Martello enclosure for FR88EX

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#21
Hi,

Well the datasheet for the driver is here http://www.solen.ca/pdf/fountek/fr88ex.pdf and it seems on paper to have quite a range.
I modeled my enclosure (attached) using an on-line calculator from here Loudspeaker enclosure calculating with Thiele Small parameter and I use a box Q that is lower than usual to account for my port design. I use an alignment between a sealed box and ideal ported box, based on a recommendation from Dave at planet10 (I've seen others who also prefer this alignment).
 

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#25
I am building a mini monitor with a FR88EX with allmost have the exact same inner cubic cm^3 (of ft^3 🙂) and would like to use a BR as well. I calculated that 2.6cm radius 10-11 cm would be "great" considering the size.

An externally hosted image should be here but it was not working when we last tested it.


I have two issues;
Will putting the BR port in the back create problems?
I would like the enclosure to be as "clean" as possible. If I would glue the front, implementing a filter would be hard. What filter have you tried?
 
#26
Hi SuperRRRRR !! By looking at the image seems that :1) the box is deep about 10 cm ,so how would a duct fit either way (front or back )😕
So putting it on the bottom would be the natural solution ,providing 3 spikes that lift the box at about 2cm.
2)a little sound deadening material inside should (could) be used
3) A filter is not what is needed with a single driver box . Some equalization is possible (usually a coil+Resistor paralleled,in series with the driver)
 
#27
You seem to have great "depth-estimation-from-a-photo"! The inner dimensions are 112 mm width* 224 mm height * 92 mm depth.
I might use an elbow for the port or just bend a piece of steel/aluminium pipe. The other option would be using a bit smaller pipe 1.8cm radius which would lead to +/-5 cm length, but would increase airspeed to +/-18m/s.
Damping"wool" is not on the photo, but I have some available.
 
#28
Yes I do ! Metric and eyesight have occupied most part of my life 😛
Elbow duct ? No good ; it adds losses (whatever they might be 😕)
I would not go ending with that little hole that we usually see in plastic-cast low class PC speakers .
A port on the bottom seems the best way ,far better than in the front ,when it is not well executed ,brings to the "mix" all the nasty inside-box medium -frequency resonances ....
BTW Gareth's speakers are nice !
 
#29
There's a lot of mystique around ports. I think a straight round pipe is going to let the most high freq out of the port - maybe lining the box with felt reduces the amount that reflects around and out of the pipe. A rear firing port should help reduce the amount of hf that finds its way back to the listening position but it could introduce placement issues (e.g. distance to wall). I think downward firing is the best option and it was the first option I considered - I abandoned it only to make construction easier.

The front slot port I've used doesn't seem to allow hf to escape, the bend at the throat of the port helps with this as does the restricted opening to the port (it's an expanding prism shape).
 
#35
Cardboard Martello

Well, I've decided to put my little fountek drivers to use thanks to this great thread. I live in an apartment and have no woodworking skills whatsoever, even making open baffles is a big hassle. Working with cardboard, however, shouldn't be a problem. The 'build' is stalled for the moment because I can't seem to locate my glue gun, but I will post pictures as things progress.

A couple of questions:

Is felt lining sufficient or does this speaker also require stuffing?

I'm considering adding the Aurasound 3/4" Titanium Dome Tweeter.
Think it's worth it? I have some 2.2uf caps and .15mh inductors,
which I could probably wire up as a first order crossover. If anyone
has thoughts on whether or not that would work, I would appreciate
it.
 

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#39
Flat Pack

This will be interesting to see, there was a company a couple of years ago that did a set of cardboard speakers for computer enthusiasts that folded up so they could be carried. Though i believe they were based on a planar design.

You could double up on cardboard in places leaving an air gap in between to improve the properties, even better you could corrugate thin card board in the gap to break up the sound. Or if you have some cotton wool insulate the gap with that.

I can't wait to see hows these turn out.

You never know iKea will be selling them next 🙂
 
#40
mules

Greetings!

There is nothing wrong with using cardboard for starting purposes. Open baffle mules have been made out of cardboard for years.

I'm not sure I would recommend it for permanent install, but for just layout, experimentation, and such it works great.
 
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