Sreten Thanks!
The new re-baffled P25 vented box would be approximately 44 litres. The existing baffle would have 2 large square-ish holes cutout of it, but with a 1-2" horizontal strip remaing to keep the bracing intact. A new 1" baffle would go on top of whats left remaing of the old one. Also, the old mid and tweeter are now gone, as is the
current 1.5 litre mid box. So I'm guessing it will be about 44 litres, with stuffing (but not on the baffle's back-side). The top baffle would be identical to James' one (except for colour, lol). The MCA15 in the new top baffle has no enclosure.
If this P25 box would work, and I think your latest WinISD plots confirm this - your 'purple-line' at 40 litres and 30Hz tuning looks acceptable, but not as good as your optimal 70 litre 'red-line'. I'd probably move the port to the back, maybe 3-4 inch ID.
If the above is OK, do you think (please) the 'PFM Special' design is worth pursuing/modifying for my P25 and proposed 27TFFC's? (the mids and tweets still are still in the shop, but hopefully not for much longer!)
If so, thats splendid news! It would save me heaps of buck$. I'm wondering, in your opinion, how the xo's published by James would 'integrate' with my chosen drivers? You expressed no concern, so I assume...all's well? Btw, I think I understand Troels PMS version 5 xo, but James' xo seems a little odd...the mid LP/HP is reversed? and the mid 8.5mH coil seems kinda huge? Many thanks for your time and valuable comments, grant ( I hope I've answered your questions?)
The new re-baffled P25 vented box would be approximately 44 litres. The existing baffle would have 2 large square-ish holes cutout of it, but with a 1-2" horizontal strip remaing to keep the bracing intact. A new 1" baffle would go on top of whats left remaing of the old one. Also, the old mid and tweeter are now gone, as is the
current 1.5 litre mid box. So I'm guessing it will be about 44 litres, with stuffing (but not on the baffle's back-side). The top baffle would be identical to James' one (except for colour, lol). The MCA15 in the new top baffle has no enclosure.
If this P25 box would work, and I think your latest WinISD plots confirm this - your 'purple-line' at 40 litres and 30Hz tuning looks acceptable, but not as good as your optimal 70 litre 'red-line'. I'd probably move the port to the back, maybe 3-4 inch ID.
If the above is OK, do you think (please) the 'PFM Special' design is worth pursuing/modifying for my P25 and proposed 27TFFC's? (the mids and tweets still are still in the shop, but hopefully not for much longer!)
If so, thats splendid news! It would save me heaps of buck$. I'm wondering, in your opinion, how the xo's published by James would 'integrate' with my chosen drivers? You expressed no concern, so I assume...all's well? Btw, I think I understand Troels PMS version 5 xo, but James' xo seems a little odd...the mid LP/HP is reversed? and the mid 8.5mH coil seems kinda huge? Many thanks for your time and valuable comments, grant ( I hope I've answered your questions?)
Hi,
look at post 97 in that thread. Note the grey acoustic attenuation targets.
Using your simulation tools you can keep the MCA15 c/o but you
need to adjust the treble and bass sections (as you've been told).
Note the baffle step on the raw bass response and the acoustic
roll off of the bass unit starting at near 100Hz - hence the 6.5mH.
Note also the bass unit has no peaking and rolls off, hence the
1st order + zobel for the target 2nd order L/R point at 500Hz.
The same is true for treble, except the compensation is for
the impedance peak. FWIW the tweeters are not equivalent.
The Seas 27TTF is far more similar to the vifa than the 27TTFC.
🙂/sreten.
edit : The 8.5mH inductor is correct, reduces low bass to the mid.
look at post 97 in that thread. Note the grey acoustic attenuation targets.
Using your simulation tools you can keep the MCA15 c/o but you
need to adjust the treble and bass sections (as you've been told).
Note the baffle step on the raw bass response and the acoustic
roll off of the bass unit starting at near 100Hz - hence the 6.5mH.
Note also the bass unit has no peaking and rolls off, hence the
1st order + zobel for the target 2nd order L/R point at 500Hz.
The same is true for treble, except the compensation is for
the impedance peak. FWIW the tweeters are not equivalent.
The Seas 27TTF is far more similar to the vifa than the 27TTFC.
🙂/sreten.
edit : The 8.5mH inductor is correct, reduces low bass to the mid.
Hi again,
Think I may have been getting my tweeters mixed up.
However I'd simply re-use the D25's with some tweaking to the compensation.
🙂/sreten.
