1st Order Anarchy

[Johnloudb]

I'm considering the Peerless 831735 6.5" HDS woofer for my Thiel CS1 speakers. This is a rebuild thread. The driver is on sale and they will fit perfectly. My question is will I need a new crossover?



Okay, I know the answer that one ... and I will be taking measurements and designing my own crossover. So, is the Peerless up to the task of a first order crossover? I can't find any frequency response data on PE's site but I'll be Googling for it.

I need a tweeter as well. Any thoughts on a good tweeter for a first order design. Yes, it's going to be first order or I'm not doing it. Where are you David G?

Welcome any input, thanks!

[Johnloudb]

Thanks for the input everyone! I'm still playing with this woofer on x-over pro and your responses confirm a x-over point somewhere between 1900 & 2300 Hz! The one problem seems to be the woofer is allways reaching for the tweeter for an even plot on the amplitude graph! I've tried 4th, 3rd and 2nd order and 1st order seemed to produce good results! Any inputs or thoughts??? I'm going with the Vifa D27-45-06 on this design for just a 2-way setup.....

Still haven't found measurements but am looking. I'm encourage by the post above I found on Tech Talk in this thread:

http://72.9.35.76/showthread.php?t=218716

[Undefinition]

I have found very few tweeters that want to work well with just a 1st order crossover. In fact, the only one I've used personally is the Seas 27TDFC, which is very well-behaved with only a cap and an L-pad. Supposedly, the Morel MDT33 was also capable.

[Face]

I have experience with it, but this may work due to it's drooping top end and low fs: https://www.madisound.com/store/prod...oducts_id=8724

You will at least need a zobel too.

This one has a claimed fs of 420hz: https://www.madisound.com/store/prod...oducts_id=8714

[Johnloudb]

Thanks guys! Both the Seas and Scan tweeters look good. I'm kind leaning toward the Seas because Paul C has had experience with it, and it looks like it has a flatter impedance.

I don't see how the manufacturers expect anyone to get anything from the impedance plots on there data sheets though. I mean, there is no scale - am I missing something?

The woofer will play down to 40Hz in my box, which is a real nice.

Paul,

When you used that tweeter did you do anything to flatten the impedance more like use a zobel?

What are your subjective impressions of it?

My Thiels have a shallow waveguide built into the baffle, so I'll have to see how that affects the response once I take measurements.

John

[Johnloudb]

Paul, I see all my questions about the tweeter are answered on your website, in the Aethers build. Looks like you've used it at least a couple of times. Very nice website and documentation, btw. ;x(

[Undefinition]

Thanks. That design's got some whiskers on it, but what I said about the tweeter is still true.

The impedance is VERY benign, don't worry about impedance compensation. You will need an L-pad to attenuate its SPL. But from there, it's merely a matter of finding the right value cap to get you the crossover point you want.

The TDFC has a rising top end (read: "slightly airy"), but the TBFC does not. Both are very, very good tweeters. Can't go wrong, either way. Oh, and whichever one you choose, you can certainly EQ the top end of the tweeter using a contour filter: (inductor || resistor) or (capacitor || resistor)

[Johnloudb]

Okay, I got the woofers in the mail yesterday. They are pretty woofers!



My Thiel got roasted years ago from an amp going DC. I wasn't sure why the tweeter got roasted since the tweeter cap should block DC. Now I see that J. Thiel gave a little boost to the low frequency of the tweeter, with a resistor in series with an inductor that paralleled the cap and L pad resistor.

So the DC got this resistor and tweeter real hot and the resistor also toasted the cap next door. I drew up a schematic for the crossover just for fun, but forgot to take a photo. But, I'll post that later. Here's the crossover:



The Thiel CS1 box:



I think I'll go with the Seas fabric dome you mentioned Paul. I'm a bit of a phobe of metal domes. I just remember when metal domes were the thing and all the speakers with them, that I heard at audiophile shops sounded bright and edgy to my ears. I'm sure this fear is probably uncalled for now though. I'll just fix the high frequency rise on the Seas 27TDFC like you mentioned.

First I'll take measurements of the woofer the though. I'm not sure a ported box is such a good idea, cause it will have an f3 of 38Hz which is asking a lot for a 6.5" driver. So, going sealed with and f3 of 60Hz maybe better?

Well, I do some sims and post them soon.

[dsrviola]

Despite the very low FS on those Illuminators, I've heard that most of those ring radiators don't like to be crossed over low, and definitely not 1st order. Don't shoot the messenger...

