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Gestating large sensitive passive 15" augmenting subs


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On 24/05/2019 at 2:02 AM, Auracle said:

Flat (and/or parallel) panels will produce internal reflections that may present themselves to the back of the cone. Spheres don't exhibit this characteristic

Of course they do.

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Just a quick announcement that twins were painlessly born today, to a badly-presented but relieved BioBrian and his wonderful StereoNetter cohorts. I'd really like to gratuitously thank all staff, but

It's an odd experience when I find someone referring to something I wrote that I can't remember.   When you compare different kinds of subs, there are two experiences. The first is the easy

Both boxes now all trimmed, ready for final sand and varnish. Don't think I'll need DuraTex after all...   Worst problem has been lack of handles to move them.   110 kg each, so wi

 

22 hours ago, BioBrian said:

The example I mentioned about the Tchaik 6 recording, you twisted into another denigration of vented design

22 hours ago, BioBrian said:

(I hope) we all know speaker design is about choices between compromises.

I'm just trying to help you understand vented designs.... not "denigrate" them.

 

I don't think it is a good choice.

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22 hours ago, BioBrian said:

It shows that the vent is not creating resonance, but is preventing over-excursion

No.  That is not what your chart shows  (as everything, except a small bit of the vented box, is below 11mm)

 

If you are sure that you will never have signals below 10Hz, and you are sure that this chart represents you peak SPL, then the box is safe.

22 hours ago, BioBrian said:

which might appear to be a bit of a myth-buster

No.... and it isn't a "myth", it is just the simple physics of the matter.   The vented box will have excursion which continues to increase below the tuning frequency .... the sealed box, decrease.

22 hours ago, BioBrian said:

 

. The very large sealed enclosure (room) allows the same excursion down low as the dreaded vented box.

In your "extremely large sealed box" example..... Your chart would also show what I have just said, if you, extended the frequency lower.

 

Here it is ..... but to make it more fair to the vented box, I have EQed the sealed box the match the response of the vented box.

 

Coincidentally.... The SPL you have chosen, keeps the sealed box (when EQed to the same response as your vented box) exactly under the excursion limit at all frequencies.

 

 image.png.d3a1512aac61dbbd2d27f873197a6b82.png

 

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21 minutes ago, BioBrian said:

Maybe time to abort the project.

LOL .... I just think you can do a much better job of it.

 

 

You'll need EQ (like Paul said) .... and if you have that, then you don't need to have a vent.

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3 hours ago, Dirkgerman said:

Any ideas yet on what type of filtering ?

Passive, speaker level.

 

Hence the "need" for a vent, to get the required bass extension.    (The alternative would be a passive low pass filter operating at a very very low frequency... ie. impractical)

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19 hours ago, almikel said:

The large peak in the Group Delay for the ported box would also show as ringing in the time domain/transient response...can WinISD model transient response?

The group delay is just a function of the frequency/phase response.

 

If you EQ two boxes to the same response, they will have identical "group delay".

 

19 hours ago, almikel said:

so steep active filters can be worse than the 4th order HP filter of a ported box.

Yes, but remember is isn't the fitler.....  it's the resulting frequency/phase response, which determines the "group delay".

 

19 hours ago, almikel said:

Would you consider IB?

Will still need EQ to get suitable bass extension..... unless like you say, used a very specific IB driver ike the AE

19 hours ago, almikel said:

Flares at both ends of the port are mandatory

... and they need to get bigger as you move lower in Hz  ;) 

 

19 hours ago, almikel said:

measure speaker impedance, or driver Thiele-Small parameters

It will be ok to trust the SB datasheet here.

 

Small changes in the port tuning frequency from modelled to designed aren't going to be a big issue ...... mainly because it's v. likely to be a fairly large whack away anyway from what is needed in room once you consider room gain, and preference.     This is why people always bang on about EQ being essential for good bass  (amongst other things, so the LF knee/slope can be set in room).

