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Other Gear => Speakers => Topic started by: Doc B. on October 02, 2009, 08:07:36 AM

Title: S.E.X.y speakers
Post by: Doc B. on October 02, 2009, 08:07:36 AM
NOTE: This is a very old thread and the links are no longer good.

(http://www.bottlehead.com/loosep/S.E.X.speaker_filtered.jpg)

Here's the formula for a splendidly simple DIY monitor/woofer speaker system designed to work with the S.E.X. amp. Total cost is less than $500! We don't sell any of these parts, but we have listed sources for each component. This should make a killer dorm room or office speaker setup, and it should work great in that first apartment, too. The small pre-finished cabinets and pretty Fostex drivers have a very high WAF, too.

 
   
(http://www.bottlehead.com/loosep/S.E.Xspeaker2-filtered.jpg)

Monitors

The monitors operate from about 125Hz up. They are composed of Fostex FE166E full range drivers in pre-finished Dayton .25 cubic foot sealed cabinets from Parts Express. The only scut work is that you have to cut holes in the front baffles for the Fostex drivers. Here's the basic parts list -

Drivers - Fostex FE 166E - from Madisound - one pair needed
http://www.madisound.com/cgi-bin/index.cgi?cart_id=7741375.12505&pid=324 (http://www.madisound.com/cgi-bin/index.cgi?cart_id=7741375.12505&pid=324)

Cabinets - Dayton .25 cu.ft. pre-built cabinets - from Parts Express - one pair needed
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=302-702 (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=302-702)

Cabinet Damping - Acousta-stuff polyfill - from Parts Express - 1lb. will be more than enough
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-317 (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-317)

Binding posts - Dayton knock-in binding post - from Parts Express - two pairs needed
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=091-1245 (http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=091-1245)

Assembly is pretty self-evident. You will need to cut holes in the front baffles to mount the drivers, using the template provided with the drivers. We used an adjustable fly cutter that we got from Home Depot on a 1-1/2 HP floor standing drill press, and just centered the holes on the baffles. If you don't have that kind of equipment, maybe you can cut a round enough hole with a saber saw??? We'll leave any alternative hole making approaches up to you!

Stuff each cabinet with about 1/8 lb. of the Acousta-stuff. Install the binding posts and wire the speaker terminals to them - red to + and black to -, with your favorite flavor of wire. You may want to solder the connections, or one could install crimp-on quick connectors. Use long enough wires to make it easy to connect the wires with the drivers sitting outside the box. Mount the drivers and their gaskets, and the monitors are done!

Woofers

The woofers we originally spec'd are a pair (yes, you must use two because of the high 125Hz crossover frequency) of Parts Express subwoofers. However you may use whatever generic active subwoofers you prefer. Just be sure what you get can be set to a 125Hz or so crossover frequency. We call them woofers rather than subwoofers in this case precisely because they are running up so high. The Dayton subs mentioned here were chosen on the basis of cost, and because you will be ordering a most of the rest of the project from PE (man, they should give us a commission!). They are down firing subs. In theory a front firing sub will integrate better - and typically cost more.

Woofers - Dayton 10" 125W active subwoofer - Parts Express - you will need TWO.
http://www.partsexpress.com/pe/showdetl.cfm?DID=7&PartNumber=300-633 (http://www.partsexpress.com/pe/showdetl.cfm?DID=7&PartNumber=300-633)

Hooking it up

Run the signal from your CD player/sound card/Ipod/whatever into your S.E.X. amp with interconnects. Connect speaker cables from the speaker output binding posts on the S.E.X. amp to the left and right monitors. Then run more speaker cables from the binding posts on the monitors to the input binding posts on the corresponding subwoofer, with the woofer connections reversed (red post on monitor to black post on woofer, black post on monitor to red post on woofer). Connecting the system this way will avoid running the signal through a 125Hz filter that's built into the monitor output of the subwoofer. That filter would interfere with the designed roll off of the monitors and mess up their bass response. 

