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Building a 3-way TL speaker

Wharfedale Linton Heritage Speakers

Hari Iyer

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I now have a opportunity to build a 3 way TL speaker for a FM who has a SS Krell ksa100mk2 for bass and TAD 1000 tube mono blocks for mids and highs. Sources are CD-esoteric K-01, DAC - AMR dp-777 and Roon end point for digital streaming - Metrum ambre. Pre-amp is T+A P1260R. Currently they are hooked up with PMC floor standers with Krell amplifier in full range mode. He is in the lookout for more organic and holographic 3D sound stage and flexibility to mix and match various gears with future possibility of going active crossovers. The reason for opting to DIY was to get the best combination of lows, mids and highs with realism which as per him are missing in commercial products at a budget.

With this requirement in mind, i went hunting for various drivers past one+ month and finally narrowed down with Seas Prestige woofers (paper cone), SB Acoustics Satori MR (paper cone) and Beyma AMT (with horns).

The said woofer was selected as i was looking for a more high compliance/ low mass driver that can play the harmonics of the fundamental note quite well without getting compressed. Most high moving mass drivers are low compliance type and they can render only the fundamental bass right and compresses the overtones. This removes all realism from music. Needless to say this driver will be in a exo-linear TL with critical damping and this woofer prefers a lossy line and not a complete sealed enclosure. The Satori will be in a sealed enclosure to benefit of its high compliance (2.35mm/Newton) and i will be using atleast 70% stuffing to give it a high stiffness box for it to perform flawlessly. The tweeters is a AMT type attached to a horn and will be able to perform well at low distortion levels even at lower crossover points.

I have yet to finalize the box sketch as they are still in simulation mode past one month. I have already ordered the drivers and they should be delivered by end of September. This time the carpenter showed some pity for me and shall deliver the box before that. I had also simulated the crossover with publish parameters and they did turn out quite well. But again we will need to build the crossover with measured values and not published ones. Hoping this project to get over by end of this year if all turns out well.

Keep checking this post for updates. Thanks for looking.

Initial plan is to go for a first order crossover for everything. Low, mids and highs. This is one of the major reason to select these drivers. All drivers have a breakup mode 3 octaves above the crossover frequency which currently would be 300Hz and 3KHz. For a first order filters there is a significant overlap of the frequency beyond the crossover points. Hence to get a -6dB response at the crossover point the design frequency need to be either reciprocal of sqrt(2) or multiplied by sqrt(2) to arrive at the design frequency. This avoids the classic hump at the Crossover point and gives a flat response at the passband while still preserving the filter phase at 90deg and eventually cancel out. This gives a response -12 dB down at the next octave. This speaker will be time aligned for the lows, mods and highs so that they integrate well in the time domain. This is the tough part to figure out and design to get the acoustic centers of the drivers integrated so they sound as one. More important for mid to high than the low to mid frequency. Planning to keep the crossover as simple and minimiliast as possible to preserve the SPL of the drivers. Importance will be on accuracy more than frills.
 
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sanj

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Aug 26, 2010
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Gurgaon.
Great..I am also subscribed,kindly let us know expected cost of the end product , i will send you msg for other query.
 

tcpip

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Mar 1, 2010
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Is this Seas woofer the same one which Linkwitz uses for his LX521? I believe it has good low distortion performance at high excursion, which is a rare quality.
 
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Hari Iyer

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Is this Seas woofer the same one which Linkwitz uses for his LX521? I believe it has good low distortion performance at high excursion, which is a rare quality.
tcpip, i believe the LX521 used the SEAS L26RO4Y woofer which is different from the A26RE4 woofer. The A26RE4 is a classic vintage woofer from the mid-70 which was at that time A25 and was extensively used in the Dynaco A-25 classic speaker from the 70s. This speaker requires a lossy line and works well with this kind of loading. Putting them in a TL with some over damping will be suitable imo. Check out the Dynaco A-25 link for more details https://www.stereophile.com/content/dynaco-25-loudspeaker
 

Hari Iyer

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Joined
Feb 8, 2010
Messages
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113
Location
Mumbai
Received the box yesterday evening and started working with my stock ribbon tweeters (the Beyma's are two weeks away from delivery), but could not wait to lay my hands with whatever is available.

IMG-20190929-WA0002.jpg

Measured the speakers today and found the midrange and woofer step not smoothly blending with a delay of around 0.075ms or 25.8mm. This i later calculated was because the box is not time-aligned for the woofer and midrange and the driver center causes, the midrange to be little more forward than the woofer by 0.075msec. I am not sure if my ears could identify that, but the REW could.

Step response.jpg

Now i will need to try and add a equal amount of delay with passive components (if at all possible) and measure again if they blend smoothly. The speakers are still in design mode.

This is the simulated step response,

step.png

Stay tuned for further updates.
 

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Hari Iyer

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Feb 8, 2010
Messages
2,957
Points
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Location
Mumbai
After 3 months of patiently waiting for the Beyma tweeters, i understand that these tweeters have vanished from all stocks. The Chennai beyma dealer is indifferent and does not respond to any messages. His silence speaks louder than words and he has ditched me on this. Thankfully i was able to get full refund for the advance paid and i am not hoping him to deliver the tweeters any soon. God be with you, if you happen to deal with such dealers. Anyway thats a different story altogether.

Now, i have to redesign the 3 way speaker and have some ideas. 4 way come to my mind as i could not find any single tweeter (other than the Beymas) that can handle from 2kHz to 20kHz. I have narrowed upon some compression drivers + Ribbon tweeters combo to take this task in a 4 way setup. So the frequency division will be somewhat as below,

20Hz - 300Hz - Seas woofer
300Hz - 2KHz - Satori MR
2KHz - 8KHz - compression drivers (yet to decide between Paudio and Selenium-JBL)
8KHz - 20KHz - Fountek ribbon tweeters.

Interestingly Prem's JBL 4343 was an inspiration of taking this idea and the vanishing of the Beyma's allowed me to think like wise. Yet everything is still under design stage and i have not ordered anything. I have already discussed this with the FM for whom this is been built and he is quite ok with this approach.

Thanks for looking.
 
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