On 12/07/2022 at 8:52 PM, andyr said:

Shirley, bitumen paint damps the lightweight cabinet structure - it doesn't actually stiffen it?

 

Coming back to this question. It depends on what you mean by damp? I want to make sure we're on the same page.

 

Ok, I am *almost* done with this project, and I will be retaining them in the home theatre.  

 

There is one more item.  How will I treat the wooden boxes themselves?  The hint of a resonant thump.

 

The resonation is caused by internal pressure, causing the wooden walls to flex.  And that flexing causes a coloration.

 

There are different ways to treat that.

 

We can line the walls with wool or acoustic foam, absorbing the pressure, reducing the impact of the internal soundwaves inside the cab.  It's a common approach.  This can be considered dampening (dampening the soundwaves/pressure through absorption).

 

I mentioned, I previously used some bitumen paint on a pair of Aarons. 

Thread here:

 

The bitumen paint doesnt actually absorb.  If it does, it's really minor.  The surface ends up with a rubbery type feel to it.  What the bitumen paint did, was add weight and density, to the thin cabinets, making them more inert.  So that additional density, reduces the propensity for the walls to resonate.  And why I describe the bitumen as stiffening up the boxes.   We could say, it is dampening the resonation, but it is a different way to dealing with the issue (i.e. different to using an absorption layer).  So I describe it as stiffening (or strengthening),  as opposed to dampening.

 

I could do both, bitumen plus foam for example.  But I chose not to, with the Aarons.   The bitumen was enough, to help reduce the resonation.    For ported boxes, I also question if adding absorption materials, plays a role in affecting the porting?   Not sure. 🤔

 

I think our speaker cabinets have a role to play in the warmth of the sound.  I dont think they're supposed to be 100% completely inert.  We could make speakers out of concrete boxes, but i doubt it'll sound better?

 

Anyway, I can certainly experiment with these boxes.   When I look at the cabinet materials of these, and feel the weight, they do remind me of the Aarons.

 

I think I will try the wool first, with small amounts of double sided tape.  Because, I have some on hand, and it is easy enough to remove it, if I am not happy.

 

The video that suggests vinyl tiles plus acoustic foam,  the vinyl tiles are doing a similar job to the bitumen paint, I think.  And I'd probably use the bitumen as a preference (I have some on hand). 

 

 Bitumen paint is good, it doesnt kill the warmth, it just tames the resonance.   The only issue with it, it is a slow process, of painting on one layer at a time, and it bloody stinks. Takes freakin ages for the smell to dissipate.

Edited July 23, 20223 yr by Sentient

Ok, so have re-opened the box with the 10" driver.

 

There is a cross brace.  And there is 1 light layer of foam covering most of the back wall.    (I also use 18g copper wire, for the bigger drivers, rather than 23g in the tweeter+mid box).

 

The 2nd photo shows the port.

 

 

Edited July 23, 20223 yr by Sentient

I'm going to try this stuff first, because i have it on hand.

 

It's about 1cm thick.

 

And do just the side walls, leaving the light weight foam where it is on the rear wall,,, and leave the top/bottom without any treatment (to begin with).

 

 

Edited July 23, 20223 yr by Sentient

Although not a new idea, I am a huge fan of this speaker arrangement, it entices me to build something

ok, 10" bottom boxes lined with the wool.

 

sounds good.

 

will do the top boxes with the 8" midbass drivers another day.

Anyone try this stuff before,  inside their speaker cabinets?

 

Sound Deadener foam (ebay link)

 

I've ordered some, to compare it to the wool.

Edited July 23, 20223 yr by Sentient

The sound deadener foam has arrived.

 

It's thick and really easy to work with.  The adhesive back applies easily.  

 

Have left the old cheapy foam on the back wall, but I am still grappling with that decision.  🤔

 

Have decided to remove the old passive crossover components.

 

Edited August 1, 20223 yr by Sentient

So,,, I received 9 sheets of 30x50cm.

 

I used it all, on the 2 top boxes, with the 8" woofers.   

 

Seems to work well, so I've ordered 18 more sheets.  

Update: the black foam sound deadener, works really well.

 

The cabinet resonance I was hearing is gone.  The bass is warm and fast. 

