SDa/M SRS... Can we do it?

halo71

TennMan wrote: »

Thanks Mr. Bubbles. It brought a smile to my face when I read that. I should have followed your advice about not giving out results. I put my CRS+ crossovers and MWs in my monitor 10B cabinets and caught a lot of flack from some folks here who said it would never work and I screwed up a good pair of speakers. That has been well over a year ago and I still listen to my hybrid speakers every night and fully enjoy them. I have no regrets other than telling about what I had done here on this forum.

I remember that! I have some 10's sitting unused that I would not hesitate to try your mod on them someday. As long as I knew i could change things back to original if I wanted. I did a similar thread like this one years back, asking about making new SDA cabinets etc. Sorta what you alluded to, I thought I was gonna see people with pitch forks and torches in my front yard before the night was over! lol

motorstereo

halo71 wrote: »

I remember that! I have some 10's sitting unused that I would not hesitate to try your mod on them someday. As long as I knew i could change things back to original if I wanted. I did a similar thread like this one years back, asking about making new SDA cabinets etc. Sorta what you alluded to, I thought I was gonna see people with pitch forks and torches in my front yard before the night was over! lol

I had to laugh when I saw that one. For some real fun try stacking some sda's and posting pics and listening impressions of what's been done:evil:. I was also thinking lynch mob myself. There's lot's of passion here for those old Polks and you'd swear some folks feel that they're actually living, breathing objects.

PolkieMan

I agree 1C vs 2.3TLS but there is some distance there, same reason you could not have the CRS sitting vertical

westmassguy wrote: »

There must have been a lot of wiggle room there. If you compare the early SDAs, and my 2As, the drivers are almost touching, where-as the big SRSs have quite a bit of room between them.

TennMan

PolkieMan wrote: »

I agree 1C vs 2.3TLS but there is some distance there, same reason you could not have the CRS sitting vertical

The difference in MW spacing might have an impact on the SDA sound my old ears couldn't hear it. My CRS+ have a wider spacing than my monitor 10s but when I swapped the CRS+ MWs and crossovers into the 10s I couldn't tell a difference in the SDA sound.

I don't think the folks at Polk thought it was a big deal either because they used the same drivers and crossovers in the CRS+ (wide spacing) and the 2Bs (narrow spacing like the 10s). I'm guessing that the CRS had a wide MW spacing so the cabinet would accommodate the PR being mounted on the back side. I'm also guessing that the bigger speakers being wider was a matter of needing to put the tweeters down the center to keep the cabinet at a reasonable height more than the effect it would have on the SDA sound.

Hmmm, that sure is a lot of thinking and guessing. Maybe the guys who can hear a fly land on their grill cloth will have a different explanation for differences in SDA MW spacing.

Tegucigalpa

nooshinjohn wrote: »

Anybody here a wiz at CAD?

SolidWorks Pro 3D right here. Have all my own software.
What are you thinking?

Drenis

Mr. Bubbles wrote: »

I could really give a crap less if you think so or not. Again, please re read my posts; you suggested building around the original cabinet and my response was plainly that i would not recommend doing that. BUT JUST IN CASE YOU HAVE COMPREHENSION ISSUES LET ME STATE AS PLAINLY AS I POSSIBLY CAN, I DO NOT RECOMMEND THAT ANYONE MODIFY THEIR ORIGINAL CABINETS. Cabinets can not easily be changed back like crossovers, wiring etc. Also without the original cabinet for comparison (in listening as well as taking measurements), there is little to go on to guarantee improvement. If you have further questions please state them plainly and I will gladly give my opinion on how I would address such an issue personally. None of my comments are meant to describe to any other member of this forum that they should do things as I do. Their speakers are theirs and mine are mine. I will do as I wish with mine without giving results to anyone on this forum but will answer questions to any that ask or present ideas.

I'd like to think my comprehension is up to par. I've re-read your *post* because it was only the one I commented on and I keep shaking my head. I'm happy you stated your opinion regarding redoing a cabinet from scratch or heavy modifications. However, If you're going to exclusively reply back and state no, its a bad idea and list 3 of your own reasons why building a shell over the existing OEM cabinet. Then why is it you wont elaborate on your reasons... I'm sorry, I mean facts?

Any ways, At this point, I don't care. I'm just looking forward to see what John does. As Face mentioned already, if someone wanted to even begin doing this RIGHT, there is more than just rebuilding a cabinet...

KCCO

nooshinjohn

A great point there KCCO... Let's see what comes of this. Again, the purpose of the thread is to not re-hash what has already been done. Instead I want to focus on design elements, materials, features and other aspects we would like to see in a new SRS-type speaker. Also, I am seeking input from those that have made the SDA speakers that currently exist perform better than when they were new. Surely the knowledge and skill exist here within this forum to come up with a modern form for these classic speakers.

SDA1C

John,

I would think something in fiberglass could hold the same volumes and render the cabinet shapes you are after. My concern is the front vs. back slope. The PR being "fluid coupled" and the drivers being isolated by polyfill, I would think as long as the volume stays the same there should be no real problems with a new cabinet, given the same config for the drivers that is. I wonder how, without having an extremely wide front, you will be able to get the curves or slope front to back that you are after.

