Help needed : DIY speakers using philips 8inch drivers

[ark]

Hi,

Here is my first attempt to build a pair of speakers using Philips(Boston) driver - HQ48414 / 25W / 93dB. It also has a tweeter from Alpine



I need some help from experts. While I am happy with the rich mids and sweet highs the speaker produces, wondering if anything can be done to improve the low end response.

Can I convert this from a sealed enclosure to a front ported box to improve the low freq response. If so what should be the dia and length of the tube ?

Inside dimension of the box in cm is 21.5B/33D/38H. So I guess volume will be roughly 27L including space occupied by the driver. This was the biggest box I could build with the half sheet of ply I had hyeah:

By the way , initial testing was done with no sound proofing inside. My reference is an MA BR2 speaker

 

[t.antony]

Congrats on the build:clapping:.

I think you can successfully make it a good sounding ported enclosure. Use 2 inch diameter PVC pipe - the thin gray ones will be fine as they match the hole dimensions close to 2 inches. You might need a longish port - about 6 inches. Buy 2 feet of PVC tube and experiment with 4" 6" & 8" long port lengths. Position the port midway between the driver and the bottom plate.

Stuffing is required to clean up the mids. Dacron fill from a single pillow would be sufficient for stuffing both the enclosures.

 

[novice-akki]

Congrats on the build...

Crossover details please - I assume you are using a 02 way and 02nd order filter network ?

 

[ark]

Congrats on the build:clapping:.

I think you can successfully make it a good sounding ported enclosure. Use 2 inch diameter PVC pipe - the thin gray ones will be fine as they match the hole dimensions close to 2 inches. You might need a longish port - about 6 inches. Buy 2 feet of PVC tube and experiment with 4" 6" & 8" long port lengths. Position the port midway between the driver and the bottom plate.

Stuffing is required to clean up the mids. Dacron fill from a single pillow would be sufficient for stuffing both the enclosures.

Thanks Antony for the prompt response. I will try it this weekend.
Another challenge I have with experimentation is that, only the back side of the box is removable. Frequent opening makes the screw holes lose. Is it possible to get some kind of screw system that allows me frequent opening and closing ?. Also , how do I temporarily seal the back during the experimentation. Use some kind of rubber sealing ?

For stuffing, I have set my eyes on a pillow in my bed room. It will be operated upon once I get the porting sorted out.

Novice , I have not used any elaborate crossover arrangement. Currently it tweeter is connected in parallel with the Woofer through a 3.3 uf cap. I will try to do something more interesting in my next project . At the moment , I am looking to source good drivers for a 2.5 way system.

 

[t.antony]

... how do I temporarily seal the back during the experimentation. Use some kind of rubber sealing ?

I use 3" wide paper masking tape - the type used by carpenters to temporarily hold laminates in place. Two layers would be sufficient to seal any air leaks

 

[ark]

I use 3" wide paper masking tape - the type used by carpenters to temporarily hold laminates in place. Two layers would be sufficient to seal any air leaks

Got it ....Thanks a lot.

 

[quad]

. Frequent opening makes the screw holes lose. Is it possible to get some kind of screw system that allows me frequent opening and closing ?.

Look around for threaded inserts (also called D-type nuts).

Amazon.com: E-Z LOK Threaded Insert For Soft Wood, 1/4-20 Int Thread - 13mm length - Flanged- Zinc Die Cast (Pack of 100): Industrial & Scientific

I used M5 size D-type nuts, which are available here in Hyd. They are
perfect for this application. For sealing the gap, you can make a gasket
with closed cell foam and use rubber glue.

 

[ark]

Look around for threaded inserts (also called D-type nuts).

For sealing the gap, you can make a gasket
with closed cell foam and use rubber glue.

This is exactly what I was looking for, Thanks for the info quad. I just finished the project yesterday. Will use this idea for the next project.

Here is how the box looks, with 2 inch pvc pipe inside. I did not spend a lot of time in giving it a good finish. Just painted it. This will be mainly used for testing my DIY amp projects.

View attachment 3785

There is a marked improved in low end response now. Not a lot of punchy bass, but decent enough. I connected it to the TV yesterday and it was sounding very nice . Pretty happy with the outcome.

 

[t.antony]

Good to know it worked out well, how long was the port?

BTW that picture link seems to be broken.

 

[ark]

Dont know what happened to the picture. Hope it works this time.


Port length used is about 7.5 inches. The 2 inch hole was slightly bigger than the pipe. Used masking tape to wrap around the tube to make a tight fit . Also applied a lot of fevibond ( rubber adhesive) before forcing it in. The same thing was applied to all the joints with a hope that it will seal and create an airtight box. Looks like it worked. I still need to paint the ports.

My research for the next project is on !Thinking of a proper Floor standing 3 way system using MDF. Currently spending a lot of time to understand speaker design and a good set of drivers within a budget of 500 USD.