Hi,
Just want to gather opinions here WRT to suitable enclosures for the 215 RTF64.
http://www.supravox.fr/haut_parleurs/215_RTF.htm
I know S-vox is renowned for their drivers in OB. But I'm not going that path this time as I already have OB speakers using high Q vintage drivers (I just lack a good sub to fill in from 50-40Hz below for more demanding material)... Although still usable for OB, the RTF64 is not really the most ideal for it in S-vox's line up anyways. They have the slightly more pricey 215 Signatures for that.
I want to try pipes or quarter-wave designs for a new project this time.
1.) The general design suggested by S-vox for the 215 series looks nice but maybe there is room for improvement:
http://www.supravox.fr/kits/tqwt215.pdf
What do you think?
2.) Another design I'm contemplating is a pipe/blh with a Karlson vent:
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=PLAN.gif
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=PLANS-2.gif
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=BRACE.gif
(should read 1" x 4" bracing)
We built a pair of these before w/ oridnary ply and it sounds great with low Q drivers so far (tried with both FE207E and EX2's). I asked the designer (Bill Woods) who kindly shared it in the public domain for diy if a higher Qts driver like the S-vox would sound good in 'em. He told me that the only way to know is to actually try. Well, before letting go of considerable $ I'd like to know what you guys think. *He did a sim comparison Vs. JBL LE8TH using Akabak and sent me the response graph linked below. The dips are said to be artifacts of Akabak, but IME trying out high Qts drivers in backhorn or pipe designs is that they tend to sound boomy with midbass suckout. The not so encouraging part is that the designer says they LE8TH is quite bass heavy in that enclosure. Both the S-vox and JBL driver have very similar Q, although other parameters like Vas are far from each other: http://members.aol.com/IKSchiffer/jbl/bigbrother.html
*Akabak sim LE8 vs. RTF64 on K-lsot vented pipe:
http://pic4.picturetrail.com/VOL706/2663514/5325320/114959946.jpg
3.) Another that is of interest is the Singular enclosure (interesting backchamber with Helmholtz resonator). It’s said to work well with medium Qts drivers up to .6 or so. Will try this path too… http://www.bd-design.nl/contents/en-uk/d83.html
Of course there is the cool BIB design, with dims graciously provided by GM. However, width and depth is too large for my room I’m afraid.
Anything you may share would be greatly appreciated. Thanks for reading the longish post.
regards,
fred
Just want to gather opinions here WRT to suitable enclosures for the 215 RTF64.
http://www.supravox.fr/haut_parleurs/215_RTF.htm
I know S-vox is renowned for their drivers in OB. But I'm not going that path this time as I already have OB speakers using high Q vintage drivers (I just lack a good sub to fill in from 50-40Hz below for more demanding material)... Although still usable for OB, the RTF64 is not really the most ideal for it in S-vox's line up anyways. They have the slightly more pricey 215 Signatures for that.
I want to try pipes or quarter-wave designs for a new project this time.
1.) The general design suggested by S-vox for the 215 series looks nice but maybe there is room for improvement:
http://www.supravox.fr/kits/tqwt215.pdf
What do you think?
2.) Another design I'm contemplating is a pipe/blh with a Karlson vent:
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=PLAN.gif
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=PLANS-2.gif
http://gallery.audioasylum.com/cgi/gi.mpl?u=21168&f=BRACE.gif
(should read 1" x 4" bracing)
We built a pair of these before w/ oridnary ply and it sounds great with low Q drivers so far (tried with both FE207E and EX2's). I asked the designer (Bill Woods) who kindly shared it in the public domain for diy if a higher Qts driver like the S-vox would sound good in 'em. He told me that the only way to know is to actually try. Well, before letting go of considerable $ I'd like to know what you guys think. *He did a sim comparison Vs. JBL LE8TH using Akabak and sent me the response graph linked below. The dips are said to be artifacts of Akabak, but IME trying out high Qts drivers in backhorn or pipe designs is that they tend to sound boomy with midbass suckout. The not so encouraging part is that the designer says they LE8TH is quite bass heavy in that enclosure. Both the S-vox and JBL driver have very similar Q, although other parameters like Vas are far from each other: http://members.aol.com/IKSchiffer/jbl/bigbrother.html
*Akabak sim LE8 vs. RTF64 on K-lsot vented pipe:
http://pic4.picturetrail.com/VOL706/2663514/5325320/114959946.jpg
3.) Another that is of interest is the Singular enclosure (interesting backchamber with Helmholtz resonator). It’s said to work well with medium Qts drivers up to .6 or so. Will try this path too… http://www.bd-design.nl/contents/en-uk/d83.html
Of course there is the cool BIB design, with dims graciously provided by GM. However, width and depth is too large for my room I’m afraid.
