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Author Topic: SPL TD1 Recondition & Improvements  (Read 5289 times)

Nathan Riddle

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SPL TD1 Recondition & Improvements
« on: August 09, 2018, 12:33:47 pm »

I am currently working on restoring/improving my TD1's. I wanted a place to document my journey & get help as needed.

Backstory:
I purchased these back in 2016 because they were the 'almost sh46'. Scattered reports of the TD1 sounding better, but not as loud were also impressive especially at the price I got them for. I quickly found out I was no match for their weight & complexity so I put them to the side after some initial testing/restoration.

I have a renewed interested in finishing what I started and maybe improving the performance by moving to the TD-2 xover, replacing drivers, and/or bi-amp/tri-amp, adding HF protection, etc.

Goals:
1) Restore the TD1 to full working order so I can use on 'big gigs' or where pattern control is necessary.
2a) Implement improvements: louder, lighter, sentinel protection [at least hit its original goal of 137dB & perform well in a live/playback/gig situation]
2b) Add handles
3) Learn more about the TD1 & Synergy horn concept
4) Learn more about measurements in speaker design
5) Learn more about speaker design (parallel)
6) Have fun

Current plan:
1) Test each driver (impedance & FR & Phase) in-horn, drivers shorted, direct to amp to interface
2) Upload traces & get feedback (for instance: weird 4kHz issue)
3) Test in field and compare to SRX835p & JTR 3TX
4) Obtain off axis traces
5) Upload traces & get feedback
6) Implement some 'improvements' limiting on HF, neo HF (4552nd), New 12's, TD-2 xover (or improve current xover). [feedback if this is a good idea or not is welcome/invited]

Tools:
-DATS V2 (for impedance testing)
-LinearX VI Box (for impedance testing w/ amp) [REW or ARTA as software]
-SMAART (Focusrite or UMC404HD as interface) ( ECM8000 and EMM-6)
-iTech8000 (EQ, peak, program, & thermal limiter)
-Ashly ne8800 (FIR/EQ)

Resources:
http://forums.prosoundweb.com/index.php/topic,76042.0.html
http://forums.prosoundweb.com/index.php?topic=71622.0
http://forums.prosoundweb.com/index.php?topic=71214.0
https://www.prosoundtraining.com/forum/view_thread.php?thread_id=171120&page=1&sort_order=asc
https://www.prosoundnetwork.com/archives/servodrive-sound-physics-labs-td-1-speaker
http://forums.prosoundweb.com/index.php?topic=109187.30

Specs: https://web.archive.org/web/20081204100049/http://www.soundphysics.com/SPL-td1.html
Quote
Frequency Response: 65 Hz-20kHz Ī3dB (2 or more boxes)
Sensitivity: 103 dB @ 2.8v/1m

Power Handling: 600 Watts Continuous
Peak SPL: 137dB @ 800 Watts Pink Noise (6dB Crest Factor)
Nominal Impedance: 8 Ohms Average
Coverage Pattern: 60V x 40H

Transducers LF: 2 x 12"
Transducers MF: 4 x 5"
Transducer HF: 1 x 1"

Weight: 130 lbs.
Dimensions: 29" H x 23"D x 19"W
Construction: 13 Ply Baltic Birch
Finish: Black Catalyzed Texture Coat, White Catalyzed Texture Coat, Line ĖX Exterior Coating

Box Angle: 30 Degree Trapezoid
Connectors: 2 x NL4 (Passive)
2 x NL4 & 2 x NL8 w/pin swap switch (Active)

Continuation of this thread:
http://forums.prosoundweb.com/index.php/topic,159763.0.html

Inspired by this post/thread:
http://forums.prosoundweb.com/index.php/topic,167986.msg1550780.html#msg1550780

---

What Drew and I have talked about so far (edited minimally to protect the innocent):

