[::CMS::]

Originally Posted by blackfire_9

Hello all,

I am planning to get a new 4-channel amplifier for myself to drive a pair each of Rainbow Soundlines. The approximate power output value that I am looking at is 100w RMS at 4 ohms per channel.

Since I am only keen on getting a class D amplifier, I have shortlisted the below 2 options:
1. Infinity Kappa Four
2. Hertz HDP4

Could the gurus here help me in making a choice? What are the typical differences in the sound signature of these two amps & also, which one can take more abuse?

Is there any specific reason that you are looking out only for a class D amp? A Class D amp is efficient than a Class AB, but a decent class AB will outperform a class D for >100Hz in SQ. You wont feel any difference b/n the above amps but a class AB vs class D will be noticeable.

[navin]

Originally Posted by Trust_In_Thrust

I reversed phase of woofers only from stereo settings yesterday and no setting was changed for front and rear speakers.

Based on my car i.e Zen and current set up 8016 Kenwood , Infinity Reference Components .I am driving front and rear by GTO 1004 and both woofers by 3501 GTO. Plese suggest what to enter in all paramters of stereo , amp . Appreciate your help .

Keep all tone controls at the HU to flat. Bypass all crossovers at the amp (set them amps to All Pass).

From the HU set LP for 3501 (the subwoofer amp) at 80Hz (if you can control the slope set it at 18db) and
HP (1004 amp) rear at 80hz, and front a little higher maybe 100hz (same slope as above). The reason I prefer to use the HU's crossover is that I can tweak it while I am in the car. You cant do that with the amp's crossover.

I set time alignment by ear. Delay the front speakers till the subwoofer and front speakers outputs arrive together at yor ear.

The rest is all taste. I find I rarely use any EQ or boost just 1 or 2 db.

[DerAlte]

Originally Posted by archat68

... The subwoofer enclosure was home made by me using 16mm MDF board, carpeted. Sealed all joint with Araldite and silicone glue and then screwed. Not anything fancy. Ran out of adhesive and patience while carpeting so used nails as a quick fix .

Now need a grille for the subwoofer to prevent it from accidental damage. Any idea?

Fantastic! Congratulations.

16mm is an odd size for MDF board. Are you sure it is not 18 or 19mm (3/4")?

Araldite? Next time please use a wood glue like Fevicol MR (plain Fevicol). Araldite doesn't penetrate, and doesn't produce a good joint. Fevicol does - it is water based. And the for the carpet, use Fevicol SR (good old Rubber Solution).

Check in the electronics market where they make and sell PA systems. You will get the square perforated black grills. If you don't get for 8", get the next higher size. If you get a 12" one you might have to cut and form to fit.

Originally Posted by ::CMS::

... a decent class AB will outperform a class D for >100Hz in SQ. ... a class AB vs class D will be noticeable.

I don't think common listeners will be able to make out any difference in a car at normal listening levels.

[sparkguy]

Originally Posted by archat68

Thanks to DerAlte for your patient replies!!

Finally got my system up and running.

Congratulations on your setup.

Few questions
1) Details of costing involved in procuring individual items and labour
2) Are front JBL comps installed in doors. I have got spark and no space in doors. Only 4'' speakers in dash itself
3) Is it necessary to change wiring? Which brand
4) Your choice of sub is interesting. Any specific reason for choosing this
5) Lack of interest and time prevents me from doing carpentry. Could you suggest any ready made enclosure

Thanks

[archat68]

Originally Posted by DerAlte

Fantastic! Congratulations.

16mm is an odd size for MDF board. Are you sure it is not 18 or 19mm (3/4")?...

It is 3/4"

Originally Posted by DerAlte

... Araldite? Next time please use a wood glue like Fevicol MR (plain Fevicol). Araldite doesn't penetrate, and doesn't produce a good joint. Fevicol does - it is water based. And the for the carpet, use Fevicol SR (good old Rubber Solution). ...

As I got the panels cut from a shop there were some gaps between them when assembling. I first used saw dust and Fevicol to fill the gaps then applied Araldite from outside and Silicone sealant from inside. I was using rubber solution for carpet but the quantity I bought was insufficient and I was lazy to go to the market again. So just used some small nails which were lying with me.

Originally Posted by DerAlte

... Check in the electronics market where they make and sell PA systems. You will get the square perforated black grills. If you don't get for 8", get the next higher size. If you get a 12" one you might have to cut and form to fit. ...

