Jump to content

No name Speaker upgrade:


Batty
 Share

Recommended Posts

Some time ago I was given a pair of 'Dimension' speakers, I can't say I had heard of them before and Google showed up little.

 

It turns out that the mids and tweeters were blown in both boxes.

I thought that I could 'fix them up a bit' for my son to use with the PMA250 I had given him last year.

 

The before picture....

post-109729-0-71342600-1359153543_thumb.

2 x 8" bass drivers

1 x 4" mid range

1 x 2" tweeter.

 

I've had a rummage around and found a pair of Audax 2" drivers and I still have the 5" drivers from my Castles one of which has a rattle around 20Hz.

I can use the Castle drivers as they won't be doing bass duties.

 

post-109729-0-30509800-1359153792_thumb.post-109729-0-85711300-1359153812_thumb.

 

Here is a comparison of the mids.

post-109729-0-69099400-1359153853_thumb.post-109729-0-47725900-1359153914_thumb.

 

Progress so far

post-109729-0-67183100-1359153884_thumb.

 

I don't have anything to replace the bass drivers with and there seems to be no bracing or acoustic padding in the boxes, I need to replace the spring type connectors on the rear too and maybe replace the internal wiring with something a bit more substantial.

 

First I'll just put one together and see if it's worth any extra effort.

 

Thanks for reading about what is my first speaker project.

Edited by Batty
Link to comment
Share on other sites

While driver replacement in high-end speakers needs a lot of close matching, at the price of this whole job that is clearly not necessary.

 

Have fun. I hope it works out for both you and your son. There's little better than addicting others to this crazy hi-fi stuff.

 

Greg

Link to comment
Share on other sites

The Audax doesn't seem to go high enough, I tried a 3/4" soft dome and it sounds so much nicer, but I only have 1.

Using the Castle mid gives vocals and guitars a nice tone, bass as expected is a bit flabby and top end a bit stunted, but otherwise not bad for a bitsa build.

Edited by Batty
Link to comment
Share on other sites

OK it seems that the full bass signal is being directed to the mids, so I'm going to need a crossover or filter to stop frequencies below 300Hz getting to it, anyone have a cct or some values of C and L I can use?

Link to comment
Share on other sites

G'day Batty,

 

The high pass will consist of capacitors, at that frequency it could be around 60-70 uF (first order), assuming 8 ohms impedance at that frequency, using non polarised caps.

 

BTW, do you still need drivers?

 

Regards,

 

SB

Edited by Sub Sonic
Link to comment
Share on other sites

There is no real crossover to speak of, just some caps in line with the mid and tweeter.  I think the cap in line with one of the tweeters was stuffed as there was no output so I connected direct and got sound it was 22uF.  Sounding not too bad atm, we'll see what Daza thinks when he gets home, thanks for the offer of drivers, I may PM you if I get stuck.

Link to comment
Share on other sites

Daza is happy showed him that if he boosts the bass the mid rattles, he's cool with that, he also has a denon equaliser so is tailoring the curve to reduce the rattle.

Link to comment
Share on other sites

That actually is a crossover. A cap just applies a first order high pass. Inductors are the expensive components, so to exclude those and save cost they make it a 3 way using a mini fullranger instead of a tweeter. That way it can handle the extra bottom end.

 

You can use an online calculator to give you a quick guess at cap values, but it's very hit and miss. You actually need to measure before you will find out what the cap needs to do. Probably a lot more effort than you had in mind. Just keep in mind that you are looking at a wild guess here.

Link to comment
Share on other sites

Just going by the original fit, the mid needs a cap in line to stop LF getting to it 300 Hz or even 450Hz anywhere in between is good I want to stop the rattle caused by low frequencies.

 

I know I should just replace the driver but I would need 2 and they are a good sounding driver.

Edited by Batty
Link to comment
Share on other sites

You should probably build a mini enclosure for the mid and fill it with stuffing. This will avoid the cone moving from the bass pressure in the box and it will also protect the driver and limit excursion. It will probably give you a bit of a hump like a closed back driver, which could want a slightly higher crossover point so your filter starts attenuating before the hump.

Link to comment
Share on other sites

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.




×
×
  • Create New...
To Top