 

Also the aerodynamics of the port will be a lot more significant issue than whether it ends up tuned to 19 or 23Hz.

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21 hours ago, almikel said:

Flares at both ends of the port are mandatory

Hi Mike

 

, I understand the logic behind this but JBL on their square vents and largest of the bass enclosures do not use flares. There MUST be a reason for this, thousands of tests over decades and hundreds of designs, by a professional Audio Corporation ?? This goes well beyond your opinion. We are talking about Speaker Systems people PAY MONEY to listen to, not domestic stuff.

 

Personally build in all practically more than a pair of enclosures for sub/bass purpose, professionally and otherwise per year,  many more in the hey day of car audio. 

 

https://www.jblpro.com/www/products/cinema-market/subwoofers#.XZAgR0YzY2w

 

 

An observation over time through building dozens of Professional PA and Personally owned enclosures is

 

1, the larger the box the better the whole thing will respond ultimately regardless of the driver

2, Round pipe is not seen as the best type of material for a port and has always been some sort of issue at the test phase or listening end of the project, particularly the end of the pipe within the enclosure, it's a PITA to flare and or make a flare for it unless it is Manufactured on mass. 

Large single vents on the same side of the enclosure as the driver always seem best, for whatever reason, possibly due to what was stated in my first second sentence of this post.

 

This information was formed over more than 3 decades of really building this stuff not sitting at a key board and using whatever means of calculating the enclosure, normally WIN ISD

 

I don't get the continual "afraidy cat" stance many are showing toward the ported enclosure, maybe it's the Maths ? They may have made duds in the past, dunno, (yea I have and not afraid to say so) but in the World at this point I can absolutely guarantee there are 10 to 1 factory designs using ported/vented enclosures for subs. Some are ok, some are not, but the Manufacturing FACTS are the same.

 

Why would this be ? I think @BioBrian has covered that rather well.

 

It's possibly an idea at this time to discuss how the response can be shaped to best advantage in a similar way @davewantsmoore is alluding to in a previous post

2 hours ago, davewantsmoore said:

(The alternative would be a passive low pass filter operating at a very very low frequency... ie. impractical

When was a 350 litre enclosure practical in any real sense of the word and or a very large or a few in series filter Inductor/s for a sub ?

 

Nothing practical, but practically has little or NOTHING to do wit this project.

 

Buying a fork lift however would be a practical thing to obtain.

 

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3 minutes ago, Dirkgerman said:

Buying a fork lift however would be a practical thing to obtain.

@BioBrian has this covered as well, he made special tools to move his present speakers(have wheels) and has a rather large tractor with bucket if needs be.

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11 minutes ago, soundbyte said:

@BioBrian has this covered as well, he made special tools to move his present speakers(have wheels) and has a rather large tractor with bucket if needs be.

Yes, I am starting to join the dots thanks Soundbyte\

 

Enclosures in excess of 100Kg are not the norm and hold a very special place in my heart as "The Best of ALL SPEAKER SYSTEMS" bar none. 

 

A rare thing indeed is a small speaker that sounds better than a large one. :) Do I have to run and hide now after making comments that are true ?

 

Size matters in this World of speakers, but the smalls will defend this to the death 

 

edit in a similar manner some will defend the use of a $1000 IEC cable, same gene pool 

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16 minutes ago, afa said:

Some "light" Sunday reading https://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf

cheers, Arthur

Done, I like the 9 points in, 13 General Conclusion, P 40/41

Thanks, interesting had not seen that before. 

 

Time to get the treddly out for a few dozen miles, Sunday ride 

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Every enclosure type is a compromise of some form, and ported ones have some of the best compromises. 

 

I have had lots of issues with trying to get bass out of open baffle or sealed woofers. They are probably much worse in terms of running woofers to their excursion limits than playing a ported system below its resonance frequency.

