Something stirs in the Undergrowth

[vinylnvalves]

I think the oversized box and just fill it with stuff is the easiest. When I dismantled some speakers a few years back.. I remembered where I put all my university text books. I think Bruce Edgar recommended the water bottles. Plastic bags of rice etc is just as good. I just want to see the results of this Midbass horn this decade

[JamesD]

Rice is a good idea - I used whatever I had been using for blind baking such as rice, dried beans or seeds - sunflower seeds were popular, sugar bags or small clay granules all in bags... not sure of the compressibility factors of the different materials though... What sort of pressure differences are to be expected?

I had not come across the idea of water bottles before but I guess it is an incompressible fluid...it will compress but not by very much...

[IslandPink]

Thanks Ant - good point. I should get some loading from a cardboard box. I'm ahead of you on the water bottles, I did that already with the folded horn. Yes, maybe it was Bruce who suggested that ?

[izzy wizzy]

Well , after some more purchasing of bits ( filler, dremel cutting discs etc ) I finally got the mouth section tidy enough to fit to the rest. Yesterday was sound check #2. I must say this thing sort-of dominates the room -

The sound is good but not amazing. It has gained some extension into the bass, with the mouth added. It's a bit hard to evaluate without filtering, as there's a lot more out of band energy ( upper end ) than expected. You have to sort of tune that out when listening and concentrate on things like lower percussion and bass guitars. The mouth section is not rigid enough ( as expected ) it needs another layer of fibreglass, I'll do that inside - plus a brace from top to bottom.
The other thing I need to do its make a back volume for the driver. I think this bigger, longer horn will benefit from this more than ones I've done in the past. This could be a faff, I'm just thinking about how to do it - it'll be cylindrical, using the phase plug surround as the starting point.

I just used fibreglass for the first time on a gully betwixt house and garage so outside. None of the stuff is on me yet I stink of resin fumes. Can't imagine the smell if you did that inside. Will it permeate soft furnishings or does it die away after a while?

Anyway, hope this gains you the sound you're after.

[Ali Tait]

It'll die away.

[Ray P]

I just used fibreglass for the first time on a gully betwixt house and garage so outside. None of the stuff is on me yet I stink of resin fumes. Can't imagine the smell if you did that inside. Will it permeate soft furnishings or does it die away after a while?

Anyway, hope this gains you the sound you're after.

That's why I use epoxy resin whenever it's viable for the job.

[IslandPink]

Yes it was pretty bad in the house, especially when I did about 4 sessions in two days. I had the front sash window open a few inches and the back door likewise, some air flowing through - but I tended to escape and go out for a walk when it was at its worst. It does dissipate but can take a few days to completely go. The thing you've got to avoid is underestimating the catalyst - then it'll smell for weeks !
Epoxy would be nice but is twice the price of polyester resin.

[IslandPink]

Have done a bit of testing with the further reinforcements of the mouth.
It's not a lot better than before - which leads me to think that the back enclosure is going to be the key step, now.
I found part of an old back chamber from the first bass/mid horn - see picture, just planning how to modify that to use as the basis for something here. Will have time this weekend to get to work on that.

[IslandPink]

Curses !
I just soldered-up a 2nd-order low-pass filter from a 3.3mH choke and 22uF Ansar cap .
Got out the chip amp. Got the CD player , got a 1.5m speaker wire and an interconnect.
Keen to hear this without the upper mids and treble.
Connected everything up and switched on. No sound.
Preliminary investigations suggest the CD player is to blame - nothing coming out of the output sockets when checked with an AC voltmeter.
I suppose it is 17 years old ( Ah! Njoe Tjoeb 4000 )
It looks like the disc is spinning up, and I get the total length and track timer running when I press play.
Annoying.

[Nick]

Maybe the digi out is still working?

[IslandPink]

Good point, that is the way I've been using it in recent months, into your DAC.
Will check tomorrow.

[Toppsy]

Curses !
I just soldered-up a 2nd-order low-pass filter from a 3.3mH choke and 22uF Ansar cap .
Got out the chip amp. Got the CD player , got a 1.5m speaker wire and an interconnect.
Keen to hear this without the upper mids and treble.
Connected everything up and switched on. No sound.
Preliminary investigations suggest the CD player is to blame - nothing coming out of the output sockets when checked with an AC voltmeter.
I suppose it is 17 years old ( Ah! Njoe Tjoeb 4000 )
It looks like the disc is spinning up, and I get the total length and track timer running when I press play.
Annoying.

Mark,
I to have a AH! Njoe Tjoeb 4000 CDplayer and had a similar problem some years ago. I replaced the laser lens assembly optical pickup mechanism which is a readily available standard Philips VAM1201/11 or VAM1202 series type. The problem seems to be with track stress fracture on the flexible wiring strip. See photo below. You can just about see a crease in the long straight length of the flexi strip at the point where the tracks turn back on themselves. The inner most track on mine was broken. I am now on my second replacement unit. I use my CD player almost on a daily basis. The job is fiddly to do but I'm sure is well within your means to carry out yourself. Lets face it if I can can do it. Just be careful when removing and refitting the clear isolation mounts to the chassis mounting lugs. These can be easily torn and are like hens teeth to find replacements if you break one.

A few photos to help:







As can be seen I last bought a replacement from www.signalsuk.com in Birmingham but I don't think they are still trading.

[IslandPink]

Thanks for the info Colin. I have done a similar job on an Audio Note player - so I have some experience that should be useful.
I just need to do the check that Nick suggested , first. Might be worth getting one of those units though, in any case.

[Toppsy]

Mark,
you can just replace the laser lens pickup optical unit instead of the whole transport I posted. Avoids having to remove the whole unit and so avoid having to remove the isolation mounts which are difficult to disengage from the lugs without damaging them and they are irreplaceable or extremely difficult to find replacements. The other advantage is they are cheaper. Try here if the test Nick suggests works https://www.ebay.co.uk/itm/Laser-Lens-P ... SwsVVfeHKL. I might invest in one myself for safe keeping just in case.

[IslandPink]

It's working with the DAC. I'd better check the output stage valves, that could be the reason. ! I think they are 6922's, will see if I have any spares.
Thanks for extra info Colin, just crossing with my post.