Sub bass & bass Speakers with 18" Volt RV4564 drivers

[MF 1000]

A weeks absence from here ( not a ban ....damaged iPad and password issues) let me sort a couple of other bits on the Volts.

Between rain showers etc I managed to get the 18mm plywood cut and drilled (25 counter sunk fixing screws per sheet) to fix to the rear baffle of each speaker, which was 'only' 30mm MDF.  The aim of this was to be both visually finishing off the rear and brace/seal the baffle.

A good layer of wood adhesive as applied to the MDF then on with the ply and 25 torx drive screws.  

Before any critical listening I decided to allow 24 hrs for the glue to work it's magic and then it was out with someone me reference tracks.  Bass seemed deeper and the decay was more detailed.  Not had chance to check with REW or take pics as I'm away with work again .....maybe this weekend.

 

[MF 1000]

Did a bit of analysis with REW this afternoon and a few minor tweak on my eq setup.

The graph below shows that adding in the 18mm glued and screwed layer on the rear of the 30mm mdf baffle on the bass units has lifted the 30 to 180 Hz level by 3 or 4 dB

The blue curve is before the extra thickness and red curve after ....quite an area under the curve as my old maths teacher would say.

 

[tuga]

Did a bit of analysis with REW this afternoon and a few minor tweak on my eq setup.

The graph below shows that adding in the 18mm glued and screwed layer on the rear of the 30mm mdf baffle on the bass units has lifted the 30 to 180 Hz level by 3 or 4 dB

The blue curve is before the extra thickness and red curve after ....quite an area under the curve as my old maths teacher would say.

Intersting though somewhat unexpected (for me), particularly the bit between 30Hz and 200Hz.

Was this measurement performed near-field as required? It would be more informative to look at frequency response of the bin box in isolation.

 

[MF 1000]

As nothing has been moved in my room and I always have the mic in the same place (at ear height between the sofa cushions) this whilst not technically correct shows an actual comparison and the sound as I hear it at my listening position etc.

 

[tuga]

As nothing has been moved in my room and I always have the mic in the same place (at ear height between the sofa cushions) this whilst not technically correct shows an actual comparison and the sound as I hear it at my listening position etc.

Is it a measurement of both channels playing simultaneously? Nothing should have changed above 200Hz or even lower.

I would expect it to sound better balanced in the bass but I'd still try to reposition the speakers to get rid of the dip in the lower midrange. If you feel inclined to do so I suggest that you measure each speaker separately.

 

[bencat]

I am hopeless at reading and understanding these graphs but look at it after your comments and get what you are saying. This is just a question as I do not fully get the graphs but does that not also show that the 300 - 600 area is much lower and less smooth ? If this is wrong then could you explain for bears of little brain the difference in that area ?

 

[MF 1000]

I did some minor eq tweaking in that region Andrew ....needs a bit more work yet to smooth it out.  The main point of the graph though was showing a 3dB lift in bass response between 40 and 100 Hz just from a thicker/stiffer rear baffle.

 

[bencat]

Keith that was not me saying anything bad about this but more to see and have confirmed that what i was looking at was right . I know full well that you will continue refining this till you are fully happy just wanted to know if I was reading that area right . As it seems I was and that I could easily see the area you were working on and the results it gives me a much better idea of what I should be doing when I do my next set of DIRAC runs.

 

[MF 1000]

27K views ...wow 

now I wonder if it will hit 30k before the next show

 

[MF 1000]

Just checked in on this thread .....wow 28 000 views in just over 3 years ....incredible interest in my journey with these drive units and integrating them into my system . Hope to show you all how they really sound at this years show

 

[MF 1000]

Now what might you think I’m going to experiment with today ……

 

[bencat]

X-box ?

 

[MF 1000]

So this afternoon in between British GP coverage I did some experiments with using the papier-mâché egg box trays lining sides of the bass cab to see how this would affect or change the bass response on my speaker.


above is a pic as I was temporarily installing The boxes

I just did one cabinet …..well wrestling with 17 Kg drivers and 160 Kg cabinets isn’t exactly a fun pastime, then ran a test sweep with REW.


The orange curve was with the ‘std’ bubble wrap and the blue line is with the egg box lining. The egg box setup introduces a 2 dB dip from 40-80 Hz, so not a viable improvement.

As ever with this hobby/ obsession if you don’t try you never find out etc.

 

[tuga]

So this afternoon in between British GP coverage I did some experiments with using the papier-mâché egg box trays lining sides of the bass cab to see how this would affect or change the bass response on my speaker.


above is a pic as I was temporarily installing The boxes

I just did one cabinet …..well wrestling with 17 Kg drivers and 160 Kg cabinets isn’t exactly a fun pastime, then ran a test sweep with REW.


The orange curve was with the ‘std’ bubble wrap and the blue line is with the egg box lining. The egg box setup introduces a 2 dB dip from 40-80 Hz, so not a viable improvement.

As ever with this hobby/ obsession if you don’t try you never find out etc.

It is very likely that those crates will vibrate, maybe even be displaced, and they're not doing anything (they're only really effective at very high frequencies).
Probably not audible, though.

 

[tuga]

The idea is good though (though perhaps not really effective at the frequency range your subwoofer operates), but needs to be implemented differently:

 

[MF 1000]

I didn’t really expect it to be that effective given the wavelengths involved but as the egg trays were free etc the only loss was time etc and through failure we learn.

 

[MF 1000]

Humbled yet again as this thread hits the 30k views mark. I’m still working on the speakers ….completed the cladding of the other monitor last weekend, now some sanding/oiling to do ahead of Stoke.

Been very busy with my job so the connections to the three speakers in the top monitor are still via a connection block ……that will be a autumn job I fell to fit proper terminals etc.

 

[MF 1000]

Pop in my room at the show to experience them in all their sonic glory

 

[TheFlash]

Pop in my room at the show to experience them in all their sonic glory

What: the egg trays?

 

[MF 1000]

Egg trays were evaluated found wanting and sent for recycling

 

[deggie]

I see you were not eggstatic with the results then keith......hope to see ya sunday ......