1 inch CD Comparison (SEOS18) - AVS Forum
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post #1 of 212 Old 06-18-2013, 07:31 PM - Thread Starter
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I recently received the SEOS-18 horns from the group buy. There are very few measurements of the SEOS-18. I wanted to find out how much lower can the SEOS-18 be realistically used compared to the SEOS-12 and 15. Although, the directivity may be controlled to below 800 Hz, are there drivers out there that can go that low? What sort of crossover can be used without driving the drivers into distortion?

So, I gathered the four most popular 1 inch drivers: DNA350, B&C DE250, BMS 4550, and the Radian 475PB.
EDIT:When I first started this thread, I thought I was using the DNA360, but it was actually the 350. This error was detected later in post 80. The graphs and text has been corrected to state that the measurements are for the 350, not 360.
Update 7/11/13: The DNA360 graphs can be found in post 168.
http://www.avsforum.com/t/1477921/1-inch-cd-comparison-seos18/150#post_23519679





Measurements are outdoors, at about 62 inches. I raised the waveguide above the floor using a table, and then put it on top of my woofer cabinet. I know the waveguide is not baffled, but the comparison is between compression drivers, so this should be fine. Here's the setup:





There is a thin strip of weatherstripping that the horn sits on. It helps isolate it somewhat from the vibrations of the woofer cab.





A good way to kill the floor reflection is to put some fiberglass on the ground. I stuff the fiberglass in microfiber pillow covers that you can buy at Walmart for $4 a piece. It has a zip, so it will contain the fiberglass, and plus the pillows are portable, so you can move them around any way you like. When you're done, just put them away. They really work very well in killing the reflection. I'm using an R-11 batt, but I know I can get more in there.



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post #2 of 212 Old 06-18-2013, 07:43 PM - Thread Starter
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I made the frequency response measurements in Holm and the distortion measurements in STEPS. It's difficult to compare the distortion in STEPS because it only allows two measurements to be compared at a time. So, I'm not showing the distortion in STEPS, only in Holm. But let's first see what difference, if any, the fiberglass-stuffed pillows made.

Here is the response of the DNA350 with and without the pillows. This is the raw (ungated, unsmoothed) response. There is still some ripple below 1 kHz, but most of it is gone after using the pillows.
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post #3 of 212 Old 06-18-2013, 07:53 PM - Thread Starter
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Now, lets go to the actual comparison. Up first, the DNA350, B&C DE250 and BMS 4550. This is the response with 1/24th octave smoothing.



Clearly, the DNA350 does not have the same output as the other two below 1 kHz. It also has a ragged top end. Nothing disastrous, but would require more EQ.

Let's look at distortion. The measurement is equalized for for an SPL of 90db at a distance of 2m -- a more realistic SPL and distance to gauge distortion at. I wanted to do it at 100 db, but proved to be too loud for the neighbors. With a compression driver, there shouldn't be any non-linear effects and so the 100 db distortion should be a replica of the one at 90 db, accept a little higher for all three drivers.



Again, the DNA350 has the highest distortion of the three.
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post #4 of 212 Old 06-18-2013, 07:55 PM
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Would have loved to see the BA-750 added to the mix. Out of all the 1" drivers, I think that driver has the best shot at playing lower.

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post #5 of 212 Old 06-18-2013, 08:01 PM - Thread Starter
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Let's bring in the fourth driver, the Radian 475. Here's the Radian 475, B&C DE250 and the BMS 4550. Again, 1/24th octave smoothing applied.



The Radian has less output near 1 kHz compared to the other two, but more output than the other two below about 600 Hz. Is this extra output useful? I doubt it. Plus, it's quite a bit more ragged than even the DNA350 above 7 kHz.

The Radian 475 does have lower distortion above 1 kHz than the other two drivers. But the lack of smoothness and bottom end means the Radian is out. That leaves us with two, B&C DE250 and BMS 4550, the usual suspects. Who would've thought Geddes and Danley knew what they were doing? biggrin.gif
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post #6 of 212 Old 06-18-2013, 08:08 PM - Thread Starter
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So, here's the comparison between the B&C DE250 (grey) and the BMS 4550 (red). The 4550 clearly has more output from about 900 Hz to 4 kHz, and it has lower distortion. Below 900 Hz, the 250 has maybe 1 db more output, and both drivers have similar distortion.