Keep the woofers close to the monitors. They are running up to 125Hz and at that range you can definitely localize where the sound is coming from. Aligning the monitors so they are directly over the woofers will probably give the best integration of midrange-to-bass. Try to set the monitor height so that the center of the Fostex driver is close to level with your ear when seated. The Fostex drivers are very directional, and you may find that the the highs will sound best with the speakers aimed directly at you. They will also squawk until they break in! Be patient, they do tone down with use. Start with the woofer crossover frequency set to about 125Hz, the output turned all the way down, and the phase set to 0 degrees. While playing music bring the woofer gain up slowly until it sounds balanced with the midrange emanating from the monitor. There may be a slight "hole" in the lower midrange.  Fiddling with the phase switch (or knob) may help. Be careful to set the phase the same way on both woofers, or your bass may disappear! A great way to get the system to sound more balanced is to incorporate a baffle step correction filter (BSC), which compensates for the lower midrange/upper bass rolloff which occurs due to the narrow baffle width of the monitor cabinet.

Apologies for the delay in getting photos of a line-level BSC installation on the page. Meanwhile here's a circuit:

 

IN ------------------- 0.0012uF -------------- OUT
      |                      |
      --- 10k ohm -----
                      |
                      |
                    10k ohm
                      |
                    0.033uF
                      |
GND ------------------------------------------- GND

The 0.0012uF is optional and provides the treble boost if your room and taste calls for it. You can go up to twice that value if more treble is desired.

This circuit can be placed at the input of the power amp (e.g. SEX amp).

 

 
Title: Re: S.E.X.y speakers
Post by: Thoburn on October 24, 2009, 01:30:02 PM
Hi Bob,

Is this the ciruit that Paul Joppa is refering to in his reply to my Lowther post over in the Paramount forum?

Thanks,
Thoburn (Toby)
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on October 24, 2009, 02:26:06 PM
Yes it is, but the formatting did not come across. Here's another try at the circuit:

Title: Re: S.E.X.y speakers
Post by: Thoburn on October 25, 2009, 07:33:35 AM
Thank you Paul for the clarification. The values are very different than the circuit used inside my DX4 cabinet. And there is no inductor in your circuit. Is there an equation that gives starting values for the components based upon the driver and cabinet being used? The Fostex 166 in that skinny cabinet and subs to carry the bass is signifcantly different from my single Lowther in a 12 inch wide MLTL.

Toby
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on October 25, 2009, 11:15:29 AM
The circuits are quite different indeed! What's in the cabinet is at speaker level, meaning a load impedance of 8 ohms (or 4 or 15 or whatever the speaker is). At line level, between preamp and power amp, most devices want to see at least 10000 ohms load impedance. You can get away with RC circuits (no inductors) here because there is no need to maintain a low resistance in the bass for good speaker damping.

The circuit as drawn is optimized for an 8.5-inch baffle width. A wider baffle will want a larger value for the 0.033uF capacitor, in proportion - so for example, use 0.047uF for a 12-inch baffle. Of course this is a theoretical value assuming perfect speakers and an anechoic chamber for a listening room, so feel free to experiment with different values! The value does not need to be precise because the step response function is very gradual; it will be difficult to hear changes of less than 20% in value.

The baffle step function occurs at several hundred Hz, well above any subwoofer, so the presence or absence of a sub will make little difference in the optimum BSC component values.
Title: Re: S.E.X.y speakers
Post by: rchristie on November 08, 2009, 06:16:46 AM
Doc,
 
Congratulations on the new site, it looks great.  I thought I'd try out the new forum to ask a question that has been bugging me for a while about the "hooking it up" instructions on the SEXy speakers:

Quote
Hooking it up

Run the signal from your CD player/sound card/Ipod/whatever into your S.E.X. amp with interconnects.  Connect speaker cables from the speaker output binding posts on the S.E.X. amp to the left and right monitors.Then run more speaker cables from the binding posts on the monitors to the input binding posts on the corresponding subwoofer, with the woofer connections reversed (red post on monitor to black post on woofer, black post on monitor to red post on woofer). Connecting the system this way will avoid running the signal through a 125Hz filter that's built into the monitor output of the subwoofer. That filter would interfere with the designed roll off of the monitors and mess up their bass response.

What is the rationale for reversing the connections from the monitor to the woofer?  Is it that the reversal of the woofer connection results in the bypassing of the built-in filter?  Or are there two different things going on here, one of which is the bypassing of the internal filter by hooking up the monitor and woofer in parallel, and something else to do with reversing the polarity of the signal? 

At any rate, thanks again for the great music, and great fun, with the kits!

