Hi all -
Im after a bit of help. I found some Shahinian Arcs missing their bass drivers. They were cheap, the woofers Im guessing blew. The passive radiator is also missing.
Im working on a bit of a hit & miss approach. The tweeters are still working, the mids are blown (I will get to those) however in the meatnime I want to sort out the bass.
I've been recommended a pair of Scanspeak P21WO20 8" drivers for my purpose. One issue is cost & shipping. Given todays climate the cost is unjustifiably high to get these. I live in New Zealand.
I have found a pair of 830869 Peerless drivers to fit. I will need to mod the cutout a little bit to fit these. Im not after perfection, I have modded and fixed up several pairs of speakers before.
Anyway, the 830869 specs are almost identical to what I need (I have the T/S specs of the original woofers). That is, apart from QMS, which is about double of what I need, at 4.4.
The original woofer T/S specs were given to me by someone else who worked on what seems to be the same era of Arcs; the specs are (for one measured, ageing woofer): Fs = 24.2 Hz, Vas = 2.95 cu ft, Qts = 0.28, Qes = 0.32, Qms = 2.30, Mms = 29.9 gm, Re = 3.52 ohms, SPL = 87 dB, Le = 0.32 mH.
Im not sure of the overall cabinet size, however due to the design, the above woofer worked well in it. There is also a 10 inch passive radiator weighing approx 100gm in the original design. From what I have read on this, the QMS may not be the most importance factor in considering performance in this box (after all, its only one T/S factor). Many have said in discussions that it could also make for a livelier woofer with more engaging performance.
The data on the 830869 is here: https://www.wagneronline.com.au/pee...rivers/audio-speakers-pa/830869-7151/3245/pd/
Note that it has a bit of a peak at around 5Khz (but I presume the xover will roll it off before then. The 830869 has good Vas and Fs (I cant find many drivers at all matching these numbers). Of course, I will also need to address the different impedance vs shifting xover frequency issue.
Are there any views on this?
thanks in advance
Im after a bit of help. I found some Shahinian Arcs missing their bass drivers. They were cheap, the woofers Im guessing blew. The passive radiator is also missing.
Im working on a bit of a hit & miss approach. The tweeters are still working, the mids are blown (I will get to those) however in the meatnime I want to sort out the bass.
I've been recommended a pair of Scanspeak P21WO20 8" drivers for my purpose. One issue is cost & shipping. Given todays climate the cost is unjustifiably high to get these. I live in New Zealand.
I have found a pair of 830869 Peerless drivers to fit. I will need to mod the cutout a little bit to fit these. Im not after perfection, I have modded and fixed up several pairs of speakers before.
Anyway, the 830869 specs are almost identical to what I need (I have the T/S specs of the original woofers). That is, apart from QMS, which is about double of what I need, at 4.4.
The original woofer T/S specs were given to me by someone else who worked on what seems to be the same era of Arcs; the specs are (for one measured, ageing woofer): Fs = 24.2 Hz, Vas = 2.95 cu ft, Qts = 0.28, Qes = 0.32, Qms = 2.30, Mms = 29.9 gm, Re = 3.52 ohms, SPL = 87 dB, Le = 0.32 mH.
Im not sure of the overall cabinet size, however due to the design, the above woofer worked well in it. There is also a 10 inch passive radiator weighing approx 100gm in the original design. From what I have read on this, the QMS may not be the most importance factor in considering performance in this box (after all, its only one T/S factor). Many have said in discussions that it could also make for a livelier woofer with more engaging performance.
The data on the 830869 is here: https://www.wagneronline.com.au/pee...rivers/audio-speakers-pa/830869-7151/3245/pd/
Note that it has a bit of a peak at around 5Khz (but I presume the xover will roll it off before then. The 830869 has good Vas and Fs (I cant find many drivers at all matching these numbers). Of course, I will also need to address the different impedance vs shifting xover frequency issue.
Are there any views on this?
thanks in advance
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My experience with Passive Radiator is limited to one implementation, so will not claim any "authority" on this.
Anyway, since no-one responded I here is how I would approach the issue.
Hopefully someone with more practical experience can chime in with advice and comments.
My approach was to first measure the internal volume of the bass cabinet.
Then I plugged the cabinet volume and driver specifications into software that can predict Bass performance of PR boxes.
I use the UNIBOX excel sheet http://audio.claub.net/software/kougaard/ubmodel.html
When using Unibox, I often add about 0.5 ohm DC resistance in series with the element to account for the Coil influence on TS parameters.
Run predictions with different weights on the PR radiator until a reasonable frequency response is achieved. You may also want to check how reducing internal volume will influence the response.
If you have the required equipment you may want to run an impedance plot on the speaker to verify how real life performance compares to the calculated alignment.
An alternative to purchasing a PR may be to route a disk that can block the PR cutout. Hence, I would also use Unibox to check sealed and vented performance in your box.
Then as you point out yourself, it is time to address the crossover.
Anyway, since no-one responded I here is how I would approach the issue.
Hopefully someone with more practical experience can chime in with advice and comments.
My approach was to first measure the internal volume of the bass cabinet.
Then I plugged the cabinet volume and driver specifications into software that can predict Bass performance of PR boxes.
I use the UNIBOX excel sheet http://audio.claub.net/software/kougaard/ubmodel.html
When using Unibox, I often add about 0.5 ohm DC resistance in series with the element to account for the Coil influence on TS parameters.
Run predictions with different weights on the PR radiator until a reasonable frequency response is achieved. You may also want to check how reducing internal volume will influence the response.
If you have the required equipment you may want to run an impedance plot on the speaker to verify how real life performance compares to the calculated alignment.
An alternative to purchasing a PR may be to route a disk that can block the PR cutout. Hence, I would also use Unibox to check sealed and vented performance in your box.
Then as you point out yourself, it is time to address the crossover.