 

A lot of linkwitz designs suffer terribly from this, where he adds +20db EQ to a sealed bass setup and relies on listeners listening at low levels to make it work. The LXmini demos out there have its little woofer moving about like crazy and his Thor design (which i built) is the least impactful, most constrained subwoofer I have ever used

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42 minutes ago, oohms said:

 

I have had lots of issues with trying to get bass out of open baffle or sealed woofers.

 

 

I'm surprised to hear this, O - as I have zero problems getting deep bass from the sealed  subs that Paul Spencer designed for me.  Each has a 15" Dayton 'Ultimax' driver in a sealed box (internal volume ~7 cu ft), with an 800w Hypex plate amp driving it.  I happen to have an LP with a 16Hz organ test tone on it (32' pipe! :) ) - and I can clearly hear this tone.

 

Andy

 

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4 hours ago, afa said:

Some "light" Sunday reading

Thanks Arthur! I had a 'light' skim-though, and found it quite affirming.

 

And you others - I certainly wasn't expecting such a bunch of treats awaiting me after my afternoon nap. Should do it more often (if that were possible).

 

They were really pushing the boundaries by using quite small vents too; I didn't see mention of 150 mm vents, but I'll have a better read later.

 

Good to see flares are in fashion again, after starting in the '70s ?.

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3 hours ago, andyr said:

I happen to have an LP with a 16Hz organ test tone on it (32' pipe! :) ) - and I can clearly hear this tone.

That doesn't sound right. Why would they build 64' and 128' pipes, if they can't be heard?

 

Edit - sorry, it does appear correct, but maybe has something to do with closed or open pipes (one octave difference).

Impressed if your ears can hear 16 Hz though - I didn't know that was possible!

3 hours ago, andyr said:

I'm surprised to hear this, O - as I have zero problems getting deep bass from the sealed  subs that Paul Spencer designed for me.  Each has a 15" Dayton 'Ultimax' driver in a sealed box (internal volume ~7 cu ft), with an 800w Hypex plate amp driving it. 

I don't know how much of this thread you've read, but this is off topic. We are trying to use passive, analogue means to maximize low frequency output from specific drivers.

 

I do wish you continued joy from your system - maybe I'll take the same route one day, but I'm trying to squeeze as much out of this idea as possible.

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6 hours ago, davewantsmoore said:
Quote

It shows that the vent is not creating resonance, but is preventing over-excursion

No.  That is not what your chart shows  (as everything, except a small bit of the vented box, is below 11mm)

Dave I can't see what you mean here. The chart shows much less excursion from the vented system between 11 and 20 Hz, the bit that's dangerous because it might be contained in some music but can't be heard. The only way of knowing is alarming sounds, or visually seeing the cones moving a very long way (I've personally never seen this).

 

I appreciate that excursion may be higher below 11 Hz, but is it very common to find this on modern digital recordings of classical music?

 

Your version of WinISD seems to be different from mine. I have never come across this mammalian shape that you show for the sealed box excursion - in the charts I showed (you're still showing the wrong driver, but I don't thing that matters here) the excursion from the sealed driver box keeps going up, with lower frequency. Maybe you're using a little box size?

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@davewantsmoore

At one stage you said that these SB42FHCL75-6 drivers were not suited to a vented box design. Can you let us know why you said that?

 

I thought a Qts of 0.31 was within the normal boundaries for such a design.

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3 hours ago, afa said:

Some "light" Sunday reading https://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf

cheers, Arthur

what a great paper - thanks for posting

@BioBrian - definitely worth a detailed read.

 

3 hours ago, Dirkgerman said:

I understand the logic behind this but JBL on their square vents and largest of the bass enclosures do not use flares. There MUST be a reason for this

cost would play a part - a flare on a rectangular cross section port would be costly to manufacture.

Commercial designs where profit margins rule need to take compromises DIY designs don't - the paper attached by @afa talks a lot about flares - you've read it...do you still think ported designs are so good?

