Need a little help with a birthday present

[vitalstates]

love the curve

have to say, after many builds and much measurement, I far prefer the curve to straight or angle corners.

Havn't tried it with a pipe terminus though.

Ed

 

[Scottmoose]

It can be useful for horns (expanding pipes) depending on circumstance, I agree. Reverse taper pipe? I'm not convinced as yet.

 

[sreten]

Hi,

Whilst it looks nice its very inefficient way of folding in a shallow box.
The arrangement shown earlier takes up far less volume internally
and the final box would be far more rigid, as the partition also
makes up a nice front to back brace when its a shallow box.

rgds, sreten.

 

[oublie]

Hi,

Whilst it looks nice its very inefficient way of folding in a shallow box.
The arrangement shown earlier takes up far less volume internally
and the final box would be far more rigid, as the partition also
makes up a nice front to back brace when its a shallow box.

rgds, sreten.

Sreten,

What would you recommend as a better method to fold it please bear in mind i'm not even close to competent at translating the schematic into a workable sketchup design. Will i get too much chuffing if the mouth is too narrow?

 

[oublie]

If i wasn't so stupid i'd be dangerous

I finally worked out what i was doing wrong when it came to the design i.e. trying to fold like a normal cabinet. Sometime you have to think sideways so here's what i hope is my final design. I've moved the driver onto the front of a narrow but wide and high cabinet it is still at the correct position for the driver and it even models well in basta when it comes to baffle step.

here are some pics, the design in 3d, in basta (doesn't do horns so i ran a ported box just for effect) showing the design in 2d (ignore the port), response off axis and on axis.

 

[chrisb]

You should try to avoid shallow mounting depth - no matter how you fold the pipe, you'll likely experience a lot of high amplitude very early reflections from the back panel that will color the midrange.

I learned that the hard way with several CSS FR125 and Fostex based designs a few year back.

If your floor space permits, something like sreten's original drawing would likely give much better overall sonic performance.

and use hard angles at the fold's corners to your advantage as in your second drawing

 

[oublie]

I didn't consider the effect on the midrange Chris. What if the back was stuffed would this mitigate the problem? sreten mentioned that wide and tall i.e. close to the wall will help the baffle step so i'm guessing that if i increase the depth by double and change the other dimensions the speaker has more breathing room and the mids will improve at the expense of other consideration.

 

[planet10]

Reverse taper pipe?

What is a reverse taper?

Further to the above, we talk about horn flare, a reverse taper would be the same.

dave

 

[Scottmoose]

I was applying it in the context of a reverse taper horn (what I call a TQWT), although admittedly that's just me lurking in my own little corner of the hifi world.

 

[planet10]

A TQWT/Voigt does have a reverse taper, ie a conical flare. Even thou the term TQWT can be a bit confusing, we should just nuke that term and call them Voigts to eliminate any ambiguity (and as a tribute to the great man himself)

dave

 

[chrisb]

I didn't consider the effect on the midrange Chris. What if the back was stuffed would this mitigate the problem? sreten mentioned that wide and tall i.e. close to the wall will help the baffle step so i'm guessing that if i increase the depth by double and change the other dimensions the speaker has more breathing room and the mids will improve at the expense of other consideration.

Well to be honest, I don't get too exercised over battling with baffle step loss, and would personally tilt my compromise towards increased imaging ability normally resultant from narrower baffles and enclosure placement far enough from back / side walls to allow for any required toe-in.

I think you'd also need to be careful with over-damping of the back wall of shallow enclosures to mitigate reflections - changing the density gradient in the vicinity of the driver could well have a deleterious effect on the overall damping scheme.

The few wide/shallow enclosures that I have built (PAWO/Mileva/Demitri) all suffered to my ear with minor congestion most notable on voice that become rather fatiguing.

Fortunately there are recent drivers that have a measure of BSC contour cleverly engineered into their raw response curves. For sure the Mark Audio 70mm and larger drivers don't suffer from lack of lower mid-bass even in narrow cabinets like the Pensil and others.

 

[sreten]

Hi,

Doubling cabinet depth for a nebulous reason is not a good idea.
What you can do is assume you'll put quality damping material
directly behind the driver, e.g. whilst BAF or similar can be used
for general stuffing, put some quality acoustic foam on the back
panel directly behind the driver.

Cabinet depth is determined by "efficiency", the ratio of the
volume of wood to build it compared to the total volume.
If the depth is too low the above becomes very high.

Neverless the arrangement I suggested does have ~ twice
the depth of the first suggested folding arrangement, QED.

rgds, sreten.

 

[oublie]

so we have two differing opinions.

these are being wall mounted either side of a t.v. so narrow and wide will be good.

Too narrow will give my son an issue with midrange not that he will probably notice - but that's not the point.

a happy medium is obviously the solution so i will play around with sketchup and try to get that happy medium tommorrow.

I truly thought that hornresp was all i needed - how wrong i was, this folding malarky seems like it can make or break a speaker so i'm going to leave that part to trial and error.

In the coming days i'm going to build at least one cabinet and see how i get on hopefully i won't be too far off the mark.

I'll post pics and polars once i'm done.

any more suggestions will be appreciated - thanks for all the info so far guys i've learned so much from this forum.