Think I may have been getting my tweeters mixed up.
However I'd simply re-use the D25's with some tweaking to the compensation.
🙂/sreten.
grantnsw said:
Hi, having looked at it more IMO 44L is best used sealed, inductor DCR 0.5 to 1 R, 🙂/sreten.
Sreten, Wow, thanks!
Your replies raise lots of questions......(in order of your posts)
Re: "the grey attenuation targets"...this might be a really dumb question, but I'm assuming James would have measured all the raw responses under identical conditions , ie, power/mike distance, say 1W at 1M. This is just a supposition, but fairly standard I think., which makes me wonder what the 0 dB y-axis is in 'absolute' terms? (probably showing my ignorance again!) Each driver's '0dB point' as shown, looks different?
Thanks for your other comments regarding the bass and treble...noted. Yes, Seas makes a 27TFF (H0831) its Fs claimed is 1200Hz, where Vifa claims 650Hz for the D27TG-35-06. I haven't checked the responses yet.
Now this is where it gets really interesting.... My ancient tweeters are Vifa D25TG-55-06's, but no specs available on the net. By this .."However I'd simply re-use the D25's with some tweaking to the compensation.", are you saying I could just use my old ones? (with tweaking). Wow, that would be a big *+* for me in trying to
modify James design. If this is possible to do, with no spec sheet, then things are looking up! I guess the series resonance trap is still required, but the values would need to change. I think this is what you're suggesting. I guess my D25TG-55-06's Fs is somewhere around 1200Hz(+?). The response could be pretty ordinary too?
Sreten, I believe your advice, and I note with great interest that you now consider the P25 would be best suited to a 44 litre approx. closed box. There are no doubt factors here that I don't fully comprehend, so I'm interested that James says his M26WR with Qts = 0.32 is 'borderline' for a closed box, so he used a series resistor
presumably to increase its Qts. Is this correct please?
On a quick glance, your closed box suggestion seems at odds
with the Vifa spec-sheet and James comments,..he says "The P25WO will need to be reflex loaded if you want to get any bass from it." and "The Qts of the P25 is too low for sealed box loading and would need to be ported." This is very interesting, Vifa claims the P25 Qts is 0.28.
Of course I have no objection to sealing up the bass box, if it sounds good. I'm just trying to reconcile James differing opinion. I guess the inductor DCR from 0.5 to 1 R would appropriately raise its Qts suitability for a sealed box? I'm trying to read between the lines of your reply here....
Are you now considering closed in view of our recent discussion of room gain and no 'knee' response? But a closed box doesn't offer as much bass extension as a vented box. Could you please enlighten me as to why you now think closed is preferable? I'd really appreciate your thoughts on this.
There is something appealing about James PFM design, if I could possibly modify it now using my existing tweeters and woofers. Thank you Sreten! ...grant
Your replies raise lots of questions......(in order of your posts)
Re: "the grey attenuation targets"...this might be a really dumb question, but I'm assuming James would have measured all the raw responses under identical conditions , ie, power/mike distance, say 1W at 1M. This is just a supposition, but fairly standard I think., which makes me wonder what the 0 dB y-axis is in 'absolute' terms? (probably showing my ignorance again!) Each driver's '0dB point' as shown, looks different?
Thanks for your other comments regarding the bass and treble...noted. Yes, Seas makes a 27TFF (H0831) its Fs claimed is 1200Hz, where Vifa claims 650Hz for the D27TG-35-06. I haven't checked the responses yet.
Now this is where it gets really interesting.... My ancient tweeters are Vifa D25TG-55-06's, but no specs available on the net. By this .."However I'd simply re-use the D25's with some tweaking to the compensation.", are you saying I could just use my old ones? (with tweaking). Wow, that would be a big *+* for me in trying to
modify James design. If this is possible to do, with no spec sheet, then things are looking up! I guess the series resonance trap is still required, but the values would need to change. I think this is what you're suggesting. I guess my D25TG-55-06's Fs is somewhere around 1200Hz(+?). The response could be pretty ordinary too?
Sreten, I believe your advice, and I note with great interest that you now consider the P25 would be best suited to a 44 litre approx. closed box. There are no doubt factors here that I don't fully comprehend, so I'm interested that James says his M26WR with Qts = 0.32 is 'borderline' for a closed box, so he used a series resistor
presumably to increase its Qts. Is this correct please?
