Don't mention it, Rich, it was no trouble. Still, perhaps there is a thing or two that might improve on the bass. I can't say I recall reading about it, but would you say a few words on how much you have inner volume to spare, vent measures and how exactly and where did you put stuffing/lining. Is there an air flow blockage or too small of a volume at disposal? I know 6.5" Peerless PPB's have got so much bass in 18 litres that I suppose most of the audiophiles would have been very happy with it, not to mention an 8" woofer is a better bass player by default.
Hi Lojzek,
I have about 38 liters available but I am only using 27 liters. This was based on comments by diyaudio member Michael Chua's recommendations on improving bass dynamics of the Peerless 830869 8" woofer. It would be easy at some point to expand voulume if necessary. I'm using 3" port tubes flared on both ends 11.5 inches long. My desired port tuning was 38 hz but it looks like from nearfield measurements and impedance graphs that it is more like 41 hz. I lined walls with about 1 inch thick fiberglass and was careful not to block the vent.
What do you think of this idea? I have 2 JBL woofers 15 inch diameter that where pulled from cabinets in a sealed alignment. Would it work well to build one or two separate sealed boxes for these and use them as sub woofers? Also, go from ported to sealed on the Peerless 830869 woofers. It looks like in Unibox that 27 liters sealed is about perfect for that woofer. To my thinking, it seems like a logical plan and not very costly since I already have the woofers.
Your thoughts are Appreciated,
Rich
I have about 38 liters available but I am only using 27 liters. This was based on comments by diyaudio member Michael Chua's recommendations on improving bass dynamics of the Peerless 830869 8" woofer. It would be easy at some point to expand voulume if necessary. I'm using 3" port tubes flared on both ends 11.5 inches long. My desired port tuning was 38 hz but it looks like from nearfield measurements and impedance graphs that it is more like 41 hz. I lined walls with about 1 inch thick fiberglass and was careful not to block the vent.
What do you think of this idea? I have 2 JBL woofers 15 inch diameter that where pulled from cabinets in a sealed alignment. Would it work well to build one or two separate sealed boxes for these and use them as sub woofers? Also, go from ported to sealed on the Peerless 830869 woofers. It looks like in Unibox that 27 liters sealed is about perfect for that woofer. To my thinking, it seems like a logical plan and not very costly since I already have the woofers.
Your thoughts are Appreciated,
Rich
Hi Rich, adding extra woofers is always viable, bearing in mind the sensitivity match and the way it'll be crossed over. But I am afraid 27 litres is exactly what's keeping you from achieving an optimum. We can all simulate stuff with manufacturer's TSP, yet I am interested if you attempted to measure yourself, the woofer parameters? If it were me, I'd always try to employ all the potentials of a unit before resorting to any other driver helpers. JBl's are mighty loud, I assume?
Hi Lojzek,
Thanks for sharing your thoughts.
I may try expanding the box volume to 38 liters. It looks like from Unibox and Winisd that 38 liters tuned to 36 hz is about perfect. Does that sound correct to you.? I did not measure TS parameters myself. It was a decision based on what others had tried and found successful for them. I knew going in, that there was a possibility that lack of volume could be an issue and that's why I left room to expand if required. Every once in awhile I guess correctly.
Best Regards,
Rich
Thanks for sharing your thoughts.
I may try expanding the box volume to 38 liters. It looks like from Unibox and Winisd that 38 liters tuned to 36 hz is about perfect. Does that sound correct to you.? I did not measure TS parameters myself. It was a decision based on what others had tried and found successful for them. I knew going in, that there was a possibility that lack of volume could be an issue and that's why I left room to expand if required. Every once in awhile I guess correctly.Best Regards,
Rich
It certainly sounds better for deeper bass. Leave the vent unchanged. Have you got an impedance measurement of a woofer in free air? If yes, then I'd ask you to export a zma file of it so I can calculate the Qms and Qes, curious only. My TSP measurements of the smaller 6.5" proved to be different than manufacturer's but the tuning remained the same when simulated. People often have their own preferences and I am no exception. Mine is to give woofer a chance to dig as deep as feasible, and your Peerless works like that in the 60 litres area. Someone said " we live in the midrange", but that is far from the truth. We live in all three major frequency ranges, and bass compromised is just silly, IMO.
Hi Lojzek,
It is no bother at all. This is fun stuff. It helps me to learn more about speaker design and building. The only reason I asked is I have used every sizable plywood in building these speakers and it is near blizzard conditions in North Idaho today to go out and buy a piece for a test baffle.
As always your help is Appreciated,
Rich
It is no bother at all. This is fun stuff.
It helps me to learn more about speaker design and building. The only reason I asked is I have used every sizable plywood in building these speakers and it is near blizzard conditions in North Idaho today to go out and buy a piece for a test baffle.As always your help is Appreciated,
Rich
Hi Lojzek,
I have attached a .txt file for your consideration. This is TSP taken from Room EQ Wizard based on the two impedance files I sent you in the last post. If everything is done accurately enough a 38 liter box is way under sized for this driver. It looks like from my sims in Unibox that this driver will do much better in a 70-80 liter box tuned to around 35 hz ( F3= 33-35hz). Obviously, I won't be able to increase volume to that size but I could increase from 27 liters to 38 liters but that will only help a slight amount. Most of the parameters are close to either the manufacture's or third part ones I have found. The one exception is Vas = 97.41 that reading seems a bit high. My best alternative might be to go the sealed route and add a sub in a sealed box to fill in the lowest bass region. Just thinking out loud.
