Acoustic Elegance TD18+4, vented box or sealed ?

[A9X]

5 hours ago, jasonphilip said:

The PSE144 is a cool speaker system from my experience (possibly slightly underrated really) that is vaguely similar to the Danley and probably your Lambda Unity.

They all work on exactly the same principle, which you'd know if you understood how they worked.

5 hours ago, jasonphilip said:

and it pays to read entirely the posts made before commenting.

It's usually Sunday before the sermons start.

5 hours ago, jasonphilip said:

I am almost certain you possibly have some experience with larger drivers and more efficient speaker systems

I do. I haven't has a set of mains, or even surrounds, lower than about 96dB in more than 20 years. When the new midbass horns are complete, I'll be back up to 102dB or so.

 

As for larger drivers, I consider 15's the sweet spot for midbass though in recent years I've built with 10's, 12's, 15's, 18's and 21's.. The (4) surrounds have 15Xs as midbasses, and the mains 2x15S each. All are sealed and EQd to give the desired response.

5 hours ago, jasonphilip said:

and your time spent better giving an educated opinion of

This amused me as you are asking for my help, yet you tell me how I should spend my time. Those who know me in person from here could perhaps tell you how I'd respond to that in person.

5 hours ago, jasonphilip said:

sealed or tuned helmholtz resonator enclosure for the AE TD 18+4 

It's an odd duck driver with it's very low Qt, so I've never really liked it, even though I own 12 AE drivers that I like a lot. The low Qt will typically give an EBS type response similar to the green curve in this pic, so I'd seal them and EQ them with a DSP.

[jasonphilip]

1 hour ago, A9X said:

This amused me

Glad I amused someone today and thanks for your reply. Understand everything except for 

 

1 hour ago, A9X said:

low Qt will typically give an EBS type response similar to the green curve

this. Yes the driver has the low Qtot and relatively high Fs, which could be viewed that the driver doesn't do low bass, it's  a midbass driver. The green curve appears to give a more coherent response without the little sealed box and DSP in the sim.  Idea is to use the speaker in a domestic environment on a small amp[lifier using  as a HF section, all passive ? way.  I dunno, just going to do the black sheep thing and build a ported <:)

  

[Buffle]

I'd pay head to the advice from DWM and A9X.  This driver is particularly unsuited to use in ported enclosures.  It is, however, very well suited to sealed enclosures and EQ due to its Qes and Qts.  Out of the AE drivers I'm familiar with, this would be about my last choice for use in a ported alignment.

[BioBrian]

From their website: 

 

Suggested Enclosures:
4-8cf vented for bass applications
2-3cf vented for midbass
6-12cf vented extended bass
3-10cf sealed
automotive infinite baffle

 

Says it all?

[A9X]

1 hour ago, BioBrian said:

Says it all?

Nope, just some serving suggestions. There are plenty of other ways to skin the cat.

 

Take for example my favourite 15's before the AEs, the JBL2225/2226. JBL suggests a ported cab of 140L tuned to 40Hz, a pretty standard QB4 qlignment. However, put them in 40L, tune to 40Hz, and add a Q=2 40Hz HPF and you end up with a 6th order ported (NOT bandpass) alignment that gives a smaller enclosure, lower distortion, the HPF naturally protects against over excursion below tune, and you get the same basic FR and output from 40Hz up. I built a number of these and have used them to excellent effect at home, and also in a PA where I beat the snot out of them for several years with no damage/failures. The only disadvantage is that you require EQ, which must be electronic (line level). Some of the AE 15's also do well in similar enclosures, but not the 18 because the  Qt is too low; it would likely make an excellent midbass horn driver.

 

The late Dennis Kleitsch put me on to the idea about 2000 of so. I was skeptical until he pointed out that Don Keele developed the math.

Edited May 9, 2019 by A9X
Added a sentence to clarify, Clarise.

[davewantsmoore]

11 hours ago, jasonphilip said:

doesn't do low bass

You can also view this as - the driver has a strong motor force.

 

 

This chart is telling.   Grey=Vented

 

 

 

11 hours ago, jasonphilip said:

The green curve appears to give a more coherent response

I don't know what that means.

 

... but have a look on the Group Delay chart.

 

11 hours ago, jasonphilip said:

small amp[lifier using  as a HF section, all passive ? way.  I dunno, just going to do the black sheep thing and build a ported

 

I made a chart with 200L boxes + 30Hz vent, with the output set to 105dB.

