CSS 3 way bookshelf speakers

[sam xt]

Hello everyone, I have been reading these forums for a while but this is my first post.

So for some time I have been toying with the idea of a bookshelf speaker made with the following drivers from CSS, SDX7, FR125, and the RT1. My idea is to arrange in a mtw arrangement all sealed.

I have looked around and have planned to have the SDX7 in 7L sealed, the FR125 in a 9.4L sealed and the RT-1 in its own small compartment.

So now the question where I hope someone with more experience will come in - the crossover. To start will all be passive. The following pic shows what I have come up with for values. Crossover points are 500 and 4000 Hz.

An externally hosted image should be here but it was not working when we last tested it.

The crossovers will all be wired in parallel. They are based on a butterworth arrangement, and the values for caps and inductors were calculated based on the impedance at the crossover frequency.

So if someone could help me out and have a look over, let me know if I'm way off base here. I'm also flexible to the crossover points and any other recommendations about my preliminary design.

Below is the plan for the speakers, curved sides, with a walnut veneer finish on sides and top, and a curved leather wrapped front baffle. Not a very good pic to start but I'll find another and post it soon.

An externally hosted image should be here but it was not working when we last tested it.

I know it's a long first post, but I look forward to hearing your feedback and I'll be posting pics of it when I get it started.

Thanks again to everyone here!!

Sam

 

[gz76]

Wow, great diagram there... it always amazes me how people use Excel creatively to do diagrams. My sister-in-law uses it like graph paper to do floorplans and calculate areas!

I'm sure the original designers of the software only ever thought it would be used for dealing with boring stuff like numbers!

 

[planet10]

So for some time I have been toying with the idea of a bookshelf speaker made with the following drivers from CSS, SDX7, FR125, and the RT1. My idea is to arrange in a mtw arrangement all sealed.

I have looked around and have planned to have the SDX7 in 7L sealed, the FR125 in a 9.4L sealed and the RT-1 in its own small compartment.

I'd allocate the volume somewhat differently... the RT1 doesn't need any enclosure as it is sealed from the back. I'd put the FR125 in no more than 7 litre, I'd actually use 5-6 litres and vent it aperiodically out the back. The SDX7 can work in pretty small sealed box, but if possible i like to get it up to at least 14 litre, where it really shines.

Also the SDX7 really benefits from 1st order cone treatment to tie the carbon fibres together.

XOs i try to stay away from. On all 3 of the speakers i have with SDX7 i cross-over actively. With the extended range upward of the (treated) SDX7 and the ability of the FR125 to go low, you could away with a pretty simple 1st order PLLXO -- i'd also push the XO lower than 500 Hz to take advantage of the FR's FR capabilities.

Tweeter to mid is a bit trickier. RAW had his XO a bit higher 4250 IIRC, i'd give a try to just a single cap on the RT1 as a starting place (XO up at 10-12k) just to see what that does.

dave

 

[sam xt]

Revised crossover

Thanks for the help Dave,

Here is what I have now for the crossover.

An externally hosted image should be here but it was not working when we last tested it.

The main changes are:
Crossover between mid and bass is now a first order at 360Hz
Upper crossover point has been raised to 7200 Hz and only has a cap on the tweeter.

I'm revising my box plan now to allow the volumes you recommended.

 

[sreten]

Hi,

Your going to need two SDX7's to match the FR125S.
(look up baffle step compensation).
The SDX7 in 7L sealed works, but venrted low is much better.
Shown are graphs for 2 SDX7's, which coulds be mounted
in force cancellling mode like the AudioPhysics Virgo.

See : http://rjbaudio.com/Extremis/extremis.html

/sreten.

 

[sreten]

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/DesigningXO.htm

http://www.zaphaudio.com/
http://www.rjbaudio.com/projects.html
http://www.geocities.com/woove99/Spkrbldg/
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
http://htguide.com/forum/forumdisplay.php4?f=39
http://www.humblehomemadehifi.com/

/sreten.

 

[planet10]

The SDX7 in 7L sealed works, but venrted low is much better.

