old spare speakers lying around...OB?

[Fran604g]

Hello collective hive,

I've mentioned in other threads my intention to build my 1st ever OBs using my recently brought back to life 10" Carbonneau (Heathkit AS-1373) woofers teamed up with a couple FR 7" Jensen C-840 (of which I know nothing about other than they work and were used in a PA system) drivers. At first, my intention was to simply mount them both in some old shelves cut to size and see what happens. Then, as I read about H-Frames being used around here, the recipe got a bit more interesting for the woofers. For each OB/H-frame I would use one 10" woofer below and one Jensen 7" FR driver on top. That's simple enough, and I could just (probably) run them both FR not worrying about even a simple 1st order crossover to start. Then go from there to experiment and fine tune.

Since I'm apparently on a roll around here lately reclaiming forgotten "treasures" (aka junk) that was stashed years ago, I got thinking about the spare AR4x drivers I have that came out of a pair of trashed yard sale cabinets. I managed to put together a good single AR4x out of that pair, with a leftover woofer, tweet and crossover. The foam surround on the woof needs replacing of course, but the VC seems fine. I'm going to fix that very soon.

Then I thought: just for fun and to use up the AR4x loose drivers, could I combine them - 1 woof & 1 tweet & crossover - on each OB (kind of used as an adjustable MF/HF section), along with the 10" woofer H-Frame below and the Jensen 7" FR on top? Kinda like building a dummy's 4-way speaker system in a really simple way with an adjustable crossover only used for the mid-bass/HF AR4x drivers. The 3 sections would be run FR, or if needed I could add a simple dividing network between the 10" woofer and AR4x sections to blend the bass and see how it sounds. Maybe even add an L-Pad if I think it could help. I have some of them lying around too.

I have a speaker selector box doing nothing at the moment for 3 pairs of speakers, so I could wire each section to make sound or eliminate any of them with the push of a button to A/B/C them.

Whattaya think?

 

[RPMac]

I say go for it
Have fun

 

[mhardy6647]

I mean, it's a pretty low bar.
That said, loudspeakers meant for an acoustic suspension alignment probably aren't the best for open baffle use. (EDIT: well, given your proposed use case, I am probably way over-thinkin' things!)

I... think I'll shoot you a PM. Gimme a bit...

 

[Fran604g]

I mean, it's a pretty low bar.
That said, loudspeakers meant for an acoustic suspension alignment probably aren't the best for open baffle use. (EDIT: well, given your proposed use case, I am probably way over-thinkin' things!)

I... think I'll shoot you a PM. Gimme a bit...

I figured that's the case. I think I'll lose a lot of the low end of the AR4x woofer, but I'm hoping to pick some up with the H-frame. I'm still thinking about the speaks in my Magnavox SK-44. There's a big woofer in there with the accompanying mid and tweets, all driven by a 3-channel amp. 6BM8. I'll be digging it out of the barn once warm weather gets here.

I just have this primal urge to do something with all these orphaned speakers...

Chicken scratchings of a feeble mind:

 

[TimNick]

Build a test mule and try em out.
Modify as needed & swap out drivers to discover what really works.
No heavy boxes to mess with and BONUS...
Pretty easy to make H-frame look presentable.

 

[RPMac]

I figured that's the case. I think I'll lose a lot of the low end of the AR4x woofer, but I'm hoping to pick some up with the H-frame. I'm still thinking about the speaks in my Magnavox SK-44. There's a big woofer in there with the accompanying mid and tweets, all driven by a 3-channel amp. 6BM8. I'll be digging it out of the barn once warm weather gets here.

I just have this primal urge to do something with all these orphaned speakers...

Chicken scratchings of a feeble mind:
View attachment 59573

I thought of doing something like that….EV T-35, Fostex 103 & 166 and an EV SB12B for woofer. Even cut a baffle out….an old door.

 

[mhardy6647]

I thought of doing something like that….EV T-35, Fostex 103 & 166 and an EV SB12B for woofer. Even cut a baffle out….an old door.

That's what I'm talkin' about!

 

[Fran604g]

As I continue to understand the intricacies involved in practicing the HiFi voodoo dark arts that I thought I understood well enough, I was doing some (more, not new) reading, trying to refresh the stale dried up brain cells this morning. I'm still thinking about the likely negative issues my OB/H-frames will exhibit, and how to better understand what I'm going to build.

I came across this take on loudspeaker systems design which is fairly standard (maybe) mid level knowledge. It's good for me to brush up on elemental knowledge to keep perspective. It sort of anchors me, if that makes any sense.

Speakers: Principles

Understanding loudspeakers and speaker behaviour

education.lenardaudio.com

One of his statements concerning inter-modulation struck me in relation to my experience with surround sound systems, whether here at home or in the cinemas:

This problem is most noticeable at venues and Live concerts where not a single word can be understood. We have become so accustomed to hearing inter-modulated sound from distorted sound systems that we have accepted it as being normal.