RChristie

Rich Christie
Title: Re: S.E.X.y speakers
Post by: Paul Birkeland on November 08, 2009, 08:01:33 AM
You could run the speaker cables out of the SEX amp into the subwoofer, then out of the subwoofer to the monitors.  This hookup style will impose a highpass filter on the monitors.  Running the signal to the monitors first will let them play the entire spectrum. 

Hooking the speaker leads up out of phase puts the woofer and monitor drivers out of phase with each other, allowing for better blending between the drivers. 
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on November 08, 2009, 09:29:39 AM
Just to augment CB's response, the effective acoustic crossover is approximately a second order Linkwitz-Riley, which calls for the LF and HF sections to be out of phase. If your sub amp has a phase switch, you can use that instead of reversing the leads. If the phase is wrong, there will be a big suck-out at the crossover frequency.
Title: Re: S.E.X.y speakers
Post by: rchristie on November 08, 2009, 11:10:58 AM
Thanks to both of you for the replies.  Paul, should that phase relationship with the subwoofer also hold for the Climax  (using the passive crossovers only, without the line-level tweak)?
Title: yes (nt)
Post by: Paul Joppa on November 08, 2009, 12:43:39 PM
nt
Title: Re: S.E.X.y speakers
Post by: Thoburn on November 11, 2009, 05:54:32 AM
The circuits are quite different indeed! What's in the cabinet is at speaker level, meaning a load impedance of 8 ohms (or 4 or 15 or whatever the speaker is). At line level, between preamp and power amp, most devices want to see at least 10000 ohms load impedance. You can get away with RC circuits (no inductors) here because there is no need to maintain a low resistance in the bass for good speaker damping.

The circuit as drawn is optimized for an 8.5-inch baffle width. A wider baffle will want a larger value for the 0.033uF capacitor, in proportion - so for example, use 0.047uF for a 12-inch baffle. Of course this is a theoretical value assuming perfect speakers and an anechoic chamber for a listening room, so feel free to experiment with different values! The value does not need to be precise because the step response function is very gradual; it will be difficult to hear changes of less than 20% in value.

The baffle step function occurs at several hundred Hz, well above any subwoofer, so the presence or absence of a sub will make little difference in the optimum BSC component values.


Hi Paul,

What would changing the resistor values do?
Thanks!
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on November 11, 2009, 09:22:11 AM
Changing resistor values would change the frequencies just as the capacitor values do - the frequency of any response corner is inversely proportional to the RC product. But changing the resistor values will also change the impedance of the circuit, smaller values placing a more severe load on whatever is driving the circuit, and larger values requiring a greater minimum impedance of the device that follows the circuit.

Right now, I would recommend that the source driving the BSC be capable of driving 10K ohms and have a source impedance no greater than 1K; and the load (amplifier input impedance) be no less than 100K ohms. These are not absolute requirements, just general recommendations.
Title: Re: S.E.X.y speakers
Post by: nullspace on February 05, 2010, 04:42:55 AM
Hi Paul,

With the S.E.X.y speakers, what impact does the 3-4ohm output impedence of the SET amp plus the impedence peak of the FE166s have on the input signal seen by the subwoofer amps? I modeled the FE166 in a .281cu ft. and it looks like the impedence peak is at ~120hz. So, wouldn't there be a bump up in voltage-out from the SET centered on ~120Hz, and consequently also in the input signal to the sub amp? And, if that's the case, does that have a small impact or a large impact?

Thanks for the help. I've been wondering about this for a while, and I haven't been able to wrap my head around it.

Regards,
John
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on February 05, 2010, 05:34:15 AM
Yes, you are correct. It will create a bump of about 3dB, right at the crossover point. The subs I am familiar with have a Linkwitz-Riley second order function which is 6dB down at the crossover point, so you are left with a net 3dB down, i.e. a Butterworth filter function.

The electrical Q of the FE-166 in the box is also greater with an SET driving it - it comes out to approximately a Linkwitz-Riley with high damping, and Butterworth with an SET. But that does not account for the large amount of stuffing, which will decrease the mechanical Q and the net Q. I haven't measured this myself so I can't quantify it, but the effect will probably be modest, around 0.1 change in the total Q.

In an anechoic chamber, this will give a 3dB bump at 125Hz if the sub driver is very close to the FE166 (a tenth of a wavelength is about one foot). For large separations, the average power into the room is flat for a Butterworth. But room effects are much larger than this, so I have not worried about it excessively. For perspective, note that open-baffle designs, which are quite popular these days, have a 3dB bump at their bass cutoff, usually around 200Hz.

