Is the Infinity polydome replaceable with any IMG midrange?
- Thread starter BSEYE
- Start date
Well, after 1.5mm spacer, even tried 2mm spacer, it changes thinks a bit, but not even close getting to the original SPL. I am not a pro at REW, but got UMK1 and did measure the driver and also the speaker, even with increased L-Pad midrange, its still behind the other drivers, which makes the singer feel like its behind the scene.
Here is a pic of where I put the spacer, if anyone wanna try, might get a better results.
Spacer size is 93mm inner diameter to 98mm outside diameter with thickness of 1.5mm, which is 0.060"
Just put the spacer there, when you put the upper plate just match the holes and bolts will fix it where it must stay.
Anyone any more suggestions, could it be me that just not doing anything right ? I dont know what to think anymore, I see comments on ebay with 30+ happy people from those domes and many people in Europe selling their speakers with the new polydomes, or just polydomes with replaced domes, saying they do sound like new.
Here is a pic of where I put the spacer, if anyone wanna try, might get a better results.
Spacer size is 93mm inner diameter to 98mm outside diameter with thickness of 1.5mm, which is 0.060"
Just put the spacer there, when you put the upper plate just match the holes and bolts will fix it where it must stay.
Anyone any more suggestions, could it be me that just not doing anything right ? I dont know what to think anymore, I see comments on ebay with 30+ happy people from those domes and many people in Europe selling their speakers with the new polydomes, or just polydomes with replaced domes, saying they do sound like new.
Ah, yeah you are kind of right, I've never heard the original sound when the speakers were new and of course I do not posses such driver. But it just can't be this huge difference in SPL between the drivers. Are you suggestion that it actually was such dramatic difference ?
When I rebuild polydomes I get them within 1-2db of original. I was fortunate enough to acquire a fully intact original a few years ago and measure output near field. The tolerances on these drivers is pretty tight and any misalignment in any direction will throw off the output. There are a couple things that will reduce output dramatically. As you’ve discovered, not having the voice coil located in the correct vertical position relative to the magnet gap. If the the voice coil is not fully glued to the dome it will cause issues as well as the voice coil not being fully perpendicular to the face of the magnet structure. Voice coil tilt will usually cause more drop off at either end of the response range. Too much tilt will cause voice coil rub which will also greatly reduce output.
That's the best I could do. Turned my dinning table in workshop for 2 days, a day per driver. Tried every possible position (perfectly centered at the dot, little bit behind, little bit upfront) to attach them and ran a test with a simple measure without mounting them to the box, I am pretty much sure they are perfectly fit, no misalignment, no rubbing and is excellently glued. It does not sound bad, well at least at first gives good impression, but after few days of listening, you realize that its still little bit behind, it might be 2 or 3 db, have no idea, but it feels behind in the upper end, like 2-3 khz. Increasing the L-Pads of the mids barely does anything, which gives me the feeling that the material is too thick to pass those frequencies. I am giving up and gonna try to sell the speakers. I have moved them to little bit older equipment and lower level cables and it sound better, it might be that, the higher level equipment points out where the problems of the speaker are. Those measurements are made by my higher tier equipment, dont have the nerve to measure at where they are now attached, it might reveal something else and I just cant do it anymore. To confirm for future readers this are the polypropylene domes from Germany.
@seifreit Your result just 1-2db of original is outstanding it should be better than millers repair. I wish you were somewhere in europe. You should consider doing a video guide, it will help lot of people.
En este momento no estoy seguro de qué modelo específico de altavoces está reemplazando a los Polydomes en mi Kappa 8, pero creo que son estos Monacor que, aunque son de 8 ohmios, suenan de maravilla.
https://www.costruireaudio.com/PDF/MONACOR/SPH/pdf_monacor_SPH-102KEP_1.pdf
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Suenan así.
IMG_4969.MOV
https://www.costruireaudio.com/PDF/MONACOR/SPH/pdf_monacor_SPH-102KEP_1.pdf
MONACOR SPH-102KEP - 4″ Mid-range 8Ω
Technical parameters and comparison of the MONACOR SPH-102KEP 4″ Mid-range 8Ω · Resonance frequency 95Hz · Power handling 120W · Sensitivity 89dB · Xmax 1mm
loudspeakerdatabase.com
IMG_4969.MOV
I've already said it's an 8-ohm speaker. The claim that a 4-ohm speaker is needed is false, or at least not entirely correct. I can assure you I didn't modify the hole at all, and as you can see in the video, it looks fine. If you say it won't work, tell me what sounds wrong with it in the video. If you'd like me to play a specific track, I can, no problem, and you can tell me what's wrong. I understand that if you say it won't work, it's because it sounds bad.
swechsler
Frog Whisperer
An 8Ω speaker will work, in that it will produce sound (any speaker that fits in the hole will work), but the crossover frequencies won't be correct. That's just physics. As far as how it sounds, it's impossible to tell that by watching a video, no matter how well the video is recorded.