 

4 hours ago, Dirkgerman said:

I don't get the continual "afraidy cat" stance many are showing toward the ported enclosure, maybe it's the Maths ?

certainly not the maths

You've read the paper @afa posted - it discusses the complications ports bring - different port criteria between low volumes and max SPL as an example.

Calculating actual port length when including flares given the diameter changes is another...

...to get the best outcome from a ported design you need to prototype and tune mechanically...

 

I'm a lazy DIYer - I don't bother with ported designs when I can achieve good results with simple sealed designs and some EQ - which IMHO is needed anyway (EQ) to manage the room's bass response....

...and I liked Paul Spencer's T20 tapped horn design, so I built one - it works great (though tricky to design), but needs EQ, which I have,  so no issue.

 

4 hours ago, Dirkgerman said:

When was a 350 litre enclosure practical in any real sense of the word 

In the DIY world of subs a 350 litre enclosure is not unusual - and not outside what @BioBrian would consider...

...my T20 tapped horn is a bit less than that, but not much.

 

4 hours ago, Dirkgerman said:

and or a very large or a few in series filter Inductor/s for a sub ?

well that's what @BioBrian is planning - this is a passive sub after all.

 

4 hours ago, Dirkgerman said:

Enclosures in excess of 100Kg are not the norm and hold a very special place in my heart as "The Best of ALL SPEAKER SYSTEMS" bar none. 

Good box bracing is more important than mass - with subs, good bracing shifts the panel resonances above the operating frequency of the sub.

My T20 tapped horn box is light considering its size (2400x300x400) - 2 people can carry/move it easily

The enclosures I built for my 18" mid bass got bitcoted/gravelled - with drivers they're over 50kg each.

 

4 hours ago, Dirkgerman said:

A rare thing indeed is a small speaker that sounds better than a large one.

are you referring to driver size or enclosure size?

My AE TD18's are in very small sealed boxes - they sound fantastic.

 

My personal view is that you shouldn't run sealed enclosures smaller than a Qtc of 0.7 - but with EQ and power there's no real reason you couldn't run smaller enclosures

 

5 hours ago, Dirkgerman said:

Size matters in this World of speakers

18" midbass is truly a revelation - the drivers barely move and the bass slam is amazing - big drivers in a small box.

The T20 tapped horn below just adds weight - dual 12" divers in a big box.

 

cheers

Mike

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42 minutes ago, BioBrian said:

We are trying to use passive, analogue means to maximize low frequency output from specific drivers.

Hi Brian - what you mean is passive only - including analog would bring a Linkwitz Transform EQ into the picture :)

 

Something I would recommend, but not something you would allow.

 

Mike

 

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9 minutes ago, almikel said:

My T20 tapped horn box is light considering its size (2400x300x400) - 2 people can carry/move it easily

Have they shrunk? Your build post says "The ceiling height in my room is too shallow for it to stand up (it's 2400 x 600 x 400), so it will lie down along one wall with the mouth in a corner". That would equate to 576 litres? 300 x 400 would be a tight squeeze for 12" woofers?

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9 minutes ago, BioBrian said:

Have they shrunk? Your build post says "The ceiling height in my room is too shallow for it to stand up (it's 2400 x 600 x 400), so it will lie down along one wall with the mouth in a corner". That would equate to 576 litres? 300 x 400 would be a tight squeeze for 12" woofers?

Lol - brain fade - I went downstairs to measure it  - external 2400 x 600 x 400 - still an easy lift for 2 people.

17 minutes ago, BioBrian said:

That would equate to 576 litres?

bigger than I remember - a bit under that for internals etc etc

sounds good though

 

Mike 

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12 hours ago, Dirkgerman said:

Passive Filtering can perform rudimentary EQ if applied for that purpose ? particularly with subs

Passive filtering can provide cut only - and you need to build the passive filter for the purpose...change anything and you're winding new coils and buying expensive caps again.

 

...passive filters are really only feasible for making the low pass sub filter/high pass mains filter crossover  - not for EQing a room response.

