Title should say "Help updating......"
Hello All,
Way back in 2008 my buddy Zilch (may he rest in peace) designed an Econowave variant speaker for me using a pair of vintage Heath AS-10 cabinets I'd picked up. I've been wondering lately if the cabinet volume is optimum for the JBL 127-H1 woofers and BMS4555 compression drivers that use JBL PT-D95HF waveguides. Am certain the non-flush woofer and waveguide mounting is not optimal. Plus the cabinet baffles have a lip around them that is causing diffraction.
I know nothing about DIY cabinet design other than what I've learned today by reading in this forum. Any thoughts and help on designing new cabinets with stiff bracing would be greatly appreciated.
Regards,
bmwr75
Hello All,
Way back in 2008 my buddy Zilch (may he rest in peace) designed an Econowave variant speaker for me using a pair of vintage Heath AS-10 cabinets I'd picked up. I've been wondering lately if the cabinet volume is optimum for the JBL 127-H1 woofers and BMS4555 compression drivers that use JBL PT-D95HF waveguides. Am certain the non-flush woofer and waveguide mounting is not optimal. Plus the cabinet baffles have a lip around them that is causing diffraction.
I know nothing about DIY cabinet design other than what I've learned today by reading in this forum. Any thoughts and help on designing new cabinets with stiff bracing would be greatly appreciated.
Regards,
bmwr75
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These look great imo. I think perhaps the bass driver itself is the weakest link after 12 years the foam surround may deteriorate, while not the cabinet after 50 years. I wouldn't worry much about the lip unless you can measure the problem. Cabinets was built to last back then and the design is somewhat timeless. You could make a front grill with round corners.
Greets!
Assuming the 127H = 127H-1 since there's no official [-1] in JBL's T/S specs pdf; the so called 'optimum' is a T/S max flat alignment [net] = ~ 293.68 L/23.61 Hz Fb and a 'classic' cab alignment [net] = ~165.21 L/25 Hz Fb, so guessing from just looking at the pics that yours are technically too small in theory, but doesn't mean that combined with its tuning that it could be considered 'optimum' for its [net] volume [Vb].
Your room's acoustics and where the speakers are located combined with the sort of performance, preferred tweeter height desired determines what's 'optimum' for your app though.
Assuming the 127H = 127H-1 since there's no official [-1] in JBL's T/S specs pdf; the so called 'optimum' is a T/S max flat alignment [net] = ~ 293.68 L/23.61 Hz Fb and a 'classic' cab alignment [net] = ~165.21 L/25 Hz Fb, so guessing from just looking at the pics that yours are technically too small in theory, but doesn't mean that combined with its tuning that it could be considered 'optimum' for its [net] volume [Vb].
Your room's acoustics and where the speakers are located combined with the sort of performance, preferred tweeter height desired determines what's 'optimum' for your app though.
The internal volume of these old Heath cabinets is 1.43 ft3 or 40.5 liters. Of course the wave guide and compression driver and ports take up part of this volume, which I assume reduces the effective volume the design.
Wow! Makes me wonder if the specs I used are 'close enough' to accurate. 🙁
Figure 36 L net and it equates to a near ~1.2 Qtc sealed, so quite tiny by venting standards.
What are the vent diameters, lengths? Curious what tuning he chose.
Regardless, lacking your driver's measured specs, got to go with what we have.
Figure 36 L net and it equates to a near ~1.2 Qtc sealed, so quite tiny by venting standards.
What are the vent diameters, lengths? Curious what tuning he chose.
Regardless, lacking your driver's measured specs, got to go with what we have.
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The nice thing about the horn is much less effect from lip diffraction, so you're fine there.
If you must put a lot of work into it, make a new flush baffle and give it a nice finish that looks good with the finish on the rest of the box.
You get to 'update' without losing the beautiful box or the Zilch provenance.
If you must put a lot of work into it, make a new flush baffle and give it a nice finish that looks good with the finish on the rest of the box.
You get to 'update' without losing the beautiful box or the Zilch provenance.
Two 2" by 7" long ports.
Here is the original build thread on AK.org of you are interested.
Heath AS-10 Cabinets - Need Driver Recommendations | Audiokarma Home Audio Stereo Discussion Forums
Here is the original build thread on AK.org of you are interested.
