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Author Topic: SPL TD1 Recondition & Improvements  (Read 5926 times)

Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #10 on: August 10, 2018, 11:45:38 pm »

I haven't gotten to each component but DATS just came in today and I wanted to give it a go, pretty schweet. I can see why Langston talks fondly of it.

Yellow in first pic is before I twisted the speakon about 15 or so times to help clear the corrosion.

Seems part of my restoration process might be to check for more corrosion (previously I tried to clean up the xover's).
« Last Edit: August 10, 2018, 11:50:27 pm by Nathan Riddle »
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #11 on: August 10, 2018, 11:56:47 pm »

You REALLY need to be careful about just "throwing any 'ol" driver in the cabinet.

The position of the HF in relation to the mids (phase response/timing) is critical.

A different driver may have a slightly different path length, therefore throwing the phase response where they need to meet up off.

Amplitude response is often easier to deal with than phase response.

Yes I have tried some different drivers and there are noticeable differences when you look at the whole cabinet response.

It is the SUM of the parts that makes it what it is, not just the individual parts, no matter what quality they may be.

I definitely don't plan on doing that. The SAC thread referenced speaks to that being a horribly bad idea.

I think mainly my thought on replacing drivers would be the "TD-2" xover that calls for the BMS 4550 (hoping I can swap the 4552nd=neo). The extended HF & LF (and hopefully distortion) would increase the fidelity.

I have gobs of amp power with the iTech8k so I'd think the extra 'padding' of the TD-2 xover would be okay. Though the impedance curves seem to indicate why the 4k range is down (at least that's why my inexperienced mind says) [what amp can produce power at 69 ohms @ 3.91kHz].
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #12 on: August 10, 2018, 11:59:41 pm »

Hi Nathan, glad to hear the 3tx arrived.....enjoy :)

FWIW, here's how I'd try to meet your TD-1 goals.....
a. measure each driver raw, individually....transfer and impedance...looking for general health and consistency
b. measure each driver section raw....ie both 12"s running together, all four 5"s together, (CD already done )...transfer and impedance
c. measure each driver section individually with passive crossover in place....transfer
d. measure entire box with passive crossover in place...transfer and impedance

Assuming all drivers are in good condition, these steps have let me see how the drivers are being used.
A good idea of the passive crossover topology should be evident.  If any confusion remains, I'd run transfers on the electrical crossover outputs.

Now I should have enough info to decide what i want to do... fiddle with passive, go active, bi/tri amp, etc etc...maybe even replace drivers

Since I've made active multi-way processing one of my hobbies, I'd do it just to see if I could better the passive....and learn some more.
Your Ashly ne8800 is a great platform to try from.   
1.I'd first eq each driver section individually for the smoothest response possible.  Be willing to use out of band eq to flatten response tails.
2.Then I'd try to replicate the passive crossovers, paying special attention to any asymmetries if they're present.
3.Tie it all together with polarities, levels, and timings.

That was all using IIR.  If you want to take it up a substantial level, I'd use the FIR capability in the ne8800.
1. either keep the IIR eqs for each section as they are, or embed them into the FIR file
2. choose crossover points based on measured passive points, and substitute linear-phase complimentary crossovers, probably LR24s
3. same step as above, but much much easier to tie flat phase slopes together  ;)

The ashly has up to 384 FIR taps, that should work handily for the mid to CD crossover.
It may or may not work for the low to mid crossover, if the crossover freq is too low. If you find you can't hold a 24dB slope there, you need more taps.
If your ashly has the AES input/output option, I highly recommend a miniDSP OpenDRC-DI for more taps.
$325, AES in and out, 2x6144 taps. An incredible learning tool.

Donateware rePhase can build fir files for both the ashly and miniDSP.  FirDesigner is excellent, but costs.
rePhase is kinda cool to start out with, because it's all manual and gets you to think through whats going on..another incredible learning tool.

Best of Luck !
Mark

Thanks, Mark!

This is a great write-up for someone such as myself getting their feet wet with speaker building!

I didn't have time to take readings of the drivers yet, but I can't wait!

One question...
Should I remove each driver from the horn while doing the test or can I leave them in (shorting the others during the test)?
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John Halliburton

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Re: SPL TD1 Recondition & Improvements
« Reply #13 on: August 11, 2018, 08:53:04 am »

"One question...
Should I remove each driver from the horn while doing the test or can I leave them in (shorting the others during the test)?"


I'd remove them and test them in the same bench position.  I suspect too much interaction with other drivers and particular position in the horn will give different results measuring an individual driver.


I suspect you'll find the midranges will be the drivers that show the most imppact from life in pro audio.  They may work, but I've found that they get a bit worn down over time.  Cheap to replace though.

And yes, the TD-1 does gain quite a bit of output in the lower response when a second(or more) is added.  That was part of the design.

