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Old 9th May 2009, 06:35 PM   #1
zeljkor is offline zeljkor  Serbia
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Default Help with MLTL design for GPA416-8c

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
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Old 14th May 2009, 05:19 PM   #2
elac310 is offline elac310  France
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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.
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Old 14th May 2009, 07:01 PM   #3
zeljkor is offline zeljkor  Serbia
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There are couple of threads regarding design but unfortunatelly with version B of this driver which has different T/S parameters.

Altec 416-Z 48" 846B MLTL

MLTL Cabinet for 416-8B

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
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Old 14th May 2009, 07:41 PM   #4
pkitt is offline pkitt  United States
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Default Re: Help with MLTL design for GPA416-8c

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.

Quote:
Originally posted by zeljkor
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
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Old 14th May 2009, 08:36 PM   #5
zeljkor is offline zeljkor  Serbia
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Thank you
Parameters I calculated and some measured are:

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


Zeljko
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Old 14th May 2009, 11:37 PM   #6
pkitt is offline pkitt  United States
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Default 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?

Quote:
Originally posted by zeljkor
Thank you
Parameters I calculated and some measured are:

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


Zeljko
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Old 15th May 2009, 02:23 AM   #7
GM is offline GM  United States
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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
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Old 15th May 2009, 02:59 PM   #8
pkitt is offline pkitt  United States
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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.

Quote:
Originally posted by GM
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
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Old 15th May 2009, 03:22 PM   #9
pkitt is offline pkitt  United States
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Default 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.
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File Type: gif 416-8c mltl.gif (6.7 KB, 465 views)
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Old 15th May 2009, 05:30 PM   #10
zeljkor is offline zeljkor  Serbia
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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
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