Help with MLTL design for GPA416-8c

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Hi to all,
I hope there is somebody who can help me to design MLTL for my new GPA 416-8C. I found several designs here on forum for 416-8B but parameters are too different between these units. As much as I can see it is very important to have MJK matchad program which is not avaliable any more. So I need help from somebody who has them :)

T/S parameters for new GPA units are:
Qts=021; Qes=0.22 Qms=6.7; Vas=24.5 cu.ft; Fs=22.9Hz; Re=6.55; Vd=19.7 cu.in; Xmax=0.15 inch; Ref.eff=6.55%; Z=8 ohm.

Thanks,
Zeljko
 
I am myself so impressed by the results obtained with a 12cm FR driver loaded with a MLTL (see threads on Alpair 10FR in the full range forum) that I'm - like you - wondering how this kind of load would work with 15inch woofers. Have you found information in the meantime as regards the application with a 416? Or can you recommend the most relevant threads you've found so far?
Thanks in advance!
Chris.
 
There are couple of threads regarding design but unfortunatelly with version B of this driver which has different T/S parameters.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=115034&highlight=

http://www.diyaudio.com/forums/showthread.php?s=&threadid=113177&highlight=

In begining I was considering Onken design for this driver but it seems at least when I put T/S in Onken calculator that it is not good choice (A version is good one). Another solution is bass reflex box like M19 but my opinion is that MLTL is far superior .

For now I hope that someone who has MJK formulas and good expirience can help me with design.

Regards,
Zeljko
 
I have Martin's last releases of his TL modeling worksheets and would be happy to model an ML-TL for you but I need 3 T/S values you don't list; Le, Bl and Sd.

zeljkor said:
Hi to all,
I hope there is somebody who can help me to design MLTL for my new GPA 416-8C. I found several designs here on forum for 416-8B but parameters are too different between these units. As much as I can see it is very important to have MJK matchad program which is not avaliable any more. So I need help from somebody who has them :)

T/S parameters for new GPA units are:
Qts=021; Qes=0.22 Qms=6.7; Vas=24.5 cu.ft; Fs=22.9Hz; Re=6.55; Vd=19.7 cu.in; Xmax=0.15 inch; Ref.eff=6.55%; Z=8 ohm.

Thanks,
Zeljko
 
A couple of questions

Do you have in mind a maximum size for the cabinet and/or some maximum dimensions, like width or height, etc? What F3 are you hoping for? And, as a forwarning, I've never had much luck coming up with good TLs for low-Qts drivers, although having a 23-Hz Fs will help if you aren't wanting a really low F3. Last question, this is a 15-inch driver, is it not?

zeljkor said:
Thank you :)
Parameters I calculated and some measured are:

Sd=131.08 sq.in
BL=17.66
Le=0.37mH (measured)


Zeljko
 

GM

Member
Joined 2003
15" assembly on a 16" frame.

Yeah, my default MLTL for these old style drivers is Vb = Vas, Fb = Fs, but they are EBS alignments if not driven with a high output impedance, so ideally we also need to know what the power drive system is, room size, layout and where these will be located. FWIW, Altec liked this driver in ~9.43 ft^3/36 Hz. A smaller one was ~5.27 ft^3/40 Hz. Either suitable for SS and relatively high DF PP amps.

Looking forward to what ya'll come up with.

GM
 
I did a quicky ML-TL model yesterday and in a 5.2 cubic foot box, ended up with an F3 of ~45 Hz, very close to your "smaller" example. I want to look at an ML-TQWT just to see how it might perform, but I know a large box is going to be needed regardless.

GM said:
15" assembly on a 16" frame.

Yeah, my default MLTL for these old style drivers is Vb = Vas, Fb = Fs, but they are EBS alignments if not driven with a high output impedance, so ideally we also need to know what the power drive system is, room size, layout and where these will be located. FWIW, Altec liked this driver in ~9.43 ft^3/36 Hz. A smaller one was ~5.27 ft^3/40 Hz. Either suitable for SS and relatively high DF PP amps.

Looking forward to what ya'll come up with.

GM
 
Here's an ML-TL possibility

The internal dimensions I used were 15"W x 15"D x 40"H. The center of the 416-8C is located 9" from the top (or bottom) and the mass-loading port is located at the bottom (or top). The port is just a hole in a 1"-thick wall (could be baffle or rear panel), has an area of 20 square inches and could be round, square or rectangular (slot). I used a stuffing density of 0.75 lb/cu.ft., requiring a total of 32 ounces of stuffing located in the top (or bottom) 21 inches of the cabinet. The attachment shows the system response and when I expanded the vertical scale for better resolution, F3 is ~43 Hz. The air velocity through the port with the modeling input voltage of 2.83 volts is a smidgen below 0.5% the speed of sound. A little later today I'll try an ML-TQWT model.
 

Attachments

  • 416-8c mltl.gif
    416-8c mltl.gif
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I will drive 416 with 6080 SE amplifier. Room size is something like 3.6meters x 5 meters. Because of furniture configuration (and wife) I will put boxes 60 centimeters from back wall - smaller one (possible in corners also). I would like to achieve F3 of at least 35Hz if possible and I will cross it around 400-500Hz.

Zeljko
 
You can lower F3 by adding a series resistor (or by driving it with an amplifier having a high output impedance, I guess) but not enough to get it down to 35 Hz. And, the penalty will be quite a large loss in sensitivity. Basically you need a bigger box approaching 10 cubic feet like GM suggested. Just how big of a box can you (and your wife) accept? What form factor in this box are you thinking about? Is this going to be standalone box just for the woofer, or will it be multi-way with other drivers also included in the same box?

zeljkor said:
Is it possible to achieve better lower bass response by using high imepedance amplifier or by adding series resistor to driver to get higher Qts (of course I will loose some SPL)?
 
I am planning it to be standalone box. On top I will add Edgar midrange horn with Dynaudio D54 and for tweeter I will use Selenium D220Ti with JBL waveguide. Regarding size I can survive up to 14 cu.ft Now I can see that big roblem are dimensions since midrange and tweeter will be on top. Another solution would be if really more than this is needed to integrate midrange and tweeter with box.

Zeljko
 
An enlarged ML-TL

I increased the internal depth of the cabinet to 25", enlarged the port area to28 square inches, and increased the stuffing density to 1 lb/cu.ft., requiring 72 ounces total of stuffing (with no other changes). The gross cabinet volume is now ~8.8 cubic feet and F3 is ~36-37 Hz (see the attachment).

zeljkor said:
I will drive 416 with 6080 SE amplifier. Room size is something like 3.6meters x 5 meters. Because of furniture configuration (and wife) I will put boxes 60 centimeters from back wall - smaller one (possible in corners also). I would like to achieve F3 of at least 35Hz if possible and I will cross it around 400-500Hz.

Zeljko
 

Attachments

  • 416-6c mltl2.gif
    416-6c mltl2.gif
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Are you asking for a cabinet width of 25" but a depth of 15"? If so, the result will be the same as for a cabinet width of 15" and a depth of 25". Or, are you asking for the cabinet's depth and width to both be 25"? One can always tune the cabinet lower but it won't lower F3 in a given volume, it will just make the frequencies below F3 have a bit more amplitude at the expense of lowering the amplitude at F3 and above a bit.

zeljkor said:
Hi Paul, can you try to simulate with increased width ? Let say for example 25". Also to try to tune it lower ? What do you think?

Zeljko
 
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