Corundum opinions

dynamo

I know, I ask about tweeters a lot..

Anywho, it sounds like people got some exposure to the peerless corundum tweeters at indiyana, as well as the Dayton Rst28A tweeters.

Could I get some subjective opinions on these?

Once I wrap up my RSX project I will be doing an 8” two way with some M8Ns I have laying around. I want to use a beefy tweeter and go sans waveguide for these and have narrowed it to these two.

The 32mm corundum with it’s published long throw, low fs, and large size seems the obvious choice, but the RST-a also has a reasonable fs, a nice “bbc dip” built in, is cheap, and with a high sensitivity I’d think it will of course make more output with less input and therefore perhaps lower distortion?

Any guidance between the two would be greatly appreciated!

Thanks!

jhollander

Both tweeters are detailed.  The Peerless don't seem as harsh(?) as the RST28As.  But that's me listening to my DA25TX. The DA32TX at Indy had a lot of energy so I might have voiced it differently.

Someone might have a graph, but I believe the Peerless will have the lower distortion.  I used the DA25TX down to 1,500 with LR2s.

I still want some extended listening time with the new RST28As.  That might change my opinion, but right now I like the Peerless.

Now Peerless DA25TX to old RS28A would be a toss up imo.  The Peerless has the detail and depth, but the old RS28A seems to do the bell sounds better.

dynamo

That’s great info, thanks. When you say the 32 had a lot of energy, do you mean that in a bad way or good? I’m assuming if one could pull down the 2-3k area a bit that might resolve the excess energy, right?

Im not opposed to the smaller corundum, but my thought was the larger size would help as I was planning a crossover point around 1100 with no waveguide.

jhollander

Yeah at 1,100 Hz. I'd do the DA32TX.

With the DA32TX at Indy without seeing the graph, you couldn't say the tweeter was hot, excess energy, or the woofer had the annoying breakup not pushed down. It's hard to know for sure.  Plus it's 3 minutes of music.

The 32 had the same detail I heard in the 1-inch so I was focused on that detail above everything else.  I voted the Peerless over the RST28A as I recall.  Later when talking with Ben, he mentioned the 32 Peerless was hot and then it clicked that indeed there was more energy in the highs.  I had confirmation bias I guess.  

Wolf

Yes- Curt's were very forward, but that does not discount how all 3-4 DATX tweeters sounded.

I'm pairing my DA32TX with the TB W8-2096S when I get there...

dynamo

jhollander said:

Yeah at 1,100 Hz. I'd do the DA32TX.

With the DA32TX at Indy without seeing the graph, you couldn't say the tweeter was hot, excess energy, or the woofer had the annoying breakup not pushed down. It's hard to know for sure.  Plus it's 3 minutes of music.

The 32 had the same detail I heard in the 1-inch so I was focused on that detail above everything else.  I voted the Peerless over the RST28A as I recall.  Later when talking with Ben, he mentioned the 32 Peerless was hot and then it clicked that indeed there was more energy in the highs.  I had confirmation bias I guess.  

Cool thanks again for the feedback. Sounds like the RS isn’t the worst at least but the Peerless is better if I want to spend it, but might need a little careful voicing. Thanks

dynamo

Wolf said:

Yes- Curt's were very forward, but that does not discount how all 3-4 DATX tweeters sounded.

I'm pairing my DA32TX with the TB W8-2096S when I get there...

I saw elsewhere you were doing that combo. I’m interested to see that, should be pretty nice.

4thtry

I agree with everything that John said about the DA25TX and would add that this tweeter has an ability to resolve detail that is comparable to several, much more expensive tweeters that also played the same house track.  That's one of the nice things about attending events such as this; you get to compare the sound of your speakers with ones using drivers costing several times as much. 

I was sitting up front with Ed P & ??, and I can remember being told to listen to how the DA25TX tweeter could resolve the female vocalist's exhalation on track 3. With most other tweeters, this "exhalation" simply disappeared. 

Regarding power, I have my DA25TX crossed at 1kHz at 12dB to the HiVi F6.  My first attempt had it crossed at 1.3kHz, but I did not like the sound.  Too much mid-rangy "bloomy-ness".  So I dropped it to 1kHz, which, per my measurements, helped significantly to dampen the first breakup mode of the F6 (-4dB or so).  I probably need to install a notch filter to handle this, but this would have boosted my parts count to 8.  Had to stay at 5 parts, so I decided to give the DA25 a little more juice!!  Seems very robust, with the big heat sink and all.  No apparent strained or beaming type sound quality that I could hear.   Did anyone at the event hear a tweeter related overload type problem with my speakers (the SideTowers)?   

Attached is a graph of HD at 95dB using the 1.3kHz xover.  I will re-do this using the 1kHz and post it next week.

Time will tell.  I may burn the tweeter at some point!   But I have decided to keep the 5 part xover just the way it is.  I like the way it sounds.

