MF 1000

Sub bass & bass Speakers with 18" Volt RV4564 drivers

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After acquiring a pair of bass speakers fitted with Volt RV4564 drivers from eBay, the challenge now is to make them more aesthetically pleasing, if I make new cabinets - not to go too big, tune the existing cabinets to try to achieve sub 20Hz frequencies and eliminate any cabinet flexing/vibration.

As posted in the bits & bobs thread here is a pic of the speakers 'as collected' 

IMG_0045.JPG.e63b680119d49e56c81ec167805e028f.JPG

not pretty in any ones eyes.

A quick bit about the Volt drivers....

18" dia, weighing in at 17Kg each, they are the ones used in the top end PMC speakers and numerous studio monitors or high end home cinema subs.  With a vMax of +/- 12.5mm and a 8" dia magnet they are more or less bullet proof, so I doubt my MF A370 is ever going to over drive them.

Ill do some analysis with REW this weekend using the same dcx settings I've driven my transmission lines with and use this as a base line.

The front facing port is 150mm dia (good job we haven't a cat .....I could see them being an attraction as a 'home' 🙈.  The cabinet is nominally 167 litres ( 45 x 54 x 69 cm) and the current port length is 10 cm, which gives a tuning frequency of 56 Hz ☹️ - not very low for such a big driver.

A quick call of various port length/tuning frequency combinations for a 167 litre cabinet gives the following options:

51 cm port length - 25 Hz

80 cm port length - 20 Hz

98 cm port length - 18 Hz

124 cm port length 16 Hz 

The challenge now is 'snaking' a >80 cm long 15 cm dial pipe inside the cabinet to achieve a low tuning frequency.....possible but challenging 😁.

My usual approach to isolating cabinet stiffness will be applied using internal ribs and cross dowelling to support the walls and reduce potential colourations.

Visually it might be easier to simply wrap the cabinet in a new layer if mdf or ply prior to veneering etc, this would also aid reducing cabinet flexing as well.

I will try to remember to take pics of each change etc and measure it if I can with REW.

Edited by MF 1000
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Keith I think you've easily guaranteed a place in the 'big room' at Keggie again :)

Looking forward to seeing what you do with those and how they sound.

Im sure your MF would do a good job but if you seriously wanted to move the walls power is getting seriously cheap these days.

2 x 500 watts 8ohms RMS only £130, those volts will take more but it's bridgable to 1700 watts. If you can live with the constant fan noise that is, as sometimes people do just want to listen at lower levels. Or maybe another A500 they bridge up to 600 RMS, but they cost more than these KM1700s

https://www.amazon.co.uk/Behringer-KM1700-Professional-Stereo-Amplifier/dp/B01N6PW7FY/ref=sr_1_1?keywords=behringer+500+watt&qid=1553678476&s=musical-instruments&sr=1-1

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Are you sure those 18" drivers are big enough, Keith...? :whistle:

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Are you sure your calls are correct? I'm getting a 150 dia port length of 337mm for a 26hz . 

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2 hours ago, MF 1000 said:

The challenge now is 'snaking' a >80 cm long 15 cm dial pipe inside the cabinet to achieve a low tuning frequency.....possible but challenging 😁.

 

You could use flexi drainage pipe - comes in a variety of diameters:

https://www.drainagesuperstore.co.uk/browse/underground-drainage/underground-drainage-pipes/coiled-land-drain-pipes.html

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10 hours ago, cooky1257 said:

Are you sure your calls are correct? I'm getting a 150 dia port length of 337mm for a 26hz . 

I've re run the data on two different sites to calculate port lengths ....both produce the same results 

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10 hours ago, Tony_J said:

Nice idea Tony ....but it's in 50m lengths - and £106 

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2 minutes ago, MF 1000 said:

Nice idea Tony ....but it's in 50m lengths - and £106 

Ask a local builder for some offcuts?

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1 minute ago, Tony_J said:

Ask a local builder for some offcuts?

:^

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Alternatively...construct the port out of MDF - easy enough to fold it as necessary.

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Now there is an idea .....a discreet transmission line of sort - hmmmm 

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Keith you could use toilet rolls , but it might sound ...pants …:D

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The mdf constructed port could also provide the bracing too.......that's two in one Tony :^ xD

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1 minute ago, MF 1000 said:

Now there is an idea .....a discreet transmission line of sort - hmmmm 

Indeed. The ports on my Alpair/Tang Band speakers were made that way.

Of course you could go the whole way and do a proper TL tuned to something stupidly low - that would be fascinating...

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