# Passive Radiator EX-PR15 Econowave Design



## Navydoc (Feb 8, 2009)

I built a 24" sealed Mal-X, Gen II sub last summer. It sounds outstanding, but now I am unhappy with my main speakers (Paradigm 9seMkIII's). I thought about using my Magnepan MMG's for HT duty, but decided to build some L/C/R's instead.

Current plan is to build waveguide speakers that are widely discussed on the speaker forums. My plan calls for a 3 cu ft cabinet (only set dimension is 17" width so I can use a passive XO developed by users over at the PE Tech Talk Forum). The LF's will be covered using an Eminence Kappalite 3012LF Neo 12" Driver coupled with a B&C DE250-8 1" Polyimide Compression Driver in a QSC waveguide (PL-000446-GP) [aka Deluxe Econowave].

While playing with UniBox, I plugged in the parameters from Kevin's EX-PR15 and the results for the low end look very good (not that I need it with the Mal-X, but the lower I can x-over w/ my Onkyo 805 the better). I do not know much about speaker design, :huh: I am more of a copier of other peoples plans (thanks NeoDan and WillyD for the inspiration for my subwoofer). However, I have not seen a build of an econowave using a PR.

Attached are the plots comparing sealed to PR. I bought all the tools to build to sub, shame to see them getting fat and out of shape.

Best,
SWN


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## vann_d (Apr 7, 2009)

If your plots are correct, you are not gaining much with the PR because you are exceeding x-max south of 70Hz either way.


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## looneybomber (Sep 20, 2006)

Single PR is a bad idea, especially on a speaker that will be mounted on a stand. You're asking for a tumble. That's why you don't see any econowave builds with a passive radiator. Use a port.


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## Navydoc (Feb 8, 2009)

looneybomber said:


> Single PR is a bad idea, especially on a speaker that will be mounted on a stand. You're asking for a tumble. That's why you don't see any econowave builds with a passive radiator. Use a port.


I couldn't get the port to model for me (very limited experience with the software as I couldn't change the port size). On another forum a more skilled individual plugged the 3012LF into WinISD for a 3 cu.ft. box (net after you subtract the volume of the horn, drivers and braces) with a 4" diameter port tuned to 40 Hz (4" long port), 35 Hz (6.2" port) and 30 Hz (9.5" port). Looking at the graphs he suggested going with the 35 Hz tune as room gain should bring up the gentle droop.

Ported would be less expensive to build. I will attempt to learn more about the software over the next week or so.

Thanks, I am trying to gather as much information as possible.


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## lsiberian (Mar 24, 2009)

Navydoc said:


> I couldn't get the port to model for me (very limited experience with the software as I couldn't change the port size). On another forum a more skilled individual plugged the 3012LF into WinISD for a 3 cu.ft. box (net after you subtract the volume of the horn, drivers and braces) with a 4" diameter port tuned to 40 Hz (4" long port), 35 Hz (6.2" port) and 30 Hz (9.5" port). Looking at the graphs he suggested going with the 35 Hz tune as room gain should bring up the gentle droop.
> 
> Ported would be less expensive to build. I will attempt to learn more about the software over the next week or so.
> 
> Thanks, I am trying to gather as much information as possible.


You have a very good sub all you need is an 80hz crossover point. Get a pair of Exodus Anarchy drivers and a nice tweeter and you're set. Start simple. Once you get simple down move on to harder stuff. Designing a speaker is a tricky business that takes knowledge, experience and intuition. Give it time and you'll have enough information to do the deed. But pace yourself. Subwoofers are easy.

Speakers require extensive bracing and dampening to do their best.


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## Navydoc (Feb 8, 2009)

lsiberian said:


> You have a very good sub all you need is an 80hz crossover point. Get a pair of Exodus Anarchy drivers and a nice tweeter and you're set. Start simple. Once you get simple down move on to harder stuff. Designing a speaker is a tricky business that takes knowledge, experience and intuition. Give it time and you'll have enough information to do the deed. But pace yourself. Subwoofers are easy.
> 
> Speakers require extensive bracing and dampening to do their best.


I spent all evening modeling the Kappalite 3012LF driver using "The Woofer Box and Circuit Designer" Ver 4.5 (http://audio.claub.net/software/jbabgy/WBCD.html). After many trials and error, I landed on a sealed 1.65 cu ft box.

I am going sealed instead of ported because 1) I have a good subwoofer and 2) the model always exceeded 10 mS air velocity by 70 Hz with 130 W amplification (4" port, tuned at 35, 40 or 45 Hz in 2.0 to 3.0 cu ft cabinet). The sealed 1.65 cu ft design has a max output of 115.07 dB w/ 130 W input; relative - 3 dB point of 86.62 (- 6 and - 10 dB points of 59.14 and 42.03, respectively). Since I will run the speakers in a home theater setup with an 80 Hz high pass filter this bass response should be fine.

At 130 W the cone excursion does not exceed Xmax at any frequency (Xmax is exceeded at 40 Hz and 70 Hz w/ 200 and 450 W, respectively).