What started me down the path of no return:
My suggestion is to change out or modify the crossovers when you get time and money.  The original design did not really do the rest of the box justice.  Some years ago Tom worked up a new crossover design for these that was tentatively called the TD-2.  The idea was to make the crossovers as an upgrade option for all the installed TD-1 boxes that customers had.  I'm not sure if that idea went forward but the crossover was a major improvement in terms of frequency response, phase response and overall sound quality. Tom said at the time that it was not quite as good but in the ball park of the SH50.  Of course, that improvement came with a few costs.  The recipe called for the BMS4550 (which was the darling of the Danley line at the time) compression driver and there were a lot more crossover components.  This included several expensive capacitors and inductors.  I don't think any of the original components could be re-used.  I made one crossover for one of my boxes to try it out and even experimented with the original B&C driver vs the 4550.  (The original driver wasn't too far off from the 4550.  I think you could get by with a little EQ.) . The other drawback for me was the loss in sensitivity.  I always felt that the original crossover was perhaps padded a little too much but in order to really get the response under control, Tom had to pad it down even more. 

Given the cost and the loss of dbs ( vs amplifier ) I decided to work on rolling my own crossover design that I dubbed the "TD-3".  My design idea was to simply get the drivers as loud, protected and working in "synergy" as possible without much regard for frequency or phase response - I would "correct" those as much as possible with DSP.  I ended up with something that reused quite a few components from the original crossover and was much louder while driven from a channel of a QSC PL236 amplifier.  After some processing, they've never sounded better.  I don't do a whole lot of music shows any more but I never cease to be impressed at how these sound when I shoot them across a ballroom and send them a podium mic.  The 'clarity' or 'throw' or whatever you want to call it from that largish horn really puts the sound where I want it. 

Some folks used to bi-amp or tri-amp these speakers.  I was never terribly interested in that given the cost and cabling complications.  But there are certainly more possibilities if you go that route.

Hi Drew,

I have a couple of TD-1's that sit unused because I couldn't get them loud enough originally with my RMX2450.
I'm thinking it might be the xover.

I saw your post about them and I wanted to see about the improved v2 xover or the v3 xover you created.

Hi Nathan,

I understand the issue well.  They tend to be bright without a lot of "rock n roll" midrange cut. They're capable of it but it takes some signal level. Hereís a bunch of words to explain my journey a bit. 

For the first few years I actually used Carver PM1.5 amps, bridged, per box.  I wired the woofers in series instead of parallel and bypassed the 1 ohm resistor.  This worked pretty well with a lot of dynamic power.  But then some kids broke into my truck and stole some gear and since I wasnít excited about buying more really old amps, I ended up buying more QSC PL236 amps.  Around that same time I did a noise evaluation gig where I had to pump pink noise as loud as I could into a neighborhood and some acousticians went out and took measurements.  I tried bridging various QSC amps (3002, PL236) amps into stock TD-1s and could smell the glue burning but didn't damage any drivers or components.  Then I did a gig shortly after that where the BE totally clobbered the system and I actually burned up some mid range drivers. This was clearly a case of ínot enough rig for the gigí and I tried to learn my lesson ;).  After that I decided to run them on single channels rather than bridged just to save the drivers.  But this left me short quite a few db of what I was used to. 

My ideas for a custom crossover were to take out some of the padding but also to steepen the filter slopes for better driver longevity.  I would then use some DSP to correct what could be corrected.  But in the end I needed more SPL even if it wasnít the ďbest soundĒ.  Before I started working on that I had a chat with Tom Danley and he said that there was interest in designing a new crossover for the TD-1 based on his Synergy advancements.  I guess Mike Heddenís installation company had some requests for this kind of thing from existing customers who had TD-1s installed years before.  After some back and forth I ended up lending Tom a TD-1 to measure and develop the new crossover.  Once he was done with the design on paper i decided to build his "TD-2" crossover for one box.  I found it was even "quieter" than the original, although it sounded a lot better.  I wouldnít suggest it for getting more usable dbís out of a lower voltage amp.  But for big amp power, it might be a good option. 