 

Overall, the sound is very nice.

 

Much easier than painting multiple layers of bitumen paint, and probably more effective.

 

This project is now complete.  The speakers have been moved to their final destination.  Picture coming soon.

in place,,,,

with the grills off

they've turned out better than I'd hoped.

 

4 way active implementation on the mains.

 

2 matched rotel amps driving them:

RB-971 2ch power amp on the 10" drivers

RB-976 6ch power amp, driving the rest.

So,,,  with the success of this last active conversion project.

 

I felt compelled to have another crack. 

 

Another set of chinese speakers, but a very different design.   Pic attached.

In this 3 way system, is a 10" woofer, a large dome mid driver, and dome tweeter.

 

HiVi brand, my googling shows me there is information online about them, and they can be sourced online. 😎

 

Here they are removed from the speaker.

 

Edited August 29, 20223 yr by Sentient

The speakers had bi-wire terminals.

 

But, when I looked inside, those terminals were internally bridged.  🤦‍♂️

 

The cabinets are really freakin heavy, solid wood.  i need to weigh them, but here are some pics.

 

The front baffle is 4cm thick, and rear is 2cm.   It doesnt appear to be thick particle board, it looks like wood, multiple layers of it on the front baffle.

Edited August 29, 20223 yr by Sentient

Here are the (removed) crossovers, also using the Hivi brand caps.

 

Edited August 29, 20223 yr by Sentient

the cabinets had wool, shoved inside, just sitting loose.

 

The bottom port, is housed in it's own section, and sound waves travel down an internal cavity at the rear of the cabinet, down to the port.  This cavity was blocked by the wool, I couldnt see how the port was actually functioning like that.

 

So I used my double sided tape to secure the wool to the walls, and I cut the wool back, to open up that passage/cavity to the port.

 

 

Edited August 29, 20223 yr by Sentient

have added a 3rd pair of speaker posts to the rear plate, and direct wired copper to each driver.

 

the mid dome driver, has an impressively wide band,  measures flat from 400 to 6k.

 

after listening tests, I've settled on crossover points of 600 and 4k.

 

Am using 1 x swamp active electronic crossover (stereo 3 way) for my testing.

They look like VERY substantial speakers- boxes AND drivers.

Another active conversion, Sentient?

If so, what amps are you planning to use?

Also, given that you are inside and fiddling with there gubbins, have you ever tried avoiding the speaker terminals altogether and literally direct-driving the speakers? Just an idle wondering thought.

All the best, and thanks for the detailed thread.

36 minutes ago, ICUToo said:

If so, what amps are you planning to use?

 

In terms of final configuration, I dont know yet.   I'm just using temporary amps, while I test.   Will keep you posted.

 

36 minutes ago, ICUToo said:

Also, given that you are inside and fiddling with there gubbins, have you ever tried avoiding the speaker terminals altogether and literally direct-driving the speakers? Just an idle wondering thought.

All the best, and thanks for the detailed thread.

 

No I havent tried that, good suggestion.  I really love the aesthetics of these boxes.  They have a gorgeous wood grain finish, with smooth curved baffle.  I see them in my bedroom, oogling them, as I fall asleep.  😍🤣

 

If my bedroom was their end destination, I could certainly try that !  

Edited August 29, 20223 yr by Sentient

Initial listening, is quite good.  The woofer is very capable, warm sounding, deep, vibrant, yet runs up to 600 without any obvious drama.   The mid dome, delivers very sweet sounding vocals too, quite an impressive driver, really.

 

 

Edited August 29, 20223 yr by Sentient

Weighed them, 33kg per speaker !!

Hey mate, nice one.

I'm wondering what make and model these are?

 

Ant.

 

Edit - sorry, I re read they are HiVi drivers, are the speakers made by them too?

Edited August 29, 20223 yr by BuzzzFuzzz

49 minutes ago, BuzzzFuzzz said:

Hey mate, nice one.

I'm wondering what make and model these are?

 

Ant.

 

Edit - sorry, I re read they are HiVi drivers, are the speakers made by them too?

 

Same chinese maker as the previous set of speakers, earlier in the thread- UK Audio Advanced.   Model- Reference Series 501