Anything you may share would be greatly appreciated. Thanks for reading the longish post.
regards,
fred
I've been meaning to run a MathCad sim on those enclosures for a while. If you give me until tomorrow morning (well, it's technically morning already, but I need to sleep!) I'll run a few numbers.
A dirty great vented box like the old Tannoy enclosures might also be an interesting option, although it's not nominally that close to the TL type you want to try out.
A dirty great vented box like the old Tannoy enclosures might also be an interesting option, although it's not nominally that close to the TL type
Hi,
Look here http://www.audiofanatic.it/Diffusori/Tqwt215/TQWT215.html
Seems to be intresting design.
Good luck Martin
Look here http://www.audiofanatic.it/Diffusori/Tqwt215/TQWT215.html
Seems to be intresting design.
Good luck Martin
OK, here's what the driver looks in the Supravox TQWT.
To be honest, it's not too bad. This is a fairly quick model; I didn't refine to the 'nth' degree, but it's as close as should make no difference. I deliberately applied no stuffing to the model -a small quantity will take out the worst of the ripple.
It wouldn't be my choice for this driver, as IMO, it's not got enough volume -one of the reasons it cuts off a bit high for my taste, but I wouldn't mind sticking a smaller unit in it -in fact, I checked it with the FE168ESigma, to good effect. Someone (Can't remember who, off-hand) on the board is in fact doing just this.
To be honest, it's not too bad. This is a fairly quick model; I didn't refine to the 'nth' degree, but it's as close as should make no difference. I deliberately applied no stuffing to the model -a small quantity will take out the worst of the ripple.
It wouldn't be my choice for this driver, as IMO, it's not got enough volume -one of the reasons it cuts off a bit high for my taste, but I wouldn't mind sticking a smaller unit in it -in fact, I checked it with the FE168ESigma, to good effect. Someone (Can't remember who, off-hand) on the board is in fact doing just this.
Attachments
OK, here's a possiblility, if you've got the space. I came up with something similar a couple of weeks back for a friend with Coral Flat 10s, albeit rectangular, which wasn't ideal, but what he wanted. If you don't like the shape, you can make it whatever you want -just keep the CSA the same, or within a few percent of 236in^2. It's not small, but with driver's like these, you really need to have a sizable enclosure to get the best performance out of them.
I actually borrowed the layout and CSA from the original Tannoy Lancaster corner cabinet as I rather like it. It's stretched vertically to 42in tall (internal) though, and the big original rectangular vent is replaced by a single circular port, 4in diameter, 2in long, 4in up from the internal bottom. I'm lousy with CAD software (learning a couple of decent programs is on my to-do list), so I simply modified the original Lancaster drawing to reflect the changes. Sorry the internal length is so small -as I say above, it should be 42inches. 0.25lbs ft^3 of stuffing used in the top half of the enclosure.
I actually borrowed the layout and CSA from the original Tannoy Lancaster corner cabinet as I rather like it. It's stretched vertically to 42in tall (internal) though, and the big original rectangular vent is replaced by a single circular port, 4in diameter, 2in long, 4in up from the internal bottom. I'm lousy with CAD software (learning a couple of decent programs is on my to-do list), so I simply modified the original Lancaster drawing to reflect the changes. Sorry the internal length is so small -as I say above, it should be 42inches. 0.25lbs ft^3 of stuffing used in the top half of the enclosure.