My ďTD-3Ē crossover increases the filter slopes considerably and is quite a bit louder on a "600-800 wattĒ amo.  But, it requires some processing to be usable and I donít have the documentation or details organized in a format that will likely make sense to anyone else.  The raw response is midrange heavy and the phase is considerably worse than even the original crossover. I have 2 different kinds of processing to address this.  One is an FIR ďcorrectionĒ that I worked up that flattens the phase and frequency response pretty well.  The other is an unusual way I configured a DCX-2496 processor where I mix multiple outputs together. 

SAC thread: https://www.prosoundtraining.com/forum/view_thread.php?thread_id=171120&page=1&sort_order=asc
I took the original post a little differently. I think he meant to replace the old worn out drivers with new eager drivers. Not to swap out drivers willy nilly. In the case of the TD-1 I have these comments:
 
A) Tom has moved on from the B&C DE25 driver that was in most of the Sound Physics Labs boxes to more "modern" drivers. Most of the similar designs in the current catalog use the BMS 4550 which has some solid advantages over the original. That said, the DE25 driver is still a pretty good sounding device and replacement diaphragms are available for a reasonable price.

B) The mid drivers are pretty reliable but can suffer issues over time. I've seen a number with some tilt to the cones. There isn't much out there that could offer an improvement over the originals. Danley has replacement drivers that are largely the same (if not the same) specs as the originals and the price isnít too bad.
 
C) The woofers in the original were what I would call a medium duty pro woofer from Eminence. The newer DSL models are using beefier 12" woofers and some improvement to the TD-1 could be made with a "betterĒ model woofer depending on what you want to ďimproveĒ. In my opinion, a woofer swap is the most benign change that you could do. The mids and comp driver are much more critical to the reasonable function of the box and you wonít want to change either of those without knowing exactly what youíre doing.

D) The crossover in these is critical. In a typical 2-way box with a separate horn and woof you can change some things up in the crossover and maybe not notice depending on where in the pattern you are listening. The thing about a Unity design is that itís gotta be ďrightĒ or itís wrong everywhere. Again, Tom has a newer crossover (with about 3 times as many parts) that uses the BMS driver and puts this box up close to an SH50 in terms of frequency response and phase. I would expect it to be a nice upgrade for an install that has been using these things for 10 years. That said, I have a crossover design that takes a different approach to Tomís and delivers wonkier phase in exchange for more sensitivity. For my purposes itís a tradeoff Iím willing to make and my portable system has never sounded better (using the original DE25 too!).

Thanks for the journey! I enjoyed it.

First, I've never reconditioned a speaker. I just know I'm capable of learning and SMAART ;)

Second, I just grabbed them out of storage to look at where they're currently at. I originally started restoring them a bit with Ara Ayrassian's help, but I didn't get much further than upgrading one of the resistors to 50w, testing them TF trace, and cleaning them.

Third, My overarching goal is to make them loud/usable as my 'big rig' for if/when that ever happens.

Lastly, I have an Xilica, Ashly ne8800, and other DSP at my disposal so I can do FIR or IIR filters as needed.

My plan is to test each component individually and make sure it's working.
Then each section.
Then put it together.
Getting TF traces along the way to document/ensure the journey is progressing correctly.

I read through your SAC post, very informative. Thoughts: Should/could I update these using the  SH46 drivers? Or should I keep these stock? Or could I do a bit of both?

Have you considered bi-amp (or tri-amp) running these and using FIR filters to increase filter slope allowing for higher power, yet keep same relative phase so synergy works?

Handles:  I have one box with the "Tour Shell" and I find it to be a pain.  Itís heavy duty but itís not configured in a useful manner.  But it does have handles in the vertical sides.  I have another box that has the same handles but without the ATM fly hardware.  Itís obviously lighter.  But the rest of my boxes are the install models and therefore had no handles.  After quite a bit of thinking about it I decided to put handles in the ends.  They donít mess with the side wall strength so theyíre ok with my fly track that I installed on a few boxes.  The factory handles are a little bit nicer for just general lifting but I think the end handles are actually more useful for a few of the ways that I deploy them.