 

12 hours ago, Dirkgerman said:

? particularly with subs 

subs are the particular area where a "passive filter only" solution brings additional challenges, because the room response is so dominant.

@BioBrian is up for that challenge - I'm sure the result will sound great.

 

cheers

Mike

Edited by almikel
typo
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6 hours ago, andyr said:

 

I'm surprised to hear this, O - as I have zero problems getting deep bass from the sealed  subs that Paul Spencer designed for me.  Each has a 15" Dayton 'Ultimax' driver in a sealed box (internal volume ~7 cu ft), with an 800w Hypex plate amp driving it.  I happen to have an LP with a 16Hz organ test tone on it (32' pipe! :) ) - and I can clearly hear this tone.

 

Andy

 

Some drivers (like my Aurasound NS18s) do perform well in sealed boxes, but in my experience, most don't. I can feel 16hz with that setup, and hear things rattle, but the harmonic distortion is low enough that i barely hear any of the tone itself

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2 hours ago, almikel said:

Passive filtering can provide cut only

I've read a number of times that it's not clever to boost dips with DSP EQ.  A better way is to use another sub or 2.

 

(Hey, that sounds like a fine idea).

 

It's just that HP, where passive speaker-level roll-off isn't practical. Hopefully that can be managed by repertoire manipulation.

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3 minutes ago, afa said:

program called "flare it"

Thanks again Arthur, I'll give it a go.

 

Actually from your big article I got the feeling I don't even need flaring with such a huge port, but seeing that the router can do it so easily, I'm sure I'll be fitting the same sized flares to the inside. The symmetry thing sounds very sensible for an oscillating column.

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31 minutes ago, Dirkgerman said:

Never been a problem really unless you are building for  130dB + PA performance and crowds in the hundreds.

 

If I'm reading this right, I disagree strenuously. A HPF for the mains is mandatory for the best integration between mains and subs, not just in PA systems, but it modest domestic ones as well. I've designed and built many of both types and set up many HTs and 2ch+sub(s) set ups.

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23 minutes ago, A9X said:

If I'm reading this right

Looks like a slight misunderstanding here. We were referring to HP filters on the subs themselves, with a view to avoiding over-excursion below ~20 Hz. These are just "filler" subs, and have no other drivers within metres.

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That's been the topic underlying the last few pages here.

 

Do you know of music content that's likely to threaten the drivers in my situation? Being a retired violinist, my tastes are mostly classical, and never painfully loud. I'm guessing that the graphs shown above are well above my listening threshold, therefore I'm looking at not using a HP filter for the subs.

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In my experience, it's not actual musical content that's the problem, but unexpected rubbish that can be at surprisingly high levels because they couldn't hear it in the studio when mastering.

I do all of my xovering in DSP, so adding a HPF below tune is very simple and provides peace of mind for $0 and a trivial effort.

For midbass boxes, ie PA 'subs' I've been using 6th order ported for nearly 20 years, so the HPF is included as standard. Played louder and cleaner than commercial equivalents in smaller boxes and I never damaged a driver in all that time.

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1 hour ago, oohms said:

I've never worried about it in domestic setups

me either.

 

Not an issue with music in general, however playing Basstronics tracks continually may occasionally be a problem ? below 20Hz 

 

If you watch movies with the sub volume maxed out there may be a need but otherwise, not really, installation specific. 

 

Certainly not "mandatory" 

2 hours ago, A9X said:

I disagree strenuously.

That's fine. But in all the years of building stuff, only used the ported box HPF (infrasonic protect) for PA applications and never damaged a driver, either. 

 

 

One could surmise that phono pre amps have this feature built in to a degree as part of the RIAA curve.

Some amplifiers have a sub sonic filter option.

 

15" passive augmentation is the thread title after all 

 

 

 

 

 

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8 minutes ago, Dirkgerman said:

Interesting beasty, they take quite a bit of work and can be a tricky thing to get right.

