Noob - I need help putting a specific driver in an ML-TL

[netcastle]

I have been through many of these threads and the one common theme I see is that in order to effectively model an ML-TL you need MJK's worksheets. If someone could help me out I would be so appreciative. My head is hurting these last few days trying to figure out a simple way to do this. It all leads back to the worksheets.

The driver is a Seas ER18RNX

T/S:
re : 5.9
le: .67
Bl: 7.2
Fs: 37
Sd: 136cm2
Vas: 32l
Qms: 1.58
Qe: .39
Qt: .32

I'm looking for floor standers which is why I am not going with Zaph's design. And I figure if I am going with floor standers, why not reap the benefits of an ML-TL? It looks like this driver would be a good candidate but I just don't know where to put it in the enclosure, where to optimally put the port, what the port dimensions should be, how tall the box... A BR is easy, there is just no good way for an English Major such as myself to figure this out. Thanks.

[pkitt]

The attachment shows the system response for an ML-TL I modeled with Martin's ML-TQWT worksheet. I modeled a cabinet with INTERNAL dimensions of 6.5"W x 9"D x 40"H. The ER18's center is located 8" (internally) from the top. The mass-loading port can either be a 2.5"-diameter tube with its center 2" above the bottom of the 40" height, or it can be a 1"H x 5"W slot port located at the very bottom. Either type of port needs a length of 3" and can be located on either the baffle on the rear panel. I used a stuffing density of 0.75 lb/cu.ft. You'll need a total of 11 ounces of stuffing distributed uniformly by density in the top 26-27" of the cabinet. You'll see in the attachment that F3 is about 37-38 Hz. If you want it lower, the cabinet's depth and/or width could be increased to get a larger volume. I assumed you were intending this to be a MT with the tweeter located above the ER18 on the baffle. I modeled arbitrarily with 0.5 ohms in series with the ER18 to represent likely d.c. resistance of crossover inductor(s) in series with this driver. The graph depicts the likely SPL output with a 2.83-volt input.

[netcastle]

pkitt,

Thank you very much. The graph looks very promising and my only concern is that they may end up a little boomy when room gain is taken into account. Would you recommend dealing with this in the crossover, or would a slightly lower box volume tame that roll off a little?

-Tim

[pkitt]

Originally posted by netcastle
pkitt,

Thank you very much. The graph looks very promising and my only concern is that they may end up a little boomy when room gain is taken into account. Would you recommend dealing with this in the crossover, or would a slightly lower box volume tame that roll off a little?

-Tim

If you reduce the cabinet depth to 7" and make the port 4" long, F3 rises to 40 Hz (you only need a little over 8 ounces of stuffing in the same space with this smaller cabinet volume). Unless you over-stuff to force the shape of the knee to be more rounded and the initial roll-off a bit slower, which may have negative side effects elsewhere, there's not much you can do IMO outside of the crossover to change the shape of the curve below the knee for these drivers.

[netcastle]

pkitt,

Thank you for your input. I am going to take your suggestions and build this cabinet. The more I thought about it, I could only imagine the size of an inductor needed to tame a low end roll off, so I guess I agree as well. I will post back when I get this done and post some results.

-Tim

[sreten]

Originally posted by netcastle


I'm looking for floor standers which is why I am not going with Zaph's design.
And I figure if I am going with floor standers, why not reap the benefits of an ML-TL?

Hi,

There are very good reasons to go with Zaphs design in any sort of box.

FWIW if you want less boomy bass you make the box bigger, not
smaller, and/ or tune the port or ML (in the TL) lower than "flat"
would indicate.



Do not ignore Zaphs measured parameters.

http://www.geocities.com/woove99/Spk...18RNX_2Way.htm

or WJ's tuning options :

2) You want to build the design in a floorstanding cabinet, which
means a little more baffle gain due to the extended baffle height
(see the effect of using a tall baffle on frequency response)
Þ Use my default crossover;

/sreten.

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spk...esigningXO.htm

http://www.zaphaudio.com/
http://www.rjbaudio.com/projects.html
http://www.geocities.com/woove99/Spkrbldg/
http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm
http://htguide.com/forum/forumdisplay.php4?f=39
http://www.humblehomemadehifi.com/

[netcastle]

Originally posted by sreten
[B]

Hi,

There are very good reasons to go with Zaphs design in any sort of box.

FWIW if you want less boomy bass you make the box bigger, not
smaller, and/ or tune the port or ML (in the TL) lower than "flat"
would indicate.

sreten,

Thank you for your advice. I have looked into zaph's designs and respect his contributions to this community. I have also heard excellent reviews of the
sr71. In fact, I had intended to build these, but a floor stander fits well into my room and when I started learning about TL's I couldn't resist. Can you blame me

In response to your comment, are you suggesting that the bigger box pkitt modeled will be the better option for accurate lowend reproduction (I think that is what you are saying - and they are the ones I would like to try)? Additionally, if I place these near a wall (which I must) I should go with a significantly reduced baffle step to accommodate the boundary and baffle reinforcement? I am also using the H1189 (TDFC). Will the reduced baffle step crossover from zaphs design work?

-Tim

[netcastle]

Do not ignore Zaphs measured parameters.

http://www.geocities.com/woove99/Spk...18RNX_2Way.htm

or WJ's tuning options :

Or these? (I got hung up on the first part of your post. I'll have a look here as well).

[sreten]

Hi,

Both designs use the 27TDFC aka the H1189, so no problem there.

The ER18RNX would work well in a 20L to 22L vented floorstander,
an arrangement like the following could lower the overall hieght :

http://www.humblehomemadehifi.com/Tempo.html

Adjust hieght for the best axis, the depth for internal volume.
(could be built with a vertical back if you so inclined, but harder).

IMO it should be tuned low, 33Hz to 35Hz for best in-room bass.

TL's, or MLTL's AFAIK to work properly need more internal volume,
usually too much for a sensibly vented box, but is a way of getting
more bass ..... but possibly e.g. in 3 way you be better off using
that volume with a bigger bass driver vented low down than usual.

TBH I'm no expert on MLTL's and suppose e.g. that the Tempo
above depending on the stuffing strategy would act like a MLTL.

FWIW pkitt's numbers indicate a ~ 38L cabinet tuned to ~ 45Hz,
but presumably these numbers are based on the given parameters,
which in particular have higher Vas than measured by Zaph.

AFAICT MLTL's are very different to TL's, so if your after classic TL
bass then you'd need a folded line, I'd suggest a 4 to 5:1 taper.

http://www.quarter-wave.com/TLs/Alignment_Tables.pdf

http://www.quarter-wave.com/TLs/Alig...tor_3_3_09.xls

Cabinet similar to this :
http://www.seas.no/images/stories/di...t/thor_cab.pdf

/sreten.

[Fast1one]

Instead of starting a new thread, I am going to bump this for my question. I am also interested in using the Seas woofer mentioned above in a quarter wave design.

Can someone please help me with the design of an ML-TL? Box size is not a big concern, but I do have some requirements and goals:

• Overall cabinet width of 9 inches
• Woofer located 12 inches down from the top surface, including wood thickness
• Extension to around 40hz in room

The design listed above is too peaky for my tastes. I prefer flat response or even a slight roll-off to prevent boominess. Will an increase in stuffing help in this department? Thanks.