Iíll have to look up which handle I used but they are a Penn Elcom model.  And they are symmetrical.  Plastic cup with an aluminum bar.  I actually routed in recesses with a hand router using a template a made.  Iím not sure if thatís still around.  If you want to put handles in the factory positions I seem to recall seeing a drawing with the handle positions somewhere.  Iíll try to find it.  Iíll upload it here if/when I find it.  www.audiovidual.postach.io

Bi-amp - Tri-amp:
It certainly opens up some options.  I didnít go down that path for 2 reasons.  One was simply the cost of it.  I didnít feel like I could justify adding that many more amp channels, processing and specialized cabling.  And, the complexity was a turn off.  If I bi-amped then I could use NL-4 cable but subs would have to be cabled separately.  If I tri-amped, would I use NL-8 (ugh) or use non-bridged amps and do a setup with NL-4 where I assign one pin as a common ground? Amp racks would not be interoperable with other speakers.  If I bi-amped, which crossover was the more important one to do?  These were all the questions that I didnít answer.  But you could sure dial in a sweet response that way.

Measurement: 
This is going to be crucial.  I have lots of old traces but so much time has passed and notes are so sparse, I wouldn't want to share them.  I would suggest you setup and do some fresh measurements.  Take each band separately and drive the drivers directly.  In other words, bypass all the passive crossover stuff.  Short out the drivers in the other bands when you do this.  This should be very revealing about what the crossovers need to do.  The compression driver is covering a huge range.  When you measure it, in particular, take measurements at various angles besides just on axis.  Although Unity/Synergy is proud about having the same response everywhere, there are some variations.  I seem to recall some funny stuff in the 4-6k range in the vertical.  I believe itís caused by reflections off of the midrange entrance holes.  Keep these variations in mind when designing crossover processing since the processing affects every angle the same. 

Individual Drivers:
Your plan to test drivers before doing all the measurements is good.  Be careful taking the mid drivers off.  You will probably tear the paper gaskets.  But if you are careful to put them back together the same way they came apart, it shouldn't be an issue.  Some elmers glue can be used to glue them back together if you deem it necessary. 

Improvements: 
As far as changing the componentsÖ Iíve spent some time looking at this.  The old DE25 driver is actually pretty good.  Iíve only had one complete diaphragm failure and the replacements are fairly cheap.  I did have some units in TRIKs that didnít sound the same.  I think it was from a rainy show where the horn got water in it.  Anyway, I think they sound quite nice.  But I do think some newer drivers could be an improvement.  The problem is that you have to buy them to test them.  Making decisions about compression drivers based on a spec sheet is challenging.  The BMS 4550 or 4552 could be considered an upgrade.  I think I have comparison measurements between the 4550 and the DE25.  But I donít recall it being significantly louder.  The most promising/interesting driver Iíve seen is the B&C DE550.  It has a larger diaphragm than the 25 which means less excursion for a given SPL output.  It has nearly 3db more power handling.  But looking at the response graphs, it seems to have a couple less db of sensitivity at the very top end which means a little more ďboostĒ in the processing to flatten it.  (larger diaphragm means more mass which means more drop off in the top end). Of course, until one of us puts one on a box and compares, we donít really know how or if itís an improvement. 

SH46 components - The SH46 is a different enough box that it doesnít really help us here.  Tom went with a 1.4Ē exit driver so the compression driver is out.  And, one of the reasons he went that way was because it could go lower.

The mid drivers that he used are actually smaller in diameter which means that wonít mount directly to the TD-1 horn.  And, contrary to what we might assume, Tom told me that they donít actually go as high in frequency as the original drivers.  I (like many others) have actually spent quite a bit of time looking for an improved mid driver for Unity/Synergy designs.  There arenít many that improve the original driver.  Even though itís a rather narrow band of frequencies, getting a driver that can both go high enough and low enough is challenging.  One that looks promising is the little 3Ē Faital driver.  But itís not a closed back.  A friend of mine and I were working on a plastic rear cup that would seal it but we never really got it complete.  Regardless, I donít know that it would be possible to make it meet up with the existing entrance holes.  At this point, I donít know that any improvements are out there in the midrange department.

