3way XO help greatly appreciated!

Status
Not open for further replies.
Jump to Latest
#81
grantnsw said:

I must admit I've been vacillating between XO topologies, but I'm now seriously leaning to LR2 for each driver including bandpass at 300/3000. I thought that I had understood things from the 'Cookbook' but am still pondering Tinitus's enlightening reply. It raised even more questions re mixed order slopes etc. I might put an involved fundamentals type question here, but only if you have ~20mins to spare. So, at the moment a complete LR2 seems for me, ultimately easier , better documented and more likely to provide an 'acceptable' result. I'll just have to buy a good meter and unwind coils! The tweeter I think is rated at 100W (2ndO. XO) so 3000 should be OK (resonance 1500).
grant
Click to expand...

Hi,

You do not pick an electrical crossover topology, you can pick an acoustic topology.

e.g. this design has acoustic 2nd order L/R, and 0.5 way for BSC.

http://www.zaphaudio.com/Waveguidetmm.html

Note it is 1st order electrical.

Cookbook 2nd order electrical L/R for the bass/mid will not work.

🙂/sreten.
 
#82
Hi, a quick question please?
I just found the printed P25 specs(1988) and I'm trying to normalise' it with the CA15 driver response.

P25: 90dB @ 1W @1M. This IMPLIES to me 2.83V used as P=V*V/Z. (assume Z is purely resistive). Is my 2.83V assumption correct? But the FR graph is 2V input @ 0.5M - assume normalized to 1M. (hardly any noticible difference for 0.5M anyway?)

For the CA15: Sensitivity 87.5dB (2.83V@1M)
FR graph: "The frequency responses above show measured free field sound pressure in 0, 30, 60 degrees angle using a 20L closed box. (FR) Input 2.83 Vrms, microphone @ 0.5M, normalized to SPL @ 1 M. (The dotted line is a calculated response in infinite baffle based on the parameters given for this specific driver. The impedance is measured in free air without baffle using a 2V sine signal)".

A question please; assuming the P25 FR was done at half the power of the CA15 measurements, i.e. 3dB down. Would the P25's FR graph need to be increased overall by 3dB to be consistent with the
CA15 considering my assumption that the stated sensitivities are essentially the same? Not sure. Probably a dumb question!
thanks , grant
 
#83
Hi Sreten,
Re: "Picking an acoustic topology"......Oops, yes, a fundamental design requirement.
Thanks for reference to Zaph's waveguide, I'll have a look.

Re: (quote) "Cookbook 2nd order electrical L/R for the bass/mid will not work". I guess I'll have to do more study to identify the reasons why. I presume its dependent on driver roll-off rates, eg, the order of rolloff down towards resonance?

I think I understand that the resultant acoustic response is a combination of the electrical rolloff of xo and the drivers natural rolloff. Cookbook formulas don't consider the particular driver being used. thanks again Sreten, grant
 
#84
Hi,

2V at 0.5m meters gives the same result as 2.83V at 1m.

All Seas specs do try and show the 1m/2.83V sensitivity.

Note the CA15 response includes the baffle step of the 20L box.
Probably not fully realised at 0.5m distance.
The same is probably true of the P25 specifications.

🙂/sreten.
 
#86
Sreten, Your'e the Man! I only posted that about an hour ago! Awesome! Thanks!

So there is 3dB difference in only 0.5M! i.e. the power reduces by half in only half a metre! I didn't realize that.
So, it looks like there is no problem using my P25 specs as is, in conjunction with the CA15. More great news and very valuable advice. If you're ever in Sydney on holidays I must shout you a beer or 3! ...
(Still reading Troels TJL3W, Ekta and Zahra) grant
 
#87
Grant, thank you very much for the link. I took a quick glance at it and will have to review it again. I gotta rehook up my computer speaker. I tore it apart to try to use my computer for impedance measurements, with the frequency generator on WinISD. Long story.........LOL.I will have to go back to my old freq. generator for final plots.......I am thinking I can use my measurements, in the cabinet for part of my zma, frd files for the woofer, and maybe I am barking up the wrong tree......... Recently I have been trying to download and apply zma and frd files for the Seas CA15RLY and the Seas 27TDFC from the link Sreten provided, but am encountering problems............They are only downloading as text files, and I can't import them into the crossover application. Am I doing something wrong here? Also, Im not sure about the trace program which creates these type of files. More study needed......At any rate, I'm getting ready to apply final coats to my baffles so I can move on to the crossovers, meanwhile, taking in as much as possible here............Let's keep in touch.................Regards............Omni
 
#88
omni said:
......... Recently I have been trying to download and apply zma and frd files for the Seas CA15RLY and the Seas 27TDFC from the link Sreten provided, but am encountering problems............
Click to expand...

