DIY Modified Aiwa HP-500 from Kabeer Page 2

Page from owners manual describing the planar magnetic operating principle.

Tyll's Notes
First of all, the old school audio geek in me wanted to obsessively fondle the all-metal earpieces of these fine cans. The mix of stainless, chrome, silver metal flake paint, and burnt-orange anodize finish were attractive beyond baring. My lusts welled strong with the Aiwas.

These are a fairly heavy headphone, with modest headband and earpad padding. You know how those red spaceport chairs in "2001: A Space Odyssey" looked really cool, but not very comfortable? Yeah, kinda like that. The thing is, if you had the chance to sit in a spaceport chair, you would right? Same thing with these cans; a real audio gear experience.

Which brings me to the sound: Wow, just fantastic! I really wonder how good they sounded out of the box relative to Kabeer's mods, but I've got to believe they must have been pretty good, because the sound modified is really great ... in a 1977 spaceport sort of way.

The first thing that struck me was the tremendous balance and dynamics of these headphones; everything in the mids and lows was dynamic, tight, and extended. The treble was just a little withdrawn and slow, however. I'm fine with that because I can't stand too much brightness. The highs --- and really the whole presentation of these cans --- were a little bit hard sounding, however. I'm not too sure how to describe it exactly, but you know how you can get '70s recordings that are good, but not airy and open? Typical of the recordings of the '70s in my experience, the Aiwa's had a somewhat cardboard cut-out presentation. Very good cardboard cut-outs, mind you (I had to compare them with the world class Audeze LCD-2 to get a solid read on it), but not lifelike and natural with organic depth and weight that give really top-tier audio images three dimensions. The were very, very good, but in an old school way.

Within the limits of that sort of sound quality, Kabeer's Aiwas are simply spectacular. Like most vintage planar magnetic cans, the mid-range was simply luscious. But unlike the vintage orthos I've had the pleasure of hearing, the Aiwa HP-500 had an easy and naturally potent punch that extended very tightly into the lows. It was punch that was very articulate without being piercing. That's a combination that's hard to come by. I listened to Massive Attack's "Be Thankful For What You've Got" and it got me groovin' so hard I almost put on bellbottoms and roller skates.

We've certainly found a new leader in the DIY ortho measurements race with Kabeer's Aiwa HP-500. Other than just a couple of odd notes, these are among the best full-size headphones I've measured ... DIY or commercial.

Click on graphs image to download .pdf for closer inspection.

Despite being very old and somewhat worn, the raw frequency response data shows the earpads sealing very reliably. Bass extension is simply exquisite, and response is ruler flat from 20Hz to 2kHz. An extraordinarily good result.

Kabeer mentions a peak in the treble, which is possibly seen at 10kHz. This is quite common and is likely, to some extent, to be an artifact of the application of the HRTF compensation (notice it's smaller in the raw measurements). Nonetheless, I did hear this peak in listening tests but felt it only a minor coloration. All told these were very neutral sounding cans, with only a slight tendancy to sound a bit rolled-off.

As expected from the flatness of the FR and bass extension, the top of the 30Hz square wave is very flat and wave shape is excellent. 300Hz square wave response shows a single small overshoot and good damping, but the rise time is a bit slow looking. Impulse response is a bit stunted, but has little ring and settles quickly.

I inadvertently ran the normal headphone test, so there are THD+noise results for both 90 and 100dBspl levels. Results show some troubles with handling power; and the left channel being slightly worse then the right. Not sure what's up with that.

Kabeer, old buddy, old pal, your Aiwa cans are absolutely yummy. I'm spectacularly impressed ... you've done wonderfully ... and you can happily grin at the pain of my jilted lust as I return them to their original carry case, and send them off to Wualta for their return journeys. Terrific job, mate! Well done!

Resources, such as they are, after the video!

Wikiphonia Aiwa HP-500 page ... with pix!
German site "Radiomuseum" Aiwa HP-500 page.


maverickronin's picture

The FR and square waves are great but what's up with the distortion? Is noticeable much at lower volumes or does it really ramp up with volume?

gurubhai's picture

but yet wow....
these are some fantastic measurements.
Great job, Kabeer.
And a big thanks to the 'big bad W' for arranging to get them measured.I really wanted to see these.

donunus's picture

Looking almost like an lcd2 frequency response except for the speed in rise time which may actually be good since it might compensate for the rolloff in the lower highs. WOW.

Kabeer's picture

Thanks for the measurements and great review Tyll! I do still feel they give a nice 3D bodied feel to insturments though.

As for the cable and plug. The cable is stock (cloth covered cable). The 1/4" plug is an aftermarket one I put on, it kinda matches the curvy style of the headphones.