Field Coil 515 enclosure suggestion

[zfhtang]

Hi, i just finished the test of A515 field coil driver. the T/S parameters are as following: 7.5V/3.29A
Re = 13.4061 ohms
Fs = 21.4535 Hz
Zmax = 648.7863 ohms
Qes = 0.1694
Qms = 8.0270
Qts = 0.1659
Le = 2.1547 mH (at 1 kHz)
Diam = 320.0000 mm ( 12.5984 in )
Sd = 80424.7707 mm^2(124.6586 in^2)
Vas = 454.6720 L ( 16.0566 ft^3)
BL = 34.4489 N/A
Mms = 111.2214 g
Cms = 494.8276 uM/N
Kms = 2020.9058 N/M
Rms = 1.8677 R mechanical

please help me to decide the best volume of the bass enclose? BR or MLTL? Vent to front or vent toward ground？
i use bassBox pro 6 to sim. the BBP give me a very small box.
i browse some forums. usually suggest a 8cu ft. to 10cu ft. for a altec 515b.

many thanks for sharing your experience!

 

[DeonC]

I am not one of the more knowledgeable patrons on the forum, but if I look at that low Qt, I would suggest a back-loaded horn. I cannot see this working in a sealed or even reflex box. Just my .

 

[tomtt]

I would suggest a back-loaded horn.

or a front loaded horn.



how much room does one have?

a field coil driver has an advantage of adjustable perimeters ...



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[freddi]

(beautiful BL product) the original Karlson K15, finalized in the summer of 1951 would be a good match. I'm not sure how a "Karlsonator" variant would do without member XRK971 doing an Akabak analysis.

 

[ogie]

Lots of choices.
Was it converted to FC?

 

[whgeiger]

Notes

Hi, i just finished the test of A515 field coil driver. the T/S parameters are as following: 7.5V/3.29A
Re = 13.4061 ohms
Fs = 21.4535 Hz
Zmax = 648.7863 ohms
Qes = 0.1694
Qms = 8.0270
Qts = 0.1659
Le = 2.1547 mH (at 1 kHz)
Diam = 320.0000 mm ( 12.5984 in )
Sd = 80424.7707 mm^2(124.6586 in^2)
Vas = 454.6720 L ( 16.0566 ft^3)
BL = 34.4489 N/A
Mms = 111.2214 g
Cms = 494.8276 uM/N
Kms = 2020.9058 N/M
Rms = 1.8677 R mechanical

please help me to decide the best volume of the bass enclose? BR or MLTL? Vent to front or vent toward ground？
i use bassBox pro 6 to sim. the BBP give me a very small box.
i browse some forums. usually suggest a 8cu ft. to 10cu ft. for a altec 515b.

many thanks for sharing your experience!

1) System Q is now a function of the current flowing through the field coil as well; so a lower supply voltage there, will provide higher Q values required to achieve certain alignments for bass reflex enclosures. To explore this alternative, you will need to calculate a set of TSP's for selected lower supply voltage levels.

2) The profile of the vent(s), is more important than its location (front, back, bottom). However, close proximity to an adjoining surface, changes port acoustics, particularly for a floor facing placement.

3) For the lower Q values, a horn load is needed. A corner bass horn (al la Klipsch) will provide good loading down to driver resonance. For all others, the driver will become unloaded long before that frequency is reached unless the horn footprint is huge.

Regards,

WHG

 

[zfhtang]

Many thanks for your kindly suggestion!
It is a A515 16 ohm of Mr. Wolf Von Langa' s field coil speaker. I just install it on my lowther pm8A open baffle according to lowther America' s design. It is really a very good speaker.
Mr. Wolf suggests a 825/828 enclosure. Or just a enclosure at least 8-10 cubic feet in net volume. vent to ground with a 127mm feet.
My room is 4mx6mx2.8m. I want the bass can flat to 40Hz.
The amp I am using is a 2A3 amp with 6C45 driver, freelunch schametic direct coupled.
I also bough a A2000 field coil compress driver. And I want to use a yuichi 290 wood horn with a cross over 800Hz.
The problem is I can't to sim this driver with a 8 cubic feet enclosure to get a good result. The BBP6 gives a beautiful curve with a small 4 cubic feet enclosure. F3=69Hz. If I use a 8cubic feet net volumn to sim, it can reach F3=35. But the curve is not flat.

 

[kevinkr]

I am running a pair of Iconic 165-8 (515-8G) in 11 cu ft Onken enclosures.. Quite pleased with their performance over the past 8yrs.

 

[DeonC]

If I use a 8cubic feet net volume to sim, it can reach F3=35. But the curve is not flat.

Don't worry about a curve not being very flat. They seldom are with a low Q driver in a ported box.

In a 4 cu.ft. box tuned to 37.5Hz, I get an f3 of about 43Hz. OTOH, I would try the designer's suggestions. Simulations aren't everything.

Deon

 

[GM]

The problem is I can't to sim this driver with a 8 cubic feet enclosure to get a good result.

Greets!

Yes, you can and you can do it all the way to Fs if you like assuming the field coil has enough adjustment and/or you add some series resistance to increase Qts to ~0.403 and cab net Vb = Vas.

For 8 ft^3, 35 Hz Fb, increase Qts until the response is flat, which will be somewhere in the 0.3 - 0.4 range.

GM

 

[zfhtang]

Thanks a lot! It is a very good feeling there is a lot of friends help me!
I will make a simple 8 cubic feet box to test the driver. After I finished I will upload relative test result here for further suggestion!

And how about the vent? Vent to ground with a 127mm feet is helpful for the bass extension? Or just vent to front?

Thanks again for your beautiful pictures and good sharing!

 

[GM]

You're welcome!

Normally, vents just need to be the standard forward firing and close enough to the floor to get good 2pi [half] space loading.

Once you raise the cab to down fire the vent, it's best overall to find the cab/floor gap that acoustically mass loads it enough to slightly lower its tuning, so must be found empirically.

GM

 

[zfhtang]

Thanks Mr. GM!

When I looking for information about ALTEC i always can found your name in many place. You gave instructions in chossing altec driver, discuss the enclosure. ... ...
I am very happy to get your help! I am on business trip. When I go back home I will publish my drawing here. And looking forward for further opinions.

Jason