 

This might seem louder than you want, but the range below 50Hz needs to be capable of these SPL to sound "realistic", and if it is much lower than this, bass won't even be audible (as the threshold of audibility rises dramatically at LF due to fletcher munson, and masking).

 

Then I set the LF -6dB point for the sealed box to be as low as possible (until the driver runs out of xmax @ 105dB). 

 

Alternatively - If you reduce the peak SPL (currently 105dB), then you can lower the LF rolloff of the sealed box further (less max output, more bass).

 

Or....  Everywhere you read "more bass" for the sealed box - you can trade that extra bass in for "less power" and "less driver excursion".    Although there's no point doing that (within reason) for this driver - it is designed to handle massive power and excursion  (otherwise you should just buy a driver priced << 50%).

 

 

To get this SPL curve from the vented box, I added a 1st order low pass filter at about 70Hz.

 

If you did this in practise, that's a massive inductor in series with the woofer.    But, I highly doubt this will be effective in practise anyways, due to the very non-flat impedance of the driver in box (impedance peak right at 50Hz).    The thing which makes this driver cost $1k (among others) is the low inductance   

 

 

The next issue is the rolloff where it will cross over to the horn.     The sealed box is flat through this region - what you see in the chart above is what you get when a fourth order linkwitz riley low pass filter is added.   (24dB/octave) at 300Hz  (-6dB=300Hz). 

 

Why that filter?   The high pass response of your horn is going to be ~24dB/octave ... and so the TD18H needs to roll off at 24dB/octave to blend successfully with the horn through the crossover.

 

How are you going to get that slope with a passive filter.    The grey line is already at ~6dB/octave, with a -6dB@300Hz.    You're going to want to keep the -6dB point roughly at 300Hz (to meet the horn) ..... can't really do that with a "passive" filter.     You could add a 18dB/octave (3rd order) fiter .... but it'd need to be down at @200Hz to get the overall shape right.

 

Hard to know without knowing the precise shape of the horn high pass.... but the point is, that no matter what - the vented box makes it difficult here.

 

 

 

For the LF end.   You can see the vented box is about -10dB @ 20Hz and -30dB @ 10Hz ..... that's not loud enough in relation to the octaves above (eg. 40Hz, 80Hz, etc.) for the bass to sound natural.

 

 

The power is an issue.

 

For the yellow/sealed box i peaks at ~180w / 4ohm ... but this is still only ~10% of the drivers rated power.

 

Setting the vented box to output 105dB, puts it over your 10w power goal.    If you dial the power back to 10w, you get 104dB, close enough.

 

 

Cone excursion is OK.  The driver is still quite linear at xmax ....   but notably here excursion is very low, ~1/3 xmax until < 40Hz 

 

 

The real issue here though is the designing a high performance vented box for the driver is much more difficult than the comically simple simulators  we are using suggest.   The strong motor of this driver make the job in some ways easier (it's less susceptible to the effects of the vent) but also harder because the driver rolls off quickly below Fc.

 

In lots of ways the comparison would be fairer vented+EQ vs sealed+EQ.     Then many of the issues I mentioned go away - and in a simple simulator like this, the vented box would look good (less power less excursion) .... but this ignores the realities of the vent design itself - which unless they are big and curves (aerodynamic) work less well under dynamic conditions than the sim shows.    You can get a glimse of it in the group delay chart - but again, it's an over simplification.

 

 

 

 

If you're the sort of person who can figure out what you have so far..... then you can setup some EQ built into an amplifier.

 

https://www.diyclassd.com/product/fusionamp-fa251/155

 

If you don't want to split signals at your source .....  this amplifier, can take input via speaker leads running from your existing 10w amplifier (like many subwoofers can).

 

Don't be fooled by the ~$400 per channel price (assuming you think it is cheap) ....  it would likely outperform your existing amp   

 

Not to mention the biggest benefit of doing this, which we haven't even touched on.     It will give you the ability to apply EQ to the in room response below 300Hz.    Bit of a suck out at 100Hz?    Bit boomy at 40Hz?   Fix it.

 

 

PS - the comparisons above, assume a "10w amplifier".    If the amp is "10w peak @ 4ohm" ie. clipping .... then you'll need to reduce the above numbers.     The recommended amp above is "250w@4ohm", so 180w is clean.

[davewantsmoore]

1 hour ago, BioBrian said:

Says it all?

They're not all created equal.    There's lots of pros and cons to those options.... talking through what they are, and how they apply to a situation, is what's needed.

 

AE have a lot of pro audio customers.    Those customers need boxes which maximise the SPL ...  there a vented often more appropriate.