It may model better, but the sound of an SDX7 hitting its stops is not pleasant... i'm sticking with the sealed air spring to help prevent that.

dave

 

[sreten]

It may model better, but the sound of an SDX7 hitting its stops is not
pleasant... i'm sticking with the sealed air spring to help prevent that.

dave

Hi,

And your point is ? Other than stating the obvious ?
What so special about the SDX7 than means sealed is better than vented ?
Unless you just saying sealed is best .... which it is not .... is this case ....

/sreten.

 

[planet10]

And your point is ? Other than stating the obvious ?
What so special about the SDX7 than means sealed is better than vented ?
Unless you just saying sealed is best .... which it is not .... is this case ....

Every non-sealed box i've tried for these has had to have the port stuffed to aperiodic to keep them from bottoming out. For this woofer, i eould indeed say sealed is better.

dave

 

[sreten]

Every non-sealed box i've tried for these has had to have the
port stuffed to aperiodic to keep them from bottoming out.
For this woofer, i eould indeed say sealed is better.

dave

Hmmmm..........

Triumph of claimed experience over engineering ?

On paper there is absolutely no reason why they should bottom
out. Vas is not excessive for a 6.5" driver which means that the
surround is quite stiff, the low Fs coming from the cone weight.

Only if the driver is badly designed (see klippels papers) will
it be prone to "bottoming" out / jumping out of the gap, and
for that case lower Vbox will linearise a dodgy suspension.

This should be very unlikely for an XBL motor, Zaphs analysis of
long throw 6.5" drivers indicates that excursion is suspension
rather than motor limited.

I've never read anything anywhere else that implies the SDX7 and
its precursor the Extremis is not suitable for vented loading. Noting
a vented single driver is the same as four sealed drivers at the port
frequency two drivers in 30L tuned to 30Hz looks very good for a
full range (no sub) design, and it should do at > $200 a pair.

And like all vented designs if using vinyl a rumble filter is mandatory
if you intend to use the driver near up to its maximum capability.

/sreten.

 

[planet10]

Hmmmm..........

Triumph of claimed experience over engineering ?

On paper there is absolutely no reason why they should bottom
out. Vas is not excessive for a 6.5" driver which means that the
surround is quite stiff, the low Fs coming from the cone weight.

Only if the driver is badly designed (see klippels papers) will
it be prone to "bottoming" out / jumping out of the gap, and
for that case lower Vbox will linearise a dodgy suspension.

I've successfully used extremis in vented box. People use SDX7 in vented box too, but both the SDX7 and the FR125/WR125 give no warning of running out of excursion, Push then too far and they fart. Transition from just fine to over the top is very abrupt. A very unpleasant sound. SDX7 works very well sealed and handles a bit of boost just fine. I love that we have a driver that works so well sealed,

I have both Trio8 & SDX10 here now, we'll see if they do the same thing.

dave

 

[sreten]

...but both the SDX7 and the FR125/WR125 give no warning
of running out of excursion, Push then too far and they fart.
Transition from just fine to over the top is very abrupt.

dave

Hi,

As it has to be with a very linear BL curve versus excursion,
an issue covered in some detail in Klippels distortion paper.

Note that I'm not saying sealed does not work, it should
work very well, but it will not have the SPL capabilities
in the low bass of a low bass tuned vented alignment.

And I'll repeat again aggressive filtering of vented boxes
below the port frequency is needed to explore the SPL
capabilities. It is not needed for lower power valve /
class A amplifiers so much, here the higher efficiency
of the vented alignment in the low bass is a plus.

/sreten.

 

[planet10]

aggressive filtering of vented boxes
below the port frequency is needed to explore the SPL
capabilities. It is not needed for lower power valve /
class A amplifiers so much, here the higher efficiency
of the vented alignment in the low bass is a plus.

The filter needed has its own issues. With the FR125S the problem is most evident with SE amps (small or big tube ones, or SS ones)

dave

 

[sreten]

The filter needed has its own issues.

dave

Hi,

Of course it does, but any vented speaker or subwoofer
designed for maximum SPL correctly should include one.