At the time this was developed, I was expecting we would have a crossover product soon. One application for that would be to add a second order Butterworth function to both the sub and the fullrange, to produce a net fourth order Linkwitz-Riley crossover. That task is proving more complex than we anticipated, and I have not yet had a chance to audition the result with a S.E.X.y system so I can't even say I prefer it - though in theory it would be a big help.
Title: Re: S.E.X.y speakers
Post by: nullspace on February 05, 2010, 06:33:19 AM
Thanks very much for the thorough answer, Paul; I really appreciate it.

The more I look at other people's work, the more I realize how well thought-out and sneaky-smart a lot of it is.

Regards,
John
Title: Re: S.E.X.y speakers
Post by: debk on April 29, 2010, 04:34:02 AM
I am thinking of building some speaker in the future.  Has anyone compared these to using the Fostex full range driver in a folded horn cabinet like the BK16 on the Madisound web site?

Thanks

Debra
Title: Re: S.E.X.y speakers
Post by: Maxwell_E on July 23, 2010, 08:35:06 PM
I am confused a little bit. Call me a newbie, but I can't figure out exactly where to hook the BSC into on my SEX amp. I'm not too good with schematics or anything and I don't really know where the preamp ends and where the power amp begins. Someone please help me before I cause any more trouble.
Title: Re: S.E.X.y speakers
Post by: dbishopbliss on July 24, 2010, 03:05:31 AM
In the post above Paul says, "This circuit can be placed at the input of the power amp (e.g. SEX amp)." 

I think if he were suggesting a change to the circuit of the SEX amp, he would have given more detailed instructions.  Therefore, put the BSC circuit between your CD player and the SEX amp.  CD Player OUT goes to the BSC IN, BSC OUT goes to SEX amp IN.
Title: Re: S.E.X.y speakers
Post by: rob on November 22, 2010, 06:07:32 AM
Has anyone built these?  I finished up my S.E.X. a few months ago and have been enjoying it through my HD-600's, but find myself wanting to add speakers. 
I've been wanting to try these, but haven't actually seen anyone who's given them a shot.
Title: Re: S.E.X.y speakers
Post by: booangler on December 30, 2010, 12:29:14 AM
Has anyone built these?  I finished up my S.E.X. a few months ago and have been enjoying it through my HD-600's, but find myself wanting to add speakers. 
I've been wanting to try these, but haven't actually seen anyone who's given them a shot.

That Sir is a great question! Has anyone tried these out. As of today you can some good prices at PE for the components that closely match the original suggested items. The special price on the Sub woofers ends 12/31
Title: Sexy speakers w/out sub but w/ port?
Post by: myrun on March 07, 2011, 12:52:48 PM
Hi B'heads,

Well, I have the 166 fostex drivers and the .25 cf cabinets from Parts Express.  I don't have the subwoofers and am not planning on buying them for budget reasons.  I understand that the 166s in the sealed cab will really only reach down to 125hz. 

Could I move the driver up a little in the cabinet to fit a port down below?  Is this a worthwhile endeavor to try to get the response down below 100hz?  If so, what diameter of port tube should I order and what length should I trim it to?

Sorry for knowing nothing about speaker design, but since I have all the goods except for subs, can I do any better than sealed response with a port?  Thanks in advance folks.

Regards,
Mario
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on March 07, 2011, 01:52:15 PM
Not in those boxes. The vented alignment gives almost exactly the same response in the 0.25CF box; mostly it just lets the cone flop around more below the vent frequency.

In a larger box, 0.5 to 1.0 cubic feet, you can get some decent bass, down to 50 or 60Hz with a vent. But the increased excursion leads to audible distortion at any useful loudness. That was my first design for this speaker; we just didn't like the distortion. (A non-audiophile friend bought the prototypes and loves them - go figure.)

By the way, all these designs assume an SET amp with damping factor of 2 to 3. With a high-feedback solid state amp, you can get down to 125Hz with a vent but the sealed box only goes down to 180Hz or so.
Title: Re: S.E.X.y speakers
Post by: myrun on March 08, 2011, 02:49:47 PM
Thanks Paul for the quick response!

