polk 7 diy clone

jestwaitn
jestwaitn Posts: 33
in Vintage Speakers
i have a pair of polk 7, iirc it is the 7b.

they are wall-mounted about 6' off the floor, tweeters on the bottom, box slightly tilted toward the floor. the speakers are unmodified. unbelievable sound.

i want to clone them with 'off the shelf' components and make the enclosure less deep (slimmer), taller and wider.

anyone have any ideas on this?

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Comments

  • mhardy6647
    mhardy6647 Posts: 33,791
    edited December 2020
    Yes.
    "Why?!?"


    What do you wish to accomplish? What deficiencies are you interested in correcting?
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  • mhardy6647
    mhardy6647 Posts: 33,791
    edited December 2020
    now, if you want to try a "slimmer, taller and wider" variant, why not hunt down a pair of the vintage Radio Shack Realistic "Optimus 27" from 1980?

    hjeqg3b4r6t6.png
    source: https://www.radioshackcatalogs.com/flipbook/1980_radioshack_catalog.html
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  • xschop
    xschop Posts: 5,000
    edited December 2020
    IIRC, you should try to leave the baffle width the same for baffle step compensation of the original crossover. Or you can buy mhardy's Optimus 27's. :)
    Don't take experimental gene therapies from known eugenicists.
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  • mhardy6647
    mhardy6647 Posts: 33,791
    Non Optimus 27s here -- I would be curious to hear a pair (never have).
    I do have a pair of one of the other handful of PR-loaded loudspeakers that R/S sold back when PRs were a thing -- the lattice-grilled :p Nova 10, replete with cone tweeters. They're actually rather pleasant (which was not the case of many of R/S's loudspeaker system offerings over the years).

    8abqdcsmev6d.png
    https://www.radioshackcatalogs.com/flipbook/1981_radioshack_catalog.html

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  • motorstereo
    motorstereo Posts: 2,133
    Taller, wider, and slimmer..........sounds like a pair of Boston Acoustic ba400's is just what you're looking for.
    ndhld74b2bax.png

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  • mhardy6647
    mhardy6647 Posts: 33,791
    nice suggestion and a dandy choice! Forgot about those (as most of my BA experience is at the low-er end of their classic line).
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  • la2vegas
    la2vegas Posts: 657
    motorstereo wrote: »
    Taller, wider, and slimmer..........sounds like a pair of Boston Acoustic ba400's is just what you're looking for.
    ndhld74b2bax.png

    BA fanboy indeed. I've got a pair of A40, 2 pair of A100 and a pair of A150. Been looking for a pair of A400's but they don't come up for sale too often.
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  • jestwaitn
    jestwaitn Posts: 33
    wow. thanks. many great ideas. uncertain if i heard the a400 back 'in the day'. it is a little longer than what i had in mind. these will be off the floor. shallower speaker disappears in the wall better than the 7b.

    and looking for a diy solution.

    not really any deficiencies in these 7b speakers. but they are 35 years old & i want to see if it is possible to clone (approximate) this sound with a similar approach. idk???
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  • Emlyn
    Emlyn Posts: 4,489
    edited December 2020
    Designing a passive radiator based speaker with different cabinet dimensions to approximate the Monitor 7s is not a trivial endeavor. But, it could make for an interesting hobby. There's really nothing wrong with the midwoofers and passive radiators in the Monitor 7s despite being relatively old.

    Out of curiosity, why are the speakers mounted on the wall upside down? I remember seeing some wall mounted in college bars back in the 1980s.
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  • mhardy6647
    mhardy6647 Posts: 33,791
    edited December 2020
    Well, if the internal volume of the cabinet is the same as the Monitor 7, the requirement for the PR (moving mass, first and foremost -- at least as I understand it) will be the same to get the same box tuning as the Monitor 7 in a different "form factor".

    PR-loaded enclosures aren't particularly hard to tune, especially if one has the measurement tools (which is a pretty low bar nowadays) and doesn't mind taking an empirical (trial and error success) approach.

    As an aside -- since it came up ;) -- some of the smaller BAs also had thin-line cabinets; e.g., the A70 (albeit sans PR). The original A70, with SEAS tweeters, is a fine sounding little two-way loudspeaker. Even the later ones, with BA's own (?) dome tweeter, sound pretty good, too.

    39110162542_f7d964142f_c.jpgP1010012 (1) by Mark Hardy, on Flickr

    24766146181_fa0e59f4a2_b.jpg081 by Mark Hardy, on Flickr
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  • pitdogg2
    pitdogg2 Posts: 25,437
    Restored a pair of both Boston a150's and a400. All needed refoamed and one a400 needed a tweeter. The tweeter (for me anyway) was none too easy to source. Those cabinets were stuffed to the gills with polyfil. Both were very nice sets of speakers when finished.
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  • jestwaitn
    jestwaitn Posts: 33
    again, thanks for the wonderful ideas!

    the 7b's are mounted 'top-down' since this puts the tweeter axis in closer alignment with the woofer axis on the vertical.

    of course a pr can always be mounted on the rear of the cabinet, as with the amt4.

    idk what type of damping material the 7b has inside. so many diyers use/recommend felt on the cabinet walls and some amount of poly fill. and not too many diyers seem to use the pr tuning; tl or br are more common if not sealed.
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  • F1nut
    F1nut Posts: 50,542
    Who has the decoder ring?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • motorstereo
    motorstereo Posts: 2,133
    la2vegas wrote: »
    motorstereo wrote: »
    Taller, wider, and slimmer..........sounds like a pair of Boston Acoustic ba400's is just what you're looking for.
    ndhld74b2bax.png

    BA fanboy indeed. I've got a pair of A40, 2 pair of A100 and a pair of A150. Been looking for a pair of A400's but they don't come up for sale too often.

    I had a pair of recapped and refoamed A400's stay with me for several years. They were very nice sounding speakers and it took a pair of the larger ADS speakers for me to part with them.
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  • la2vegas
    la2vegas Posts: 657
    motorstereo wrote: »
    la2vegas wrote: »
    motorstereo wrote: »
    Taller, wider, and slimmer..........sounds like a pair of Boston Acoustic ba400's is just what you're looking for.
    ndhld74b2bax.png

    BA fanboy indeed. I've got a pair of A40, 2 pair of A100 and a pair of A150. Been looking for a pair of A400's but they don't come up for sale too often.

    I had a pair of recapped and refoamed A400's stay with me for several years. They were very nice sounding speakers and it took a pair of the larger ADS speakers for me to part with them.

    Which ADS model dethroned the A400'd?
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  • motorstereo
    motorstereo Posts: 2,133
    ^^^^A pair of 1230's sent them to another home. But the 1230's didn't stay here long as a pair of 1530's arrived and sent them away.
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  • lavane
    lavane Posts: 8
    mhardy6647 wrote: »
    now, if you want to try a "slimmer, taller and wider" variant, why not hunt down a pair of the vintage Radio Shack Realistic "Optimus 27" from 1980?

    hjeqg3b4r6t6.png
    source: https://www.radioshackcatalogs.com/flipbook/1980_radioshack_catalog.html

    A friend bought a pair of the Optimus 27's recently on the cheap. He gave them to me to try out. I have to say, they aren't horrible.
    They image pretty well. And they can get dang loud when pushed. The dome tweeter isn't harsh, and the midrange is nice. At a low volume the bass is a bit tight, but if you push them a bit the bass fills out. They are an odd looking speaker for sure, with that thin cabinet. They sounded best about 4" from the wall. The only thing I really didn't like about them was the fuzzy terry cloth like grills.
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