Two weird questions on using speaker replacements

[carlmart]

1) What do I get if I try to use a woofer designed for a vented box into a closed box? Is there anything I can do to use a driver with lower Qts in a closed box?

2) Besides the obvious crossover parts mods, anything else to worry about using a 4 ohm speaker in a former 8 ohm design?

3) Why are there so few, just a couple, 8" mid woofers designed for closed box boxes?

 

[Count Dacula]

It's hard to get answers on Homebrew speakers. I've tried, but I don't think people are helpful, while AI is very receptive. I'm shocked of how comprehensive, personal and affirmative it is. I explained a bunch of the Q&A material to my wife, it was a nice surprise.

My guess is a Bass Reflex speaker is ok in a Sealed box, but not the other way around. Some of us had a life before ASR.

 

[Duke]

1) What do I get if I try to use a woofer designed for a vented box into a closed box?

You'd get weak bass response. The bass would start rolling off fairly high up, and would do so rather gradually.

Is there anything I can do to use a driver with lower Qts in a closed box?

You could equalize it.

2) Besides the obvious crossover parts mods, anything else to worry about using a 4 ohm speaker in a former 8 ohm design?

The specifics matter of course, but there's a pretty good chance of the voltage sensitivity being higher for the 4-ohm driver, which in general means that it would be louder than the original 8-ohm driver. And if there is any EQ specific to the original 8-ohm driver built into the crossover, it's unlikely that the same EQ will be what your replacement 4-ohm driver calls for, even if you correct the parts values for the new impedance.

3) Why are there so few, just a couple, 8" mid woofers designed for closed box boxes?

Presumably because vented box woofers are what the people who buy woofers for DIY are buying the most of.

 

[kemmler3D]

It's hard to get answers on Homebrew speakers. I've tried, but I don't think people are helpful, while AI is very receptive. I'm shocked of how comprehensive, personal and affirmative it is. I explained a bunch of the Q&A material to my wife, it was a nice surprise.

My guess is a Bass Reflex speaker is ok in a Sealed box, but not the other way around. Some of us had a life before ASR.

DIYAudio is a much better forum for discussing speaker building if you find ASR unhelpful. There is a little more nonsense / woo, but also almost everyone there knows something about building speakers in practice. It is naturally a measurement-driven community also, so I think it's worthwhile.

 

[carlmart]

It's bad luck and a little of laziness from me that got me into this problem I am now.

These speaker were designed and built by a genius friend of mine in Argentina who practically hand made his speakers, which were just two models, all closed boxes. A 3-way and a two way. I had both and stayed with the simpler two way. All drivers were built following his designs and severe instructions. Every wire of them. They were so precisely built that a the crossover was single order: just a series cap on the tweeter (with resistors to adjust the level) and a single inductor on the mid-woofer.

As one of my drivers had survived two days of amplifier DC, though with slightly damaged VC, we had been planning to replace both with a new pair of 8" units, which he had to build a new quantity of. The problem is he passed away, and I was left with a speaker that is damaged and few amplifiers can stand the electrical demands of the damaged voice coil, which must have lowered in impedance and resistance. It measures 6 ohms on a multimeter, but I am certain it's lower. A very difficult load.

As finding a similar VC coil for replacement is absolutely impossible, and I couldn't find a single replacement coil at his home studio, I will have to look for new drivers. That's why I asked about using woofers not designed for closed boxes.

I've already seen some woofers that can work on both boxes, always poorer in bass in the closed box version, usually one-octave less. Unfortunately I live in Brazil, so I can't simply order different drivers to try from Madisound or similar suppliers, and see if someone suits me better. Speaker suppliers are scarcer and scarcer every day. So my options are fewer and fewer.

Some from SB and from Dayton seem to be interesting on paper, but to get them here to actually try them is tricky and VERY expensive. Weight and customs taxes are a problem. Of course I should replace both drivers, so shipping internationally is costly.

Besides all that I am not a speaker designer, and I can't find someone to properly repairing the VCs. Someone I can trust. At most I could measure D & L, and wire resistance. VC weight and other specs I can't without destroying the un-damaged driver.

If anyone can think of another option, please say so.

 

[kemmler3D]

It's bad luck and a little of laziness from me that got me into this problem I am now.

These speaker were designed and built by a genius friend of mine in Argentina who practically hand made his speakers, which were just two models, all closed boxes. A 3-way and a two way. I had both and stayed with the simpler two way. All drivers were built following his designs and severe instructions. Every wire of them. They were so precisely built that a the crossover was single order: just a series cap on the tweeter (with resistors to adjust the level) and a single inductor on the mid-woofer.

As one of my drivers had survived two days of amplifier DC, though with slightly damaged VC, we had been planning to replace both with a new pair of 8" units, which he had to build a new quantity of. The problem is he passed away, and I was left with a speaker that is damaged and few amplifiers can stand the electrical demands of the damaged voice coil, which must have lowered in impedance and resistance. It measures 6 ohms on a multimeter, but I am certain it's lower. A very difficult load.

As finding a similar VC coil for replacement is absolutely impossible, and I couldn't find a single replacement coil at his home studio, I will have to look for new drivers. That's why I asked about using woofers not designed for closed boxes.

I've already seen some woofers that can work on both boxes, always poorer in bass in the closed box version, usually one-octave less. Unfortunately I live in Brazil, so I can't simply order different drivers to try from Madisound or similar suppliers, and see if someone suits me better. Speaker suppliers are scarcer and scarcer every day. So my options are fewer and fewer.

Some from SB and from Dayton seem to be interesting on paper, but to get them here to actually try them is tricky and VERY expensive. Weight and customs taxes are a problem. Of course I should replace both drivers, so shipping internationally is costly.

Besides all that I am not a speaker designer, and I can't find someone to properly repairing the VCs. Someone I can trust. At most I could measure D & L, and wire resistance. VC weight and other specs I can't without destroying the un-damaged driver.

If anyone can think of another option, please say so.

This is beyond my skills but I think if you can get a DATS you can measure more electrical properties (T/S parameters) of the good driver, and then search for a close replacement using more data points. I think that is your best hope of not having to redesign the speaker entirely.

 

[carlmart]

The DATS is a VERY EXPENSIVE TOOL!!! Not sure it would solve my problem anyway, as I wouldn't know how to use it. And then track among existing speakers to get to a likely replacement would be almost impossible to achieve.
A better bet might be finding a good 8" mid-woofer, get two of them and build at least a new xover.
Still better would be to find a replacement for the VC coils, but I wonder if that would be possible, as they were designed and rolled specifically by my friend for these 8" drivers.

 

[10PSPMemSticksForMiku2007]

You don't need DATS for this. There is a much cheaper, good enough way to measure the parameters. Please read this and I hope it is helpful to select a replacement woofer. Otherwise, you may be right, it may be necessary to make a new crossover.

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