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-   -   8" speaker driver replacement (https://www.diyaudio.com/forums/multi-way/324520-8-speaker-driver-replacement.html)

Brettn56 1st July 2018 12:11 PM

8" speaker driver replacement
 
1 Attachment(s)
Hi, I'm after some advice or comments.
I built some cabinets to suit the Jaycar CW2136 drivers many years ago. Cabinet volume is 33ltr, 66mm port at 165mm length. They sound OK, but I'm looking for advice about some better quality 8" drivers that I could use to replace my existing ones. Drivers suitable for my existing 33ltr cabinets...

The lower driver in the picture is in a 40ltr separate compartment, and is driven by a separate 300wrms and (sub signals only). The sub is fine, just looking to improve the 8" driver and possibly the tweeter as well. Speakers sound very light sounding and lack bass without the sub woofer being active.

Thanks in advance.

haiqu 1st July 2018 04:01 PM

Zaph|Audio

system7 1st July 2018 04:42 PM

Decent reflex basses for two ways at 3kHz XO:
H1471-08 CA22RNY
W 200 S - 8 Ohm | Visaton

Let's put this down while I have the data:

Jaycar CW2136 8" bass:

Quote:

Older, but more powerful version of this: Woofer Speaker Driver - 8 Inch | Jaycar Electronics 200mm 8" "Response" driver: - OD: 210 - Mounting holes: 198mm - Cut-out: 184mm - Nom impedance: 8ohms - Power handling: 120watts RMS - Frequency range: 39Hz - 3500Hz - Sensitivity: 90dB 1watt 1metre - Voice Coil Resistance (Re): 6.9ohms - Resonant frequency: (fs)39.9Hz - Mechanical Q factor (Qms): 6.623 - Electrical Q factor (Qes): 0.506 - Total Q factor (Qts): 0.470 - Equivalent Volume (Vas): 32.8Lt - Cone Area (square metres): 0.0214 Vented Box- Box volume (litres): 33Lt - Tuning Freq (Hz): 39Hz - 3db Frequency (Hz): 38.3Hz Two Vent Options: - Vent dia: 66mm Length: 160mm - Vent dia : 50mm Length: 80mm Inside Cabinet Dimensions: - W 257mm - D 323mm - H 407mm Sealed Box- Box Volume (litres): 26.9Lt - Tuning Freq (Hz): 58.1 - 3db Freq (Hz): 58.7- Qtc: 0.707 Inside Cabinet Dimensions: - W 237mm - D297mm - H 337mm
Looks like you got the box right there.

https://www.diyaudio.com/forums/atta...0421212441-jpg

It's actually a closed box driver at Qts 0.47, I reckon. But the main thing with bass is the slope on the driver. A big 2.2mH bafflestep coil will sound a lot bassier than, say, 1mH. So a crossover issue, maybe?

Can we see the crossover schematic?

Brettn56 2nd July 2018 12:40 AM

1 Attachment(s)
Here's the crossover schematic.
They ar basic, I know. There is no L-pad, and the values were calculated for 8ohms, not the speakers impedance at the crossover frequency. Xover frequency is set to 2.5k, which again I know is not ideal....
They don't sound bad, just very 'light's.
I'll get a frequency sweep and a FFT/spectrum analyser and do a frequency plot of them in a few days.

Would I be better bi-amping them and using an active crossover?

Thanks again!

rabbitz 2nd July 2018 01:57 AM

Is that damping blocking the upper port? Midwoofer should be close to the tweeter.

system7 2nd July 2018 02:00 AM

It's way too late at night in Dear Old Blighty, and far too hot for a change, to go into crossovers.

But this is just as I suspected, my friend. The bass coil is too small, leading into all sorts of bass deficiency due to a thing called bafflestep.

Online calculators have their uses, but assume flat impedance from the bass unit. In fact you can flatten impedance with a thing called a Zobel.

But bafflestep has to be dealt with separately.

Your bass unit is a bit of an unknown quantity, apart from being a plastic cone which is usually quite well behaved.

I'll get back to you with the fix. Here's a taster: http://www.diyaudio.com/forums/multi...ml#post5431294

Yawns. Shuffles off to bed. Night. :o

Brettn56 2nd July 2018 02:56 AM

Thanks for the reply's!!

The damping material is only on the walls, the cabinets are definitely not stuffed with material.

I'll switch to bi-amp and do an active crossover. Thanks for the crossover recommendation! If they sound drastically better actively crossed, then i'll rebuilt the passive crossover and go from there. If they still sound the same, I'll change the drivers, and use your suggested crossover method.

TMM 2nd July 2018 06:41 AM

I've used those Response drivers before - not half bad bass but the distortion in the midrange was fairly severe due to the huge (>10dB) cone breakup node occurring low in frequency (about 2kHz if i remember correctly). Active crossover won't help, it's a driver limitation.

Maybe check out the Dayton Audio RS225-8/RS225P-8 - midrange will be much cleaner to start with. Not cheap (around $125AU each), but they are one of the few 8" drivers that i'd attempt a 2-way with. The Peerless 830869 is also workable, around the same price from Wagner Electronics.

rabbitz 2nd July 2018 07:31 AM

1 Attachment(s)
From the pic it looks like the damping material is going into the port inlet. Make sure there is a clear path from the woofer to the port.

Brettn56 2nd July 2018 09:31 AM

So in everyone's opinion, are the Dayton or the peerless better drivers?
Of should I find a sealed back mid-range, and make these a 3 way speaker?

I'll rebuilt the crossovers as per all the advice I have had so far, and setup a mic/sig gen/and my DSO and so a frequency plot. Be interesting to see the before/after result of just changing the crossover.


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