Here is an updated version of NASP the NASP II.

It uses the Peerles Nomex 164 WR 33 102 NWP AL LS 8 ohm Bass/mid.  This woofer has a nice smooth mid band response and good off axis response. There is a break up mode peak centered on 4.5 kHz from 3 to 5 kHz.  This basically mandates a crossover around 2 kHz.

The Tweeter is the highly cost effective Vifa BC25SG19-04.   This tweeter has a flat response in its pass band to 9 kHz were a gradual HF roll off begins.  The roll off becomes steep at 18 kHz.  However for a small bookshelf speaker this is no bad thing, and I have made no attempt to correct this HF fall off.

Fs is 1060 Hz so I have made the tweeter to be 24 down at Fs.

The woofer is in a standard B4 ported enclosure.

The crossover

Here is a cost effective three way speaker.  It uses the paper coned Peerless SLS 830668 woofer, the Audax carbon fiber HM130C0 as the mid range and the soft dome Vifa 27TG-35-06 Tweeter.

This makes a very decent three way speaker with an F3 of 26 Hz.

Here is the optimal box for that woofer.

Note that driver and vents will displace about .2 cu. ft.

Here is the sealed mid range cavity.

The driver displaces about 0.01 cu. ft.

Here is the crossover.

These second order APC (Linkwitz Riley) slopes, which produce composite slopes that are pretty much third order.  The cross over points are 350 Hz and 3 kHz.  This allows for the band pass to be 3 octaves, encompassing most of the speech discrimination band.  Minimum impedance is five ohms.  There is optimal diffraction compensation.  There is a slight peak centered at 650 Hz from the mid range driver of 3 db which has not been notched.

I would feel inclined to build the speaker with a narrow top and broad base.  It will not matter if the band pass enclosure is over sized.  I would put the tweeter at the top, with the band pass driver below, and the a board below that to make the top of the speaker enclosure the tweeter/band pass enclosure, and have the bass enclosure below that.  Quarter round should be placed as trim all round the edge of the front panel.  It should be an attractive good performing speaker.

This design is a two way.  Here is the box alignment for the woofer.

Note that the driver and port will displace 0.0408 cu.ft. in the enclosure, this will have to be added to Vb.  To get to Vt you will have to add brace volumes as well.  Mineral wool (Rockwool) should be placed on the back surface behind the driver.  50% of the internal surfaces should be covered with Polyfill.  Damping is included in Vb.

This is the crossover.  Chokes should be air core. L1.  L2.  The value is 1.5 mh, but this is close enough to 1.6 mh.

C1 and C2.  Ce.

Rp1.  Rp2.  Req.

The rise below 1 kHz is intentional to correct the diffraction loss of the cabinet.  The acoustic response is for a driver on a baffle, so when loaded the rise will continue to cut off as intended.  These Vifa tweeters have a slight rise in response at 15 kHz but there is no need to notch it.

The crossover point is at 2.8 khz and both drivers are down 21 db an octave either side of crossover.  The tweeter has an Fs of 1500 kHz and ideally the tweeter should be a little further down at that point, but I think the result will be satisfactory.  This could really only be corrected by selecting a tweeter with a lower Fs.

With the diffraction compensation these speakers have to be considered essentially five ohm.  The phase response is superior and the speakers are only 90 degrees out of phase at crossover.

When the boards are constructed the inductors should be spaced from each other as far as possible and their axes at 90 degrees to one another.

This is the port you will need, you will have to cut to length.

The Audax Aerogel drivers are excellent mid bass woofers.  However they have a big peak first break up mode, at 3.8 kHz of 9db in magnitude.  This is associated with a rise in response at 1kHz.  This very large peak requires notching out.  However with careful crossover design, excellent performance is obtainable from this driver.  At first sight this driver does not look promising, but with notch filter and tweaking the Qs of the filters superior performance is possible.  A speaker with good bass performance and excellent smooth detailed mid range is posible, in a very cost effective speaker.

Last fall while in England, my father asked me to put together speakers for their sun room.  There are always a collection of drivers around my parent’s house.  I used the Audax AP170Z0 and the Scanspeak D2905/95 tweeters.  I used these because they were handy.  A superior speaker resulted from this design.

Here is the woofer alignment, for an optimal 1 Cu. ft. box.

Here is the alignment for a smaller 0.43 cu.ft. box

This is the Crossover Circuit.

