Disappointing first build w/ W3-871C W3-926SD

[patrickm]

You may want to remove some material from the back of the baffle to make sure the driver can breathe freely. Maybe chamfer or rabbet it to keep the thickness about 8-10mm near the driver, if you haven't already done so.

[Alvis]

I think you are asking too much from a 3" speaker, no matter what brand.

They gave some advice to band-aid the situation, but I don't think it will ever sound like you expect.

Would make a decent computer setup though.

[Moon Track]

Originally Posted by lost eden

So what's my best option? Should I be considering permanently filling one of the ports in addition to adding stuffing?

Dampening by polyfill works worse for lower frequencies.
As a side note, the strength of this resonance depends on ratio between box and port size.

Leave only one slot, and reduce the length in two times. It will be 11 cm2 port.

Modeled in Unibox program for Fb 85hz ,the 15cm long port with 11cm2 internal area gives air velocity 18m/s at 12watt and first port resonance at 1150Hz.

Further, you can insert thin pad, 2-3cm from polyfill, at a distance of 1/3 of port lenght, it will help to split the main resonance and to redirect part of energy into it’s harmonics.

[ODougbo]

Back to post 10, I think you got way off track with the huge port(s) idea, my guess is that sound is just pouring out of them, canceling out the sound from the front.

This is an interesting build using the same speaker:

www.vikash.info/audio/W3-871S/build.asp

[lost eden]

Originally Posted by Moon Track

Dampening by polyfill works worse for lower frequencies.
As a side note, the strength of this resonance depends on ratio between box and port size.

Leave only one slot, and reduce the length in two times. It will be 11 cm2 port.

Modeled in Unibox program for Fb 85hz ,the 15cm long port with 11cm2 internal area gives air velocity 18m/s at 12watt and first port resonance at 1150Hz.

Further, you can insert thin pad, 2-3cm from polyfill, at a distance of 1/3 of port lenght, it will help to split the main resonance and to redirect part of energy into it’s harmonics.

I'll have a think how I can do that. As it's all glued together apart from the one side making alterations to the ports won't be easy, but I should be able to Dremel the one on the open side.

Back to post 10, I think you got way off track with the huge port(s) idea, my guess is that sound is just pouring out of them, canceling out the sound from the front.

I followed the dimensions from WinISD, but as I said I couldn't know whether WinISD was leading me astray...

This is an interesting build using the same speaker:

Construction of W3-871S monitors from plywood

I saw that & several others like it when I was coming up with my original design, but when I put them into WinISD the frequency response was dreadful! Vikash's cabinets are roughly 2.8l, which is the same as mine if I completely filled the ports, but the plot from WinISD is attached for this & (to my unexperienced eyes at least) is useless!

[chris661]

Okay, it looks to me like...

- you need a baffle step filter - when the driver goes from "seeing" the baffle to not seeing the baffle, it loses an amount of energy as the sound wraps around the cabinet. At higher frequencies, the driver is effectively in half-space, at LF, its in full space. Out in a field, this transition will lose 6dB. In the home, 4dB seems more common. There are online calculators that will help you calculate the components needed.

- that cabinet isn't going to work as simulated - high aspect ratio ports with sharp folds aren't going to allow airflow so easily, reducing bass output compared to what winISD said.

- you may well be expecting too much from a small driver - comparing them to a larger 2-way and expecting them to do what the 2-ways do with bass and treble isn't fair: FR drivers are generally about the midrange.

- you need to let them bed in (as others have said).
Here's how I do it...
Download a bass-heavy track. Bass I Love You, 15 Step by Radiohead, whatever. Something to get the cones moving.
Put the cabinets face to face and wire one backwards. That way, the sound cancels out, so you're not disturbed so much (add a blanket over them if there's still noise getting out). Play the bassy track through on repeat, set off so you can just about see the cones moving, leave it a couple of hours, then have another listen. Turn it up so they're moving a few mm peak to peak, leave for a couple of hours, listen again. Take them up to rated Xmax (not recommended for Mark Audio stuff: the rated Xmax is way beyond what they should be driven to, due to the fragile cones), leave for a few hours, listen again.
Repeat the last stage a few times over for good measure.
By that time, they should be somewhere near their final operating condition.

Hope this helps.

Chris

PS - where abouts in the UK are you?

[ODougbo]

I didn’t see that being a fair comparison either (it’s not that easy). The Mission 732 appears to have to good reviews, a bigger woofer and a tweeter for highs.

As far as what do now, I would try to improve on a previous design, e.g. a 2.8L triangle box, try to make the front small as possible.

btw, I'm really happy with a recent FR Fostex build using these:

Fostex FF125WK 5" Full Range: Madisound Speaker Store


[QUOTE=chris661;2996011]

- you may well be expecting too much from a small driver - comparing them to a larger 2-way and expecting them to do what the 2-ways do with bass and treble isn't fair: FR drivers are generally about the midrange.

QUOTE]

[profring]

i think the driver with the phase plug not sited properly...

[Bjohannesen]

Hi Lost Eden, the 26 lenth of the port, is that including the fold ? What is the hight and depth of the box the port not includet?
In other words, I would like alle the internal dimesions and fire up MJK´s excelent simulation models.

In the meantime, please take a look at my foldet version of TABAQ. As you can see, the volume is much larhes than yoru design.

Hi from
Bjorn J

[mondogenerator]

Im mid progress in something similar myself. I would just re-iterate what others have said, the points that i agree with.

Ports= too big cross sectional area and/or too long and/or the bend doesnt help much.

ALso, It may have even been better sounding with a rear firing port, identical to the one you have now.POSSIBLY a fairly easy mod.

I have a 2" round port on a pair of 5"ers in 17litre cabs. one has a rear port the other on the front. Even with the port spaced some 8" away, the front ported box radiates more midrange hash from the inside of the cab.

Also, I reckon the port is too close to the driver itself. As others said, there will be cancellation. the large this distance is, the better for eliminating cancellation.

I seem to recall reading a 'rule of thumb' of minimum 3" between driver and port, although that maybe have been in reference to the 'inside' end and its proximity to rear walls, the rear of the driver etc.

Hence why the rear firing port works well, but is difficult on a micro speaker. Maybe you could reduce the area of the port, but then without also shortening it, the tuning will be even lower, and bass weaker. With these drivers (I have the W3-1285sg) Ive used a small port, and given the low relative SPLs I would suggest that even a 'simple port' ie a hole, would work, IF the volume required for a port area of maybe 100mm² or so, wasnt too large.

RUN IN

Run in time is definitely a big factor with these drivers, BUT theyre never going to shake the windows. The change in the driver Vas and Qts MAY work in your favour, however small it may be. I dont understand why MA drivers are so cautious about the run in. Yes theyre fragile cones, but does it mean I can NEVER let them get up to 1mm pk-pk movement for fear of damaging? speakers that you ruin by LISTENIng to them.....paradoxical indeed.