As Always your thoughts are Appreciated,
Rich
I have attached a .txt file for your consideration. This is TSP taken from Room EQ Wizard based on the two impedance files I sent you in the last post. If everything is done accurately enough a 38 liter box is way under sized for this driver. It looks like from my sims in Unibox that this driver will do much better in a 70-80 liter box tuned to around 35 hz ( F3= 33-35hz). Obviously, I won't be able to increase volume to that size but I could increase from 27 liters to 38 liters but that will only help a slight amount. Most of the parameters are close to either the manufacture's or third part ones I have found. The one exception is Vas = 97.41 that reading seems a bit high. My best alternative might be to go the sealed route and add a sub in a sealed box to fill in the lowest bass region. Just thinking out loud.
As Always your thoughts are Appreciated,
Rich
Interesting findings. Did some calculations and according to your free air measurements following parameters came out.
Fs=33 Hz
Qms=4.61
Qes=0.365
Qts=0.338
Vas=85.5 lit
Re=6.1
I advise to try out this 38 litres option and shorten the vent legth to about 6". Using new TSP and comparing these:
27 litres, Fb=38 Hz, vent 11.5"
F3/F6/F10=54/42/34 Hz
38 litres, Fb=41 Hz, vent 6.2"
F3/F6/F10=44/37/32 Hz
To confirm the added mass measurement went good, use 15 g or similar.
Try the same procedure with 15" woofers, only with more mass weights, like 40 g.
Fs=33 Hz
Qms=4.61
Qes=0.365
Qts=0.338
Vas=85.5 lit
Re=6.1
I advise to try out this 38 litres option and shorten the vent legth to about 6". Using new TSP and comparing these:
27 litres, Fb=38 Hz, vent 11.5"
F3/F6/F10=54/42/34 Hz
38 litres, Fb=41 Hz, vent 6.2"
F3/F6/F10=44/37/32 Hz
To confirm the added mass measurement went good, use 15 g or similar.
Try the same procedure with 15" woofers, only with more mass weights, like 40 g.
Hi Lojzek,
I have attached .zma files for JBL 15 inch woofer for your consideration. I also added a screenshot from Unibox in a volume that is sensible to build anything larger then that I would look for another woofer. But, I'm still going to expand existing cab to 38 liters and see what difference that makes before deciding on adding a sub woofer. Here is my TSP as calculated in REW:
Re=6.85
Qms= 4.15
Qes=0.69
Qts=0.592
Vas=454.27
Le=2.22
Fs=27.3
I used 45 grams of weight for this driver.
Thanks so much,
Rich
I have attached .zma files for JBL 15 inch woofer for your consideration. I also added a screenshot from Unibox in a volume that is sensible to build anything larger then that I would look for another woofer. But, I'm still going to expand existing cab to 38 liters and see what difference that makes before deciding on adding a sub woofer. Here is my TSP as calculated in REW:
Re=6.85
Qms= 4.15
Qes=0.69
Qts=0.592
Vas=454.27
Le=2.22
Fs=27.3
I used 45 grams of weight for this driver.
Thanks so much,
Rich
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Hi again Rich, did a little more calculations and it looks as if the JBL in a 116 litres enclosure would have achieved slightly worse cut-off frequencies comparing to an extended volume version for Peerless.
The thing with this large woofers is these work better in larger volumes. This is your show, so you get to make the calls. I'd rather build new larger enclosures for Peerless and avoid complications turning it into a 3 way, especially a passive one ( nightmare. Still, there is a chance you could be satisfied with the extended version.
The thing with this large woofers is these work better in larger volumes. This is your show, so you get to make the calls. I'd rather build new larger enclosures for Peerless and avoid complications turning it into a 3 way, especially a passive one ( nightmare
. Still, there is a chance you could be satisfied with the extended version.
Hi Lojzek,
The things you mentioned concerning JBL woofers is exactly my thoughts as well. There is no benefit in low frequency extension with going that route. I'm going to take my time and consider what might work the best. I really appreciate all the help you provided on this project.
Best Regards,
Rich
The things you mentioned concerning JBL woofers is exactly my thoughts as well. There is no benefit in low frequency extension with going that route. I'm going to take my time and consider what might work the best. I really appreciate all the help you provided on this project.
Best Regards,
Rich
You are welcome. Keep experimenting, it will teach you all kinds of stuff, and remember to make your own measurements, TSP and FR. It will save you from making wrong decisions and explain why things are what they are, more or less. It does not matter so much what anyone personally thinks on the topic. See you.
Hi Tony,
It is great to hear from you! I certainly am having fun with this project and it has been a real learning experience. With each build, I am starting to gather the concepts that make for nice sounding speakers. But, the fun has to come to an end. It's time for me to go back to work for the season. Then next winter try to decide on what to build next. It seems there is always 'just one more'.
Take Care,
Rich
It is great to hear from you! I certainly am having fun with this project and it has been a real learning experience.
With each build, I am starting to gather the concepts that make for nice sounding speakers. But, the fun has to come to an end. It's time for me to go back to work for the season. Then next winter try to decide on what to build next. It seems there is always 'just one more'.Take Care,
Rich
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