[Face]

Not that I was planning on it, but thanks for the heads up.

[Undefinition]

So the DC got this resistor and tweeter real hot and the resistor also toasted the cap next door. I drew up a schematic for the crossover just for fun, but forgot to take a photo. But, I'll post that later. Here's the crossover:

Ouch! 8O That's pretty bad.

[Johnloudb]

Ouch! 8O That's pretty bad.

Yeah, we called the fire department when that happened. We smelled smoke but didn't know where it was coming from at first.

[Johnloudb]

Ported

Well, I did some box simulation and I don't think the box is big enough to get the ported response I want, so I'll probably go sealed.

Here is the SBB4 ported response using LSPCAD Lite:



Here's the excursion:



What worries me is that at an SPL of only 88dB and 1 Watt the woofer is already past it's Xmax of 6mm. I don't think that's good, so I think ported is out.

[Johnloudb]

Sealed

Here is the sealed response, Butterworth:



Here is the excursion:



That is in a box of 0.53 cu. ft. and since my box is about .84 cu. ft. I can experiment with a critical response or a Bessel response.

Anyway, that's where I'm at now. Got to put the woofer in and take some measurements. If all goes well then I need to make some mods to the box to flush mount the tweeter, and fix detachable grill/baffle to accommodate the woofer which is a bit bigger diameter.

[Undefinition]

What worries me is that at an SPL of only 88dB and 1 Watt the woofer is already past it's Xmax of 6mm. I don't think that's good, so I think ported is out.

Well, hang on there. How often will you be playing music with 20 Hz content. Or even stuff below 30 Hz? Excursion doesn't seem like such a problem when you see it that way, does it?

[Jed]

John,

Are you looking at hitting a 1st order acoustic slope? If so... the Seas tweeter won't do it if you are planning on crossing over at a frequency where woofer beaming won't become a major issue. Most of the Seas 27 Series roll off fairly quickly at around 2k (acoustically speaking without a filter). So my recommendation would be to find a tweeter that has a response flat to 1k. Maybe the Dayton RS28F. It's much more extended at the low end than a lot of tweeters out there. Plus they sound nice.

[Johnloudb]

Well, hang on there. How often will you be playing music with 20 Hz content. Or even stuff below 30 Hz? Excursion doesn't seem like such a problem when you see it that way, does it?

I'm not sure. It does rule out Dark Side and organ music. I wouldn't play it that loud but my dad might. What if he decides to crank up the military channel - you know bombs, tanks, and the like? This isn't our main system and he usually doesn't play the TV that loud, but I don't trust him.

If it were just me, I'd might go ported. Well, I'm not sure, I'll have to think about it. What happens if the driver gets pushed well beyond Xmax? Dead driver?

John,

Are you looking at hitting a 1st order acoustic slope? If so... the Seas tweeter won't do it if you are planning on crossing over at a frequency where woofer beaming won't become a major issue. Most of the Seas 27 Series roll off fairly quickly at around 2k (acoustically speaking without a filter). So my recommendation would be to find a tweeter that has a response flat to 1k. Maybe the Dayton RS28F. It's much more extended at the low end than a lot of tweeters out there. Plus they sound nice.

Yeah, I see you what you mean. Looks like Thiel used some low frequency compensation on his tweeter to extend the response lower. The RS28F does look nice, and that would be easier to implement. Did you use an RLC network to notch out the impedance peak?

I read on the PE board that the Peerless likes to be crossed over at around 2K. So that's what I'm planning on but got to take some measurements and see what I got first. Though other Peerless HDS drivers are pretty flat all the way to 3k, with only a slight bump at 4k. Even that disapears at 30 degrees off axis.

John

[Johnloudb]

Here is the schematic diagram for the Thiel crossover.



Anyway, I'm guessing that the resistor and inductor in series with the tweeter is there to boost the low end of the tweeter to extend the response. Just a guess.

But, I agree Jed. The Dayton looks like it would be a good fit for this project.

[Jed]

Did you use an RLC network to notch out the impedance peak?
John

For your application I would...

[SpeakerGuy]

...What worries me is that at an SPL of only 88dB and 1 Watt the woofer is already past it's Xmax of 6mm. I don't think that's good, so I think ported is out.

My experience with the similar 830875 woofer ported is that it has a good amount of bass potential, physical x-max seems pretty decent on these.

I had a pair playing in some ported cabinets, tried the "bass boost" button on the cheap old Sony amp I happened to be using at the time, thought: hey, that sounds good, and I turned it up to a nice moderately loud volume. I did not hear any unplesantness out of the woofer as a result.