Attachments
And here's the FR graph. This enclosure is on the border between being an MLTL and a BR I suppose -whatever you feel like calling it, it seems to work pretty well -roll-off is in lock-step with room gain, so it should be pretty flat to around 40Hz or so, and it'll still by belting out notes into the 20s, no problem. Smaller versions are possible of course, but if you've got the space, this'd be one of my top choices. Pretty nice efficiency too. Give me a shout if you want something smaller & I'll try to come up with something.
Regards
Scott
Regards
Scott
Attachments
Hi Scott,
I appreciate you doing a sim on the the Supra TQWT. I suspect the early LF rolloff is deliberate to avoid over-loading when placed near corners (?).
The Tannoy design looks sweet. The only problem I think is I've only got ~8.5' (width of the room) of space where the l/r speakers would be placed - too close to each other. Maybe a version that is narrower but taller? BTW, that's a textbook FR graph!
I have a heavily modifed SET amp that puts out around just 7W (but 'stiff' psu and driver stage). I'm not sure how amp damping factor would play a role in large BR 'hybrid' deisigns.
I would be out of town for 2 days. I'll have online access when I get back to ask a few more questions. Thanksabunch!
regards,
fred
I appreciate you doing a sim on the the Supra TQWT. I suspect the early LF rolloff is deliberate to avoid over-loading when placed near corners (?).
The Tannoy design looks sweet. The only problem I think is I've only got ~8.5' (width of the room) of space where the l/r speakers would be placed - too close to each other. Maybe a version that is narrower but taller? BTW, that's a textbook FR graph!
I have a heavily modifed SET amp that puts out around just 7W (but 'stiff' psu and driver stage). I'm not sure how amp damping factor would play a role in large BR 'hybrid' deisigns.
I would be out of town for 2 days. I'll have online access when I get back to ask a few more questions. Thanksabunch!
regards,
fred
Now that looks very impressive indeed. How did you model the Onken in MathCad? Or am I asking for trade secrets there? (my apologies if that's the case).
Bigger cabinets are better? Now, who was it who has taught me that principle over the course of a certain other thread... ;-) Cheers Greg. You've opened my eyes to quite a bit.
Regards
Scott
Bigger cabinets are better? Now, who was it who has taught me that principle over the course of a certain other thread... ;-) Cheers Greg. You've opened my eyes to quite a bit.
Regards
Scott
Greets!
You can't accurately model one in any program AFAIK, but assuming the specs are reasonably accurate it's close enough IMO. Anyway, nothing special, just run the numbers in an Onken calculator and use the PORTED WS. Since the vents are distributed along its height, just position the vent in the middle and calculate its radius based on their total area using whatever length the calculator says, then if you don't like it, change it to suit as I did with this one, hence the 'hybrid' moniker.
Here's the n = 6.34 Onken alignment I started with:
GM
You can't accurately model one in any program AFAIK, but assuming the specs are reasonably accurate it's close enough IMO. Anyway, nothing special, just run the numbers in an Onken calculator and use the PORTED WS. Since the vents are distributed along its height, just position the vent in the middle and calculate its radius based on their total area using whatever length the calculator says, then if you don't like it, change it to suit as I did with this one, hence the 'hybrid' moniker.
Here's the n = 6.34 Onken alignment I started with:
GM
Attachments
8" Vs. 6.5"
Okay, so there's no going around it if I want to get the most out of the RTF64 re: Needs cabs w/ large footprint. Maybe it would be do-able if the drivers can be mounted offset on the front baffle??? If the mounting is not centered on a wide baffle at least there will be some distance between the L/R drivers in my narrow room; less tendency to "shout". I'm just not sure how the offset will affect the response...
I'm more used to 8" drivers, but I won't discount 6.5" widerange/wideband drivers... Generally speaking, what are the pros and cons of 8" Vs. 6.5" if both are high performance with similar efficiency??? I know that larger drivers "move more air", but will it be significant if driver sizes are close? Plus let's say if the difference in Fs is very minimal between the drivers, ~4Hz higher for the 6.5"...