Overall, the design should be relatively easy to build as the crossover has been developed and by not insetting the front baffle i can add plenty of bracing and still have an internal volume of 1.65 cu ft.


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## looneybomber (Sep 20, 2006)

"the model always exceeded 10 mS air velocity by 70 Hz with 130 W amplification"
You're crossing over at 80hz right? Model it with that 80hz HPF in place and then see what happens.
Another thing you could do is to tune it higher, which will enable you to use a larger diameter port of the same length. Having a larger port will reduce air speed...and by the way, 10m/s is not bad at all! Over 20 and you should worry.


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## Navydoc (Feb 8, 2009)

looneybomber said:


> "the model always exceeded 10 mS air velocity by 70 Hz with 130 W amplification"
> You're crossing over at 80hz right? Model it with that 80hz HPF in place and then see what happens.
> Another thing you could do is to tune it higher, which will enable you to use a larger diameter port of the same length. Having a larger port will reduce air speed...and by the way, 10m/s is not bad at all! Over 20 and you should worry.


Yes I will be crossing over at 80 Hz. I went back and modeled the 1.65 cu ft cabinet that Zilch used over on the PE forum (PE Sku 245-325). In this cabinet tuned at 45 Hz (Port: 4" dia, 7.17" length) the cone excursion does not surpass the Xmax at 450 W input (the rating for the driver). The vent air velocity reaches 5 m/s at ~85 Hz and 10 m/s at ~68 Hz. Freq response stays flat to 60 Hz (-3 dB = 48.38; - 6 dB = 41.61; - 10 dB = 35.8).

This cabinet tuned to 35 Hz (4" dia, 13.77" length) the cone excursion surpasses the Xmax at 450 W input at 70 Hz. The vent velocity is lower than the 45 Hz tuning, 5 m/s at ~68 Hz and 10 m/s at 50 Hz. Freq response stays flat to ~90 Hz (-3 dB = 59.14; -6 dB = 42.03; -10 dB = 32.05).

With 200 W input, neither excursion or vent air velocity appear to be a problem for either cabinet tuning. I plan on using a 130 W/ch Onkyo 805 receiver, so i should not be albe to hear port noise from my seat (13 ft away).

I am thinking the 45 Hz tuning looks better than the 35 Hz tuning (with 40 Hz stradeling the two). Am I missing anything important?


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## Lucky7! (Jan 7, 2008)

If you can added specific active EQ, then a 46L net sealed box with a Q=1 HPF at 80Hz get this. Ignore the F3=92Hz on the graphs as it's around 80 looking at the numbers in the curves directly.


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## Navydoc (Feb 8, 2009)

A9X said:


> If you can added specific active EQ, then a 46L net sealed box with a Q=1 HPF at 80Hz get this. Ignore the F3=92Hz on the graphs as it's around 80 looking at the numbers in the curves directly.


I am not planning on active EQ. The EBP (Fs/Qes) for the driver is 108.88 and the Qts is 0.324, both are in the range recommended for a vented box. Looks like in the 1.65 cu ft enclosure vent air velocity will be below 5 m/s w/ 200 watts amplification (my largest amplifier). The driver manufacturer spec sheet indicates it will work well in either design.

QSC waveguides arrived today, now I just need to scrape up the funds to buy the drivers and XO parts.


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## Lucky7! (Jan 7, 2008)

Navydoc said:


> I am not planning on active EQ.


Fair enough. As I don't bother with passive xovers any more it's a standard development path for me to look at application specific EQ, and that just popped out as obvious to me.

Now, if you weren't running a sub, with 6th order assisted you could get about 35Hz...


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## Navydoc (Feb 8, 2009)

A9X said:


> Fair enough. As I don't bother with passive xovers any more it's a standard development path for me to look at application specific EQ, and that just popped out as obvious to me.
> 
> Now, if you weren't running a sub, with 6th order assisted you could get about 35Hz...


Thanks for the input, I need to look into active XO's at some point. They appear to offer a lot of flexibility for not that much cost (learning curve seems a bit steep).


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## Lucky7! (Jan 7, 2008)

Navydoc said:


> Thanks for the input, I need to look into active XO's at some point. They appear to offer a lot of flexibility for not that much cost (learning curve seems a bit steep).


I reckon the learning curve is much less for an active, especially something like the DCX as you can dial in adjustments on the fly. Passives are much easier now to design with specialist CAD design tools, but still more work and can never do as well some of the things active can.

A friend who was definitely a non believer borrowed one of mine to experiment with adjusting the passive xover in his system and was rapt with how quickly and easily he could try things and the speed with which you could test two options. He has one again at the moment because he has a new midbass and wants to work out what he wants before committing the design to an analogue electronic unit.

I see a lot of passive DIY designs out there and wonder if the designer has chosen xover points and slopes arbitrarily because of what looks good in the sims, or tested many variations. My guess is the former as it's so hard to compare xovers in terms of logistics as well as costs for all those components.

Sorry for the sideline; all the best with your build and I'll watch the development and results with interest.