Here's the same response but now the B&C is offset by -5 db to show the two response more clearly. The BMS extends a few kHz higher. Regarding smoothness, which is very important, I'd say it's very even between the two.

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post #7 of 212 Old 06-18-2013, 08:16 PM - Thread Starter
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Coming back to the main reason I did this comparison: which driver has the most bandwidth down low and the smoothest response? Here's the comparison of the 250 and 4550 with a LR 4th order 800 Hz acoustical target. The target level is set to the lowest point in the HF.




The -24db point is one octave lower at 400 Hz. The distortion is sky high at that point. To make the response follow the target, a very shallow slope is needed and the CD will have little protection against the low frequencies. An 8th order target will probably work better with these drivers. So, even though the horn is capable of more, the drivers are not.

The question I'm left with is, which driver will work well on this horn? The BA-750 perhaps, as was mentioned earlier. Maybe the TAD-2001? The TAD is certainly out of my budget.

Thoughts? Comments? I need to send the drivers back, so if anyone wants to see some other graphs, let me know soon.
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post #8 of 212 Old 06-18-2013, 08:21 PM
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Very nice write up. Great stuff. Thanks.

I've always viewed the SEOS 18 as an odd duck. Could use a 1.4" CD but then you lose top end. So you may as well go with an even bigger horn. And the 1" can't get down far enough. I think the 4550 looks pretty good on there. And a hard 900hz XO would probably be fine and the waveguide will have lots of control. What are your thoughts.
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post #9 of 212 Old 06-18-2013, 08:23 PM
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Just saw your last post. What does the target look like for LR6 at 900hz.

Definitely go Linkwitz Riley to allow for a -6db knee.
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post #10 of 212 Old 06-18-2013, 08:31 PM - Thread Starter
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Tux, I may be wrong but I don't think the LR has a 36db slope. It goes directly from 24db/oct to 48db/oct. I don't know why.... well, I could find out if I dug deep enough.

I have to step out for a while. Will post the BW 36db 900 Hz target when I get back.
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post #11 of 212 Old 06-18-2013, 08:50 PM
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Quote:
Originally Posted by rahula7 View Post

Tux, I may be wrong but I don't think the LR has a 36db slope. It goes directly from 24db/oct to 48db/oct. I don't know why.... well, I could find out if I dug deep enough.

I have to step out for a while. Will post the BW 36db 900 Hz target when I get back.

LR36db slope is a choice on my MiniDSP 10x10HD.

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post #12 of 212 Old 06-18-2013, 09:10 PM
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Should be any even order. The LR has a softer knee than the BW, so I'd go that way if it were me. And 6th order is a nice compromise between a wicked hard 8th order and a to soft 4th order. I've used the LR6 on a few SEOS 12 things.
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post #13 of 212 Old 06-18-2013, 09:45 PM - Thread Starter
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ok..I was mistaken. For some reason, LR36 doesn't show up in the 2x4 MiniDSP.

Here's the B&C response with LR48 at 800 and LR36 at 900.




My main goal with the SEOS-18 was to get directivity as low as possible. While 800 Hz is better than 1000 Hz, it would be nice to be able to do an LR24 at 700 Hz. And none of these combinations will work at that point. I'm currently using the DNA360 with an 800 Hz LR48 target. It definitely sounds strained.
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post #14 of 212 Old 06-18-2013, 10:02 PM
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nice work!

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nice work!

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post #16 of 212 Old 06-18-2013, 11:08 PM
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I think you likely damaged your CD because the 360 response curve is way off everyone else's. Going by the charts, it looks like your extended use at too low of a crossover point messed up the diaphragm like it would with any of those models, not just the 360. You mentioned that you've been running the DNA-360 at 800hz for a while and said it definitely sounds strained. None of those brands are designed for use that low without having major problems.