I have modified the circuit for the Vifa D27TG 05/06.  This is available from parts Express.

The driver has an F3 of  46Hz in a 1 cu.ft box.  This is good performance, although the driver is displacement limited from 50 to 110 Hz. In this range spl is limited to 100db.  above that spl. of 107db is possible.

There are two impedance humps at 30 and 75 Hz, with the minimal impedance at F3, so tuning is optimal.

A vent flared at both ends, 3″ in diameter, six inches long, slows air velocity to 18 m/sec.

The crossover is electrical second order, however it combines with the driver slopes to make a composite fourth order filter.  Both tweeters are down at least 24 db at resonance (Fs).

The woofer impedance is equalized by Req and Ce and the break up mode peak dealt with by Rm, Lm and Cm.

16 SWG air core inductors  should be used for L1 and L2.  A good quality iron cored inductor should be used for Lm.  Good quality polypropylene caps should be used, such as Solen caps.  Resistors should be wire wound 15 watt.

The phase response of the crossover is unusually good.  The mid band response is excellent, including across the crossover region.  Some degree of diffraction compensation has been achieved, about 3db.  This is usually what is achievable without adding a second driver.  Room gain should in any event do the rest, unless the speaker is a very long way away from room boundaries.

The impedance is 5.5 ohm though most of the range with a peak to 24 ohms in  the crossover range.  These speakers should be regarded as 6 ohm speakers.

Allowing for component insertion loss, notching the woofer peak, and providing for some diffraction compensation, the sensitivity of the speakers is 86db 2.83 volts at one meter.  This is very typical for a two way using drivers of this size.

This makes a very nice speaker.

I have also worked out a crossover that has minimal changes for the SEAS 27TDC.  This tweeter is about $10 more, but well worth it.

If you want to do a two and a half way tower, then here is the optimal box alignment with an F3 of 46 Hz.

I have designed a crossover using the Scanspeak tweeter.  This should be a very good speaker and well worth the cost of the Scanspeak tweeter.  The diffraction compensation starts at the optimal point of 600 Hz, and provides +6db of compensation for the diffraction loss by 175 Hz.  This speaker should have good robust tenor register.

Here is the 2.5 way crossover using the SEAS 27 TDC tweeter.  The phase response is excellent.

I’m adding and MTM design for this driver with a choice of two tweeters.  This requires a third order crossover at 1.8kHz.

Here is the box alignment.  Allowing for the volume of driver crossover and braces,the final volume Vt should be around 1.3 cu.ft.  The port should be 4″diameter X 10″long flared at both ends.  You can also use the two cu. ft. box from the two and a half way tower, above, for extended bass.

The crossover circuits for the Vifa D27TG 05/06  and the SEAS D27TDC are the same.   The SEAS D27TDC is excellent value for money, and in my view worth the slight extra cost.

This is the response with the Vifa D27TG 05/06

This is the response for the SEAS D27TDC

Any of these designs should make an excellent set of speakers.  The crossovers for the MTM set up should have optimal lobing for this configuration.  Vent velocity of these MTMs is an excellent 18m/sec.

Allowing for insertion loss, and notching the woofer peak, overall sensitivity of these MTM speakers will be 90 db 2.83 volts 1 meter and 87 db 1 watt 1 meter.

The impedance is very uniform at 4 to ohms throughout, except for a slight peak t0 15 ohms at crossover.  This design is impedance compensated and should be a pretty easy load for any amp or receiver able to drive a four ohm load.

50% of the internal surfaces of these enclosures should be covered with a Rockwool like product or Black Hole.  The internal surface of the back of the enclosures should be fully covered.

Any of these speakers if properly constructed should give results equivalent to speakers in the 1 to 2 K range per pair.

Here is a parts list and sources, for the two and a half way with the Scanspeak D29.  The component values that change when using the SEAS 27 TDC tweeter are in the brackets, and those alternate values that change when using that tweeter can be found by clicking within the brackets.  Note the specified values and source values in some cases differ slightly.  However there is no significant change in performance.

C1   Two required

C2   Omitted

C3   Two required.  (version with SEAS 27 TDC tweeter)

C4   Two required

C5   Two required

Ce   Four required

Cm  Four required

L1   Two required

L2   Omitted

L3   Two required (version with SEAS 27TDC tweeter)

L4   Two required

L5   Two required

Lm  Four required

Rp1 Two required (version with SEAS 27 TDC tweeter)

Rp2 Two required (version with SEAS 27TDC tweeter)

Req Four required

Rm  Four required

Circuit Board  Two required

Terminal cups  Two required

Ports 4″ flared  Two required

The total cost of the above list is $323.94

Crossover parts for the MTM.  Note that the parts for the Vifa and SEAS tweeters are same.

