Hi I am planning on installing Integral Audio Soundstage + Sub in my CM S, when the system becomes available later this year, but just got hold of a HERTZ HDP5 and Mille speakers, and would like to know if this equipment + IA Sub could deliver as good SQ as getting the whole system from IA.

 

Excellent question. It's an apples and oranges comparison. There are two key elements of the complete system. There are the components - the individual pieces that make up the system, and then there is the system design - how are those components designed to work together and with the listening "room".

Every vehicle is different – the location, angle, distance of each speaker from each other and from the listener – and these are all CRITICAL factors in the crossover design (the crossovers divide the frequencies up among the different speakers. For anything beyond entry-level sound, they are the most important part of the entire system). The only way to properly account for this is to measure the drivers in the vehicle, and then build the crossovers off that data. That’s what we do. Hertz doesn’t, and neither does anyone else for that matter. It isn’t an issue of component quality – the Hertz are a fine product – it’s an issue of specificity. It’s like a tailored suit vs. something that is one-size-fits-all.

I happened to be working on the attached image for some marketing material, and it's relevant here. This is related to subwoofer-design, but it's a great illustration of why you need to design for the actual vehicle. You might be familiar with the concept of “cabin gain”, the phenomenon wherein low frequencies are boosted in a room or vehicle cabin. Again, every vehicle is different – the dimensions of the vehicle, volume, and other factors determine the shape of that curve (the transfer function) - how much, how fast, and how evenly are frequencies boosted.

Take a look at the attached image. The red curve is the transfer function of a sedan, the blue curve is a hatchback. They are dramatically different - 16dB at 60Hz! They also have very different slopes - vehicle "B" cabin gain rises faster, and there is a null/hump at 60/85Hz that have to be dealt with. In short, a subwoofer that sounds good in vehicle "A" is NOT going to sound good in vehicle "B".

Now look at the other curves. The yellow curve is the target response for vehicle "A" (the inverse of the transfer function) - if you add the blue curve (transfer function) and the yellow curve (target response) you the green line: flat magnitude response. Now look at the purple curve. This is the actual response of the subwoofer that we designed for this vehicle [this is a subwoofer, so you are only interested in the area below 100Hz. Above about 80Hz the subwoofer is rolled off by an active crossover]. We're off by a mere 3dB or less from 20-35Hz, and everything else is spot on. FWIW, 3dB is the smallest difference that any human can hear at those levels, and most wouldn't even be able to do that. There's no equalization there, that's just the natural response. How'd we do that? Match Qtc and frequency response to the target vehicle response by altering the motor, suspension, etc, of the driver, and the volume of the enclosure to get the desired response.

 

Thanks for the information Kevin, I understand your point, I guess that is why the SQ of OEM equipment like Acura ELS, Burmester of Porsche, etc are getting so good. Please advice if there could be a benefit from replacing with better unit from Sony , Kenwood, etc? Or is this also unnecessary to get highest SQ, if installing IA Soundstage+SUB ?

 

Largely, yes. The issue for the OEM's and other OE suppliers is that they still don't seem to have a handle on measurement. They have massive resources - seven/eight figure research budgets and up, and no shortage of smart people - yet they still seem to get it wrong. They can build to what they measure, that's easy for them. Granted, the measurement part is extremely hard, but still. They are also hamstrung by limited unit costs - they are under pressure to keep spend on speakers, etc, under control - and all other things being equal you can't make a good speaker inexpensive.

With our systems, it's not only unnecessary, it will hurt you since our systems are designed based on measurements that include the OEM HU. If you are doing your own, is there a benefit? Yes. Is it worth the cost and trouble? Depends on your goals and what else you are doing. In general, my opinion is that it isn't necessary.

 

Great post on cabin gain. I have had that debate with Miata owners for years and everyone still thinks a sub in the trunk will just rattle your car apart. I built my sub and put it in a tiny box with a high F3 and relatively high Q and people were amazed.

The hard part is getting people to understand that a sub that goes down to 20 Hz will sound bad and waste power. The harder part is measuring what it really should be!