If the crossover point gets pushed lower and lower to experiment......eventually you will fry them or distort the diaphragm.....just like your charts show. We can't experiment with lower points, hear stress and assume we didn't already cause issues. There is a point of no return, which is why all brands have their crossover recommendations. I'd never use any of those at 800hz or lower on a SEOS-18 because the diaphragms simply won't hold up, especially if they're used like that for an extended amount of time. You will certainly cause issues.


I test every 360 and none have looked like that. The distortion tests that Jeff Bagby posted and talked about on the PE forum were very low. Even Earl Geddes and other speaker designers did testing on them. They're good to go. But running any of those brands as low as you have on a big horn will cause diaphragm issues like your charts show.

There are replacement diaphragms, but none of those 1" CD's with similar diaphragm material will hold up long term at 800hz or less. They will eventually fail or have serious issues with flawed output and increased distortion because your set up is not recommended.

If you put a B&C DE250, BMS 4550, or 360 on an even deeper horn, it might look like they can go down to 700hz....but that's the horn helping. It doesn't mean you can actually use them that low without distorting or frying something. That's why they always recommend higher crossover points or you will eventually have the issues you posted.

I know it's fun to experiment and probably push things beyond their limits with that big woofer and waveguide. It's no different than someone thinking they can push a certain woofer farther and farther until they hear something bad. But you may have pushed too far past the recommendations. Keep in mind, ALL of those brands will fail. None are designed for what you're doing there. You need different CD's for an 18" horn and 700-800hz crossover points.
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post #17 of 212 Old 06-19-2013, 06:44 AM
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I was wondering why the DNA 360 measured different to the DE250. Is it possible it's been damaged a little?

You should be able to program LR36 with the mini 2x4. What plug in do you have? Also, you'll want to reach an acoustic slope, so likely won't use the LR36 setting anyways. More likely to use something shallower that will achieve the desired acoustic slope. That is the temptation of active XOers, but it doesn't work like that. You can't just hit LR36 at 900hz on the mini and expect good results.
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post #18 of 212 Old 06-19-2013, 07:46 AM - Thread Starter
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Quote:
Originally Posted by Erich H View Post

I think you likely damaged your CD because the 360 response curve is way off everyone else's. Going by the charts, it looks like your extended use at too low of a crossover point messed up the diaphragm like it would with any of those models, not just the 360. You mentioned that you've been running the DNA-360 at 800hz for a while and said it definitely sounds strained. None of those brands are designed for use that low without having major problems.

Erich, I don't think there is any damage to the diaphragm. I can post pictures of the diaphragm and insides. I have opened CDs before and know how to put them back. If you can link to some other measurements of the DNA360 on even a SEOS-12, it would be great. Even in my first measurement of the DNA360 just after I received it, it looked different to a DE250 on a SEOS-12 horn. I just never made a big deal out of it. I've been using it for over a year now. It works just fine on a SEOS-12.

I'm not trying to knock on your product. I don't want this thread to be about that. I want it to be about drivers that can be successfully used with the SEOS-18. I know that 800 Hz is pretty low for these all these drivers. A few db here and there doesn't really make a big difference.

Do you have any BA-750 in stock?

Quote:
Originally Posted by tuxedocivic View Post

I was wondering why the DNA 360 measured different to the DE250. Is it possible it's been damaged a little?

You should be able to program LR36 with the mini 2x4. What plug in do you have? Also, you'll want to reach an acoustic slope, so likely won't use the LR36 setting anyways. More likely to use something shallower that will achieve the desired acoustic slope. That is the temptation of active XOers, but it doesn't work like that. You can't just hit LR36 at 900hz on the mini and expect good results.

I have the latest 2x4 plugin. Not sure why it is not showing. Anyway, I can do it using biquad programming. 8th order works just fine, and provides more protection to the tweeter. I get good phase overlap between the woofer and tweeter and flat amplitude summing.

Yes, I do know about the difference between acoustical and electrical slopes. That what I was saying in post 7. With the 4th order target at 800 Hz, the electrical crossover will be very shallow and won't provide enough protection to the CD.
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post #19 of 212 Old 06-19-2013, 07:57 AM
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Maybe the TAD-2001? The TAD is certainly out of my budget.

send me a PM. I have one sitting around wink.gif

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I have the latest 2x4 plugin. Not sure why it is not showing. Anyway, I can do it using biquad programming. 8th order works just fine, and provides more protection to the tweeter. I get good phase overlap between the woofer and tweeter and flat amplitude summing.

