Wharfedale speaker improvements

[Dave Bullet]

As an exercise to test my measurement setup and knowledge of SpeakerWorkshop, I've designed a new crossover for a pair of old Wharfedale 505.2 speakers.

Details are on my web page here

I welcome any feedback, questions or criticism (of the speaker crossover redesign - not the crappy website that is )

Thanks,
David.

[AMV8]

Hi

I would be interested to hear how the rdesigned speaker sounds.

One comment is that the 8" base mid unit seems to have an extended upper range. One possibility is that this caused the lack of clarity in the mid range by being too slow as an 8" unit to respond. If you are happy that the 8" is ok then you could improve the mid range detail by direct connecting the 8" base / mid unit ( ie no filter ) and just include a high pass filter on the treble unit. From the look of the curves a one pole or two pole filter might be sufficient for that purpose.

Just a thought.

Don

[Dave Bullet]

I am all for a simpler crossover.

The problem I have with the 8" mid/woofer is it really starts to droop beyond 2KHz and the off-axis response really suffers.

As such, I believe I have to crossover earlier. The 27TBFCG can handle a lower crossover point as long as the acoustic HP is steep enough.

I originally only had an inductor low pass on the woofer resulting in a 2nd order LP slope, but couldn't get good phase integration. I tried crossing over the 27TBFCG higher, but found the off-axis problems and drooping response which led me away from that design.

Going 2nd order on the woofer and adding the 8uF cap helped phase alignment a lot.

At only (?) USD$51, I might just order the parts and try them out. If good, I'll buy a second pair of tweeters.

Cheers,
David.

[Dave Bullet]

Another issue I have with running the 8" driver higher would be increased distortion due to cone flexing. It is a soft polypropylene cone and at higher frequencies I doubt it is acting like a rigid piston. Cutting it off as low as possible would reduce distortion.

Thanks for the advice though.

One thing I might try is remove the impedance compensation on the woofer now it is a 2nd order electrical filter.... may not be required (although will likely result in other component values to be changed). Without the zobel - high frequency impedance might also increase (a good thing).

Cheers,
David.

[AMV8]

Hi

With the additional information you have given I agree it would not help to run the 8" at higher frequencies. A polypropylene cone does not normally work well in the higher ranges and sounds wooly. You are probably better to cross over lower. If the speaker still sounds wooly I would then add a 5" midrange and use the 8" simply as a base speaker.

Don

[sreten]

Originally posted by Dave Bullet


One thing I might try is remove the impedance compensation on the woofer now it is a 2nd order electrical filter.... may not be required (although will likely result in other component values to be changed). Without the zobel - high frequency impedance might also increase (a good thing).

David.

Hi,

The zobel should not be needed for 2nd oder electrical.

I do not understand the tweeter l-pad values, why aren't they higher ?
This is the root cause of the unnecessarily low high frequency impedance.

/sreten.

[Dave Bullet]

Hi sreten,

I was hoping you would reply - you are always a good source of feedback / critique on designs.

Re zobel - agreed. The iterations I went through were:
1. Try first order electrical on woofer to hit 2nd order target acoustic
2. Put zobel in which hit target slope
3. Tried 2nd order electrical on woofer to help shape the 2KHz baffle diffraction anomaly

I forgot to take the zobel off and tune again to see if required. Will do that tonight and post results.

Re tweeter L-Pad. I tried both increasing series / parallel resistance (and one or the other). The net result was too much attenuation of treble relative to woofer efficiency. I either ended up with a lower "shelf" of treble (series resistance increase) or a dip in upper treble (parallel resistance increase) - I might have got that the wrong way around.

In any case if you can offer any advice on how to increase impedance that would be great. I'll model some graphs and post tonight to show you the effects of what I mean.

Thanks,
David.

[Dave Bullet]

Hi sreten,

following your advice, I've improved things. still need to play around but here is the latest.... looking better (parallel resistor in tweeter circuit now gone)

I found the zobel on the woofer was still required. A plain 2nd order is not enough (unless I go 3rd order), since a 0.7mH series inductor doesn't give enough cut / shape, and increasing it cuts too much.

Dave.

[Dave Bullet]

The frequency response still maintained...

[Dave Bullet]

And finally the modified crossover: