8" speaker driver replacement

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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.
 

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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:

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.

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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?
 
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!
 

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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-way/314732-wharfedale-shelton-xp2-minor-classic-imo-3.html#post5431294

Yawns. Shuffles off to bed. Night. :eek:
 
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.
 
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.
 
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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.
 
No reason to change the drivers at all at this stage.

Let's see how it goes first.

I have rustled up a crossover that does the right things with almost any well behaved 8" bass. Because I have tried it. I'd assume the 1" tweeter is about 90dB loudness. That is easily adjusted later.

I've used some of your existing capacitors to save money. If the tweeter is a quieter 87dB type, lose the 22R and replace 4.7R with 2.2R.

Cheap Non Polar audio electrolytics will be fine here. 10W wirewound and ferrite cored 1.5mH. Air core 0.2mH.

This will have far more bass than your current set up. I always fold component connections rather than cut them short. Makes components reuseable. Which saves money. I also keep a stock of wirewounds. Say pairs of 1R, 2.2R, 3.3R, 4.7R, 6.8R, 10R, 15R, 22R. They are cheap and it saves time. :)

You can build crossovers on a piece of hardboard. Or a PCB. You will need some speaker cable, of course. modest 5A does for me. Have a go.
 

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I would look at a 3-way top-box design which seals off the 33ltr volume and adds a 4" or 5" midrange in a small separate sealed volume. In the USA Dayton RS100-8 or RS125-8 are considered good value. On a flat baffle, BW3 circuit for the tweeter, and LR2 circuits for the midrange and woofer usually integrate well.
 
I think Steve is right - fiddling with crossover can help a lot. A measurement mic helps with getting it right. You can do it by ear, but it goes MUCH faster with a mic.

About $100 gets you a plug and play mic with a USB cable. The miniDSP site sells one. About $20 gets you a similarly good mic which you can plug into a phone:
Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android
I have both types. The main benefit of the $100 mic is being able able to do deeper nerd stuff like before-and-after graphs in REW.

The cheap one + a phone (& the Audio Tool app) is better for quick, average / in-room measurements.

-----

I also think Linesource and others are right - the current speakers are imperfect because the tweeter-to-midrange spacing is huge. Using your existing cabinet as a bass box and making a second (small) box for mid-high range would be a good upgrade.

If you did that, I'd recommend this as a mighty midrange that is stupidly good value (currently $30):
Subwoofer 6 - FS Audio

The VFM website lists it as a sub, which is wrong. It is definitely a mid; see my measurements at the end of this thread.
Measurement based cone damping / treatment
 
I would highly recommend a PC based mic for crossover design, there's much better software availability/freedom than tablet/phone based solutions.
The UMIK-1 looks decent although I haven't personally used one (I use a Dayton EMM6 and standalone soundcard)

If you are going active then all you need is a decent mic (and mic boom/stand) to design the crossover.
 
With everyones advice, I decided to bi-amp the speakers to determine 2 things: my crossover design was very poor (thanks system7) , and as a few of you have suggested the 8" driver is definitely not ideal for a 2 way system. Using an active xover has allowed me to adjust the crossover point 'on the fly' very easily, so I can find a happy medium. So far just from listening it sounds a lot better. Clearer bass and mid, and the high end also sound quite 'colourful'. Obviously me using these terms to describe the sound is like someone trying to describe colours... But compared to what I had previously it is a 100% improvement. Now I have found a good xover frequency that seems to sound the best, I will rebuild my passive xovers and then do some measurements. I've been away a lot lately, and am currently in an airport typing this. Thank you all again and I'll post some results soon. Brett
 
What frequency was that? 8" plus tweeter works very well, IMO. The best two way for adequate bass.

The US cousins always like low crossover around 2kHz. I prefer BBC style 3kHz negative polarity. Gives the tweeter an easy ride. Also solves the fierce time alignment problems with 8" bass. Half a wavelength at 3kHz or 5cms, you see. We must just hope your polycone bass doesn't have any horrors in frequency response.

687319d1529236762-6-8-woofer-system7-wlm-la-scala-clone-jpg


I've just got the parts for my newest build, above. I'm looking forward to this. The previous one was good anyway. But always room for improvement. :D
 
No reason to change the drivers at all at this stage.

Let's see how it goes first.

I have rustled up a crossover that does the right things with almost any well behaved 8" bass. Because I have tried it. I'd assume the 1" tweeter is about 90dB loudness. That is easily adjusted later.

I've used some of your existing capacitors to save money. If the tweeter is a quieter 87dB type, lose the 22R and replace 4.7R with 2.2R.

Cheap Non Polar audio electrolytics will be fine here. 10W wirewound and ferrite cored 1.5mH. Air core 0.2mH.

This will have far more bass than your current set up. I always fold component connections rather than cut them short. Makes components reuseable. Which saves money. I also keep a stock of wirewounds. Say pairs of 1R, 2.2R, 3.3R, 4.7R, 6.8R, 10R, 15R, 22R. They are cheap and it saves time. :)

You can build crossovers on a piece of hardboard. Or a PCB. You will need some speaker cable, of course. modest 5A does for me. Have a go.

Hi Steve; this is not a critique-I’m trying to learn the dark art of crossover design. What type of crossover is detailed in your schematic? It doesn’t resemble the schematics I’ve seen for a third order Butterworth as an example. Also do you use any online calculators or do you use longhand and formulae?

Thanks in advance,
Nigel
 
It's a circuit that works well with high inductance woofers, but Troels uses it with more regular woofers in the TQWT with an added 5kHz breakup notch that I didn't really like: TQWT-

First order with impedance correction.

I use Boxsim for sims. Software | Visaton

You can import frd and zma files for other drivers too.

These projects are quick "get you started" downloadable .bpj files: Boxsim Projektdatenbank
 
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