 

Not for me. Just follow Keele's maths and they worked perfectly every time. Used them domestically, in PA and for my last bass guitar rig.

 

The late 'djk' put me onto this in maybe 2001.

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19 hours ago, BioBrian said:

@davewantsmoore

At one stage you said that these SB42FHCL75-6 drivers were not suited to a vented box design. Can you let us know why you said that?

 

I thought a Qts of 0.31 was within the normal boundaries for such a design.

 

Precisely why is a complicated subject .... and speaker design is full of shortcuts and generalisations which are dangerous.

 

You may have encountered something referred to as "Efficiency Bandwidth Product".... it is "Fs/Qes", ie. Free air resonance frequency divided by the electrical Q of the driver at it's free air resonance.

 

People generalise that if EBP is > 50 then the driver is "good for vented" .... and if it is < 50 then it's good for sealed.... but this is a bad generalisation, due to the way it is worded ..... as it makes people think "I should use a vented enclosure".

 

WinISD uses the EBP (with the above rule) to suggest which type of enclosure to use.... and so it suggests vented, because EBP for this driver is 57.5.     However, realistically..... almost every single driver has an EBP > 50, usually by a lot.

 

A better way to generalise about EBP (although most generalisations are silly) .... is that EBP >> 100 means the driver is strange and was designed specifically for a vented box or a horn .... and EBP around 100 is quite normal, and most enclosures will work depending on your application  .... and as EBP gets lower eg. << 80 .... then the driver was likely designed for a sealed enclosure.

 

EBP = 57.5   (Fs = 18.4Hz / Qes = 0.32) 

 

 

 

To escape the rule of thumb, you have to look at the driver parameters meaning... and this driver is not the easiest, as it's unusual.

 

You have:

 

High motor force and relatively low moving mass.   This might suggest a high resonant frequency.

 

... but you have a very low free air resonant frequency.   This is because of the very high compliance (soft suspension) and low Q electrical breaking (spread over a wide range of Hz).    Essentially a "floppy" driver.

 

You can see that in the VAS (litres) parameters of the driver.  If you take away the mechanical and electrical restoring forces of the driver.... how much air do you need to provide that same restoring force.   The VAS is very big.   This means you need a large volume of air to match the force.... meaning a low amount of force.

 

 

How a driver works....

 

Above the resonant frequency of the system .... the amplifier is in control, the driver moves where the motor force tells it to.... and it's simply force against a moving mass.

 

AT, the resonant frequency ..... everything is in equilibrium.   This is where the Qs of the electrical and mechanical forces (Qes and Qms) are specified.

 

Below, the resonant frequency.... the amplifier has no control.   The motion of the cone is determined by the compliance (stiffness) of the mechanical system.    In a sealed box the volume of air in the box (part of the mechanical system), conspires to control the movement - and so we get reducing cone excursion as the frequency goes down.    A vented box contributes less, and so the cone excursion continues to rise as the frequency goes down.

 

So what you will have at low frequency.   A big box, with a big as possible port....  low stiffness, and low loss driver.....  ie. as little as possible preventing the driver from experiencing uncontrolled movement.

 

 

Is this just all just me being waaaay too "grumpy cat".   In general, no.... In practise, unsure.

 

Very small changes in tuning, and peak SPL, will produce big changes in excursion.    The difference between tuning to 25Hz and only making 100dB peak (which isn't very loud for a sub) ... and the difference between 18Hz and 105dB peak SPL, is the difference between fairly linear behaviour, and the potential for hurting your driver.    Between those two lies bad performance.

 

You mentioned that you "don't see" the cones moving too much..... and unless there is very very LF in the absence of other LF (which is unusual sans warped LPs and recording with traffic or similar) then you won't necessarily see it.    That's because the wobbling is super-imposed over the normal (amplifier controlled) movement.    But you can measure it as higher non-linear distortion (THD and IMD, etc.) .... and you can hear it in a "less dynamic range" kinda way   (a bit more muddy and constrained).