C1

C2

C3

Ce

Cm

L1

L2

L3

Lm

Req

Rm

Circuit Board

Terminal Cup

Port

The cost of this MTM crossover and other parts is $130, so for a pair, $260, for mains and center $390.

This is the parts list for the crossover for the 1 cu. ft and 0.43 cu.ft book shelves.  This is for the Vifa and SEAS tweeters.  The different values for the Seas tweeter are in brackets.

C1

C2

Ce

Cm

L1 (SEAS 27TDC)

L2

Lm

Rp1 (SEAS 27 TDC)

Rp2

Req

Rm

Circuit Board

Terminal Cup

Port 0.43 cu. ft.

Port 1 cu. ft.

The cost is around $100 each.  So two mains or surrounds $200.  Two surrounds and rear backs $400.

So the total parts cost for a system using 2.5 way mains, MTM center and four bookshelves is $1228 using the Vifa tweeter and $1298 using the SEAS.

Using MTM mains and centers the cost is $1164 using the Vifa tweeter and $1234 using the SEAS tweeter.

So the most expensive system averages $185 per speaker for all parts, and the cheapest $166 per speaker.

So building with MDF, you should be able to build two towers, a center and four surrounds for around the $1500 price point, which is outstanding value.

This combination works best with a fourth order Linkwitz Riley crossover.

Here is the vented woofer box alignment.

MTM CONFIGURATION

Here is a vented box alignment for two Dayton RS 150S-8s.

Note that it requires a 3″diameter vent flared at both ends 7.25″ long.  This gives a max air vent velocity of 20 m/sec.

The max. spl is 109db, however output is limited by driver excursion from 50 to 100 Hz, reaching an spl of 103db at 65 Hz.

The cabinet should be well braced.  The volume displaced by the drivers, braces and crossover should be added to Vb to come up with Vt.  A rule of thumb estimate is Vb + 15 to 20%.

Place the drivers as close together as possible.

Half the internal surface of the enclosure should be covered by acoustic absorbing material.  The back wall should definitely be covered.  Rockwool type products are best.

The vent can be placed on the front or back.  Keep the vent 4″ away form any wall boundaries and drivers.

Here is the crossover for two Dayton RS 150S-8s in MTM configuration with the Beston RT002A.

If you want to notch the 15 kHz peak of the tweeter, use this parallel notch filter in series with the tweeter.

C =  2.002 µF
L =  0.05 mH
R =  7.95 ohms

Note: R should be adjusted by sub-
tracting from it the DCR of the coil.

Put the above components in parallel and out the parallel network in series with the tweeter.  At the high frequency range of the peak centered at 15 kHz, I doubt the sonic effects of this peak will be very noticeable.  I would build the speaker without this notch filter first and see how it sounds.

The crossover is third order for this MTM configuration, which will give the correct lobing tilt for this MTM configuration.

This speaker is modeled at the request of Loren42.

The woofer is the Dayton DC380-8.  This driver is available from Parts Xpress.  This has an F3 of 30 Hz in a 5.5 cu.ft cabinet tuned with a single 4? diameter port 9.2 inches long flared at both ends.  Spl is 111 db.  The speaker is slightly limited by xmax between 30 and 55Hz, however overall performance is excellent.  The vent air speed velocity is 18 m/sec so there should be no issues with vent chuffing.

The mid range cabinet should have all walls lined with mineral fiber such as Rockwool.  The cavity should be filled with Polyfill without compression.

The bass enclosure should have 50% of each panel lined with 4? thick Rockwool.  Special attention should be payed to placing Rockwool on the panel behind the driver.

Here is the box alignment.

The Crossover is a three way all-pass Linkwitz Riley second order.  The composite electrical and driver slopes are third order 18db per octave in the low pass/band pass filter and fourth order 24 db per octave in the band pass/high pass filter.

Zobel networks have been provided to equalize the impedances of the LF and band pass drivers.

The woofer has a sharp cone break up peak at 1500Hz which has had to be dealt with in the woofer compensation network.

