Yes. That’s basically how you can scale a TL or horn. Double the volume to match the double Vas. The bass extension is the same, as the length is the same. The sensitivity is +6dB if wired parallel and the same (0dB) if in series. But going to bipole eliminates baffle step loss so net gain circa 5dB to 6dB. Wire two 4ohm drivers in series and you now have 8ohm speakers which lets more amps drive it - like many Class A amps are designed for 8ohms minimum.
Picture running a string of woofers from the tweeter to the floor, à la line array. The mechanism of action is different for different kinds of modes so the details of how many woofers and how to space them can vary, if you care to work out the differences, but some take a standard approach with good results. The Elsinores are an example of this. It also reduces box modes for what it's worth.
Attachments
I had a few minutes to play around in hornresp.
2 drivers in about 36.6 litres, F3 is about 32hz
I will draw something up later.
I can't seem to figure how to add jpg's here (???)
But the line is 163cm long
beginning area is 426cm2
termination area is 65cm2
centre of the 2 drivers is offset 25.2cm from the beginning of the line.
2 drivers in about 36.6 litres, F3 is about 32hz
I will draw something up later.
I can't seem to figure how to add jpg's here (???)
But the line is 163cm long
beginning area is 426cm2
termination area is 65cm2
centre of the 2 drivers is offset 25.2cm from the beginning of the line.
Lets call this FiTL
In post 392 hallcon83 asked “I have a question , I have 4 Purify Drivers and am not sure of the best way to use them - does anyone have suggestions for a design..... ? ..... Or another way to approach this, if you had 4 drivers , how would you use them, what would you build??”
Xrk971 responded “Wire two in series as bipole (Push push front and back Magnets supported with common brace) in tall floor stander TL.
- 8 ohms impedance at 88dB
- No baffle step loss - true 88dB sensitivity at 50Hz
- Omni pattern
- Vibration cancellation”
Then AllenB opined “Stack them and attempt to gain directivity to manage vertical reflections.”
My reaction to both suggestions was YES, that’s a good idea. Actually which is the best is in my experience related to how the room they will be used in is setup. If I can site the speaker well away from the back wall sign me up for the push/push bipole. If the situation demands closer back wall placement then drivers need to be on front panel.
Then in post 404 ontariomaximus posted some rough starting TL parameters for such a TL featuring two PTT6.5W04 woofers per speaker. This all fits in with a short tower design I have been toying with featuring a tweeter on top inspired by the Kaiser Acoustics Kawero Classic.
The little tweeter box on top allows playing with time alignment and different tweeters (I’m a bit of a tweeter slut always switching). Of course the other oddness in the attached sketch is surely three not two woofers. The idea here is this TL could be built with its pair of woofers in locations A & B for the bipole or A & C for a forward fire configuration. Lengths are more or less along ontariomaximus’ with the fat grey lines measuring the center length. Angles are all 45 degrees because those are fairly easy to achieve on table saws, router tables, and CNC. Did not bother drawing those angles on panel ends for sealing at this very preliminary stage. Some will object the turns are too sharp. My reply is the bass I want out the line end port will have no problem making that turn and I plan for the higher frequency content to fail to turn instead bouncing around getting absorbed by the acoustic filling.
Comments and discussion welcomed. I am a complete neophyte to transmission lines and readily admit this is all highly speculative and preliminary as I climb that learning curve. Moving the second woofer between B & C locations effect on the line tuning is the first thing I wonder about. Is this ‘close enough in practice’ or would the interior need to be tweaked to more closely hit the 25 cm beginning of line to drivers’ center spec?
In post 392 hallcon83 asked “I have a question , I have 4 Purify Drivers and am not sure of the best way to use them - does anyone have suggestions for a design..... ? ..... Or another way to approach this, if you had 4 drivers , how would you use them, what would you build??”
Xrk971 responded “Wire two in series as bipole (Push push front and back Magnets supported with common brace) in tall floor stander TL.
- 8 ohms impedance at 88dB
- No baffle step loss - true 88dB sensitivity at 50Hz
- Omni pattern
- Vibration cancellation”
Then AllenB opined “Stack them and attempt to gain directivity to manage vertical reflections.”
My reaction to both suggestions was YES, that’s a good idea. Actually which is the best is in my experience related to how the room they will be used in is setup. If I can site the speaker well away from the back wall sign me up for the push/push bipole. If the situation demands closer back wall placement then drivers need to be on front panel.
Then in post 404 ontariomaximus posted some rough starting TL parameters for such a TL featuring two PTT6.5W04 woofers per speaker. This all fits in with a short tower design I have been toying with featuring a tweeter on top inspired by the Kaiser Acoustics Kawero Classic.