You know they will be worth the same as the 7's by the time they are done right LOL.

nooshinjohn

The only aspect of the front baffle tha can be altered would be the outside edges, and even that gets you only a couple inches. The tapered sides would result in the new speaker being deeper than the existing box by a few inches. I am also looking at the way the feet are designed on the /M's and how such a system could be incorporated into the new cabinets.

First up however are going to be new signature plates for the SDA's I have already. They will be satin nickel finished with resessed signature and other information that the current plates have on them. I will post up pictures of the new plates as soon as I have them, and if I can get Polk's blessing, I will make a bunch of them for whoever may want a set...

Mr. Bubbles

However, If you're going to exclusively reply back and state no, its a bad idea and list 3 of your own reasons why building a shell over the existing OEM cabinet.

I am sorry I have no idea what you are saying here.

3 of your own reasons why building a shell over the existing OEM cabinet.

My own reasons why building a shell over the existing cabinet what? This does not appear to be a complete sentence and I am unsure what ending you had in mind.

Then why is it you wont elaborate on your reasons... I'm sorry, I mean facts?

I believe I have described my reasoning in a very basic sense. If you would prefer more detail please let me know exactly which part you would like me to explain in more detail. Again you may want to re-read; I have not mentioned any "facts", but have given reasoning (albeit very general) behind my opinions. And they are only that; my opinions, based on my education and past experiences in and around the audio industry.

Unless you ask for more specific clarification, I will not continue this back and forth discussion past this post, in an effort to prevent things from getting any more heated than they already may be. May you enjoy your Polks as well or better than I enjoy mine.

PolkieMan

I for one would like to see them

nooshinjohn wrote: »

The only aspect of the front baffle tha can be altered would be the outside edges, and even that gets you only a couple inches. The tapered sides would result in the new speaker being deeper than the existing box by a few inches. I am also looking at the way the feet are designed on the /M's and how such a system could be incorporated into the new cabinets.

First up however are going to be new signature plates for the SDA's I have already. They will be satin nickel finished with resessed signature and other information that the current plates have on them. I will post up pictures of the new plates as soon as I have them, and if I can get Polk's blessing, I will make a bunch of them for whoever may want a set...

nooshinjohn

I just spent the better part of my day adding Larry's rings to the left channel speaker and I must say I am impressed that these speakers deliver so much performance given the shortcomings of these cabinets. The materials used were not the highest grade possible even for back in the day. The particle board is not very good to say the least.

The addition of the rings to the left cabinet has shown there is a significant improvement in sound over that of the right cabinet. I attribute this to the better coupling of the driver to the baffle, and reduced resonance in the driver. I could be wrong on the physics of it.

I am even more convinced ther are performance gains to be made with stereophonic SDA technology by designing a better cabinet. I have some sketches of the new cabinets, and will grab some measurements from the internals when I do the rings on the right side tommorow.

I should have Internet in another week or so and will get the pics on line as soon as I can.

Tegucigalpa

Post up those sketches and I can draw them up 3D.
Then the design ideas can be tweaked in way you want.

nooshinjohn wrote: »

I am even more convinced ther are performance gains to be made with stereophonic SDA technology by designing a better cabinet. I have some sketches of the new cabinets, and will grab some measurements from the internals when I do the rings on the right side tommorow.

I am with you on this one.
When I first got inside my cabinets (SDA SRS) I was really surprised at the 'cheapness' of the internals.
The wiring and the quality of wire is shoddy at best, the crossovers were falling apart.
And the cabinet just doesn't seem beefy enough for the number of drivers that are attached to it.

Face

Tegucigalpa wrote: »

When I first got inside my cabinets (SDA SRS) I was really surprised at the 'cheapness' of the internals.
The wiring and the quality of wire is shoddy at best, the crossovers were falling apart.
And the cabinet just doesn't seem beefy enough for the number of drivers that are attached to it.

Have you seen the internals of many other cabinets from that time?

As for the cabinet itself, a "beefed" up cabinet of that size would have added a substantial amount to the price tag.

F1nut

I'll add that the wire and the wiring is a lot better than you imply and much better than I've seen in other speakers. I don't recall seeing any SDA crossovers that were falling apart either, so not sure why yours would be.

Tegucigalpa

Face wrote: »

Have you seen the internals of many other cabinets from that time?

As for the cabinet itself, a "beefed" up cabinet of that size would have added a substantial amount to the price tag.

True that.
I'll admit, these speakers are very impressive in the way that they deliver performance.
And $3000 back in '86 was pretty steep for the average Joe.
I'm just saying that I was somewhat dissapointed when I got inside them.

F1nut wrote: »

I'll add that the wire and the wiring is a lot better than you imply and much better than I've seen in other speakers. I don't recall seeing any SDA crossovers that were falling apart either, so not sure why yours would be.

