MF 1000

Sub bass & bass Speakers with 18" Volt RV4564 drivers

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Super Wammer

Had an hour free around lunchtime to do some analysis with REW and try an idea I had.

The first sweep was to check just what effect the new bracing had made given it sounded better 'by ear' 

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the plot above compare the unbraced curve (red) with the braved curve (purple).  The bracing has given me another couple of dB response at 15Hz, but a slight drop in the 25-35 Hz area.  What is significant is the 12 Hz change in the dropout at 42Hz and an equal change around 88Hz....both are very narrow dips so don't necessarily have a big impact aurally but a gain is a gain.

I still had my 20Kg ballasted boxes that I used under my transmission lines......I wondered what the effect of placing them on top of the Volt cabinets would be.

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the plot above shows a comparison curve turquoise being without the ballast box and blue with the ballast.  Not much of a change really, but that drop out around 60Hz has an instant near 10dB uplift ....again quite narrow but a gain is a gain.

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this is my master comparison plot ...green is as I bought the Volts and purple is in the braced & ballasted format.  The response above 100Hz is by application of EQ on the KEF 104 bass drivers, but my efforts with port changes, bracing etc as well as some EQ has dramatically improved the performance below 80Hz making a far flatter response curve up to 80Hz (which is the nominal xover point).

I now need to build some ballast boxes to fit the Volt cabs and then try some other ideas I have.....watch this space.

Edited by MF 1000
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Super Wammer

Was sat thinking (glass of malt in hand etc) last night about how to apply the ballast best to the top of the cabs.  Had a thought of doing a quick test with a couple of spare concrete paving slabs 600x600 I had in the garden.

Carefully lifted them in place and carried out a quick scan with REW.

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whilst this appears to be a 'good' solution the extra weight ( approx 60kg in total fir a slab compared to my 20Kg ballast box) increases the drop out levels at 43 & 58 Hz....the upper one dropped out by around 5dB more.  So it's back to the ballast boxes.

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Super Wammer

Just got a second A500 at a v good price on eBay ....so watch this space.  Given I've got a spare channel on my two behringers I'm considering using a separate channel for each A500 feeding their individual Volts....and at 600 watts in bridged mono form I'm looking forward to seeing how this might change things.

Edited by MF 1000
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4 minutes ago, MF 1000 said:

Just got a second A500 at a v good price on eBay ....so watch this space.  Given I've got a spare channel on my two behringers I'm considering using a separate channel for each A500 feeding their individual Volts....and at 600 watts in bridged mono form I'm looking forward to seeing how this might change things.

Eeeeek! :notworthy:

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Super Wammer

Was just thinking about the <0.5 Richter scale restrictions on fracking .....do they apply to hifi subs :sofa:

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Should certainly be fracking loud...

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Not sure about fracking, I'd be more worried about it breaching the terms of the Strategic Arms Limitation Treaty.

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1 hour ago, MF 1000 said:

Was just thinking about the <0.5 Richter scale restrictions on fracking .....do they apply to hifi subs :sofa:

I suspect that you are still trying to blow that candle out....

Deep down you know you should have gone for the 24” drivers 😛

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Let me know when you're going to test it flat out. Mt best mate lives in Chester, so I can warn him to open all the windows to save them breaking.

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The acid test is whether the port wave from a rimshot can blow out a candle at 100 paces...if not, you're not trying hard enough 😂

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Super Wammer

Had some spare time after finishing some reports this morning .....so out came the drivers and I added some more broomhandle bracing between the rear of the cabinet and the broom handle cross bracing I added earlier.

A quick sweep with REW gave the plot below

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The green line is with the new bracing ....gaining around 3 dB at 15 Hz and around 6 dB at the 50 & 70 Hz peaks albeit with a slight loss in the 30-40Hz region - maybe I can eq that out.  

Ill wait now till the extra A500 arrives etc, but a quick listen before going out seems to back up the plot with a tighter bass line 😀

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Super Wammer

Pic of the extra bracing ...the vertical legs in this shot IMG_0082.jpg.147a8cf38ebfcb6043301ce15371db26.jpg

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Super Wammer

Keith. You are certifiable.

I will be across with the system destroyer CD in hand when you think you have them sorted. If I can bring SWMBO I will forgo the Armagnac and let Jane and SWMBO chat out of the room, drinking fizz, whilst you and I try the candle test in earnest. On Saturday I found my Chezi test disk from May 2006, in the very early days of the Wam, when we had the  Scottish contingent. I wonder if Chezi is still alive after another 13 more years of alcohol consumption?

Lee and I once attempted to get to  Glasgow for a bake off but were defeated by the snow and had to turn back before the Lake District. Good job as Glasgow was then snowed in for days!

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Super Wammer

Found some spare 18mm MDF in the garage this morning so I cut two panels to fit the rear of the cabs as this would be where most of the pressure from the driver will first impact etc.  Nine screws attaching each panel then it was time to plug in the mic etc and see what effect it had.  

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After some adjusting of eq the green curve is the rear panel brace, once again the very bottom end has improved by a couple of dB and a small reduction in the peak at 35 Hz - not sure yet if it's a room or cabinet/port effect causing that peak, but the curve up to 100 Hz is now a little smoother.  The purple curve is the cabs as I bought them.

A quick listen to Marcus Miller and my Boellmann Toccata test CDs showed a good move forwards with a nice balance at 'normal' listening levels.  Delivery of the extra A500 is due Weds or Thurs 😀.....will be interesting to see how the potential of more power/ control adds or detracts etc.

Edited by MF 1000
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