If you like to go ported with a woofer like this (not very big, not too beastly on the x-max) I suggest some method of limiting input below tuning frequency, either a passive or active high pass. As long as you do that, I think you'll be pleased with what you can get out of them. It's always easier to stuff a sock in a port, than to go back and add a port later (not that you couldn't)...

[Johnloudb]

If you like to go ported with a woofer like this (not very big, not too beastly on the x-max) I suggest some method of limiting input below tuning frequency, either a passive or active high pass. As long as you do that, I think you'll be pleased with what you can get out of them. It's always easier to stuff a sock in a port, than to go back and add a port later

Okay, good point! Maybe I'll just stick a sock in the port it has now and see how I like them sealed. Then maybe add a port later, and add a filter before the amp. Adding the port is pretty easy, since it can fit right inside the old one.

[Undefinition]

My goof. I guess when you said "1st order," I just assumed you meant 1st order electric, since 1st order acoustic (-6 dB/oct) slopes are actually kind of hard to do. The advice I gave you regarding the Seas tweeter--only using a cap in series with the tweeter--will actually get you a -12 dB/oct slope.

Just my $.02, but I think 2nd order (-12 dB/oct) slopes would be much easier to work with than 1st order (-6 dB/oct). The only real drawback is that it couldn't play a pure square wave. :roll:

However, don't let me dissuade you from a good old fashioned experiment. If the 1st order acoustic slopes give you too much trouble, just remember that you can fall back on 2nd order acoustic slopes and the whole thing should come together pretty easily. And with all that said, the Dayton RS28F is capable of playing quite low for its price, so that seems like a logical candidate. The way to tell if you NEED an impedance compensation filter on a tweeter is if the response gets peaky or otherwise weird around the tweeter's Fs. You won't hurt the tweeter by not having one, however your ears might get tired of the extra noise after a short while.

[Johnloudb]

But Paul, I want to play square waves!

I'm just looking to keep it a first slope for the first octave. I think these drivers are up to it. If it doesn't sound good, I'll do something else, probably second order like you mention.

Well, I got to get to work and get the woofer mounted and take some measurements.

[Johnloudb]

Update: I'm waiting on a new Dayton T-amp as my old Sonic Impact T-amp broke awhile back. That's what I use to test speakers with.

I've been making use of Paul's nice documentation on speaker design. ;x( Was able to use SPL Copy to get frequency and impedance data in .FRD and .ZMA(?) file. I think I'll try modeling a few different tweeters and see what I can do with them before I decide which to buy. I downloaded Speaker Workshop and imported the plots and displayed them in a graph. Got to read more on Speaker Workshop and find out how to model a crossover.

I'm using ATRA to take measurements of the woofer and then I'll import them into Workshop. Does Speaker Workshop work good for modeling crossovers? I'm also considering LspCAD lite for $90 but wanted to try this first.

So, why am I doing a first order crossover? Well, all my very favorite speakers have been either full range or first order speakers. That includes Soundlabs speakers, Thiel speakers, as well as our Nelson-Reed 804B speakers which are first order between the mid and tweeter. Even my full range Infinity in dash car speakers have something very musically right about them.

Does that mean anything? No, except to me. These Thiels were not perfect speakers and they were somewhat deficient in high frequency detail in comparison to more expensive designs. But the naturalness of the Thiel's sound could make me melt at times. They just suck you in.

So, enough of my subjective blathering. I just think that speaker manufacturers like Vandersteen and Thiel go to the trouble of doing first order designs for a reason. I think there is some benefit to going this route.

[Undefinition]

I think I'll try modeling a few different tweeters and see what I can do with them before I decide which to buy. I downloaded Speaker Workshop and imported the plots and displayed them in a graph. Got to read more on Speaker Workshop and find out how to model a crossover.

I'm using ATRA to take measurements of the woofer and then I'll import them into Workshop. Does Speaker Workshop work good for modeling crossovers? I'm also considering LspCAD lite for $90 but wanted to try this first.

Yeah, some modeling using mfr graphs can go a long way before you purchase any parts. And really, I've heard several great speakers that were ONLY done using traced mfr graphs and modeling software. Conversely, I've heard several stinkers that were designed with real-world measurements. In my opinion, the real magic of crossover design is in the designer having a good ear, and being honest with himself if something doesn't sound right (even though it should theoretically be "correct").

I've used Speaker Workshop a few times, but I've found it difficult. Some people are great with it, though. You really can't beat Jeff Bagby's Passive Crossover Designer for being intuitive. Also the price is nice, too!