The mid band response with this network is excellent and unusually smooth for inexpensive drivers with this network.  With the polarity of the band pass driver inverted, the phase response is excellent.  Group delay is very acceptable.  The impedance curve has been equalized and this driver should be a very easy amplifier load, and not cause any problems.

Allowing for insertion loss of the network, the sensitivity of these speakers should be 92 db 1 watt I meter.  This accounts for the high spl.

As is is typical of three ways using a large woofer, the crossover network is complex with a part count of 20 components per crossover.  Because the low pass/band pass crossover has to be at 400Hz,some inductor and capacitor values are high.  This cost of the components for these crossovers will be significant.

The ports and all crossover parts are available from Madisound.

Even though  the drive units are all in the lower price range, with a properly braced  and damped enclosure and this crossover network, this should be a superior speaker.

Here is the alignment for a Peavey 15 black widow in a 6 cuft box.  It requires 4, 4inch diameter vents flared at both ends, 11.4″ long.  Optimal box id 2.2 cuft.

Here is a simple simple cost effective bookshelf speaker design that will yield superior results compared to commercial offering from manufacturers at similar or greater price tags.  The performance of this speaker should be superior to the sum of the parts.

 

I chose the above drivers carefully to transition well together with a low part count in the crossover.  I have selected a small Vifa polypropylene woofer.  The on and off axis response is excellent, and there is nothing troublesome with the out of band response.  There is a small I KHz peak and as is the norm with small polypropylene bass/midranges a step response.  Here is the manufacturer’s specification.

 

The tweeter is by Morel.  This is one of their cheaper offerings.  The roll off and dispersion characteristics are excellent.  Fs is 900 Hz.  This is the full specification.

 

The crossover needs to make a smooth transition at crossover without ripple, correct the step response, as far as possible take care of response irregularities.  It should have a respectable, impedance, phase, and time response.  It should also be the most elegant solution with the smallest part count compatible with achieving goals.  These crossovers have five components on each board.

 

Now this crossover has a combined fourth order acoustic and electronic slopes.

The crossover is very symmetrical without ripple.  As you work with a design you find the design begins to tell you where the crossover needs to be.  In this case it is 3 KHz.  This is a very good place for a two way crossover point by the way.  There is no zobel impedance equalization.   This is for a good reason.  I took advantage of the rising impedance to correct the step response.  The low pass filter is in fact first order over most of it operative range.  It changes to second order.  Now please note that the program does not let me write in and show R1.  If you look at the component values you will see that C2 shows an internal resistance of 4 ohms.  No cap has this value, so you need to put a 4 ohm resistor in series with C2.  This is VERY important.  This resistor is operative in the model.

 

The HF filter has the Q of the filter aligned to combine with the acoustic roll off of the tweeter and make for symmetry with the woofer response and make a very smooth transition.  This crossover also optimizes the off axis response of the speaker.  The tweeter is 33db down at F3, which is excellent.   This filter also switches order.

 

The step response is corrected.  A small remnant of the small woofer peak remains, however the Q of the peak is changed.  It is lower in magnitude and moved down to 750 Hz.  It is 400 Hz broad from 600 to 1000Hz, and less now about 2db.  I have made the judgment that in that range and at that magnitude it will do no arm.  Also I suspect that if the speaker is around 10 inches from room boundaries that the response below the slight peak will be lifted by that small amount and help compensate for cabinet diffraction loss.

 

A word about sensitivity,  note that the average sensitivity is now 86db 1 watt one meter.  That is because with any passive network does not allow for boosting a signal, only attenuating it.  This reduction in sensitivity is a consequence of correction of the step response.

 

Now impedance.   Now the bass curve will be the one shown in the woofer alignment.  The published spec is sealed, and has one impedance hump.  This woofer requires reflex loading and there will be two impedance humps.  One is at 20 Hz the other at 73Hz.  There is a dip to 6 ohms between the peaks.  Now although these are 8 ohm drivers, correcting the step response, which in my view is essential, always drops the impedance.  The impedance is 6 ohms from 200 Hz to around 650 Hz and then rises.  This is where a good deal of the power is, so regard these speakers as 6 ohm.  There is an impedance rise to 14 ohms in the crossover region.

 

These speakers should be an easy amp drive.  Any amp the over heats driving those, should never have seen the light of day.

