As many of you know, I am in the process of renovating an old house I bought. It's enough to drive anyone absolutely crazy. Too much work, limited cash-flow, dealing with frustrating contractors, one thing after the other breaking, etc, etc.
Anyway, in order to keep myself from going absolutely insane I have been working on this set of speakers for the past couple of weeks. I only do a bit here and there when I have a break or when I need to "take a chill pill" from the renovations.
The cabinets are nearly done - probably another week or two worth of work left on them. After that I will start crossover development as time permits.
Cabinet construction & materials:
The cabinets are made out of 18mm marine plywood, and has 5mm thick natural bamboo over that. The baffle is around 40mm thick. To say that this cabinet is solid is an understatement. It's super strong. To make it a bit more interesting looking, I did some Walnut inlay on the baffle and top as you can see from the pic above.
The cabinet will have a grille (I don't often do those - too boring) which will cover the recessed black part of the baffle.
The port is on the back - standard 44mm type with a flare.
I had to cut my own binding posts as I could not find any with a long enough thread. I needed 65 - 70mm long thread to pass through the back board as well as the internal divider. The posts will only accept banana plugs - I wasn't in the mood to sit on the lathe for hours making 5 way jobs, so the simplistic route works well.
Cabinet type:
Cabinet type is mass loaded tapered quarter wave tube (ML-TQWT). My frist time doing a ML-TQWT. I have built plenty bass reflex and TQWT, but never a combination of the two as this is. Can't wait to hear how this type of enclosure sounds! I did some simulations and came up with a ratio of around 3.6 : SD. I don't have any software to accurately model a ML-TQWT, so I modeled both a bass reflex and TQWT and did a best guess as to how these will combine. Time will tell whether this worked out well or not.
Also, I did a bit of trickery inside the cabinet. I have a magnet brace directly behind the Eton. When the driver is mounted, this brace is flush against the back of the magnet, thereby bracing the driver frame.
Drivers:
Eton 5-200 Symphony A8 - http://www.madisoundspeakerstore.com/approx-5-woofers/eton-5-200/a8-symphony-5-mid/bass/
Seas Excel T25CF001 (E0006) tweeter - http://www.madisoundspeakerstore.com/seas-soft-dome-tweeters/seas-excel-t25cf-001-e0006-tweeter/
Crossover considerations:
If you take a look at the published transfer function of the Eton you will notice the nice slow role-off it has starting at about 2.2 kHz. Other than a minor bump (cone breakup or something) at 6.5 kHz it looks pretty good for use with a 1st order filter. Obviously my own measurements will need to be taken to check whether this is the case or not.
Why is the mid/bass above the tweeter?
The cabinets are not very tall at around 850mm. Because of this, you need to make a plan to get the tweeter to near ear level. One way is to make a slanted baffle, but I don't always like the look of those and I don't think it will look too good on a small speaker. The second option is to put the tweeter below the mid/bass. This has a similar effect as slanting the baffle because of the induced angle, and also allows for a similar path length between your ear and both drivers. Ever heard of time-aligned drivers? This configuration in a short speaker approximates the same.
That's it for now - more when I have time to do some more work on them.
Cheers,
Ian.
Anyway, in order to keep myself from going absolutely insane I have been working on this set of speakers for the past couple of weeks. I only do a bit here and there when I have a break or when I need to "take a chill pill" from the renovations.
The cabinets are nearly done - probably another week or two worth of work left on them. After that I will start crossover development as time permits.
Cabinet construction & materials:
The cabinets are made out of 18mm marine plywood, and has 5mm thick natural bamboo over that. The baffle is around 40mm thick. To say that this cabinet is solid is an understatement. It's super strong. To make it a bit more interesting looking, I did some Walnut inlay on the baffle and top as you can see from the pic above.
The cabinet will have a grille (I don't often do those - too boring) which will cover the recessed black part of the baffle.
The port is on the back - standard 44mm type with a flare.
I had to cut my own binding posts as I could not find any with a long enough thread. I needed 65 - 70mm long thread to pass through the back board as well as the internal divider. The posts will only accept banana plugs - I wasn't in the mood to sit on the lathe for hours making 5 way jobs, so the simplistic route works well.
Cabinet type:
Cabinet type is mass loaded tapered quarter wave tube (ML-TQWT). My frist time doing a ML-TQWT. I have built plenty bass reflex and TQWT, but never a combination of the two as this is. Can't wait to hear how this type of enclosure sounds! I did some simulations and came up with a ratio of around 3.6 : SD. I don't have any software to accurately model a ML-TQWT, so I modeled both a bass reflex and TQWT and did a best guess as to how these will combine. Time will tell whether this worked out well or not.
Also, I did a bit of trickery inside the cabinet. I have a magnet brace directly behind the Eton. When the driver is mounted, this brace is flush against the back of the magnet, thereby bracing the driver frame.
Drivers:
Eton 5-200 Symphony A8 - http://www.madisoundspeakerstore.com/approx-5-woofers/eton-5-200/a8-symphony-5-mid/bass/
Seas Excel T25CF001 (E0006) tweeter - http://www.madisoundspeakerstore.com/seas-soft-dome-tweeters/seas-excel-t25cf-001-e0006-tweeter/
Crossover considerations:
If you take a look at the published transfer function of the Eton you will notice the nice slow role-off it has starting at about 2.2 kHz. Other than a minor bump (cone breakup or something) at 6.5 kHz it looks pretty good for use with a 1st order filter. Obviously my own measurements will need to be taken to check whether this is the case or not.
Why is the mid/bass above the tweeter?
The cabinets are not very tall at around 850mm. Because of this, you need to make a plan to get the tweeter to near ear level. One way is to make a slanted baffle, but I don't always like the look of those and I don't think it will look too good on a small speaker. The second option is to put the tweeter below the mid/bass. This has a similar effect as slanting the baffle because of the induced angle, and also allows for a similar path length between your ear and both drivers. Ever heard of time-aligned drivers? This configuration in a short speaker approximates the same.
That's it for now - more when I have time to do some more work on them.
Cheers,
Ian.
