low level fullrange?

[GM]

Call me old fashioned, but it sounds like the 6.5" inexpensive PA [ceiling] drivers like was stuck in the bottom front of large RPTVs would be ideal. Just fab a baffle and open up the rear of the cabinet, add a little damping to 'taste' and pocket a sizable chunk of the budget.

GM

 

[chrisb]

Call me old fashioned, but it sounds like the 6.5" inexpensive PA [ceiling] drivers like was stuck in the bottom front of large RPTVs would be ideal. Just fab a baffle and open up the rear of the cabinet, add a little damping to 'taste' and pocket a sizable chunk of the budget.

GM

OK, so what that you're old fashioned


provided that the cabinet can be purposed for this task, it'd certainly work - reminiscent of and old 50 & 60's stereo console

actually the first "hi fi" component to which I was exposed in 1959, and which served us three kids throughout the early Beatles et al era was a mono floor standing record player - about the only detail I can remember was the changer was a Dual

takes me back to the innocent years - thanks, Greg

 

[planet10]

Hi Dave, I'm starting to like the sound of these and the price is certainly right
Are you thinking a simple 1" front port or slotting like you have on your designs?

http://p10hifi.net/tlinespeakers/FAL/downloads/VarKalEL-191111.pdf

dave

 

[Lostcause]

http://homepage.mac.com/tlinespeakers/FAL/downloads/VarKalEL-191111.pdf[/url]

dave

OMG... You've taken my sketch and made it into a working design.... just for me..... what a Gent
All I need to do is put about 10 degree of angle on the front face and I'm in business
Cheers Dave, VERY much appreciated.

Chris/GM.... My Grandma had one of those floorstanding gramophones, blimey that takes me back......

 

[GM]

.........about the only detail I can remember was the changer was a Dual

takes me back to the innocent years - thanks, Greg

Bet it was a good one, my first 'HIFI' TT is a '70 Dual 1219 which I've kept for spinning old, much abused 45s, 78s.

Sometimes 'innocent' is still 'best', though the ~ modern ['02 vintage] DSP in the Toshiba sure helps, especially when turned up to fairly loud average levels. It turns a pair of whizzer cone 6.5" into a better overall performer than I can recall ever tweaking out of most 'el cheapo' RS or similar PA/car audio offerings.

GM

 

[sreten]

Hi,

Allthough not ideal have you considered modifying your cabinet such that
it is the enclosure ? FWIW I think the madisound kits referred to in a earlier
post is a good idea, careful with the different 8 ohm and 4 ohm driver specs.

rgds, sreten.

 

[Lostcause]

Hi sreten, yeah that was an option but by the time I had made the cabinet strong enough I would have virtually rebuilt it
This way I can make up the cabs in 'nude' form and just slide them in there with lots of wadding to cancel any resonance.
I've already ordered the markaudio drivers now and at just over 40 quid delivered they are a bargain
Already got the board and I'm marking it out now
Cheers guys
Lee

 

[sreten]

Hi, fair enough, sit them on foam for mechanical decoupling I think, rgds, sreten.

 

[planet10]

Bet it was a good one, my first 'HIFI' TT is a '70 Dual 1219 which I've kept for spinning old, much abused 45s, 78s.

My 1st one was a 1969 Dual 1210... it got a lot of miles.

I still have one of the previous gen (1109?) for use as a 78 player.

dave

 

[Lostcause]

Hi Dave, I had problems getting 15mm plywood so I've gone for all 18mm
As a result I've had to re-jig the dimensions based on what fits within my cabinet.

Is the revised design OK with that port length?... I assume it is, as the internal volume is very similar
https://docs.google.com/open?id=1ncBAv4vijWRdNZqAvt0JImi8ETFzaWY6E0HzFvZSZK8NaqQku3BrEAIYJXPT

I'm going to leave it all square as well. I have the flexibility with the size to angle them over 5 degrees within the cabinet if needed, this would be directly at head height when seated.

Cheers
Lee

 

[chrisb]

Hi Dave, I had problems getting 15mm plywood so I've gone for all 18mm
As a result I've had to re-jig the dimensions based on what fits within my cabinet.

