Cheap 'n' simple 2x10 top?

[Brian Steele]

Intended use: a pair of tops (>100 Hz) to be driven off a car audio amp, open-air venues small (<100 persons) crowd. Looking for high output and 4-ohm load. Doesn't have to be "hi-fi", but should be reasonably clean and clear.

Ideas so far:
http://www.parts-express.com/pe/show...-030&FTR=pa255
Dayton PA255 x 2

Eminence BH410 exponential Horn
http://www.parts-express.com/pe/show...Number=290-549

1" compression driver (haven't decided yet, but leaning towards one of the Seleniums)

Build - 44 l (net) sealed box, with the two 10's positioned vertically as close together as possible with the BH410 located between them. ~2.5 kHz x-over point, nothing too fancy. Pole-mounted to bring the BH410 up to ear level.

Sounds good?

[Paul O]

Sure... why not, use the DH200 and bring the crossover down to around the 2khz area to mitigate more of the cone breakup, should be plenty loud.

[Brian Steele]

Sure... why not, use the DH200 and bring the crossover down to around the 2khz area to mitigate more of the cone breakup, should be plenty loud.

The FR graph for the DH200 suggests that it dips almost 9dB by 10kHz before coming back up a few dB. A possible cancellation issue? It doesn't seem to have a phase plug - it's not mentioned in its description (like it is for other Selenium drivers). I might just pay the extra $4 or so and go with the D202Ti - http://www.parts-express.com/pe/show...number=264-455, which seems to have a smooth FR.

[Paul O]

Yes the 202 has a better highend response but less power handling, if you want to utilize all the potential in those 10s then you'll need a CD that can handle upwards of 150w assuming 6-7db of padding, if you use more it's not an issue of course. The DH200 is one tough driver, I installed some in a feedback riddled bar(all hard surfaces everywhere) that sees regular karoke abuse and these things simply won't die. They don't sound as bad as the graph would seem to indicated either.. nothing a little EQ couldn't dress up.

Now all that said I have D210s in my own speakers, response is very linear and there is definitely more highend extension. IMO you can't go wrong with any of these, if you really want to pinch pennies the DH200 will get the job done but there's no doubt you'll get a littler more extension for only a few dollars more with the 202s.. as long as it will handle the power you're gonna hit these cabs with. In my case the driver is only mated to a single 12 so it's padded down pretty heavily but you have dual 10s and output could be higher at the crossover frequency so the CD will see more wattage.

[Brian Steele]

Yes the 202 has a better highend response but less power handling, if you want to utilize all the potential in those 10s then you'll need a CD that can handle upwards of 150w assuming 6-7db of padding, if you use more it's not an issue of course. The DH200 is one tough driver, I installed some in a feedback riddled bar(all hard surfaces everywhere) that sees regular karoke abuse and these things simply won't die. They don't sound as bad as the graph would seem to indicated either.. nothing a little EQ couldn't dress up.

Now all that said I have D210s in my own speakers, response is very linear and there is definitely more highend extension. IMO you can't go wrong with any of these, if you really want to pinch pennies the DH200 will get the job done but there's no doubt you'll get a littler more extension for only a few dollars more with the 202s.. as long as it will handle the power you're gonna hit these cabs with. In my case the driver is only mated to a single 12 so it's padded down pretty heavily but you have dual 10s and output could be higher at the crossover frequency so the CD will see more wattage.

Thanks for the feedback. Some rough calcs suggest that my DIY "tops" (if SWMBO gives the go ahead to build them) are likely to see 100W or less from my system, so I think I should be OK with the D202. In any case, I'll be investing in some protection for them, just in case someone decides to be stupid with the volume control. I've seen some circuits online for this that look a lot more involved and useful than a simple inline lamp or polyswitch, and I'm tempted to give them a try.

[Brian Steele]

One more question - the horn I've chosen seems rather small. Is it really useful down to 2kHz, or am I worrying too much?

[Paul O]

Eminence says the lowest recommended crossover freq is 1.2khz so you're plenty safe.

[wg_ski]

The FR graph for the DH200 suggests that it dips almost 9dB by 10kHz before coming back up a few dB. A possible cancellation issue? It doesn't seem to have a phase plug - it's not mentioned in its description (like it is for other Selenium drivers). I might just pay the extra $4 or so and go with the D202Ti - http://www.parts-express.com/pe/show...number=264-455, which seems to have a smooth FR.