The plastic tabs (in right speaker) that hold the circuit board were completely bent over, like as someone tried to push the board onto the tabs before they were lined up.
The wiring inside is pretty messy and sloppy on the connections.
Who knows, maybe the guy I bought them from did some handy work inside the cabinets.

PolkieMan

Original owner, one of my plastic tabs on one the standoffs that hold the inductor to the x-over board on my left speaker was like that too.Also there was the thick paper/felt piece that was suppose to be on the back of the SB radiator lying in the bottom of the cabinet. And yea I paid $2500+tax in 1990 for 2.3tls, which was a lot.

Tegucigalpa wrote: »

True that.
I'll admit, these speakers are very impressive in the way that they deliver performance.
And $3000 back in '86 was pretty steep for the average Joe.
I'm just saying that I was somewhat dissapointed when I got inside them.





The plastic tabs (in right speaker) that hold the circuit board were completely bent over, like as someone tried to push the board onto the tabs before they were lined up.
The wiring inside is pretty messy and sloppy on the connections.
Who knows, maybe the guy I bought them from did some handy work inside the cabinets.

nooshinjohn

Internal volume is 6.75 cubic feet, including internal bracing.

Toolfan66

Why can't one upgrade the drivers and tweeters with better quality ones and just do the math of what values are needed for the capacitors, resistors, and inductors?

I only ask because for one I wouldn't know and two there are a lot of DIYer's that have the skills in building quality DIY speakers..

Why couldn't it be done? Don't throw out the cost to much, in this hobby there is a lot of I don't care what it cost I just want it so I shall have it's...

Toolfan66

Toolfan66 wrote: »

Why can't one upgrade the drivers and tweeters with better quality ones and just do the math of what values are needed for the capacitors, resistors, and inductors?

I only ask because for one I wouldn't know and two there are a lot of DIYer's that have the skills in building quality DIY speakers..

Why couldn't it be done? Don't throw out the cost to much, in this hobby there is a lot of I don't care what it cost I just want it so I shall have it's...

SDA's with ribbons or horns? LOL !!:eek:

Face

It's more than just math as far as using new drivers, simulations and measurements would be needed. For an "upgraded" 2B it wouldn't be too difficult, the larger models would be a nightmare unless one went active or stuck with a single tweeter.

Toolfan66

Face wrote: »

It's more than just math as far as using new drivers, simulations and measurements would be needed. For an "upgraded" 2B it wouldn't be too difficult, the larger models would be a nightmare unless one went active or stuck with a single tweeter.

Yeah I figured as much. As simple as a speaker really looks there is a lot going on to make it work, I do get that. But when looking at it it does look simple. But if it was everyone would be doing it though right?:razz:

PolkieMan

Well 2B or CRS+ then. I think the 2B would be easier to work with.

Schurkey

Face wrote: »

It's more than just math as far as using new drivers, simulations and measurements would be needed. For an "upgraded" 2B it wouldn't be too difficult, the larger models would be a nightmare unless one went active or stuck with a single tweeter.

And yet, it was do-able in the late '80's--early '90's with about half the computer simulation/computer aided design power that's available to today's committed hobbyest.

Major Problem: It still helps to be smarter than the computer. GIGO.

Face

Schurkey wrote: »

And yet, it was do-able in the late '80's--early '90's with about half the computer simulation/computer aided design power that's available to today's committed hobbyest.

Major Problem: It still helps to be smarter than the computer. GIGO.

I didn't say it would be impossible. If I did this for a living, I'd say "no problem". :cheesygrin: And you're right, the computer doesn't tell/do all. After running sims, I still fine tune with 5 bins of caps, coils, and resistors.

FTGV

Face wrote: »

... the larger models would be a nightmare unless one went active or stuck with a single tweeter.

Though I don't think one would want to try a duplcate the multi tweeter progressive point source actively.:eek::cheesygrin:The main hi pass could be done actively but you might want to retain specific passive parts in series with each tweet.

nooshinjohn

Just a small update here... Next eek I meet with a professional cabinet shop about these speakers. This shop is the west coast vendor for factory finish repair for B&W and a few others, as well as doing grand piano restoration. This should give me an idea as to cost. I won't even begin to take this on if I cannot take it to a very high level of finish quality. If these are to have any life at all, I want them to be something that Mr. Polk would be proud to stand next to in his famous white labcoat.

Do it right or not at all on these. That served me well on the amps so lets see what happens.

chandler9a

AMEN brother, I agree. Can't wait to see what happens with these, I have thought about the same thing for years now.

nooshinjohn

Finishing costs on these will be around 2500.00, but for that money, these speakers will be world-class "production ready" speakers that incorporate the latest in cabinet construction and of course, all current upgrades and modifications.

Magnetic grills are also in the works for these.... It will be a long journey from here on, but I am pleased to say that the idea is a go!

Anyone that wants to bring their skills, ideas and talents to the fore, and help me bring them to life, shoot me a pm or post your intentions here. There will be a new thread when the build begins.

Coming in 2014, the SRS/M!

Face

I hope you have your tweeters and crossovers upgraded first.