DIY Boston Acoustics Full Range Speaker

[shaan]

A little petrol and the dust cap came out like feather from water. But I did not expect a copper shorting plate!! diyaudiocart should mention this in the product description.

 

[maxsumit]

What is the issue with copper shorting plate ? Plz explain.

 

[greenhorn]

It's a good thing
Explaination provided here
Philips 9710 disassembling

 

[goldyrathore]

But I did not expect a copper shorting plate!!

Many of the drivers available locally are quite good for DIY projects. Often DIYers think that putting a system with Boutique drivers is going to get them a good system. The reality is far from it. The local drivers if used 'properly' will give the most bang for the buck.

I ve measured quite a few OEM drivers and found them to be very consistent in T/S parameters as well as frequency response.

This 8" driver seems a good one, no doubt its been around for a long time.
BTW, do you think the driver lacks any highs? I am contemplating a project with this driver.

 

[shaan]

What is the issue with copper shorting plate ? Plz explain.

There is no issue with it. It is actually a great little trick to minimize driver distortion when voice coil is attempting to leave the strong magnetic gap of the pole piece. Any flux generated by the coil outside the gap, that didn't interact with the pole piece, will be absorbed by the plate and cone movement will be damped. No wonder these drivers sound so good for their price (for which I did not expect the copper plate, but looks like they know what they're doing)!

Many of the drivers available locally are quite good for DIY projects. Often DIYers think that putting a system with Boutique drivers is going to get them a good system. The reality is far from it. The local drivers if used 'properly' will give the most bang for the buck.

Agree.

This 8" driver seems a good one, no doubt its been around for a long time.
BTW, do you think the driver lacks any highs? I am contemplating a project with this driver.

These have enough output at HF that no tweeter is needed. However, as I mentioned earlier, there is this peak at 11-12KHz and also a very noticeable HF beaming above 8KHz or so. meaning a phase plug is almost essential.

Yesterday I experimented with one of them and a diy plastic phase plug made from a chisel handle. The response with the phase plug was clearly discernible, no "shout"/peak and a very smooth and well spread high frequency dispersion, almost a point source. I loved the changes that happened. Today evening I will contact my carpenter and will try to convince him to make a pair 23mm diameter 50mm long plugs, he is a little shy about these stuffs. :lol:

 

[sudhirbhosale]

Thanks, the sound is melodious as intended for listening music.
As usual, the highs are little shouty, which I tamed by putting some wool around the whizzer cone.
Bass is well defined.

Hi maxsumit
I have 8" Boston acoustic drivers HQ48414P. But when I connected and out in smimple box, could not get good base. Any special requirement needed to get good base ? or it has frq limitation toward side?

 

[shaan]

Hi Sudhir.

These drivers are anemic below 100Hz by design. With a huge back-loaded horn like the one shown below you may expect a flat response up-to 40Hz. But you will also need a huge listening room.

 

[maxsumit]

I totally agree with Shaan. I also first made a OB speaker, and then a simple box speaker...wherein the bass response was not that good.
But in my last designed box with internal horn shape, the bass response was substantially improved.

Shaan, waiting for your update on phase plugs.

 

[shaan]

The carpenter turned out to be too shy to attempt turning some wood so I decided to turn it myself and after a couple hours made one. Here is a pic showing the last ugly one and the current marginally better looking one .

Will make another tomorrow and will do some listening on Sunday. Among the ones I have, the octagonal shaped drivers have much better placing of the whizzer cone. So will do the final mod on them.

 

[jls001]

Nice and shiny Great job, Shaan!

 

[Udit99]

they look amazing great job

 

[raj12345]

Amazing Job..

 

[Hari Iyer]

This is how my Phase Plug looks on the Fostex FR driver

https://screenshot.net/mor5zi9

I salvaged them from my daughters skipping rope handles and she is annoyed about that even today.

 

[shaan]

Placed the first plug with superglue and looks not that bad.

Unfortunately screwed up the second wooden plug and gonna have to turn one again next weekend. The nylon plug I previously made works pretty well but stands out so much on the driver that it looks ugly. So not gonna use it.

 

[Hari Iyer]

Why do you need to glue it. I just added a nut+ bolt and the phase plug just get stuck to the magnet.

 

[shaan]

Why do you need to glue it. I just added a nut+ bolt and the phase plug just get stuck to the magnet.

Yea I thought of that and is a common practice but felt like stealing out some of the field lines. Call me paranoid. :lol:

 

[maxsumit]

Hi,

I am hoping to buy a used (fairly new) pair of Audio Nirvana Super Ferrite 8 inch speakers for Rs 18000 /-

What do you guys think ? Is the price right and should I buy them at this price.

Please share your opinions here.

Thanks.

 

[maxsumit]

I have got these phase plugs from kebab skewers. Got to cut them, stain and finish them.

Trial fitting of phase plugs after cutting to size.

 

[shaan]

Cool.

Do tell us about the changes in sonics.

 

[keith_correa]

Why don't you guys use candelabra bulbs for phase plugs? They're slick!