MLTL Floorstanders for Alpair 7MS

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hello!

Since the Alpair 7MS is right around the corner I have decided to replace my Alpair 6.2m MLTLs mains and move them to surround rears, I hope to pre-order these tomorrow and I'm excited!

I have MiniDSP that takes care of crossing over to two Tang Band 6.5" sealed bass units that handle all channels below 90hz. A Hifimediy T-1m to drive the mains, maybe this will be upgraded later and iNuke driving the Tang Bands.

I have very much enjoyed the sounds of the 6.2m drivers and the form factor the Woden/Planet 10 Sasquatch MLTLs and they look good as far as I am concerned! I have designed BR and sealed cabinets before but not a TL or MLTL so this is my first time trying this.

My aims for this build are:

1. Create compact floorstanders that work with my environment. As slim as possible, I am aiming for 16cm wide.

2. As they will be crossover to two sealed sub/bass units I want to ensure that the low end is clean and easy to integrate around 80-90hz.

3. To make my own design.

After lots of messing around with various allignments using Leonard Audio TL software I have come up with the attached design that is as follows:

13x17cm (204cm cross section area) pipe
77cm long
5x12cm vent at 49cm from the top of the cab
Driver is positioned 9cm from the top

All graphs are without stuffing.

It looks nice and flat and when stuffing is applied it seems to come up very smooth, is this too good to be true? I will post all graphs and hopefully someone might be able to chip in their thoughts on the simulation. As I understand, phase is important for integrating in to a crossover to subwoofers but I am not sure how to read this or tell if its ok. Also, efficiency doesn't seem too high or am I misreading things?

All input appreciated!

G.
 

Attachments

  • SPL.jpg
    SPL.jpg
    120.1 KB · Views: 1,312
  • Phase.JPG
    Phase.JPG
    103.7 KB · Views: 1,295
  • Impedance.JPG
    Impedance.JPG
    143.7 KB · Views: 1,267
  • Group Delay.JPG
    Group Delay.JPG
    86.7 KB · Views: 1,263
  • Enclosure.JPG
    Enclosure.JPG
    65.4 KB · Views: 1,266
Last edited:
I am not a big fan of that bump and sharp drop right after 50Hz.
If you take room resonance that often occur in that range into account, it might make a very boomy speaker... Unless you are after that sort of thing.

I like to use design and drivers in MLTLs that come up a little more softly without a hump to minimize that effect.
 
Yes, I agree. With stuffing that jump is less pronounced. How would adjust the design to tackle it?

I'll post graphs with stuffing when I am home.

I am not a big fan of that bump and sharp drop right after 50Hz.
If you take room resonance that often occur in that range into account, it might make a very boomy speaker... Unless you are after that sort of thing.

I like to use design and drivers in MLTLs that come up a little more softly without a hump to minimize that effect.
 
I am not at home at the moment (vacation!) so I can't try a couple of things, but you have the right idea... Changing the volume, length of the box, along with the tuning of the vent might help, but there are some drivers that you simply can't get to behave in a MLTL.
 
Well done for getting stuck in Graham. I've got your name next to a pair.


Scott posted the Pensil for this (i have to draw it now).

New Markaudio Drivers

dave

It's worth deconstructing this design and seeing what your software says and maybe working back from there.

Mark was very pleased yesterday when we were together to hear folk phoning to get drivers before I even had them :) Thanks you made me look like a super dealer!
 
No worries mate, hope the video went well!

Yeah, I've been (attempting) reverse engineering several designs, steep learning curve!

Excellent, looking forward to them, thanks Stefan!

Well done for getting stuck in Graham. I've got your name next to a pair.




It's worth deconstructing this design and seeing what your software says and maybe working back from there.

Mark was very pleased yesterday when we were together to hear folk phoning to get drivers before I even had them :) Thanks you made me look like a super dealer!
 
Thanks all.

Yes, I agree, I have attempted to model several but have had predicted responses that I can't believe anyone would pick. Either software, experience or black magic are at work with these mismatches!

I have read a few articles and followed the Neurochrome suggestions mapped out in the "Designing MLTL Speakers" article but all alignments I attempt result in this steep LF roll off. Can anyone hint at a solution or approach?

Also, Chris, Scott, Dave, Stefan, Perceval et al, I have noticed that in many designs the stuffing weight can be up to 12kg per m3 (Jim Griffins MLTLs most notably). Enclosure design aside, is this weight of stuffing critical to creating that smoother roll off or should I be looking to achieve it before stuffing is applied? Heavy heavy stuffing seems to start the roll off at around 100hz which is higher than I need to integrate in to my subwoofer / WAW set up.

Had these drivers worked in sealed cabs down to the crossover point I need I would have pursued this route however, I wouldn't have learnt anything and I think the crossover design would be stretched considering.

With my initial design I assume crossover to subs is easy as there is a broad stretch of flatness to sculpt. As speakers on their own, as Perceval quite rightly points out, not achieve a desirable sound when room gain is taken in to consideration. My subs have a q of just above 0.5 and matches my room perfectly.

Any thoughts appreciated.
 
frugal-phile™
Joined 2001
Paid Member
Most ML-TLs will have a shape at roll-off similar to what you find in a BR — but it won’t sound the same.

If you want a slower roll-off you have to push the box towards aperiodic (and usually give up some bass quantity). This is usually done with more stuffing.