You should use a large CAP to protect the CD drivers. Remember the DSP is connected to the AMP not the CD. 1st order rolloff around 500 to 700Hz is perfect for protection.

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post #21 of 212 Old 06-19-2013, 08:22 AM
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So which one is the best ?

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"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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post #22 of 212 Old 06-19-2013, 08:26 AM
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Penn is back. YAY!!!

Great thread also. I am on the look out for a 1" CD and possibly a 1.4/1.5" also.
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post #23 of 212 Old 06-19-2013, 08:27 AM - Thread Starter
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Quote:
Originally Posted by penngray View Post

You should use a large CAP to protect the CD drivers. Remember the DSP is connected to the AMP not the CD. 1st order rolloff around 500 to 700Hz is perfect for protection.

Sent pm re TAD.

I usually have a the signal rolled off sharply below 200 or 300 Hz in Holm. That works just fine. Cap introduces phase turn, which is ok if you are doing just measurements, but not good for crossover design. Anyway, the signal rolloff in Holm works just fine. Besides compression drivers are tough thingies. I have never managed to break any. FWIW, I have never broken conventional drivers or tweeters either.
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post #24 of 212 Old 06-19-2013, 08:29 AM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post

So which one is the best ?

I'd say it's a close call between the BMS 4550 and B&C DE250. I'm leaning towards the BMS because of higher output near 1 kHz and slightly smoother response. That said, the B&C is significantly cheaper than the BMS. And it will probably work just as well.
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post #25 of 212 Old 06-19-2013, 08:35 AM
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Quote:
Originally Posted by rahula7 View Post

8th order works just fine, and provides more protection to the tweeter.
SNIP
the electrical crossover will be very shallow and won't provide enough protection to the CD.

I'd disagree with this. 8th order has such a sharp knee compared to the 4th and 6th order that the steeper slopes will actually strain the CD more IMO. Below the -6db point, they all roll off quickly enough that excursion is reducing. See the transfer functions here:



You can see that they all converge at 800hz and -6db, as expected. Below that, they all roll off at or steeper than 24db/oct. Mean while the knee of the LR4 and 6 demand less output from the CD. Up to half the power demand. I'm talking electrical slopes of course. So if using an LR4 input, you may yield an LR6 acoustic.

With 4th through 8th order slopes, the harm happens at the knee, not below the knee. But all this is up for debate and I'd like to hear what other peole have to say about it. Possibly you disagree with me.

BTW, sorry I didn't know if you were thinking in terms of acoustic slopes or not based on something you said.
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post #26 of 212 Old 06-19-2013, 08:45 AM
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If I can elaborate in terms of distortion. Go back to the distortion measurement of the DE250 and BMS4550. See where the distortion swings up right below 900hz (why I mentioned 900hz). I would try and put the electrical -6db point of the transfer function right there. Below the -6db point you'll have 24db/oct or more of protection. With LR4 at 900hz you'll be -30db by 450hz. Even though the distortion is through the roof by 450hz, the xfer function is through the floor by then too. If using LR6 you'd be -42db by 450hz. That's plenty of protection.

I agree it's hard to wreck these things. Even with 2.83V I run sweeps with no protection. 20hz start frequency sweeps are no problem. I usually use less power on a CD though cause they're so loud tongue.gif

EDIT - 1 last thing. Once you level match the tweeter with your woofer you should get some free protection out of that. Like if you need to bring it down 10db, well, that's a lot of power.
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post #27 of 212 Old 06-19-2013, 08:56 AM
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Quote:
Originally Posted by rahula7 View Post

Erich, I don't think there is any damage to the diaphragm. I can post pictures of the diaphragm and insides. I have opened CDs before and know how to put them back. If you can link to some other measurements of the DNA360 on even a SEOS-12, it would be great. Even in my first measurement of the DNA360 just after I received it, it looked different to a DE250 on a SEOS-12 horn. I just never made a big deal out of it. I've been using it for over a year now. It works just fine on a SEOS-12.

