First 2-way build: Peerless 830869 8" and Seas 27TFFC in waveguide

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I tested the 830869 with a Selenium D220 coupled with a Pyle PH715 asymmetric horn. I'm quite happy with the results. A sample of my crossover can be found at Nightingale-V.

I'll be running more test, this time with a DNA350 compression driver and a selection of horns from DIY Sound Group. I think it'll be even better.
Hi Michael, it was partially your comments on the 830869 that ultimately gave me the confidence to buy them. So thanks for that. I'll take another look at your passive crossover to get a better idea of what you did.
 
Hi System7, thanks for your informative reply. A few questions/comments:

In the second simulation I posted, I used a 2.2mH coil and a 15uF cap to get the woofer breakup ~14-15db below the total output. Assuming this is not enough, what minimum suppression should I be aiming for?

...Which leads to my next question:by "overdoing" the shunt capacitor are you saying that 10uF is TOO large? If that's the case, I think I already know how you'll feel about the 2.2mH/15uF option.

I initially started my crossover simulations with a zobel (the same as IG81 recommended, or by using PCD's suggested values) and baffle step and everything, and this morning I went back to that. But I have not yet found a way to incorporate the zobel such that I get a good FR, good phase, AND any additional breakup control compared to 2.2mH/15uF. To get anything that looks good I have to resort to a single series coil in conjunction with the zobel (and then phase is bad anyway). This may all be due to the fact that I'm not yet using my own in-box measurements, and perhaps once I get started with those I'll see (or hear) what you're describing.

If serious rolloff is the goal, maybe I should put more attention toward the 24db crossover, despite the higher complexity and cost.

chaz, believe me, there is no problem getting steep rolloff on an 8" driver. In fact you often work to reduce it! :D

I'll show you below just how bad your 1.8mH/10uF bass filter is.

Next is what I would do as a start point with your Peerless paper cone using your highish bafflestep value and economically reusing the 1.8mH and 3.3uF. It is a 2.7kHz crossover .

Last is Troels' TQWT filter for comparison. It has less bafflestep. The 1uF tank capacitor value I use IS a bit of a moveable feast, as is the input resistor on the treble. :cool:
 

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System7, keep in mind that I have not yet purchased any crossover components, so there is no need to reuse any hypothetical values. But I appreciate the thought. :)

I am having a hard time interpreting the first graph you posted and why that should be in such stark contradiction with what CSD predicts for the same values. If 1.8mH/10uF is no good, I'm still unclear as to whether or not 2.2/15 is any better, or still on the wrong track.

Something else: I've been aiming for a ~1.5khz crossover for two reasons: to avoid the cone breakup as much as possible, and to reduce lobing issues between the 8" woofer and the waveguide. The crossover you're suggesting is aimed at 2.7k. Did you choose this crossover point to accommodate the 1.8mH coil, or for some other reason?
 
People always seem to think it's clever to use a low crossover point and joke first order filters. :confused:

Well, you may as well ask Troels Gravesen why he uses a serious 3.2 kHz crossover here. http://www.troelsgravesen.dk/JA8008.htm The clue is from Lynn Olson:

When working with rigid-cone drivers, there are some hard choices to make: if you lower the crossover frequency to minimize driver coloration, tweeter IM distortion skyrockets, resulting in raspy, distorted high frequencies at mid-to-high listening levels.

If you raise the crossover frequency to improve the sound of the tweeter, the rigid-driver breakup creeps in, resulting in a forward, aggressive sound at moderate listening levels, and complete breakup at high levels. (Unlike paper cones, Kevlar, metal, and carbon fibers do not go into gradual breakup.)

With the drivers we have today, the best all-around compromise is a 2nd, 3rd, or 4th-order (12-24dB/Oct.) crossover with an additional NOTCH filter tuned to remove the most significant HF resonance of the midbass driver.

I have no idea why "CSD" is getting the response so wrong. That peerless 830869 is a typical 8" 1.8mH Le paper driver with a bit of a peak at 3kHz.

Modelling the horn loaded driver has an element of guesswork on my part. It's not going to be a million miles away. The main thing it does is time align far better than on a flat baffle where the 8" plus 1" combination is very difficult to get right on simple filters.

As for lobing, build an MTM D'Appolito if you want to avoid it. Otherwise it's a fact of life in two ways.
 
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2.7kHz is where I have my 830869 acoustically meeting my tweeter (BMS 4540ND on JBL 6" PT waveguide) and I feel it works fairly well. I have a third order electrical filter and don't experience much breakup and it sound good up to fairly loud levels IMO. It really is as high as it goes as far as meeting my directivity requirements though. My tweeter does not want to play much lower than 2kHz as well, so I made it work there. :) I might tweak a few things if I have the time, mostly smoothing some areas.

IG
 
I too would recommend a lower crossover point to avoid lobing. Since that waveguide has a slight loading effect, below 2k shouldn't be an issue. A 24db slope or 12db plus tank circuit will be needed as I find it's best if breakups are -50 below reference.
 