Getting smooth reposnse at the bottom (ignoring the room) means killing the unwanted harmonics. The high order ones are fairly easy to kill with damping, but the 3rd & 5th (the 1st 2 unwanted harmonics) are harder. Traditionally it was just “use more stuffing” (althou a taper will push those up in frequency making them easier to damp and further away from the desired fundamental). Inevitably this meant losing some of the bass reinforcement. Modern modeling tools have introduced tricks that help kill those 2 harmonics without damping. Notably driver offset and restricted terminus (aka mass-loading). Using these tricks one can kill the harmonic with less reduction in the fundamental.

dave
 
Right, after a lot of umming and ahhing from Daves post I think this design could work with manual analysis of stuffing with mic and REW after contruction. I have read elsewhere that Leonard Audio software does not model stuffing too well so I won't trust it.

I have shortened the length by 4cm and tinkered with the port and stuffing.

Attached is a new SPL chart and a real-world implementation of the enclosure. Can anyone see any issues with the placement and clearances? The only thing that comes to mind is that it's a bit tight on the driver mounting and the port is rather large which may interfere with the CSA at the port location. As the port is round will this help waves pass around it?

I have to decided on front or rear ported now.

As always, any thoughts appreciated!
 

Attachments

  • Enclosure Sketch.jpg
    Enclosure Sketch.jpg
    994.7 KB · Views: 605
  • SPL More Stuffing.JPG
    SPL More Stuffing.JPG
    80.6 KB · Views: 606
I wouldn't worry too much about the port and waves passing through.

I usually put the driver lower to help tame the ripples instead of using heavy stuffing.

I don't like to force a driver to behave into a selected design. But who knows. Maybe it will be ok this time. That's the spirit of DIY. :)

The only other thing I'd recommend is to build a base for them. Tall and skinny enclosures are prone to tipping over... Pets, kids, earthquakes.... So, either extended legs or a wider base would help.
 
FWIW, a similar albeit slightly expanded reaction to the above; if you want some constructive criticism, without going into too many specifics

-You're not far off end-loading, which provides maximum excitation to the fundamental but also all harmonics; if possible I would adjust the driver tap location to reduce excitation the 3rd & 5th. You may need to tilt the box back slightly due to the lower driver mounting position.

-Vent tap location seems a bit high to me. Assuming an internal axial length of 760mm, I'd be inclined to either place it as close to the bottom as possible for maximum gain, or centre on 645mm down from the internal top.

-If you think the duct CSA is too large, reduce it & its length accordingly for the target Fb. With a practical hat on, the 7MS is a 4in driver, not a 15in woofer so providing you don't go too far vent mach shouldn't be too much of a problem.
 
I usually put the driver lower to help tame the ripples instead of using heavy stuffing.

The only other thing I'd recommend is to build a base for them. Tall and skinny enclosures are prone to tipping over... Pets, kids, earthquakes.... So, either extended legs or a wider base would help.

I have some mini outriggers as can be seen in the attached image and yes I agree, I should be aiming for best response but domestic life dictates certain things! Thanks for your input, hope you can further chip-in as I bumble through this!

FWIW, a similar albeit slightly expanded reaction to the above; if you want some constructive criticism, without going into too many specifics

-You're not far off end-loading, which provides maximum excitation to the fundamental but also all harmonics; if possible I would adjust the driver tap location to reduce excitation the 3rd & 5th. You may need to tilt the box back slightly due to the lower driver mounting position.

-Vent tap location seems a bit high to me. Assuming an internal axial length of 760mm, I'd be inclined to either place it as close to the bottom as possible for maximum gain, or centre on 645mm down from the internal top.

-If you think the duct CSA is too large, reduce it & its length accordingly for the target Fb. With a practical hat on, the 7MS is a 4in driver, not a 15in woofer so providing you don't go too far vent mach shouldn't be too much of a problem.

I hear you, attached is a sim with a very flat line with and a LF bump I can't seem to get rid of. I have reduced the port considerably, I was being overly careful re velocity! It's Aanoying that this alignment just isn't convenient. I am sad to say that form is having an annoyingly high influence over function.

I am trying to replicate the form factor the Sasquatch you designed as it suits my room perfectly. They are already tilted back some and they are perfect (obvs not as perfect as the 7MS might be!!!). Will my former design (or a similar tweaked design) be that poor?

Again, thanks both for input. This is proving trickier than I thought and I say this every time!
 

Attachments

  • FLAT.JPG
    FLAT.JPG
    151.9 KB · Views: 592
  • Sasquatch.jpg
    Sasquatch.jpg
    536 KB · Views: 589
Last edited:
Thanks Scott for chiming in and give a much better reply than mine! :)

Graham... Are you so dead set on that Alpair driver?
It doesn't look like a good match for the MLTL design.
It kinda looks like you are trying to fit a round driver into a square hole!
I'd suggest to look at a different driver, more suited to the MLTL design... There are plenty of them at about 4".

If you already bought that driver, then, may I suggest a simple vented design that could reach 80Hz, low enough to integrate with your subs.

You can still have the same looks as a MLTL, just make a long empty base to put the simple vented enclosure on top. Even better, fill the empty base with sand.

I am on an iPad and no access to my computer so I can't model a vented enclosure, but there might be some floating around already.
 
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.