91dB Sensitivity and 114dB Max from a Pair of 2in Drivers?

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#21
xrk971 said:
Nice work Pelanj! I was going to make the same thing but seems you have beat me to it - can you share the CAD files?


Btw,
Has anyone tried this PC68-8 driver? Looks pretty good on paper and reviews all positive. Fiberglass cone is nice.

Dayton Audio PC68-8 2-1/2" Full-Range Poly Cone Driver
Click to expand...

Interesting driver you found. Also interesting is a 5db drop about 3kHz. That means in a small baffle like this, baffle step will flatten it off....
 
#22
I think I’ll order some of those PC68-8’s and give them a try. A good “filler” item to make the $100
Minimum for free shipping. 🙂

Not too many fiberglass cone full ranges are available at 8ohms for this price since the TG9FD-8 became unobtanium.

I love the fiberglass fullrange sound. SS 10F as an example. Glassy smoothness.
 
#26
Hey X,

If you like fibreglass cone full range, you should try this one from SB Acoustics. A low Fs for this category of speakers. Sound is really smooth with no peakiness. The downward slope in frequency response means baffle step might not be necessary in narrow column. Would be nice to place in series - parallel arrangement to boost sensitivity.....

SB Acoustics SB10PGC21-4 3" Full Range

I tried it in a small BR and was very impressed with the sound. Would love to try in a frugal horn that you built using foam core...
Oon
 
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#28
I have had the SB10 since they came out with it.
It's nice and well-behaved enough if not pushed too hard.

But it has a strong distortion peak at 4kHz, and would probably be annoying if it is pushed a bit.

The SBAcoustics 3” SB10PGC21-4 / Fiberglass driver

I use them in my camper right now and they do an ok job. Even had people compliment on the sound, although they do not know high end music, they usually listen on a little JBL portable mono speaker! ha ha!
 
#29
Some progress🙂
 

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#31
perceval said:
I have had the SB10 since they came out with it.
It's nice and well-behaved enough if not pushed too hard.

But it has a strong distortion peak at 4kHz, and would probably be annoying if it is pushed a bit.

The SBAcoustics 3” SB10PGC21-4 / Fiberglass driver

I use them in my camper right now and they do an ok job. Even had people compliment on the sound, although they do not know high end music, they usually listen on a little JBL portable mono speaker! ha ha!
Click to expand...

I missed this thread somehow. Thanks for the measurement. That’s too mediocre for my purposes.

851187d1591676326-sbacoustics-3-sb10pgc21-4-fiberglass-driver-sb10-dist-png
 
#32
Some more progress🙂 The only problem is, that the 15 mm plywood is really more something like 14.8 mm. I can really understand, why they say these are handmade, there will be a lot of sanding🙂 I must say that the layered plywood construction looks really good and feels very solid. I learned a few things in the process through making mistakes.

This little project could be made on a small 3018 CNC. The intended use will be in a two way system with a mono Karlson bass box. And maybe over time, two dedicated midbass units using the same construction will be built, maybe with a built in 1st order crossover. A 6" - 8" driver with matching sensitivity would be used.

I still do not know which connector to use, an enclosed 6.3 mm jack would be one option.
 

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#33
Common sense plays in the ratings.

The 91 dB rating is at 2.83 volts.
so its 2 watts @ 4 ohms, not 1 watt

Its 2 drivers to get 5.5 mm xmax

one driver would be only 2.2 mm

100 watts is the thermal rating of 2x 50 watt drivers

The likely power @ 10% distortion is 25 to 40 watts
and that would include the 150 Hz highpass.

without filter you would not get more than 3 to 5 watts
like any other small speaker

A horizontal splayed baffle @ 30 to 45 degrees
will improve horizontal dispersion and reduce combing.

instead of multiple combing frequencies with horizontal
speakers, you get one comb frequency
usually around 600 to 800 Hz

the frequency will slightly rise or fall
depending on the splay angle.

its a tradeoff 45 degree splay has best dispersion
with more notable single comb notch.
30 degree splay has less comb notch and slightly
less dispersion
 
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#34
A 3FE22 (8 ohms) should have a total Q around 0.9 and the resonance will be around 220 Hz. That looks quite promising for the intended purpose. I think I will wire the drivers in series instead, to make a simple passive single cap crossover possible. Bipolar electrolytics with a foil bypass cap should be good enough for trying out.
 
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