[Johnloudb]

Well, I don't have Exel so, I may just get LspCAD.

[BOBinGA]

I believe PCD also works with Open Office Calc. You can download that for free.

http://download.openoffice.org/

-Bob

[Johnloudb]

Thanks Bob! I use Open Office - I'll give that a try.

[kmibb]

Thanks Bob! I use Open Office - I'll give that a try.

Bob is incorrect, it will not work with OpenOffice.

[Johnloudb]

Bob is incorrect, it will not work with OpenOffice.

Okay, too bad. That's the impression I got from reading Jeff Bagby's website.

So, it's back to LspCAD lite I guess. That should work good for me I think.

Got my T-amp and played the woofer full range in the cabinet, with a sock in the port. It's a speaker, though not much high frequency and kind of dull and rough sounding.

Will try to get some measurements this weekend.

[SpeakerGuy]

So, it's back to LspCAD lite I guess. That should work good for me I think.

I found LspCAD to be a little easier to learn/use than SoundEasy. I used the free demo version to learn it. I do very much like the crossover simulator in LspCAD.

Got my T-amp and played the woofer full range in the cabinet, with a sock in the port. It's a speaker, though not much high frequency and kind of dull and rough sounding.

You'll have that, without a proper crossover + tweeter. Rough eh? I would say it's quite a smooth woofer (at least, the 830875 which seems quite close?) I'd be pleased to try to help with the crossover if you get some proper actual measurements

Have you seen this?:

[Johnloudb]

Well, I'll download the LspCAD demo, see what that looks like.

The overall sound of the woofer was pretty soft, just in the higher frequencies (what were there) it wasn't as smooth as what I'm used to. I noticed it sounded better slightly off axis, so I was probably hearing that slight peak in the high frequencies, assuming it has a similar response to the 830875. Yeah, I didn't expect much. :W

Sure, some help would be great. I'll see if I can manage to take some measurements, soon. I'm just getting acquainted ARTA "STEPS" and got to wire that up their test setup to my sound card. Think I can find the right wires around here somewhere.

No, I don't know what speaker that is. I think I recognize the woofer. Is it first order?

[Face]

Those are Sonus Faber Toy Towers. I've never heard those, only Strads.

[Johnloudb]

Those are Sonus Faber Toy Towers. I've never heard those, only Strads.

Looks like it's a pretty well liked speaker from peoples comments online.

Okay, well I got distracted from my speaker project and got busy finishing a little preamp circuit I wanted to try out and I measured the distortion.



That's at 2.8 volts out I kind of expected the high distortion, given it's a single JFET common source preamp. Also the voltage rails are too low at +/- 10volts from my regulated battery supply, but I just wanted to try it. The sounds sucks too. But, intend to use the supply with my active crossover, for my 3 way speaker project.

So, today I attempted to take some measurements of my woofer. It was all going fine and got everything set up and then I see that ARTA "STEPS" demands I use a $300.00 mike calibrator for a mike that is already calibrated!!!

Am I missing something. Why don't they just let me type in the mike sensitivity. Surely they didn't need to make this that painful. Anyone familiar with Arta?

My thought is just to use my SPL meter to calibrate.

John

[Mark K]

Just go to Setup->Audio devices and enter the mike sensitivity. I believe you're looking at Setup->Calibrate

[Johnloudb]

Just go to Setup->Audio devices and enter the mike sensitivity. I believe you're looking at Setup->Calibrate

Yes I was. Thanks Mark!

[fork]

Yeah, some modeling using mfr graphs can go a long way before you purchase any parts. And really, I've heard several great speakers that were ONLY done using traced mfr graphs and modeling software. Conversely, I've heard several stinkers that were designed with real-world measurements.

I wish more people had this opinion instead of just telling people to build an existing design.

[Johnloudb]

I got my first driver measurement, but not without some problems. My new mike didn't work ... it's a year old but this is the first time I tried to use it.

But, I have a small Radioshack clip on mike that I used instead. I think it has a pretty flat response at least according to Radioshack's graph anyway. I think I've discovered baffle step. And well I took some other measurements that were a just a tich off axis and they were significantly smoother (+/-2.0dB), so that could be good cause I never listen on right on axis when I set my speakers up. This is also what I noticed when I listened to music on them awhile back, that they sounded significantly smoother off axis.

I don't really trust my measurements too much yet because I'm new at this and had some problems, but I will take some more and with the speaker in a better position.