Yet another boombox-type build. Hopefully somewhat different.

[roubi]

I'd then take two. There are ways to decrease cabinet size*, but they aren't really pretty. With a simply too small box it'll just sound pretty horrible....

* By adding a really large series capacitor. This is often done with those tiny subwoofers available in shops, like from brands like REL.

Hi V-bro, could you explain how this works? And how this allow to have a smaller cabinet? Or do you have any links about this?

Thank you.

[Saturnus]

The piezos I have chosen is Monacor MPT-001, I saw them recommended in the boominator thread on diyaudio, and figured they might be just as good with these speakers

I don't recommend those. They are just "the best of the worst" meaning of all the Motorola replicas these are the least bad.

I should note that I with the help of a few friends have taken contact to a chinese piezo tweeters manufacturer to remake the originally used bubble horn piezos which was of far better quality as they used a much larger piezo element and therefore went deeper in frequency (to about 3khz instead of 4.5khz) and without the initial 6dB peak at 5khz that both the Motorolas and replicas suffer from. They also had a better dispersion pattern as the horn is a true constant directivity type whereas the Motorola (and replicas) is a hybrid exponential.

Once sourcing and testing is complete they'll be sold at roughly the same price as the Monacor replicas although being vastly better quality (than even the original Motorola).

[V-bro]

Hi V-bro, could you explain how this works? And how this allow to have a smaller cabinet? Or do you have any links about this?

Thank you.

Only in Dutch, but it is an online calculator for GHP boxes.....
http://www.12vhifi.nl/closed.html

[roubi]

Only in Dutch, but it is an online calculator for GHP boxes.....
http://www.12vhifi.nl/closed.html

Hum, I don't speak dutch, but thanks to google translate...
I'll try to play a bit with it.
Is there an english name for this method?

Thanks.

[Saturnus]

Only in Dutch, but it is an online calculator for GHP boxes.....
http://www.12vhifi.nl/closed.html

Seeing that only Qts and Fs of the driver has effect on the series capacitor this could just as easily be done by reverse engineering the series capacitor cut-off frequency and calculating the input capacitor to the same cut-off value instead.

[V-bro]

Seeing that only Qts and Fs of the driver has effect on the series capacitor this could just as easily be done by reverse engineering the series capacitor cut-off frequency and calculating the input capacitor to the same cut-off value instead.

No, the inter action with the inductance is the key, it's a resonance network that extends the bass frequencies to a point beyond expected to be possible for the size. A very smart way to achieve this as it is pretty simple to apply.