As its an active filter I cannot see what
the type of amplifier is has to do with it.

/sreten.

 

[planet10]

As its an active filter I cannot see what
the type of amplifier is has to do with it.

Nothing to do with any filter. It is just really easy to get an FR125 to fart, even at modest levels, with an SE amp, Just a clue to how they run out of steam.

dave

 

[sreten]

Nothing to do with any filter.
It is just really easy to get an FR125 to fart, even at modest
levels, with an SE amp, Just a clue to how they run out of steam.

dave

Hi,

The fact that SE amplifers fart when they run out of steam
(in one current direction) gives you no clue as to the nature
of a drivers overload characteristic.

Low sensitivity and bass boost are SE amplifier killers,
they cannot cleanly provide the necessary current.

Severe assymetric current limiting does not sound good,
and leads to DC driver offsets, which will be less of a
problem with a driver in a sealed box compared to vented.

If designing speakers around the foibles of amplifiers it
should be clearly stated and apparent that this is the
case, and the reader should not be misled by "facts"
that are technically misrepresented.

/sreten.

 

[planet10]

Low sensitivity and bass boost are SE amplifier killers,
they cannot cleanly provide the necessary current.

2 of the SE amps were easily able to deliver the necessary current.

dave

 

[sreten]

Hi,

Well you are going round in circles and as far as I can tell
implying all is not rosy with the SDX7 unless you go sealed,
but cannot explain why this should be or is the case.

I'm not responding to contrary one-liners any more.

/sreten.

 

[planet10]

Well you are going round in circles and as far as I can tell
implying all is not rosy with the SDX7 unless you go sealed,
but cannot explain why this should be or is the case.

Since i was talking about FR125 in the last posts i wonder how you come to that conclusion, I was just reporting real-world experience, take what you want of it.

dave

 

[sam xt]

Build pics

Well its been a while but I'm finally getting around to posting some build pics and the final pics as well.

First off below is the updated plan for the speakers. Each driver is in its own enclosure, all of them with curved sides to match the sub I built earlier. The front baffles for mid and bass are wrapped in leather and the tweeters baffle is in black felt.

An externally hosted image should be here but it was not working when we last tested it.

So first off some pics of the drivers, as mentioned before they are: SDX7, FR125, and RT-1; all from CSS. The build quality of these drivers is incredible.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

The construction of the boxes was the same as it was for the sub. First I made a baltic birch plywood frame with the front, top, back, bottom, and internal ribs of the enclosure. Then for the curved sides 4 layers of 1/8" BB ply was laminated over top of the frame.

An externally hosted image should be here but it was not working when we last tested it.

Edges were then trimmed, driver holes cut and pieces of walnut, less then 1/16" were put on the sides and walnut veneer on the top. Then several coats of wipe on poly and felt was applied to the bottoms, some tops, fronts and backs. (I still haven't covered the backs with felt)

An externally hosted image should be here but it was not working when we last tested it.

The front baffles/covers can be seen below covered with either leather or felt.

An externally hosted image should be here but it was not working when we last tested it.

The crossover points are at 360 and 7200. First order at 360, and second order at 7200.

Here are a couple pics of the finished speakers.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

I'll try and get some better pics of them up in a few days. You can also see the matching sub in one of the pics.

I'll also find the schematic for the crossover and some picks of them.

Now for my first impressions. I have about 30 hours on them so far, but I think they are amazing. These replaced some cheap 2 ways I made before out of spare parts. I don't want to use to many subjective or fluff terms, but... the highs on these are so crisp and clear the bass is not boomy but nicely controlled and tight. They sound fantastic at all volume levels. The detail in the entire spectrum is astounding. Music sounds much different on these, and in a very good way. I'm able to sit and listen to music for hours at a time and hear things I didn't hear before. I can say that I am very happy with these drivers and the overall sound of the system.

(I guess to note, they are being driven by a H/K AVR-254 receiver.)

Let me know if you have any questions or comments.

Sam