Esta situación es similar a la de un altavoz de 4 ohmios distinto al original, y también a la de un altavoz original reparado con un diafragma diferente. Cambiar la frecuencia de cruce no implica necesariamente que el altavoz deje de funcionar correctamente. He visto muchos filtros Infinity con valores de componentes diferentes a los del esquema original, y nadie se ha quejado.
En mi caso, con los Kappa 8 funcionando en modo activo con un amplificador de potencia individual para cada canal y un filtro divisor de frecuencias activo donde puedo programar la frecuencia de cruce y el nivel de señal a mi gusto, ese problema no existe. En cualquier caso, con su filtro divisor de frecuencias pasivas y el altavoz que menciona, suenan de maravilla.
En mi caso, con los Kappa 8 funcionando en modo activo con un amplificador de potencia individual para cada canal y un filtro divisor de frecuencias activo donde puedo programar la frecuencia de cruce y el nivel de señal a mi gusto, ese problema no existe. En cualquier caso, con su filtro divisor de frecuencias pasivas y el altavoz que menciona, suenan de maravilla.
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swechsler
Frog Whisperer
No, it's not the same. We are all aware that a slightly different driver or diaphragm won't match the impedance curve of the original exactly. But it will be a lot closer than if you change the nominal impedance from 4Ω to 8Ω. If you change the high pass crossover frequency of the upper midrange, without a corresponding change to the low pass crossover frequency of the lower midrange, there will be either a gap or a peak in the frequencies that both drivers are reproducing, that wasn't included in the original design, and cannot be compensated with the L-pads.carlinos said:
1. Just because nobody complained doesn't mean it sounds rightcarlinos said:
2. It's been documented here many times that Infinity has changed crossover designs in the middle of a production cycle. That doesn't make either design right or wrong.
@carlinos indicates in his post that his Kappas are active-crossovered and multi-amped, which can facilitate integrating a replacement driver of a different type successfully.
Carlinos, you might want to consider translating your posts
Disculpa, veo la página en español y cuando respondo uso un traductor y pego el texto traducido, que lo convierte automáticamente al español. ¿Ves este mensaje en español?@carlinos indica en su publicación que sus Kappas tienen crossover activo y amplificación múltiple, lo que puede facilitar la integración exitosa de un controlador de reemplazo de un tipo diferente.
Carlinos, tal vez deberías considerar traducir tus publicaciones.
swechsler
Frog Whisperer
FWIW, when I get email alerts about your responses, they usually show in English (that's how I got the translation for my last response, although your response above this one showed Spanish in both places) but directly here they show in Spanish. That's probably why if you mentioned active crossovers, I missed it.
Yes
Kappa 8 in passive mode with Yamaha MX-1000. They sound much better in active mode with the 4 power stages.
IMG_4089.MOV
IMG_4089.MOV
I was replacing my polydomes with the bare domes from Europe, and I noticed this post (as well as various others) suggesting a spacer was required to obtain the original SPL.
Since one of my polydomes was still intact enough to measure where the voice coil sits vertically relative to the frame, I was able to compare it against the equivalent measurement of the new replacement dome.
Original:
New replacement:
Hard to capture a good pic, but hopefully the difference is easily observed by the naked eye.
As it turns out, the new polydome voice coil position is 0.080" higher than the original.
So - at least according to this observation - spacing the replacement voice coil up another 0.060" would position the voice coil, relative to the magnet, 0.140" higher than the original!
Does that seem right?
Of the assumptions being made here, the key assumption is that my worn out old polydome is not sagging from where it should be. Given the breakdown of the plastic material, however, I wonder if that assumption is correct?
I'll note that I installed the replacements (after many trials and errors, using the original voice coils on the new domes perfectly centered and without bending is one of the most difficult things I've ever done to repair a speaker, in hindsight I should have ordered them with the voice coils already installed ... next time ...) without spacers, and it sounds well and balanced to my ears at the factory pot positions for both.
I did observe while centering the new domes with a 1kHz test tone that the sensitivity significantly improves when they are centered, compared to being out-of-center. Maybe an obvious point to make, but also, looking for ways to explain the reports of low output above and in other threads I've read.
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