Woofers could be upgraded.
I always expected to change my woofers out for neo drivers when the time came.  Early on I experimented with the Eminence Delta Lite neo drivers and had one box outfitted with them.  A couple years ago I noticed a problem with a box and it turned out to be a blown Delta Lite driver.  So, I swapped back in the original eminence drivers.  Most of the Danley boxes (SH50, SH46) have (last I knew) B&C woofers that are probably at least 3db louder.  Iím all for shaving weight off of these things so if you have the cash, I would consider the high output neo drivers.  Since they only play up to the 300-500hz range, there arenít as many considerations to balance for the woofers.  So long as they play fairly well with the semi sealed enclosure, and match the bolt holes, they will probably work.  Most of the Synergy boxes vent the low frequency section back into the horn.  This is kind of like a regular vented box where the bottom octave gets a boost in level in exchange for a larger box, a faster roll-off below cutoff and a greater phase swing in the bottom couple octaves.  The big advantage for the Synergy boxes is to get a little bit lower F3, which is desirable for the church installation market that Danley is so strong in.  They often spec the SH50 and other boxes without subwoofers.  In these cases, going down to 70Hz instead of 90 or 100, means a significant cost savings for the client.  Since I/we are always using ďSubs", Iím not sure that this is a big advantage.  I havenít worked out if itís workable for the TD-1. 

You've given me some great ideas, I'll need help weeding the chaff from the wheat though since I'm quite new to speaker tinkering. But this might be a fun project :) I think the BMS 4552ND looks sweet (+20kHz), ~5dB louder 108.5 -> 113 sensitivity & lighter :)

I think I'll turn our conversation into a thread.

The 4552nd is one of my favorites. I used them in a prototype pair of speakers that I made over 10 years ago and they still bring a smile to my face every time I hear them.  Itís very close to the response of the 4550.  Let me see if I have the comparison measurements between the DE25 and the 4550.  I may have even measured the 4552 on the horn as well.  Before you assume 5db more sensitivity, letís get some comparative measurements.  And Iím pretty sure the 4552 has a much lower impedance so that increase in sensitivity might not equate into more maximum SPL.

I am having weird issues right at 4khz about 400hz wide where it's about 8 or 10 dB down. I need to get fancier with my measurements.

---

Recently, I had some 'fun' and "tested" the TD1 with my Yamaha HS8 and SRX835p

There were huge differences. Which sounded better at low volumes? Who knows.

We played: Johnny Cash's -  Solitary Man. And in general it seemed like his voice was real and visceral with the TD1 & HS8, but the SRX lacked it a bit. But the SRX handled pop music better with a better midrange sound.

I grabbed my spl meter too. Both (SRX & TD1) hit 131dB @ clip @ 1m in my room so that's good.
I know the SRX get loud enough to be deafening so if the TD1 can get just as loud then I'm fine with that.
« Last Edit: August 09, 2018, 03:05:42 pm by Nathan Riddle »
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Art Welter

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Re: SPL TD1 Recondition & Improvements
« Reply #1 on: August 09, 2018, 02:18:21 pm »

Nathan,

Testing of the individual components is a good idea, no reason to replace them if they work well.

Since protection of the drivers is important, and you are not happy with the present passive crossover, going three-way active would be the way to go unless you want to devote a long time to developing a flat phase passive crossover and HF limiting circuit which will be specific to the drivers.

Even if you ultimately wish to retain the "simplicity" of a passive crossover, working through the crossover in active form will inform you of what is required in a passive version.

Cheers,
Art


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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #2 on: August 09, 2018, 03:36:20 pm »

Nathan,

Testing of the individual components is a good idea, no reason to replace them if they work well.

Since protection of the drivers is important, and you are not happy with the present passive crossover, going three-way active would be the way to go unless you want to devote a long time to developing a flat phase passive crossover and HF limiting circuit which will be specific to the drivers.

Even if you ultimately wish to retain the "simplicity" of a passive crossover, working through the crossover in active form will inform you of what is required in a passive version.