Thanks!!

Originally Posted by sparkguy

Congratulations on your setup.

Few questions
1) Details of costing involved in procuring individual items and labour...

Amp Rs 5K from ebay, Subwoofer 4.6K from Avenuesound.in, HU JVC 926BT 11.5K locally, wiring, damping, installation 8K approx.

Originally Posted by sparkguy

...2) Are front JBL comps installed in doors. I have got spark and no space in doors. Only 4'' speakers in dash itself ...

Yes on the door. They are 6.5"

Originally Posted by sparkguy

... 3) Is it necessary to change wiring? Which brand ...

If you are feeding the speakers directly from HU I think you may skip wiring change. But wiring change is not very costly affair. Instead of exotic brands get Finolex 16AWG wire from electric shop. They will be much cheaper and better too.

Originally Posted by sparkguy

... 4) Your choice of sub is interesting. Any specific reason for choosing this ...

Only reason is boot space!!

Originally Posted by sparkguy

... 5) Lack of interest and time prevents me from doing carpentry. Could you suggest any ready made enclosure ...

There are no readymade enclosure for 8 inch sub. You can get it done from any carpenter. Just provide them the dimensions.

Thanks.

Thanks everybody! I've provided the answers in bold.

[DerAlte]

Originally Posted by archat68

... I first used saw dust and Fevicol to fill the gaps then applied Araldite from outside and Silicone sealant from inside. ...

Over-engineering!
1. First minimize the gaps by using a wood file / rasp. You can check by holding up the joint to light. Countersink holes before assembling if using CSK head screws. Use self-tapping screws, but pre-drill holes with a bit same size as bottom-of-thread dia - this prevents MDF from splitting

2. Then, assemble the joint by applying Fevicol to one side of the joint, preferably the edge of one board. Drive in and tighten the screws (would be easy since holes are pre-drilled) till Fevicol oozes out of the joint

3. Assemble all the joints and then leave the joints to dry (couple of hours)

4. Now apply Fevicol mixed with sawdust *from the inside* to seal the joints - rub it in with finger. Nothing else required to be applied from inside or outside. (Your Araldite and Silicone sealant application was redundant)

[blackfire_9]

@cms: Yes, there's a reason & it is because a class D amplifier is more efficient than a similar amplifier but with class AB design. My car's current alternator is rated at 120A, out of which various electro-mechanical components mostly need half of that. So give & take, I have around 50-55A to play with.

Now, I already have a mono on my car that pumps out about 400w RMS on a 4ohm load. Add to that my requirement of about 100w RMS per channel multiplied by 4 channels & the total power is close to 800 watts. At about 75-80% efficiency of a class D, this translates to an average current draw anywhere around 40-50A (approx.) & that's my limit. With a class AB, I can never stay in this limit for the kind of power I am aiming for.

Probably the system would still run but would be a big load on my car's electrical system & I don't want that. I can sacrifice that little extra clarity of AB amps in mid-highs to reduce the electrical load.

Originally Posted by ::CMS::

Is there any specific reason that you are looking out only for a class D amp? A Class D amp is efficient than a Class AB, but a decent class AB will outperform a class D for >100Hz in SQ. You wont feel any difference b/n the above amps but a class AB vs class D will be noticeable.

@ALL: Any advice between the two amps? Also is there any way to spot if the Hertz is genuine or not? I ask because though the Hertz is from a reputed dealer/installer, I am getting a deal since the amp comes from a company who is no longer associated with Hertz.

[archat68]

Originally Posted by DerAlte

Over-engineering!
1. First minimize the gaps by using a wood file / rasp.

Actually I didn't had any. The gaps were not small 1-2mm. SO filled then with saw dust and fevicol. Applied Araldite thinking it would hold the joint better. Later got hold of Silicone sealant and I thought why use it too . I also used te silicone glue to seal the sides of the speakon connector with the cabinet after it has been screwed to the cabinet.

Now shall I need to put some polyfil inside the cabinet or some bitumen sheets?

[DerAlte]

Originally Posted by blackfire_9

... though the Hertz is from a reputed dealer/installer, I am getting a deal since the amp comes from a company who is no longer associated with Hertz.

That's a bit cryptic. I would go for the Kappa Four purely on the basis of better service support in India from Harman. The low price of the possibly genuine Hertz could be just 'cut-your-losses' price.

Originally Posted by archat68

... Now shall I need to put some polyfil inside the cabinet or some bitumen sheets?

Polyfill will do. About 200g in a cloth bag. Just to break up any standing waves.

[::CMS::]

Originally Posted by archat68

shall I need to put some polyfil inside the cabinet

It depends on the dimensions of your enclosure. If your sub is made exactly as per the manufacturer recommendation, it doesnt need any polyfill. Polyfill can slowdown the waves making it look like a larger box thereby changing the net box volume, density and quantity are the variables. This need to be calculated properly using any simulator apps like unibox / winisd, unless it can have a -ve effect. In other words, if you have made the box smaller than the recommended size, you can add polyfill.

Bitumen sheets on the walls of the sub is a diy option for increasing the resonance frequency of the box, thereby it avoids / reduce the resonance inside the box. Another common way to stiffen the walls is to have enough braces (need to simulate the box dimensions based on the brace volume to get the recommeded volume)

[archat68]

Originally Posted by ::CMS::

It depends on the dimensions of your enclosure. If your sub is made exactly as per the manufacturer recommendation, it doesnt need any polyfill. Polyfill can slowdown the waves making it look like a larger box thereby changing the net box volume, density and quantity are the variables. This need to be calculated properly using any simulator apps like unibox / winisd, unless it can have a -ve effect. In other words, if you have made the box smaller than the recommended size, you can add polyfill.

Bitumen sheets on the walls of the sub is a diy option for increasing the resonance frequency of the box, thereby it avoids / reduce the resonance inside the box. Another common way to stiffen the walls is to have enough braces (need to simulate the box dimensions based on the brace volume to get the recommeded volume)

The manufacturer recommended volumeis 0.23 - 0.3 cft. The one that I made is slightly larger than 0.3cft (0.32cft).

[::CMS::]

Originally Posted by archat68

The manufacturer recommended volumeis 0.23 - 0.3 cft. The one that I made is slightly larger than 0.3cft (0.32cft).

Then, no need of any polyfill. Also, considering the box size you dont need bracing. But I would suggest plotting it once, if possible, using unibox\winisd and see the chart to get the required volume (hope the speaker's T/S params are same as the published params). Also try to reduce the volume to the required size and play it for a while and see if there is any difference.

[blackfire_9]

That's exactly what it is, a "cut-your-losses" price. You are correct that since Infinity is still associated with Sahil International, chances of getting warranty support are better. The discount on MRP (in case of Hertz) is basically 40%-42%, would you consider this a good deal purely from a discount proportion perspective, if its a distress sale?

Secondly, purely from product perspective, do you have any experience or information on these two amplifiers? I would basically like to know if there is any significant difference to the way these amplifiers can sound & if there is a difference in the build quality (w.r.t durability or ability to handle abuse). Any tips here?

Also, would you by any chance know of the authorized distributor for Hertz products in India?

Drive safe.

Originally Posted by DerAlte

That's a bit cryptic. I would go for the Kappa Four purely on the basis of better service support in India from Harman. The low price of the possibly genuine Hertz could be just 'cut-your-losses' price.

[navin]

Originally Posted by ::CMS::

It depends on the dimensions of your enclosure. If your sub is made exactly as per the manufacturer recommendation, it doesnt need any polyfill. Polyfill can slowdown the waves making it look like a larger box thereby changing the net box volume, density and quantity are the variables.

While adding polyfil (or fiberglass, long hair wool, open cell foam or simialr damping materials) can increase the virtual volume of the box damping materials do much more than that. Damoing helps reduce standing waves by dissipating the reflected "sound-energy" within the box. Granted the efficacy of damping is limited from material to material with long hair wool being the best followed by fiberglass. The former is rarely used becuase it is expensive and the later itches like crazy when handled.

Damping also helps damp impedance peaks. So if the woofer-box combo had a 30 ohm peak at Fb damping might reduce it by half. The amp then sees a much more resistive load and hence is more efficient and can more easily control the woofer.

Over damoping a system can rob it of it's dynamics. The best way to damp is to use impendace sweeps and see when the impedace peak stops falling but if you do not have the equipment about 200-400gms per cu. ft. is a good guide.

[::CMS::]

Originally Posted by navin

Damoing helps reduce standing waves by dissipating the reflected "sound-energy" within the box.

Damping also helps damp impedance peaks. So if the woofer-box combo had a 30 ohm peak at Fb damping might reduce it by half.

But all these are not applicable for the frequencies produced by a subwoofer which have wavelengths more than a car.