Hmmm...

The calypso.swd file needs to be opened in SW.

The zma and frd files have already been converted into SW files,
i.e. they are already imported.

🙂/sreten.
 
#89
Sreten, check out rjbaudio.com/files...........It's a database of frd and zma files for download on that website that the Calypso is on. I tried to download the Seas 27TDFC and CA15RLY zma and frd files to import into Jeff Bagbys crossover designer5.1 which is also downloadable from this site. These files were tagged as text files in my computor after I downloaded, and I could not import them into the crossover designer5.1. I would like to play with this designer in addition to the SW which I downloaded as well. If you have any insights after lookin at it let me know if you can. Maybe I am doing something wrong....................Respectfully............Omni
 
#91
Omni,
Many thanks for the link to RJB's Seas frd & zma files. I didn't know they were there! I still haven't progressed very far yet with SW. Now having these files give me an impetus to 'get cracking'.

Sreten,
thanks for your clarification of the above files. best regards, to you both, grant
 
#94
Grant I looked at the specs you mentioned and I am not certain what they are yet either, they do indeed look strange. Probably will have to backtrack the project to find out whats up with them. It has often been mentioned that Speaker Workshop has a steep learning curve............Guess what............they were right........lol........... Sreten, you mentioned the zma and frd files were text files with extensions. You also instructed me to change them back............How do I change them back? .............Desparately..........Omni
 
#95
Hi,

Set you file browser to show extension names, so all Word
documents are .doc, Text .txt etc. You can then change the
extension using Rename.

The TS values in the Calypso.swd file are fillers, they don't
matter, only the zma and frd values matter.

The impedance is measured in box, hence the reflex double hump.

🙂/sreten.
 
#96
Sreten, thank you for further clarifying that. Also, upon further reading at the site, the files need to be processed further in Unibox and a couple of the other downloads before importing them into a crossover design program. Sounds somewhat tedious to begin with, but once I learn it, I imagine that it should become second nature..............Hopefully,the weekend will provide more uninterupted time to get this rolling...........Grant, I am wondering if that 35 cubic feet is the volume of the box that the CA was measured in..............Regards...........Omni
 
#97
Hi Omni,
(politely)..From what 'I understood' Sreten said; is that the Thiele-Small driver data in the SW resource bar is irrelevant and overidden by the contents of the frd and zma files. The driver inclusion there is only to maybe 'allocate' the device, and that their properties are sourced elsewhere. Please correct me if I'm wrong!

I really don't know and haven't got to that stage yet - I'm still trying to grasp the user guide!. Also, still wanting to try your 'Bagby' reference , thanks! ...(other big commitments at the moment)

Not sure yet how much use I can make of SW without test-equipment, but already, thanks to Sreten, I can BEGIN to see how varying driver parameters (in Basta) alters response. 'Untested'
'ball-park' information is the best I can get at the moment for my woofers (~20yo spec sheet), but I'm sure the P25's are usable up to 300Hz(12dB/O) and may match well with the Seas mid/tweets.
I can't wait to 'Seas' the day!......hehe

Re: xo...I'm keen to (try to) implement a 'flatish' acoustic summed response where each drivers rolloff would hopefully suit an LR2 electrical. (Whew, hope I got that right, Lol) I think they do, maybe! So, because our drivers will be the same, (except woofers) it would be interesting to compare what we decide on, and why. If OK with you? Including things like bandpass gain, baffle step and diffraction
effects.

Hi Sreten, I'd just like to thank you again for 'hanging-in' here and still helping us out!, grant
 
#99
Hi Omni, me again, lol
I was thinking of LR2 for all my drivers, (roll-offs considered) untill I read something here....
It seems the TDFC is 'almost' bullet-proof'. I searched for 'TDFC' and got this post from 'Rabbitz':

(Hope Rabbitz doesn't mind me quoting him? 'Coz I need to buy some gear from him!)

20/7/2006 (quote): "I've run the 27TTFC at 3000Hz in a 1st order without any problems and the 27TDFC should be able to go lower as they are tough and have a lower Fs. If you're stupid with the volume control, then it's game over but I've never blown a tweeter using a 1st order".

Now, assuming say ~2700? (1st) for TDFC, if possible, and same for CA15 (surely no probs there!) it seems to me that (woofer-wise) I have enough overlap/bandwidth for a 'full' 1st order.
Your ALU 830669 Peerless (from memory) is good to 270Hz but maybe needs 2nd order for cone breakup @2K? In my case, less complexity of xo is a bonus. I'm seriously considering this if moderate power is ok. Maybe only <5W going to tweeter? What do you think Omni? ,grant
 
Status
Not open for further replies.
Top Bottom