Foam Core Board Speaker Enclosures?

[tb46]

Hi xrk971,

That looks nice. I'm still trying to figure out the AkAbak.

Regards,

 

[Carlp]

OK, I'm tempted by the Karlsonator. I've wanted to play with this design for a while but not willing to commit to a wood build nor full-size drivers. But I could give a go with foam core and I have a quad of this speaker:

Pioneer A11EC80-02F
Paper cone w/cloth surround.
20 watts RMS/30 watts max
Voice coil diameter: 1"
Impedance: 8 ohms
Frequency response: 70-15,000 Hz
Magnet weight: 9.3 oz.
Fs: 70 Hz
SPL: 90 dB 1W/1m
Vas: .31 cu. ft.
Xmax: 1.1mm
Qms: 1.40, Qes: .47, Qts: .35
Diameter: 4-1/2",
Mounting Depth: 2-3/8"

Any thoughts about applicability of these dirvers? Anyone care to help me figure out how to size for these (I'm willing to do the work but don't know where to start).

Thanks for all this work, xrk!

 

[xrk971]

CarlP,
When I have some time I will run a sim for you. The look like they will work fine. I am guessing that it will fit in a 3/4 scale Karlsonator.
X

 

[xrk971]

Dual Pioneer AC11EC80 in 0.67X Karlson

OK, I'm tempted by the Karlsonator. I've wanted to play with this design for a while but not willing to commit to a wood build nor full-size drivers. But I could give a go with foam core and I have a quad of this speaker:

Pioneer A11EC80-02F
Paper cone w/cloth surround.
20 watts RMS/30 watts max
Voice coil diameter: 1"
Impedance: 8 ohms
Frequency response: 70-15,000 Hz
Magnet weight: 9.3 oz.
Fs: 70 Hz
SPL: 90 dB 1W/1m
Vas: .31 cu. ft.
Xmax: 1.1mm
Qms: 1.40, Qes: .47, Qts: .35
Diameter: 4-1/2",
Mounting Depth: 2-3/8"

Any thoughts about applicability of these dirvers? Anyone care to help me figure out how to size for these (I'm willing to do the work but don't know where to start).

Thanks for all this work, xrk!

CarlP,
Here is the sim of the Pioneer 4.5 in full range in the Karlson. It looks like a 0.67X Scale cabinet with the vent further scaled to 0.90X works well. There may be an issue with cone excursion though. It sure is sensitive with two drivers though. This is 2.83V into 4 ohms so it really is 2 watts input power. Measured at 1 m with speaker 1 in from wall. The last plot is the speaker 60 in away from back wall and mic at 3 m away. The bass has some fall-off and I am not so sure about the rising response - the T/S parameters were kind of sketchy. I googled the Re at 7 ohms and Sd at 64 cm^2. They may not be right.
Regards,
X

 

[Carlp]

CarlP,
Here is the sim of the Pioneer 4.6 in full range in the Karlson. It looks like a 0.67X Scale cabinet with the vent further scaled to 0.90X works well. There may be an issue with cone excursion though. It sure is sensitive with two drivers though.
Regards,
X

Wow, thanks a ton X! I wondered about the low Xmax. Looks like a problem primarily below 50Hz, but this driver doesn't do much below 70. I wonder if I might I be safe anyway. Hmmmm. I may try it but I like the drivers and don't want to damage them...

Also, any idea what happens above 5k Hz? These aren't stellar in the way upper ranges, but I'm 50+ and don't hear a ton up there anyway. More hmmmm.

Thanks again, X
Carl

 

[GM]

Pioneer A11EC80-02F

FWIW, a bit more realistic specs.......

GM

 

[IG81]

FWIW, a bit more realistic specs.......

GM

+1 on this. I had a pair until recently and they were much closer to these parameters than the ones posted on seller's websites. IIRC, none of the ceramic magnet A11 ever had a low Qts, you have to go back to the AlNiCo versions. Could still work decent in a "lossy" foamcore Karlsonator, as xrk971's little Vifa also have higher Qts.

Here, I retrieved what I measured on my pair, maybe my Vas value is a bit fudgy though.

Re 7.0 ohm
Fs 116 Hz
Qms 2.28
Qes 0.9
Qts 0.64
Vas 2.27 L
BL 5.32 N/A
SPL 88.1dB/W/m

IG

 

[xrk971]

Thanks guys. I will put these new numbers into the model and now I have another set of measured parameters for these guys. PE is selling an in-house GR branded replacement of this driver, is that any good?

 

[GM]

Actually......... I have a pair of the [Pioneer] low Qt ceramics made by Foster, but they were the mids driver I 'rescued' from some 'early '70s MCA? speakers sold at J.C. Penny.

