Evaluating Ripole with 3 LW150-4 6"

Member
Joined 2021
Paid Member
Hi there!

LW150-4 6" is not really a sub but there's some bass for my desk. I have 3 idle that I got a while ago, not something I just bought.

What people don't like about ripoles is good if you have them right in front of you. So I gave it a try and I'm liking a lot how it sounds, usually at 50cm from me. Just a prototype using the driver's box.

I wonder if I can use 3 of them for a small 4mx4m living room, listening 2.5m from it.

I was reading a recent thread about simulating a ripole with HornResp. I was wondering if you could model it as a 6th order bandpass. So I took some measurements 2cm from each opening and tried a simulation with the approximate data. It doesn't change much with small variations. I find it interesting that the peak is in the same place. 90Hz is the F3 for the suggested closed box.

Does it make sense to simulate it this way? Just wondering....

I can do measurements 50cm instead of 2cm from the openings later today, right now somebody else is sleeping in this room and I can not measure with more SPL.

1688808505698.png

1688808661683.png


This simulation has a 150 2nd order LP filter added. I think this amp I'm using now has this fixed crossover point set, from what I have measured in other tests.

1688808389320.png



The drive is inverted. No reason other than building fast.

A bit of black foam is separating the back of the driver from the cardboard, hard to see in the photo.


1688808126323.png
1688808216000.png




Model NumberLW150-4
ColorBlack
Unit of MeasureEach
UPC848791001864
Warranty - Parts5 Years
Warranty - Labor5 Years
Product Shipping Weight (lbs.)0.8
Speaker TypeWoofer
Nominal Diameter6"
Power Handling (RMS)40 watts
Power Handling (max)80 watts
Continuous Program Power--
Impedance4 ohms
Sensitivity86.1 dB @ 2.83V/1m
Frequency Response60 - 1,800 Hz
Voice Coil Diameter31.8 mm
Magnet Weight--
DC Resistance (Re)3.6 ohms
Voice Coil Inductance (Le)0.86 mH @ 1 kHz
Resonant Frequency (Fs)62.6 Hz
Mechanical Q (Qms)6.01
Electromagnetic Q (Qes)0.72
Total Q (Qts)0.64
Diaphragm Mass Inc. Airload (Mms)21.9g
Moving Mass Of Diaphragm (Mmd)--
Mechanical Compliance of Suspension (Cms)0.3 mm/N
Surface Area Of Cone (Sd)91.6 cm²
Volume of Displacement (Vd)36.6 cm³
BL Product (BL)6.52 Tm
Compliance Equivalent Volume (Vas)3.49 liters
 
Last edited:
You cannot measure a Ripole at 2cm in front of the opening and get the "far field" response. Are you going to listen to the thing at 2cm away??? This problem is much worse than the related problem of measuring a driver in an e.g. closed box with the microphone very close to the dust cap - in that case you do not get the effect of the cabinet and its edges (diffraction and baffle step response) and so it is missing some key aspects that will appear in the response if/when you measure it farther away, meaning at least 3 times the baffle width. For any dipole, the front and rear radiation interact out in the room, and this will happen even at 50cm distance for your relatively small Ripole. This interaction will cause cancellation at low frequencies. Your 2cm measurement is not capturing this aspect of the far field response, and so I would expect that the bass below 100Hz will be much more attenuated than what your measurements above show.

The fact that your model using a bandpass is similar to the measurement is no coincidence. It's because you are not measuring the dipole, only one side of it due to the proximity of the mic to the opening.

I suggest you re-measure at a distance from the Ripole. But then you will start to get the room entering your measurements, which is the typical problem when attempting to measure indoors in a domestic space (in your home) and below 200-300Hz.
 
Member
Joined 2021
Paid Member
Thanks for the reply @CharlieLaub
The fact that your model using a bandpass is similar to the measurement is no coincidence. It's because you are not measuring the dipole, only one side of it due to the proximity of the mic to the opening.

Oh, I was very interested in the cone excursion simulation so this is still very useful and interesting! What I was hoping for.

I measured again for my desktop/room, not close from the wall, and ab.jpeg is with and without the prototype. The main drivers are FR 3.5" and the bass was all the way down, that's the best I could get.

In this setup the two video monitors I use might interact with the cancellations, the one above it is 32".

With REW the cardboard resonates a lot at low frequencies, I think it's too stressing for the driver. Time to build with wood.

What this suggests is that I might have better luck using the low profile buffers (two or three) in a video monitor stand to provide some bass with moderate power to each driver and get better suited drivers for the living room. Right?
 

Attachments

  • spectrogram.jpeg
    spectrogram.jpeg
    89.9 KB · Views: 42
  • spl.jpeg
    spl.jpeg
    96.3 KB · Views: 40
  • ab.jpg
    ab.jpg
    125.7 KB · Views: 39
Member
Joined 2021
Paid Member
I would like to test this one. Not really a Ripole but following the idea, if the tuning frequency for rear and front is the same and if you have the two buffers (would need to be opposite to each other), then it seems the phase is 180 deg apart. Thoughts?

1689019992859.png