Hello all:
I have a pair of Jensen SG-300 (Heathkit AS-27) "Triax" 12" speaker drivers, that I currently house (on interim basis) in a pair of large, ported boxes (approx 24" wide, 36" high, 18 " deep) - designed for a full-range Wharfdale speaker driver.
The drivers are very similar in design to the Jensen G-610 (15" diameter vs mine which is 12"), with the horn integrated into the woofer, and a tweeter suspended in front (seems to me the series to which this speaker belongs was released a bit after the G-610) .
here is a link to an old ad describing the SG-300 :
http://www.tubularradio.com/jensenSigmabrochure.html
I'm unable to find evidence as to what Jensen recommended for the SG-300 in terms of speaker box, but I do understand that Jensen proposed either the Imperial or the "Ultraflex" (aka Onken box precursor) speaker box design for the G-610 - Jensen included in their designs sizes that would work for 12" speakers, so I am guessing that either design might be a nice fit for mine.
From another forum, here are some generic specs measured on someone else's pair -
SPL 98.3
Re 5.35
Fs 34 Hz
Qts .35
Le .035
Mms 40.2
Vas 15.
I would assume that these measurements give some idea about the design of the drivers, and thus what kind of box would be best for them.
They are being driven by 10 W from a SE-tube amp.
I'm looking for advice on a design for their permanent home - for 2 reasons :
1) They sound great, but I suspect that they could sound better in boxes that are optimized for them.
2) We are about to move into a condo, and floor space is a premium.
I likely would not build them myself but I think I have a contact here in Montreal who could help with the cabinet design and build. Suggestions of kits / blueprints etc. would be welcome ! I'd also be open to recommendations of folk in the Montreal or Ottawa region of Canada who might be able to help - in case my suggested contact doesn't work out.
Thanks so much !
I have a pair of Jensen SG-300 (Heathkit AS-27) "Triax" 12" speaker drivers, that I currently house (on interim basis) in a pair of large, ported boxes (approx 24" wide, 36" high, 18 " deep) - designed for a full-range Wharfdale speaker driver.
The drivers are very similar in design to the Jensen G-610 (15" diameter vs mine which is 12"), with the horn integrated into the woofer, and a tweeter suspended in front (seems to me the series to which this speaker belongs was released a bit after the G-610) .
here is a link to an old ad describing the SG-300 :
http://www.tubularradio.com/jensenSigmabrochure.html
I'm unable to find evidence as to what Jensen recommended for the SG-300 in terms of speaker box, but I do understand that Jensen proposed either the Imperial or the "Ultraflex" (aka Onken box precursor) speaker box design for the G-610 - Jensen included in their designs sizes that would work for 12" speakers, so I am guessing that either design might be a nice fit for mine.
From another forum, here are some generic specs measured on someone else's pair -
SPL 98.3
Re 5.35
Fs 34 Hz
Qts .35
Le .035
Mms 40.2
Vas 15.
I would assume that these measurements give some idea about the design of the drivers, and thus what kind of box would be best for them.
They are being driven by 10 W from a SE-tube amp.
I'm looking for advice on a design for their permanent home - for 2 reasons :
1) They sound great, but I suspect that they could sound better in boxes that are optimized for them.
2) We are about to move into a condo, and floor space is a premium.
I likely would not build them myself but I think I have a contact here in Montreal who could help with the cabinet design and build. Suggestions of kits / blueprints etc. would be welcome ! I'd also be open to recommendations of folk in the Montreal or Ottawa region of Canada who might be able to help - in case my suggested contact doesn't work out.
Thanks so much !
Pioneer's basic BR = 15 L/1.44 = ~10.42 L net volume (Vb), box tuning (Fb) = measured Fs whereas fir T/S, the default is max flat =
net volume (Vb) (L) = 20*15*0.35^3.3 = ~9.39 L
box tuning (Fb) (Hz) = 0.42*34*0.35^-0.96 = ~39.12 Hz
That said, your amp probably has a high output impedance, so ideally need to know its resistance or at least its DF to calculate it, then adjust the 0.35 Qts to its Qts' and recalculate its Vb, Fb, though if it's high or outright a matching impedance (~8 ohms), then best overall to tune to Fs regardless for max bass efficiency.
