help with driver sensitivity matching

Mr. Sharpe · May 2022

I’m rebuilding some old speakers and may end up needing new midranges. The ones I need however have a 96db rating and the original speakers were only rated at 90. I know I should know how to do that part by now but I’ve always bought fully built crossovers so I’m not we’ll educated. These speakers were cheap and only had two caps and I prefer to only spend money on two replacements. I need help with what value resistor or whatever it is I need to make the midrange match the woofer and tweeter and I’ll be good. Many thanks in advance!!!

Honestly I wouldn’t be surprised if this comes back that the drivers will all even out regardless of how sensitive they are lol

Mr. Sharpe · May 2022

Actually after reading somethings online I’m hoping the original mids still work, that would be easiest. I do have to replace the tweeters bc the plastic is busted around the edges. The speakers sat in a house that was ruined by Michael and there has been such an absurd amount of moisture that the cabinets are completely ruined and useless. The speakers were much special, Yamaha ns-a635. From what I remember sounded alright. I think it’s be worth at least using the woofers in a small project and the not so special crossover caps. I’ve got the fever and need to do something lol

SeleniumFalcon · May 2022

It looks like the tweeters and drivers are available from Ebay.

Mr. Sharpe · May 2022

Ok I’m sorry.i know they’re all on eBay. I didn’t mention that if the original mids were either out I didn’t want to use the same ones. The 96db mid is 8ohms but there’s a 4ohm version with a 92db rating so I may just use it coupled with a 4ohm resistor. I’ll do some more research as well.

SeleniumFalcon · May 2022

Usually, the tweeter is more efficient than the mid range driver, so the tweeter's level is reduced with a series resistor.

mhardy6647 · May 2022

Mr. Sharpe wrote: »

Actually after reading somethings online I’m hoping the original mids still work, that would be easiest. I do have to replace the tweeters bc the plastic is busted around the edges. The speakers sat in a house that was ruined by Michael and there has been such an absurd amount of moisture that the cabinets are completely ruined and useless. The speakers were much special, Yamaha ns-a635. From what I remember sounded alright. I think it’s be worth at least using the woofers in a small project and the not so special crossover caps. I’ve got the fever and need to do something lol

Unless they have some sentimental value, they're not really worth the effort of rebuilding, IMO (and FWIW). A pair passed through here some years back -- they are as bare bones & low end as a three way loudspeaker can be. Capacitor only XOs on the MR and HF drivers, as I recall, and very basic cone drivers.

Radio Shack sold their own version of these, too, for a while (and FWIW).
Sold as "Optimus ST-S100".

source: https://www.radioshackcatalogs.com/flipbook/1996_radioshack_catalog.html

Mr. Sharpe · May 2022

Awesome, I’ll look at the drivers some more.

Oh wow that’s cool, I didn’t know that existed. I know they’re bare bones but now that I have the woofers (at least)it’s hard to just throw them away:-/ I may end up trying to find a three way crossover or do something cheap, maybe stick with the same 6db octave and different mid and tweeter and see what happens. I don’t plan on putting a lot into them.

mhardy6647 · May 2022

In terms of matching sensitivities, the easy way to do it is using a combination of series and parallel resistors called an L-pad. The nice thing about an L-pad is that it can attenuate the level of signal delivered to a driver (like a volume control) while maintaining a constant impedance (so that the crossover still functions as intended).
An L-pad consists of two resistances: one in series with one connection to the driver and the other in parallel across the driver's connections. There are two flavors of L-pads: fixed and adjustable. The latter is nice in that the level of the "padded" driver can be dialed in (literally), but the quality of the variable L-pad isn't up to that of a fixed L-pad. The problem of course with a fixed L-pad is that it is fixed at one level.

Here's an L-pad calculator to make a fixed L-pad at whatever level of attenuation is desired:
http://www.sengpielaudio.com/calculator-Lpad.htm There's also a table of some common values.
So, for example, a fixed 6 dB attenuation (i.e., "-6 dB") L-pad for an 8 ohm driver can be made with a series resistance of just about exactly 4 ohms as the series resistance and 8 ohms as the parallel resistance.

Here's a "serving suggestion" for a variable L-pad used to attenuate the output of a "supertweeter", for example.

One good trick is to use a variable L-pad to decide how much attenuation is required, then measure the series and parallel resistances of the variable L-pad. The variable pad can then be replaced with two fixed resistors of high quality to provide the desired level of attenuation.