Heath AS-10 Cabinets - Need Driver Recommendations | Audiokarma Home Audio Stereo Discussion Forums
I like the flush baffle idea. The box needs a cross brace running horizontally between the woofer and horn too. Zilch was a unique fellow. I had the pleasure of meeting him in 2009 while on my honeymoon in San Francisco.
Thanks! I made a bad assumption, the 127H-1 is a different driver and fortunately he posted its specs.
Not surprisingly the 127H is for sealed alignments.
Anyway, the 127H-1's so called 'optimum' is a T/S max flat alignment [net] = ~ 75.7 L/35 Hz Fb and a 'classic' alignment [net] = ~78.68 L/31 Hz Fb.
Not surprisingly the 127H is for sealed alignments.
Anyway, the 127H-1's so called 'optimum' is a T/S max flat alignment [net] = ~ 75.7 L/35 Hz Fb and a 'classic' alignment [net] = ~78.68 L/31 Hz Fb.
Michael Chua measured the JBL 127H1 HERE!.
Here's his measured TS results ( they seem to be a bit more realistic than those that Zilch had posted ).
Michael's :
Zilch's :
My inclination would be to simply build a 75 Litre test box ( ported/tuned with the ability to seal the ports ) to see which tuning sort I might prefer.
Michael has posted some suggested box tunings ( for 75 Litres ).
One should be able to design a 2.7 cu' floor stander that sets the horn at listening level .
@BmWr75, are you going to build the boxes yourself ( or hire someone ) ??
🙂
Here's his measured TS results ( they seem to be a bit more realistic than those that Zilch had posted ).
Michael's :
Zilch's :
My inclination would be to simply build a 75 Litre test box ( ported/tuned with the ability to seal the ports ) to see which tuning sort I might prefer.
Michael has posted some suggested box tunings ( for 75 Litres ).
One should be able to design a 2.7 cu' floor stander that sets the horn at listening level .
@BmWr75, are you going to build the boxes yourself ( or hire someone ) ??
🙂
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I'd have to hire someone to build the cabinets or find an available flat pack I could assemble that is the right size. Don't have all the tools or skills required to cut one out sheets of MDF or baltic birch plywood.
How about changing the bass driver to something that fits the cabinet better? 70l for that 8” foam surround doesn’t seem right. Is that driver so good it’s worth refoam? Doesn’t look very pro. Cabinet and HF looks way higher quality?
Thanks! I did a fairly 'deep' search and found no other mention of this driver except ebay, etc., used sales/reconing and lots of ads of totally unrelated products, services, so combined with other recent searches being similar even when I know they're out there, guess Google is becoming somewhat worthless, so....... any other search engines [still] worth using?
JBL used the 127H-1 woofer in some well respected Consumer speakers ( L80t, XPL160a ) and at least one studio monitor ( the 4410 ), so no, I wouldn't be looking to junk it out of hand.
OTOH, JBL never crossed the 127h higher than 800hz due to always pairing it with a 5" midranger . It's top octaves might not be as smooth as one assumes ( or wishes for ).
JBL also used this woofer in cabinets as small as 1.5 cu' ( 4410 ) to as large as 2.3 cu' ( L80t ).
It's entirely possible that exacerbating///triggering the initial complaint ( of needing more bass ) is a network that failed to include enough builtin BSC .
Maybe BmWr75 can enlighten us to the network that's in present use and what the values are of its passive/component parts ( assuming that it's not biamped ).
🙂
PS; One idea is to keep the original cabinet in play since it looks nice and alreadt exists.
- Simply enlarge it ( add as much as 1 cu' of volume ).
- This could be done by cutting out the bottom and adding///making-up the necessary volume with some of the "dead space" that I see in the current speaker stand.
- If necessary, make a new custom speaker stand that has the needed space and dimensions.
One more time; Micheal Chua's 127H-1 measured specs' so called 'optimum' is a T/S max flat alignment [net] = ~ 166.75 L/27.89 Hz Fb and a 'classic' alignment [net] = ~154 L/25.57 Hz Fb.
There was never a cross over developed for this speaker. Zilch passed away before he got around to it. He and I are the only two people he was aware of ever paired this woofer, compression driver and waveguide in about a 1.4 ft3 (40.5 liter) ported cabinet. I used an active crossover at 1.8 kHz and biamped them. I have no plans to scrap the woofers. Am going to refoam them soon and keep using them in this speaker cabinet or a new one.
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