On a quick glance, your closed box suggestion seems at odds
with the Vifa spec-sheet and James comments,..he says "The P25WO will need to be reflex loaded if you want to get any bass from it." and "The Qts of the P25 is too low for sealed box loading and would need to be ported." This is very interesting, Vifa claims the P25 Qts is 0.28.
Of course I have no objection to sealing up the bass box, if it sounds good. I'm just trying to reconcile James differing opinion. I guess the inductor DCR from 0.5 to 1 R would appropriately raise its Qts suitability for a sealed box? I'm trying to read between the lines of your reply here....
Are you now considering closed in view of our recent discussion of room gain and no 'knee' response? But a closed box doesn't offer as much bass extension as a vented box. Could you please enlighten me as to why you now think closed is preferable? I'd really appreciate your thoughts on this.
There is something appealing about James PFM design, if I could possibly modify it now using my existing tweeters and woofers. Thank you Sreten! ...grant
Hi,
I was looking a the specs of the wrong D25 it seems...
(The D25AG-35-06 listed in your first post)
You would need to find the specs for your tweeter,
or try asking vifa what is a currrent equivalent ?
On a budget consider the Hi-Vi SD1.1 as your new tweeter.
Note this will save you 3 crossover components also.
At 40 / 45 L the drivers are borderline between sealed and vented
loading. So sealed and saving some money on the inductor it is.
Note the baffle step for the woofer, the baffle peak for the mid,
0dB seems to the same for the first two, but not the tweeter.
The attenuation required is the difference between the red + grey.
If you go for it note the mid and treble resistors can be varied.
Also note that using the tools and the data you already have on
the mid you could derive the response ripple caused by the baffle.
Again using the tools you could then use a different mid bass.
I would use the Tangband W5-704S as a budget choice.
🙂/sreten.
I was looking a the specs of the wrong D25 it seems...
(The D25AG-35-06 listed in your first post)
You would need to find the specs for your tweeter,
or try asking vifa what is a currrent equivalent ?
On a budget consider the Hi-Vi SD1.1 as your new tweeter.
Note this will save you 3 crossover components also.
At 40 / 45 L the drivers are borderline between sealed and vented
loading. So sealed and saving some money on the inductor it is.
An externally hosted image should be here but it was not working when we last tested it.
Note the baffle step for the woofer, the baffle peak for the mid,
0dB seems to the same for the first two, but not the tweeter.
The attenuation required is the difference between the red + grey.
If you go for it note the mid and treble resistors can be varied.
Also note that using the tools and the data you already have on
the mid you could derive the response ripple caused by the baffle.
Again using the tools you could then use a different mid bass.
I would use the Tangband W5-704S as a budget choice.
🙂/sreten.
Sreten, Hi,
Thats a great call on your new driver suggestions... good sound on a tight budget is what I'm all about! As you know, Zaph has tested both the Hi-Vi SD1.1A and the TangBand W5-704S and gave
good reports for both considering they are budget drivers. The HiVi tweeter looks particularly good...yeah, I like its spooky but fun 'eyeball' appearance! (pic attached). The rising response would suit my old ears too!
Re:"On a budget consider the Hi-Vi SD1.1 as your new tweeter. Note this will save you 3 crossover components also." ... I presume you mean the notch filter?
The TB mid seems to have a huge impedance curve though. On the TB site there is a W5-704D version only, which I assume is an improved model. Unfortunately both HiVi and TB are not available here in Au - I googled both and no local suppliers? The Seas 27TFFC here is about $50Au and the MCA15RCY is about $86Au. So I might not save much after importing? The bottom line is: my choice will still be the Seas 27TFFC and MCA15RCY as they are well respected and available here.
I'm sorry I misquoted my Vifa tweeters on page 1, I did email the importer earlier, but they didn't suggest an equivalent.
Right!, I guess the P25 can be ok in a sealed box...which you say is advisable..no problem for me there as your coils' DCR is 0.5 to 1 R, which I assume increases Qts? Would you please elaborate on your 'closed' box reasoning for this driver?
Also, would you have any idea what the James tweeter 0dB is please? Its strange that they are not aligned. I guess the M and W are at about 90dB, ie the 0dB reference? Re:..."If you go for it note the mid and treble resistors can be varied." ...but, the R2071 mid resistor seems odd? Maybe it should be added to R2011 (and deleted)? And the HP filter should be put first?
About using 'the FRC tools'..well, I only have Speaker Workshop now. It would be impossible for me to model the PFM-Special which has an open baffle mid, sadly there's no option for it in SW.