The real advantage with 6.5"rs (usually has much lower Vas) in this case, is the smaller footprint for enclosures. So a BIB would be an obvious candidate.
Thanks!
fred
Okay, so there's no going around it if I want to get the most out of the RTF64 re: Needs cabs w/ large footprint. Maybe it would be do-able if the drivers can be mounted offset on the front baffle??? If the mounting is not centered on a wide baffle at least there will be some distance between the L/R drivers in my narrow room; less tendency to "shout". I'm just not sure how the offset will affect the response...
I'm more used to 8" drivers, but I won't discount 6.5" widerange/wideband drivers... Generally speaking, what are the pros and cons of 8" Vs. 6.5" if both are high performance with similar efficiency??? I know that larger drivers "move more air", but will it be significant if driver sizes are close? Plus let's say if the difference in Fs is very minimal between the drivers, ~4Hz higher for the 6.5"...
The real advantage with 6.5"rs (usually has much lower Vas) in this case, is the smaller footprint for enclosures. So a BIB would be an obvious candidate.
Thanks!
fred
Re: 8" Vs. 6.5"
Greets!
You can offset it some, ~0.618:1 max, but if depth isn't a major issue, a MLTL is your best bet for making it narrower.
Well, all things being equal, it takes a little less than two 6.5" drivers to match an 8" in area and the higher the Fs, the higher Qts must be to tune it low, so you're going in the wrong direction for convering the LF BW. Really, the easiest thing to do is sim some to compare.
GM
Greets!
You can offset it some, ~0.618:1 max, but if depth isn't a major issue, a MLTL is your best bet for making it narrower.
Well, all things being equal, it takes a little less than two 6.5" drivers to match an 8" in area and the higher the Fs, the higher Qts must be to tune it low, so you're going in the wrong direction for convering the LF BW. Really, the easiest thing to do is sim some to compare.
GM
Hi GM,
Yes, enclosure depth is not a major issue. I could go with MLTL with the RTF64. Now the only prob is I don't have any engineering or higher math background, so doing MathCad sim/models etc. is out of my league. No way really to compare or come up with a design of my own. Any help on this dept would be greatly appreciated...
I linked a TL-like design for the RTF n my #1 post. It uses a Helmoltz resonator:
http://www.bd-design.nl/contents/en-uk/SINGULAR_ISOMETRIC.pdf
http://www.bd-design.nl/contents/en-uk/TOP_SECTION_SINGULAR_18mm.pdf
http://www.bd-design.nl/contents/en-uk/SIDE_SECTION_SINGULAR_18mm.pdf
What do you think?
I would be using low powered tube (se and pp) amplification, so I guess I wouldn't need any passive Eq network with these fairly linear drivers (at least on paper).
Thanks for the reply!
regards,
fred
Yes, enclosure depth is not a major issue. I could go with MLTL with the RTF64. Now the only prob is I don't have any engineering or higher math background, so doing MathCad sim/models etc. is out of my league.
No way really to compare or come up with a design of my own. Any help on this dept would be greatly appreciated... I linked a TL-like design for the RTF n my #1 post. It uses a Helmoltz resonator:
http://www.bd-design.nl/contents/en-uk/SINGULAR_ISOMETRIC.pdf
http://www.bd-design.nl/contents/en-uk/TOP_SECTION_SINGULAR_18mm.pdf
http://www.bd-design.nl/contents/en-uk/SIDE_SECTION_SINGULAR_18mm.pdf
What do you think?
I would be using low powered tube (se and pp) amplification, so I guess I wouldn't need any passive Eq network with these fairly linear drivers (at least on paper).
Thanks for the reply!
regards,
fred
Greets!
I've yet to read a review of this cab design by anyone whose opinion I trust and can't model it, so don't have a clue beyond the fact that ignoring the resonator, it will otherwise need considerable stuffing to be relatively smooth just like any end loaded pipe. Then again, with low power you may need to trade the smoothness of the MLTL for the rippling gain of an unstuffed pipe. I assume the resonator is designed to ~fill in the 3rd harmonic's dip, so it may be OK. Only one way to know for sure though!