 

dynamo

Wow, that’s impressive that the 1” is happy with 1k second order. Maybe that’s the way to go since there is so much more feedback (positive at that) on the 25 than the 32. I wish I knew if the energy and hotness of the 32 in Curt’s speaker was the tweeter’s nature or his voicing. Was his in a waveguide?

PWRRYD

FWIW I am almost done building the boxes for a project that pairs the DA32TX tweeters with Peerless 830-869 Nomex 8" woofers.  I have no idea at what frequency they will cross or what slope yet.  I'll push the DA32's as low as they are comfortable to reduce the off axis issues of the 8" woofers.  These boxes are pretty big stand mounts....   a bit over one cubic foot net.  F3, if that is your fancy Grumpy, is only about 44 Hz but they don't roll off a cliff and can play quite nicely at 100+ dB.

dynamo

Sweet. I look forward to hearing your thoughts on the 32 in your build

dynamo

I also plan to do a one cubic foot stand mount. I want to do an interchangeable base plate that is a sealed stand mount, or custom stands that bolt in place of the plate that add a port and a half cube or so. This should get the m8n flat ported with an f3 around 29. Otherwise it models nice sealed if used without the bases. 

Ed_Perkins

Bill -

That was Joel from Meniscus that we were sitting with.  It was great sitting with him and have him explain what to listen for among the different speakers.  I believe he also was explaining how to detect bass distortion with you, but I missed most of that conversation.

rjj45

4thtry said:

I agree with everything that John said about the DA25TX and would add that this tweeter has an ability to resolve detail that is comparable to several, much more expensive tweeters that also played the same house track.  That's one of the nice things about attending events such as this; you get to compare the sound of your speakers with ones using drivers costing several times as much. 

I was sitting up front with Ed P & ??, and I can remember being told to listen to how the DA25TX tweeter could resolve the female vocalist's exhalation on track 3. With most other tweeters, this "exhalation" simply disappeared. 

Regarding power, I have my DA25TX crossed at 1kHz at 12dB to the HiVi F6.  My first attempt had it crossed at 1.3kHz, but I did not like the sound.  Too much mid-rangy "bloomy-ness".  So I dropped it to 1kHz, which, per my measurements, helped significantly to dampen the first breakup mode of the F6 (-4dB or so).  I probably need to install a notch filter to handle this, but this would have boosted my parts count to 8.  Had to stay at 5 parts, so I decided to give the DA25 a little more juice!!  Seems very robust, with the big heat sink and all.  No apparent strained or beaming type sound quality that I could hear.   Did anyone at the event hear a tweeter related overload type problem with my speakers (the SideTowers)?   

Attached is a graph of HD at 95dB using the 1.3kHz xover.  I will re-do this using the 1kHz and post it next week.

Time will tell.  I may burn the tweeter at some point!   But I have decided to keep the 5 part xover just the way it is.  I like the way it sounds.

 

Thanks for the feedback on the DA corundum tweeters.
But how did you get the multiple popup % boxes on the OM window? I've never seen that - didn't know that was possible. VERY useful.

Gowa

Crossed at 1kHz at 12dB!!

4thtry

  rjj45 said:

Thanks for the feedback on the DA corundum tweeters.
But how did you get the multiple popup % boxes on the OM window? I've never seen that - didn't know that was possible. VERY useful.

I was wondering if anyone would notice this new and improved OM feature.    Actually, this is "photoshopped".  It would really be nice if OM could do this feat, but no such luck.  To create the graph, I saved 9 screen shots, moving the curser to a different point on the graph for each shot, and then merged all the individual shots into one using the difference overlay blending technique in photoshop.  Looks really cool when you get done, but takes forever to accomplish.   

4thtry

dynamo said:

Wow, that’s impressive that the 1” is happy with 1k second order. Maybe that’s the way to go since there is so much more feedback (positive at that) on the 25 than the 32. I wish I knew if the energy and hotness of the 32 in Curt’s speaker was the tweeter’s nature or his voicing. Was his in a waveguide?

The 32 was not in a waveguide.  Here is a pic.  I had the same question running through my mind as I listened to these at the event.  This was my first and only listen to this tweeter, so very hard to speculate as to what the issue was.

PWRRYD

That is a beautiful looking speaker.  Maybe the energy and hotness was some untamed RS225 metal cone breakup.

Wolf

I'm sure that was part of it, as well as the DA32 not being padded enough.

PWRRYD

I'm about 1 week away from spending some time listening to and tweeking crossovers with this DA32TX.  I just finished machining hardwood baffles.  Hopefully I like these tweeters and the Peerless woofers.  But no biggy if I don't, I've burned better baffle wood than this  

rjj45

4thtry said:

  rjj45 said:

Thanks for the feedback on the DA corundum tweeters.
But how did you get the multiple popup % boxes on the OM window? I've never seen that - didn't know that was possible. VERY useful.

I was wondering if anyone would notice this new and improved OM feature.    Actually, this is "photoshopped".  It would really be nice if OM could do this feat, but no such luck.  To create the graph, I saved 9 screen shots, moving the curser to a different point on the graph for each shot, and then merged all the individual shots into one using the difference overlay blending technique in photoshop.  Looks really cool when you get done, but takes forever to accomplish.   