GM

 

[GM]

Thanks guys.

PE is selling an in-house GR branded replacement of this driver, is that any good?

You're welcome!

Dunno, but if they are as far off spec wise as their 8" BOFU replacement, about all they're good for is skeet practice.

GM

 

[GM]

maybe my Vas value is a bit fudgy though.

Based on Fs, Qes, SPL, not enough to matter.

GM

 

[IG81]

Actually......... I have a pair of the [Pioneer] low Qt ceramics made by Foster, but they were the mids driver I 'rescued' from some 'early '70s MCA? speakers sold at J.C. Penny.

GM

Interesting.

Based on Fs, Qes, SPL, not enough to matter.

GM

My SPL is directly derived from that possibly fudgy Vas though, so who knows? It does feel uper-80ies sensitive TBH.

Thanks guys. I will put these new numbers into the model and now I have another set of measured parameters for these guys. PE is selling an in-house GR branded replacement of this driver, is that any good?

Hadn't seen that A11 replacement yet. Good to see they are not carrying on advertising the ancient specs. Physically, it'd fool me from the front, though there are differences in other places. The version I had measured pretty well, but was somewhat bland-sounding ultimately.

IG

 

[GM]

True, but only the Cms part of the equation, otherwise there would be no variance, which there is, just not enough to matter acoustically.

GM

 

[KLBIrd]

I cut the whizzers off of my GRS 8". They make better woofers than full range drivers.

 

[xrk971]

FWIW, a bit more realistic specs.......

GM

Here is the sim with GM's T/S parameters and same 0.67X scaling as previous. First is speaker 1 in from back wall at 1 m measurement, next is impedance, third is cone displacement, fourth is speaker 60 in from back wall and mic at 3 m from speaker. I would not worry too much about the excessive cone excursion as long as you use a low power amp (< 5 watts). The last plot is cone displacement with 4 watts input power (4 volts into 4 ohms). Below 50 Hz, you will hit 2 mm of travel (probably OK?). The revised T/S params have a much weaker motor and the cone motion is pretty well controlled I think. If you are really worried, place a ~750 uF cap, that can probably be placed in series to high pass and prevent excessive excursion.

 

[Carlp]

+1 on this. I had a pair until recently and they were much closer to these parameters than the ones posted on seller's websites. IIRC, none of the ceramic magnet A11 ever had a low Qts, you have to go back to the AlNiCo versions. Could still work decent in a "lossy" foamcore Karlsonator, as xrk971's little Vifa also have higher Qts.

Here, I retrieved what I measured on my pair, maybe my Vas value is a bit fudgy though.

Re 7.0 ohm
Fs 116 Hz
Qms 2.28
Qes 0.9
Qts 0.64
Vas 2.27 L
BL 5.32 N/A
SPL 88.1dB/W/m

IG

Thanks for the input, guys. I don't yet know how, nor have the capability, to measure T/S params (though I do want to start trying). I have wondered about the 70Hz Fs figure but I currently run them in a "BD Pipes" enclosure (transmission line) with rear firing driver and no baffle step correction, and they go surprisingly low (no measurement).

 

[Carlp]

Here is the sim with GM's T/S parameters and same 0.67X scaling as previous. First is speaker 1 in from back wall at 1 m measurement, next is impedance, third is cone displacement, fourth is speaker 60 in from back wall and mic at 3 m from speaker. I would not worry too much about the excessive cone excursion as long as you use a low power amp (< 5 watts). The last plot is cone displacement with 4 watts input power (4 volts into 4 ohms). Below 50 Hz, you will hit 2 mm of travel (probably OK?). The revised T/S params have a much weaker motor and the cone motion is pretty well controlled I think. If you are really worried, place a ~750 uF cap, that can probably be placed in series to high pass and prevent excessive excursion.

Thanks a ton, X. I'll probably be running it on SE amps (tube and ss) from 1.5 to 5 wpc, and not especially loud, so I'm probably safe. If the efficiency is really up there, I'm interested to see how the low end sounds. I was starting to work out the cap high pass to at least run tests (I thought it was more like 400uF for 50 Hz - 750uF would go lower - so I should check my calcs).

I'll have a go at this as soon as I can and report back. This week is shaping up to be BUSY and following week I'm off canoeing, so it may be a few weeks now. But I'll try to get started today.

 

[xrk971]

Remember it is 4 ohms.

 

[Carlp]

Hmmm. So one cap for the two drivers. That makes sense. Thanks!

 

[xrk971]

Looking forward to seeing your build. So you will be doing it in foam core right? It goes fast.