Best regards,

John
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josh allman

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Re: SPL TD1 Recondition & Improvements
« Reply #14 on: August 11, 2018, 10:05:50 am »

I do have smaart, an itech 8k, and a couple TD-1s around today, if you would like a reference. Id have to do the test in my garage so not sure if reflections will make it worthless, but Id be willing to try it out.

1m distance, how loud?


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Mark Wilkinson

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Re: SPL TD1 Recondition & Improvements
« Reply #15 on: August 11, 2018, 10:40:04 am »


One question...
Should I remove each driver from the horn while doing the test or can I leave them in (shorting the others during the test)?

Like John says .....(who like Art, has considerable more speaker building expertise than me...(my only budding expertise is multi-way FIR tuning)).

I figure the individual driver testing is more about health and consistency, than in-box response. 
To this end, you might want to use DATS to also measure the T/S parameters.....

I'd be particularly interested if you can detect any cone sag differences between the drivers. 
I've been wondering how the more horizontally mounted drivers in synergy's age, ever since the topic of cone sag came up on one of my sub projects. Please pass on if you see anything there...

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Mark Wilkinson

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Re: SPL TD1 Recondition & Improvements
« Reply #16 on: August 11, 2018, 10:52:44 am »

You REALLY need to be careful about just "throwing any 'ol" driver in the cabinet.

The position of the HF in relation to the mids (phase response/timing) is critical.

A different driver may have a slightly different path length, therefore throwing the phase response where they need to meet up off.

Amplitude response is often easier to deal with than phase response.

Yes I have tried some different drivers and there are noticeable differences when you look at the whole cabinet response.

It is the SUM of the parts that makes it what it is, not just the individual parts, no matter what quality they may be.

Hi Ivan, I'm guessing you swapped drivers with the same passive crossover in place?

If a fellow has the ability to actively dial in different drivers, where they sum correctly mag and phase in keeping with the acoustic design, do you see any red flags?     thx

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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #17 on: August 11, 2018, 10:57:35 am »

I'd remove them and test them in the same bench position.  I suspect too much interaction with other drivers and particular position in the horn will give different results measuring an individual driver.

I suspect you'll find the midranges will be the drivers that show the most impact from life in pro audio.  They may work, but I've found that they get a bit worn down over time.  Cheap to replace though.

And yes, the TD-1 does gain quite a bit of output in the lower response when a second(or more) is added.  That was part of the design.

Thanks, John, I'll do that.

One TD1 already has 4 new mids from DSL. The other one I replaced two broken mids when I first got them.

Later today I'm going to my friend's field and we're going to test each speaker (3TX, SRX, TD1, 153) at a distance seeing what SPL we can get, what they sound like, etc.

I plan on getting some off-axis readings for comparisons. Hopefully 0,30,60

I do have smaart, an itech 8k, and a couple TD-1s around today, if you would like a reference. I’d have to do the test in my garage so not sure if reflections will make it worthless, but I’d be willing to try it out.

1m distance, how loud?

Having a reference sounds lovely.

No worries, I believe my setup comes with a plethora of reflections.

Herm, never measured that. One sec... Looks like 83dBC/fast, 82.7dBC/slow (just a guess at how loud I made it before).

Yellow:
SPL: 82.7dBC/Slow
Dist: 28"
HP: 65Hz, LR24
EQ1: 75Hz, +3dB, 1.5Q
EQ2: 1.95kHz, -2.5dB Q10
EQ3: 3kHz, 2.5dB, 4.5Q
EQ4: 7.57kHz, -4.5, 5Q
EQ5: 10.25kHz, -4.5dB, 4.5Q

Blue is old trace for reference.
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #18 on: August 11, 2018, 10:58:57 am »

Like John says .....(who like Art, has considerable more speaker building expertise than me...(my only budding expertise is multi-way FIR tuning)).

I figure the individual driver testing is more about health and consistency than in-box response. 
To this end, you might want to use DATS to also measure the T/S parameters.....

I'd be particularly interested if you can detect any cone sag differences between the drivers. 
I've been wondering how the more horizontally mounted drivers in synergy's age, ever since the topic of cone sag came up on one of my sub projects. Please pass on if you see anything there...

Can you explain cone sag and how to test for it?
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Mark Wilkinson

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Re: SPL TD1 Recondition & Improvements
« Reply #19 on: August 11, 2018, 01:00:39 pm »

Can you explain cone sag and how to test for it?

Hi Nathan, it may only be relevant to larger drivers. 
It's simply the weight of the voice coil slowly settling the cone/surround out of center position.
The more horizontal the driver mounting, obviously the more the potential for settling away from center.

I put a straightedge across the mounting surface and measure down to the center of the dust cover.
So it helps to know how 'new' measures, but if you don't have that reference, just compare the different drivers on the bench when all pointing up.  If there is any setting, I'd suspect the difference between the up-mounted and down-mounted drivers will show it.
Just curious I am, don't mean to be chasing ghosts....   If you do measure a difference, I'd take the time to check T/S just for learning...
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