 

Now to phase, this crossover puts woofer and tweeter out of phase at crossover.  There is an unusually good phase and time response.  The shift at crossover is 2.2 inches or 0.17msec.  Now a woofer�s acoustic center is the geometric center of the cone, which for me is impossible to visualize and certainly calculate.  However the tweeter will be ahead of the woofers acoustic center, so will modify this.  I would start with the wiring as shown, but when the speaker is constructed see which polarity has the greatest output at crossover.  I have a hunch that with the drivers lined up on a flat panel recessed flush, the polarity switch will not change the output.  If that is the case, I would wire the tweeter in phase.  This is something that is hard to predict from modeling.

 

For the crossover use good quality air cored inductors and mount them as far away from each other as possible, with one horizontal and the other vertical.  This will minimize cross inductance.  Please select polypropylene caps.

 

This should be an easy low budget speaker to construct.  I would welcome comments from anyone who builds a pair.

This is a mod for the Polk RT 3 speaker.  It uses this woofer.  This is a pdf. of its specification sheet.

It uses this tweeter.   Here is the spec. sheet.

This is the woofer alignment.

This is the crossover pdf and simulations.

The crossover is at 3 KHz.  However the component values have been significantly modified. There is 2 the 3 db of diffraction compensation and the response irregularities of the woofer between 200 and 2000 Hz have been significantly blunted.

L1 and C1 form the high pass filter.  This starts to attenuate first order at around 6.5 KHz and switches to second order around 1200 Hz.  The tweeter is down 33db at resonance.  This should mitigate against any tweeter roughness.  Rp1 and Rp2 pad the tweeter output.

L2 and C2 form the low pass filter.  This starts as a first order filter around 400 Hz and starts to perform diffraction compensation.  It changes to second order just before crossover at 3 KHz.   Req and Ce perfrom impedance compensation.  Without it there is significant rise in response above crossover.

Note that providing diffraction compensation has sacrificed about 3 to 4 db of driver sensitivity.  Although the sensitivity is around 87db 1 watt 1 meter which is good for a small speaker like this.

There are impedance peaks of 50 and 40 ohms as a result of reflex loading at 25 and 100Hz respectively.  Because of the equalization of diffraction and  smoothing of the response the impedance is 6 ohms over most of the operating range.  There is a rise to 12 ohms at crossover.

The phase response with the polarity of the tweeter reversed is excellent. with the drivers having a maximum pahse angle of 45 degrees in the crossover region.  Driver offset of the front baffle will modify this a little.  As  result group delay is only significant on the driver tuning range.

The existing vents should be made 7.62 inches each.

The crossover can be mounted in and out of the cabinet.

This mod to the RT 3 should be able to be accomplished with minimal cabinet modification.

If a bigger box were to be built, then F3 could be lowered to 59 Hz.

Here is a speaker design for novice builders.  I have called it NASP (Noob Audiophile Speaker).  It is built round the SEAS: –

29TFF/W (H1318) Fabric tweeter, price $43.9 each, and the Peerless PPB-6.5″ Polycone woofer PPB 830874.  This woofer is now renamed, so there is a discrepancy in the name on the simulations, however it is the same woofer. Price is $57.9.  The drivers are available from Madisound

This is a good beginner’s project.  The impedance is very uniform at 8 ohms and will be an easy load for ANY amp.

I designed this for an experienced builder for his brother in law to do his first project.  Results were highly favorable.

The crossover consists of a third order Butterworth low pass filter, formed by L2, L3 and C2.  The Zobel network that corrects the impedance rise, so the low pass filter can work correctly is formed by Req and Ce.  Rm, Cm and Lm can be omitted, they just flatten the impedance curve.

The high pass filter is a second order Linkwitz-Riley formed by C1 and L1.  Level matching is accomplished by the L-pad Rp1 and Rp2.

The crossover is nice and smooth.  Time and phase aberrations are minimal and very acceptable.

The box is a fourth order BB4 0.5 cu.ft. ported reflex enclosure.  The F3 is 51.5 Hz.  There is no ripple and QL is 7 so the bass will be tight without being over dry.  The box though small should be well braced.

Here are the pdf. files of the box and crossover.

nasp-bassbox-pro.pdf

nasp-crossover.pdf

Please note that this is a beginner’s project.   It should be straightforward to build.  All crossover parts can be obtained from Madisound.

The design, in order to have a very flat 8 ohm impedance curve, is not diffraction compensated.  In most rooms best results will be achieved of the speaker is not too far from room boundaries.