The little tweeter box on top allows playing with time alignment and different tweeters (I’m a bit of a tweeter slut always switching). Of course the other oddness in the attached sketch is surely three not two woofers. The idea here is this TL could be built with its pair of woofers in locations A & B for the bipole or A & C for a forward fire configuration. Lengths are more or less along ontariomaximus’ with the fat grey lines measuring the center length. Angles are all 45 degrees because those are fairly easy to achieve on table saws, router tables, and CNC. Did not bother drawing those angles on panel ends for sealing at this very preliminary stage. Some will object the turns are too sharp. My reply is the bass I want out the line end port will have no problem making that turn and I plan for the higher frequency content to fail to turn instead bouncing around getting absorbed by the acoustic filling.
Comments and discussion welcomed. I am a complete neophyte to transmission lines and readily admit this is all highly speculative and preliminary as I climb that learning curve. Moving the second woofer between B & C locations effect on the line tuning is the first thing I wonder about. Is this ‘close enough in practice’ or would the interior need to be tweaked to more closely hit the 25 cm beginning of line to drivers’ center spec?
Attachments
IF doing a single pair of loudspeakers..
I'd do a smaller (scaled-down) version of the Sonus Faber Stradavari: using the Purify drivers as mid-bass drivers that scale well into the midrange (viable with the wider baffle).
Midrange: Neo 10 open-back (again, viable with the wider baffle).
Tweeter: Viawave SRT-7.
Attachments
Last edited:
Hi Norman,
That’s sort of what I had in mind too but had not considered the dual drivers on the front option. I would try to keep rectilinear 90deg bends as it’s easier to build. But the slanted passages may reduce standing wave cancellation. Good idea of having an external tweeter box that slides back and forth for time alignment - important for a tweeter slut (albeit, high priced tweeters)
haha
That’s sort of what I had in mind too but had not considered the dual drivers on the front option. I would try to keep rectilinear 90deg bends as it’s easier to build. But the slanted passages may reduce standing wave cancellation. Good idea of having an external tweeter box that slides back and forth for time alignment - important for a tweeter slut (albeit, high priced tweeters)
haha
Last edited:
Hi scott I had thought of the Neo 10, but they are out of stock and 370.00 each... so then I thought that maybe a pair of Neo9's and a couple of Neo3's might work well. But then Neo 9's or 10's aren't really necessary - Norman and others have said the midrange of the Purifi is amazing , and can cross up somewhere around 2,500 - 3,000 Hz so I was thinking maybe just a couple of the GR Research Neo3's for High SPL's if needed.
Hi Norman and that's a good idea of having the tweeter module separate to allow different tweeters to be tried, I always liked the way the Kawero looked too. When you or Xrk were modeling your TL's did you get as far as finding how low the dual woofers would go?
I was also considering MTM Ideas too.....
I found another interesting tweeter - there is a company out there that has a new version of an older Ribbon tweeter design, NewForm Research - Their Oval Ribbon driver's can be crossed over around 1,000 - 2,000 Hz, It's also very rugged and capable of Hi output , and is a very easy load to drive - "The Oval Ribbon is designed for use in a Coaxial Ribbon Line Source system but will work exceptionally well in any conventional Ribbon application" and comes in 15, 30 and 45 inch sizes.
Hi Norman and that's a good idea of having the tweeter module separate to allow different tweeters to be tried, I always liked the way the Kawero looked too. When you or Xrk were modeling your TL's did you get as far as finding how low the dual woofers would go?
I was also considering MTM Ideas too.....
I found another interesting tweeter - there is a company out there that has a new version of an older Ribbon tweeter design, NewForm Research - Their Oval Ribbon driver's can be crossed over around 1,000 - 2,000 Hz, It's also very rugged and capable of Hi output , and is a very easy load to drive - "The Oval Ribbon is designed for use in a Coaxial Ribbon Line Source system but will work exceptionally well in any conventional Ribbon application" and comes in 15, 30 and 45 inch sizes.
Attachments
I have a standmount TL that would be a very large bookshelf speaker.
https://www.diyaudio.com/forums/mul...ng-ptt6-5-rs28f-waveguide-28.html#post6323964
It sounds amazing though as if it were a much bigger speaker. The waveguide tweeter is superb.
https://www.diyaudio.com/forums/mul...ng-ptt6-5-rs28f-waveguide-28.html#post6323964
It sounds amazing though as if it were a much bigger speaker. The waveguide tweeter is superb.
Like most 6" woofers, the Purify's start loosing pressure off-axis at about 1.5-1.6 kHz.
https://hificompass.com/sites/defau...oaxis/ptt6.5w04-01a_offaxis.png?itok=9cVh2uti
IF you use a large enough waveguide for your tweeter then polar (off-axis) matching between your tweeter and your woofer should be OK, but if you don't then it's going to require something lower in freq. for your cross-point.