 

For example.... When we are trying to fill the Sydney Cricket Ground.....  the type of difference shown below  ....  a vented box which follows their 12 cu.f (I tuned to ~20)     .... You can get 10dB (!!!) more out of the box  (although as mentioned before, they'll still use lots of EQ to bend the response to what they want)

 

 

 

.... or if you move up to 50Hz (ie. bass, rather than extended bass) .... You can get 15dB+ more max output, and hit 130dB.

 

Edited May 9, 2019 by davewantsmoore

[davewantsmoore]

1 hour ago, A9X said:

Take for example my favourite 15's before the AEs, the JBL2225/2226. JBL suggests a ported cab of 140L tuned to 40Hz, a pretty standard QB4 qlignment. However, put them in 40L, tune to 40Hz, and add a Q=2 40Hz HPF and you end up with a 6th order ported (NOT bandpass) alignment that gives a smaller enclosure, lower distortion, the HPF naturally protects against over excursion below tune, and you get the same basic FR and output from 40Hz up. I built a number of these and have used them to excellent effect at home, and also in a PA where I beat the snot out of them for several years with no damage/failures. The only disadvantage is that you require EQ, which must be electronic (line level).

It doesn't even need to be line-level (right?!) .... If you want to put the peaked-HPF in between the amp and driver, you can.

 

The TD18H wants about 75L (instead of 40L).   So this chart is 75L tuned to 40Hz, vs sealed 200L .... The SPL is set to "~6th order" (36dB/octave) with -6dB point at 40Hz.

 

I've raised the output to 115dB from the previous example  (cos it's still a walk in the park if we're giving up the bottom octave).

 

 

 

 

 

It's a good way to ensure the cone excursion stays low  (although for this driver the difference between 2 and 5mm isn't relevant) .....  and doing so let's you put the full 2000w of rated power into the driver .... although it doesn't let the TD18H be a "subwoofer".

 

BUT .... The small vented box doesn't keep the power low relative to a larger sealed box.    The vented box needs 3x the power in this example.

 

Quote

Some of the AE 15's also do well in similar enclosures, but not the 18 because the  Qt is too low

Looks ok in that sort of box. 

 

If your goal is to get the cops from the next suburb (or maybe 2 suburbs away) over to visit .... then more than OK. 

Edited May 9, 2019 by davewantsmoore

[A9X]

4 minutes ago, davewantsmoore said:

If you want to put the peaked-HPF in between the amp and driver, you can.

How exactly are you generating a peaking filter passively to compensate for the low Q ported enclosure design?

[davewantsmoore]

1 hour ago, A9X said:

How exactly are you generating a peaking filter passively to compensate for the low Q ported enclosure design?

The circuit is a resonator, and you can design a higher Q.     "Butterworth" etc. are just examples of the resonator where the pass band is "maximally flat".

 

 

It's also possible I have spent waaaay too long exclusively using active filters....

Edited May 9, 2019 by davewantsmoore

[davewantsmoore]

24 minutes ago, davewantsmoore said:

The circuit is a resonator, and you can design a higher Q.     "Butterworth" etc. are just examples of the resonator where the pass band is "maximally flat".

 

 

It's also possible I have spent waaaay too long exclusively using active filters....

Nope... It's fine.

 

Just jumped into the passive XO simulator.... and made this from the parts bin.    That's a real woofer it's connected to (a Seas Excel midwoofer)

 

 

 

 

 

 

[jasonphilip]

Reply's received wow, let's flesh this job right out !, will take me an hour or so digesting/reading all of them carefully before reply as you Blokes know a bit

Edited May 9, 2019 by jasonphilip
apostrophe missing

[fishball79]

On 09/05/2019 at 8:42 AM, A9X said:

Some of the AE 15's also do well in similar enclosures, but not the 18 because the  Qt is too low; it would likely make an excellent midbass horn driver.

Hiya, im sitting on a pile of AE woofers (TD15M, TD15X, SBP15, SBP12, TD10S), just joined the forum. Lo & behold i found something very interesting to me.  I have NOT manage to get any good decent punchy bass from them so far in my probably wrong sized cabinets.

 

With the 2226 having an official Qts of 0.31, i'm assuming any AE driver within 10% of that suitable.
Where can I find the maths or calculator to find out the suitable size and tunings for my AE drivers?

[soundbyte]

Nice to hear of another AE user.

 

WinISD is used by a number of members here for calculations for boxes and can be downloaded at http://www.linearteam.org/ install (hopefully you have a Windows machine) and run.