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## Navydoc (Feb 8, 2009)

Here is a scale drawing of the overall design. To maximize space for internal bracing, and to look interesting, I will mount the QSC waveguide in a 1.5" baffle coupled to a parts express trapezoid speaker enclosure.

I have received the 3 QSC waveguides but will not not be able to start building until late spring due to job-related travel.


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## Zilch (May 18, 2010)

A9X said:


> Now, if you weren't running a sub, with 6th order assisted you could get about 35Hz...


Thanks for the reminder; that was my intent, but I've forgotten to turn it on anytime since the pair were complete.... :duh:


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## Lucky7! (Jan 7, 2008)

Zilch said:


> Thanks for the reminder; that was my intent, but I've forgotten to turn it on anytime since the pair were complete.... :duh:


I've finally decided what I'm going to do for surrounds and am looking forward to further testing my JBL2225 and Beyma 15G40 in this alignment. Early tests were promising but the secondhand boxes I used were rubbish. DJK has been recommending this for years and he's been spot on with everything else he's suggested and I've tried so far. Will likely need to tweak the LF EQ to compensate for near wall placement.

Based the design around Troel's PMS but wider and deeper in the centre to accommodate the 15" drivers. Have ripped enough ply for the front and rear of 6 speakers and will hopefully get to the ribs this w/e. The planned 3 way Ewave style MF/HF doesn't sound as good to me as cones'n'domes in an WMTM here, so pair #3 might be that way for the bedroom speakers.


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## Zilch (May 18, 2010)

All of my 2225s got converted to 2235s, and the next pair I get will become 2234s. DO have a pair of E145s that might be worth pursuing, tho.

Generally, I'm getting good results building eWaves with 12" and 10" woofers in modest-size cabs. The small 6.5" and 8" ones are fun builds, too. I have a poo-pot of small vintage cabs I scored last summer to use for those.

Y'all exploring various tunings for 3012LF is very helpful; I'm going to have to settle on something final for my EconoWave Deluxes and finish them here soon, as they are definitely keepers.... :T


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## Navydoc (Feb 8, 2009)

Still finalizing the design (I know, I need to stop playing on the computer and cut wood!!!!). I will be home for nearly three months soon :clap::clap::clap: - so I need to finalize the build plan.

I'm attaching the most recent iteration of the design. I am not going to use the Parts Express trap for the bass cabinet, instead I am building out of 13-ply birch w/ 1.5" x 1.5" poplar as a scaffolding for rdgidity and glueing aid.

I have decided for sure on a 35 Hz vented cabinet w/ 2 3" ports (w/ 40 Hz high pass filter maximum excursion is less than 5 mm and air vent velocity is less than 5 m/sec [via Bagby Woofer Box Model, ver 4.5]).

Zilch - Thanks for posting on my thread. Do I need to worry about boosting the low end? It looks pretty good to my untrained eye.:help: 

Thanks,


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## Zilch (May 18, 2010)

Navydoc said:


> Do I need to worry about boosting the low end?


Not if using with subs, I shouldn't think....


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## Navydoc (Feb 8, 2009)

Zilch said:


> Not if using with subs, I shouldn't think....


Thanks Zilch, I cannot wait until June so the sawdust can fly! Per the thread title I was going to use a 15" PR for the design, but didn't seem to gain any performance over vented.


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## Lucky7! (Jan 7, 2008)

Navydoc said:


> instead I am building out of 13-ply birch w/ 1.5" x 1.5" poplar as a scaffolding for rdgidity and glueing aid.


You're going to need more bracing of the panels. The corners are already the strongest and with nothing to stop them, the panels are going to flex in the centre like a drum.


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## Navydoc (Feb 8, 2009)

A9X said:


> You're going to need more bracing of the panels. The corners are already the strongest and with nothing to stop them, the panels are going to flex in the centre like a drum.


Thanks for the input. I will have pretty extensive bracing as shown in the attachment. When sizing I made the cabinet larger than I modeled so that I have plenty of room for bracing (will keep track of cu ft of bracing so as not to screw up the tuning freq). The bracing will be asymetrical to assist with resonance.


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## Lucky7! (Jan 7, 2008)

Zilch said:


> All of my 2225s got converted to 2235s, and the next pair I get will become 2234s. DO have a pair of E145s that might be worth pursuing, tho.


I bought mine for about half the cost of a 3012LF new here, and I know their entire service history (permanent install, know the maint engineer who took care of them). They were bought for a Jack Bouska like project, supplanted by the AE TD15 drivers in that and being great drivers, I can't bring myself to sell them, so into the surrounds they go. Definite overkill here, but that never hurt and the price is right.

I did at one stage think about a 2235 conversion. Then I saw the cost of the JBL parts to do it here....



Zilch said:


> Y'all exploring various tunings for 3012LF is very helpful; I'm going to have to settle on something final for my EconoWave Deluxes and finish them here soon, as they are definitely keepers.... :T


If I were starting from scratch again today, the Ewave deluxes would be of great interest to me except in the surrounds. Here I'm going for wide dispersion.


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