Also, as good as the Purify might be - it's not going to be as good as the Neo 10 (at least subjectivly), particularly not if the Neo 10 is open-back and has some of the dipolar out-of-phase pressure from the rear of the cabinet. Note: the Neo 10 will be back in stock in almost 1 month. Objectively it should be better (w/ lower pressure higher harmonics) because of the limited bandwidth with a proper crosssover.
That's not to say that the Neo 3 wouldn't be a good match IF it had the right waveguide and IF it had the right rear-chamber.
Also, my comment was in context with *2* Purify drivers.. (per cabinet.)
You really should NOT be running both of those drivers up to about 2 kHz. You could however do so with a bipole design as mentioned where the upper-freq. pressure loss is lower than the front. It will however create some nasty diffractive combing at the edges though (..unless the cabinet has enough absorptive material on the its edges - which is tough to do). ..and even then it still is likely to require it's own filter, speaking of which:
You could of course also make it a 2.5 way speaker and just use one of the two to 2 kHz and the other to fill-in the baffle-step loss.
Last edited:
I’m the person who commissioned this design from Joseph Crowe. Looking forward to the finished product.
- Hi Studley , welcome to the thread, I checked out the information on Joseph's design and after watching the video I was really impressed, Very well built! - I learned a few new things. It looks like a great design, wish I could afford it - I like the waveguide design a lot.
-- Hi Xrk, and Norman , I ran across an interesting thread on TL speaker design , Have either of you read through this thread ??? -- What did you think ?
An Improved Transmission Line Alignment.
-- Hi Xrk, and Norman , I ran across an interesting thread on TL speaker design , Have either of you read through this thread ??? -- What did you think ?
An Improved Transmission Line Alignment.
Hi Hallcon,
Yes, I have seen that thread - I was already designing and building TLs using those concepts for years already - the concepts of tapered TL, offset of the driver along the line, stuffing, etc. they are all employed in my PTT6.5 TL. I do feel that a tapered TL with stuffing properly applied is the best sounding bass possible. It has a shallow bass roll off and the group delay is minimized while the reduced driver stroke and better cone control reduces distortion for a clearer mid bass. You hear textured bass rather than one note bass. There is content within the bass note. Reflex and PR alignments don’t do this well. Front loaded horn bass does this perhaps the best. But they are huge.
Yes, I have seen that thread - I was already designing and building TLs using those concepts for years already - the concepts of tapered TL, offset of the driver along the line, stuffing, etc. they are all employed in my PTT6.5 TL. I do feel that a tapered TL with stuffing properly applied is the best sounding bass possible. It has a shallow bass roll off and the group delay is minimized while the reduced driver stroke and better cone control reduces distortion for a clearer mid bass. You hear textured bass rather than one note bass. There is content within the bass note. Reflex and PR alignments don’t do this well. Front loaded horn bass does this perhaps the best. But they are huge.
xrk971: always interesting to follow your builds. Now that you have played some time with the purify driver. How would you compare it to the Dayton next to it. On some reviews, it seems the purify can do things, that no other bass driver can, for its size. But does it actually better the Dayton ?
Selah Audio Purezza tested here Selah Audio Purezza Bookshelf Speaker Review
"I have yet to hear a speaker of this size with this level of neutrality. The midrange is so distortion-free that it’s like listening to your music collection with a new set of ears/memory. I have to think that this is pushing the envelope, if not exceeding it, for performance in this size class and cost.", says Erin
"I have yet to hear a speaker of this size with this level of neutrality. The midrange is so distortion-free that it’s like listening to your music collection with a new set of ears/memory. I have to think that this is pushing the envelope, if not exceeding it, for performance in this size class and cost.", says Erin
Last edited:
Column Line Array using Purifi Drivers
I am planning to make a column line array using a number of the Purifi PTT6.5W04 drivers + Pro-Ribbons.
Its for a mini bar/ club 13x12m with a high ceiling 6m and very hard untreated surfaces. Its a bit like a modern church/ chapel in its design and acoustic qualities.
Sound quality is paramount within the limitation of the structure not being acoustically treated - it won't be played loud but will still need some level of SPL headroom.
Any advice on speaker spacing, box design/ dimensions, ribbon placement, number of drivers required, etc etc?
I am planning to make a column line array using a number of the Purifi PTT6.5W04 drivers + Pro-Ribbons.
Its for a mini bar/ club 13x12m with a high ceiling 6m and very hard untreated surfaces. Its a bit like a modern church/ chapel in its design and acoustic qualities.
Sound quality is paramount within the limitation of the structure not being acoustically treated - it won't be played loud but will still need some level of SPL headroom.
Any advice on speaker spacing, box design/ dimensions, ribbon placement, number of drivers required, etc etc?