Re:" Also note that using the tools and the data you already have on the mid you could derive the response ripple caused by the baffle."...you're smarter than I am, lol, any clues? thanks Sreten, grant ..(your reference in another thread to Zaph's forthcoming HiVi/TB design is interesting!)
Thats a great call on your new driver suggestions... good sound on a tight budget is what I'm all about! As you know, Zaph has tested both the Hi-Vi SD1.1A and the TangBand W5-704S and gave
good reports for both considering they are budget drivers. The HiVi tweeter looks particularly good...yeah, I like its spooky but fun 'eyeball' appearance! (pic attached). The rising response would suit my old ears too!
Re:"On a budget consider the Hi-Vi SD1.1 as your new tweeter. Note this will save you 3 crossover components also." ... I presume you mean the notch filter?
The TB mid seems to have a huge impedance curve though. On the TB site there is a W5-704D version only, which I assume is an improved model. Unfortunately both HiVi and TB are not available here in Au - I googled both and no local suppliers? The Seas 27TFFC here is about $50Au and the MCA15RCY is about $86Au. So I might not save much after importing? The bottom line is: my choice will still be the Seas 27TFFC and MCA15RCY as they are well respected and available here.
I'm sorry I misquoted my Vifa tweeters on page 1, I did email the importer earlier, but they didn't suggest an equivalent.
Right!, I guess the P25 can be ok in a sealed box...which you say is advisable..no problem for me there as your coils' DCR is 0.5 to 1 R, which I assume increases Qts? Would you please elaborate on your 'closed' box reasoning for this driver?
Also, would you have any idea what the James tweeter 0dB is please? Its strange that they are not aligned. I guess the M and W are at about 90dB, ie the 0dB reference? Re:..."If you go for it note the mid and treble resistors can be varied." ...but, the R2071 mid resistor seems odd? Maybe it should be added to R2011 (and deleted)? And the HP filter should be put first?
About using 'the FRC tools'..well, I only have Speaker Workshop now. It would be impossible for me to model the PFM-Special which has an open baffle mid, sadly there's no option for it in SW.
Re:" Also note that using the tools and the data you already have on the mid you could derive the response ripple caused by the baffle."...you're smarter than I am, lol, any clues? thanks Sreten, grant ..(your reference in another thread to Zaph's forthcoming HiVi/TB design is interesting!)
Attachments
Omni,
My friend, I hope your all your effort is close now to a very pleasing result..make that a grand first performance! Very best wishes with it indeed. Keep us posted, it must be soon now, but no pressure, do it right, the first time! cheers mate, grant
My friend, I hope your all your effort is close now to a very pleasing result..make that a grand first performance! Very best wishes with it indeed. Keep us posted, it must be soon now, but no pressure, do it right, the first time! cheers mate, grant
grantnsw said:
Hi,
Shown is 0R and 1R resistor - assuming QTS = 0.28 is accurate for the driver.
Seems not really worth the effort to vent. In this case I would
say the sealed version would sound better than a vented.
roll-off rate at -6dB is as important as -6dB point.
🙂/sreten.
Attachments
grantnsw said:
1) I guess nominal tweeter sensitivity.
2) R2071 should not be added to R2011.
🙂/sreten.
grantnsw said:
I saw this and thought I better comment...
The Hi-Vi SD1.1A is good if you get it from Madisound. It's not good if you get it from Parts Express. I'll explain in more detail in my blog when I get a moment this weekend.
It will be a blog update with a bunch of depressing complaints about driver consistency. 🙁
Sreten, thanks!
Your reason for 44 litre closed is very convincing.
Well manuf's specs may vary, the P25 Qts could be 0.28 ...+- 10 (+?) %. I assume a series 0 R is similar to a very low series coil DCR, ie your closed 'blue curve' whereas a series 1 R , (or coils DCR) is
your preferable 'yellow curve'. I hope I've got this right?
The closed yellow curve would sound better due to 'average' room gain, I think. So, no reason to go vented!
The -6dB rolloff rate at about 43Hz is I hope what you're referring to, for your yellow curve?
Hmm, I just had another look and I may have mixed up the curves?
Re: '0 dB' being 'nominal tweeter sensitivity'...thanks. Re: not adding R2071 and R2011...the reasons are probably beyond me, lol, but I'd love to know why, as they are in series.
Zaph,
Many thanks for your comment, I'm glad you posted here, and eagerly awaiting your blog.
cheers all, grant
Your reason for 44 litre closed is very convincing.