 

 

The other concern, is that WinISD does not model the ultra-low frequencies accurately.   So the charts which low the increasing driver excursion leveling off around 5Hz or so, are surely wrong.    It doesn't model your port properly either (it's making wildly optimistic assumptions about aerodynamics and turbulence).

 

If you build it ... and then measure the electrical impedance of the box at various SPLs (very low to very high) you will see the tuning changing.   The bad new there is as the port dynamically compresses (turbulence) it momentarily moves towards a closed box.... which means the bass goes away.   :-S

 

 

So why all this naysaying, and does this mean that vented boxes are just all-bad?   No.... but what it means is that you should use low SPLs (but I don't believe your peak SPL at 20Hz will be ~100dB) ... or use a high pass filter  (but a passive speaker-level HPF is impractical).

 

It means you should build a super aerodynamic port, and probably tune a little higher than you are.    It means that the LF knee of your response is quite high Q  (it has a peak and then a sharp drop) .... and this is almost certainly not what you'll need to match for your in-room response.    That's OK (it doesn't mean "don't vent") ... but it just means you'll need EQ to set the response to what you want/need.

 

As people said.... all the boxes will sound the same (assuming they avoid major flaws - which I don't think your vented box will) if they're set to the same response.    That's where your EQ is needed.

 

Also the EQ will help you solve.... room modes and the low pass filter (integrating the woofer with the next driver up).   All of these things are important.     There's just no getting around designing the right high pass (mechanical) and low pass (electrical) filter if you want a good result ..... and the choice of a vent, and a passive-speaker-level filter .... are both impractical.

 

 
Edited by davewantsmoore
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5 hours ago, BioBrian said:

Do you know of music content that's likely to threaten the drivers in my situation

No not really although you said you listen to Basstronics, regularly earlier in the thread. 

Violin Classical, well ,,,,,, un likely unless there are foot falls and other stuff on the recording in sub sonics that were missed during productions like this 

 

THis Basstronics track you will hear the effects of an uncontrolled driver diaphram, in a ported enclosure. 

 

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    • By Stereolove
      Item Condition: Excellent working condition Shipping Options: Pickup available and you can audition. Suburb or Town: Essendon State: VIC Payment Method: PayPal / Cash Reason for selling: No longer required. Upgraded subwoofer. Further information: The Bose Acoustimass 10 Series IV home entertainment subwoofer brings great sound to your movies and music. Connect it to your home theatre receiver and enjoy Bose quality sound.
       
      Unit is in excellent working condition - very few cosmetic marks, all control knobs operational, and comes with original power cable. No manual or original packaging comes with this unit. 
       
      Compatible with A/V receivers and amplifiers rated from 10 to 200 watts per channel, rated from 4 to 8 ohms.

      Photos:
       
      PLEASE READ
      If you include any reference to pricing whatsoever in this section (excluding RRP), your ad will not be approved If you are advertising multiple items, you must post one bulk price only, or post seperate ads for each item If you don't include photographs of the actual item being sold, your ad will not be approved You understand that a reasonable donation for selling fees is expected upon successful sale of your item
      - if you have previously sold items and not made a donation, your advertisement may not be approved.




    • By umami
      Hey guys,
       
      Got handed down a sick sound system from a relative that's downsizing, and he said he's not sure whether or not the subwoofer actually works. He's not a massive hifi/electrical guy so it's up to me to diagnose it. For now I just need help knowing what the correct way to connect it is, so I can know whether it actually works under normal conditions, and if not then I'll open it up and get the multimeter out. 
       
      Receiving this system is what spurred me on the join this site because I really want to optimise it and learn how to use it well, because I don't have any hardcore hifi experience, just tinkering with cheap junk over the years.
       