I'll have to re-think my decision not to buy a couple relatively cheap subs but in any event won't try to shoe-horn a port w/ 166s in .25cf boxes...I suppose thats one less hole to cut in the baffle! 

But just one more stupid question to suffer:  If I save my 166s for another day and bigger box and instead use these .25cf boxes for a 4ish" single driver ala fostex or tang bang, is it indeed that case that I might entertain a port if driver Q < .4 but not to consider it for driver Q > .4?  Unfortunately, I'm barely starting to learn just a little about speaker/box compatability....that is, just enough to be dangerous.

Best regards,
Mario

PS: I really enjoyed SEX amp camp many summers ago in SF and would be willing to go up the coast to your neck of the woods for another......
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on March 08, 2011, 06:50:37 PM
I use a shareware program called "Boxplot" - it's quite old, and there are many more modern alternatives. Get one and learn to use it, then you can play around and learn a lot!

Speakers of lower efficiency can go deeper in the same box. That's sometimes called "Hoffman's Iron Law".

Q is a more complex issue that it seems. First off, QT is the "total" Q, usually dominated by the electrical QE, with the mechanical damping QM a much smaller player. But QE is based on an infinite damping factor. When using SET amps with no feedback, QE is increased by 30% to 50% - and so is QT. This makes a big difference in box design.

The mathematically simplest ported boxes are for a speaker with QT = 0.38. But you can tune the box and get good enough results if the Q is in the range of 0.25 to 0.5 - the higher QT will require a larger box and will go deeper. A large QT indicates a stiff suspension, which will usually be less linear. Such a system often has a more constricted-sounding bass. The bass can extend to around 0.4 times the speaker resonance, divided by QT.

For sealed boxes, a QT of 0.5 or less is desired. You can only extend the bass to 0.7 times the speaker resonance, divided by QT; many people prefer to keep it a bit higher. The box will be smaller than the ported box.

Be aware that cone volume displacement (diaphragm area times peak displacement xmax) must increase rapidly as you go deeper. As I said, getting the FE166 down to 50Hz (for example) exposed this weakness; cutting it off at 125Hz eliminated that problem. Small drivers usually have small displacement limits as well.
Title: Re: S.E.X.y speakers
Post by: myrun on March 09, 2011, 04:10:19 PM
Thanks again Paul,

I'll check out some box design shared software...I understand what you've written enough to understand that ported v sealed box design choices involve much more than a total Q factor litmus test.  I'll complement this software-based learning by purchasing another set of baffles for $20 so as to experiment with both sealed and ported using just one pair of boxes.  There is a bevy of relatively cheap 4"ers to try and am looking forward to much fun with this.

Regards,
Mario
Title: Re: S.E.X.y speakers
Post by: Wanderer on December 09, 2011, 01:52:11 PM
I may have an oppertunity to aquire some Fostex 206e (not the new "EN"). I note that Parts Express has some cheapsy sub-woofers on special.   

Any thoughts if a S.E.X.y-ish speaker could be made using the 206?

Kevin     
Title: Re: S.E.X.y speakers
Post by: btrancho on December 09, 2011, 02:54:42 PM
Kevin,

I have built the Half Changs  here  (http://www.frugal-horn.com/spawn-plans.html) using the 206e and they were marvelous.

You can see  my build thread in the DIY Audio forum (http://www.diyaudio.com/forums/full-range/109576-half-chang-build.html)

The Chang family is really designed for the Fostex 207, but the BSC described in the thread worked quite well.  The 206e is an 8" driver so your box will be much larger than the one described in this thread, but properly designed, you might get away without having to use a sub woofer.  These Changs easily go down into the 40Hz-45Hz range.

Search the DIY Audio Full Range forum and you'll probably find some other designs for the 206e.  I believe other members of this forum have DIY 206e speakers, as well.

(http://www.trancho.net/HC/hc.jpg)
Title: Re: S.E.X.y speakers
Post by: Paul Joppa on December 09, 2011, 06:10:25 PM
I may have an oppertunity to aquire some Fostex 206e (not the new "EN"). I note that Parts Express has some cheapsy sub-woofers on special.   

Any thoughts if a S.E.X.y-ish speaker could be made using the 206?

Kevin     
Sure! Looks like with an SET amp, a 0.5 cubic foot sealed box will work, crossover at about 85Hz.