 

Basically insert the relevant driver details, then see what result/s you get.

 

Not that easy but with a bit of time, you should get results that are suitable for your drivers.

[BioBrian]

nnn

Edited May 16, 2019 by BioBrian
clumsy OT rave on my obsession

[davewantsmoore]

22 hours ago, fishball79 said:

I have NOT manage to get any good decent punchy bass from them so far in my probably wrong sized cabinets.

They will all make "no bass" when put in a box .... as they all have very powerful motors.

 

You will need to "EQ" the response so the bass is lifted, and the response is flat down to LF.     You can "EQ" by adding a vent/port, or using EQ, or a horn, or....

20 hours ago, soundbyte said:

hopefully you have a Windows machine

It also runs through the windows app emulator "WINE".

 

Quote

Where can I find the maths or calculator to find out the suitable size and tunings for my AE drivers?

If you are trying to make a vented box or horn, then the box/vent will be quite important ..... if it's a sealed box, then it will need EQ regardless of size.   The size of the box will affect the power handling and cone excursion.

[davewantsmoore]

For example all of the woofers will rolloff somewhere below 100Hz when they're in a realistically sized sealed box.

 

I run the TD15M, with EQ setting it to a 24dB/octave high pass response @ 60Hz .... and my subwoofers overlap it

[fishball79]

1 hour ago, davewantsmoore said:

You will need to "EQ" the response so the bass is lifted, and the response is flat down to LF.     You can "EQ" by adding a vent/port, or using EQ, or a horn, or....

I have tried various amounts of eq from 0.1 to 6db in the in various bands between 40-120hz but no joy.  The bass weren't chest thumping still.

[Guest Peter the Greek]

3 hours ago, fishball79 said:

 The bass weren't chest thumping still.

Probably a room or placement issue?

[A9X]

On 15/05/2019 at 4:21 PM, fishball79 said:

Where can I find the maths or calculator to find out the suitable size and tunings for my AE drivers?

Unibox or WinISD.

[davewantsmoore]

19 hours ago, fishball79 said:

I have tried various amounts of eq from 0.1 to 6db in the in various bands between 40-120hz but no joy.  The bass weren't chest thumping still.

If it was in a sealed box, then you'd need more EQ than that.

[fishball79]

6 hours ago, davewantsmoore said:

If it was in a sealed box, then you'd need more EQ than that.

Forgot to mention i got a Trinnov DSP FIR used for crossover & EQ so the response i get at the seated position is exactly as per what i set for the EQ.

The system is in a concrete apartment open plan living room which the EQ would've resolved any high bass peaks that might overpower the mid bass that is present.

 

I do get deep articulate bass but what I am not getting is the chest thumping kind.  Is what I want some kind of colouration?

[A9X]

1 minute ago, fishball79 said:

I do get deep articulate bass but what I am not getting is the chest thumping kind.

Chest thump is a lower midbass thing, from maybe 80-150Hz, depending upon the size of your chest cavity.

 

I also don't trust auto EQs.

[fishball79]

1 hour ago, A9X said:

I also don't trust auto EQs.

Don't matter, without the auto eq in place. manual eq to boost 80-150hz didnt improve the the midbass punch.

Next step is to move the system into a closed room as some have adviced if the air volume isnt fixed, its hard to couple.

 

That said, we get plenty of punch in open area concerts so im not sure if thats the solution.

[A9X]

1 hour ago, fishball79 said:

manual eq to boost 80-150hz didnt improve the the midbass punch.

As you've not provided any measurements, it's hard to know at vast distance what's going on. Maybe you're sitting in some midbass room nodes.

1 hour ago, fishball79 said:

Next step is to move the system into a closed room as some have adviced if the air volume isnt fixed, its hard to couple.

In my experience, that's utter bollocks. My mains and surrounds both use AE TD15 drivers for midbass, S and X respectively, and they are in a room with 2 large archways at one end, and I have no problem with midbass punch. Nor did I in my house up north where the open plan living area is larger than my entire apartment currently . I also ran a PA system for many years that I designed and built and it would provide good punch in room of 600 people or so; that used JBL 18 midbasses.

1 hour ago, fishball79 said:

That said, we get plenty of punch in open area concerts so im not sure if thats the solution.

If it won't sound good indoors in terms of midbass, then it will be worse outdoors as you'll lose any boundary reinforcement.

I feel you have a problem with your design somewhere but not knowing you, your tastes, experience and expectations, it's going to be difficult to offer more advice at this distance.