Is the revised design OK with that port length?... I assume it is, as the internal volume is very similar
https://docs.google.com/open?id=1ncBAv4vijWRdNZqAvt0JImi8ETFzaWY6E0HzFvZSZK8NaqQku3BrEAIYJXPT

I'm going to leave it all square as well. I have the flexibility with the size to angle them over 5 degrees within the cabinet if needed, this would be directly at head height when seated.

Cheers
Lee

As long as you retain the internal volume and CSA/length of port the same, you can feel free to juggle the other 2 dimensions ( height and depth) within reason. Just don't reduce depth to the point that net aperture to port slot is occluded by back wall damping material.

A few well placed spacer blocks under the front of raw rectangular boxes should provide all the angle adjustment required. Keep in place with double edge foam tape or PSA velcro.

 

[Lostcause]

As long as you retain the internal volume and CSA/length of port the same, you can feel free to juggle the other 2 dimensions ( height and depth) within reason. Just don't reduce depth to the point that net aperture to port slot is occluded by back wall damping material.

A few well placed spacer blocks under the front of raw rectangular boxes should provide all the angle adjustment required. Keep in place with double edge foam tape or PSA velcro.

Cheers Chris, I was about to glue the cabs last night but stopped myself to just make sure first
TTFN

 

[planet10]

Is the revised design OK with that port length?... I assume it is, as the internal volume is very similar

Assumming that you have the net volume the same, you have decreased the cross-section of the vent, and increased its length by 3mm thus tuning it lower by a tiny bit. Shortening the shelf by 4mm will put it back in the same ballpark, but driver to driver variation would likely swamp the vent difference.

dave

 

[Lostcause]

Assumming that you have the net volume the same, you have decreased the cross-section of the vent, and increased its length by 3mm thus tuning it lower by a tiny bit. Shortening the shelf by 4mm will put it back in the same ballpark, but driver to driver variation would likely swamp the vent difference.

dave

Cheers Dave,
The cross section of the port has reduced because of the increased material thickness (6mm total)....but kept the length the same as your design. (the baffle was 18mm in your design anyway). So the net volume of the port is smaller but the same length.
The net volume of the whole cab is still the same however.
Cheers
Lee

 

[planet10]

When you decrease the X-section of a vent you also need to decrease its length to keep the same tuning.

When i looked at my drawing quickly this AM, i thot 15mm baffle on mine, but it was 18 so length is the same, shorten by a mm should keep thing sthe same. If you want to check my guess, i did up this vent sizing doc.

http://p10hifi.net/tlinespeakers/FAL/downloads/ChangingPortSize.pdf

dave

dave

 

[Lostcause]

When you decrease the X-section of a vent you also need to decrease its length to keep the same tuning.

When i looked at my drawing quickly this AM, i thot 15mm baffle on mine, but it was 18 so length is the same, shorten by a mm should keep thing sthe same. If you want to check my guess, i did up this vent sizing doc.

http://homepage.mac.com/tlinespeakers/FAL/downloads/ChangingPortSize.pdf

dave

dave

Cheers for that Dave, calculus isn't my strong point but.....
If port 'volume' is the critical part of the tuning then I need to reduce the length by about 8mm or make it thinner by 1mm. Crikey, I didn't realise just how critical the port tuning is

Is that right or am I being a bit thick
Also, can I ask what the tuning frequency is for that volume? I'm guessing about 60 hz?
If you could give me a pointer to some worksheets or programs I'll stop bother you guy's

 

[Lostcause]

Edit: Or make it thicker by 1mm I guess, so that the ratio of area to length is the same....

 

[Lostcause]

Hi guy's, cabs are done but I've left one side removable for now so I can tweak things...
With regard to the felt lining of the panels can I use this stuff?
I have an abundance of this Polyurethane foam to hand but not felt.....

Also, I'm not sure what to do around the port? Do I leave it clear by a inch or so?
Thanks chaps

 

[planet10]

That stuff is not nearly as effective as the felt but it will do in a pinch. Keep the vent clear of restriction.

dave

 

[Lostcause]

That stuff is not nearly as effective as the felt but it will do in a pinch. Keep the vent clear of restriction.

dave

Cheers Dave