I think this explains why I have trouble with those systems and consequently hate them so much. I've spent nearly my entire life (60 of 65 years) around decent to great stereo HiFi systems. The result is, I think, my brain is so hardwired for that environ that other forms of sound reproduction don't make sense to me. I have frequent trouble deciphering words within the sound envelope, considerably without some screwing around with the EQ significantly. Therefore, there's absolutely no "one size fits all" setting for the surround system we have used.

Sound familiar to anyone? I get that hi-end home audio surround systems can, and probably do eliminate this phenomenon, but that's (kinda) not my point.

 

[Poultrygeist]

Woofers with low Qts require a box enclosure. The air in the box acts like a spring for the tighter suspension of the low Qts woofer.

Higher Qts woofers ( above .7 and the higher the better ) have a loose suspension that's needed to move air and produce bass in the free space of an open baffle.

 

[Fran604g]

Woofers with low Qts require a box enclosure. The air in the box acts like a spring for the tighter suspension of the low Qts woofer.

Higher Qts woofers ( above .7 and the higher the better ) have a loose suspension that's needed to move air and produce bass in the free space of an open baffle.

Right. I'm thinking I'll end up with mid-bass (<100 Hz maybe?) and most likely good mid and adequate (for me) high freq. Now I'm thinking much more seriously about the low to sub freqs. I'm sure they'll be very anemic below 100Hz.

I need the nice, warm weather to get out in the barn and start putting something together. Pretty excited!

 

[mhardy6647]

IME and IMO -- a speaker (driver) that sounds good in free space is a good sounding driver and is worth investing effort into.
The converse, I believe, is also true.
Case in point. My first ever experience with Altec Dupexes. I happened to be visiting Gary Kaufman's house when he had just received a pair of 604C Duplexes with the stock Altec XOs. He unboxed them and said "let's see what they sound like!", so he sat them on the floor, hooked them to his amp at the time (which I think was his 45/46/300B Ragtop* amp) and he played some Ella through them. Yup.

________________
* Convertible

 

[RPMac]

”sounds good in free space“ I think I read that on the Glow in the Dark. Inspired me to use 414’s in open baffle.
Haven’t had the desire to listen to anything else since.

 

[mhardy6647]

The famous little (4 inch) PartsExpress 269-469 "69 cent wonders" were (are) like that, too. Hook one to an amplifier, hold it in one's hand and listen to the sound that comes out. It sounds good.

 

[Fran604g]

IME and IMO -- a speaker (driver) that sounds good in free space is a good sounding driver and is worth investing effort into.
The converse, I believe, is also true.
Case in point. My first ever experience with Altec Dupexes. I happened to be visiting Gary Kaufman's house when he had just received a pair of 604C Duplexes with the stock Altec XOs. He unboxed them and said "let's see what they sound like!", so he sat them on the floor, hooked them to his amp at the time (which I think was his 45/46/300B Ragtop* amp) and he played some Ella through them. Yup.

________________
* Convertible

When I brought my 604-8Gs home that's exactly the first thing I did.

The complete (long) story behind how I obtained them has probably been repeated too many times, so I'll fight the urge to repeat it again.

I had previously tested them - sans the odd and very small semi-circular enclosures - along with the rest of the sound system electronics after we (the Chef/owner, me - a lowly sous-chef - and a co-worker) dismantled everything in the building we took over to construct and open a second restaurant. The previous business had been a disco, and these were mounted to the ceiling along with 2 15" woofers - 515s? All 4 speakers never went back into use and were simply kept on a shelf in our dry-storage area. Unfortunately I was unable to locate the 2 woofers before another tenant took over the space after our relatively short-lived 2nd restaurant went under and closed.

So consequently, I wasn't completely unprepared for my 2nd experience a couple three years later (1985), but this time they were mine and they were in my home, and I was smitten with them just setting on the floor of my livingroom driven by my venerable ol' Heathkit 1500A until I figured out what to do with them. They literally changed my idea of what speakers could achieve. A mind altering experience.

 

[mhardy6647]

I bought a pair of slightly scruffy (but delightfully affordable) 604B Duplexes shortly after the "audition" I described above.
Still have those, too (imagine that?!). Keep meaning to do something with them...

 

[mhardy6647]

Of course, ultimately I acquired a very lovely pair of 604E Duplexes, which initially spent some quality time in the basement on my workbench while my woodworker friend Mike Berg constructed their intended enclosures. Knowing the proclivities of our two curious felines, I immediately covered them with some towels after bringing the home from western Vermont and putting them downstairs.

Within hours of bringing them home, I went downstairs to be greeted by the following tableau.



L to R: Duplex, cat, Duplex. The cat is on the Duplexes' baskets. 😲

 

[je2a3]

I bought a pair of slightly scruffy (but delightfully affordable) 604B Duplexes shortly after the "audition" I described above.
Still have those, too (imagine that?!). Keep meaning to do something with them...

I doubt if your 604Bs are still affordable now (if one can find a pair) even if less than pristine. The folded paper suspension prevented it from going very low but was great for midrange response further aided by having the largest horn.👍😊

 

[mhardy6647]

Yup, they (the "B" morph, that is) are held in high esteem in certain circles.