I too would recommend a lower crossover point to avoid lobing. Since that waveguide has a slight loading effect, below 2k shouldn't be an issue. A 24db slope or 12db plus tank circuit will be needed as I find it's best if breakups are -50 below reference.
If you ask me, a lower crossover point is a no-brainer in this situation. The argument against a low crossover point is tweeter distortion, but based on zaph's distortion measurements with this waveguide, I don't think the lower crossover point will be any issue for the tweeter. MarkK found the same thing when working with the Seas DXT tweeter: he only used a first order electrical filter for the ER18DXT.

hornconversion-horn-hd-3.3uf.gif


-50db will be a tough nut to crack, but a lot easier to achieve crossing 1 octave below the breakup than on its doorstep. Anyway, enough time and energy has been wasted on discussing the crossover; let me get the drivers into a test cabinet first...
 
Update: while I haven't had any time since starting this thread to get going on my cabinets, I have spent more time playing with the crossover. I imported baffle and phase data, and the best solution I've found so far is a mixed electrical 3rd order/1st order. I modeled the response on-axis with the tweeter. Sensitivity is about 87db. The model requires 5 components: 2mH/20uF/.5mH for the woofer, and a 3.3uF cap paired with a 1ohm resistor on the tweeter. Any thoughts? I would have liked to avoid phase wrap but I couldn't make it work any other way.
 

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Hi chaz,
I use the 830869, initially in a two way with a Vifa tweeter passively, then two way active with a Vifa XT25G, and the last iteration is a three way active with a Peerless 832873 inserted.
As a two way passive, I found the 830869 as a very good driver, capable of fairly good bass (ported, of course) and able to handle the abuse better than the Vifa P21 woofers which I managed to blow up twice. I did say "abuse". :< )
Asfter converting one of the pair to active, after reading Rod Elliott's article about bi-amping, I was surprised at the difference. The active version made the passive sound muffled and I was happy with the the passives up until then. I only really went active to give myself something to do. It was well worth the effort.
The next bit probably isn't of use to you, however, the next step was to add a mid to the remanining passive and convert to active. Again, a significant improvement, mainly in ridding the vocals of any sibilance at all.
The bass of the 830869 can be really felt through the abdomen; there is no shortage. I offered pundip, a member also in Melbourne, for an audition. He was very impressed. That is the difference going active made for me.

This is what I used, mounted in the bottom of the boxes;
Linkwitz-Riley Electronic Crossover
Loudspeaker Protection and Muting
Single Chip 50W Stereo Amplifier
Baffle Step Compensation

Abs
 
Very glad to hear of your good results with these woofers, Abs. :) I was pretty confident about buying the 830869s based on other positive comments about the Nomex line. Your comment reminds me of what Troels says of the 6.5" woofers: "The 830875 drivers have a fairly high Fs and take some heavy beating to break in. And don't be afraid to do so, the 33 mm voice coil takes a lot of heat and my JungSon drove the speakers to 95 dB @ 2½ meter without noticeable distortion. Well done! They deliver a punchy bass that even can be felt. Do not expect anything in the 20-40 Hz range." You're right that I won't be looking to biamp my speakers for sometime, but it's a nice thought down the road.
 
Hey guys, I've had to set this project aside for some time, but here's a quick update on my crossover situation. After a several-months break I came back to PCD7, fiddled with figures, and came up with this design: electrically it's a damped 2nd order on the woofer and a damped 3rd order on the tweeter, and acoustically it's pretty close to LR4 slopes on both. Phase has been optimized for a 3+ meter listening distance. Electrical phase is very flat through the midrange and the impedance is also quite smooth. This is what I'm expecting to start with once I get the cabinets finished next week.
 

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The simulation looks very good, I also appreciate the use of "standard" values. However I think it is time for you to either try the crossover or to measure the speaker (or both). From what I've seen you don't have a real FR of the tweeter+waveguide, so it's time to have a reality check.
I can suggest you invest in some cheap film caps, ceramic resistors, and some coils. I bought a cheap LCR meter and use it to create custom value coils simply unwinding an oversized coil.

Ralf
 
You're absolutely right about that, but the only thing I'm really concerned about is whether or not the phase I've extrapolated is accurate or not. Otherwise I think these simulations should be pretty close to real life. I expect to have my own measurements made within a week or two, so the moment of truth is coming. :)
 
Long time no update, and I'll explain why. I gave up on the MLTL cabs I was building for these speakers as I realized that they were outside my ability to do, given that I don't really have a decent space of my own to get the work done and limited time as well, but it took me a long time to finally reach that conclusion. I only recently purchased a set of .75cf cabs from parts express to finally complete the project. I presently have them running with a quick test crossover just so I can finally hear music running through them, but it's far from optimized. Still they are sounding good and miles better than my old W5-1611 fullrange speakers; not much of a surprise there, but it was fun to A-B them and see just how much more capable these new speakers are. New components are arriving in a few days to make a proper crossover, the model of which can be seen below. It's simply an electrical 1st order plus LCR on the woofer and 2nd order plus pad for the tweeter. This provides the best frequency response/phase coherence/woofer breakup control that I could manage, and has a relatively low component count. Acoustically it's 1500hz LR4.
 

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I will bet that slope is no problem at all with that waveguide doing what it does... unless constrained by overall cabinet/baffle size, I think a waveguide loaded tweeter is absolutely the way to go in almost any two way design.

Nice project, speaker looks great.
 
Like Greggo said, I think the 1500hz target is a safe one given the waveguide. Given the same filter (3.9uF/0.8mH), the tweeter by itself would be rolling off much sooner. Still, I'll be checking distortion measurements to make certain of that once I have the new crossover in place.
 
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