[Qts']: [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
That said, had 'brain fade' in that the 15 is likely in ft^3, so.........
BR = 424.753 L/1.44 = ~294.47 L/ 10.4 ft^3 net volume (Vb)
net volume (Vb) (L) = 20*424.753*0.35^3.3 = ~265.82 L/9.388 ft^3
.........which is more in line with tube era cab sizes and tuning was typically at ~ Fs when both impedance peaks have equal amplitudes.
If too large, then guess you'll have to make them as big as you can and tune to Fs, though nowadays we tend to make them much taller and mount the driver at ~seated ear height at an offset of ~L*0.349 to 'shrink' its footprint as much as practical and put the vent down near/at the bottom to get some TL acoustic loading for greater vent efficiency.
For instance, a popular seated ear height is ~38" so assuming 3/4" (1.8 cm) thick panels, this equates to an internal (i.d.) height = ~56".
edit: Historically a kitchen, etc., cabinet maker would build to spec for reasonable prices, at least in my locale of Atlanta, Ga, though for fine furniture finish, those shops tended to 'demand' a (not so) small fortune plus long delivery times.
net volume (Vb) (L) = 20*15*0.35^3.3 = ~9.39 L
box tuning (Fb) (Hz) = 0.42*34*0.35^-0.96 = ~39.12 Hz
That said, your amp probably has a high output impedance, so ideally need to know its resistance or at least its DF to calculate it, then adjust the 0.35 Qts to its Qts' and recalculate its Vb, Fb, though if it's high or outright a matching impedance (~8 ohms), then best overall to tune to Fs regardless for max bass efficiency.
[Qts']: [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
That said, had 'brain fade' in that the 15 is likely in ft^3, so.........
BR = 424.753 L/1.44 = ~294.47 L/ 10.4 ft^3 net volume (Vb)
net volume (Vb) (L) = 20*424.753*0.35^3.3 = ~265.82 L/9.388 ft^3
.........which is more in line with tube era cab sizes and tuning was typically at ~ Fs when both impedance peaks have equal amplitudes.
If too large, then guess you'll have to make them as big as you can and tune to Fs, though nowadays we tend to make them much taller and mount the driver at ~seated ear height at an offset of ~L*0.349 to 'shrink' its footprint as much as practical and put the vent down near/at the bottom to get some TL acoustic loading for greater vent efficiency.
For instance, a popular seated ear height is ~38" so assuming 3/4" (1.8 cm) thick panels, this equates to an internal (i.d.) height = ~56".
edit: Historically a kitchen, etc., cabinet maker would build to spec for reasonable prices, at least in my locale of Atlanta, Ga, though for fine furniture finish, those shops tended to 'demand' a (not so) small fortune plus long delivery times.
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Thank you for that info - that kind of volume is consistent with what I had heard. I'm curious to learn more about you comment on the height - would it be possible to have a "taller - thinner" speaker for these kinds of drivers ?
Correct, though of course 'thinner' is relative to being narrower than a shorter/wider cab of the same net volume (Vb).
Anyway, above a ~36" i.d. height, a cab's 1/4 WL closed cylinder/pipe (TL) modes develop enough to start preloading (damping) the vent's output and in the larger (up to 30 ft^3), taller Altec and similar cabs I'm most known for the loading is strong enough to not just shorten the vent, but to make it a bit larger in area as a simple baffle thickness (reflex) vent for extremely well damped bass performance.
Smoothest overall response is when the driver is at an odd harmonic of the i.d. height (L) with L*0.349 the best overall, hence the need to know where the driver height is best suited overall in your app.
Anyway, above a ~36" i.d. height, a cab's 1/4 WL closed cylinder/pipe (TL) modes develop enough to start preloading (damping) the vent's output and in the larger (up to 30 ft^3), taller Altec and similar cabs I'm most known for the loading is strong enough to not just shorten the vent, but to make it a bit larger in area as a simple baffle thickness (reflex) vent for extremely well damped bass performance.
Smoothest overall response is when the driver is at an odd harmonic of the i.d. height (L) with L*0.349 the best overall, hence the need to know where the driver height is best suited overall in your app.
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