I'm not trying to knock on your product. I don't want this thread to be about that. I want it to be about drivers that can be successfully used with the SEOS-18. I know that 800 Hz is pretty low for these all these drivers. A few db here and there doesn't really make a big difference.

A few db here and there does make a difference when they're run at 800hz or lower. It's like any other component you experiment with. If you push a woofer to see what it can do and it bottoms out for hours and you hear the straining, there will be damage. At that point it's not really fair to test it against other brand new woofers and wonder why it doesn't test good anymore. wink.gif It's been bottomed out to the point of failure.

Your 360 has definitely been damaged, the charts show it. When I did testing on the prototypes, I purposely ran some with smaller and smaller caps until failure. Testing them showed what you just posted. Experimenting and straining a 1" compression driver playing that low will distort the diaphragm on any of those models, not just the 360. You probably wouldn't be able to see it by just looking, but running it for long enough like that will distort them until they eventually fry.

Hopefully you don't really think the 360's test like. wink.gif Hundreds have been ordered and there's measurements of them everywhere. They're at least as good as the DE250 and have very low distortion. Keep in mind, any of those models you have will fail if you run them for any extended time at those lower frequencies. Rack it up as a learning experience, but you should let people know that in your tests because right now you're showing tests from an over-driven driver.

Just curious, why did you think those DE250's, 4550's, or 360's could work that low? Their manufactures all recommend a crossover no lower than 1000hz with a steep crossover. Just because a big horn boosts that low end, doesn't mean the driver will be safe running lower. It was discussed many times that 950hz could possibly be done, but not paired with the volume your big woofer would be putting out.

You need something like this:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=294-410


Because you were just experimenting, you can send me the driver and I will replace the diaphragms for you. Just don't go crazy like that again. biggrin.gif
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post #28 of 212 Old 06-19-2013, 09:44 AM
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BMS is rated from 500hz up and recommends an 800Hz crossover, fwiw....

http://bmsspeakers.com/index.php?id=4550_specification

Shane
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post #29 of 212 Old 06-19-2013, 09:52 AM
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Quote:
Originally Posted by tuxedocivic View Post

I'd disagree with this. 8th order has such a sharp knee compared to the 4th and 6th order that the steeper slopes will actually strain the CD more IMO. Below the -6db point, they all roll off quickly enough that excursion is reducing. See the transfer functions here:



You can see that they all converge at 800hz and -6db, as expected. Below that, they all roll off at or steeper than 24db/oct. Mean while the knee of the LR4 and 6 demand less output from the CD. Up to half the power demand. I'm talking electrical slopes of course. So if using an LR4 input, you may yield an LR6 acoustic.

With 4th through 8th order slopes, the harm happens at the knee, not below the knee. But all this is up for debate and I'd like to hear what other peole have to say about it. Possibly you disagree with me.

BTW, sorry I didn't know if you were thinking in terms of acoustic slopes or not based on something you said.

If its not a brick wall (Still don't have a DEQX), I do not bother even going past 3rd order any more even with the DSPs I use. I think the OP is still very confused on the issue of protection.

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post #30 of 212 Old 06-19-2013, 09:56 AM
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Originally Posted by rahula7 View Post

Sent pm re TAD.

I usually have a the signal rolled off sharply below 200 or 300 Hz in Holm. That works just fine. Cap introduces phase turn, which is ok if you are doing just measurements, but not good for crossover design. Anyway, the signal rolloff in Holm works just fine. Besides compression drivers are tough thingies. I have never managed to break any. FWIW, I have never broken conventional drivers or tweeters either.

I think you might be a little confused on why a Cap is need for protection. Your DSP equipment (I own many) does not protect your CDs (no matter what slopes you use) and while I also have not screwed up a CD, a simply CAP adds the only projection in a DSP setup. The phase shift at more then 1 octave below the XO point is meaningless.


Will you blow your CD without a cap in place? who knows, just turning on an amp can destroy a CD because there is ZERO protection between the CD and the amp. lower costs CDs are easily replaced.

I do not want to spend another $5 to $10K on CDs myself wink.gif

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