Cheers,
Art

Thanks, Art,

My thoughts on replacing lows would be to gain some more (rock) SPL and maybe lighter weight. Though in talking with Drew moving to NEO drivers in the LF would probably only net me +3dB and I believe Pat Brown says a reasonable upgrade is 6dB.

I don't think anyone has figured out a better mid, so that's out of the question.

The reason to transfer to the BMS driver would also be SPL, but it would be three-fold as it would also be lighter, & extend the FR further out to 20k (not that that's really a big deal). But I did see a thread on the DSLUG about the HF brightness missing for the EDM/DJ crowd.

I'll be honest, I don't think I know enough about passive crossover design to actually implement it effectively. I would LIKE to keep them passive as it's easier to deploy. I agree with you on starting with active as I think the process of working on them in active form will help me learn in general which is part of my goal here. And I can much easier use trial and error to my advantage.

I think I've mostly settled on upgrading xover and installing the zener diode + light trick for the DE25 that Ivan spoke of in one of the posts referenced.

---

I'll post some traces up later tonight.
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #3 on: August 09, 2018, 09:47:53 pm »

I think I messed up my measurements a few times. I need to get more precise and follow best practices.
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #4 on: August 09, 2018, 09:57:53 pm »

For reference my HS8 & SRX835p & 3TX (that just arrived; thanks Mark!)
« Last Edit: August 09, 2018, 10:04:22 pm by Nathan Riddle »
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Mark Wilkinson

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Re: SPL TD1 Recondition & Improvements
« Reply #5 on: August 10, 2018, 10:57:05 am »



Goals:
1) Restore the TD1 to full working order so I can use on 'big gigs' or where pattern control is necessary.
2a) Implement improvements: louder, lighter, sentinel protection [at least hit its original goal of 137dB & perform well in a live/playback/gig situation]
2b) Add handles
3) Learn more about the TD1 & Synergy horn concept
4) Learn more about measurements in speaker design
5) Learn more about speaker design (parallel)
6) Have fun



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
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josh allman

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Re: SPL TD1 Recondition & Improvements
« Reply #6 on: August 10, 2018, 04:00:26 pm »

Hah, this is a cool thread.

I think bang for the buck you just can't beat these. I've never found myself in a position of needing them louder! Potent, heavy boxes, these are.

I would agree that overall they are bright and I'd probably want more of everything below 1k.

I have been pondering selling my collection of them (I have 6, two are not currently in my possession, the other four were reconditioned by a former SPL emp) to put towards some of Tom's newer designs, but I am all for options to make these better. I have also considered using them in a HT setup. Could be awesome!
« Last Edit: August 10, 2018, 04:02:36 pm by josh allman »
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Ivan Beaver

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Re: SPL TD1 Recondition & Improvements
« Reply #7 on: August 10, 2018, 04:04:54 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.
 
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josh allman

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Re: SPL TD1 Recondition & Improvements
« Reply #8 on: August 10, 2018, 06:20:50 pm »

Looking at archive.org, they mentioned this in parenthesis, which is not present in the PDF of the TD-1 I have:

65 Hz-20kHz Ī3dB (2 or more boxes)

That might explain why mine seem to be lacking in lower freq output.

Nathan, what did your "extensive EQ" end up looking like?
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Nathan Riddle

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Re: SPL TD1 Recondition & Improvements
« Reply #9 on: August 10, 2018, 11:34:26 pm »

Looking at archive.org, they mentioned this in parenthesis, which is not present in the PDF of the TD-1 I have:

65 Hz-20kHz Ī3dB (2 or more boxes)

That might explain why mine seem to be lacking in lower freq output.

Nathan, what did your "extensive EQ" end up looking like?

Yes, I recall someone saying Tom designed them to be 6dB down for coupling in the LF (as they were designed to be used in pairs)

See attached EQ. Note this is me fiddling around in my room. I honestly don't think it sounded that good (lack of bass), but flat does have that 'sound.'
I turned off all the LF filters and it sounded much better with my 2nd EQ try. Though I doubt it was flat at that point.
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