Well manuf's specs may vary, the P25 Qts could be 0.28 ...+- 10 (+?) %. I assume a series 0 R is similar to a very low series coil DCR, ie your closed 'blue curve' whereas a series 1 R , (or coils DCR) is
your preferable 'yellow curve'. I hope I've got this right?
The closed yellow curve would sound better due to 'average' room gain, I think. So, no reason to go vented!
The -6dB rolloff rate at about 43Hz is I hope what you're referring to, for your yellow curve?
Hmm, I just had another look and I may have mixed up the curves?
Re: '0 dB' being 'nominal tweeter sensitivity'...thanks. Re: not adding R2071 and R2011...the reasons are probably beyond me, lol, but I'd love to know why, as they are in series.
Zaph,
Many thanks for your comment, I'm glad you posted here, and eagerly awaiting your blog.
cheers all, grant
grantnsw said:
Your shiny eyeball means you got one of the good ones. A dull dome that is hard to see though is likely a poor performer. [image][/image][image] Note that the W5-704S has proven to be consistent over the years. I've tested 4 pairs total over a 2 year period and they have all been the same.
John[/image]
Hi Zaph,
Very nice to met you!
How (come bye) your graphs (on your site) say freq.output/phase/impedance and phase never shows up. Am'I missing something here?
Nice of you to stop bye.
Very nice to met you!
How (come bye) your graphs (on your site) say freq.output/phase/impedance and phase never shows up. Am'I missing something here?
Nice of you to stop bye.
Hi John,
Thanks for your blog update. You're right its depressing, but being fore-warned is very useful. It seems that to guarantee consistency and performance the best choice is expensive ScanSpeak. I guess the more affordable Seas Prestige line is pretty good too from a consistency viewpoint!
Hi Sreten,
I've had a good look at your last WinISD plots. I couldn't figure out why all your 4 coloured responses seemed to almost converge to *only* about 14-16dB down at the Vifa P25's stated Fs of 24 Hz. It
seems very weird to me that the response at Fs (and below ) is still relatively high? I thought it should be much lower.
So, I had a go with it myself in WinISD ( plot attached). My red curve looks almost identical (possibly different port dimensions?) to yours but you say your 'red curve' is with the series 1 Ohm resistor?
Now I'm really confused! How can this be so?
Also please, for our similar 'yellow closed' 44 Litre reponses with 0 series R , I thought, from our previous discussion this would be best when room gain is added in? Or have I totally lost it? lol. I just can't see how a 1 Ohm series resistor would yield the rising responses in your blue and red plots. Can you help me out here please? I really would like to know. Thanks, grant
Thanks for your blog update. You're right its depressing, but being fore-warned is very useful. It seems that to guarantee consistency and performance the best choice is expensive ScanSpeak. I guess the more affordable Seas Prestige line is pretty good too from a consistency viewpoint!
Hi Sreten,
I've had a good look at your last WinISD plots. I couldn't figure out why all your 4 coloured responses seemed to almost converge to *only* about 14-16dB down at the Vifa P25's stated Fs of 24 Hz. It
seems very weird to me that the response at Fs (and below ) is still relatively high? I thought it should be much lower.
So, I had a go with it myself in WinISD ( plot attached). My red curve looks almost identical (possibly different port dimensions?) to yours but you say your 'red curve' is with the series 1 Ohm resistor?
Now I'm really confused! How can this be so?
Also please, for our similar 'yellow closed' 44 Litre reponses with 0 series R , I thought, from our previous discussion this would be best when room gain is added in? Or have I totally lost it? lol. I just can't see how a 1 Ohm series resistor would yield the rising responses in your blue and red plots. Can you help me out here please? I really would like to know. Thanks, grant
Attachments
Hi Sreten,
Thanks for your re-posted 'mhsoft' link, I finally tried it with a series 1R on the P25, which gives a new of Qts 0.32 from 0.28 originally. I tried to do it in WinISD, but how should the new parameters be specified please? I just can't seem to get the new Qts value to 'save'. I followed the help-file examples as best I could. Any clues please as I would like to try this myself. thanks, grant
Thanks for your re-posted 'mhsoft' link, I finally tried it with a series 1R on the P25, which gives a new of Qts 0.32 from 0.28 originally. I tried to do it in WinISD, but how should the new parameters be specified please? I just can't seem to get the new Qts value to 'save'. I followed the help-file examples as best I could. Any clues please as I would like to try this myself. thanks, grant
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