The FR graphs are for the driver on the specified horn. Change the horn, you get a different FR. Dips and cancellations like that can be just as much a function of the horn as the driver. The DH200 is a lot smoother on the HM2525, but loses top end above 10k. If you taper the response in the crossover, you can actually end up with a peak above 10k with the DH200/HM1725 - which can add some sparkle. How it will do with the Eminence horn is anybody's guess - until they measure it.

The DH200 does have a phase plug. Its design is quite a bit different, and not easy to see by looking down the throat becasue the VC/diaphragm is a ring radiator as opposed to the usual dome. It has a very small radiating surface which limits the low end, but a full 1.75" VC which gives good power handling.

[Randy L]

Have you looked at the Selenium Bi-Radial horn?
http://www.parts-express.com/pe/show...number=264-308

[Brian Steele]

Have you looked at the Selenium Bi-Radial horn?
http://www.parts-express.com/pe/show...number=264-308

I think I looked at a number of horns, including that one. I selected the one I did primarily for aesthetic reasons, I'll admit. The shorter I can make the baffle, the deeper the resulting box can be to achieve the same volume, so I'm aiming for the smallest distance possible between the two 10" drivers. I might even position the horn slightly to the side to make the distance between the two 10" drivers even smaller.

[wg_ski]

The flange on the 1725 horn is just a shell - not solid. If the 10's are recess-mounted, the horn flange can overlap the woofer flange and gasket a bit. This will tighten the CTC. You'll have to custom cut grills to do this, but you might be doing that anyway. A couple of the RFC horns have cutouts to minimize CTC, but then you're talking Real Money. I've taken a jigsaw to the Selenium 2525 horn to acheive the same end.

It looks like the Eminence horn was designed to stick in the center of a 4x10 bass guitar cab.

[Brian Steele]

It looks like the Eminence horn was designed to stick in the center of a 4x10 bass guitar cab.

That's correct. What I'm thinking of doing with it is rotating it 45 degrees, so it fits between to 10s mounted vertically. It's a 60x60 horn, so I think it might be possible to do so without any significant ill effects.

[steve22]

Have you considered using an Eminence co-axial driver for the woofer while it also serves as the horn for the HF driver? Your woofers can be very close together this way. You might also consider a 2.5 way setup like this.

[wg_ski]

That's correct. What I'm thinking of doing with it is rotating it 45 degrees, so it fits between to 10s mounted vertically. It's a 60x60 horn, so I think it might be possible to do so without any significant ill effects.

If anything, it will probably have a 'better' pattern oriented that way. With that design, I seriously doubt its directivity is constant in any one plane anyway.

[Brian Steele]

Looks like this project is getting more and more feasible. We're finishing up renovations at home here, and are likely to have a little housewarming party afterwards. It would be nice to have some speakers with decent SPL for the occasion, particularly as my current "amplifier" is a lowly 30Wpc into 4 ohms :-).

Three things are stumping me at the moment:

(1) The baffle design: I can't find a cutout template for the Eminence horn which I can use in my drawing program to conceptualize what the finished baffle would look like. I like to have a really good idea of what the end result is going to look like before I start cutting wood.

(2) The x-over design: Ideally I should buy the speakers, measure them in the baffle, then design the x-over accordingly. Even better would be if I can use an application to simulate the effect of a passive xover on the drivers. I'll look around to see what's available. And should I go with a 2.5 way design, or just a simple 2 way design?

(3) The Finish: This speaker is going to be used both indoors and out. Spray-on bedliner isn't readily available locally, and even then might not be the most pleasant-looking finish. I've got about nine(!) square yards of speaker grill cloth available for use, so I'm thinking about removeable grills - a cloth one for use indoors, and a metal one for when I'm using them as part of a portable DJ set.

[AMC]

(2) The x-over design: Ideally I should buy the speakers, measure them in the baffle, then design the x-over accordingly. Even better would be if I can use an application to simulate the effect of a passive xover on the drivers. I'll look around to see what's available. And should I go with a 2.5 way design, or just a simple 2 way design?

Jeff B's PCD will do just what you need. I'd stick with a 2 way for simplicity sake.

(3) The Finish: This speaker is going to be used both indoors and out. Spray-on bedliner isn't readily available locally, and even then might not be the most pleasant-looking finish. I've got about nine(!) square yards of speaker grill cloth available for use, so I'm thinking about removeable grills - a cloth one for use indoors, and a metal one for when I'm using them as part of a portable DJ set.

What ever looks good to you, it's your speaker, make it truly your own.

[Brian Steele]

Passively assisted?

The Dayton PA255 is an interesting driver in that the specs suggest that you'd need a pretty large box if you want to use a "maximally flat" alignment.

The driver's high Qms suggests though that a passively-assisted sealed alignment might be another way to get a bit more bass out of it without having to resort to using a big box.