      So far I've just tried connecting the amp's subwoofer port directly to the "low level input" with a 1 to 2 RCA cable, and didn't get anything. Fuse is intact.
       
      So:
      Looking at the photos of the inputs, are this sub and amplifier actually compatible, and if so, what's the best way to connect them?
       
      Should I care about the speaker out part on the sub or just throw the speakers directly onto the amplifier?
       
      Also, can someone give me a rundown on the gain/Freq knobs as well as the on/auto/off and phase switches? Like, I know what gain is from playing my guitar, and I understand that the frequency knob will be probably focusing the sub on a particular frequency to thump out or isolate, but I don't know what kind of range I want to keep it on for it to be good. Absolutely no clue what the phase bit is for.
       
      Cheers, and happy listening


    • By PaddyMcD
      Item Condition: Used Shipping Options: Pickup available and you can audition.,Shipping is available at agreed cost. Suburb or Town: Sydney State: NSW Payment Method: Cash, Paypal Reason for selling: Change Subwoofer has a ding on the left corner (pictured) from removal company. Doesnt effect performance. Mediabridge ULTRA Series Subwoofer Cable (2M) included. 
       
      Further information:
       
       Polk Audio Powered Subwoofer PSW303

      * video-shielded

      * slot-loaded enclosure

      * 100-watt RMS amp

      * 8" front-firing, long-excursion driver

      * frequency response 35-160 Hz (-3dB)

      * continuously variable 60-160 Hz crossover

      * unfiltered LFE input for 5.1 bass

      * line-level and speaker-level inputs

      * speaker-level output

      * volume control

      * phase switch

      * auto on/off

      * real wood veneer

      * 11-7/16"W x 12-3/8"H x 17-7/8"D

      * warranty: 5 years woofer, 3 years amplifier
       




    • By Shane Stephenson
      Item Condition: Near mint condition. Shipping Options: Pickup available and you can audition. Suburb or Town: Herne Hill Geelong State: VIC Payment Method: Cash Reason for selling: Too big and powerful for my room. Hi all up for sale is my SVS ultra 16 PB subwoofer. This unit is in mint condition with very little used would suit somebody wanting to buy new. It is 6 months old and has 4 1/2 years warranty remaining.
      This thing is ridiculous as all the reviews show. You need to make sure everything's tied down around your house because stuff will start falling off the shelves. Sealed up it produces amazing chest-thumping bass for 2 channel Hi-Fi listening.  And with the plugs released gets down comfortably into the mid teens shaking the dust off your ceiling fans. It literally makes your house resonate. Must be heard to be believed. It's just too much for my house and my listening room. But at the time I purchased this my eyes were bigger than my stomach. Grab yourself an end game sub for a very reasonable price. It's black Ash and I have the brand new remote control still in the Ziplock bag. There are no marks or damage on the subwoofer anywhere l have the inner box but not be outer cardboard.
       
      Photos:
       
      PLEASE READ
      If you include any reference to pricing whatsoever in this section (excluding RRP), your ad will not be approved If you are advertising multiple items, you must post one bulk price only, or post seperate ads for each item If you don't include photographs of the actual item being sold, your ad will not be approved You understand that a reasonable donation for selling fees is expected upon successful sale of your item
      - if you have previously sold items and not made a donation, your advertisement may not be approved.





    • By Michael Lee
      Item Condition: Good used Shipping Options: Pickup available and you can audition. Suburb or Town: 2570 State: NSW Payment Method: EFT Reason for selling: Redundant A good surround sound speaker starter package. The sub has recently been serviced. Further information:
       
      Photos:
       
      PLEASE READ
      If you include any reference to pricing whatsoever in this section (excluding RRP), your ad will not be approved If you are advertising multiple items, you must post one bulk price only, or post seperate ads for each item If you don't include photographs of the actual item being sold, your ad will not be approved You understand that a reasonable donation for selling fees is expected upon successful sale of your item
      - if you have previously sold items and not made a donation, your advertisement may not be approved.





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