion in comparison with a standard motor unit by 75% up to about 75% of maximum linear excursion.

In that respect they should have lower distortion than something like the Precision Devices drivers, though i know these to be rather good with low thermal compression. They still don't have the XBL2 motor though

The passive radiators are the only pain in the backside though. I don't mean what they'll do, but building the things If you have read back from a page or two you'll know i couldn't port these things as the port would be either too small (causing turbulence & distortion) or too long in which case the first port resonance frequency would be in the passband

As it is i have sussed out a neat way of getting the passive radiators mechanical properties out of the window by giving them a huge VAS which will be totally swamped by the 300L of enclosure. Thus it'll only be the enclosure air volume that'll be in control of the PR which has the same effect as using a huge reflex port but with none of the problems associated with it..

It'll be interesting for sure, though as i have already pointed out (i think) i'll never hear them at full volume as i just won't be able to stand it. At lower volume distortion will be minimal

[SPS]

. So yes in that respect these & just about everything else isn't perfect.

to be frank thats my experence too,
most speakers can leave a lot to be desired, but most don't realise that

and there's just so many variables and viewpoints.... all valid enough,
the trouble is you cant imagine the improvements you can get in the sound quality when you give the driver less work to do, but as you know you need good drivers with just enough self damping for the job... and it sounds like that is what you have,

i've had a couple of pairs of ns1000's, as you know they dont have that ported sound, but the speakers sound is limited by the driver compressing the air in the box,
remove that aspect and speakers can spring into life,

i would make up a baffle board to compare

say a cheap W section board on hinges at the 3 joints, cut /mount the speakers on the two middle panels, well tape the joints so the dont leak
mount the speakers close to the floor on the boards & site next to a wall if you can, nothing too big... each board the width of the driver and say 30" high

they wont go as loud in the bass as you would like..but you can eq it a bit
without spoiling the sound too much,
but you will have a reference to what the driver will sound like on its own ( without a box or load)
and work from there..

hope you dont mind me interfering.. i too have been building speakers for a few years, but ended up in a totally different route, in the search of what i think is a realistic sound.

[Reid Malenfant]

hope you dont mind me interfering.. i too have been building speakers for a few years, but ended up in a totally different route, in the search of what i think is a realistic sound.

Steve, you aren't interfering in the least

To be perfectly honest i will say that i have never heard any open baffle speakers. Well that's not strictly true as i sure as hell heard the Pro Plus drivers breaking in

I'll be 100% honest & say that i was planning on going down the closed box route, rather than a reflex. The only reason i decided on the reflex is because i managed to get the box tuning so low (about 10Hz now ). Because of that they should sound like a sealed box from 20Hz upwards as the port or in this case the ABRs PRs or whatever we shall call them will only operate up to approximately double the tuning frequency. For all intents & purposes that is now (supposedly) below audibility.

I still have 6 of the 15" Pro Plus drivers which are actually better suited to OBs due to the driver Q being higher. Maybe some day i'll experiment with some kind of OB & see what i get. Only a herd of charging rhinos will deflect me from building these as i designed them now as i have purchased the bits & pieces to build the ABRs

You can't say you didn't try though ATB!

[SPS]

it did look like i was trying to convert you to OB's mark.. that was not really what i had in mind, i was just thinking you could knock quick a test baffle up to compare to the speaker cabs you where planning,
you would easily be able to compare the sounds you where getting... and i just thought that may help...

but your minds set i can see...

cheers
steve