With SE power, I would need to know the amp's output impedance or its DF, not its nominal tap rating(s).
GM
I've yet to read a review of this cab design by anyone whose opinion I trust and can't model it, so don't have a clue beyond the fact that ignoring the resonator, it will otherwise need considerable stuffing to be relatively smooth just like any end loaded pipe. Then again, with low power you may need to trade the smoothness of the MLTL for the rippling gain of an unstuffed pipe. I assume the resonator is designed to ~fill in the 3rd harmonic's dip, so it may be OK. Only one way to know for sure though!
With SE power, I would need to know the amp's output impedance or its DF, not its nominal tap rating(s).
GM
Hi GM,
The TL+resonator design needs heavy polyfill stuffing for the chamber part, where in the middle of that chamber there is a partition panel having 5 holes in it (purposely designed). The top part of the resonator hole is also covered with stuffing as illustrated in the .pdf top section plans. ~1.5" thick damping material on the bottom of the enclosure is also needed. And that's about it as far as stuffing goes, but hopefully it's a good compromise between smoothness and gain for my app... For a pipe like this I don't know if enclosure volume would still play a big role as I noticed that the RTF has a relatively higher Vas compared to other 8" offerings from Fostex, etc... Will try it first with cheap ply. There's only one person I read about who tried this enclosure with the RTF Bicone version, but there are no real impressions on how they sounded.
The zero nfb SE amp has an output impedance of 1.6 Ohms.
Thanks!
fred
The TL+resonator design needs heavy polyfill stuffing for the chamber part, where in the middle of that chamber there is a partition panel having 5 holes in it (purposely designed). The top part of the resonator hole is also covered with stuffing as illustrated in the .pdf top section plans. ~1.5" thick damping material on the bottom of the enclosure is also needed. And that's about it as far as stuffing goes, but hopefully it's a good compromise between smoothness and gain for my app... For a pipe like this I don't know if enclosure volume would still play a big role as I noticed that the RTF has a relatively higher Vas compared to other 8" offerings from Fostex, etc... Will try it first with cheap ply. There's only one person I read about who tried this enclosure with the RTF Bicone version, but there are no real impressions on how they sounded.
The zero nfb SE amp has an output impedance of 1.6 Ohms.
Thanks!
fred
Hi GM,
It's kit amp by sun audio (with lots of mods) from Japan. It's a basic SE amp really, although I guess most off the shelf SE amps from the from the west use lower primary impedance on the OPT for slightly higher power, hence ~2 to 4 Ohms DF on average.
I read an article from this webpage a few years ago on how to calc DF for tube amps (SE, PP, OTL).
http://www.transcendentsound.com/amplifier_output_impedance.htm
Basically just get the plate impedance of the output tube... Calculate the impedance ratio between pri & secondary of OPT (primary / secondary tap). Then the plate impedance of output tube is divided by the ratio of primary and secondary, then you get the DF value...
Perhaps it's too general a calc for the outputstage only, and not taking other factors into consideration???
I guess all is well If the pipe's Vb is "okay" when used with the RTF64 driver.
Thanks for the reply!
fred
It's kit amp by sun audio (with lots of mods) from Japan. It's a basic SE amp really, although I guess most off the shelf SE amps from the from the west use lower primary impedance on the OPT for slightly higher power, hence ~2 to 4 Ohms DF on average.
I read an article from this webpage a few years ago on how to calc DF for tube amps (SE, PP, OTL).
http://www.transcendentsound.com/amplifier_output_impedance.htm
Basically just get the plate impedance of the output tube... Calculate the impedance ratio between pri & secondary of OPT (primary / secondary tap). Then the plate impedance of output tube is divided by the ratio of primary and secondary, then you get the DF value...
Perhaps it's too general a calc for the outputstage only, and not taking other factors into consideration???
I guess all is well If the pipe's Vb is "okay" when used with the RTF64 driver.
Thanks for the reply!
fred
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