Thanks for the explanation! It doesn't look like Bill Waslo will add this to OM. sometimes I go through the (arduous) process of setting up ARTA just so I can get distortion graphs in % terms. OscarJr has an excel sheet that will convert and graph OM distortion files. Gotta see if he will share that....

dcibel

rjj45 said:

4thtry said:

  rjj45 said:

Thanks for the feedback on the DA corundum tweeters.
But how did you get the multiple popup % boxes on the OM window? I've never seen that - didn't know that was possible. VERY useful.

I was wondering if anyone would notice this new and improved OM feature.    Actually, this is "photoshopped".  It would really be nice if OM could do this feat, but no such luck.  To create the graph, I saved 9 screen shots, moving the curser to a different point on the graph for each shot, and then merged all the individual shots into one using the difference overlay blending technique in photoshop.  Looks really cool when you get done, but takes forever to accomplish.   

Thanks for the explanation! It doesn't look like Bill Waslo will add this to OM. sometimes I go through the (arduous) process of setting up ARTA just so I can get distortion graphs in % terms. OscarJr has an excel sheet that will convert and graph OM distortion files. Gotta see if he will share that....

This would be super simple, except that OM fails to export a correctly formatted CSV file. It misses the first comma after frequency, so when you load the data into Excel its a bit messed up. I don't have the time right now to go into much detail on this, but you can extract the data you need (dBSPL column) using a RIGHT function, and correct the frequency column using a LEFT function.

With correctly formatted data, the math to convert relative dB to % is simple. First, normalize the distortion data by creating a column with the following:

=C2-B2

=C3-B3

=C4-B4

etc

Where column C is the distortion, you can select which ever THD or harmonic column you like and column B is the fundamental dBSPL. The resulting values should be negative. This is the level of the distortion relative to the fundamental.

Take this relative dB, and convert to SPL by using the following function:

=POWER(10,M2/20)*100

=POWER(10,M3/20)*100

etc

Where M is the column of your previous calculation. You can test this is correct by entering -60 as the dB value, the formula should calculate 0.1%. Now simply create a plot of freq vs %.

rjj45

Thanks @dcibel - I'll give that a try tomorrow.
 

dcibel

Well now that I've burnt my fingers good on my lawnmower exhaust, my plans for the rest of today has changed while I sit around with my hand on an ice pack. Stupid moment while I adjusted the blade height...

I had a look at excel, and here's an easy way to fix the CSV data from Omnimic. First, select the data from columns B through H and move it over one column. Leavee the header in place, so copy everything from row 2 down. You should now have an empty column B apart from the title dBSPL in row 1.

Select all of column A, then go to Data -> Text to Columns. Tell the wizard you have space delimited data. That will split the SPL properly into column B, and Column A will now correctly contain the Frequency data. You can now add in the math columns as I explained above and plot the results.

6thplanet

^^^^ZOOM..right over my head 😕^^^^

dcibel

LOL, some simple excel tasks don't translate well when you try to explain them in words. The above post is really necessary to fix the fact that OM has a bug in the CSV export. If you guys are having trouble with this, I could make a video perhaps, but you'd have to wait until next weekend at the earliest, as I'll be in California all week this week training for work.

rjj45

dcibel said:

LOL, some simple excel tasks don't translate well when you try to explain them in words. The above post is really necessary to fix the fact that OM has a bug in the CSV export. If you guys are having trouble with this, I could make a video perhaps, but you'd have to wait until next weekend at the earliest, as I'll be in California all week this week training for work.

I do have some semi-expert Excel skills, so I read this easily. Feedback in a few hours later this morning.

4thtry

Thanks for the info on exporting OM distortion data to an excel file.  I did not know that you could do this; will have to give this a try next time around.

As I promised above, below is the HD at 95dB for the 1kHz xover.  Distortion is pretty much the same.  This was measured at a distance of 1 meter on axis with the tweeter.  Also attached is the SideTower 3 pane model, showing xover and detailed phase & rolloff slope information.  The highpass section conforms to a LR 4th acoustical slope with a corner frequency of 1.05kHz.  Using the same corner frequency of 1.05kHz, the low pass section conforms to a LR 4th order acoustical slope up to about 2kHz, then transitions to a 3rd order Butterworth beyond 2kHz.  I used dlr's Winfilters program to generate target files to overlay my xSim model.  The bad looking 4.6kHz glitch on the model was corrected by grinding off the baffle facets and replacing them with a smoothed out layer of mortite caulking cord and foam rubber.

I could very well be missing something here, but the speaker seems to sound OK to my old ears.  Time will tell.  I know it is very easy to miss a problem if you do not know, specifically, what to listen for. 

jhollander

Bill, I don't mean to be unduly critical but I thought that in the InDIYana finals both your and Dan's speakers distorted with either the first or second track.  I called it unloading, as it could have been the woofer.  My speaker could have distorted as well, it just was not in the finals...