EDIT: oh, here's a typical 8 ohm "mono" variable L-pad, such as one might use to attenuate the output of a tweeter to match it to a woofer in a two-way system.
https://www.parts-express.com/L-Pad-15W-Mono-3-8-Shaft-8-Ohm-260-248

Hope this is helpful!

mhardy6647 · May 2022

Here's a rather nice Fostex "supertweeter" hooked up, via an L-pad and a first-order crossover (one simple capacitor, that silver cylinder behind the tweeter) to an Altec Duplex loudspeaker for testing purposes

Mr. Sharpe · May 2022

mhardy6647 wrote: »

In terms of matching sensitivities, the easy way to do it is using a combination of series and parallel resistors called an L-pad. The nice thing about an L-pad is that it can attenuate the level of signal delivered to a driver (like a volume control) while maintaining a constant impedance (so that the crossover still functions as intended).
An L-pad consists of two resistances: one in series with one connection to the driver and the other in parallel across the driver's connections. There are two flavors of L-pads: fixed and adjustable. The latter is nice in that the level of the "padded" driver can be dialed in (literally), but the quality of the variable L-pad isn't up to that of a fixed L-pad. The problem of course with a fixed L-pad is that it is fixed at one level.

Here's an L-pad calculator to make a fixed L-pad at whatever level of attenuation is desired:
http://www.sengpielaudio.com/calculator-Lpad.htm There's also a table of some common values.
So, for example, a fixed 6 dB attenuation (i.e., "-6 dB") L-pad for an 8 ohm driver can be made with a series resistance of just about exactly 4 ohms as the series resistance and 8 ohms as the parallel resistance.

Here's a "serving suggestion" for a variable L-pad used to attenuate the output of a "supertweeter", for example.

One good trick is to use a variable L-pad to decide how much attenuation is required, then measure the series and parallel resistances of the variable L-pad. The variable pad can then be replaced with two fixed resistors of high quality to provide the desired level of attenuation.

EDIT: oh, here's a typical 8 ohm "mono" variable L-pad, such as one might use to attenuate the output of a tweeter to match it to a woofer in a two-way system.
https://www.parts-express.com/L-Pad-15W-Mono-3-8-Shaft-8-Ohm-260-248

Hope this is helpful!

That’s very helpful! I was actually thinking earlier of getting the 96db mid and a highly efficient tweeter and using l-pads for both but now I see that would be ridiculous and a waste lol. That’s really really helpful. I can do this with both the midrange and tweeter right?

mhardy6647 wrote: »

Here's a rather nice Fostex "supertweeter" hooked up, via an L-pad and a first-order crossover (one simple capacitor, that silver cylinder behind the tweeter) to an Altec Duplex loudspeaker for testing purposes

This is great, I can see this happening at my house as well:)

Mr. Sharpe · May 2022

I just got this crazy idea of finding two more of the woofers and making floor standing speakers.
I think I’m gonna sit on this for a while before moving forward. I appreciate the replies and they’ll be remembered for when I get around to this. It’s an obsession is it not?

mhardy6647 · May 2022

1) yes, you can pad both MR and tweeter separately. The "circuits" will be identical. Each will be connected in parallel to the woofer with the XO capacitor for each driver in the circuit as shown above.

2) as soon as you decide you're going to spend any significant amount of money -- I'd strongly encourage you to start with a clean sheet of paper and design, resource, and build something worth the effort (and expense)!

The Yamaha components aren't worth the effort, even if you have them in hand.
Parts Express has an excellent fourm and list of projects aimed at all budgets and skillsets. Spend some time looking at DIY options there and plot a new course. Again, just my opinions, and, as (unsolicited!) free advice, worth what it costs you

-- but I would encourage you to think more broadly, deeply, and strategically before spending much $ (or time).

https://techtalk.parts-express.com/forum/tech-talk-forum
http://projectgallery.parts-express.com/

The nice thing about PE is they offer drivers from very inexpensive but decent to high quality, excellent (and, in some cases, expensive) drivers. They also often have numerous buyouts and specials, and sometimes their customers even "publish" designs/projects based on their 'specials'. Plus, of course, they have a bevy of kits, as well.

... or, you could consider aiming a little higher up the food chain.

https://www.madisoundspeakerstore.com/

Mr. Sharpe · May 2022

Oh it won’t be much money😂 I used to have a tech talk account but sometimes I felt like I got one peoples nerves a little when asking questions lol. I also know Parts very well, I’ve purchased from them many times and know they have good products, same as Madisound, just haven’t bought much from them.

Thank you for the help with using the l-pads, that’ll come in handy! I never knew you could use them to figure out what resistor to use when mixing driver sensitivity:)

help with driver sensitivity matching

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