For a Qb=1.1 alignment using the PA255, net Vb works out to just about 0.5 cu.ft, with Fc=106 Hz and F3=80 Hz. Some quick calcs suggests that adding 450uF of series capacitance (an ~$6 NP capacitor from PE) could flatten the passband and could drop F3 to 60 Hz.

60 Hz response and 94.5dB/2.93V/1M in a cabinet that's 0.5 cu.ft in size containing a 10" driver doesn't sound too bad... In fact, it might sound a bit too good to be true....

Could a passively-assisted vented alignment also work to get a little more low end out of this driver in a small box?

[Sydney]

Brian: The initial post :

Intended use: a pair of tops (>100 Hz)...Build - 44 l (net) sealed box, with the two 10's positioned vertically as close together as possible

Is probably what I'd do; Don't care for the sound of Qb=1.1 alignments; and wouldn't attempt to go for LF extension to 60Hz
Just opinions...

[Brian Steele]

Brian: The initial post : Is probably what I'd do; Don't care for the sound of Qb=1.1 alignments; and wouldn't attempt to go for LF extension to 60Hz
Just opinions...

With the inline capacitor, it will no longer sound like a Qb=1.1 alignment. The response at the low end will be more like a 3rd order system (which it is).

I've run a few sims through Akabak. Box size reduction and decreasing excursion below Fb seem to be the key advantages of using passive assistance for the PA 255. There's little or no gain in low-frequency performance (in fact, it drops off faster below the 3dB point). I have no idea how to fit the PA255 into a 12L box though, so maybe I'll abandon that idea .

Here's an idea of what one of the sims looks like. Note that I haven't included the effect of the capacitor's ESR. The result is a nice flat SPL response to just below 100 Hz.


Def_Driver 'D1'
dD=21cm dD1=3cm tD1=2.5cm |Cone
fp=1.3kHz
fs=46.4Hz Mms=34g Qms=9.64
Qes=0.48 Re=5ohm Le=1.33mH ExpoLe=0.618

System 'S1'
|Generator resistance
Resistor 'Rg' Node=1=2
R=1ohm
|Series Capacitance
Capacitor 'C1' Node=2=20 C=0.45mF
|Transducer
Driver 'Drv1' Def='D1' Node=20=0=30=40
|Radiation element
Radiator 'R1' Def='Drv1' Node=30
x=0 y=0 z=0 HAngle=0 VAngle=0
|Closed cabinet
Enclosure 'E1' Node=40
Vb=12L Qb/Fo=0.1 Lb=20cm

[Brian Steele]

Def_Driver 'D1'
dD=21cm dD1=3cm tD1=2.5cm |Cone
fp=1.3kHz
fs=46.4Hz Mms=34g Qms=9.64
Qes=0.48 Re=5ohm Le=1.33mH ExpoLe=0.618

System 'S1'
|Generator resistance
Resistor 'Rg' Node=1=2
R=1ohm
|Series Capacitance
Capacitor 'C1' Node=2=20 C=0.45mF
|Transducer
Driver 'Drv1' Def='D1' Node=20=0=30=40
|Radiation element
Radiator 'R1' Def='Drv1' Node=30
x=0 y=0 z=0 HAngle=0 VAngle=0
|Closed cabinet
Enclosure 'E1' Node=40
Vb=12L Qb/Fo=0.1 Lb=20cm

Improved a bit (fixed driver dimensions, incorrect Rg)

Def_Driver 'D1'
dD=21cm dD1=8.6cm tD1=4.8cm |Cone
fp=3kHz
fs=46.4Hz Mms=34g Qms=9.64
Qes=0.48 Re=5ohm Le=1.33mH ExpoLe=0.618

System 'S1'
Resistor 'Rg' Node=1=2 |Lead Resistance
R=0.25ohm
Capacitor 'C1' Node=2=20 |Series Capacitance
C=0.75mF
Driver 'Drv1' Def='D1' Node=20=0=30=40 |Transducer
Radiator 'R1' Def='Drv1' Node=30 |Radiation element
x=0 y=0 z=0 HAngle=0 VAngle=0
Enclosure 'E1' Node=40 |Closed cabinet
Vb=12L Qb/Fo=0.1 Lb=20cm



I'm still fudging my way through AkAbak (Lord, and I though HornResp had a difficult learning curve!), so there are probably a few more tweaks and corrections that have to be done. But the results do look interesting. FWIW, AkAbak predicts that the group delay peaks at 4.75 ms around 70 Hz, and excursion hits Xmax around the same frequency with just over 100W of power.